H'ORT PAPERS IN— ilalytical techniques \7 ,onomic geology ‘Igineering geology eochemical exploration re deposits Eleontology Ftrology {ality of water ,dimentation Iatigraphy uctural geology [eoretical hydrology pographic mapping I E Pé MSG/’5 GEOLOGICAL SURVEY RESEARCH I964 Chapter C QZ-WQ é’:’= ”‘5’ /., biz/c: Ag” 0% «”75 flé» k firm/=5 ‘0 EARTH SCIENCES L'BRARY GEOLOGICAL SURVEY PROFESSIONAL PAPER 5OI—C GEOLOGICAL SURVEY RESEARCH I 964 Chapter C GEOLOGICAL SURVEY PROFESSIONAL PAPER 5OI—C Scientific notes and summaries of investigations prepared by members oft/1e Geologic and Water Resources Divisions in the fields of geology, hydrology, and related sciences UNITED, STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: I964 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. NoIan, Director am“ 902“” um»! For sale by the Superintendent of Documents, US. Government Printing Office, Washington, D. C., 20402 @2575 P9 V. 50/.’C”D EARTH SCIENCES LIBRARY FOREWORD This collection of 46 short papers is the second of a series to be released as chapters of Geological Survey Research 1964. The papers report on scientific and economic results of current work by members of the Geologic, Conservation, Water Resources, and Topographic Divisions of the US. Geological Survey. Some of the papers present results of completed parts of continuing investigations; others announce new discoveries or preliminary results of investigations that will be discussed in greater detail in reports to be published in the future. Still others are scientific notes of limited scope, and short papers on techniques and instrumentation. Chapter A of this series will be published later in the year, and will present a summary of results of work done during the present fiscal year. flaw/QM“ THOMAS B. NOLAN, Director. III 294 CONTENTS Page Foreword ______________________________________________________________________________________ m GEOLOGIC STUDIES Structural geology " \ Late Mesozoic orogenies in the ultramafic belts of northwestern California and southwestern Oregon, by W. P. Irwin_-__ C1 Westward tectonic overriding during Mesozoic time in north—central Nevada, by R. E. Wallace and N. J. Silberling ______ 10 Strike—slip faulting and broken basin-ranges in east-central Idaho and adjacent Montana, by E. T. Ruppel ____________ 14 Evidence for a concealed tear fault with large displacement in the central East Tintic Mountains, Utah, by H. T. Morris and W. M. Shepard _______________________________________________________________________________________ 19 Shape and structure of a gabbro body near Lebanon, Conn., by M. F. Kane and G. L. Snyder ________________________ 22 Outline of the stratigraphic and tectonic features of northeastern Maine, by Louis Pavlides, Ely Mencher, R. S. Naylor, and A. J. Boucot __________________________________________________________________________________________ 28 Stravligraphy and paleontology Stratigraphic importance of corals in the Redwall Limestone, northern Arizona, by W. J. Sando ____________________ 39 Younger Precambrian formations and the Bolsa(?) Quartzite of Cambrian age, Papago Indian Reservation, Ariz., by L. A. Heindl and N. E. McClymonds _______________________________________________________________________ 43 Occurrence and paleogeographic significance of the Maywood Formation of Late Devonian age in the Gallatin Range, southwestern Montana, by C. A. Sandberg and W. J. McMannis _______________________________________________ 50 Petrography of the basement gneiss beneath the Coastal Plain sequence, Island Beach State Park, N.J., by D. L. Southwick _______________________________________________________________________________________________ 55 Offshore extension of the upper Eocene to Recent stratigraphic sequence in southeastern Georgia, by M. J. McCollum and S. M. Herrick ________________________________________________________________________________________ 61 Upper Eocene smaller Foraminifera from Shell Bluff and Griffin Landings, Burke County, Ga., by S. M. Herrick ________ 64 Mineralogy and petrology Post-Paleocene West Elk laccolithic cluster, west-central Colorado, by L. H. Godwin and D. L. Gaskill ________________ 66 Chemistry of greenstone of the Catoctin Formation in the Blue Ridge of central Virginia, by J. C. Reed, Jr ____________ 69 Occurrence and origin of laumontite in Cretaceous sedimentary rocks in western Alaska, by J. M. Hoare, W. H. Condon, and W. W. Patton, Jr ____________________________________________________________________________________ 74 Clay minerals from an area of land subsidence in the Houston—Galveston Bay area, Texas, by J. B. Corliss and R. H. Meade ___________________________________________________________________________________________________ 79 Attapulgite from Carlsbad Caverns, N. Mex., by W. E. Davies __________________________________________________ 82 Diagram for determining mineral composition in the system MnCOrCaCoa—MgCog, by W. C. Prinz ________________ 84 Geochemistry Lithium associated with beryllium in rhyolitic tuff at Spor Mountain, western Juab County, Utah, by D. R. Shawe, Wayne Mountjoy, and Walter Duke ________________________________________________________________________ 86 A geochemical investigation of the High Rock quadrangle, North Carolina, by A. A. Stromquist, A. M. White, and J. B. McHugh ___________________________________________________________________________________________ 88 Evaluation of weathering in the Chattanooga Shale by Fischer assay, by Andrew Brown and I. A. Breger _______________ 92 Measurement of relative cationic diffusion and exchange rates of montmorillonite, by T. E. Brown __________________ 96 Geophysics Preliminary structural analysis of explosion-produced fractures, HARDHAT event, Area 15, Nevada Test Site, by F. N. Houser and W. L. Emerick ________________________________________________________________________________ 100 Seismicity of the lower east rift zone of Kilauea Volcano, Hawaii, January 1962—March 1963, by R. Y. Koyanagi ________ 103 Economic geology Paleolatitudinal and paleogeographic distribution of phosphorite, by R. P. Sheldon ________________________________ 106 Reconnaissance of zeolite deposits in tuffaceous rocks of the western Mojave Desert and vicinity, California, by R. A. Sheppard and A. J. Gude, 3d _______________________________________________________________________________ 114 Ore controls at the Kathleen-Margaret (MacLaren River) copper deposit, Alaska, by E. M. MacKevett, Jr ........... 117 V VI CONTENTS Geomorphology and Pleistocene geology Page Cavities, or “tafoni”, in rock faces of the Atacama Desert, Chile, by Kenneth Segerstrom and Hugo Henriquez ________ 0121 Negaunee moraine and the capture of the Yellow Dog River, Marquette County, Mich., by Kenneth Segerstrom ______ 126 Ancient lake in western Kentucky and southern Illinois, by W. I. Finch, W. W. Olive, and E. W. Wolfe ______________ 130 Outline of Pleistocene geology of Martha’s Vineyard, Mass, by C. A. Kaye _______________________________________ 134 Illinoian and Early Wisconsin moraines of Martha’s Vineyard, Mass, by C. A. Kaye ______________________________ 140 Glacial geology of the Mountain Iron-Virginia-Eveleth area, Mesabi iron range, Minnesota, by R. D. Cotter, and J. E. Rogers _____________________________________________________________________________________________ 144 Glaciology Recent retreat of the Teton Glacier, Grand Teton National Park, Wyo., by J. C. Reed, Jr __________________________ 147 Analytical techniques A simple oxygen sheath for flame photometry, by Irving May, J. I. Dinnin, and Fred Rosenbaum ___________________ 152 Determination of iodine in vegetation, by Margaret Cuthbert and F. N. Ward ____________________________________ 154 Judging the analytical ability of rock analysts by chi-squared, by F. J . Flanagan ___________________________________ 157 Ultrasonic dispersion of samples of sedimentary deposits, by R. P. Moston and A. I. Johnson _______________________ 159 HYDROLOGIC STUDIES Ground water Tritium content as an indicator of age and movement of ground water in the Roswell basin, New Mexico, by H. O. Reeder- 161 Relation of surface-water hydrology to the principal artesian aquifer in Florida and southeastern Georgia, by V. T. Stringfield _______________________________________________________________________________________________ 164 Quality of water Contamination of ground water by detergents in a suburban environment—South Farmingdale area, Long Island, N.Y., by N. M. Perlmutter, Maxim Lieber, and H. L. Frauenthal ___________________________________________________ 170 Relation of chemical quality of water to recharge to the Jordan Sandstone in the Minneapolis-St. Paul area, Minnesota, by M. L. Maderak _______________________________________________________________________________________ 176 Engineering hydrology Geohydrology of storage of radioactive waste in crystalline rocks at the AEC Savannah River Plant, S.C., by G. E. Siple- 180 Theoretical hydrology Stream discharge regressions using precipitation, by H. C. Riggs _________________________________________________ 185 Relation of annual runofi to meteorological factors, by M. W. Busby _____________________________________________ 188 TOPOGRAPHIC MAPPING Photogrammetry Photogrammetric countouring of areas covered by evergreen forests, by James Halliday ............................ 190 INDEXES Subiect _________________________________________________________ .. ............................... , ............. 195 Author ....................................................................................................... 197 GEOLOGICAL SURVEY RESEARCH I964 LATE MESOZOIC OROGENIES IN THE ULTRAMAFIC BELTS OF NORTHWESTERN CALIFORNIA AND SOUTHWESTERN OREGON By WILLIAM P. IRWIN, Menlo Park, Calif. Work done in cooperation with the California Division of Mines and Geology Abstract—The structural style of the pre-Tertiary rocks of northern California and southern Oregon is one of regional thrust faults along which great sheets of ultramafic rocks are emplaced. Ultramafic rocks form a belt along the Klamath Mountains and Sierra Nevada in which they intruded during the Late Jurassic Nevadan orogeny. To the west they form a second belt in which they intruded rocks of the Coast Ranges, probably during the Late Cretaceous. In the Coast Ranges these pre-Tertiary structures have been dislocated and obscured by faults of the San Andreas system. The belt of ultramafic rocks along the Pacific coast of North America trends through the Klamath Moun- tains and Coast Ranges of northern California and southern Oregon. Here the ultramafic rocks intruded Mesozoic and Paleozoic strata as great subhorizontal sheets during two orogenies in the late Mesozoic. The earliest of these orogenies, the Nevadan, is Late Jurassic in age. It is of primary importance in the Klamath Mountains and in the nearby Sierra Nevada from which the name was derived. The second of these orogenies, probably Late Cretaceous in age, is of greatest im- portance in development of the pre-Tertiary structure 'of the Coast Ranges, and thus will be referred to as the Coast Rangeorogeny. The Coast Range orogeny also influenced the structure of the Klamath Mountains but to a much lesser degree than did the Nevadan. This article presents an hypothesis regarding the overall structural framework of the late Mesozoic and older rocks of the Klamath Mountains and Coast Ranges. Some parts of the area have been studied in detail, but most are known only in reconnaissance. Thus, many of the relations inferred are highly spec- ulative, but it is hoped that the hypothesis will prove U.S. GEOL. SURVEY PROF of use in suggesting areas Where critical relations might be examined. The general concept to be developed is one of west- ward overriding'of great, low-angle thrust plates during the late Mesozoic orogenies, and will rely considerably on the belief that the ultramafic rocks were em- placed primarily as sheets between the thrust plates. This differs from the tectonic style commonly accorded the Pacific coastal terrane, a style dominated by strike- slip movements along high-angle faults such as the San Andreas. The intent is not to minimize the signifi- cance of the strike-slip faults, but to point out that low- angle thrust faults may have a role of equal, if not greater, importance in the orogenic history of the Pa- cific borderland. The rocks involved in the Nevadan orogeny are dis- tinguished from later rocks by use of the term “sub: jacent.” Subjacent refers to the Paleozoic and Meso- zoic rocks involved in the Nevadan orogeny, including the ultramafic and granitic rocks that intruded during that orogeny. The term “superjacent” refers to the late Mesozoic and younger rocks that, in the Klamath Mountains, were deposited unconformably on the sub- jacent rocks. This article is not greatly concerned with superjacent rocks younger than Late Cretaceous in age, except that they conceal the lateral extensions of the older rocks and thus limit observation. The subjacent rocks predominate in the Klamath Mountains and Sierra Nevada, whereas the superjacent are the prin- cipal rocks of the Coast Ranges and Great Valley. SUBJACENT (NEVADAN AND OLDER) ROCKS The subjacent rocks are eugeosynclinal, as they in- clude greenstones, graywacke sandstones, mudstones, . PAPER 501-0, PAGES C1-C9 Cl C2 STRUCTURAL GEOLOGY EXPLANATION SUPERJACENT ROCKS U Rocks of Cenozoic age U Rocks of Late Jurassic (Tithonian) to Late Cretaceous age SUBJACENT ROCKS Will Western Jurassic belt ill Western Paleozoic and Triassic e t 0" ._. 4 Central metamorphic belt Granitic rocks Ultramafic rocks, in both subjacent and superjacent terranes Includes some gabb'roic rocks 10 O 10 20 30M|LES L4_.|_I_I_l__;l_l Geology compiled and modified trorn Strand (1962 and 1964), Wells and Peck (1961), and Irwin (1960) FIGURE 1.—-Geologic map of northwestern California and southwestern Oregon. IRWIN C3 thin-bedded chert, and minor limestone. In the Kla- math Mountains they occur in several broadly arcu- ate belts (fig. 1), which from east to west are the east- ern Paleozoic, central metamorphic, western Paleozoic and Triassic, and western Jurassic belts (Irwin, 1960). At a few places in all the belts, except the eastern Paleo- zoic, patches of rocks of adjacent belts are found. Each belt seems to constitute a separate bundle of rocks, as no depositional contacts have been found between the separate bundles, and as the contacts between the belts, or the separate bundles, seem to be either faults or the loci for emplacement of ultramafic or granitic rocks. All the bundles have been intruded by ultramafic and granitic rocks. The eastern Paleozoic belt is a thick, fairly complete, stratigraphic section that ranges in age from Ordo- vician( ?) upward through the Paleozoic (fig. 2), and WEST EAST Pit Formation Bully Hill Rhyolite Dekkas Andesite Nosoni‘Formation / Triassic / Permian Mississippian McCIoud Limestone Baird Formation Bragdon Formation Hosselkus Limestone Balaklala Rhyolite Kennett Formation Copley Greenstone Gazelle Formation Rocks of western Paleozoic and Triassic belt Duzel Formation Ultramafic rocks Rocks of central metamorphic belt FIGURE 2.—Schematic section across the eastern part of the Klamath Mountains, Calif. Light tone, rocks of eastern Paleozoic belt ; dark tone, ultrabasic rocks. to the east continues on through Triassic into the Mid- dle Jurassic. The strata of Ordovician( ?) and Silu- rian age are known only in the northern part of the belt, Where they predominate, whereas Devonian, Mis- sissippian, and Permian strata occupy the remainder. The section is structurally complex in detail, but in general dips to the east. Rhyolitic strata occur at sev- eral places in the stratigraphic section, but none are known in the belts to the west. The central metamorphic belt is separated from the eastern Paleozoic belt by ultramafic rocks. The rocks of the central metamorphic belt are chiefly the Salmon Hornblende Schist and Abrams Mica Schist of Hershey (1901). However, some of the rocks originally de- scribed by Hershey as part of the Abrams Mica Schist are now excluded from the centralimetamorphic belt. These are the Stuart Fork Formation of Davis and Lipman (1962). They are exposed in Windows in the central metamorphic belt, and are considered correla- tive with rocks of the western Paleozoic and Triassic belt (Davis and Lipman, 1962). The age of the rocks of the central metamorphic belt is not known, except that (1) the rocks are older than ultramafic and gra- nitic rocks emplaced during the Nevadan orogeny; and (2) a K40—Ar40 age of 190 million years, obtained from hornblende of the Salmon Hornblende Schist by M. A. Lanphere (Irwin, 1963), indicates that the metamor- phism was earlier than the Nevadan orogeny. The western Paleozoic and Triassic belt lies west of the central metamorphic belt. It is structurally com- plex and seems to consist chiefly of Permian and Trias- sic rocks, although at one locality, fossils suggesting a Silurian and Devonian age were found (Merriam, 1961). The western Jurassic belt is chiefly slaty mudstones and graywackes of the Galice Formation, which is as young as middle Kimmeridgian in age, and which is an equivalent of the Mariposa Formation of the Sierra Nevada. Along the western boundary of the Klamath Mountains it includes the schist of South Fork Moun- tain. In both California and Oregon, a few patches of rocks of the western Jurassic belt occur in the Coast Ranges west of the Klamath Mountains boundary.1 Those in California are schist like that of South Fork Mountain; in Oregon they include the Galice Forma- tion and Colebrooke Schist, a correlative of the schist of South Fork Mountain. SUPERJACENT (POST-NEVADAN) ROCKS The superjacent, post-Nevadan, rocks are the princi- pal rocks of the Coast Ranges and Great Valley, and in- clude the uppermost Jurassic (Tithonian) and Cre- taceous. They occur along the southern, western, and northern perimeter of the Klamath Mountains, and also as a few small patches within the Klamath Mountains (fig. 1). The superjacent deposits are separated into two fundamentally different kinds: eugeosynclinal de- posits, and noneugeosynclinal deposits. These two kinds of deposits were laid down penecontemporane- ously during the Late Jurassic and Cretaceous and are equivalents, or facies, of one another (Irwin, 1957). The eugeosynclinal superjacent deposits include the Franciscan Formation in California, and the Dothan Formation2 and the Franciscan-like part of Diller’s 1 The western boundary of the Klamath Mountains shown on figure 1 more precisely separates the Klamath Mountains and Coast Ranges on the basis of subjacent and superjacent terranes, and structure, than does the boundary as drawn by Diller (1902), who included in the Klamath Mountains all the Dre-Tertiary rocks of southwestern Oregon. 3 The Dothan Formation usually has been regarded as part of the sub- jacent terrane, rather than superjacent as herein considered. Inclu- sion of the Dothan with the superjacent formations in no way violates any factual data. C4 (1898) Myrtle Formation in Oregon. For the most part they are thick assemblages of graywacke, mud- stone, pillow lavas, and radiolarian chert. Lentils of distinctive Foraminifera-bearing limestones, the Calera (Lawson, 1914) in California, and the Whitsett (Diller, 1898) in Oregon, are found in the mid—Cretaceous parts of the deposits. The eugeosynclinal terrane is struc- turally complex and very sparsely fossiliferous, and exotic small blocks of glaucophane schist and ultramafic rock are fairly common features. The eugeosynclinal deposits probably were laid down along the western border of the continental mass, perhaps on the oceanic crust in an offshore environment. No evidence has been found to indicate that these eugeosynclinal rocks were deposited anywhere on the subjacent (continental) rocks. The noneugeosynclinal superjacent deposits of latest Jurassic and Cretaceous age include the Great Valley sequence (or Sacramento Valley sequence of Irwin, 1957) in California, and the Myrtle Group (Imlay and others, 1959) in Oregon. These deposits were laid down predominantly, if not wholly, on subjacent rocks that formed the continental shelf and slope, and for brevity will hereafter be referred to as shelffldeposits, in contrast to the eugeosynclinal deposits. The shelf deposits consist of interlayered beds of graywacke, mud- stone, and conglomerate. These rocks more commonly show bedding features such as grading, crossbedding, and sole markings, are more fossiliferous, and generally are less folded and faulted than are the equivalent eu- geosynclinal rocks. Other relative differences such as greater K—feldspar content (Bailey and Irwin, 1959) and lower specific gravity (Irwin, 1961) also have been noted. In California the Lower Cretaceous shelf deposits lap on the subjacent rocks of the Klamath Mountains, in- cluding the Shasta Bally batholith (Km—AI"0 age 134 m.y., Curtis and others, 1958). The Upper Jurassic is conformable beneath the Lower Cretaceous along the west side of the Great Valley about 15 miles and more south of Shasta Bally batholith; thus the Upper Jurassic (Knoxville Formation of Tithonian age) also must postdate the intrusion and stripping of the Shasta Bally batholith. At the north end of the Klamath Mountains in Oregon the Upper Jurassic (Riddle For- mation of Tithonian age) and Lower Cretaceous (Days Creek Formation), similar to correlative rocks of the Great Valley sequence of California, also lie uncon- formably on the subjacent rocks. Scattered patches of Lower Cretaceous and Upper Cretaceous shelf deposits lie on the subjacent rocks elsewhere in the Klamath Mountains, and it is clear that these shelf deposits once covered much of the Klamath Mountains. The rela— STRUCTURAL GEOLOGY tions between the superjacent shelf deposits and sub- jacent rocks are shown diagrammatically on figure 3. On the left side of the same figure the eugeosynclinal equivalents of the superjacent shelf deposits are shown in thrust-fault contact with the subjacent rocks of the Klamath Mountains province. ULTRAMAFIC ROCKS The ultramafic rocks are an important key in outlin- ing the structural framework of northern California and southern Oregon. They are chiefly peridotite that gen- erally is somewhat serpentinized and at many places highly sheared. Some gabbroic rocks occur with the ultramafic rocks, and although of questionable genetic relation, they are included with the ultramafic rocks shown on figures 1 and 4 for cartographic convenience. The ultramafic rocks in the Klamath Mountains intrude subjacent strata as young as Late Jurassic (Kimmerid- gian) and are in turn intruded by granite. Thus the ultramafic rocks of the Klamath Mountains belong to the subjacent block, and along with the granitic and other subjacent rocks, are overlain unconformably by the superjacent shelf deposits. In the Coast Ranges the ultramafic rocks intrude superjacent strata as young as early Late Cretaceous (Cenomanian) in age. Thus the ultramafic rocks occur in two belts. Those involved in the Nevadan orogeny lie to the east, and are referred to the Klamath ultramafic belt. Those that intrude Mesozoic superjacent strata lie to the west and are re— ferred to the Coast Range ultramafic belt. The general trend of the Klamath ultramafic belt is arcuate (fig. 4), parallel to the pattern of the lithic belts of subjacent rocks of the Klamath Mountains. At the south end of the Klamath Mountains the belt presum- ably extends to the southeast beneath superjacent strata KLAMATH COAST RANGES MOUNTAINS 1v " GREAT VALLEY :.l.lpper'Jurassic_:; '?,:"to lower Upper1°a _ . Cretaceous . ’.°.'o'.'.'.o" -' Jurassic and older EXPLANATION Eugeosynclinal Shelf and slope deposits deposits Cl SUBJACENT SUPERJACENT ROCKS ROCKS FIGURE 3.—Schematic relations. between superjacent and subjacent rocks. IRWIN C5 122L00' IZOLOO’ EXPLANATION Cenozoic rocks SUPERJACENT SUPERJACENT EUGEOSYNCLINAL SHELF AND SLOPE DEPOSITS DEPOSITS Gold Beach Upper Jurassic to lower Upper Cretaceous Upper Cretaceous -42 ° 00’ Uppermost Jurassic and Lower Cretaceous Crescent City Ultramafic rocks Includes some gabbroic rocks Subjacent rocks ® 2 Dry Creek section V: Ex) Eureka Ward Creek sectlon O . O l I -40 ° 00' ‘ I L) I N 5' < E E I Q ‘N O ' <1 In > O 3 ca 4 Z V O: Q, I L ?n \ 4 x 7 \ O \ 7 \ \ \ O l l I l - 38 ° 00' Geology compiled and modified from Strand (1962 and 1964), Wells and Peck (1961), Irwin (1960), Jenkms(1938). and Bailey and others (1964) I \ . San Francisco'n. FIGURE 4.—Distribution of ultramafic rocks and two‘ facies of superjacent rocks in northwestern California and south- western Oregon. C6 of the Great Valley, and continues southward along the foothills of the western Sierra Nevada. In the eastern Klamath Mountains the ultramafic rocks are regarded as parts of a once-continuous, subhorizontal sheet that separated the rocks of the central metamorphic belt from structurally overlying rocks of the eastern Paleo- zoic belt (Irwin and Lipman, 1962). The present ar- cuate outcrop of the ultramafic rocks between the two belts is the eroded lip of the sheet whose roots lie buried beneath the Paleozoic strata to the east. The large area of ultramafic rock that generally separates the Or- dovician( ?) and Silurian from the younger strata in the eastern Paleozoic belt (fig. 1) is interpreted as a broad arch in the sheet from which the once-overlying Paleozoic strata are largely eroded. In one sense, the area of Ordovician( ?) and Silurian strata may even be considered a large outlier, unless it connects with the main body of eastern Paleozoic strata beneath super- j acent strata to the northeast. In the southern part of the Klamath Mountains an outlier of Mississippian strata of the eastern Paleozoic belt rests on, but is gen- erally separated from, rocks of the central metamorphic belt by a thin layer of ultramafic rock (Irwin, 1963). As shown schematically on figure 2, the ultramafic sheet is discordant with the stratigraphic section of the eastern Paleozoic belt. This discordance, in addition to the structural break seemingly required for intrusion of a low-angle sheet of such great magnitude, suggests that the ultramafic sheet intruded along a thrust fault of considerable horizontal translation. West of the central metamorphic belt, the ultramafic rocks do not as clearly occur as widespread sheets. At many places they are concentrated along boundaries between lithic belts, and within lithic belts as alined, though discontinuous, bodies. Detailed mapping prob- ably will establish an areal sheetlike continuity for many of these now seemingly unrelated bodies. However, at present it is not known whether the ultramafic rocks west of the central metamorphic belt should be consid- ered dislocated portions of several large individual sheets, or whether one might take an extreme view that all the ultramafic rocks of the Klamath Mountains were originally parts of one great sheet that transgressed successively younger strata from the eastern Paleozoic belt to the western Jurassic belt. The pattern of distribution of ultramafic rocks in the Coast Range belt differs from that of the Klamath belt (fig. 4). Here the arcuate pattern that reflects the struc- ture of the subj acent terrane of the Klamath Mountains is not present. The principal ultramafic body of the Coast Range belt trends north-south along the west side of the Great Valley. At the south end of this large body, approximately at the latitude of Sacramento, the STRUCTURAL GEOLOGY concentration of ultramafic rock extends to the west as a series of individual, northwesterly oriented bodies. These are thought to be faulted segments of the north- south-trending body. Here, as elsewhere, most of the ultramafic rock of the Coast Ranges occurs along or near contacts between the two facies of superjacent rocks. STRUCTURAL RELATION OF FACIES OF SUPERJACENT ROCKS The distribution of the two facies of Late Jurassic (Tithonian) and Cretaceous superj acent rocks is shown on figure 4. The eugeosynclinal (Franciscan) facies is confined to the Coast Ranges and is the dominant rock there. Along the west side of the Great Valley the eu— geosynclinal facies on the west is separated from the shelf facies (Great Valley sequence) on the east by the major body of ultramafic rock of the Coast Ranges. At the south end of the body, the area of shelf facies swings to the west across the grain of the Coast Ranges, follow- ing the concentration of ultramafic rocks. Here the structure seems to have been a broad arch, plunging gently south, in which the rocks of the Great Valley sequence mantled the Franciscan, but which were sep- arated from the Franciscan by an ultramafic sheet. The crest and west limb of the arch have been broken, and its continuity obscured, by numerous steep north- west—trending faults of the San Andreas system, giving a northwest—trending pattern that is typical of the Coast Ranges. Near the San Andreas fault, in the western part of the Coast Ranges at this latitude, patches of rocks of the Great Valley sequence are now outliers completely isolated within large areas of Franciscan rocks, and here, too, the ultramafic rocks are concen- trated along the boundaries between the two facies. Two of these outliers of the Great Valley sequence are known (Bailey and others, 1964) as the Ward Creek and Dry Creek sections (fig. 4). The arch trends along the east side of the Coast Ranges for almost the length of the Great Valley, and is the major structure of the central Coast Ranges east of the San Andreas fault (Bailey and others, 1964). Along the arch are the great piercement structures, such as at Mount Diablo, east of San Francisco, and the Diablo Range. In these piercements the underlying Franciscan rocks have broken through the mantle of Great Valley sequence and younger rocks, and have carried with them some of the intermediate layer of ultramafic rock. The structural relations between the two facies of late Mesozoic superjacent strata are shown incross sec- tion (fig. 5). In the Coast Ranges, along the line of section, the shelf deposits extend from the Great Valley IRWIN CONTINENTAL DEEP ' . . i SIERRA OCEANTSLgEELéND-T‘ COAST RANGES ..,.— GREAT VALLEY TI‘NEVADA i ".3 a I a E E 2,, <3: ‘5 c . g I ' ‘0— 0.2 “3.9 I an I : c =1 H L... I | : (,9 'oo 0 o 1 a; I : c 53 >3 : z : r m g 5 : = I I V) I m : SEA LEVEL i f f A i I I EXPLANATION EUGEOSYNCLINAL DEPOSITS Upper Jurassic to lower SHELF AND SLOPE DEPOSITS U pper Cretaceous Upper Cretaceous V SUPESJCA‘CSENT s\\\\\\ Upper Jurassic and Lower Cretaceous :3 —<1 u . . . A A V \ UItramafic rocks of thrust sheet and mantle ' Basaltic layer Subjacent rocks 0 40 MILES L_l__l.__L.__l HomzomAL MD VERTICAL SCALE FIGURE 5,—Schematic section showing structural relations be- tween two facies of superjacent rocks. westward over equivalent eugeosynclinal strata of the Coast Ranges, but are separated by an ultramafic sheet. Note particularly the outlying Ward Creek and Dry Creek sections of shelf deposits, which are mildly de- formed in contrast to their surrounding eugeosynclinal equivalents. This juxtaposition of facies seems to de- mand great relatively westward transport of shelf rocks over eugeosynclinal rocks. As the bulk of the ultra- mafic rock of the Coast Ranges occurs along boundaries between these juxtaposed facies, most if not all the ultra- mafic rock may be dislocated parts of a single sheet emplaced along a subhorizontal fault between the two facies. The root zone of the ultramafic sheet lies to the east, presumably connecting with the mantle, and may account for the large positive magnetic anomaly that trends the length of the Great Valley (Irwin and Bath, 1962). As shown on figure 5, the amount of horizontal transport, or relative westward riding of the shelf de— posits, is 50 miles or more. The thrusting and intrusion probably were part of the same orogeny that formed the thrust fault along the western boundary of the Klamath Mountains. THR‘UST-PLATE RELATIONS» The inferred structural relations of the pre-Tertiary strata of the Klamath Mountains and Coast Ranges are C7 summarized schematically on figure 6. The several lithic belts of the Klamath Mountains are considered thrust plates that successively overlap adjacent plates to the west. Isolated patches of rocks correlative with a specific belt are interpreted to be thrust outliers or windows of the plate to which the correlative rocks have been assigned. For illustrative convenience, the gra- nitic and ultramafic rocks are not outlined, and are in- cluded arbitrarily with individual thrust plates. Al- though ultramafic rock intruded between certain of the thrust plates, its inclusion with individual plates does not in most cases seriously distort the outlines of the thrust plates shown on figure 6. An exception is the outline of the eastern Paleozoic plate. Here, the ero- sional lip and exposed crest of the broad arch in the ultramafic sheet are included with the eastern Paleo- zoic plate. Thus the eastern Paleozoic plate as shown on figure 6 is not only the distribution of the rocks of the eastern Paleozoic belt, but includes a reconstruction of the strata of the eastern Paleozoic belt that formerly bridged the broad arch of ultramafic rocks. Because of this, the position of the Gray Rocks outlier, which forms part of this bridge, is shown only by a symbol. The central metamorphic plate lies below the eastern Paleozoic plate and above the western Paleozoic and Triassic plate. The Oregon Mountains outlier of the eastern Paleozoic plate rests on the central metamorphic plate, and, as suggested by Davis and Lipman (1962), windows at several places along the central metamor— phic plate expose portions of the underlying western Paleozoic and Triassic plate. Along its western bor- der the western Paleozoic and Triassic plate lies on the western Jurassic plate, with the Willow Creek, Pros- pect Hill, and Flint Valley outliers of the western Paleozoic and Triassic plate presumably resting on the western Jurassic plate. Near the boundary between California and Oregon, an area of rocks similar to those of the central metamorphic belt is exposed, pre- sumably in a window, nearly surrounded by abundant ultramafic bodies in the western Paleozoic and Triassic belt. These thrust plates are depositionally overlapped at the south end of the Klamath Mountains by the super- jacent shelf deposits, and thus are older than Late Jurassic (Tithonian) in age. Whether all these thrust plates were developed during a single brief orogenic episode is not clear. However, if all the relevant ultra- mafic rocks were emplaced during a single brief span of time in the Late Jurassic, between the middle Kim- meridgian and Tithonian Stages, a similar age span seems likely for the major thrusting. The thrusting, the emplacement of the Klamath ultramafic sheets, and the intrusion of granitic batholiths are tentatively CS 10 0 10 2O 3O STRUCTURAL GEOLOGY EXPLANATION Cenozoic rocks Upper Cretaceous shelf deposits Uppermost Jurassic and Lower Cretaceous shelf deposits. Not shown on outlier of western Ju- rassic plate in Oregon Eastern Paleozoic plate \Q\ \\\\ / / \ \ \ / Central metamorphic plate Hill Western Paleozoic and Triassic plate Western Jurassic plate D Uppermost Jurassic and Cretaceous plate 8 Contact l Thrust fault Sawteeth an upper plate 40 MILES FIGURE 6.—Principal postulated thrust plates of the Klamath Mountains and adjacent Coast Ranges. Thrust outliers are indicated by letter symbol: A, Oregon Mountain; B, Willow Creek; 0, Prospect Hill; D, Flint Valley; E, Redwood Mountain; F, Patricks Point; and G, southwestern Oregon. considered closely timed sequential events of the Nevadan orogeny. The western Jurassic plate is thrust westward over eugeosynclinal superjacent rocks along the western boundary of the Klamath Mountains. The Redwood Mountain and Patrick Point outliers'in California, and the outlier formerly considered part of the Klamath Mountains in southwestern Oregon, are postulated to be thrust outliers of the western Jurassic plate resting on eugeosynclinal superjacent rocks. The eugeosynclinal superjacent rocks along the west— ern boundary of the Klamath Mountains are, at least locally, of Early Cretaceous age and are mildly meta- morphosed. It is noteworthy that equivalent shelf de- posits, adjacent or only a few miles to the east, are not metamorphosed and lie with depositional contact on thrust plates of subjacent rocks that are structurally higher than the eugeosynclinal superjacent rocks. Hence, the thrusting along the boundary of the Kla- math Mountains clearly postdates the Nevadan orogeny, IRWIN and is younger than Early Cretaceous. The south- western Oregon outlier is particularly interesting, as it includes not only subjacent rocks (Galice Formation, Colebrooke Schist, and granitic rocks) of the western Jurassic belt, but also superjacent shelf deposits that were laid down on the subjacent rocks of the plate be- fore the plate was thrust over the superjacent eugeo— synclinal rocks. The thrusting that formed the boundary fault along the west side of the Klamath Mountains presumably was contemporaneous with the thrusting that controlled the emplacement of the ultramafic rocks of the Coast Range belt. The thrusting in both cases is clearly later than Early Cretaceous, and an apparent juxtaposition of superjacent shelf deposits of Late Jurassic and Early Cretaceous age against eugeosynclinal strata of early Late Cretaceous age in the San Francisco Bay area of California and Roseburg area of Oregon suggests that the age of the Coast Range orogeny is post-early Late Cretaceous. An upper limit to the age of the Coast Range orogeny is inferred from the relation of late Late Cretaceous shelf deposits to the older superjacent strata. In the Great Valley, deposition of the super- jacent shelf deposits was virtually conformable into the late Late Cretaceous. In the Coast Ranges, however, the relation is one of great unconformity at the few places where the late Late Cretaceous shelf deposits are known to occur on the older shelf and eugeosynclinal rocks. REFERENCES Bailey, E. H., and Irwin, W. P., 1959, K—feldspar content of Jurassic and Cretaceous graywackes of northern Coast Ranges and Sacramento Valley, California: Am. Assoc. Pe- troleum Geologists Bull., v. 43, no. 12, p. 2797—2809. Bailey, E. H., Irwin, W. P., and Jones, D. L., 1964, Franciscan and related rocks, and their significance in the geology of western California: California Div. Mines and Geology Bull. 183. [In press] Curtis, G. H., Evernden, J. F., and Lipson, J., 1958, Age determi- nation of some granitic rocks in California by the potas- sium-argon method: California Div. Mines Spec. Rept. 54, 16 p. I» 09 Davis, G. A., and Lipman, P. W., 1962, Revised structural se- quence of pre-Cretaceous metamorphic rocks in the south- ern Klamath Mountains, California: Geol. Soc. America Bull., v.73, p. 1547—1552. Diller, J. S., 1898, Description of the Roseburg quadrangle: U.S. Geol. Survey Geol. Atlas, Folio 49, 4 p. 1902, Topographic development of the Klamath Moun- tains: U.S. Geol. Survey Bull. 196, 69 p. Hershey, O. H., 1901, Metamorphic formations of northwestern California : Am. Geologist, v. 27, p. 225—245. Imlay, R. W., Dole, H. M., Wells, F. G., and Peck, D. L., 1959, Relations of certain Jurassic and Lower Cretaceous forma- tions in southwestern Oregon: Am. Assoc. Petroleum Geolo- gists Bull., v. 43, no. 12, p. 2770—2785. Irwin, W. P., 1957, Franciscan group in Coast Ranges and its equivalents in Sacramento Valley, California: Am. Assoc. Petroleum Geologists Bull., v. 41, no. 10, p. 2284—2297. 1960, Geologic reconnaissance of the northern Coast Ranges and Klamath Mountains, California, with a sum- mary of the mineral resources: California Div. Mines Bull. 179, 80 p. 1961, Specific gravity of sandstones in the Franciscan and related Upper Mesozoic formations of California: Art. 78 in U.S. Geol. Survey Prof. Paper 424—B, p. B189—Bl91. 1963, Preliminary geologic map of the Weaverville quadrangle, California: U.S. Geol. Survey Mineral Inv. Field Studies Map MF—275. Irwin, W. P., and Bath, G. D., 1962, Magnetic anomalies and ultramafic rock in northern California : Art. 25 in U.S. Geol. Survey Prof. Paper 450—B, p. B65—B67. Irwin, W. P., and Lipman, P. W., 1962, A regional ultramafic sheet in eastern Klamath Mountains, California: Art. 67 m U.S. Geol. Survey Prof. Paper 450—0, p. 018—021. Jenkins, 0. P., 1938, Geologic map of California: California Div. Mines, 6 sheets. Lawson, A. C., 1914, Description of the San Francisco district; Tamalpais, San Francisco, Concord, San Mateo, and Hay- ward quadrangles: U.S. Geol. Survey Geol. Atlas, Folio 193, 24 p. Merriam, C. W., 1961, Silurian and Devonian rocks of the Klamath Mountains, California: Art. 216 in U.S. Geol. Sur- vey Prof. Paper 424—0, p. 0188—0190. Strand, R. G., 1962, Geologic map of California, Olaf P. Jenkins edition, Redding sheet: California Div. Mines and Geology. 1964, Geologic map of California, Olaf P. Jenkins edi— tion, Weed sheet: California Div. Mines and Geology. Wells, F. G., and Peck, D. L., 1961, Geologic map of Oregon west of the 121st meridian: U.S. Geol. Survey Misc. Geol. Inv. Map I—325. GEOLOGICAL SURVEY RESEARCH 1964 WESTWARD TECTONIC OVERRIDING DURING MESOZOIC TIME IN NORTH-CENTRAL NEVADA By ROBERT E. WALLACE and NORMAN J. SILBERLING, Menlo Park, Calif. Work done in cooperation with the Nevada Bureau of Mines Abstract.—Large-scale overturned folds indicate that higher structural units rode westward over lower units during J urassic- Cretaceous orogeny. The examples discussed are in a belt ex- tending from the vicinity of Lovelock, Nev., to the Hot Springs Range northeast of Winnemucca, Nev., a distance of more than 100 miles. The purpose of this article is to reemphasize the pres- ence of a westward-directed movement pattern of Meso- zoic age in the tectonics of north-central Nevada, a fact which may be lost sight of in the discussions of more predominant eastward-directed movement patterns of Paleozoic age of the Roberts Mountains thrust (Roberts and others, 1958, p. 2850—2854), and other large thrusts of Late Cretaceous and early Tertiary age in the cen- tral and eastern Great Basin. The chief evidence presented here that higher struc- tural units have ridden westward over lower units is the geometry of large-scale overturned folds. Although thrust faults are involved in this movement pattern, the direction of movement of upper-plate rocks com— monly cannot be determined frOm thrust relations alone; neither is the relation of folding and thrust faulting clear in every case. The term “tectonic over- riding” is used as a general descriptive term to include any type of strain, either folding or faulting, in which higher tectonic reference points move over lower refer- ence points. By use of this term, genetic implications, such as the nature of coupling between folds and faults or origin of stresses, are avoided. Muller (1949, p. 54) first postulated westward over- thrusting of Jurassic age in the region, and Willden (1961, p. 0116) describes paleogeographic evidence for a westward-directed thrust of post-Middle Triassic age in the Kings River Range, Nev. Silberling and Rob- erts (1962, p. 50—52) discuss possible movement direc- tions of post—Triassic thrust plates as based on paleogeo- graphic relations of Triassic rocks, and prefer the interpretation of westward overriding along the Tobin, Willow Creek, and other faults of known Mesozoic age in the East, Tobin, and Sonoma Ranges. The examples of overturned folds discussed below and illustrated on figure 2 are in a northeast-trending belt extending from the vicinity of Lovelock, Nev., to the Hot Springs Range northeast of Winnemucca, Nev. (fig. 1). Although the belt is only crudely defined, there seems to be enough regional data now available to estab- lish its reality as a more or less continuous movement field. The entire extent of the westward-movement field is as yet unknown, but the small remnant of a westward- directed thrust plate described by Willden in the Kings ' River Range is about 40 miles northwest of the Hot Springs Range. Westward tectonic overriding represented in all ex- amples cited except in the Hot Springs Range probably is related to Jurassic—Cretaceous orogeny. Within the belt, intrusive rocks believed to be of Late Jurassic or Early Cretaceous age seem to be unaffected by the fold- ing. However, ages of all critical intrusive bodies are not known with certainty. In the Hot Springs Range, only rocks of Cambrian age are involved, and Roberts and others (1958, p. 2829) believe that these rocks are in approximately normal position on the west flank of a major anticline. In the Edna Mountains, strata of the Preble Formation, also part of the anticline, are over— lain unconformably by the Antler sequence which ranges in age from Middle Pennsylvanian to Permian. The implication, although indirect, is that the overturned folds in Cambrian rocks of the Hot Springs Range were produced in pre-Middle Pennsylvanian time. We U.S. GEOL. SURVEY PROF. PAPER 501-0, PAGES Clo—013 ClO WALLACE 118° 117° \. l H Kings Trout River Creek ) Range Mtns 50 MILES 1 4i 1 l l I x l l l 1 FIGURE 1.—Map showing location of examples of westward over- riding of probable J urassic-Cretaceous age. Letters and accom- panying lines indicate location of sections shown on figure 2. believe that this indirect implication is not sufficiently strong to rule out the possibility that the asymmetry of the folds in the Hot Springs Range is indeed related to J urassic—Cretaceous orogeny, even though some type of deformation prior to Middle Pennsylvanian time is clearly represented. In contrast to the movement pattern in this belt, Rob- erts (1951) found that in the Antler Peak area to the east, overturning is predominantly toward the east and is of Paleozoic age. James Gilluly and Olcott Gates (report in preparation) show similar relations in the northern Shoshone Range. To the west, in the Jackson Mountains, overturning and thrusting of probable Late Cretaceous and early Tertiary age is directed eastward (Willden, 1958, p. 2397). The belt of westward overriding may represent sec- ondary structures complimentary to a more general eastward-directed movement pattern, forming where eastward movement of upper-plate rocks was locally impeded. Or, more likely, it may represent a period of 732—760 0—-64—2 AND SILBERLING 'Cll movement reversal, possibly more widespread than now recognized. EXAMPLES OF OVERTURNED FOLDS Hot Springs Range (fig. 2A) (Hate and Willden, 1.960) .—Rocks of the Harmony Formation of Late Cam- brian age underlie most of the Hot Springs Range and have been thrown into a series of overturned folds, the axial planes of which strike about N. 20° E., and have dips ranging from 45° to 55° E. Western Sonoma Range (fig. QB) (Ferguson and others, J.951).—A series of large faulted overturned folds, involving rocks of the Prida, Natchez Pass, Grass Valley, Dun Glen, and Winnemucca Formations of Middle and Late Triassic age are overridden by rocks of the Harmony and Sonoma Range Formations of Late Cambrian and Ordovician( ?) ages respectively. The axial planes of the folds strike almost north and dip about 50° E. Some of these folds may be collinear with folds in the northeastern East Range. Northeastern East Range (fig. 20) (Ferguson and others,1.951).—An overturned syncline and anticline in- volve rocks of the Prida, Natchez Pass, Grass Valley, Dun Glen, and Winnemucca Formations of Middle and Late Triassic age as well as the underlying Koipato Group of Permian and Early Triassic age. Axial planes strike about N. 30° E. and dip about 55°. Sil- berling and Roberts (1962, pl. 2) regard these rocks, as well as the underlying Havallah Formation, as having been overridden from the southeast by the Paleozoic rocks that form the upper plate of the Willow Creek thrust. Western East Range (fig. 21)) .—An overturned anti- cline extends for about 10 miles along the western flank of the East Range. The strike of its axial plane ranges from north to N. 35° E., and its dip from 40° to 60° E. Rocks of the Leach and Inskip Formations are involved in the fold, and the entire block is thrust over rocks of the Winnemucca sequence. Silberling and Roberts (1962, p. 46) suggest that the Leach is of Ordovician age and that the Inskip may be of Mississip- pian age, but age assignments are still uncertain. Northern Humboldt Range (fig. 2E) .——The over- turned flank of a major fold represents westward overriding. This movement pattern appears to be superimposed upon a smaller scale and possibly older pattern of eastward overriding, including overturned folds and thrust faults. At the extreme north end of the range and in low hills northeast of the main Hum- boldt Range, the overturned flank approaches a recum- bent attitude. Strata of the Koipato Group of Permian and Early Triassic age and of the Prida, Natchez Pass, and Grass Valley Formations of Middle and Late Triassic age are involved in the deformation. C12 ’ STRUCTURAL GEOLOGY W E 4000’ 4000’ 2000' _ ‘ T. \ «44¢! ' , . 2000' o smmhmmss‘ O O l 2 MILES O 1 2 MILES A. Hot Springs Range B. Western Sonoma Range, Mullen Canyon C. Northeastern East Range NW SE 9000- \ \ — 9000' 8000’ — — 8000’ 7000’ — - 7000’ 6000’ — 6000’ 5000' — 5000’ 4000’ — 4000’ 3000’ .1 3000’ 2000’ —- 2000’ 1000’ — 1000’ O SW NE SW NE O 1 2 MILES l—L—J F. .Southern Humboldt Range G. West Humboldt Range, Gypsum Peak FIGURE 2.—Diagrammatic sections illustrating overturned folds described in text. Location of sections shown on figure 1. Symbols: C. Cambrian; 0, Ordovician; M, Mississippian; P, Permian; 'fi, Triassic; J, Jurassic. Patterns show structure of the folded beds but do not necessarily indicate the lithology. WALLACE AND SILBERLING Southern Humboldt Range (fig. 2F).——A large fan fold is interpreted as representing an overall movement direction to the southwest. The southwest limb is the larger, far more complex limb of the two and is recum- bently overturned. Rocks of Late Triassic and Early Jurassic age are involved. West Humboldt Range (fig. 20) .—Due east of Love- lock, Nev., a thrust plate composed of rocks of Late Triassic age rests on rocks of Early Jurassic age. Along the western margin of the thrust plate as exposed, gyp- siferous beds and their enclosing strata have been thrown into an asymmetric syncline. The age of the gypsiferous beds is not certain but is believed to be Early Jurassic. The asymmetry of the fold, the axial plane of which dips about 50° E., implies overriding from east to west. REFERENCES Ferguson, H. G., Muller, S. W., and Roberts, R. J ., 1951, Geology of the Winnemucca quadrangle, Nevada: US. Geol. Survey Geol. Quad. Map GQ—ll. Cl3 Hotz, P. E., and Willden, Ronald, 1960, Preliminary geologic map and sections of the Osgood Mountains quadrangle, Humboldt County, Nevada: US. Geol. Survey Mineral Inv. Field Studies Map MF—161. [1961] Muller, S. W., 1949, Sedimentary facies and geologic structures in the Basin and Range province, tn Longwell, C. R., chm, Sedimentary facies in geologic history [symposium] : Geol. Soc. America Mom. 39, p. 49—54. Roberts, R. J., 1951, Geology of the Antler Peak quadrangle, Nevada: US. Geol. Survey Geol. Quad. Map GQ—lO. Roberts, R. J ., Hotz, P. E., Gilluly, James, and Ferguson, H. G., 1958, Paleozoic rocks of north-central Nevada: Am. Assoc. Petroleum Geologists Bu11., v. 42, no. 12, p. 2813—2857. Silberling, N. J ., and Roberts, R. J ., 1962, Pre—Tertiary stratig- raphy and structure of northwestern Nevada: Geol. Soc. America Spec. Paper 72, 53 p. Willden, C. R., 1958, Cretaceous and Tertiary orogeny in Jack- son Mountain, Humboldt County, Nevada: Am. Assoc. Petroleum Geologists Bull., v. 42, no. 10, p. 2378—2398. 1961, Major westward thrusting of post-Middle Triassic age in northwestern Nevada: Art. 192 in. US. Geol. Survey Prof. Paper 424—0, p. 0116-0118. GEOLOGICAL SURVEY RESEARCH 1964 STRIKE-SLIP FAULTING AND BROKEN BASIN-RANGES IN EAST-CENTRAL IDAHO AND ADJACENT MONTANA By EDWARD T. RUPPEL, Denver, Colo. Abstract—The Lost River Range, Lemhi Range, and Beaver- head Mountains, basin-ranges in east-central Idaho and adjacent Montana, were broken in Pleistocene time by north-trending, dominantly right-lateral strike-slip faults. These faults, which control a peculiar pattern of mountain spurs and reentrant valleys, are in a zone about 50 miles wide that extends north- ward about 150 miles from Arco, Idaho, into the Big Hole Basin, Mont. The Lost River and Lemhi Ranges, and the Beaver- head Mountains of east-central Idaho and adjacent Montana are remarkably long mountain ranges that trend N. 30° W., are separated by broad valleys, and have long been recognized as basin-ranges (fig. 1) (Meinzer, 1924, p. 5, 15—16; Shenon, 1928, p. 5; Ander- son, 1947, p. 67—68). Only a few range-front faults have been mapped, however, and the ranges and valleys have at times been attributed to erosion (Umpleby, 1913, p. 30), thrust faulting (Kirkham, 1927, p. 24), or down- warping (Ross, 1961, p. 236; 1947, p. 1137—1139; 1938, p. 85—87). Range-front faults were first recognized by Shenon (1928, p. 5) along the southwest side of the Beaverhead Mountains near Nicholia, and the fault on the southwest side of the Lemhi Range near Patterson was later recognized and mapped by Ross (1947, p. 1137—1139). Baldwin (1951, p. 892) discussed frontal faults bounding the southwest sides of both the Lemhi and Lost River Ranges. The physical characteristics of the basins and ranges have been described by Anderson (1947, p. 63—67). Most of these writers have commented, too, on the offset or broken pattern of the basin-ranges. Umpleby (1917, p. 16, 19), Kirkham (1927, p. 10), and Anderson (1947, p. 70) described the reentrant valleys in the Arco Hills (12 1 fig. 1) and at Wet Creek (8) and considered them to be old erosion valleys flooded with lava. Bald— win ( 1951, p. 892, 899) mentioned the “. . . ofl'set pat- 1Numbers shown in parentheses in text refer to localities shown on figure 1 and in the table. tern of the ranges,” and ascribed the ofl'sets to range- front normal faults. The examples cited by these writers are mostly in the Lost River Range, but similar topographic features are also characteristic of both the Lemhi Range and Beaverhead Mountains (see accom— panying table). The striking similarities among the broken basin- ranges suggest a common cause. In the Lemhi Range and Beaverhead Mountains, near the town of Leadore, detailed mapping has shown that the broken pattern is controlled by north-trending strike-slip faults; in the other areas, reconnaissance mapping suggests that the broken pattern is invariably controlled by strike-slip faults similar in nearly all respects to those near Lea- dore. The broken basin-ranges of east-central Idaho and adjacent Montana therefore reflect a major zone of strike-slip faulting as much as 50 miles Wide that ex— tends northward from the Snake River Plain near Arco, Idaho, to the Big Hole Basin in western Montana, a dis- tance of nearly 150 miles. The zone may extend into the Bitterroot Valley in western Montana. CENOZOIC STRUCTURAL EVENTS NEAR LEADO‘RE, IDAHO Early faulting 2 The history of faulting is best known in the area of detailed mapping near Leadore, Idaho. The earliest faults recognized there are flat thrusts that break the pre-Tertiary rocks in the Lemhi Range and in the Bea- verhead Mountains. The thrusting occurred before the eruption of the Challis Volcanics, which probably are mainly of Oligocene age but may extend into the Eocene and the lower Miocene (Ross, 1961, p. 179). The flat thrust faults north of Leadore were broken by west- trending high-angle faults of uncertain age, and sub- sequently both of these early sets of faults were moder- ately folded. Following the folding, movement on the 3Early Cenozoic faults are not shown on figure 1. U.S. GEOL. SURVEY PROF. PAPER Sol-C, PAGES 014-018 014 RUPPEL 015 113°30' 113° _-_£ew______ E I I l UNITED STATES Big Hole Basin EXPLANATION |I | iii 755% ** ? Strike-slip Normal fault Thrust fault fault Range from; hachures Sawteeth on on downthrown side upper plate Faults Solid where mapped in detail; dashed where mapped in recon- naissance; dashed and dotted where topography suggests faulting, but not examined in field ' LOCALITIES REFERRED TO IN TEXT Lost River Range: 1. Freighter Spring 2. Elkhorn Creek 3. Lower Cedar Creek 4. Elbow Canyon-Pass Greek 5. King Mountain 6 7 8 9 . Brier Canyon—Arco Pass . Upper Pahsimeroi River . Wet Creek . Hurst Creek 10. Donkey Hills 11. Hawley Mountains 12. Arco Hills Lemhi Range: 13. Goldburg 14. Warm Creek—Sawmill Canyon 15. Cedar Run 16. Fallert Springs 17. Swan Basin—Big Timber Creek 18. Leadore Hill 19. Coalkiln Canyon—Keg Gulch 20. Bald Mountain Beaverhead Mountains: 2]. Peterson Creek 22. Mollie Gulch—Grizzly Hill 23. Cedar Gulch 24. Poison Spring 25. Timber Canyon 26. Upper Big Hole Basin 27. Upper Horse Prairie 28. Big Hole Divide 29. Jeff Davis Peak 30 MILES 0 10 20 44.0 FIGURE 1.—Late Cenozoic faults in east-central Idaho and adjacent Montana. Mountains shown by pattern. 016 STRUCTURAL GEOLOGY Topographic features related to strike-slip faulting at various localities in the basin-ranges of east-central Idaho and adjacent Montana [Numbers in parentheses refer to localities shown on figure 1] Idaho Idaho and Montana Major topographic feature Lost River Range Lemhi Range Beaverhead Mountains—Bitterroot Range Sharply angled or offset range (1) Freighter Spring 1 (13) Goldburg 2 (21) Peterson Creek 2 front. (2) Elkhorn Creek 1 (14) Warm Creek 2 (22) Mollie Gulch 3 (3) Lower Cedar Creek 1 (15) Cedar Run 2 (23) Cedar Gulch 3 (4) Elbow Canyon 2 (16) Fallert Springs 2 (24) Poison Spring 1 (5) King Mountain 2 (25) Timber Canyon 2 (6) Brier Canyon, Arco Pass 2 Reentrant valleys ______________ (7) Pahsimeroi River 2 (17) Swan Basin 3 (26) Upper Big Hole Basin 2 (8) Wet Creek 2 (27) Upper Horse Prairie 2 (9) Hurst Creek 2 Mountain spurs ________________ (10) Donkey Hills 2 (18) Leadore Hill 3 (28) Big Hole Divide 2 (11) Hawley Mountains 2 (19) Coalkiln Canyon and (29) Jeff Davis Peak 2 (12) Arco Hills 2 Keg Gulch 1 (20) Bald Mountain 1 l Not studied in field; fault origin not proved. normal faults of the range-front system started to block out the mountains in their present form. Range-front faults The time of movement on the range—front faults can- not yet be dated very closely, but the relation of range- front faults and valley fill in the Lemhi Valley suggests that most of the movement was in Miocene and Pliocene time. The valley fill seems to consist largely of tuif and tufl’aceous elastic rocks, and gravity data suggest that it is at least 9,000 feet thick (W. T. Kinoshita, writ- ten communication, 1962). In the southern part of the Lemhi Valley the valley-fill deposits are everywhere bounded by range-front faults or by the younger strike- slip faults, but equivalent rocks farther north in the valley unconformably overlie the Challis Volcanics (An- derson, 1961, p. 32). The oldest valley-fill rocks are along the range front north of Leadore; vertebrate fossils from these tuiface- ous rocks have not been studied in any detail, but in gen— eral a Miocene age seems likely, perhaps middle Miocene (Wilson, 1946; Schulz and Falkenbach, 1947, p. 186— 187; Anderson, 1961, p. 34; L. P. Richards, written com- munication, 1962). About a third’ of these rocks are tufi'aceous conglomerate mainly composed of subangular to subrounded pebbles, cobbles, and boulders from the Precambrian and Paleozoic rocks in the adjacent Bea- verhead Mountains, which suggests that movement on the frontal fault system was about contemporaneous with deposition. Clean, fine-grained tufl" and tuffaceous rocks on Mid- dle Ridge, east of Gilmore, are at the present top of the valley fill. Knowles 3 considered these rocks to be 3R. R. Knowles, 1960, Geology of the southern part of the Leadlore quadrangle, east-central Idaho: Pennsylvania State Univ., M.S. thesis, 1). 71. 2 Area of reconnaissance mapping. 3 Area of detailed mapping. no older than Pliocene, on the basis of fresh-water dia- toms contained in them, and it seems unlikely that their deposition could have continued long into the Pleisto- cene, for the deposits are beveled by a pediment that is capped by moraine of probable early Wisconsin age and that must have been cut largely in late Pliocene and early Pleistocene time. The pediment also cuts across the range-front fault on the west side of Middle Ridge and bevels the pre-Tertiary rocks between the fault and the present mountain front, which lies more than a mile to the west. After the moraine was deposited, the pedi- ment east of the fault was raised by about 400 feet of reverse movement on the range-front fault; except for this reverse movement, the range-front fault near Gil- more must have been inactive during the time of pedi- ment cutting, and consequently since late‘ Pliocene or early Pleistocene time. The range-front fault system on the east side of the Lemhi Valley must have had periodic normal movement to very recent time, even though the main movement was earlier. No pediment cuts across this fault system, the drainage pattern is disrupted at the range front, young alluvial fans are beheaded at the range front, and the steep westward—facing slope of the Beaverhead Mountains clearly is a but slightly modified fault scarp. Reconstruction of drainage profiles in some of the can- yons north of Leadore suggests that the latest move- ment on this fault system relatively lowered the valley block about 200 feet. However, the very late move— ments on the range-front system may represent local readjustments related to movement on the north-trend- ing faults. The history of range-front faulting in the Big Lost River Valley, the Pahsimeroi—Little Lost River Valleys, RUPPEL and the Birch Creek Valley has been similar to that in the Lemhi Valley. North-trending strike-slip faults The north-trending faults in the vicinity of Leadore cut all of the other faults. This faulting probably could not have begun much before the culmination of major movement on the range-front faults in late Pliocene or early Pleistocene time. The major displacements prob- ably were completed by late Pleistocene time, for some faults are partly obscured by late Pleistocene surficial deposits, most drainage interrupted by the faults has been reintegrated, and many large canyons are partly out along north-trending faults. Nevertheless, some movement is more recent—the lower parts of some glaciated valleys south of the Swan Basin (17) in the Lemhi Range appear to have been cut off, some of the younger glacial deposits west of Leadore are displaced, and some of the faults out very young surficial deposits, behead young alluvial fans, and disrupt present drain- age patterns. Despite their youth, most of the north-trending faults are not particularly obvious. But the faults near Lea- dore and those in the other areas share many common characteristics, and exhibit most of the features said to be typical of strike-slip faults (DeSitter, 1959, p. 173—174). The faults are exceptionally straight, and many of them maintain their northward strike for many miles; their dips are vertical or nearly so. Brec- ciated zones as much as 500 feet wide are present at many places along the faults, commonly with corre- spondingly Wide depressions cut into them; at as many other places, the faults are clean breaks without recog— nizable breccias. At Brier Canyon (6) and west of Saw- mill Canyon (14), beds of sedimentary rocks have been dragged parallel to the faults. Landslides and slumps that are covered with thin soil and sparse vegetation, but that retain their initial hummocky form, are com- mon along the faults and clearly were triggered by movements on them. The larger strike-slip faults are accompanied by many parallel small faults, and some are linked together by curving northwest— and northeast-trending faults that transferred the major movement from one north- trending fault to another. At the north end of Leadore Hill (18), the strike—slip faults appear to merge with flat, south-dipping thrust faults. Similar thrusts prob- ably are present at the north end of the Hawley Moun- tain spur (11) and north of Arco Pass (9), but they have not yet been recognized in the Arco Hills (12) 4 or in the Donkey Hills (10) (Ross, 1947) ; the geology 4 J. P. Shannon, Jr., 1959, Geology of the Howe Peak area, Lost River Range, Butte County, Idaho: Northwestern Unlv., M.S. thesis. 017 of the mountain spurs in Montana, the Jeff Davis Peak area (29) and the Big Hole Divide (28), is virtually unknown. North of Leadore, on Grizzly Hill (22) , the horizontal displacement on individual north-trending faults is as much as 11/2 miles, and the aggregate displacement on groups of closely spaced faults is as much as 4 miles. The north-trending segment of the Lemhi Valley be- tween Lemhi and Tendoy, northwest of Leadore, may be controlled by faults with an aggregate horizontal displacement of about 8 miles. In the Swan Basin (17), south of Leadore, horizontal displacement on the faults is more difficult to determine, but possibly the aggregate movement has been about 8 miles. In the Lost River Range and Beaverhead Mountains, the hori- zontal movements seem to be of the same order of magni- tude. Geologic evidence indicates that the displace- ment is right lateral on most of the strike slip faults, although the offset pattern of the ranges suggests left- lateral displacement; the reason for this anomalous re- lation is not yet clear. The amount of vertical displacement on the faults appears to be small, but it can be satisfactorily deter- mined in only a few places. Some of the smaller strike- slip faults on Grizzly Hill, faults that have several hundred feet of horizontal displacement, have no ap- preciable component of vertical movement, for they do not break the smoothness of stripped thrust surfaces that control much of the rolling upland topography here. The Cedar Gulch fault (23) east of Leadore, offsets the range-front fault system about 6,000 feet horizontally, beheads very young alluvial fans, and is responsible for offsets in the distribution of Tertiary tuffaceous rocks and in drainage mentioned by Alden (1953, p. 41). This fault together with other parallel faults has triggered large landslides in the basin south of Bannock Pass. Closely comparable faults in the other areas (fig. 1) include the fault on the east side of Sawmill Canyon (14) in the Lemhi Range and the Elbow Canyon fault (4) in the Lost River Range east of Mackay. The calculated vertical displacement nec- essary to give the apparent horizontal displacement on the Cedar Gulch fault is about 4,000 feet—and yet this young fault, with all its effects on upper Tertiary and Quaternary deposits, is without any well-defined scarp. By way of contrast, the older range-front faults are marked by the looming scarp front of the Beaverhead Mountains, almost 2,000 feet high. The same sort of calculation can be made for most of the other north— trending faults in the Beaverhead Mountains near Leadore, and the conclusion that movement on the faults was dominantly horizontal seems inescapable. The widely distributed north-trending faults in east-central C18 Idaho and adjacent Montana clearly are part of a single strike-slip system on which there has been much hori- zontal displacement in relatively recent times. The forces responsible for the strike-slip faulting are not yet understood, but a genetic relation is suggested by the coincidence in time of strike-slip faulting, erup- tions of most of the basaltic lavas in the Snake River Plain, development of the Snake River depression in the eastern, northeast—trending part of the Snake River Plain, and the arching north of this part of the Plain (Kirkham, 1927, p. 11, 13, 24—26). Also, the apparent western boundary of the strike-slip zone intersects the area where the Snake River Plain bends to the north- east, which is also where the Plain changes from a fault— bounded graben in its western part (Malde, 1959, p. 272; Malde and Powers, 1962, p. 1203), to a depression of uncertain origin in its eastern part. Kirkham (1927, p. 11, 13, 24—26) early believed that the eastern part of the Snake River depression was downwarped, and that accompanying isostatic uplift arched the region to the north. Hamilton (1963, p. 785), following Carey (1958, fig. 56), suggested that the eastern part of the depression is a product of tensional rifting or thinning of the crust resulting from northwestward drifting of the Idaho batholith. The forces required for tensional rifting parallel to this part of the plain trending N. 30— 40° E. can be resolved into those required to form north- trending right-lateral strike—slip faults. REFERENCES Alden, W. C., 1953, Physiography and glacial geology of western Montana and adjacent areas: U.S. Geol. Survey Prof. Paper 231, 200 p. [1954] Anderson, A. L., 1947, Drainage diversion in the northern Rocky Mountains of east-central Idaho: J our. Geology, v. 55, no. 2, p. 61—75. 6% STRUCTURAL GEOLOGY Anderson, A. L., 1961, Geology and mineral resources of the Lemhi quadrangle, Idaho: Idaho Bur. Mines and Geology Pamph. 124, 111p. Baldwin, E. M., 1951, Faulting in the Lost River Range area of Idaho: Am. Jour. Sci., v. 249, p. 884—902. Carey, S. W., 1958, The tectonic approach to continental drift, in Carey, S. W. ed., Continental drift, a symposium: Aus- tralia, Univ. Tasmania, p. 177—355. DeSitter, L. U., 1959, Structural geology: New York, McGraw- Hill Book Co., Inc., P. 173-174. Hamilton, Warren, 1963, Overlapping of late Mesozoic orogens in western Idaho: Geol. Soc. America Bull., v. 74, p. 779—788. Kirkham, V. R. D., 1927, A geologic reconnaissance of Clark and Jefierson and parts of Butte, Custer, Fremont, Lemhi, and Madison Counties, Idaho: Idaho Bur. Mines and Geology Pamph. 19, 47 p. Malde, H. E., 1959, Fault zone along northern boundary of western Snake River Plain, Idaho: Science, v. 130, no. 3370, p. 272. Malde, H. E., and Powers, H. A., 1962, Upper Cenozoic stratig- raphy of western Snake River Plain, Idaho: Geol. Soc. America Bull., v. 73, p. 1197—1220. Meinzer, O. E., 1924, Ground water in Pahsimeroi Valley, Idaho: Idaho Bur. Mines and Geology Pamph. 9, 35 p. Ross, C. P., 1938, Geology and ore deposits of the Bayhorse region, Custer County, Idaho: U.S. Geol. Survey Bull. 877, 161 p. 1947, Geology of the Borah Peak quadrangle, Idaho : Geol. Soc. America Bull., v. 58, p. 1085—1160. 1961, Geology of the southern part of the Lemhi Range, Idaho: U.S. Geol. Survey Bull. 1081—F, p. 189—260. Schulz, C. B., and Falkenbach, C. H., 1947, Merychyinae, a new subfamily of oreodonts: Am. Mus. Nat. History Bull., v. 88, art. 4, p. 157—286. Shenon, P. J ., 1928, Geology and ore deposits of the Birch Creek district, Idaho: Idaho Bur. Mines and Geology Pamph. 27, 25 p. Umpleby, J. B., 1913, Geology and ore deposits of Lemhi County, Idaho: U.S. Geol. Survey Bull. 528, 182 p. 1917, Geology and ore deposits of the Mackay region, Idaho: U.S. Geol. Survey Prof. Paper 97, 129 p. Wilson, J. A., 1946, Preliminary notice of a new Miocene verte- brate locality in Idaho [abs]: Geol. Soc. America Bull., v. 57, no. 12, p. 1262. GEOLOGICAL SURVEY RESEARCH I964 EVIDENCE FOR A CONCEALED TEAR FAULT WITH LARGE DISPLACEMENT IN THE CENTRAL EAST TINTIC MOUNTAINS, UTAH By H. T. MORRIS and W. M. SHEPARD,1 MenIo Park, Calif” Denver, Colo. Abstract—Elie apparent termination of the Oquirrh—East Tintic fold system and the East Tintic thrust fault in the lava- covered central part of the East Tintic Mountains, Utah, suggests the presence of a heretofore unsuspected northeast- trending tear fault of regional significance. This fault may be the localizing feature of yet undiscovered base-metal and silver ore deposits. The apparent termination of the Oquirrh—East Tin- tic system of folds in the lava—covered central part of the East Tintic Mountains of West-central Utah sug- gests the presence of a heretofore unsuspected northeast— trending tear fault of regional significance (fig. 1). Contributory evidence for the existence of such a struc- ture is furnished by deep drill holes that have disclosed the probable termination of the concealed East Tintic thrust fault 4 miles southeast of Eureka, and by the ex- posure of a northeast-trending tear fault with large displacement in the southern part of West Mountain, 15 miles northeast of the central East Tintic Mountains. The inferred tear fault in the East Tintic Mountains is believed to be similar to strong tear faults exposed else- where in the range and in the adjacent Gilson Moun- tains. Like some of these transverse faults, it may be the localizing feature of concealed ore deposits. The folds of the Oquirrh—East Tintic system were formed concommitantly with thrust faulting during the early Laramide orogeny and involve rocks of late Pre- cambrian to Permian age. They occur in an arcuate belt, convex eastward, that extends from the central Oquirrh Mountains near Bingham, 11 miles north of the north boundary of figure 1, to the central East Tin- tic Mountains, a distance of about 50 miles. The axes of adjacent synclines and anticlines are 3 to 5 miles apart and are approximately parallel; the minimum ampli- tudes of the folds range from 6,500 to 13,000 feet. In I Bear Creek Mining Co. the northern East Tintic Mountains the fold axes strike southeasterly, but the strike changes progressively southward until at the edge of the lava field the strike is nearly due south. The degree of asymmetry of the folds also increases southward from the Oquirrh Moun- tains, and the westernmost anticline and syncline are overturned locally near the edge of the lava field. In the East Tintic Mountains, the amplitudes of the folds increase steadily southward to the point where the folds are covered by the postorogenic volcanic rocks. South of the central part of the range, however, scat- tered erosional windows in the lavas south of the area of Tertiary intrusions show that the sedimentary rocks are not appreciably folded. The beds in general strike eastward or northeastward and dip south, forming a broad, faulted homocline that extends southward to the southernmost part of the East Tintic Mountains and eastward to the Wasatch Mountains and beyond. The abruptness of the apparent termination of the folds thus suggests the presence of a transverse fault of sufficient displacement to delimit flexures of large amplitude and regional extent. The total concealment of a fault of such large magnitude is possibly explained by the ero- sional development of an east- or northeast-trending valley along the fault zone and the filling of this valley with pyroclastic and flow rocks during the earliest phases of the volcanic eruptions. This valley has not since been reexposed. The structure of the sublava sedimentary rocks in the central East Tintic Mountains is reasonably well known from surface exposures, mine workings, and drill holes. Of particular interest is the East Tintic thrust fault (Bush and others, 1960, p. 1127—1129, 1532) that cuts the east limb of the East Tintic anticline below the lavas east of Eureka. This low-angle fault strikes northward and dips to the west; it cuts Paleozoic car- bonate rocks and quartzite and displaces them about U.S. GEOL. SURVEY PROF. PAPER 501-C, PAGES Cl9—C21 019 STRUCTURAL GEOLOGY C20 w // uW, 5 .1 a 2 11 1 tuyumm .s. s mdtmm d .. m M l ef m m emwsm m .3 s a N w c c S Wefme . M dww m d e o m m m m m fl "mmflw 7.2 .mqu m m m l t l T .w w .m N c We m "m”mAm “Em “Spm u ,m n A d .m m m /m m a imam w “up“ Mm w p m _ d . r . N w. m h .m .m. .n m be an tmm ”w dam no a t o o o b n ewfida spc ne e .vf A m ’ .m v \Z // M m 0 re .mdm uuw ah n 1m 0 L Km WV 6 C Ewe rl r e flw r a m P w W. W. e l w UDn.zMnfu hmh eld u d x m .m .m M m m .mnswofi TmW nmm m m d t ceno .P e .hxo .1 n E Q a a P hhwmmm w .m aD v u a T Swo .z. w t9 0 S T hdmmnm & _n.m m Mmmwwfi .Aw n as oit .M t FDauddS S S 9 , ' a 0 O 4 m 9 W/AWWWW, .. _ ._ ...... k. ”95W... 2:). “m... 7 W WW .1 10 MILES .——Generalized geologic map of the East Tintic Mountains and adjacent: areas, west-central Utah. FIGURE 1 Geology from original and published sources. MORRIS AND SHEPARD 5,000 feet relatively to the east. The sublava position of the thrust trace has been established by drill holes to a point 4 miles east-southeast of Eureka, where the thrust apparently ends against a concealed fault that is indicated by the pattern of drill holes to have a north- east strike and a near vertical dip. The drill holes on the northwest side of this inferred fault enter carbonate rocks of the upper and lower plates of the East Tintic thrust. On the southeast side, however, six drill holes enter rocks that structurally are best correlated with rocks deep in the lower plate of the thrust. Inasmuch as it seems to terminate the thrust, this steep, concealed fault probably has large displacement and thus may be the inferred tear fault that delimits the major folds. The indicated strike of the concealed fault is somewhat more northeasterly than the average strike of the in- ferred regional fault as shown on figure 1, but this may be the result of a local bend similar to that shown on the exposed part of the Tintic Prince fault 41/2 miles north- west of Eureka. Alternatively, the fault indicated by the drill holes may be one of several faults that together may form the concealed transcurrent structure. A fault that is the possible continuation of the in- ferred tear is exposed in the southern part of West Mountain, where it brings the upper, Permian, part of the Oquirrh Formation against rocks 25,000 or more feet lower in the section. Hintze (1962, p. 75) and others have described this fault as a thrust that dis- placed rocks of Permian age relatively southward over rocks of Cambrian to Mississippian age. An alterna— tive interpretation, which is more in keeping with the regional pattern of north-trending thrust faults and northeast-trending tear faults, is suggested from the geologic relations of the exposed rocks. The trace of the fault across the ridgelike mountain is nearly straight, indicating a steep, if not vertical, fault plane. The Permian rocks strike north-northeast and are over- turned to the east, suggesting that the rocks northwest of the fault did not move southward, but relatively east- ward, horizontally past the rocks southeast of the fault, in the manner of a tear. The projected strike, dip, and displacement of this tear are comparable with the indi- cated strike, dip, and displacement of the inferred con- cealed fault in the central East Tintic Mountains. 6% C21 Thus, this fault may be the eastward continuation of the concealed fault. If one assumes that both faults are part of a single zone of transverse tears of regional pro- portions, the strike of this zone is approximately N. 55°—60° E., which is close to the N. 60°—65° E. strike of the conspicuous Leamington fault that separates upper Paleozoic carbonate rocks and sandstone from upper Precambrian quartzite and argillite in the southern part of the Gilson Mountains. The Leamington fault is here interpreted also to be a tear fault, forming the south edge of the upper plate of the Nebo-Charleston thrust fault, which is best exposed a short distance northeast of Nephi. The absence of a comparable tear fault in the Wa- satch Range on strike with the strong fault in the southern part of West Mountain suggests the possibility that the tear fault terminates at a thrust fault whose trace is concealed beneath the alluvium in Utah Valley. A possible remnant of such a thrust fault may be the small thrust plate shown by Baker and Crittenden (1961) on the west slope of Mt. Timpanogos east of Pleasant Grove, Utah. Conclusive evidence for the existence of a major tear fault in the central East Tintic Mountains will be fur- nished only by the actual interception of such a struc- ture in mine workings. Continued exploration for blind ore bodies in the Tintic and East Tintic mining districts conceivably could test this hypothesis in the foreseeable future, especially since a transverse fault of this magni- tude may possibly be the site of undiscovered base- metal and silver ore bodies. REFERENCES Baker, A. A., and Crittenden, M. D., Jr., 1961, Geologic map of the Timpanogos Cave quadrangle, Utah: US. Geol. Survey Geol. Quad. Map GQ—132. Bush, J. B., Cook, D. R., Levering, T. S., and Morris, H. T, 1960, The Chief Oxide-Burgin area discoveries, East Tintic district, Utah; a case history, pts. 1 and 2: Econ. Geology, v. 55, no. 6, p. 1116-1147, and no. 7, p. 1507-1539. Hintze, L. F., 1962, Structure of the southern Wasatch Moun- tains and vicinity, Utah, in Hintze, L. F., ed., Geology of the southern Wasatch Mountains and vicinity, Utah: Brigham Young Univ. Geology Studies, Provo, Utah, v. 9, pt. 1, p. 70—79. GEOLOGICAL SURVEY RESEARCH 1964 SHAPE AND STRUCTURE OF A GABBRO BODY NEAR LEBANON, CONNECTICUT By MARTIN F. KANE and GEORGE L. SNYDER, Houston, Tex., and Denver, Colo. Work done in cooperation with the State of Connecticut Geological and Natural History Survey Abstract—Geologic and gravity evidence indicates that the discordant gabbroic intrusive body near Lebanon, Conn, is a northeast-trending boat-shaped mass 10 miles long, 2 miles wide, and 3,000 feet deep, attached by its stem to a dominantly northwest-trending curved sheet 15 miles long by as much as half a mile wide. An intrusive gabbro body near the village of Leba- non, Conn., (fig. 1) was first studied in detail by Dow,1 and the name Lebanon Gabbro was first applied to it in published print by Foye (1949, p. 49). These and other maps have generally shown the gabbro as an elliptical mass 4 miles long by 1 mile Wide within the Willimantic quadrangle north of Lebanon, although Percival (1842, geologic map) originally indicated that the gabbro might extend outside this small ellipse. More recent mapping (fig. 1) indicates that the gabbro ex- tends as a three-pronged pinwheel into the adjoining Columbia, Colchester, and Fitchville quadrangles, and that its surface area is more than 300 percent greater than that previously mapped. A synformal roof pend- ant of metasediments, the Kick Hill roof pendant, caps part of the gabbro north of Lebanon. The otherwise sinuously continuous gabbro body is offset by three parallel normal faults in the central part of the mass. The geologic data indicate crudely that the shape of the gabbro body might be likened to that of an elliptical pod attached by one end to a gently to steeply dipping curved tabular sheet. Foliation Within the southeastern and northwestern arms of the gabbro, the curved tabu— lar sheet, is uniformly parallel to the walls of the gabbro and generally is parallel to the schistosity and bedding of the surrounding wallrocks. Geologic evidence sug- 1D. W. Dow, 1942, The Lebanon gabbro of Connecticut: North- western Univ., unpub. M.S. thesis. gests strongly that this part of the body is tabular and probably largely sill like. Locally, however, the gabbro cuts across contacts or the strike of schistosity of the surrounding metasediments, and near the place Where the three parts of the body join, the gabbro appears to dip southward much more steeply than the nearby wall- rocks. In the northeast arm of the elliptical podlike part of the gabbro, foliation is much less uniform in strike but appears to dip inward along the northwest and southeast contacts of this part of the gabbro. Line- ation in the northeast arm trends much more uniformly; generally it is parallel to the direction of elongation of the mass, plunges inward at. a low angle from both ends, and is generally horizontal near the center. It would appear from the internal structures that this part of the gabbro may bottom at depth and be shaped like a boat attached at its stern end to the more tabular part of the gabbro. A keel for this boat can be projected from its prow end using the available lineation data, and this would indicate that the gabbro in the northeast arm should bottom at a maximum depth of 1 mile. Gravity measurements were made in'1961 along four profiles across the gabbro (fig. 1) in order to check the geologic interpretation of its shape (Bean, 1953; Bott, 1956; Kane, 1961), especially in the northeastern part of the body, and also to check on the presence or absence of the gabbro in some areas Where surface outcrops are absent and the mapping was based on indirect evidence. The gravity studies in general substantiate the geologic mapping and geologic indications of structural shape and have made them more precise. A reconnaissance gravity survey of the surrounding region (unpublished data) shows a positive anomaly over the gabbro near Lebanon, superimposed on the south flank of a larger, broader gravity low centered on the Willimantic dome. U.S. GEOL. SURVEY PROF. PAPER 501-0, PAGES C22-CZ7 C22 72°22'30” Area of report CONNECTICUT ' {25 24 COLUMBIA KANE AND SNYDER 72° 15’ 45 O WILLIlVIANTVICfl °/ go; 2* QUADRANGLE'h' (323 72°7’30” 4 1 ° 3 7' 30 0 20 E X P LA N AT I O N Contact Normal fault Gabbro of Lebanon + ‘- " a, homble’hdite b, mafie hornblende gabbra c, homblende-Motite gabbro d, biotite dion'te Metamorphic rocks, Hebron Formation or younger C] Metamorphic rocks, pre-Hebron For- mation FIGURE 1.—Generalized COLCHESTER OUADRANGLE Thrust fault Dashed where inferred B...........B , Gravity traverse 25 / Strike and dip of schistosity or foliation FITCHVILLE 15¢,— Bearing and plunge of lineation <—) Horizontal lineation 41°30' geologic map of pre-Pennsylvanian rocks in part of eastern Connecticut. Snyder, 1956—61. Geology by George L C24 In order to interpret the gravity data, specific gravities of the rocks in this part of Connecticut were measured on a Jolly balance; the averages of the measurements for certain groups of these rocks are given in the accom- panying table. These data show that the average den- sity contrast between gabbro and metamorphic country rock is + 0.2 grams per cubic centimeter. The Bouguer anomalies for four profiles over the gabbro are shown on figures 2 and 3. Profile A—A’ crosses the inferred extension of gabbro northeast of all known outcrops in an area underlain by unconsolidated sand and gravel. If the two central measurements of relatively low gravity are caused by a local thickening of the unconsolidated rocks, the anomaly (as general- ized) indicates that gabbro is present, and probably bottoms within a few hundred feet. The overall re- gional gradient in this area probably reflects a west- dipping contact with dense basement rocks at depth. Profile B—B’ (fig. 3) crosses the gabbro and its syn- formal roof pendant near the center of the northeastern arm. Because the anomaly is contained entirely within the boundaries of the gabbro, the mass of the gabbro must be concentrated inside its mapped contacts, that is, the outer boundaries dip generally inward. A simple triangular cross section, with its apex 3,000 feet below its base has a computed gravity anomaly very similar A A’ 27— 0? T 26— _ 17 (I) _i < 9 j a 2 a 25— W :16 :‘ z 24 15 STRUCTURAL GEOLOGY Densities of some rocks of eastern Connecticut ividual - Ingiiic gravistp; Unweighted $123,211” Rock type - measurements average density (g per? on small rock (g per cm!) cm!) specimens Gabbroic rocks Biotite diorite _____________ 2. 88, 2. 89 2. 89 Hornblende-biotite gabbro" 2. 91, 2. 93 2. 92 2 99 3 0 Mafic hornblende gabbro--- 3. 04, 3. 04 3. 04 ‘ ' Hornblendite _____________ 3. 10, 3. 11 3. 11 Metasedimentary country rocks Scotland Schist, muscovite schist __________________ 2. 97, 2. 97 2. 97 Scotland Schist, biotite schist __________________ 2. 73, 2. 73 2. 73 Hebron Formation, calc- silicate rock _____________ 2. 80, 2. 81 2. 81 Hebron Formation, calcar— eous biotite schist _______ 2. 73, 2. 74 2. 74 Tatnic Hill Formation, sil- limanite-garnet gneiss____ 2. 95, 2. 33, 2. 98 3. Tatnic Hill Formation, bi- otite-muscovite schist____ 2. 71, 2. 72 2. 72 2. 81 2. 8 Fly Pond Member of Tat- nic Hill Formation, calc- silicate rock _____________ 2. 87, 2. 89 2. 88 Brimfield Schist, musco- vite-biotite-garnet schist__ 2. 73, 2. 76, 2. 81 2. 82, 2. 83, 2. 89 Quinebaug Formation, hornblende gneiss ________ 2. 74, 2. 76 2. 75 Quinebaug Formation, biotite gneiss ____________ 2. 68, 2. 69 2. 69 o L 20100 40'00 60100 FEET o? D ’ MILLIGALS EXPLANATION N/N'V. Data points and unsmoothed curve / __________ / Generalized curve or regional gradient Mapped gabbro contacts 20 l! )Ll L >,‘ FIGURE 2.—Bouguer gravity anomalies and mapped geologic contacts along profiles A—A’ , 0—0’, and D—D’ across gabbro. KANE to the residual Bouguer anomaly (fig. 3). The depth of bottoming would be somewhat less if the more dense mafic phases of the-gabbro thicken with depth as as- sumed on figure 4; the depth would be somewhat more if the density contrast between gabbro and the meta- morphic country rock is less. The anomaly along pro- file B—B’ has a slight asymmetry to the south, the nature of which suggests that the effective center of mass is AND SNYDER C25 south of the profile center. Because the density of the gabbro at the surface is greater to the north of the profile center, the anomaly asymmetry is probably caused by a shape that is asymmetric to the south, in the manner shown in the preferred cross sectional shape on figure 3. The two mapped units of the synformal roof pendant are reflected by the double—stepped, flattened peak of anomaly B—B’ (fig. 3) ; the estimated depth of —5 A A A Gravity anomaly computed ' | ‘t for assumed shape\ ReSIdua gravn y ‘ —4 Generalized Bouguer 28— anomaly curve (0 _l //’¥ 5 3 :’ _3 2 z 27— A f Data points and ‘ i <0 unsmoothed curve S -’ < 5 a :1 —2 J :1 < E 26— 8 z a >-‘ I: .1 < E —1 O E 25— n: u: D (D I) O —O m 24- 23‘ 22— Reg.ona\// o—_‘_———————-fl Kick Hill roof pendant N s '— ‘dj 1000— L Assumed shape on E Gabbro (density 3.0 which computed f 2000— grams per cubic anomaly based I- centimeter) E Probable shape 0 3000 _ Metamorphic country rock (see text) l (density 2.8 grams per cubic centimeter) O 2000 4000 6000 FEET I I I I I | FIGURE 3.——Bouguer anomaly, residual gravity, and probable cross-sectional shape of northeast arm of gabbro at gravity profile B—B’. C26 STRUCTURAL GEOLOGY O 494/ a 62$ :‘ 2 m We 6 EX P LA N AT I O N \ / I ; \V \ k Contact,,or form line Fault Biotite diorite Homblende-biotite Mafic hornblende Hornblendite Solid on surface, dashed Solid 0% surface, dashed gabbro gabbro in interior of block in interior of block FIGURE 4.———Block diagram and longitudinal section of gabbro body at Lebanon, Conn. the bottom the dipping on field obse gravity pro Profile 0 in an area ‘ solidated su indicates th it continues The high over the central siderable (1 both sides, the gabbro the northw does seem surface. The stru gabbro mm of th pendant is 300 to 500 feet. Details of cont cts shown on figure 3 are based partly rvat' ns and partly on the limits imposed by file B B’. ~0’ ( g. 2) confirms the existence of gabbro whe the bedrock is buried beneath uncon— rfici‘ l deposits. Amplitude of the anomaly at t mass narrows sharply with depth if belo 2,000 feet. in profile D—D’ (fig. 2) reaches a maximum area of gabbro, but extends for a con- lstance into the areas of metasediments on an overlap possibly reflecting repetition of at depth by a branch of the fault mapped to 3st. However, the asymmetry of the curve to reflect the gentle westward dip at the ctural configuration of the entire body of ' Lebanon, Conn., inferred from gravity and 732-760 0—64 KANE AND SNYDER 6% C27 geologic data is shown on figure 4. Further work is necessary to determine the absolute limits of the ex- tremities of the body, the nature of the structure Where the three arms join, and the possible thickening with depth of the mafic gabbro phases, as postulated in the longitudinal section of figure 4. REFERENCES Bean, R. J ., 1953, The relation of gravity anomalies to the geol- ogy of central Vermont and New Hampshire: Geol. Soc. America Bull., v. 64, p. 509—538. Bott, M. H. P., 1956, A geophysical study of the granite prob- lem: Quart. J our. Geol. Soc. London, v. 112, p. 45—67. Foye, W. G., 1949, The geology of eastern Connecticut: Con- necticut Geo]. Nat. History Survey Bull. 74, 95 p. Kane, M. F., 1961, Structure of plutons from gravity measure- ments: Art. 242 in US. Geol. Survey Prof. Paper 424—0, p. 0258—0259. Percival, J. G., 1842, Report on the geology of the State of Con— necticut: New Haven, Conn, Osborn and Baldwin, 495 p. GEOLOGICAL SURVEY RESEARCH I964 OUTLINE OF THE STRATIGRAPHIC AND TECTONIC FEATURES OF NORTHEASTERN MAINE By LOUIS PAVLIDES; ELY MENCHER;l R. S. NAYLOR,” and A. J. BOUCOT,2 BeltsviIIe, Md.,- Cambridge, Mass.; Pasadena,CaIiI. Abstract—Northeastern Maine is underlain by Cambrian( ‘2) to Middle Devonian sedimentary and volcanic rocks that 10- cally have been regionally metamorphosed within the green- schist facies. These rocks are generally highly folded and faulted. Markedly contrasting Iithofacies are present between rocks of the same age in the Ordovician and Silurian; the Silurian also has contrasting biofacies relations. Vulcanism occurred from Cambrian(?) through Early Devonian time; its intensity, however, was greatest in the Ordovician and Early Devonian. Some of the Ordovician volcanic terrane emerged as land near the close of the Ordovician and in Early Silurian time. Such terrane contains peripheral deposits of Lower Si- lurian rocks with faunas that are older in the south and younger in the north, suggesting a scutheast to northwest marine trans- gression in Silurian time. At least four tectonic episodes (recognized by 3 unconformi- ties and 1 nonsequence) have affected the area: the youngest, or Acadian, is the most widespread and clearly imprinted orog- eny of the region. The initial severe folding of this orogeny was followed by the emplacement of felsic plutons and a later pulse of broad warping. Detailed and reconnaissance geologic mapping in re- cent years by geologists of the US. Geological Survey, the Massachusetts and California Institutes of Tech- nology, and others (see fig. 1) have considerably revised earlier concepts of the geology of northeastern Maine (Keith, 1933). This article summarizes some of the stratigraphic and tectonic features of the region as now known. Undoubtedly, future geologic work will revise many of these concepts. The Maine Geological Survey and the National Science Foundation financially sup- ported, in part, some of the mapping carried out by the university geologists. In general, the nomenclature used for the ages de- termined by fossils, especially in the Silurian, and con- sequently the names of the stratigraphic sections de- scribed in this article are those of the European Stand- 1 Massachusetts Institute of Technology. 3 California Institute of Technology. ard section. Although the American section is accepted for the Devonian, European terminology is also used for the Devonian in this article. The American and European Standard sections are compared in the ac- companying table. Some of the rocks in the region are not closely dated and are shown as possibly in- cluding rocks of 2 or 3 systemic subdivisions. Such lithologic units will not be discussed in this article, except as they may relate to the broad regional prob- lems. STRATIGRAPHY Cambrian Closely folded early and middle Paleozoic rocks un- derlie northeastern Maine. Although the rocks of this region at many places are weakly metamorphosed (chlorite grade), the original character of many is still well preserved. For convenience, the nomenclature of sedimentary and volcanic rocks is generally used in this article rather than metamorphic names or prefixes. The oldest rocks of the region are exposed in the Weeksboro- Lunksoos Lake anticline (fig. 1). Neuman (1962, p. 7 94) reported that these rocks from the southern part of the anticline consist of “quartzite and slate, inter- bedded in varying proportions, and contain red slate with Oldhamia smithi Ruedemann.” In assigning a Cambrian( ‘9) age to the Grand Pitch Formation, Neu- man (1962, p. 796) indicated that the formation is prob- ably of Early Cambrian age but may be as old as late Precambrian or as young as Early Ordovician. In the northern part of the anticline, near Weeksboro, the core rocks are somewhat different from typical Grand Pitch; here they consist mostly of phyllite with thin (1 inch to 1 foot) quartzite layers but locally are made up of mas— sive, thick—bedded (1 to 5 feet) quartzite with thin phyllite interbeds. Volcanic rocks occur locally with the phyllite and thin quartzite facies (Pavlides, unpub- lished data). U.S. GEOL. SURVEY PROF. PAPER Sol-C, PAGES C28-C38 C28 PAVLIDES, MENCHER, NAYLOR, AN D BOUCOT 029 Correlation of the Standard and American sections for the Ordovician through Middle Devonian1 Standard section American section Graptolibe zones Series Series Stages Givetian Hamilton Middle Middle Erian Eifelian Onondaga Upper Disconformity Emsian ' 2 Devonian Lower Schoharle Esopus Lower . . Lower Ulsterian 0r1skany Siegenlan Becraft 53.5 Upper % E New Scotland Gedinnian m .3 Lower Manlius-Coeymans Upper ‘ Cobleskill—Rondout -? ?— Upper Cayugan -? ?- Ludlovian Bertie 36 Upper L°Wer Salina l 32 Lockport W— WenIOCRian Middle Niagaran Rochester 2*6 . . C6 Clinton 25 Silurian A Upper Cl E Ba l H . 1 g l Mlddle o lbw" 2 Bl Lower Albion Medina 3.5. A4 .4 T Lower A1 16 Ashgillian Richmond 15 Upper Cincinnatian Maysville 14 Eden Caradocian Trenton 13 Wilderness (Black River) 12 . . . P terf' 11 Ordovician Middle Champlalman or 1eld Llandeilian Ashby 10 Marmor 9 Llanvirnian . 8 Whlterock 7 l Arenigian 6 Lower Canadian Canadian Series T l Tremadocian 1 1 Compiled from the following sources: Ordovician W. B. N. Berry (1960 table 1);2 Silurian and Devonian (exclusive of the Silurian graptiolite zones) Boucot and others (1964); Silurian grapbolite ones, Elles and Wood (1901- 18, p. 526) and Davis (1961, p. 2 Equivalent to zoneB of Oliver (1960) C30 STRUCTURAL GEOLOGY -:Van Buren?‘ . . 1/ ./ , 9° 68' _ . 3” ._./ 70°13 W" / , . __. -/ 47.. O, {k 11+ ..-' "'./ /§g® 2 . _ _oSt9€kh°lm// , Vs "\ '4‘. Madawaska: ‘ ' ./ ‘ e: 34 a ‘.Lake'..'_,'/ _47° L. < . . . . . / Hz: fl « ~ , . ',l .. MAINE 5'0 , 46° Q 7 /' J‘: ‘5 ‘8 '0 INDEX OF GEOLOGIC MAPPING E ake 1. Reconnaissance by R. S. Naylor - and Douglas Smith, California /‘ Institute of Technology ‘ .' 2. Reconnaissance by Ely Mencher H ’11} and students, Massachusetts \fll ’ Institute of Technology x 3. Reconnaissance by R. S. Naylor, I § \ California Institute of Tech- & nology \ ' 4. Reconnaissance and detailed Big Mathias}, mapping by R.. S. Naylor, \Lakg ’ ' Raymond Fletcher , M. T. Field, \ ‘ . A. J. Boucot, Massachusetts Institute of TechnologY; and Louis Pavlides, U. S. Geological Survey . Detailed‘ and reconnaissance mapping by Louis Pa’vlides, US. Geological Survey Detailed and reconnaissance mapping by E. B. Ekren and F. C. Frischknecht, U.S. Geo- logical Survey v! ANTICLINOR.[UM g: XOIMSNHHH MEN Area of 7. Detailed and reconnaissance ,epon - ' 'Mars _‘ 46° mapping by R. B. Neuman, U.S. _ ' ‘_ <[ 30’ Geological Survey . ‘ . ~— 8. From D. W. Rankin and Andrew ' ‘ ' . Q Griscom, i_n Boucot and others, ‘ ' ' ate“?- B . ndgev‘g‘ A O I . 4 \ i-CSE \ ' \‘ // o. Howe\\- 0r Brook l/s an: V/e‘” -° ¢ofi «' .\/)’ /.' QL—fl— 7 /,. -, o 10 20 MILES 1% ". ' I.J.....i.1 J _ p.____eeksbloro /U/\Df‘\/,- , \—\ '- '. / '~ . . '.'/-‘...'/)~\j_ \lfiig/KHUNT' . “ s ' .Island -_ ~ . ~~>RIDGE..- ‘ “350/ l/ I _ . ( ‘ _ ’“Pleasant 03 ‘ \:\"‘~‘ \ \ I - ' Fallso ,\\/ Dafsg, ,Lake . , “PTO!“ . :*~KATAHDKN Oi ’ /'.‘ '- ._\\.,‘ \vsPLEASANT~ 1...? ‘ 1/ L BATHOLITH - :\ 0r , fl , . Matmwamkea? / 'ILAl-(Eh P‘LL‘lTON . /_\“‘|I" —'\/\I\/\“,‘ ,‘~ ’ 1/ “Lake- ' ‘|‘“ 69° 68. PAVLIDES, MENCHER, NAYLOR, AND BOUCOT C31 EXPLANATION SEDIMENTARY AND VOLCANIC ROCKS INTRUSIVE ROCKS SEDIMENTARY AND VOLCANIC ROCKS NOT CLOSELY DATED ‘ \ I \ \ ’ 0f) ~’ 400 x \ Middle Devonian rocks of early Z Post-Acadian (Devonian) felsic Rocks of Early Devonian or Givetian age 5 intrusive rocks Silurian age or both W ACAD/AN OROGE/VY ’\/\.« 2 Number indicates K-Ar age of biotite, in r g millions of years 7 / m /SOV / DI D ,. L v > ofi > Rocks of Silurian or Ordovician Lower Devonian rocks of late " > " age 01‘ bOth Gedinnian to Siegenian age j Post-Early Ordovician to pre-Silu- rian age felsic and intermediate- ‘ ’W SAL/MC D/STUPBANCE M type intrusive rocks . \ . k Rocks of Early Devonian or ‘ Z Silurian or Ordovician age Lower(?) to Upper Silurian rocks 5 of early(?) Llandovery to early g Ludlow age. .1 Pattern indicates area of thermally al- a _______ __— tered rocks injected by sills and dikes Contact Fault of feline Devonian rocks Contacts and faults are Vv TA CON/C OROGE/VY m approximate 01” inferred Z < 0" E) FIGURE 1.—Generalized preliminary geologic map of northeast Lower to Upper Ordovician rocks of 5 Maine. Arenig or Whiterock to Ashgillian 0 age I]: wean/row” O quartzose 11my layers have con volute layering and subtle ’W Y M] . . A graded bedding. To some degree the 11my rocks of the ; Aroostook-Matapedia anticlinorium resemble calcareous Rocks of Cambmnm t < flysch as described by Dzulynski and others (1959, p. . 0 pre- — Arenig or Whiterock age % 1095‘1096) - Pattern indicates area injected by inter- E ' - ' medmwme intrusive mks o f Or w 5 West of the 11my rocks of the Aroostook Matapedia vician age Ordovician Most of the other major anticlinal folds of the area have Ordovician rocks in their cores (fig. 1). There is a marked contrast in facies between chiefly calcareous rocks in the eastern part of the area and sedimentary and volcanic rocks of the same age to the west. The Medux- nekeag Formation of Middle to Late( ?) Ordovician age (Pavlides, 1962) forms the core of a large regional fold herein named the Aroostook-Matapedia anticlinorium. Rocks similar to the ribbon rock member of the Medux- nekeag Formation extend from northeastern Maine across part of northern New Brunswick to the Mata- pedia Valley region of Gaspé in Quebec, and thence across the Gaspé Peninsula to about Percé (Pavlides, and others, 1961, p. B66—B67; see also Neale and others, 1961, fig. 1). In northeastern Maine the Meduxnekeag Formation consists chiefly of impure ankeritic and cal— citic layers interlayered with each other and with slate and locally with graywacke. Lenticular units of slate or slate and graywacke also are present. Locally, anticlinorium are anticlines with volcanic rocks, chert, argillite, and graywacke and slate of Ordovician age (Boucot and others, 1964; Ely Mencher, unpublished data). Graptolites Of zone 13 (Orthograptus tr'u/ncatus var. intermedius zone) of Trenton age have been found in the ribbon rock member (Pavlides and others, 1961, p. B65—B66) of the Meduxnekeag Formation in the Aroostook-Matapedia anticlinorium and also in the Castle Hill anticline (Boucot and others, 1964; W. B. N. Berry, written communication, 1961). It is possible that the Pyle Mountain Argillite of Ashgillian (Rich- mond) age at Castle Hill (Boucot and others, 1964) has an equivalent in the limy rocks of the Aroostook- Matapedia anticlinorium in Maine, although Ashgil- lian fossils have not as yet been found in the latter. The only Ordovician graptolite zone definitely deter- mined from either the Portage or Pennington anti- clines is zone 12 (Olimacograptus bicornis zone) of Wil- derness age of Cooper (1956), but possibly zone 11 (N emagraptus gracilis; Porterfield age) is also present (W. B. N. Berry, written communications, 1962 and 1963). C32 Similar facies relations are present in the southern part of the described area. Here two areas of Ordovician rocks that contrast in lithology but appear to be of the same age as the ribbon rock member of the Meduxnekeag Formation are present outside of, but on both sides of, the Aroostook—Matapcdia anticlino- rium. The rocks about 9 miles west of Monticello (fig. 1) consist of graywacke, slate, volcanic rocks, and inter- bedded carbonaceous chert (radiolarian) and argil- lite. The carbonaceous chert and argillite contain zone- 12 graptolites (W. B. N. Berry, written communication, 1961). To the south and east of Houlton the Ordovician rocks are green phyllite and black carbonaceous slate which have yielded poorly preserved graptolites, dat- able nonetheless as of zones 11 or 12 and late Middle Ordovician (W. B. N. Berry, written communication, 1961). Brachiopods occur within the Aroostook-Mata- pedia anticlinorium in ribbon rock at Houlton and are not incompatible with a Middle to Late Ordovician age (R. B. Neuman, 1961, written communication). The Ordovician rocks along the central part and at the south end of the Weeksboro—Lunksoos Lake anti- cline are chiefly volcanic rocks; they consist of green- stone, volcanic conglomerate, graywacke, and tuflaceous sandstone (Neuman, 1960). A rich brachiopod fauna from the Shin Brook Formation, which occurs in a local syncline along the central part of the Weeksboro— Lunksoos Lake anticline, dates these rocks as of Arenig or Whiterock age of Cooper (1956) (Newman, 1964). Another somewhat different suite of volcanic rocks occurs along the southeast side of the anticline (Ekren, 1961). Here the rocks are chiefly spilite, keratophyre, tufl'aceous conglomerate, and sandstone overlain by chert of Middle Ordovician age (Neuman, 1960, p. 166). At the north end of the Weeksboro—Lunksoos Lake anticline the thick sequence of volcanic rocks of the Dunn Brook Formation (Pavlides, 1964) consists chiefly of keratophyre, tufl', volcanic breccia, and con- glomerate and metaperlite with local sandstone and slate interbeds. The Dunn Brook, in part, may be equivalent to the volcanic rocks to the south along the anticline; however, it cannot be dated any closer than of Ordovician or Silurian age or both (Pavlides, 1964). Silurian Markedly contrasting depositional environments are also shown by the Silurian strata of northeastern Maine, although in the southern part of the region the contrast is more strikingly one of biofacies than lith- ofacies. West of the Aroostook-Matapedia anticli— norium in the northern part of the area the Silurian consists of the Perham and Frenchville Formations (Boucot and others, 1964). The Frenchville, the low- STRUCTURAL GEOLOGY est Silurian unit recognized in this particular belt, con- sists of lithic arkose, graywacke, conglomerate, and minor amounts of shale. Brachiopods from this unit are of late Llandoverian (C4—C5) age (Boucot and others, 1964). The Perham Formation consists mostly of shale and siltstone, minor amounts of limestone, and limestone breccia and lenticular ferruginous manga- nese deposits of sedimentary origin. Its lower member is of Wenlock age, whereas its upper member is of early Ludlow age (Boucot and others, 1964). North of the Castle Hill anticline, the Frenchville Formation crops out in the cores of smaller anticlines. It also encloses the north end of the Castle Hill anticline north of the fault that diagonally cuts the anticline (fig. 1) . South of the fault, the formation is present only on the west limb of the anticline but appears to thicken to the west and encloses the volcanic rocks of Ordovician age that make up the core of most of the smaller unnamed anti- clines there (fig. 1). To the east the stratigraphic posi- tion of the Frenchville is occupied by the so-called “nubbly limestone” (White, 1943, p. 129), which over- lies the limy Ordovician rocks of the Aroostook-Mata- pedia anticlinorium. Ostracods of about early Clinton age (late Llandovery, 03—04) have been identified from the “nubbly limestone” unit (Jean Berdan, written communication, 1963) indicating that it is of the same age as the Frenchville Formation. The Frenchville may be a near-shore or possibly even a strand-line de- posit of a mainland or islands that lay to the west, whereas the “nubbly limestone” may be the eastern lithofacies developed farther ofl'shore. The Silurian on the west flank of the Pennington anticline consists of conglomerate, limestone, and cal- careous siltstone. Clasts of the subjacent Ordovician volcanic rocks occur in conglomerate. Paleontologic data indicate that these elastic basal Silurian rocks are of early Ludlow age and hence younger than those im- mediately west of the Aroostook-Matap-edia anticli- norium. Less extreme differences in lithofacies, but marked differences in biofacies, characterize the Silurian in the southern part of the area. Here the Silurian near Smyrna Mills and Houlton (fig. 1) consists chiefly of micaceous siltstone and quartzite commonly inter- layered with slate; conglomerate and graywacke are locally abundant, and lenticular, sedimentary, ferru- ginous manganese deposits occur at several horizons. This Silurian terrane has yielded many graptolite lo- calities (Louis Pavlides and W. B. N. Berry, unpub- lished data) ranging in age from early( ?) Llandovery to early Ludlow. The presence of early( '9) and mid- dle Llandovery age rocks here contrasts with conditions in the northern part of the region where the earliest PAVLIDES, MENCHER, NAYLOR, AND BOUCOT dated rocks of Silurian age are of late Llandovery (C3-Cs) age. The rather thick section of graptolitic Silurian rocks of the eastern part of the southern region difl’ers markedly from the thinner belt of Silurian rocks along the northwest flank of the Weeksboro—Lunksoos Lake anticline. The latter rocks are chiefly sandstone, conglomerate, and siltstone. The oldest rocks in this belt have brachiopods of late Llandovery (Cs—C6) age, especially in the Shin Pond and Island Falls quad- rangles (Boucot and others, 1964). These ages cor- respond to the basal Silurian Frenchville Formation and “nubbly limestone” of the northern region, and like the Frenchville appear to be near-shore deposits. The available paleontologic evidence on the west side of the Weeksboro—Lunksoos Lake anticline also sug- gests that Silurian seas did not reach this region prior to late Llandovery time. The Maple Mountain Formation of the Hovey Group at the north end of the Weeksboro—Lunksoos Lake anti- cline cannot be more closely dated than Silurian (Pav- lides, 1964). Lenticular graywacke and conglomerate are present at the base of the formation. Above these basal rocks is a thick sequence of slate with sparser thin interbeds of graywacke and micaceous quartzite. Near the top of the Maple Mountain Formation are lenticular ferruginous manganese deposits (Pavlides, 1962). Brachiopods from the basal layers are of Silurian age, but beyond that they cannot be further subdivided. A Silurian monograptid has been found Within one of the manganese deposits (Pavlides, 1962, p. 23) ; poor pres- ervation prevents a closer dating. Devonian The oldest Devonian rocks of northeast Maine are of Late Gedinnian (New Scotland) age. Within the Chapman syncline they occur in the Dockendorfl Group (Boucot and others, 1964). The Hedgehog Formation is the basal unit of the Dockendorfl' Group and is com- posed of lenses of volcanic rocks interlayered with minor amounts of lenticular sedimentary rocks. Above the Hedgehog are three formations that appear to be litho- facies of similar age. At the north end of the Chap- man syncline is the Edmunds Hill Andesite that to the south interfingers with the Chapman Sandstone, which in turn grades southward into the Swanback Formation (argillite, shale, and quartzite). Brachiopod faunas that occur in the Hedgehog Formation, the Chapman Sandstone, and the Swanback Formation are of late Gedinnian age. Late Gedinnian age rocks also occur on the north and south sides of the Pennington anticline (Ely Mencher, unpublished data), where they consist of fossiliferous limestone, calcareous mudstone, and con- glomerate. In the southern part of the area (fig. 1), C33 rocks of late Gedinnian age consist of calcareous slate and limestone containing a shelly fauna. They occur in a few areas northwest of Houlton within terrane mapped as undifferentiated Silurian and Devonian rocks (fig. 1). Rocks younger than late Gedinnian are not known from the southern part of the region. How- ever, on the north and south side of the Pennington anti- cline (fig. 1), the upper Gedinnian rocks are conform- ably overlain by micaceous and carbonaceous mudstone and sandstone. At one locality, brachiopods from these rocks are of Becraft to Oriskany (Siegenian) age (A. J. Boucot, written communication, 1963), whereas spores from well-preserved flora are thought to range into the Middle Devonian (D. C. McGregor, written communi- cations, 1962 and 1963). For purposes of this report a Siegenian age is accepted for these rocks. These Gedinnian-Siegenian rocks appear to grade both upward and laterally into slates typical of the Se- boomook Formation. At the south end of the Penning- ton anticline, rocks of Seboomook lithology lie in direct contact with the Silurian, and fossils close to the Seboo- mook base are of late Gedinnian age (Ely Mencher, unpublished data; A. J. Boucot, written communica- tion, 1963). Blue—gray slate with minor interbeds of hard sandstone characterizes the Seboomook Formation throughout the northwestern part of the region. At the south end of the Chapman syncline and extending as far south as Howe Brook, the Seboomook consists of slate and quartzite interbedded in different proportions and is cyclically layered with quartzite grading upward into slate. At one place near Howe Brook, the Seboo- mook contains reworked brachiopods and corals of late Llandovery (Cs—C5) age near its base as well as clasts of igneous rocks probably derived from the Weeksboro— Lunksoos Lake anticline to the south. The age of the Seboomook here may be as old as Silurian (post- Llandovery) or as young as Devonian; it is pro- visionally considered to be New Scotland( ?). In most of northern Maine, however, the age of the Seboomook is Siegenian (Becraft to Oriskany). The Mapleton Sandstone west of Presque Isle (fig. 1) consists of coarse conglomerate at the base that grades upward into conglomerate and coarse sandstone; the upper part of the formation consists of sandstone and siltstone with thin beds of fine-grained conglom- erate (Boucot and others, 1964). The Mapleton rests with angular unconformity on Silurian and Lower De- vonian rocks (fig. 1). Spiny psilophytes and spores from the Mapleton suggest that it is Givetian (Upper Middle Devonian—J. M. Schopf, appendix I in Boucot and others, 1964). Two clasts from the Mapleton have been found that contain brachiopods of New Scotland age, also indicating that this formation is younger than late Gedinnian. C34 TECTONICS Structural features The Paleozoic rocks of northeastern Maine, are most- ly incompetent pelites, limestones, and tufi's. Such rocks are thrown into tightly compressed steep-limbed folds and are almost everywhere cut by steeply dipping slaty cleavage. Fold plunges range from moderate to steep, and some folds may even have inverted plunges (Pavlides, 1962, pl. 5; and unpublished data). Thick sequences of competent rocks such as those in the Chap— man syncline are more gently folded, and they have moderate to gentle dips. In general, sandstones, con- glomerates, greenstones, and some felsites constitute the competent rocks of the region. The folding described above is mostly of a rather short wave length, and such folds are second-order crenulations on the anticlinal and synclinal folds of regional extent within the area, some of which are named in figure 1. However, because of the generalization introduced into figure 1, and the scale of the map, the contacts shown, especially at the noses of folds, are of necessity smooth. The overall fold pattern of at least the northwestern part of the described area and the surface distribution of the Ordovician rocks there are thought to reflect the difference in competency between the Devonian sedi- ments and the more rigid basement of Ordovician rocks upon which they rested. The surface of this basement had considerable topographic relief and stood above the level of the Early Devonian sea in many places (Ely Mencher, unpublished data) . Transverse cleavage, with a north to northeast trend, is in many places parallel with fold axes, especially in the northern part of the area. In the southern part of the region, cleavage with a north or northeast trend locally lies athwart fold axes that trend northwest (Louis Pavlides, unpublished data) . Between Houlton and Smyrna Mills, fold axes and nearly parallel cleav- age trend east; at one place the cleavage trends north- west and reflects the drag of the nearby postkinematic Hunt Ridge and Pleasant Lake plutons (fig. 1 ). Faults are difficult to recognize, and movement direc- tion is generally not known. Strike-slip movement is probably important on some faults, especially those with a northeast strike (Pavlides, 1962, p. 47). Most of the faults probably dip steeply; low-angle thrusts have not been recognized. There is a possibility that the large, arcuate fault, extending from about 6 miles west of Bridgewater, southward towards Houlton, may, in part, be a thrust; but this interpretation awaits firmer documentation from a closer dating of some of the rocks on the east and west sides of the fault. A general curved pattern displayed by many of the large folds, as well as the second-order folds of the re- gion, is believed to be a regional feature of the tectonic STRUCTURAL GEOLOGY grain of northeast Maine. Locally, however, the trends of fold axes have been modified by the drag of post- kinematic plutons. Such modification and rotation of trends of fold axes occurred at the south end of the Aroostook-Matapedia anticlinorium where fold axes within the anticlinorium, as well as on either side of it, strike nearly east-west in contract to north and north- east trends to the east and north of this area. This rotation seems clearly related to the emplacement of the Hunt Ridge and Pleasant Lake plutons (fig. 1) . The south end of the Weeksboro—Lunksoos Lake an- ticline also appears to have been rotated from a north- east-trending fold to a southeast—trending fold because of the drag of the Katahdin batholith (fig. 1) (Boucot and others, 1960). Near the northeast end of this anti- cline the trend of the anticline is nearly north rather than northeast. Here, also, the north trend may be related to rotation by a pluton that exists at depth. A gravity low centered over the Hunt Ridge pluton (Kane and others, report in preparation) extends northward from this pluton and strikes towards the northeast end of the Weeksboro—Lunksoos Lake anticline (Andrew Griscom and M. F. Kane, unpublished data). It may reflect a buried intrusive of large size, and such an intrusive, if indeed present, could have rotated the north end of the Weeksboro—Lunksoos Lake anticline during its emplacement after regional folding. Unconformities and intrusive rocks Unconformities of both a regional and local nature occur at many places in northeast Maine. The oldest of these separates rocks of the Grand Pitch Formation of Cambrian( ’9) age, presumably by angular discordance, from the overlying Early or Middle Ordovician Shin Brook Formation (Neuman, 1960; 1964). However, Silurian rocks overlie much of the Grand Pitch Forma- tion, especially along the northwest side of the Weeks- boro-Lunksoos Lake anticline (fig. 1). The Grand Pitch Formation is complexly folded and characterized by well-developed shear cleavage that has disrupted and offset complexly folded layers. This style of deforma- tion contrasts with that in the less complexly deformed overlying younger rocks. It seems reasonable, there— fore, that the Grand Pitch Formation was affected by folding in Late Cambrian or Early Ordovician time, although the angular unconformity between the Grand Pitch Formation and the volcanic rocks is not clearly exposed. A pre-Taconic unconformity has been re- ported in the Eastern Townships of Quebec (Cooke, 1955; Riordon, 1957), but the nature and extent of the tectonic event that accompanied it have not yet been explored. Along the southeast flank of the Weeksboro—Lunksoos Lake anticline, dioritic rocks complexly inject the Mid- PAVLIDES, MENCI-IER, NAYLOR, AND BOUCOT dle Ordovician greenstones (Neuman, 1960, p. 166) and the Grand Pitch Formation of Cambrian( 2) age, indicating that this pluton and possibly the one near the north end of the anticline were emplaced at some time after the Middle Ordovician. Clasts of this pluton have been found in adjacent Silurian conglomerate of probable late Llandovery age along the southeast side of the anticline (Neuman, 1960; oral communication, 1964), indicating that the pluton is at least of pre- late Llandovery age. This and the related plutons are considered to be of Ordovician( ?) age. It is not clear, however, what the time relationship of these Ordo- vician( ?) intrusive rocks is to the Taconic orogeny (described below). The Taconic, is a rather Widespread tectonic event in parts of the northern Appalachians. It probably occurred at somewhat different times and with con- trasting types of tectonism at difierent places from Middle Ordovician through Early Silurian times (Bou- cot and others, 1964). At many places it is an angular break, but it is also commonly a disconformity, as in most parts of northeast Maine. For example, along the west side of the Aroostook-Matapedia anticlinorium, bedding is parallel between Silurian and Ordovician rocks along or near their contact. Also, the Caradocian and Ashgillian age rocks of the Castle anticline appear to be conformably overlain by late Llandovery (Ci—C5) age rocks of the Frenchville Formation. Here the stratigraphic gap may represent local uplift and non- deposition from the close of the Ordovician through pre-Frenchville Formation time. To the south, in the Smyrna Mills area (fig. 1), early ( ?) and middle Llan- dovery graptolites have been identified (W. B. N. Berry, written communication, 1962) from within the Silurian rocks (Louis Pavlides, unpublished data), and there may be even less of a stratigraphic break here, if indeed any at all is present, between the Silurian and Ordovician rocks. A nonsequence, named the Salinic disturbance by Boucot (1962), is also present in northern Maine, as well as in northern New Brunswick and adjacent Que- bec (Boucot and others, 1964). This fauna] break occurs between the Silurian and the Devonian and is characterized by the absence of rocks containing fossils of late Ludlow (Cobleskill and Rondout) age and early Gedinnian (Manlius and Coeymans) age. West of Presque Isle, for example, the Hedgehog Formation of late Gedinnian age rests on the upper part of the Per- ham Formation of early Ludlow age (Boucot and others, 1964). The Salinic disturbance may have been accompanied by local uplift. The presence of re- worked late Llandovery (Ca—Cs) age brachiopods and corals in Seboomook (New Scotland age (?)) lithology C35 near Howe Brook may represent this event, if indeed the Seeboomook here is of late Gedinnian age. The Acadian orogeny is the most important and Widespread orogeny of the northern Appalachians. It is dated west of Presque Isle (fig. 1) by the position of the Mapleton Sandstone of early Givetian (Hamilton) age, which lies with angular unconformity on both the Hedgehog Formation of late Gedinnian age and rocks of Silurian age. The Hedgehog Formation is of the same age as part of the Seboomook Formation, other parts of which may range in age up to Siegenian ( Oris— kany). BecauSe the sequence of rocks from the Hedge- hog Formation upward through the Seboomook Forma- tion is conformable and appears to have been deformed by the same orogenic event, it seems probable that the Acadian orogeny in this area took place during Emsian or Eifelian time; namely, after the Siegenian (Oris— kany) but prior to Givetian (Hamilton) time, the age of the Mapleton Sandstone. The broad open fold that the Mapleton Sandstone occupies reflects a later less severe period of folding, probably a later pulse of the Acadian orogeny. Other rocks in northern Maine that may date the Acadian orogeny are in the southwest part of the map area on the north side of the Katahdin batholith. Here the Trout Valley Formation of Dorf and Rankin, 1962, unconformably overlies the Traveler Rhyolite of Top- pan, 1932, which in turn rests conformably on rocks of Becraft and Oriskany age (Dorf and Rankin, 1962, p. 1001). Plant fossils from the basal parts of the Trout Valley have been dated as of late Early Devonian age (Dorf and Rankin, 1962, p. 1003). This age differs somewhat from the late Middle Devonian age of the flora from the Mapleton Sandstone described earlier. This difference in age between the two formations, how- ever, may be more apparent than real. It may stem from the different statigraphic positions the Onondaga is assigned by the different paleobotanists who have dated the flora from these two formations (Boucot and others, 1964). Felsic intrusive rocks were emplaced in northeast Maine following the initial severe folding of the Aca- dian orogeny. The Katahdin batholith (fig. 1) in- trudes rocks of Becraft and Oriskany age and also the Traveler Rhyolite (Rankin, 1960, p. 30). It has ther- mally altered the country rock it intrudes and has brec- ciated and locally injected some of it. The other falsic intrusives to the northeast differ from the Katahdin batholith in that they are emplaced in folded rocks no younger than early Ludlow in age; generally, they have well-developed thermal aureoles, as in the case of the Hunt Ridge and Pleasant Lake plutons (Pavlides and Canney, 1964). The Hunt Ridge pluton is unique C36 among this northeast group of intrusive rocks, in that it has a wide injected border zone on its north and east sides consisting mostly of felsic sills and dikes emplaced in thermally altered Silurian rocks. The potassium-argon age of biotite from the felsic intrusives northeast of the Katahdin batholith (fig. 1) ranges from 385 to 400 million years, compared to 360 my. for the age of biotite from the Katahdin batholith (Faul and others, 1963, p. 4—14). GEOLOGIC HISTORY Northeast Maine is part of a geosynclinal belt in which sediments and volcanic rocks accumulated inter- mittently from Cambrian( ?) to Middle Devonian time. During Cambrian( ?) time, quartzose sands and pelites of various kinds were the dominant sediments deposited (Grand Pitch Formation) . Some vulcanism character- ized the Cambrian( ‘9) in this region, as minor amounts of volcanic rocks occur within the Grand Pitch Forma- tion. At some time after the sedimentation and vul- canism but before the early Middle and Early Ordovi- cian Shin Brook Formation was deposited, the Grand Pitch Formation was folded. Following this folding and a period of erosion or nondeposition or both, a time of widespread vulcanism set in along the western part of the region. Apparently, it started and lasted through Arenig to, in part, Llanvirnian (Whiterock) times in the central and southern region of the Weeks- boro—Lunksoos Lake anticline where the rocks of the Shin Brook Formation were laid down. To the north, the oldest vulcanism recognized is of Caradocian age, as older volcanic rocks have not been recognized in the Ordovician terrane of the Pennington and Castle Hill anticlines. The younger Ordovician strata that overlie the Caradocian volcanic rocks of the Castle Hill anti- cline are the Pyle Mountain Argillite of Ashgillian age, so that vulcanism in this part of northern Maine did not extend into uppermost Ordovician (Richmond) time. The limy Ordovician ( Caradocian, in part) rocks of the Aroostook-Matapedia anticlinorium in the eastern part of northeast Maine have no associated volcanic rocks. Little if any volcanic detritus was deposited from the western volcanic terrane into the area where the con- temporaneous impure limestones of the Meduxnekeag Formation were being deposited. Here graywacke con— taining volcanic clasts occurs in the Meduxnekeag For- mation, mostly in a unit below the limestone sequence or the ribbon rock member of the formation (Pavlides, 1962, p. 10). Volcanic clasts are less common or absent in the sparse graywacke interbeds of the ribbon rock member (Louis Pavlides, unpublished data). Hence, only the western part of the region (fig. 1) was a terrane volcanically active at different times from STRUCTURAL GEOLOGY Early through Middle Ordovician time. Possibly it was a volcanic mainland or even a chain of volcanic islands. At any event, it appears to have been an area that per— mitted migration of marine faunas between northern Europe and this part of North America, as Ordovician volcanic and sedimentary rocks about 51/; miles east of Ashland contain brachiopods more common to Great Britain and Europe than to other parts of the United States (Neuman, 1963). In contrast, the eastern part of the region was one in which impure limestones were the chief sediments that formed, and they may, in part, have been deposited by turbidity currents, if some of their flyschlike features are actually reliable and are diagnostic features of turbidites. The small areas of Ordovician rocks on the southeast side of the Aroostook- Matapedia anticlinorium may also represent still an- other environment of deposition, in that they are grap- tolitic carbonaceous pelites without associated volcanic rocks. The Taconic orogeny was a period of nondeposition and local uplift. The dioritic pluton along the Lunk- soos Lake-Weeksboro anticline may have been em- placed during the Taconic. It was probably during the Taconic disturbance that the Weeksboro—Lunksoos Lake anticline and much of the other Ordovician ter- rane of the northern part of the region (fig. 1) emerged into land. The Silurian seas transgressed progressively northwestward from early( ?) or middle Llandovery to Ludlow time. By late Llandovery time they had cov- ered most of northern Maine, except that they may not have transgressed westward as rapidly, and therefore, did not reach the Pennington anticline area until early Ludlow time. Vulcanism in northeast Maine was not as pronounced during the Silurian as it was during the Ordovician. The only volcanic rocks that may have accumulated here during the Silurian are in the Dunn Brook Formation, if indeed any part of this formation is of Silurian age. Nevertheless, some volcanic activity did take place at this time as ash layers a few inches thick are interlayered with the sedimentary manganese deposits of the region (Pavlides, 1962, p. 36; White, 1943, p. 134). The source of these ash layers is not known; the ash may have been erupted from distant volcanoes. The Salinic disturbance, which separates the youngest Silurian from the oldest Devonian rocks of northeast Maine, locally may have been a period of temporary withdrawal of the seas from northern Maine or a period of nondeposition. There is no evidence of any wide- spread erosional break associated with this event, except perhaps locally as near Howe Brook (already de- scribed). With the resumption of widespread sedimen- tation in northern Maine during late Gedinnian time, PAVLIDES, MENCHER, NAYLOR, AND BOUCOT certain changes in the conditions that prevailed on the nearby land areas are reflected in the biostratigraphic record. Formations of New Scotland age, such as the Chapman Sandstone and the Swanback Formation, con- tain layers with marine invertebrate faunas as well as beds with fragments of psilophyton-type plants (Bou- cot and others, 1964; Louis Pavlides, unpublished data) ; these represent the first record of terrestrial plants in the nearby land areas of northeast Maine. Also during late Gedinnian time, northeast Maine again experienced an era of pronounced vulcanism. There are volcanic rocks interbedded in the Devonian slates on the south- west side of the Pennington anticline. The volcanic rocks of the Hedgehog Formation west of Presque Isle are part of a broad but discontinuous belt of volcanic activity that extended to the southwest of Presque Isle for about 150 miles and northeast to Chaleur Bay for about 130 miles during New Scotland time (Boucot and others, 1964, fig. 2). Some of the sedimentary rocks laid down during the Siegenian may have been deposited as turbidites, judging by such features as the cyclical layering and graded bedding that occur in much of the Seboomook Formation. These rocks are part of the Connecticut Valley—Gaspé synclinorium described by Cady (1960). Following the deposition of the Tom- hegan Formation (Boucot, 1961, p. 161—163) , now dated as of lower Emsian (Schoharie) age (Boucot, unpub- lished data), the seaways that covered northern Maine were destroyed as the Acadian orogeny began. Most of the structural features of the pre-Middle Devonian rocks of northern Maine and, indeed, of most of the northern Appalachians were imprinted by this orogeny. The rocks were closely folded and probably faulted during the Acadian, although the faults of northeast Maine are not closely dated. Slaty cleavage that paral- lels fold axes, as well as locally cuts across them, prob- ably developed as a late phase of the folding or soon thereafter. The last major event during the Acadian orogenic episode was the emplacement of postkinematic felsic plutons that locally have modified the trends of fold axes (Smyrna Mills area, fig. 1). These plutons are characterized by well-developed thermal aureoles within which cleavage is mostly obliterated or obscured. They probably were emplaced near the surface rather than at great depths within the crust and belong to the epizone, or possibly are transitional with the mesozone plutons, as defined by Buddington (1959). Regional metamorphism that affected the area prob- ably occurred nearly contemporaneously with the em- placement of the plutons. It is noteworthy that the rocks in the northern part of the region are relatively unmetamorphosed, Whereas those to the south, near the C37 areas of Devonian plutonic activity, have undergone low-rank (greenschist facies) regional metamorphism. The rank of this metamorphism corresponds to the epi- zonal nature of the plutonism. A second pulse of the Acadian orogeny or possibly a separate, later orogeny is indicated in northeast Maine by the relations of the terrestrial plant-bearing Maple- ton Sandstone. This unit lies unconformably on the steeply dipping, felded rocks deformed by the Acadian orogeny and is itself folded into an open syncline with moderate to gentle dips. With the close of the episode of post-Mapleton folding, the record of the tectonic history of northern Maine apparently ends. Presum- ably, northern Maine remained an emerged area through the rest of geologic time and possibly supplied sediment for the later Devonian and Carboniferous rocks that accumulated in southeastern Maine and in the Maritime Provinces of Canada. REFERENCES Berry, W. B. N., 1960, Correlation of Ordovician graptolittL bearing sequences: Internat. Geol. Cong., 21st, pt. 7, p. 97—108. Boucot, A. J., 1961, Stratigraphy of the Moose River syncli- norium, Maine: U.S. Geol. Survey Bull. 1111—E, p. 153—188. 1962, Appalachian Siluro—Devonian, in Coe, Kenneth, ed., Some aspects of the Vvariscan fold belt: Inter-university Geol. Cong., 9th, Exeter, Manchester Univ. Press, p. 155—163. Boucot, A. J ., Field, M. T., Fletcher, Raymond, Forbes, W. H., Naylor, R. S., and Pavlides, Louis, 1964, Reconnaissance bedrock geology of the Presque Isle quadrangle, Maine: Maine Geol. Survey Quad. Mapping Sen, no 2, 123 p. Boucot, A. J ., Griscom, Andrew, Allingham, J. W., and Dempsey, W. J ., 1960, Geologic and aeromagnetic map of Maine: U.S. Geol. Survey open-file report. Buddington, A. F., 1959, Granite emplacement with special ref- erence to North America: Geol. Soc. America Bull., v. 70, no. 6, p. 671—747. Cady, W. H., 1960, Stratigraphic and geotectonic relationships in northern Vermont and southern Quebec: Geol. Soc. America Bull., v. 71, p. 531—576. Cooke, H. C., 1955, An early Paleozoic orogeny in the Eastern Townships of Quebec: Geol. Assoc. Canada Proc. 1955, v. 7, pt. 1, p. 113—121. Cooper, G. N., 1956, Chazyan and related brachiopods [U.S.- Canada]: Smithsonian Misc. Colln., v. 127, pt. 1, p. 1—1, 024. Davis, A. M. (Stubblefleld, C. J.), 1961, An introduction to paleontology, 3d ed.: London, Thomas Murby and 00., 322 p. Dorf, Erling, and Rankin, D. W., 1962, Early Devonian plants from the Traveler Mountain area, Maine: Jour. Paleontol- ogy, v. 36, p. 999—1,004. Dzulynski, Stanislaw, Ksaizkiewiez, Marion, and Kuenen, Ph. 3., 1959, Turbidites in fly‘sch of the Polish Carpathian Mountains: Geol. Soc. America Bull., v. 70, p. 1,089—1,118. Ekren, E. B., 1961, Volcanic rocks of Ordovician age in the Mount Chase Ridge, Island Falls quadrangle, Maine: Art. 309 m U.S. Geol. Survey Prof. Paper 424-D, p. D43-D46. C38 Elles, G. L., and Wood, E. M. B., 1901-18, Monograph of British graptolites: Palaeontograph Soc. London, pt. I—XI, p. c—Ixxi and 539. Faul, Henry, Stern, T. W., Thomas, H. H., and Elmore, P. L. D., 1963, Age of intrusion and metamorphism in the northern Appalachians: Am. J our. Sci., v. 261, p. 1—19. Keith, Arthur, 1933, Preliminary geologic map of Maine: Maine Geol. Survey. Neale, E. R. W., Béland, J. R., Potter, R. R., and Poole, W. H.. 1961, A preliminary tectonic map of the Canadian Appa- lachian region based on age of folding: Canadian Mining Metall. Bu11., v. 54, p. 687—694. Neuman, R. B., 1960, Pre—Silurian stratigraphy in the Shin Pond and Stacyville quadrangles, Maine: Art. 74 m U.S. Geol. Survey Prof. Paper 400—B, p. Bl66—B168. 1962, The Grand Pitch Formation: new name for the Grand Falls Formation (Cambrian?) in northeastern Maine : Am. Jour. Sci., v. 260, p. 794-797. 1963, Caradocian (Middle Ordovician) fossiliferous rocks near Ashland, Maine: Art. 30 m U.S. Geol. Survey Prof. Paper 475—B, p. B117—Bll9. 1964, Fossils in Ordovician tufls, northeast Maine: U.S. Geol. Survey Bull. 1181—E. [In press] Oliver, W. A., 1960, Coral faunas in the Onondaga limestone of New York: U.S. Geol. Survey Prof. Paper 400—B, p. B171— B174. STRUCTURAL GEOLOGY Pavlides, Louis, 1962, Geology and manganese deposits of the Maple and Hovey Mountains area, Aroostook County, Maine: U.S. Geol. Survey Prof. Paper 362, 116 p. 1964, The Hovey Group in northeastern Maine: U.S. Geol. Survey Bull. 1194—B. [In press] Pavlides, Louis, and Canney, F. 0., 1964, Geological and geo- chemical reconnaissance, southern part of the Smyrna Mills quadrangle, Aroostook County, Maine: Art. 140 in U.S. Geol. Survey Prof. Paper 475—D, p. D96—D99. Pavlides, Louis, Neuman, R. B., and Berry, W. B. N., 1961, Age of the “ribbon rock” of Aroostook County, Maine: Art. 30 in U.S. Geol. Survey Prof. Paper 424—B, p. B65—B67. Rankin, D. W., 1960, Paleogeographic implication of deposits of hot ash flows: Internat. Geol. Cong, 2lst, Copenhagen, pt. 12, p. 19—34. Riordon, P. H., 1957, Evidence of a pre-Taconic orogeny in southeastern Quebec: Geol. Soc. America Bull., v. 78, p. 389—394. Toppan, F. W., 1932, The geology of Maine: Schenectady, N. Y., Union College, Dept. Geology, 141 p. White, W. S., 1943, Occurrence of manganese in eastern Aroos- took County, Maine: U.S. Geol. Survey Bull. 940—E, p. 125—461. GEOLOGICAL SURVEY RESEARCH I964 STRATIGRAPHIC IMPORTANCE OF CORALS IN THE REDWALL LIMESTONE, NORTHERN ARIZONA By WILLIAM J. SANDO, Washington, DC. Abstract—Analysis of coral distribution in the Redwall Limstone of northern Arizona indicates that the Horseshoe Mesa Member, highest unit of the formation in Grand Canyon, has been removed by post-Redwall, ‘pre-Pennsylvanian erosion in most of the area south of the Canyon. The Redwall coral faunas suggest an age range from late Kinderhook to early Meramec for the formation. The Redwall is correlated with all but the lowermost part of the Madison Group and with post-Madison Mississippian strata. Recent intensive study of the Redwall Limestone of northern Arizona by a team of investigators lead by E. D. McKee and R. C. Gutschick (report in prepara- tion) has contributed a wealth of information 011 the stratigraphy and paleontology of this familiar but poorly understood formation. McKee (1958, 1960a, 1960b, 19600, 1963) has published several preliminary papers on lithologic subdivisions and sedimentation of the Redwall, and Yochelson (1962) and Sando (1963) have published papers on descriptive paleontology. However, none of the published work deals with recent revisions in the stratigraphy of the formation. The purpose of this report is to present some of the more im— portant biostratigraphic conclusions gained from a study of the Redwall coral faunas. Rugose and tabulate corals, among the more common of the Redwall fossils, have proved to be very helpful in interpreting the stratigraphy of the formation, de- termining its age, and establishing correlations with other stratigraphic units. Many of the stratigraphic interpretations of an earlier paper on the Redwall corals (Easton and Gutschick, 1953) have been revised on the basis of more extensive collections. Approximately a thousand specimens collected from 34 stratigraphic sec— tions measured by McKee and Gutschick (figs. 1 and 2) provided the evidence for new stratigraphic interpre- tations. McKee (1963) has recently given formal member designations to the four lithologic subdivisions of the 114° 112° 110° I l l I S UTAH I -_—_—_———————-——-——_——————_-'——- : ARIZONA VNOZIXV OOIXHN MEN 40 O 40 80 MILES I_I_I_1_.I__;__I FIGURE 1.—Index map of northern Arizona, showing location of coralliferous sections of Redwall Limestone. 1, North Kaibab; 2, Havasu Canyon; 3, Whitmore Wash; 4, Para- shant Canyon; 5, Grand Wash; 6‘, Pakoon; '7, Iceberg Canyon; 8, Quartermaster Canyon; .9, Bridge Canyon; 10, Hindu Canyon; 11, Diamond Creek; 12, Metuck Canyon; 13, Peach Springs-Nelson; 11,, Ring Cone; 15, Seligman Field; 16', Chino Point; 17, Picacho Butte; 18, Black Mesa; 19, Drake quarry; 20, Simmons; 21, Lonesome Valley; 22, Sycamore Canyon; 23, Mingus Pass; 24, Jerome; 25, Clemenceau quarry; 26‘, Natural Bridge; 27, Pine; 28, Colcord Canyon; 29, O. W. Ranch; 30, Brush Mountain; 31, Salt River Draw 1; 32, Salt River Draw 2; 33, Salt River US. 60; 34, Black River Crossing. Redwall that were previously recognized by various geologists. The lowermost unit, the Whitmore Wash Member, rests unconformably on various formations of Devonian age and, locally, on Cambrian strata. It consists of thick-bedded limestone or dolomite or a com- bination of limestone and dolomite. Overlying the Whitmore Wash is the Thunder Springs Member, which consists of a resistant series of alternating lime- stone or dolomite and chert beds which form a con- spicuous banded cliff. The Thunder Springs is suc- ceeded by the Mooney Falls Member, predominantly U.S. GEOL. SURVEY PROF. PAPER 501-0. PAGES 039—042 C39 C40 STRATIGRAPHY AND PALEONTOLOGY FEET EXPLANATION —900 W E E ‘800 Post-Redwall residuum overlying Redwall and filling caves in Mooney Falls Member —700 Horseshoe Mesa Member W W1 AAA-annnnoooool ooooooooouu-u-u- .....". Dorlodotia inconstans zone —600 x x x x Lithostrotilm (Siphonodendro'n) ~5oo Mooney Falls Member “WWW" 2°"e A A A A A Michelimla expanse zone —4OO \ o o o o o // Base of limestone marker bed ~3OO \ . Member In Naco Formation Springs Thunder -200 \ Member 1 \/ Wash —100 Whitmore 3 2 fl l—O MW?) Cl) 1L0 2|O 3.0 4‘0 5‘0 MILES 6 . NW SE Horseshoe Mesa WW:- AEAAAAAAAAAAAAAA Mooney / Thunder Member 22 WV mmmb M112 1314 1516 1“ 19 2° 21 /10 NW SE AAA ‘ Falls Mooney Member Thunder Springs Member Whitmore Wash Member 22 23 24 25 34 FIGURE 2.—Stratigraphic sections of the Redwall Limestone, northern Arizona. Numbers refer to locations shown on figure 1. Overlying rocks are of Pennsylvanian age, and underlying rocks are Devonian. Measured sections by E. D. McKee and R. C. Gutschick. SAN D0 fine- to coarse-grained, largely crinoidal limestone in thick beds which crop out in a massive cliff. The high- est subdivision is the Horseshoe Mesa Member, pre- dominantly thin-bedded, fine-grained limestone, which forms receding ledges overlying the massive Mooney Falls cliff. The top of the Horseshoe Mesa is an ancient karst surface overlain unconformably by beds of Penn- sylvanian age in the Supai and Naco Formations. Biostratigraphic analysis of the coral faunas has a significant bearing on four key stratigraphic problems of the Redwall: (l) recognition of the Mooney Falls- Horseshoe Mesa boundary in the Grand Canyon region, (2) identification of the Redwall members in the various sections studied in northern Arizona, (3) interpretation of the significance of the residuum that overlies and fills caves in the formation in the Mogollon Rim region, and (4) correlation of the Redwall with other forma- tions in the Cordilleran region. The boundary between the Mooney Falls Member and Horseshoe Mesa Member is generally marked by a change from thick-bedded, medium- to coarse-grained limestone below to thin—bedded, fine-grained limestone above. However, these relationships are not every- where consistent because characteristic Horseshoe Mesa rock types commonly occur in the Mooney Falls Member, and Mooney Falls types are known in the Horseshoe Mesa Member at some localities. Consequently, other criteria have been used in some sections to supplement the gross lithologic criteria for placement of the con- tact. Among the more useful supplementary criteria is the position of the Dorlodotz'a imcomtans zone, char— acterized by the occurrence of large dendroid litho- strotionoid corals in cherty limestone within a few feet above or below the contact established on bedding criteria. This zone has been recognized in most of the sections studied in central and western Grand Canyon and has been used as a datum of contemporaneity in erecting the stratigraphic framework in that area (figs. 2, 3). Dorlodotia inconstcms is absent in the Chino Val- ley and Mogollon Rim region, except for its occurrence in residual products overlying the post-Redwall karst surface and in solution cavities within the Mooney Falls Member in the Chino Valley area. This observation is one of the key factors in the recognition that post— Redwall erosion removed all the Horseshoe Mesa Member in most of the area south of the Grand Canyon. The stratigraphic distribution of several coral taxa (fig. 3) has been used to establish relations between the various members of the Redwall in the Grand Canyon and their counterparts in the Chino Valley and Mogol- lon Rim regions south of Grand Canyon. The absence of species of E kvasophyZZu/m and Lithostrotion (Sipho— mdendron), as well as the occurrence of Dorlodotia only in residual deposits, south of Grand Canyon sup- C41 ports the conclusion that the Horseshoe Mesa Member and part of the Mooney Falls Member are not now pres- ent in the Chino Valley and Mogollon Rim. Species of Homalophyllites and Zaphrentites are common in the Redwall below the upper part of the Mooney Falls Member throughout the area studied. Vesiculophyllum incmssatmn, which ranges from the base of the Redwall into the Horseshoe Mesa Member in Grand Cayon, is found in pre—Horseshoe Mesa beds in the Chino Valley and Mogollon Rim. The Michelim'a ewpansa zone, characterized 'by Mi- chelim'a ewpomsa and Lithostmtionella circinatw, pro- vides a convenient marker for linking many of the sections in the Chino Valley. This zone has been traced onto both flanks of the Pine arch, where overlap of the Thunder Springs and Whitmore Wash Members by the Mooney Falls Member has been established on lithic and faunal evidence (sections 26~30, fig. 2). Residual deposits similar in lithology and strati- graphic position to the Molas Formation of Colorado were formed during the karst event that immediately followed Redwall deposition. These deposits overlie the formation and fill eaves within it in the Mogollon Rim region. The residuum contains corals representa- tive of Mooney Falls levels younger than those now present in the bedrock in a given section. The signifi- cance of species of Aulina, also found in the residuum, is difficult to evaluate because the Aulinas are not known from the bedrock and have not been found elsewhere on the North American continent. Inasmuch as the known range of Aulina in Europe and Asia is upper Viséan through lower Namurian, these corals probably repre- sent an interval of Meramec or, possibly, Chester age. With respect to regional correlation, the most impor- tant faunal change relating to corals occurs at the base of the Lithostrotz'on (Siphonodendron) oculinwm. zone in the upper third of the Mooney Falls Member (fig. 3). The coral fauna above this datum includes Siphono- dendron, Dorlodotia, and E kvasophyllum, which are characteristic of Upper Mississippian (early Meramec) strata in the northern Cordilleran region. Siphono- dendron occurs in the uppermost part of the Madison Group (zone D of Sando and Dutro, 1960) in Montana and Wyoming, whereas Dorlodotia and Ekwsophyllmn are found in post-Madison Mississippian limestones in Utah and Idaho. The Redwall Limestone below the zone of Siphonodendron contains an Early Mississip- pian coral fauna characterized by species of Homalo- phyllites, Zaphrentites, Michelim'a, and Lithostrotion- ella. These forms appear to represent upppermost Kinderhook and Osage equivalents and compare with faunas found in zones C1 and 02 of the Madison Group (Sando and Dutro, 1960). C42 PENNSYLVANIAN E Horseshoe 0. Mesa —r I $ Member 3 S _ 3 3 g 1 E 3 T Lu E g S s a 3 § 1 S S T T s “ __ s .3 § s s s s a 3 3 s g * 8 3 ea 3 ‘\ on Fri § Mooney e s Falls E E I I Member ‘°‘ ~53 S, g d s s s g a. ~§ g A .e m g a S 9 VJ —§ no ” E ,8 d g. ”1 53 u « 1: a. N \' § 3 g s w 8 g s s _ m . . n. g. ,3 g ‘3 § .§ In. 3 :3 s L 's :3 — 3 ‘° 3 c (I) § 3 g a) g s e ’3 <7: m t r s <9 g‘ ’3 re 2 N S >. .1 c: 5 Thunder + Springs Member l | | Whitmore l Wash Member I J_ .L'; L‘ DEVONIAN FIGURE 3.—-Generalized columnar sect-ion of Red- wall Limestone, showing composite strati- graphic ranges of important coral taxa in northern Arizona. The interpretations expressed in this article difler significantly from those of Easton and Gutschick (1953). The new interpretations are based mainly on a regional synthesis of many coralliferous sections, in- formation that was largely not available at the time of Easton and Gutschick’s study. The new studies in- dicate that the stratigraphic unit designated as Mem- ber IV by Easton and Gutschick (1953, p. 4, text fig. II) in the area south of Grand Canyon is not the same as the highest unit of the Grand Canyon (now called Horseshoe Mesa Member). On the contrary, the Horse- shoe Mesa Member was removed from most of the area STRATIGRAPHY AND PALEONTOLOGY south of Grand Canyon by post-Redwall, pre-Pennsyl- vanian erosion which produced residual products that filtered down into the Mooney Falls Member via solu- tion cavities and, locally, resulted in mixing of rocks and faunas from several stratigraphic levels. The rec- ognition of mixed faunas, along with revised correla- tion of coralliferous intervals at some localities and discovery of some forms at levels where they were pre- viously unrecognized has resulted in a somewhat dif- ferent picture of stratigraphic ranges for many of the species described by Easton and Gutschick. Although the previous authors specifically confined their remarks on regional correlation to the Jerome re- gion south of Grand Canyon where the uppermost part of the formation is missing (Easton and Gutschick, 1953, p. 8), their study is the principal reference on faunal correlation of the formation and has at least an implied significance as a Redwall standard. For this reason, it is important to point out that the new studies disagree with Easton and Gutschick’s (1953, p. 8) state- ment that “the Redwall is almost all referable to the Kinderhookian Series”. The new evidence suggests that most of the formation is of Osage age (an inter- pretation actually anticipated by Easton and Gutschick in the footnote on page 7 of their paper) and that the age range of the Redwall is from late Kinderhook to early Meramec. REFERENCES Easton, W. H., and Gutschick, R. 0., 1953, Corals from the Redwall Limestone (Mississippian) of Arizona: Southern California Acad. Sci. Bull., v. 52, pt. 1, p. 1—11, 2 figs, 3 pls. McKee, E. D., 1958, The Redwall Limestone, in New Mexico Geol. Soc. Guidebook 9th Ann. Field Cont: p. 74—77, 2 figs. 1960a, Cycles in carbonate rocks: Am. J our. Sci., v. 258—A, p. 230—233, 1 fig. 1960b, Lithologic subdivisions of the Redwall Limestone in northern Arizona—their paleogeographic and economic significance: Art. 110 in U.S. Geol. Survey Prof. Paper 400— B, p. B243—B245. 1960c, Spatial relations of fossils and bedded cherts in the Redwall Limestone, Arizona: Art. 210 in US. Geol. Survey Prof. Paper 400—B, p. B461—B463. 1963, Nomenclature for lithologic subdivisions of the Mississippian Redwall Limestone, Arizona: Art 65 in [1.8. Geol. Survey Prof. Paper 475—0, p. 021—022. Sando, W. J ., 1963, New species of colonial rugose corals from the Mississippian of northern Arizona: Jour. Paleontology, v. 37, no. 5, p. 1074—1079, pls. 145—146, 1 text fig. Sande, W. J ., and Dutro, J. T., Jr., 1960, Stratigraphy and coral zonation of the Madison Group and Brazer dolomite in northeastern Utah, western Wyoming, and southwestern Montana, in Wyoming Geol. Assoc. Guidebook 15th Ann. Field Conf. 2 p. 117—126, 3 figs, 1 p1. Yochelson, E. L., 1962, Gastropods from the Redwall Lime- stone (Mississippian) in Arizona: Jour. Paleontology, v. 36, no. 1, p. 74—80, pl. 17. 6% GEOLOGICAL SURVEY RESEARCH I964 YOUNGER PRECAMBRIAN FORMATIONS AND THE BOLSAI?) QUARTZITE OF CAMBRIAN AGE, PAPAGO INDIAN RESERVATION, ARIZONA By L. A. HEINDL and NEAL E. McCLYMONDS, Arlington, Va., San Juan, P.R. Work done in cooperation with the U.S. Bureau of Indian Again Abstract—The Apache Group of younger Precambrian age crops out in 1,500-foot sequences in the Vekol and Slate Moun- tains. An overlying elastic unit, heretofore referred to the Troy Quartzite, is correlated tentatively with the recently re- defined Bolsa Quartzite of Cambrian age. This elastic unit is here designated the Bolsa( ‘2) Quartzite. It is also exposed in the Waterman Mountains where, however, it rests on granitic rocks. It is overlain conformably by the Abrigo Formation of Cambrian age in the three mountain ranges. Younger Precambrian and Paleozoic sedimentary rocks crop out in the Vekol, Slate, and Waterman Mountains in the northeastern part of the Papago In- dian Reservation of south-central Arizona (figs. 1 and 2). These outcrops include the westernmost known exposures of the Apache Group of Younger Precam- brian age. Also included is a elastic unit between the Apaphe Group and the Abrigo Formation of Cambrian age which could be correlated with either the Troy Quartzite of Precambrian age or the Bolsa Quartzite of Cambrian age. Evidence presented herein (p. C48) indicates strongly, though not conclusively, that the elastic unit is of Cambrian age; here the unit is cor- related tentatively with the Bolsa and is thus designated Bolsa( ?) Quartzite. The areas where these rocks crop out are shown on geologic maps prepared by Darton and others (1924), Wilson and Moore (1959), and Wilson and others (1960), and partial sections have been described briefly by Darton (1925) and Hadley (1944). These rocks are described in detail in unpublished theses by W. G. Hogue, R. H. Carpenter, A. W. Rufl', N. E. McCly- monds, and D. F. Hammer.1 Brief descriptions of the 110:_ 36' Colorado Plateaus ‘ \\ structural province I \\ A R I Z O N A \\ . _ l Basm and- \ I Range \\ 34° \ structu ral province \ \ \ I .‘Globe-MiamiI area 0 PHOENIX River .IJ'] Area of Am JJ'TI i/report \\ , J\ 7 FEM": oTucson 32° e\ _ Indian. ' _ “Eervation . ‘4 C oBisbee : \—— _ O 50 100 MILES FIGURE 1.—Map showing area of report in relation to the structural provinces and larger population centers in Arizona. Precambrian and Paleozoic sedimentary rocks by Mc- Clymonds (1959a, 1959b) were concerned mainly with correlation of the Paleozoic sequences. xW. G. Hogue, 1940, Geology of the northern part of the Slate Mountains, Pinal County, Ariz.: Arizona Univ., M.A. thesis. R. H. Carpenter, 1947, The geology and ore deposits of the Vekol Mountains, Pinal County, Ariz.: Stanford Univ., Ph. D. thesis. A. W. Rum, 1951, The geology and ore deposits of the Indiana mine area, Pima County, Ariz.: Arizona Univ., M.A. thesis. N. E. McClymonds, 1957. Stratigraphy and structure of the Water- man Mountains, lea County, Ariz.: Arizona Univ., M.A. thesis. D. F. Hammer, 1961, Geology and ore deposits of the Jackrabbit area, Pinal County, Ariz.: Arizona Univ., M.A. thesis. U.S. GEOL. SURVEY PROF. PAPER 501-0. PAGES C43-C49 732-760 0—64—4 C43 C44 do i _ :|b EXPLANATION , ; §ii Ci ‘ 5 5% Alluvium EC T._‘_j ' j 9 . S, l- j Bedrock I . TIES. in «"A ISO F 7.? Generalized line of _A’H _ _i ’ ___£I2\I.ALCO measured section 32°30'— - ’0 :1 . PIMA (‘0 — T. 4:) / Q «I 151 5 , , 0° .H R 7 E ' I 5» Waterman T 354! g 'l" \ i :‘ | Mts T ' R 6 E . - at??? _ .—T_l (x) Egg-é’iétv 12 S. "Q > QCUO C.P"K S. ' e ’/ 0 CD (7%,? T [[ i \ /\ \ o i. T. 13 u, z\ 0 " P: 13 S F . ' r l . \ 0 not 5 RAE R5E RGE R7E. R.8E 0 5 10 15 MILES L.‘_l_|_l_;__l.__.l FIGURE 2.—Map showing location of the measured sections of the Apache Group and Bolsa( ?) Quartzite in the Vekol (A), Slate (B), and Waterman (0) Mountains, Papago Indian Reservation, Ariz. A review of the literature on Precambrian and Cam- brian rocks in southern Arizona reveals considerable uncertainty about the age and correlation of the clastic rocks older than the Abrigo Formation and younger than the Mescal Limestone of the Apache Group. As originally described by Ransome (1903), the Apache Group in the Globe-Miami area consisted, in ascending order, of the Scanlan Conglomerate, Pioneer Shale, Barnes Conglomerate, and Dripping Spring Quartzite, and was tentatively considered to be of Cambrian age. On the basis of later work, Ransome (1915) added the Mescal Limestone, local basalt flows immediately over- lying the Mescal, and the Troy Quartzite to the upper part of the Apache Group. Previously, Ransome (1904) also had described the Bolsa Quartzite and Ab- rigo Limestone, both of Cambrian age, but could not determine whether they were younger than or partly of the same age as the Apache Group. Darton (1932) concluded that the Troy Quartzite should be excluded from the Apache Group, and he assigned the Troy to the Cambrian. Thus, the elastic rocks underlying the Abrigo For— mation in southern Arizona were assigned to either the Troy Quartzite or the Bolsa Quartzite—two strati- graphic units whose relations and definition were not clear. For many years, general practice has been to apply the term Troy to quartzite that overlaps the Apache Group, and the term Bolsa to quartzite that overlaps older Precambrian schist and granitic rocks (Dickinson, 1959). This usage, however, was not con- sistent. All previous reports on the Papago Indian STRATIGRAPHY AND PALEONTOLOGY North South .é'g' . {1‘ gm- "’ (I) é; LE EA EA :3?) 20A 122 an» 0': Eg‘” :9 ‘53 25 m" 3“ :5 E .L“ m o“ s. w EKH m 0,, ME I_.. 2w 2 En MM —5 2 L; gs; 3: fig %-5 _vv—< 0) _ o > (I) 313 Abrigo Formation Troy Quartzite v‘f— “ A Bolsa(? uartzite f / / .Jg;j ,// Older Precambrian l w schist and granite FIGURE 3.-—Synoptic diagram showing relations of the Apache Group, Troy Quartzite, and diabase sills and intrusions (shaded) of younger Precambrian age and Bolsa( ?) Quartzite and Abrigo Formation of Cambrian age. Not to scale. Reservation referred the elastic unit immediately be-. neath the Abrigo to the Troy Quartzite of Cambrian age, regardless of whether the underlying rocks were sedimentary rocks of the Apache Group or Precam- brian granite. Work by Shride (1958) indicated that the Troy should be reincluded in the Apache Group and re- assigned to the Precambrian. Krieger (1961) report- ed the Troy and Bolsa Quartzites in contact, and dis- tinguished the Troy and Bolsa on (a) the basis of color, composition, and bedding, (b) the presence of diabase sills in the Troy, and (c) the fact that the Bolsa locally rests on an eroded surface cut on diabase that intrudes the Troy (fig. 3). Although the Troy and Bolsa are virtually concordant, they are separated by a consider- able hiatus. Peterson (1962) accepted the Precambrian age for the Troy but did not consider it a part of the Apache Group; his conclusion is the currently accepted status of the Troy. ‘ The original formations of the Apache Group have also been redefined. H. C. Granger and R. B. Raup (written communication, April 16, 1962) consider the Barnes Conglomerate to be a basal member of the Dripping Spring Quartzite, and C. R. Willden (written communication, May 22, 1962) considers the Scanlan Conglomerate to be a bed within the Pioneer Forma- tion. As the beds of conglomerate within the Apache Group, where exposed on the Papago Indian Reserva- tion, are thin and discontinuous, and lenses of conglom— erate similar to the Barnes occur at several horizons near the base of the Dripping Spring Quartzite, the proposed reduction of the Barnes and Scanlan from formational rank seems reasonable, and the Apache HEINDL AND MCCLYMONDS Group consists, therefore, of the Pioneer Formation, Dripping Spring Quartzite, and Mescal Limestone. On the Papago Indian Reservation, the Apache Group, the Bolsa( ?) Quartzite, and the Abrigo For- mation are well exposed in the Vekol and Slate Moun- tains. The Apache Group rocks are similar to the type sequence in the Globe—Miami area; although the formations composing the Apache Group differ in thick- ness, their combined thickness and the sequence of rock types are nearly the same as in the type area (see accom- panying table). The Apache Group is missing in the Waterman Mountains, but the Bolsa(?) and Abrigo are exposed; here the Bolsa(?) rests unconformably on Precambrian granite. The following measured sec- tions are representative of the Apache Group and Bolsa( ?) Quartzite on the reservation. Thicknesses, in feet, of the Pioneer Formation, Drip ing Spring Quartzite, and Mescal Limestone of the Apache roupan the Vekol and Slate Mountains and in the Globe-Miami area, Arizona Globe- Vekol Mountains Slate Mountains Miami area Unit McCly- McCly- After Carpen- monds Haguel Ham- monds Peterson ter 1 (this mer I (this (1962) article) article) Mescal Limestone_- 291 345' 240 193 235 360 Dripping Spring Quartzite _______ 2 700 825 850 1, 179 975 840 Pioneer Formation- 3 400 350 450 374 440 300 Total (Apache Group) _____ 2 1, 390 1, 520 1, 540 2 1, 750 1, 650 1, 500 1 See footnote, p. C43. 1 Estimated or rounded thickness. Vekol Mountain Section Generalized stratigraphic section of the Pioneer Formation, Dripping Spring Quartzite, and Mescal Limestone of the Apache Group of younger Precambrian age, and the Bolsa (t) Quartz- ite of Cambrian age in the Vekol Mountains, Pinal County, Arie. (Based on composite sections: Pioneer Formation and basal Dripping Spring Quartzite measured in W1/2SW174 sec. 6, T. 10 S., R. 3 E.; Dripping Spring Quartzite and Mescal Limestone measured in SEyQSEIA sec. 1, T. 10 S., R. 2 E.; and Bolsa(?) Quartzite and lowest unit of Abrigo Formation measured in SEIANWJA sec. 1, T. 10 S., R. 2 E.) Gambrian Thickness Abrigo Formation (lowest unit) : (feet) Sandstone, light-brown, light-gray to pale-red, very fine grained, partly dolomitic; weathers blocky; interbedded with platy, locally fossili- ferous light-brown to grayish—red silty dolo- mite; unit forms steplike slope; base sharp and flat. (Note: Carpenter 2 included this unit in uppermost part of his Troy Quartzite) _____ 44 “See footnote, p. C43. C45 Cambrian—Continued Bolsa( ?) Quartzite: (feet) Quartzite, light-gray to brownish-gray, fine- grained; crossbedded; partly dolomitic; frag- ments of small fossils; weathers blocky, inter- bedded with light—gray mudstone near middle and with medium-grained sandstone in lower third ; forms cliflf with steplike slope in middle third ; base sharp and flat ____________________ 76 Erosional surface( '3) Quartzite, light-gray to light—brown to light-red; fine to medium grained; granule-sized particles near base; partly calcareous; partly cross- bedded; weathers blocky; small fragments of fossils in upper part; forms cliif; 5-foot slope- forming, fine- to coarse-grained, light-gray to dark-red sandstone bed near base; base cov- ered Total Bolsa( ?) Quartzite _________________ Unconformity Precambrian Basalt flows, black, vesicular; as much as 50 feet thick, but locally absent ________________________ Apache Group : Mescal Limestone (not including diabase sills) : Dolomite, light- to dark-gray, partly brownish- gray, partly red; aphanitic; silty; weathers blocky; gray and red chert in nodules and thin stringers; light-gray chert beds in lower half; forms ledge-shelf slope in upper half of 78-foot clifl below middle and steplike slope near base; base flat, grades into underlying units ....... Limestone, light-gray to light-greenish-gray; aphanitic; weathers blocky; gray chert and siliceous limestone in nodules, thin stringers, and thin beds; flat-pebble congomerate 44 feet above base; unit forms cliflF, sloping near base; sharp and undulating _______________________ 59 Mudstone, dark-yellowish-green to dark-gray; slightly calcareous; partly siliceous; weathers blocky to platy; forms weak steplike slope; base sharp and flat _________________________ 41 Siltstone, dark-yellowish—green; weathers blocky to platy; 3-foot, gray to dark-yellowish-brown, finely crystalline, silty dolomite ledge at top; unit forms steplike slope; base sharp and flat“ 10 Thickness 124 200 235 Total Mescal Limestone __________________ Dripping Spring Quartzite (not including diabase sills) : Upper member: Quartzite, light- to dark-gray, partly greenish- gray, partly brownish-gray; silty to coarse grained; partly arkosic; partly crossbedded; weathers blocky; slope-forming, platy-weath- ering, gray siltstone in 14ofoot-thick bed 35 feet above base; upper 41 feet forms sloping cliff, lower 35 feet forms cliff; base sharp and flat__ 90 Siltstone, light-gray to greenish-gray, partly brownish-gray; weathers blocky; lightobrown— ish-gray, fine-grained, partly arkosic quartzite in 1- to 3-foot beds in upper part; upper 54 feet forms cliff, lower 39 feet forms slope; base sharp, in contact with diabase intrusion (sill)- 93 345 STRATIGRAPHY AND PALEONTOLOGY Precambrian—Continued Apache Group—Continued Dripping Spring Quartzite—Continued Upper member—Continued Mudstone, light-greenish-gray to dark-yellowish- green; weathers platy to soft; interbedded with ledge-forming, blocky-weathering, green- ish-gray siltstone in upper 48 feet and lower 50 feet ; interbedded with ledge—forming, blocky- weathering, light- to dark-gray to brownish- gray quartzite in middle 145 feet; unit forms slope, covered in 52-foot layer 50 feet above base; base sharp and flat ____________________ Silstone, grayish-green to dark-yellowish-brown; red in basal 30 feet; partly crossbedded; weathers platy to blocky; interbedded with slope-forming, greenish-gray to light-orange mudstone in middle part; unit forms weak steplike slope; base sharp and slightly undu- lating _ Thickness (feet) 295 117 Total upper member ______________________ Middle member : Quartzite, light-gray to brownish-gray; partly red near top; fine to medium grained; partly arkosic, partly calcareous; crossbedded; weathers blocky; ripple marks and rain-drop impressions at top of some beds near top; forms cliff and dip slopes; base covered ____________ Quartzite, light-brown to light-gray ; partly green- ish gray; fine to coarse grained; partly ark- osic, partly calcareous; weathers blocky; forms slope, covered at top and bottom, 13-foot sloping cliff 7 feet above base; base covered___ 595 170 36 Total middle member _____________________ Barnes Conglomerate Member : Conglomeratic quartzite, light-gray to brownish- gray to red; fine-grained to very coarse grained matrix; arkosic; partly calcareous; weathers blocky to massive; granule- to cob- ble-sized, rounded quartz and red chert frag- ments; forms sloping cliff; base sharp and undulating _________________________________ 206 24 Barnes Conglomerate Member _____________ Total Dripping Spring Quartzite __________ Pioneer Formation (not including diabase sills) : Siltstone, greenish-gray to reddish-purple; clay- ey near top to sandy near base; partly cross- bedded; weathers massive, partly blocky; forms slope, some ledges near middle; base sharp and flat _____________________________ Siltstone, purplish-gray; weathers massive; in- terbedded with grayish-purple and yellowish- gray quartzite; fine-grained; partly arkosic, arkosic ledge at top; weathers blocky; unit forms slope with ledges; base grades into un- derlying unit _______________________________ Siltstone, grayish- to reddish-purple with green spots; weathers massive; slope-forming, gray and purple mudstone with green spots in 12- foot bed at top; ledge-forming, blocky-weather- 24 825 175 97 Precambrian—Continued Apache Group—Continued . Pioneer Formation—Continued “29°35” ing, fine-grained, gray to brownish-gray quartz~ ite in thin beds and lenses; unit forms slope. Conglomerate in l-foot lens at base, greenish- to brownish-gray; fine—grained matrix; pebbleL sized, white quartz fragments; forms weak ledge; base sharp and slightly undulating____ 78 Total Pioneer Formation __________________ 350 Unconformity Pinal Schist Slate Mountains Section Generalized stratigraphic section of the Pioneer Formation, Dripping Spring Quartzite, and M escal Limestone of the Apache Group of younger Precambrian age and the Bolsa( ?) Quartzite of Cambrian age in the Slate Mountains, Pinal County, Arie. (Based on composite section: Pioneer Formation and Barnes Conglomerate Member of Dripping Spring Quartzite measured in N1/2 sec. ’7, T. 10 8., R. 5 E.; Middle and upper members of Dripping Spring Quartzite and lower part of Mescal Limestone measured in SWIASWIA see. 6, T. 10, 8., R. 5 E.; and upper part of Mescal Limestone and Bolsa(?) Quartzite measured new middle 8E$4 sec. 1, T. 10 8., R. 4 E.) Cambrian . Abrigo Formation (lowest unit) : ”2323,27?“ Quartzite, light-gray to brownish-gray; very fine grained; crossbedded; partly calcareous; weathers platy to blocky; interbedded with fissile- to platy-weathering, light-greenish-gray mudstone; worm-burrow molds; unit forms steplike slope; base covered __________________ 104 Bolsa(?) Quartzite: Quartzite, gray, partly reddish-brown, partly purple to pink; fine grained, some granule- sized particles; mostly arkosic, some glauco- nite; partly crossbedded; weathers blocky; forms cliff; base sharp and flat ______________ 115 Sandstone, light-brown to pink, partly reddish- brown, partly gray; fine grained, some coarse— grained particles; grades laterally to quartzite; some quartzite beds; partly crossbedded; weathers blocky to soft; forms steplike slope; base sharp and flat __________________________ 218 Sandstone, light-red to reddish-brown; fine to coarse grained; silty; partly crossbedded; weathers blocky to soft; forms slope with weak ledges; base sharp and slightly undulating__ 82 Total Bolsa(?) Quartzite _______________ 415 Disconformity Precambrian Apache Group: Mescal Limestone (not including diabase sills) : Dolomite, dark-gray, partly grayish-red or brown- ish-gray; very finely crystalline; partly silty; weathers blocky; light-gray chert in nodules and thin bands; forms steplike slope; base cov- ered ..... - 128 HEINDL AND Precambrian—Continued Apache Group—Continued _ Mescal Limestone—Continued “2'19;ng Limestone, gray, partly brownish-gray ; very fine- ly crystalline; partly silty; weathers blocky; light-gray to pale-red chert in nodules and thin bands; forms steplike slope; base sharp and flat-_ _____ ___ _____ 49 Dolomite, .dark-yellowish-brown; very finely crys- talline; weathers blocky; light-gray to yellow- ish-brown chert in thin bands and beds; forms steplike slope; base covered _________________ 23 Siltstone, reddish-brown to yellowish-brown; weathers massive; limestone in thin bands in upper part; chert in lower part; forms slope; base sharp and slightly undulating-___ 35 Total Mescal Limestone ___________________ 235 Dripping Spring Quartzite (not including diabase sills) : Upper member: Quartzite, gray, partly grayish-red or greenish- gray; fine grained; arkosic; partly calcar- eous; partly crossbedded; weathers blocky; interbedded with slope-forming, fissile weath- ering, olive to gray to red mudstone; unit forms steplike slope; base covered ____________ 61 Mudstone, red to dark-reddish-brown, weathers blocky to fissile; interbedded with ledge forming, platy-weathering, gray, red, and greenish-gray siltstone; unit forms slope; base covered _______________________________ Quartzite, gray, partly reddish-brown; very fine to medium grained; partly arkosic; partly crossbedded; weathers blocky; forms step- like slope; base grades into underlying unit-- 74 Mudstone, gray and reddish-brown, partly green- ish-gray; weathers fissile, partly soft; inter- bedded with ledge-forming, blocky-weathering, gray siltstone ; unit forms slope; base covered-- Siltstone, dark-greenish-gray, partly reddish- brown; weathers blocky; interbedded with ledge-forming, blocky—weathering crossbedded, fine- to coarse—grained, gray (partly with green- ish hue) and reddish-brown quartzite; unit forms slope with weak ledges; base sharp and flat ________________________________________ 88 Sandstone, dark-red; very fine grained; muddy; weathers blocky; forms slope; base sharp and flat _ _-__ 75 116 114 Total upper member ____________________ 528 Middle member : Quartzite, pinkish-gray to red; very fine to me— dium grained; arkosic; partly calcareous in lower half; partly crossbedded; weathers blocky; ripple marks at top of some beds; forms cliff and dip slope; base sharp and flat-- Quartzite, light-gray to pale-red; fine grained; arkosic; partly crossbedded; weathers blocky; granule- to pebble-sized quartzite fragments in lower half; forms cliff; base sharp and flat_- 35 367 Total middle member ___________________ 402 McCLYMONDS C47 Precambrian—Continued Apache Group—Continued Dripping Spring Quartzite—Continued Barnes Conglomerate Member: Conglomeratic quartzite, light-gray to pink; very fine grained to coarse-grained matrix; arkosic; partly crossbedded; weathers blocky; granule- to pebble-sized quartzite fragments in beds as much as 4 feet thick; forms cliff; base sharp and slightly undulating ____________________ 45 Thickness (feet) Total Barnes Conglomerate Member ______ 45 Total Dripping Spring Quartzite _________ 975 Pioneer Formation (not including diabase sills) : Mudstone, reddish-purple to purple; weathers massive to fissile; interbedded with ledge-form- ing, platy— to blocky-weathering, greenish-gray, partly brownish-gray, siltstone; unit forms steplike slope; base sharp and flat ___________ 84 Quartzite, gray, brownish-gray, or greenish-gray; very fine to medium grained; arkosic; partly . crossbedded; weathers blocky; forms steplike slope; base covered _________________________ 46 Mudstone, dark-reddish-brown with light-green spots; weathers massive, partly soft; inter- bedded with ledgeforming, blocky—weathering, partly crossbedded, fine—grained, red, purple, and light-brown quartzite; unit forms slope with few ledges; base covered _______________ 310 Total Pioneer Formation ________________ 440 Unconformity Pinal Schist Waterman Mountains Section Generalized stratigraphic section of the Bolsa(!) Qaartzite of Cambrian age in the Waterman Mountains, Pima County, Arie. (Based on composite section measured in N W14 sec. 36, T. 12 8., R. 8 E.) Cambrian Thickness Abrigo Formation (lowest unit) : (feet) Mudstone, yellowish-brown; very silty, micaceous, and partly sandy; weathers massive; interbedded with ledge-forming, blocky-weathering, very fine to very coarse grained, yellowish-brown to reddish- brown sandstone; unit forms slope with few ledges; base sharp and slightly undulating ______________ 37 Bolsa( ?) Quartzite: Sandstone, light—red, partly brownish-gray; fine to coarse grained; partly crossbedded; weathers blocky; forms cliff; base grades into underlying unit _______________ ___ 32 Quartzite, light-gray to pink; fine grained, some gran- ule-sized particles; crossbedded; weathers blocky; forms cliif; base sharp and slightly undulating--- 134 Quartzite, light-gray to light-red; fine grained, some granule-sized particles in bands; crossbedded; weathers blocky ; forms sloping cliflf; base covered- 54 Total Bolsa( ?) Quartzite ------------------- 220 Unconformity Precambrian granite C48 In the Vekol Mountains, the Apache Group includes the Pioneer Formation, the Dripping Spring Quartzite, the Mescal Limestone, and local flows of black basalt. All formations of the Apache have been intruded by diabase sills. The Apache Group is overlain discon- formably by the Bolsa(?) Quartzite, which consists mostly of quartzite and sandstone, and the Bolsa( ?) in turn is overlain conform-ably by the A‘brigo Formation. The section in the Slate Mountains is similar to that of the Vekols, except that the Mescal is thinner, the basalt is absent, and the Bolsa( ?) is thicker. In the Waterman Mountains, the Bolsa( ?) is similar to the equivalent rocks in the Vekols. Rocks assignable to the redefined Troy Quartzite of younger Precambrian age have not been recognized at the localities described in this article, although some may be present in the Vekol Mountains (as discussed in a following paragraph). The Bolsa(?) Qu-artzite in the Vekol, Slate,a and Waterman Mountains contains fragments of fossils, generally poorly preserved brachiopods, and worm bor- ings. In each of the three areas, the unit is conform— able with the overlying Abrigo Formation and rests unconformably on either rocks of the Apache Group or Precambrian granite. The fossils and the basal un- conformity are regarded as sufficient evidence for as- signment of a Cambrian, rather than a Precambrian, age to the clastic unit, and except in the Vekol Moun- tains, as discussed in the following paragraph, no contrary evidence is reported. In the Vekol Mountains, however, Carpenter 4 found that the lower part of his Troy Quartzite—the Bolsa( ?) of this report—is intruded by diabase, presumably of Precambrian age, and some question may remain re- garding the age of the beds assigned to the Bolsa( ?) in that area. Along the line of the measured section, the contact between the diabase and the overlying clastic unit is covered, and whether the diabase was intruded along the contact between Precambrian rocks and the clastic unit or whether the elastic unit rests on an eroded surface of the diabase is not clear. However, the dia- base thins from about 200 to 20 feet within a few hun- dred feet near the measured section, and an eroded surface seems to be a more likely explanation than a rapidly thinning sill. Furthermore, small fragments of unidentified fossils in the uppermost 23-foot quartzite below the Abrigo certainly indicate that the quartzite is Cambrian rather than Precambrian. However, Carpenter 4 reports, without specifying the exact place, that “Diabase . . . penetrates the . . .. Troy to within a few feet of the shale zone that separates the . . . massive cliff-forming Troy from the . . crossbedded 3W. G. Hogue; see footnote, p. C43. 4See footnote, p. C43. STRATIGRAPHY AND PALEONTOLOGY fossiliferous member [the lowest unit of the Abrigo Formation of this report].” This observation by Carpenter obviously suggests a prediabase age—that is, Precambrian rather than Cambrian—for the elastic beds. It may be that both the Precambrian Troy and the Cambrian Bolsa( ?) are present in the Vekol Moun- tains; however, because fossil fragments occur in so much of the unit, because we saw no diabase actually intruding the quartzite during our reconnaissance of the range or where we measured the sections, because no unconformity was recognized within those beds or be- tween them and the overlying Abrigo Formation, and because the unit lies disconformably on basalt and the Mescal limestone, we consider the measured sections of the clastic unit below the Abrigo Formation in the Vekol Mountains to be of Cambrian age. The Bolsa( ’9) Quartzite is about 200 feet thick in the Vekol Mountains, about 415 feet thick in the Slate Mountains, and about 220 feet thick in the Waterman Mountains. The upper 333 feet of the atypically thick section in the Slate Mountains is similar to the Bolsa( '9) of the Waterman and Vekol Mountains, but the lower 82 feet is a pale-red to reddish-brown silty sandstone which was not seen in the other two ranges. Further- more, the silty sandstone is not present everywhere in the Slate Mountains—the section measured by D. F. Hammer 5, which is about 130 feet thicker (463 feet) than that reported here, does not include the lower red sandstone. If the basal red sandstone in the Slate Mountains is excluded, the differences in thickness of the Bolsa( '9) in the three mountain ranges probably reflect deposition on a surface of low relief. A. W. Ruff 5 re- ports t‘hat the Bolsa(?) and Troy Quartzites in his area are 185 feet thick in the south-central part of the Waterman Mountains and only 95 feet thick 2 miles away at the northwestern end. Although much of the difference in thickness undoubtedly is due to relief on the Precambrian surface, some may be due to faulting, including thrusting, which is common. Locally the con- tact between the elastic unit and the underlying granite in the Waterman Mountains shows evidence of move- ment. REFERENCES Darton, N. 1-1., and others, 1924, Geologic map of the State of Arizona : Arizona Bur. Mines, scale 1 2 500,000. Darton, N. H., 1925, A résumé of Arizona geology: Arizona Bur. Mines Bull. 119, 298 p. 1932, Algonkian strata of Arizona and western Texas [abs] : Washington Acad. Sci. Jour., v. 22, n. 11, p. 319. Dickinson, R. G., 1959, Cambrian and Ordovician systems in southeastern Arizona, in Arizona Geological Society Guide- book II: Arizona Geol. Soc. Digest. 2d ann., p. 21—24. “See footnote, 1). C43. HE INDL AND MCCLlflMONDS Hadley, J. B., 1944, Copper and zinc deposits in the Reward area, Casa Grande mining district, Pinal County, Ariz.: U.S. Geol. Survey Strategic Minerals Inv. Krieger, M. H., 1961, Troy Quartzite (Younger Precambrian) and Bolsa and Abrigo Formations (Cambrian), Northern Galiuro Mountains, southeastern Arizona: Art. 207 in US. Geol. Survey Prof. Paper 424—0, p. 0160—0164. McClymonds, N. E., 1959a, Paleozoic stratigraphy of the Water- man Mountains, Pima County, Ariz., in Arizona Geological Society Guidebook II: Arizona Geol. Soc. Digest, 2d ann., p. 66—76. 1959b, Precambrian and Paleozoic sedimentary rocks of the Papago Indian Reservation, Ariz., in Arizona Geologi- cal Society Guidebook II: Arizona Geol. Soc. Digest, 2d ann., p. 77—84. Peterson, N. P., 1962, Geology and ore deposits of the Globe- Miami district, Gila and Final Counties, Arizona : U.S. Geol. Survey Prof. Paper 342, 151 p. ’X C49 Ransome, lF' L., 1903, Geology of the Globe copper district, Ari- z 11a : ‘U.S. Geol. Survey Prof. Paper 12, 168 p. 1904, Geology and ore deposits of the Bisbee quadrangle, Arizona: US. Geol. Survey Prof. Paper 21, 168 p. 1915, Paleozoic section of the Ray quadrangle, Arizona: Washington Acad. Sci. Jour., v. 5, p. 380—388. 1919, The copper deposits of Ray and Miami, Arizona: US. Geol. Survey Prof. Paper 115, 192 p. Shride, A. F., 1958, Younger Precambrian geology in southeast- ern Arizona [abs]: Geol. Soc. America Bull., v. 69, no. 12, pt. 2, p. 1744. Wilson, E,‘ D., and Moore, R. T., 1959, Geologic map of Final COunty, Arizona : Arizona Bur. Mines, scale 1 £75,000. Wilson, E. D., and Moore, R. T., and O’Haire, R. T., 1960, Geo- logic map of Pima and Santa Cruz Counties, Arizona: Arizona Bur. Mines, scale 1 :375,000. GEOLOGICAL SURVEY RESEARCH 1964 OCCURRENCE AND PALEOGEOGRAPHIC SIGNIFICANCE OF THE MAYWOOD FORMATION OF LATE DEVONIAN AGE IN THE GALLATIN RANGE, SOUTHWESTERN MONTANA By CHARLES A. SANDBERG and WILLIAM J. McMANNIS,l Denver, Colo., Bozeman, Mont. Abstract—A channel-fill deposit of the generally marine May- wood Formation contains abundant Bothriolepis sp. flsh re- mains and probably was deposited in brackish or fresh water of a bay or estuary. Related Upper Devonian deposits are present in southern Montana and northern Wyoming. They are closely associated with lithogenetically similar Lower Devonian de- posits. Valleys previously inundated by an Early Devonian sea may have controlled and localized transgressions of the Late Devonian sea. OCCURRENCE IN THE GALLATIN RANGE A sequence of yellowish-gray very silty dolomite in— terbedded with yellowish-brown dolomite, containing abundant well-preserved large fish plates of Botkm'o- lepz's sp., crops out about 378 mile north of the Squaw Creek Ranger Station on the west side of the Gallatin Range in southwestern Montana (fig. 1). Visible from US. Highway 191, this sequence forms an almost con- tinuous 1,000-foot-long exposure overlying a north— west-trending cliff of Cambrian rocks 900 feet above the Gallatin River. Fish remains are most abundant at the south end of the outcrop in SW%NE%NW%c sec. 28, T. 4 S., R. 4 E., Gallatin County, Mont. The fossil—fish locality was discovered in the spring of 1961 by Mc- Mannis, who assisted the senior author in making a large collection a few months later. The fish-bearing sequence was assigned tentatively to the Maywood( ?) Formation by McMannis (1962). The marked similarity between the sequence and a measured section of the Maywood Formation at Milligan Canyon (fig. 2), 35 miles to the northwest, and the recent de- termination of the fish remains as Bothmfiolepz’s sp. by D. H. Dunkle now permit positive assignment of the Squaw Creek sequence to the Maywood Formation of 1 Montana State College. 111° 7 .Livingston BEARTOOTH MOUNTAINS 45° MONTANA WYOMING O 10 20 MILES I_._I__l FIGURE 1.—Index map showing approximate southern limit of Maywood Formation (hachured line) and distribution of pre- Devonian rocks during Maywood deposition. Rocks directly underlying Devonian rocks are Bighorn Dolomite of Late Ordovician age (unshaded) and rocks of Late Cambrian age (shaded). early Late Devonian age. The presence of Bothm'olep/is sp. suggests, however, that the Maywood of the Gallatin Range was deposited in marginal-marine brackish or fresh waters, whereas most known occurrences of the Maywood in the Logan area and farther north in Mon- tana represent deposition in shallow, open, or slightly restricted marine waters. U.S. GEOL. SURVEY PROF. PAPER 501-C. PAGES 050—C54 C50 SANDBERG AND McMiANNIs M lLLIGAN CANYON SQUAW CREEK RANGER STATION \ _.\ 6—“ 35 Miles Jefferson Formation a Upper unit Formation / / Maywood Red Lion Formation Pilgrim ‘ Limestone EXPLANATION LI [Dill] Dolomitic siltstone, yeI‘ Dolomitic lirnestone lowish~gray, and re- E3 Marine fossils lated silty carbonate - r—ij rocks Shale Fish plates E E... Dolomite 0 o ' Pebbles FIGURE 2.—Correlation of measured sections of Maywood For- mation and adjacent rocks at Squaw Creek Ranger Station and Milligan Canyon, Mont. At the fossil-fish locality and for about 600 feet to the north, the Maywood Formation rests unconformably on dolomite of the Pilgrim Limestone of Late Cam- brian age along an irregular erosion surface displaying channels and solution crevices as much as 3 feet deep (McMannis, 1962, fig. 7). A wedge of greenish—gray shale of the Red Lion Formation of Late Cambrian age intervenes between the Maywood and Pilgrim farther north along the outcrop; the thickness of the shale in- creases to about 12 feet at the north end (fig. 2). The Maywood Formation, which generally is con— formably overlain by the Jefferson Formation, also of early Late Devonian age, was stated to be 61 feet thick at the Squaw Creek‘ Ranger Station by McMannis (1962). However, correlation of this section with the bottom two units of the type section of the J efl'erson C51 (Sandberg, 1962) at Logan, Mont., demonstrates that 27 feet of beds preferably assignable to the Jefferson was inadvertently included in the Maywood. Thus the Maywood actually has a maximum thickness of about 34 feet, at the south end of the outcrop. The entire exposure near the Squaw Creek Ranger Station probably represents part of a wide, shallow channel-fill deposit. This is inferred from a slight northward thinning of the sequence and a correspond- ing lenticularity of the individual beds, as determined by a series of measured sections, and from the lithologic character of the rocks, as demonstrated by the follow— ing detailed section, measured at the fossil-fish locality: Measured section of the Maywood Formation, % mile north of the Squaw Creek Ranger Station, in SWIANEVL NW14 sec. 28, T. 4 S., R. 4 E., Gallatin County, Mont. Measured by 0. A. Sandberg and W. S. Alvarez. Thickness Maywood Formation: (feet) Dolomite, calcitic, very silty, yellowish-gray, pale-yel- lowish-orange, and grayish-yellow, microcrystalline. Interbedded with argillaceous dolomite. Contains scattered subangular granules and grains of chert. Weathers yellowish gray; thin bedded to platy ; forms reentrant ________________________________________ 5V2 Dolomite, grayish-brown mottled with light-brown, very finely crystalline, rhombic, sugary textured, fetid. Weathers mottled light brownish gray and grayish orange; ledge forming ____________________________ 1 Dolomite, silty, dusky-yellow and light-olive-gray, mi- crocrystalline. Weathers yellowish gray; platy to laminated; forms reentrant _______________________ 3 Dolomite, pale-yellowish-brown and yellowish-brown, finely crystalline, rhombic, sugary textured. Weath- ers yellowish gray; ledge forming _________________ 3 Dolomite, silty, yellowish-gray to light-gray, crypto- crystalline. Weathers grayish yellow; platy to lami- nated ; forms reentrant ____________________________ 1 Dolomite, yellowish-brown, dark-yellowish-brown, and grayish-brown, very finely crystalline, rhombic, sugary textured, limonitic. Bottom 2 ft. is silty and slightly glauconitic and contains scattered subangular pebbles of chert and small angular fragments of fish plates. Weathers pale yellowish brown; in 2 beds; ledge forming ____________________________________ 31/2 Dolomite, calcitic, silty, light- to dark—brownish-gray, and dark-yellowish-orange, microcrystalline, limonit— ic, slightly sandy. Weathers yellowish gray; platy to thinly laminated; forms reentrant; thins north- westward to 1/2 ft at center of outcrop ____________ 11A) Dolomite, dark-yellowish—brown to brownish-gray, finely to very finely crystalline, slightly sandy and silty, very slightly glauconitic. Contains abundant frag— mentary and whole fish plates as much as 5 in. in length and scattered subangular pebbles of chert. Large collection of Bothriolepis sp. from this bed. Weathers pale yellowish brown; forms upper bed of 31/2-ft-thick ledge; pinches out apparently by onlap about 250 ft northwestward _______________________ 1 C52 Thickness (feet) Maywood Formation—Continued Dolomite, conglomeratic, yellowish-brown and varie- gated, finely to coarsely crystalline, slightly limonitic, slightly glauconitic, slightly sandy, slightly silty. Contains subangular to angular pebbles of chert, rounded flat pebbles of medium-dark—gray siltstone and light-olive-gray dolomite, and abundant fragmen- tary fish remains. Top 7 in. contains scattered whole fish plates, as much as 8 in. in length. Weathers pale yellowish brown; forms lower part of 3%-ft-thick ledge; pinches out apparently by onlap within 250 ft northwestward Dolomite, silty, moderate-yellowish-brown mottled with yellowish-brown and dark-yellowish—orange, finely crystalline, slightly sandy, slightly glauconitic, slightly calcitic. Contains abundant subangular peb- bles of chert, fragmentary fish remains, fragmentary carbonized plant remains, and spores. Basal contact is undulatory surface with relief of about 6 in. Weathers mottled yellowish gray, pale yellowish brown, and dark yellowish orange; forms reentrant; pinches out 25 ft northwestward ___________________ 11/2 Dolomite, silty to very silty, conglomeratic, sandy, dusky-yellow, yellowish-gray, yellowish-orange, pale- yellowish-brown, and pale-olive, limonitic, slightly glauconitic, slightly calcitic. Grades in part to dolo- mitic siltstone. Contains subangular to subrounded pebbles of chert, rounded flat pebbles of medium-dark- gray siltstone and light-olive-gray dolomite, and small fragmentary fish plates of Bothriolepis sp. Inter- bedded with lenses of conglomerate composed of chert, dolomite, and siltstone pebbles. Basal few inches is loosely consolidated regolithic breccia composed of medium-dark-gray siltstone and greenish-gray and pale-olive shale. Weathers to yellowish-gray, yellow- ish-orange, and grayish-yellow smooth spheroidal surfaces studded with pebbles weathering grayish brown and dark yellowish brown. Upper 4 ft forms ledges; lower 6% ft forms slope. Thickens to 16% ft and forms clifi at center of outcrop; thins to 4 ft and forms partly covered slope at north end ________ 10% Total thickness 34 This sequence is divisible into three units summarized as follows: a lower unit, 101/2 feet thick, composed of yellowish-gray very silty dolomite; a middle unit, 18 feet thick, consisting of 4 ledges of yellowish-brown dolomite separated by reentrants of yellowish—gray silty dolomite; and an upper unit, 51/2 feet thick, composed of yellowish—gray very silty dolomite. Rounded peb- bles of siltstone and dolomite and grains of glauconite derived from the underlying Cambrian rocks are com- mon in the lower unit and bottom part of the middle unit. Subangular and angular pebbles of dense chert are common throughout, but their size decreases up- ward. The chert is largely light gray but includes some light- to medium-bluish-gray and a little medium- dark-gray and d'ark-‘bluish-gray chert. Lack of round- ing of the resistant chert pebbles suggests that they were not transported far. A close prob-able source is STRATIGRAPHY AND PALEONTOLOGY the chert-bearing Bighorn Dolomite of Late Ordovician age, whose erosional edge lies 10 to 20 miles east and south (fig. 1). Another possible source is the chert- bearing upper part of the Red Lion Formation, which is present within a few miles of the Squaw Creek locality. The biota contained in the Squaw Creek section con- sists largely of fish and some carbonized plant remains and spores. Most of the fossils are in the bottom part of the middle unit, but fragmentary fish remains are scattered through the lower unit. The fish were tenta- tively identified as Bothriolepis sp. by D. H. Dunkle (written communication, June 27, 1963). The plant remains include an early arthrophyte (S. H. Mamay, written communication, Feb. 14, 1962), and the spores include a few trilete forms and possibly Tasmanites sp. (R. H. Tschudy, written communication, July 31, 1962). The mixed biota suggests a marginal-marine brack— ish- or fresh-water environment for the Maywood F or- mation in the Gallatin Range. Although Bothm'olepis sp. generally is considered an indicator of continental deposits, some of its occurrences in Wyoming have been interpreted as near—shore transgressive marine (Deni- son, 1951) or as marginal marine (Sandberg, 1963). The plant remains and trilete spores are continental, but Tasmanites sp. is marine. OCCURRENCE IN THE LOGAN AREA The 56—foot-thick section exposed on the north side of an unnamed gulley east of Milligan Canyon (fig. 2) in the northeast corner of sec. 1, T. 1 N., R. 1 W., Jeffer- son County, is representative of the Maywood Forma- tion in the Logan, Mont., area. A more generalized sec- tion at the same locality was measured by Robinson (1963), who also recognized the three-fold subdivision of the Maywood there. The lithologic character and succession of beds of the Maywood Formation at Milligan Canyon are similar to those of the Maywood at Squaw Creek in the Gallatin Range, but the biOta differs greatly. The sequence at Milligan Canyon comprises a lower unit, 25 feet thick, composed of yellowish-gray silty dolomite; a middle unit, 20 feet thick, consisting of 4 ledges of light-olive- gray or medium-dark-gray fossiliferous dolomitic limestone separated by reentrants of yellowish-gray silty dolomitic limestone and dolomitic siltstone; and an upper unit, 11 feet thick, composed of yellowish- gray silty limestone and silty calcitic dolomite. Sub- rounded pebbles of quartzite are found only in the basal 11/2 feet of the lower unit. These may have been de— rived from the Red Lion Formation, which contains SANDBERG AND MCMANNIS quartzite on Conrow Creek . about 15 miles west of Milligan Canyon. At Milligan Canyon, the biota, which is of early Late Devonian age, consists largely of brachiopods reported by Sandlberg and Hammond (1958) and also includes echinoids, conodonts, ostracodes, and trochiliscids. The f0$ils are found in the middle unit and indicate an open-marine environment for at least this part of the sequence. The lower unit contains abundant salt casts at several nearby sections and probably was deposited in a brackish-water or slightly restricted marine en- vironment. The upper unit, like that in the Gallatin Range, yields no positive indication of its depositional environment. PALEOGEOGRAPHIC INTERPRETATION The Maywood Formation of the Logan area is the correlative of the marine Souris River Formation, which is of Late Devonian age farther east in Montana ('Sandberg and Hammond, 1958). The type Maywood, which is of Late ( ?) Devonian age in western Montana, has the same thickness, about 340 feet, as the Souris River at its center of accumulation in the Williston basin of northeastern Montana. Both formations may contain older Devonian beds in these areas, but the for- mations become younger and progressively thinner by transgressive onlap in the intervening area. The relation of an isolated channel-fill deposit of the Souris River( 3) Formation at Cottonwood Canyon, Wyo. (Sandberg, 1963), to the main body of the Souris River Formation provides a close parallel to the rela- tion of the Maywood of the Gallatin Range to that of the Logan area. The deposit at Cottonwood Canyon, like the one at Squaw Creek, underlies the Jefferson Formation and contains a mixed biota that includes Bothriolepis sp. The Cottonwood Canyon deposit was interpreted by Sandberg (1963) to have been laid down in the upper reaches of a long, narrow estuary that ex— tended into a retreating shoreline while the shallow Souris River sea transgressed westward and southward from the Williston basin. Similarly, the Squaw Creek deposit probably was laid down in an estuary or bay farther west along this same southward—retreating shoreline, after the Maywood sea had transgressed east- ward from the Cordilleran seaway and coalesced with the Souris River sea somewhere in central Montana. To the north in northwestern Montana and western Alberta and farther south in western Wyoming, how- ever, the major direction of transgression of the shallow early Late Devonian sea probably was eastward from the Cordilleran seaway. C53 The resulting distribution of the Maywood Forma- tion is erratic. The Maywood may be very thin locally or entirely absent from small areas north of its ap- proximate southern limit (fig. 1). These areas repre- sent topographic highs on the landmass that existed in the region during much of Early and Middle Devonian time. They probably were islands during part or all of Maywood deposition. Conversely, however, isolated brackish- or fresh-water deposits of the Maywood may be more widespread than previously suspected in the former drowned coastal region south of the present known limit of the Maywood (fig. 1). The widespread occurrence in southern Montana and northern Wyoming of isolated Upper Devonian basal channel-fill deposits, representing brackish- or fresh- water facies of the Maywood and Souris River Forma- tions, is strongly suggested \by regional paleogeography and is supported by some recently measured sections. Furthermore, several Upper Devonian channel-fill de- posits recently were observed at the base of the Darby Formation of Late Devonian age in the Wind River Range of west—central Wyoming (J. F. Murphy, oral communication, July 1963; A. L. Benson, written com— munication, Aug. 12, 1963). These deposits contain Bothm'olepz's sp. and are related to the Maywood For- mation, although they were deposited during direct eastward transgression of the Late Devonian sea in that area. PALEOGEOGRAPHIC RELATION OF UPPER AND LOWER DEVONIAN CHANNEL-FILL DEPOSITS Channel-fill deposits of the Beartooth Butte Forma- tion of Early Devonian age also overlie the Bighorn Dolomite in the area of southern Montana and northern Wyoming where isolated Upper Devonian channel-fill deposits may be widespread. Some Maywood and re- lated Upper Devonian basal channel-fill deposits have steep sides, coarse textures, grayish-red coloring, and scattered fish remains like some deposits of the Bear— tooth Butte Formation. Thus, unlike the basal beds of the Jefferson Formation, which generally are dis- tinguishable from the Beartooth Butte on the basis of lithologic criteria (Sandberg, 1961, p. 1304), the May- wood and related deposits are not readily distinguish— able from the Beartooth Butte without paleontologic determination of the fish remains. Close association of Upper and Lower Devonian channel-fill deposits has been noted in several measured sections. At Cottonwood Canyon, Wyo., well-dated channel—fill deposits of the Souris River ( ?) Formation of Late Devonian age and of the Beartooth Butte For- C54 mation of Early Devonian age have been reported in about the same stratigraphic position and only a few hundred feet apart by Sandberg (1963). At Beaver Creek in the Big Belt Mountains, Mont, shallow-water marine beds of the Maywood Formation directly overlie a channel-fill deposit, which contains fish remains of probable Early Devonian age (Sandberg, 1961, p. 1306). At Livingston Peak, Mont, a brackish—water deposit of the Maywood Formation now has been recognized to directly overlie a channel-fill deposit of the Beartooth Butte Formation, previously reported by Sandberg (1961). Near Livingston Peak, two thin unfossilifer— ous channel-fill deposits at Yellowstone Canyon and Canyon Mountain, previously assigned to the Beartooth Butte by Sandberg (1961, fig. 1), now are considered to be Maywood. The regional occurrence and local association of Upper and Lower Devonian channel-fill deposits in the same general stratigraphic setting suggest that some valleys, which previously had been inundated by the Early Devonian sea, served to localize and control the southward and eastward transgressions of the Late Devonian sea. 5% STRATIGRAPHY AND PALEONTOLOGY REFERENCES Denison, R. H., 1951, Late Devonian fresh-water fishes from the western United States: Fieldiana Geology, v. 11, no. 5, p. 221—261. McMannis, W. J., 1962, Devonian stratigraphy between Three Forks, Montana, and Yellowstone Park, in Symposium, The Devonian System of Montana and adjacent areas: Billings Geol. Soc. Guidebook 13th Ann. Field Cont, Sept. 1962, p. 4—12. Robinson, G. D., 1963, Geology of the Three Forks quadrangle, Montana: US. Geo]. Survey Prof. Paper 370, 143 p. Sandberg, C. A., 1961, Widespread Beartooth Butte Formation of Early Devonian age in Montana and Wyoming and its paleogeographic significance: Am. Assoc. Petroleum Geolo- gists Bull. v. 45, no. 8, p. 1301—1309. 1962, Stratigraphic section of type Three Forks and Jefferson Formations at Logan, Montana, in Symposium, The Devonian System of Montana and adjacent areas: Bil- lings Geol. Soc. Guidebook 13th Ann. Field Cont, Sept. 1962, p. 47—50. 1963, Spirorbal limestone in the Souris River( ?) Forma- tion of Late Devonian age at Cottonwood Canyon, Bighorn Mountains, Wyominngrt. 63 m U.S. Geol. Survey Prof. Paper 475—0, p. 014—016. Sandberg, C. A., and Hammond, C. R., 1958, Devonian system in Williston basin and central Montana: Am. Assoc. Petro- leum Geologists Bull., v. 42, no. 10, p. 2293—2334. Abstract—An 8-foot core taken 3,873 to 3,881 feet below the land surface and about 75 feet below the base of the sedimen— tary rocks of the Coastal Plain consists of strongly foliated garnet-microcline—biotite—quartz-plagioclase veined gneiss close to migmatite in structure. The structures, textures, and min- erals of this rock are described in detail. A K-Ar age of 235 m.y. on biotite suggests recrystallization during the late Paleo— zoic metamorphic event that affected parts of southeastern New England. A test—drilling program at Island Beach State Park, NJ. (fig. 1), was undertaken by the US. Geological Survey in cooperation with the New Jersey Division of Water Policy and Supply to provide (1) geologic and hydrologic data pertaining to the ground-water resources of southern New Jersey, and (2) a sample of the crystalline basement rocks underlying the Coastal Plain. An exploratory borehole was drilled through the entire unconsolidated Coastal Plain sequence and into decomposed and fresh basement gneiss. A depth of 3,891 feet was reached. The unconsolidated rocks were drilled by conventional rotary methods, and a diamond coring bit producing core 3.85 inches in di- ameter was used in the fresh gneiss. An 8-foot section of core was recovered from a depth of 3,873 to 3,881 feet below the surface, or about 75 feet below the base of the Coastal Plain sedimentary rocks as delimited by Seaber and Vecchioli (1963). Eight sidewall cores were obtained from a section of decomposed gneiss ly- ing between the base of the Raritan Formation and fresh basement rock (fig. 2). The stratigraphic section of the Coastal Plain se— quence at Island Beach (Upper Cretaceous to Recent) has been described by Seaber and Vecchioli (1963), and further water-resources studies of these rocks are in progress. The purpose of this article is to describe and interpret the pre-Cretaceous basement gneiss. Be- cause of the scarcity of information on the rocks that GEOLOGICAL SURVEY RESEARCH 1964 PETROGRAPHY OF THE BASEMENT GNEISS BENEATH THE COASTAL PLAIN SEQUENCE, ISLAND BEACH STATE PARK, NEW JERSEY By DAVID L. SOUTHWICK, Washington, D.C. underlie the thicker parts of the Coastal Plain sequence, the gneiss is described in considerable detail. MEGASCOPIC DESCRIPTION OF THE BASEMENT GNEISS The basement rock at Island Beach State Park is a veined gneiss approaching migmatite in character. It consists of two parts : a well—foilated dark-gray medium- g r a i n e d garnet-microcline-biotite-quartz-plagioclase “body” (hereinafter called the paleosomel), and nu- merous virtually concordant, igneous-appearing string— ers of quartz-feldspar alaskite and pegmatite ranging from about 1 to 20 cm in thickness (referred to as the neosome 1). All the essential minerals can be easily identified with the naked eye. The paleosome consists of crystals 1—2 mm across; the quartzo—feldspathic vein- lets are generally somewhat coarser, and in the largest veinlet the crystals attain dimensions of 1—2 cm. The paleosome is banded; individual layers a few millimeters thick differ in the ratio of biotite to quartz and feldspar. The quartzo-feldspathic stringers are parallel to the banding, and all gradations exist between vaguely bounded millimeter-thick layers and lenses of quartz and plagioclase within the body of the gneiss to more sharply bounded, coarser quartz—microchne-pla- gioclase stringers a centimeter or two thick. If the core is assumed to be vertical, the banding dips 35—45°. Bio- tite flakes are imperfectly oriented parallel to it, giving foliation surfaces a lustrous sheen. A weak lineation of elongate biotite can be made out roughly parallel to the “strike” of the inclined foliation planes. In addition to the gneissic banding, there is a second, far more subtle foliation consisting of short, discon- 1The migmatite terminology used here is that recommended by Dietrich and Mehnert (1961). The paleosome is the “older part of a composite rock (i.e., the remaining or pre-existing part).” The neo- some is the “younger part of a composite rock (for example the in- jected, exuded, or metasomatically introduced material)." U.S. GEOL. SURVEY PROF. PAPER 501-0, PAGES 055-060 C55 C56 ~ mimmyn - . 7:“ auvmvmu- - ‘9'. .0. 'O STRATIGRAPHY AND PALEONTOLOGY Island Beach test well Coastal Plain sequence; unconsoli- dated, undeformed clay, sand, and gravel ranging from Lower Cre- taceous to Recent in age Triassic red shale, sandstone, and conglomerate with intercalated basalt flows and diabase sills. Gently warped and block faulted E Conglomerate, arkosc, and slate, much deformed, variably meta- morphosed; intercalated coal carries Pennsylvanian fossils Folded Paleozoic sedimentary rocks of Appalachian Valley and Ridge province and Appalachian Plateaus |. Delaware '\ ~ .' Bay ‘, l . EXPLANATION \ \ \ \\\\\\ Primarily Cambrian and Ordovician dark shales and carbonate rocks. Structure is complex, featuring strong overturning to northwest Intensely deformed lower Paleozoic clastic and carbonate rocks with inliers of schist and gneiss that may be equivalent to parts of Glenarm Series and Baltimore Gneiss of eastern part of Piedmont province Mainly quartzose feldspathic gneiss and assorted pelitic schists invaded by granitic plutons of many types and several ages. Mafic rocks are represented but are relatively Metamorphic terrane comprising quartzose feldspathic and amphi~ bolitic gneisses (Fordham Gneiss); marble; many kinds of schist (Man- hattan Schist and others); and intrusions ranging in composition from granite to serpentinite 50 100 MILES l l l I I I I Variable metamorphic complex in- cluding a “basement" of quartzose feldspathic to amphibolitic gneiss (Baltimore Gneiss); quartzite, marble, and assorted schists (Glen- arm Series); and intrusions rang- ing from granite to serpentinite L - ' Strongly overturned lower Paleozoic carbonate and clastic rocks com- plexly infolded with and overthrust by Precambrian quartzose feld— spathic gneiss, granite, and amphi- bolite Precambrian gneiss complex in- cluding every gradation from quartz-mica schist to granitic gneiss; also some hornblende gneiss, marble, and quartzite. Equivalent to Precambrian parts of the Reading prong Approximate contact FIGURE 1.—Map showing the position of the Island Beach test well with respect to the major geologic subdivisions of the nearby Middle Atlantic States and southern New England. SOUTHWICK tinuous shears carrying oriented biotite (visible only in two short sections of the core) and a vague “grain” of biotite flakes and elongate quartz crystals. Over most of the core this foliation dips in the same direction as the gneissic banding but at shallower angles (0—20°) ; locally it flattens and reverses. Possibly its intersection with the gneissic banding has produced the weak bio- tite lineation mentioned above. The proportions of quartz, plagioclase, and micro— cline in the neosome vary greatly from stringer to stringer. Commonly the thick stringers (>5 cm) are richer in microcline than are thin ones, but exceptions were noted. Some stringers exhibit rude compositional zoning. The central part consists of microcline and quartz with minor plagioclase and biotite; the marginal parts are rich in plagioclase and quartz and relatively poor in microcline. Most stringers thicker than about 1 cm are bordered by a narrow black rim composed of fine-grained biotite with a small proportion of plagio- clase and quartz. These mafic borders range from about 0.5 mm to 1 cm in thickness, the thicker ones gen- erally being associated with the thicker stringers. They pinch and swell, branch, and braid, and some are discontinuous. Elongate lenses of the same material occur in the central parts of some veins. GENERAL MINERALOGY The following minerals were identified in the gneiss: plagioclase (A1130), quartz, biotite, microcline (both perthitic and nonperthitic), garnet, muscovite, car- bonate, chlorite, green amphibole, epidote, magnetite- ilmenite, apatite, zircon, sphene, tourmaline, and mona— zite. An average modal analysis of the paleosome is given in the accompanying table. Average modal analysis of the paleosome of the basement veined gnetss at Island Beach State Park, N .J . [From 6,337 points counted on 5 thin sections from different parts of the core] Constituent Percentage Constituent Percentage Quartz _______________ 34. 4 Sphene _______________ Tr. Plagioclase (A1130) _____ 40. 4 Epidote ______________ Tr. Mic‘rocline ____________ 3. 6 Ohlorite ______________ 0. 1 Biotite _______________ ‘18. 6 Tourmaline ___________ Tr. Garnet _______________ . 1 Granophyre ___________ Tr. Muscovite ____________ . 7 Myrmekite ___________ Tr. Carbonate ____________ . 6 Hydrothermal Opaque material _______ .2 assemblage 1 ________ 1 0 Apatite _______________ . 2 ——~ Zircon ________________ Tr. Total __________ 100. 0 1Hydrothermal assemblage is a fine mat of bleached, pinkish-yellow biotite, sericitic muscovite, and microcrystalline silica with or without chlorite, carbonate, powdery sphene, and shreds of deep blue-green amphibole. C57 DESCRIPTIVE PETROGRAPHY Paleosvome- Plagioclase, the most abundant mineral of the paleo- some, forms highly irregular crystals which are unzoned to very weakly zoned and are, as a rule, rather poorly twinned. Compositions, determined on the universal stage by the methods of Turner (1947) and Kohler (1941) using unpublished correlation curves compiled by T. L. Wright, range from A1127 to An“, with the largest grouping near Anao. The structural state is unequivocally ordered. All plagioclase is sericitized. Most crystals are lightly altered, but some are exten- sively replaced by white mica, dusty clinozoisite, albite, and quartz. There is no obvious compositional or structural control of the degree of sericitization. Quartz occurs both as severely strained, anhed-ral in— dividual grains up to 2 mm across and as fine-grained granular patches of unstrained crystals. The granular quartz commonly rims or invades large strained crystals, suggesting that it formed by cataclasis and recrystalli- zation of the large grains. Elongate augen of recrys- tallized quartz parallel the foliation defined by oriented biotite. Microline forms shapeless amoeboid grains which commonly are congregated in small patches or short trains. The crystals usually surround and engulf smaller crystals of quartz, plagioclase, and biotite. The distribution and textural relations suggest that micro— cline grew porphyroblastically and is younger than the other main minerals. A diffuse plaid twinning, never sharply defined, is characteristic of the microcline in this rock. Most of the microcline in the paleosome is nonperthitic. Oriented biotite plates as much as 2 mm long and 0.1 mm thick are primarily responsible for the foliation of the rock. The biotite typically is pleochroic in shades of olive and drab greenish brown, but the colors vary slightly from place to place in the core. Locally the biotite is marginally altered to green chlorite, and in a few spots complete alteration to a mat of chlorite, muscovite, magnetite, and sphene has taken place. Biotite, as well as plagioclase and microcline, commonly shows evidence of mild bending and cracking. Porphyroblasts of red-brown garnet up to 4: mm across are scattered throughout the paleosome. Typi- cally they are subhedral and sieved with inclusions of quartz and biotite. A few show incipient alteration to green chlorite. The refractive index of the garnet is 1.789i0.002, and the edge of the unit cell (deter- mined from an X—ray difi'raction pattern of garnet plus quartz and biotite inclusions) is 12.055 A. These values cannot be fitted to any composition of anhydrous garnet. C58 The closest correspondence is to compositions between andradite and grossularite (Sriramadas, 1957), even though the cell edge is slightly longer than that of pure andradite. The anomalous cell edge could be due to hydration or other substitutions in the garnet struc- ture (Chinner and others, 1960; Pistorius and Kennedy, 1960), or interference in the X-ray diffraction pattern caused by the inclusions. Muscovite and carbonate form scattered large crys- tals, but more commonly they occur as a fine-grained mat together with chlorite, yellowish biotite, quartz, and granular opaque material. This assemblage forms discontinuous veinlets and vague defined patches that generally are associated with shear zones su‘bparallel to the gneissic banding. Crosscutting veinlets also oc— cur, however. Neosome The neosome has an igneous rather than a metamor- phic appearance. Typically the texture is coarse al- lotriomorphic granular with deeply embayed inter- locking orystals of feldspar and quartz. Microcline perthite is abundant in and characteristic of the neosome. It makes up 5 to 40 percent of each vein, in general forming a larger proportion of the thicker ones. Some very thin veinlets contain micro- cline crystals that are larger than the width of the veinlet. These crystals penetrate into the “wallrock” on both sides without disturbing its foliation; this sug- gests that they are porphyroblasts that grew by replace- ment. Wispy, regularly oriented lamellae of albite are estimated to make up 5—10 percent of the perthite. The composition of the unheated microcline host, deter- mined by the X—ray method of Orville (1960), is Orggzl. The obliquity, determined by the 131—181 method of Goldsmith and Laves (1954), is 0.87. The obliquity of “maximum” microcline of composition Org3 is 0.90; therefore the microcline host of the neo- some perthite is probably close to “maximum” micro— cline. The plagioclase of the neosome has a composition of Angg. It is virtually unzoned and rather poorly twin- ned. Both it and the microcline perthite are lightly dusted with sericite and show evidence of mild bending and cracking. Quartz occurs in the same way as it does in the palm- some, forming large, strained individual grains and clusters of smaller recrystallized grains. The widely dispersed olive-brown biotite seems no different from that in the darker parts of the rock. All the main minerals are crosscut by narrow veinlets containing car- bonate, muscovite, and a little quartz. STRATIGRAPHY AND PALEONTOLOGY DECOMPOSED INTERVAL In the generalized log of the test well at Island Beach State Park, N.J., given by Seaber and Vecchioli (1963, p. B104—B105) a 64-foot section between the base of the Raritan Formation (depth 3,798 feet) and fresh basement gneiss (depth 3,862 feet) is described as “gneiss, biotite, weathered (saprolite?).” Petro- graphic study of eight samples from this interval (fig. 2) indicates that some of the material is not untransported saprolite, but is a poorly sorted, highly angular epiclastic sand. Depth (in feet) RARITAN FORMATION (UPPER CRETACEOUS) Lowermost 20 feet is clay, multicolored in shades of light gray (N—7). medium light gray(N—6), and dusky red (5R3/4). spar- ingly micaceous; contains siderite nod< ules, limonite, and hematite BASAL UNCONFORMITV OF SEABER _,_ 3798 «*WM\, 3800* < AND VECCHIOL/ ((963) RARITAN(?) FORMATION 3806* < Sandstone. friable, clayey. multicolored in shades of light gray and buff. Contains small pebbles of quartz, ironstone, shale, and calcareous siltstone in a matrix of fine, angular quartz sand loosely ce- 3816* < mented by kaolinite and mica BASAL UNCONFORMITY (THIS ARTICLE) ,#/~\? /“\4-/\\?,f\_"s\_,/\ ?/—-\v._\ ?/\_,‘\ DEPTH APPROXIMATE 3830* < DECOMPOSED BASEMENT GNEISS 3836* K Saprolite, speckled gray green and yellow white, with relict foliation. Relict quartz, biotite.and garnet common. Relict :k 3840 < plagioclase in lower 20 feet. Chlorite. secondary mica, and montmorillonite(?) * abundant 3846 < 3850* k APPROXIMATE UPPER LIMIT \ 3862 \_/-tv/r\,/\_/—\_,—\vz~\~,~EE/—\_ OF FRESH ROCK FRESH BASEMENT GNEISS (PALEOZOIC?) 3873* Well-foliated. dark-gray, medium-grained 7 garnet-microline-biotite-quartz-plagi- Core oclase gneiss cut by stringers of quart- zose feldspathic alaskite and pegmatite 38805“ 2 #389] BOTTOM OF HOLE- FIGURE 2,—Diagramnratic drawing of the lowermost 110 feet of the Island Beach test well. Numbers are depths below land surface (elevation approximately 10 feet). Depth measurements followed by asterisk are horizons at which samples were taken. Descrip- tion of basal Raritan Formation (above 3,798 feet on this figure) from Gill, Seaber, Vecchioli, and An- derson (written communication, 1963). SOUTI-IWICK The lowest five samples of the decomposed interval (3,850, 3,846, 3,840, 3,836, and 3,830 feet) are unques- tionably derived from basement gneiss. They are soft, friable, speckled gray-green and yellow-white saprolite with well—preserved foliation and abundant megascopic biotite. Thin sections reveal the textures of the fresh gneiss somewhat blurred and distorted by alteration effects. Relict quartz (both large strained individual grains and recrystallized patches), biotite, garnet, apa- tite, and zircon are present in all five samples. EX- tensively sericitized feldspar can be made out only in the lowest two. The biotite is commonly fringed by a very fine grained, grass—green, weakly to strongly bire— fringent aggregate which appears to be a mixture of chlorite and montmorillonite. Sizable patches of the same material occur throughout the rock. The place of feldspar is taken by a fine mat of sericitic muscovite (possibly with some kaolinite) and a pale-brown dust of high refringence that may be finely divided clinozoisite. The highest three samples of the interval (3,816, 3,806, and 3,800 feet) are tenacious clayey sand with scattered small pebbles. The color is streaky and un- even in shades of light gray and buff. The pebbles are subrounded to subangular and smaller than 1 cm in diameter. The majority are quartz, but iron-oxide- cemented sandstone, dark shale, calcareous siltstone, carbonate, and glauconite are also represented. The pebbles are distributed in a matrix consisting primarily of highly angular quartz silt and fine sand loosely cemented by a variable mixture of kaolinite, muscovite, pale-green chlorite, and iron oxides. Framework and cement are about equal in proportion. Besides quartz, clastic grains of perthite, microcline, epidote, greatly saussuritized plagioclase, carbonate, and “chert” occur in the framework but do not total more than 10 percent. Biotite is exceedingly scarce, and the deep—green chlorite and montmorillonite characteristic of the subjacent sap- .rolite are absent. The epiclastic textures, especially the rounded peb- bles, suggest that at least the upper 18 feet of the “weath- ered gneiss” of Seaber and Vecchioli (1963, p. B104— B105) belongs to the lowermost part of the Raritan Formation rather than to the basement rocks (fig. 2). The material may 'be a combination of reworked, little- transported saprolite plus sand brought in from else- where, or it may be simply an immature sediment having no genetic connection with the underlying decayed rock. The decomposed interval corresponds in position and general character to the “weathered zone” found on base- ment rocks beneath the sedimentary sequence of the Coastal Plain at many other localities. There is no new r132~1760 0—64—5 C59 evidence in the Island Beach profile bearing on the origin of this regional feature. AGE A potassium-argon age measurement was made on biotite from the paleosome of the Island Beach core by Richard Marvin of the Isotope Geology Branch, US. Geological Survey. An apparent age of 235 million years was obtained. A rubidium-strontium age deter- mination on microcline from the neosome was at- tempted, but was unsuccessful. The biotite age is con- sidered to be a minimum. POSSIBLE REGIONAL GEOLOGIC AFFINITIES While there is little point in attempting to correlate the gneiss at Island Beach with specific gneiss units in exposed crystalline complexes (the closest outcrops are over 50 miles away), it is of interest to speculate on the possible regional geologic relations. Figure 1 shows the position of the Island Beach test well with respect to the major geologic subdivisions of the Middle Atlantic States and southern New England. The map pattern suggests that rocks of the Piedmont province probably join rocks of the Manhattan prong and the New England highlands somewhere beneath the New Jersey coastal plain or its seaward extension. It is into this indefinite terrane that the Island Beach test well has penetrated. On the basis of lithology, the gneiss at Island Beach fits equally well into all three provinces. Virtually identical vein gneisses are common in the eastern high- lands of Connecticut; the Putnam Series as used by Solar (1958) and Hebron Gneiss as used by Aitken (1951) are but two units in which they are found. The very complex Hartland Formation in the western high- lands of Connecticut (Rodgers and others, 1959, p. 33— 34) contains large tracts of migmatitic rocks. Veined gneisses occur in the Fordham Gneiss and to a lesser extent in the Manhattan Schist of the Manhattan prong (Prucha, 1956; Scotford, 1956; Fettke, 1914). Modal analyses indicate that most of the Fordham migmatites are more felsic than the Island Beach rock, but are otherwise similar (Scotford, 1956, p. 1172). The for- mation in the northeastern part of the Piedmont prov- ince most closely akin to the gneiss at Island Beach is the Precambrian Baltimore Gneiss (Knopf and Jonas, 1929, p. 143—146; C. A. Hopson, personal communica- tion, 1963). The Baltimore Gneiss is an exceedingly complex, mixture of well—layered paragneiss, banded gneiss, hornblende gneiss, amphibolite, migmatite, veined gneiss, augen gneiss, and uniform granitic gneiss. The veined gneiss phase is identical in all respects to the core from Island Beach. C60 The radiometric age of the biotite (235 m.y. mini- mum) may provide the only clue to the regional affini- ties of the Island Beach basement gneiss. This age is younger than any so far reported on biotite from the northeastern part of the Piedmont province or from the Manhattan prong, but corresponds well with the 230—250 m.y. dates obtained on biotite from the Nar- ragansett basin area of southeastern New England (Til- ton and others, 1958, 1959; Hurley and others, 1960; Long and Kulp, 1962). The available data suggest that parts of southeastern New England underwent a Per- mian-Carboniferous metamorphic event that did not affect (or was much weaker in) the northeastern part of the Piedmont province and the Manhattan prong. Pos- sibly this event extended as far southwest as Island Beach. It is not unreasonable to project a belt of meta- morphically related rocks along the curving regiOnal strike of the Appalachians from Rhode Island and Con- necticut to a point beneath the New Jersey coast ( fig. 1) . To summarize, the basement veined gneiss at Island Beach, N.J., may have been metamorphosed at least once in common with rocks of the Narragansett basin area of southern New England. Whether or not this establishes a correlation in terms of total rock age re- mains a matter of considerable doubt. Because the bio- tite age may not record the first or only metamorphic event, it is possible that the gneiss at Island Beach is older “Piedmont” or “Manhattan” rock that was re- crystallized in late Paleozoic time. REFERENCES Aitken, J. M., 1951, Geology of a section of the Hebron Gneiss of eastern Connecticut: Connecticut State Geol. and Nat. Hist. Survey Bull. 78, 62 p. Chinner, G. A., Boyd, F. R., and England, J. L., 1960, Physical properties of garnet solid solutions: Carnegie Inst. Wash- ington Year Book 59, p. 76—78. Dietrich, R. V., and Mehnert, K. R., 1961, Proposal for the nomenclature of migmatites and associated rocks : Internat. Geol. Cong, 21st, 1960, Copenhagen, pt. 26 (supp. vol.), p. 56—67. Fettke, C. R., 1914, The Manhattan Schist of southeastern New York and its associated igneous rocks: New York Acad. Sci. Annals, v. 23, p. 193—260. STRATIGRAPHY AND PALEONTOLOGY Goldsmith, J. B., and Laves, Fritz, 1954, The microcline-sanidine stability relations: Geochim. et Cosmochim. Acta, v. 5, p. 1—19. Hurley, P. M., Fairbairn, H. W., Pinson, W. B., and Faure, Gunter, 1960, K—A and Rb-Sr minimum ages for the Pennsyl— vanian section in the Narragansett Basin: Geochim. et Cosmochim. Acta, v. 18, p. 247—258. Knopf, E. B., and Jonas, A. I., 1929, The geology of the crystal- line rocks of Baltimore County: Maryland Geol. Survey, Baltimore County Rept., p. 97—199. Kfihler, A., 1941, Drehtischmessungen an Plagioklaszwillingen von Tief-and Hoch- temperaturoptik: Min. petr. Mitt, v. 53, p. 159—179. Long, L. E., and Kulp, J. L., 1962, Isotopic age study of the metamorphic history of the Manhattan and Reading Prongs: Geol. Soc. America Bu11., v. 73, p. 969—996. Orville, P. M., 1960, Powder X-ray method for determinaton of (Ab+An) content of microcline [abs] : Geol. Soc. America, Program 1960 Ann. Mtg, p. 171—172. Pistorius, C.W.F.T., and Kennedy, G.C., 1960, Stability relations of grossularite and hydrogrossularite at high temperatures and pressures: Am. J our. Sci., v. 258, p. 247—257. Prucha, J. J ., 1956, Stratigraphic relationships of the metamor- phic rocks in southeastern New York: Am. Jour. Sci., v. 254, p. 672—684. Rodgers, John, Gates, R. M., and Rosenfeld, J. L., 1959, Explan- atory text for preliminary geological map of Connecticut, 1956: Connecticut Geol. and Nat. Hist. Survey Bull. 84, 64 p. Sclar, C. B., 1958, The Preston Gabbro and the associated meta- morphic gneisses, New London County, Connecticut: Con- necticut Geol. and Nat. Hist. Survey Bull. 88, 136 p. Scotford, D. M., 1956, Metamorphism and axial-p‘lane folding in the Poundridge area, New York : Geol. Soc. America Bull. v. 67, p. 1155—1198. Seaber, P. R., and Vecchioli, John, 1963, Stratigraphic section at Island Beach State Park, New Jersey: Art. 26 m U.S. Geol. Survey Prof. Paper 475—B, p. B102—B105. Sriramadas, Aluru, 1957, Diagrams for the correlation of unit cell edges and refractive indices with the chemical com- position of garnet: Am. Mineralogist, v. 42, p. 294—298. Tilton, G. R., Wetherill, G. W., Davis, G. L., and Hopson, C. A., 1958, Ages of minerals from the Baltimore Gneiss near Baltimore, Maryland: Geol. Soc. America Bull., v. 69, p. 1469—1474. Tilton, G. B., Davis, G. L., and Wetherill, G. W., 1959, Mineral ages in the Maryland Piedmont: Carnegie Inst. Washington Year Book 58, p. 171-174. Turner, F. J ., 1947, Determination of plagioclase with the four- axis universal stage: Am. Mineralogist, v. 32, p. 389-410. GEOLOGICAL SURVEY RESEARCH 1964 OFFSHORE EXTENSION OF THE UPPER EOCENE TO RECENT STRATIGRAPHIC SEQUENCE IN SOUTHEASTERN GEORGIA By MORRIS J. McCOLLUM and STEPHEN M. HERRICK, Atlanta, Ga. Work done in cooperation with the Georgia, Department of Mines, Mining, and Geology Abstract—Strata ranging in age from Recent to late Eocene were penetrated in test holes drilled 10 miles ofishore from Savannah Beach, Ga. Study of the rock cores and cuttings re veals that the stratigraphic sequence is similar to that onshore but that the post-Miocene section is thinner. During the summer of 1962, two test holes were drilled for the US. Coast Guard into the sediments beneath the ocean floor at lat 31°56’531/2” N. and long 80°41’00” W., about 10 miles offshore from Savannah Beach, Ga. Rock cores and cuttings obtained by drill- ing were analyzed 1 to determine significant engineer- ing properties for foundation design of a proposed “Texas-type” tower to replace the Savannah lightship. Samples from the borings were made available to the authors for geologic study, and as a result, the upper Eocene to Recent stratigraphic section has been ex- tended offshore as far as the drilling site. Previous to the test drilling, hydrographic and seis- mic surveys were made from Savannah Beach to, and in the vicinity of, the proposed tower site? Both sur- veys were made simultaneously from a boat by means of a fathometer and sonar boomer. An electronic posi- tioning apparatus was used to obtain horizontal con- trol, and US. Coast Guard tide gages were used for vertical control. The hydrographic survey showed that the ocean floor in the vicinity of the proposed tower site is from 49 to 55 feet below mean sea level. According to the seismic interpretation, in the area of the proposed tower site there is a north-trending linear zone of slight structural 1 Walter E. Hanson and Co., 1962, Foundation engineering report for U.S. Coast Guard offshore structure, Savannah, Georgia: Springfield, Ill., unpub. rept. 2Norman Porter and Associates, 1962, Hydrographic and geological surveys for offshore structure project, Savannah, Georgia: New York, unpub. rept. disturbance and possible faulting. Although the seis- mic data were interpreted to indicate a small reef or shell bed in the sediments of late Miocene ag'e, corrobo- rative evidence for such was not observed in the samples from the offshore test holes. Correlated with pertinent information from a US. Geological Survey test hole (GGS 772, fig. 1), the seismic data indicate that the top of the lower Miocene limestone is an unconformity and is about 105 feet below sea level at the proposed tower site. The geologic section on figure 1. shows the relation of the upper Eocene to Recent stratigraphic units in Chat- ham County, Ga., to those penetrated 10 miles offshore. The section extends southeasterly from a point about 7 miles northwest of Savannah, Ga., through Savannah and Savannah Beach to the proposed site of the tower. The onshore part of the section was modified from Mc- Collum and Counts (1964). The indicated correlations are based principally on lithologic and paleontologic evidence supplemented by electric and gamma-ray logs. The fossils listed on the section are F oraminifera, and only selected guide species are shown. Although all the onshore test holes were drilled through the Ocala Limestone, only the uppermost part of this stratigraphic unit was penetrated in the offshore hole (fig. 1). The Ocala, which consists of gray to buff fossiliferous limestone, is the source of most of the ground water pumped in the area. Its average thick- ness in Chatham County is about 400 feet. Overlying the Ocala Limestone are undifferentiated rocks of Oligocene age. They consist predominantly of fossiliferous limestone inland but grade laterally to sandy limestone near the coast and to limy sand at the offshore site. The sediments of Miocene age have been divided into three lithologic units. The lower Miocene sediments (LS. GEOL. SURVEY PROF. PAPER 501-C. PAGES C61-063 C61 STRATIGRAPHY AND PALEONTOLOGY C62 .ouoamuo Ban 3 can :50 .5380 8.2395 E sang 939.9533? unoowm 3 9883 .qun 95923 5525 BMBBGIA SEER wfiSnES £5st .Emox EQBE hi 3 ‘35 355885 359 onooom Saab W Essa Etc: vs: .vfiSmwSS 32:6 .wgsgfisx msgwbfimwfi $398 3 SEN: 950850 7/4 mSwaE: 53$». N533» .§£u§u 33:” S§£Am¢§l 25082 32:5 ZOC.m_4 (mm Z5: 0 .3 Post-Catoctin Lu 0. E 3 sedimentary rocks , 23 D rrenton >3 ”- E 1 g. 8? Z V . . < § Catoctm Formatmn — §> '2 g g: -Q :3 § 2 g < 3 U a. Li] Pre-Catoctin E metasedimentary rocks , Z s s s s :<-:< E g g ’\/ I /\\/ ‘ 2 “l 3 Pl t ' k < 38° _ a: u onlc roc s a (I 0. Contact Fault 1~ >< 30 I I 40 50 M I Analyzed specimen Number refers to sample ILES in table FIGURE 1.—Geologic map of the Blue Ridge anticlinorium in Virginia, showing sources of analyzed rocks (1, 2, 3, 4). Generalized from geologic map of Virginia (Virginia Division of Mineral Resources, 1963). tholeiitic basalt regionally metamorphosed under low- grade conditions. He cites the areal extent of individual flows, thinness of breccia zones between flows, presence of columnar jointing, and absence of pillow structure as evidence for subaerial eruption. He believed that the original lava was a tholeiitic basalt because of the wide- spread preservation of intersertal or intergranular tex- tures, and the occurrence of relict augite and pigeonite in the greenstone and relict labradorite in feeder dikes. Bloomer and Werner (1955) and Reed (1955) cite previously published chemical analyses in support of their respective conclusions, but no modern chemical analyses of greenstone from the Catoctin Formation in Virginia were available to them. The purpose of this article is to present four new analyses of Catoctin green- stone, and to discuss briefly their bearing on the inter- pretation of the origin of the greenstone. One of the analyzed specimens is from the area studied by Bloomer and Werner (1955), and three are from the area studied by Reed (1955) (fig. 1). The analyses are presented in the accompanying table. Uncertainties in the minor- element analyses are large, but the data are included for comparison with the minor-element analyses published by Bloomer and Bloomer (1947 ). REED Composition of four samples of greenstone from the Catoctin For- mation in Virginia [Major oxides by standard rock analysis, Christel L. Parker, analyst; minor ele- ments by semiquantitative spectrographic analysis, J. C. Hamilton, analyst] Sample Constituent 1 2 3 4 Average of Major oxides (in weight percent) SiOz __________ 45. 27 48. 91 46. 00 48. 08 47. 1 A1203 __________ 14. 38 14. 86 14. 86 14. 08 14. 5 Fezog _________ 6. 55 6. 53 6 52 3 13 5. 7 e0 __________ 8. 28 6. 84 9. 05 7 58 7. 9 MgO __________ 6. 00 5. 70 6. 91 5 83 6. 1 08.0 __________ 5. 95 6. 35 4. 87 9 01 6. 5 NazO _________ 4. 58 4. 45 4. 57 3 90 4. 4 20 __________ . 55 . 63 . 12 88 . 5 H20+ ________ 3. 24 2. 89 3. 81 2. 93 3. 2 20- ________ . 13 . 11 . 12 09 . 1 T102 __________ 4. 09 2. 27 2. 63 1. 97 2. 7 205 __________ 56 . 26 . 31 . 20 . 3 MnO __________ 33 . 22 26 20 . 25 002 ___________ 09 . 03 02 2 18 . 6 Cl ____________ 01 . 01 01 00 . 01 F _____________ 07 . 04 04 05 . O5 Subtotal--- 100. 08 100. 10 100. 10 100. 11 Less O---- .03 .02 .02 .02 Total _____ 100. 05 100. 08 100. 08 100. 09 Minor elements (in weight percent)1 Ba ------------ 0. 03 0. 05 0. 01 0. 05 Be ------------ . 0001 0 0 0 Co ------------ . 005 . 005 . 005 005 Cr ------------ . 007 . 015 . 005 .015 Cu ----------- . 0005 . 015 . 02 . 007 Ga ----------- . 003 . 002 . 003 . 003 La ------------ . 003 0 0 0 Nb ----------- 0 0 . 001 0 Ni ------------ . 005 . 005 . 005 . 007 So ------------ . 003 . 005 . 005 . 005 Sr ------------ . 05 . 015 . 01 . 02 V ------------- . O7 . 05 . 05 . 05 Y ------------- . 005 . 005 . 005 . 003 Zr ------------ .015 .01 . 01 .007 Minerals (visually estimated volume percent) Albite --------- 35 40 40 35 Chlorite ------- 35 20 30 25 Epidote ------- 5 10 <1 15 Actinolite ______ 5 -------- < 1 10 Pyroxene ------ <1 20 20 -------- Magnetite ----- 10 5 5 5 Sphene and leucoxene_ _ - _ 10 5 5 5 Carbonate _____ <1 ---------------- 5 1 Results are reported in percent to the nearest number in the series I1, 0.7, 0.5, 0.3, 0.2, 0.15. and 0.1, etc.. which represent approximate midpoints of group data on a geometric scale. The assigned group for semiquantitative results will include the quantitative value about 30 percent of the time. Elements looked for and not detected: Ag, As, Au, B, Bi, Cd, Ce, Ge, Nf, Ng, In, Li, Mo, Pd, Pt, Re, Sb, Sn, Ta, Te, Th, Tl, U, W, Zn, Pr, Nd, Sm, Eu. C71 1. Fine-grained schistose greenstone containing ragged laths of cloudy albite as much as 0.5 mm long and a few grains of partly chloritized pyroxene in a felted mosaic of chlorite, actinolite, epidote, magnetite, Sphene, and carbonate. Pla- gioclase is finely twinned and some is faintly zoned. A faint relict texture is preserved. Cleavage is defined by alinement of albite laths, actinolite, and chlorite and mag- netite aggregates. The rock is cut by a few irregular veinlets of coarse epidote and carbonate. Collected from roadcut on east side of US Highway 250, 0.3 mile north of interchange with the Blue Ridge Parkway in Rockfish Gap, Waynesboro quadrangle, Virginia. See Bloomer and Werner (1955, pl. 1), and Dietrich and Lowry (1955, p. 35). Field No. 63 SNP—l; USGS Lab. No. D 100118. 2. Massive porphyritic greenstone with well preserved relict in- tergranular texture consisting of albite laths 0.5 mm long and partly chloritized pyroxene about 0.25 mm in diameter in a matrix of chlorite, epidote, magnetite, and sphene. Scattered plagioclase phenocrysts (now albite) as much as 5 mm long. Collected from roadcut on east side of Skyline Drive, 0.75 mile S. 35° W. of summit of Hawksbill, Stony Man quadrangle, Virginia. See Reed (1955, pl. 1, and pl. 2, fig. 4). Field N0. 63 SNP—2; USGS Lab. No. D 100119. 3. Massive greenstone with well-preserved relict intergranular texture consisting of albite laths 0.25 to 0.5 mm long and partly chloritized pyroxene in a matrix of chlorite, magne- tite, Sphene, and leucoxene. A few phenocrysts of plagio- clase (now albite) as much as 2 mm long. Collected from roadcut on east side of Skyline Drive, about 200 feet south of sample 2. See Reed (1955, pl. 1). Field No. 63 SNP—S; USGS Lab. No. D 100120. 4. Fine-grained schistose greenstone displaying conspicuous col- umnar jointing. Felted microcrystalline mosaic of albite, chlorite, epidote, actinolite, carbonate, magnetite, Sphene, and leucoxene, containing a few laths of albite and small grains of pyroxene, but displaying no relict texture. Cliff on east side of the Appalachian Trail 0.15 mile northeast of Hawksbill Gap, Stony Man quadrangle, Virginia. See Reed (1955, pl. 1). Field No. 63 SNP—4; USGS Lab. No. D 100121. The variation diagrams on figure 2 compare the ana— lyzed Catoctin greenstone with published analyses of unmetamorphosed basalt and with average compositions of tholeiitic basalt, olivine basalt, and theoleiitic ande- site given by Nockolds (1954). The tholeiitic basalt of the Columbia Plateau is chosen for comparison be- cause its field relations and petrography are similar to those inferred for the Catoctin lavas in the Luray, Va., area (Reed, 1955), and because modern analyses illus- trating the range of variation within geographic and stratigraphic subdivisions are available (Waters, 1961; Hamilton, 1963). The proportions of silica, alumina, magnesia, and potash in the Catoctin greenstone are in the same range as in the Columbia River Basalt and most closely resemble those of the Picture Gorge flows of Waters (1961). The content of titania and total iron oxides is higher in some of the Catoctin analyses, but the most striking difl'erences are the consistently higher pro- portion of soda and consistently lower proportion of C72 WEIGHT PERCENT OF OXIDES CaO A1203 FeO +Fe203 MgO NaZO K20 Tio2 MINERALOGY 18— l— "\' 17 / \ . lee l ' \ \03 Cl \ 02 15‘ 01 \ / A‘ \14 14~ /~\ X / \\ 13— \\_'_,/+ 12 I I I | I I J 17— 3 + 16— 0 15 01 -~ r l/ . \\ 14— \\_QZ/ 13» . . /\ 12— A (// X lie \_/°454 10 | | I I 1 4| 10— 9 A 8— (\ 7» \03 \ 1 \.\u \ X 6_ 0 04/ 2 . .+. 5— —-——~\ 4 l I“‘i~—+ 12~ 11— /\\ A f C,\ x 10~ ‘ \\‘/) . 9— . (\“F + \ \Iv<_’_\; 8— 7— 1 4 02 6— O O r. l I n3 I | I I J 5— 01 03 O2 4 4— o 3 ,a/‘E:T\\'\_,:i' I ~ «— SI 2 | | T IX | J Zfi (iii—“Z; 1— a 1 _Q4 “3x A O r_./ \O- 0 I I\-h3-—I3/l‘21 I I 5— 1 4_ 0 (‘\~ 2 \\ .o\\ 3— A O3 \‘\\ ‘I A ' 4 . "+ 2— ’—~\ 0 .>< L\ F - 1 \\‘ o I I l I I I I I I I 42 43 44 45 46 47 48 49 50 51 52 53 SiOz, IN PERCENT AND PETROLOGY lime in the Catoctin greenstone. The wide range in composition among the basalts of the Columbia Plateau shows that comparison of a small number of analyses with worldwide averages such as those of Nockolds (1954) is probably inconclusive. The general chemical similarities between the analyzed greenstone and basalt of the Columbia Plateau is consistent with the conclu- sion that the greenstone is derived from tholeiitic basalt, as was suggested by Reed (1954) on the basis of field and petrographic evidence. However, the chemical data are insufficient to conclusively distinguish them from oli— vine basalt or tholeiitic andesite, especially in View of the lack of knowledge of possible changes in bulk com- position during metamorphism. The NazO/CaO ratios of the analyzed Catoctin greenstone are very different from those of normal basalt or andesite and show that chemically the greenstone is spilite, as first suggested by Bloomer (1950). The spilitic character of the greenstone is evidently not a result of submarine eruption, because three of the analyses are from the area where Reed (1955) has shown that the flows were subaerial. Spilitization ap- parently is related to low—grade regional metamor- phism, and may have resulted either from introduction of soda from an outside source, or from metamorphic segregation within the volcanic sequence during which soda was concentrated in the greenstone and lime segre- gated in the epidosite pods, quartz-epidote veins, and amygdule fillings. EXPLANATION o1 ‘t Average of 26 tholeiitic andesites (Nockolds, 1954) Greenstone of the Catoctin Formation (Number refers to samp/e [n rah/e) Columbia River Basalt from A Riggins quadrangle, Idaho Average of 96 samples of (Hamilton, 1963) olivine basalt (Nockolds. ,_‘___ 1954) \ _-_,_> Average and range of late Yakima and Ellensburg flows, Columbia River Basalt (Waters, 1961) A Average olivine basalt from the Snake River Plain (Waters, 1961) ”:1?) X Average and range of Picture Gorge flows, Columbia River Basalt (Waters, 1961) Average of 137 samples of tholeiitic basalt (Nockolds, 1954) FIGURE 2.—Variation diagrams showing the weight percentage of oxides in greenstone of the Catoctin Formation compared with the percentage in unmetamorph'osed basalt. material. Analyses recalculated free of 051003 and volatile REED REFERENCES Bloomer, R. 0., 1950, Late Pre—Cambrian or lower Cambrian formations in central Virginia: Am. Jour. Sci., v. 248, p. 753-783. Bloomer, R. 0., and Bloomer, R. R., 1947, The Catoctin forma- tion in central Virginia: Jour. Geology, v. 55, p. 94—106. Bloomer, R. 0., and Werner, H. J., 1955, Geology of the Blue Ridge region in central Virginia: Geol. Soc. America Bull., v. 66, p. 579—606. Brown, W. R., 1958, Geology and mineral resources of the Lynch'burg quadrangle, Virginia: Virginia Div. Mineral Resources Bull. 74, 99 p. Dietrich, R. V., and Lowry, W. D., 1955, Geological features along U.S. Routes 11, 29 and 250 in Virginia, pt. II, Wash- ington, DC, and Point of Rocks, Maryland, to Staunton, Virginia, in Russell, R. J., ed., Guides to southeastern geology: Geol. Soc. America, p, 29—42. Furcron, A. S., 1934, Igneous rocks of the Shenandoah National Park area: J our. Geology, v. 42, p. 400-410. ’X‘ C73 Hamilton, Warren, 1963, Columbia River Basalt in the Riggins quadrangle, western Idaho: US. Geol. Survey Bull. 1141—L, 37 p. Keith, Arthur, 1894, Geology of the Catoctin belt: U.S. Geol. Sur- vey 14th Ann. Rept., pt. 2, p. 285—395. Nelson, W. A., 1962, Geology and mineral resources of Albemarle County: Virginia Div. Mineral Resources Bull. 77, 92 p. Nickelsen, R. P., 1956, Geology of the Blue Ridge near Harpers Ferry, West Virginia: Geol. Soc. America Bull., v. 67, p. 239—207 . Nockolds, S. R., 1954, Average chemical compositions of some igneous rocks: Geol. Soc. America Bull., v. 65, p. 1007— 1032. Reed, J. 0., Jr., 1955, Catoctin formation near Luray, Virginia :. Geol. Soc. America Bull., v. 66, p. 871—896. Virginia Division of Mineral Resources, 1963, Geologic map of Virginia: scale 1: 500,000. Waters, A. C., 1961, Stratigraphic and lithologic variations in the Columbia River Basalt: Am. J our. Sci. v. 259, p. 583- 611. GEOLOGICAL SURVEY RESEARCH 1964 OCCURRENCE AND ORIGIN OF LAUMONTITE IN CRETACEOUS SEDIMENTARY ROCKS lN WESTERN ALASKA By J. M. HOARE, W. H. CONDON, and W. W. PATTON, JR., Menlo Park, Calif. Abstract—Laumontitized sedimentary rocks of Cretaceous age which are easily recognized by their distinctive mottled or spotted appearance crop out over an area of at least 2,000 square miles in western Alaska. Most of the laumontite is thought to have formed diagenetically through the reaction of water rich in calcium carbonate with tufiaceous material of acid or inter- mediate composition. In the course of regional mapping in western Alaska, laumontitized 1 sandstones have been mapped over an area of at least 2,000 square miles. This is probably the largest known occurrence of this calcic zeolite in North America. Deposits of similarly zeolitized sedimentary rocks of probable comparable size have been recognized in Russia (Zaporozhtseva, 1960). The zeolitized rocks discussed here form part of a thick sequence of elastic sedimentary rocks which were deposited in the Koyukuk geosyncline (fig. 1) in mid—Cretaceous (Al- bian and Cenomanian?) time. Geophysical data indicate that the sedimentary sec- tion in the deeper parts of the geosyncline may be as much as 20,000 to 30,000 feet thick. The section consists of dark-gray, fine-, med-ium-, and some coarse-grained graywacke sandstones interbedded with equal or greater amounts of siltstone and shale. In the southwestern part of the geosyncline this thick sequence of rocks can be divided into three mappable lithologic units on the basis of whether the sandstones are calcareous, non- calcareous, or laumontitized (fig. 2). Most of the rocks mapped as calcareous effervesce freely when treated with cold dilute hydrochloric acid, but many rocks in the unit are noncalcareous or slightly calcareous. Con- versely, the rocks mapped as noncalcareous include some rocks that are at least weakly calcareous. The laumon- 1 The ideal, alkali-free formula for laumontlte ls Ca4AlgSlmO4S - 161120 (Coombs, 1952, p. 825) ; however, it usually also contains some sodium and potassium. 156°00' 152°00’ 164°00’ 160°00’ Modified after Payne, 1955 O 50 100 MILES L_—I—A EXPLANATION Laumontitized sedimentary rocks Boundary of tectonic element FIGURE 1.—Map showing occurrence of laumontitized sedimen- tary rocks in west-central Alaska. titized unit contains an equal or greater amount of cal- careous and noncalcareous sandstone that contains little or no laumontite. The thickness of the laumontitized strata cannot be determined accurately because the US. GEOL. SURVEY PROF. PAPER 501—0. PAGES 074-078, C74 C75 HOARE, CONDON, AND PATTON 162'-oo' SOUND NOR TON \\ ALASKA \ EXPLANATION >K WDOUU CLAY»SIZE FRACTION —100 Upper part ———200 8‘ Clay, calcareous, red, yellow, and brown. with - lenses of fine-grained sand and sandy clay I? 5 —300 a. c o E :I In 0 an —400 m R c a.) o 0 ti 9 r '6 500 f 0—. . Alta Lorna sand of Rose, 1943, fine-to < medium-grained, 600 well-sorted, massive ‘ —700 c o .5 i“ Alternating lenses of i E sand, sandy clay, and 800 Le clay; sand, fine—to a) medium-grained '5 .2 _l ———900 EXPLANATION V i j - [:1 . Total depth _ __ _ _ Montmorillonite Illite Chlorite and 963 kaolinite FIGURE 2.—Electric log, lithology, and clay mineralogy of the sediments penetrated by NASA core hole B—S—l, Clear Lake, Harris County, Tex. The cores, taken with a double-tube Dension core bar- rel, were stored in air-tight jars. Samples from eight selected fine-grained sections of the core were prepared as follows : (1) Five grams of sample was placed in 150 millili- ters of distilled water, stirred briefly, and dispersed in an ultrasonic generator for about an hour (no chemical dispersing agent added) . Lithologic descriptions from Pettit and Winslow (1957). (2) Concentrated slurries of two siie fractions—0.1 to 0.2 and 0.2 to 2.0 microns—were separated out by centrifuging. (3) The slurries were placed on finely porous ceramic slides by means of a dropper, and the water was sucked out through the slide by a vacuum pump. This produced an aggregate of clay-mineral particles oriented with their basal surfaces parallel to the slide. CORLISS AND MEADE C81 Basal X-ray-refiectian criteria used to identify clay minerals Treatment of sample Criteria for clay-mineral identification after various steps of treatment Montmorillonite Illlte Chlorite Kaolinlte Broad reflections at 15 A and 5.0 A ; diffuse band 3.1—3.3 A. 15-A reflec- tion much more intense Air drying ___________ Integral series related to 9.9 A: 5.0 A, 3.3 A 5.0—A reflection less intense than the Reflections at 7.0—7 .1 A and 3.5 A 3.5 A reflection is separated slightly from the cor- Integral series related to 14 A: 7 A, 4.7 A, 3.5 A. 7-A and 3.5 A reflections much more intense than than the others. other two. the others. 14—A reflec- responding chlorite tion obscured by mont- reflection. morillonite reflection. Exposing to ethylene Integral series related to _____ do ____________________ do ___________________ Do. glycol. 17 A: 8.5 A, 5.6 A, 3.5 A. 17-11 reflection much more intense than the others. Heating at 400°C for Nearly integral series re- As above, presumably: As above, except that faint Do. 1 hour. lated to 9.8 or 9.9 A: reflections obscured reflection at 14 now 5.0 A, 3.1~3.3 A. by montmorillonite visible. reflections. Heating at 550°C for _____ do ______________________ do _______________ 14-A reflection enhanced; No reflections. 1 hour. other orders absent. These oriented aggregates were then treated in four steps: (1) Dried in air, (2) Exposed to ethylene glycol vapors at 60°C for 1 hour, (3) Heated to 400°C for 1 hour, and (4) Heated to 550°C for 1 hour. After each step, an X-ray diffraction pattern was run using a Norelco difi'ractometer with a Brown linear recorder. These diffraction patterns were examined to identify the clay minerals present and to estimate their relative proportions. The criteria used in identifying the min- erals are listed in the accompanying table. Tentatively it is assumed that the relative proportions of the clay minerals in a sample are represented by the ratios of the intensities (areas) of certain selected reflections on the diffraction patterns of the sample. The estimated relative proportions of montmorillonite and illite are determined by comparing the intensities of the 9.9-A (angstrom units) reflections before and after heating to 400°C. Chlorite and kaolinite are considered to- gether because their reflections coincide, making it diflicult to differentiate them quantitatively. The esti- mated ratio of Chlorite and kaolinite to illite is deter- mined by the ratio of the intensities of the 7-A and IO-A reflection after the ethylene-glycol treatment. The estimated average composition of the 0.2—2.0“ fractions of all 8 samples is 65 percent montmorillonite, 15 percent illite, and 20 percent Chlorite plus kaolinite. The composition of the finer 0.1—0.2}; fraction is similar to that of the coarser 0.2—2.0” fraction (given in fig. 2), except for a slightly larger proportion of montmoril- lonite in the finer size fraction of most of the samples. The Layne-Texas 00., under supervision of McClel- land Engineers, Inc., drilled the core hole for the U.S. Army Corps of Engineers, who in turn made the cores available for the clay-mineral studies. We are grateful to Leonard A. Wood of the US. Geological Survey who arranged for transmittal of the cores, supplied back- ground material for the illustrations, and reviewed the article. REFERENCES Pettit, B. M., J r., and Winslow, A. G., 1957, Geology and ground- water resources of Galveston County, Texas: U.S. Geol. Survey Water-Supply Paper 1416, 157 p., 23 p1s., 13 figs. Rose, N. A., 1943, Progress report on the ground-water resources of the Texas City area, Texas: Texas Board Water En- gineers, duplicated rept. Winslow, A. G., and Doyel, W. W., 1954, Land-surface subsidence and its relation to the withdrawal of ground water in the Houston—Galveston Region, Texas: Econ. Geology, v. 49, no. 4, p. 413—422. Winslow, A. G., and Wood, L. A., 1959, Relation of land sub- sidence to ground-water withdrawals in the upper Gulf Coast region, Texas: Mining Engineering, v. 11, no. 10, p. 1030—1034. GEOLOGICAL SURVEY RESEARCH 1964 ATTAPULGITE FROM CARLSBAD CAVERNS, NEW MEXICO By WILLIAM E. DAVIES, Washington, DC. Abstract—The clay mineral attapulgite occurs in well- cemented cave fill found in a maze of small- solution pockets and tubes in the Lower Cave, Carlsbad Caverns, N. Mex. Two varities of clay are present: gray to olive-green clay, mainly montmorillonite ; and pink cl‘ay composed of approximately equal parts of attapulgite and montmorillonite. Both varieties are found in the same area, grade one into another, and contain as much as 15 percent quartz. The pink clay contains 32 percent calcite, which forms a strong bond that prevents dispersion. The gray clay disperses readily. Attapulgite, general composition (0H2)4 (OH)2 Mg58i3020'4H20, is a clay mineral commonly associated with soils derived from limestone; however, its presence in cave deposits has not been reported previously. In 1956 a deposit of well-cemented, fine—grained cave fill was examined in the Lower Cave, Carlsbad Caverns, N. Mex. This deposit had been previously described (Good, 1957), but the clay minerals were not identified. The clay occurs in a maze of small solution pockets and tubes about 150 meters east of the old ladder entrance to Lower Cave. The clay in the tubes and pockets originally filled the openings completely, but shrinkage and slumping have left small voids between the clay and the roof of the pockets. The clay is broken by irregular fractures into fragments 5 to 15 centimeters on a side. The deposit contains two kinds of clay which are easily distinguished by their color: one is pink and the other gray to olive green. Both varieties occur in the same locality and commonly grade one into another. The pink clay is dense, hard, and breaks with a conchoidal fracture. It is very resistant to crushing and fracturing and with- stands the repeated blows of an ordinary geologic pick. Attempts to disperse the pink clay in water were to no avail. Samples left in water at room temperature for 2 years absorbed no water, and the strength of the clay was not altered. The green clay dispersed readily in water, forming small silt-sized flakes. Laboratory tests showed that the pink clay contained 32 percent calcite, which apparently acted as a cement, thereby preventing dispersal of the clay. After re- moval of the calcium carbonate by dissolving it in hydrochloric acid, the insoluble residue consisted pri- marily of clay (85 percent) with small proportions of silt and sand (15 percent). N0 heavy minerals were observed in the clay. X-ray examination of the silt (62—2M) and the clay (<2p.) fractions of the acid-in- soluble material showed the following minerals (esti- mate of quantities are based on the relative intensities of the diffracted lines) : Mineral Parts in ten Attapulgite __________ 5 Montmorillonite _____ 4 Kaolinite( ?) ________ Trace Quartz ______________ Trace Feldspar ____________ Trace In the silt-sand fraction the composition is estimated as follows: Mineral Parts in ten Quartz ______________ 5 Attapulgite __________ 3 Kaolinite( ?) ________ 1 Feldspar ____________ Trace Additional examination with an electron microscope confirmed the presence of attapulgite and showed that the attapulgite in the silt—sand fraction consists of ag- gregates of very fine grained fibers. The pink clay (before removal of calcium carbonate) had the following engineering properties: 89 percent1 45 percent1 Liquid limit ________________________________ Plastic limit _______________________________ Field moisture equivalent ___________________ 123 percent ‘ Shrinkage limit ____________________________ 8 percent 1 Shrinkage ratio ____________________________ 21 Specific gravity ____________________________ 2. 20 1 Moisture content in percent of dry unit weight. Compared with attapulgite not containing calcite (White, 1949) these values are low. Plastic limit is generally in the order of 116 percent and liquid limit 177 percent. U.S. GEOL. SURVEY PROF. PAPER 501-C, PAGES CSZ-C83 082 DAVIES The gray to olive-green clay consists of montmoril- lonite, quartz, a small amount of halloysite, and some disordered kaolinite. Calcite was not detectable. The occurrence of the clays gives some clue to their origin. The pink clay occurs in an exposed position where small phreatic tubes connect with larger pas- sages. The gray to olive-green clay occurs in phreatic tubes behind the pink clay. It is probable that the development of attapulgite and the cementation by cal- cite in the exposed clay occurred during a period when the Lower Cave was inundated by waters rich in carbonates. Of possible practical importance is the strong cemen- C83 tation imparted to the clay by the calcium carbonate present in the raw sample. Such bonding, where at- tapulgite is present, may be applicable as a simple, cheap means of stabilizing clay surfaces. Laboratory identification of the attapulgite from the Carlsbad Caverns was made by John C. Hathaway and Dorothy Carroll, US, Geological Survey. REFERENCES Good, J. M., 1957, Noncarbonate deposits of Carlsbad Caverns: Natl. Speleological Soc. Bull. 19, Oct., p. 20. White, W. A., 1949, Atterberg plastic limits 0f clay minerals: Am. Mineralogist, v. 34, no. 7—8, July—Aug, p. 508—512. GEOLOGICAL SURVEY RESEARCH I964 DIAGRAM FOR DETERMINING MINERAL COMPOSITION IN THE SYSTEM MnCO,—CaCO,—M9COJ By WILLIAM C. PRINZ, Washington, DC. Abstract—In the system MnGOs—C‘aOOa—MgCOa, index of re- fraction increases toward M11003 and the spacing of the strong- est X-ray line ((1 (211;) increases toward CaCOa. Variations in these properties are combined to produce a diagram for deter- mining the composition of relatively iron-free minerals in the system. In the system MnCOa—CaCos—MgCOa, index of re- fraction increases toward MnCO3 and the spacing of the strongest X-ray line (03 1211;) increases toward CaCOa. Variation in the index of refraction of. the ordinary ray with composition in the system has been presented by Wayland (1942, pl. 1), and Winchell and Winchell (1951, fig. 61); Goldsmith and Graf (1960, fig. 6) show the variation in the spacing of the d {211; plane. These data are here combined (fig. 1) and yield a useful chart for determining the composition of min- erals within the system. A similar diagram for deter- mining the composition of dolomite containing as much as 10 percent FeCOa has been published by Zen (1956, fig. 1) . Variation in the spacing of the d 4211} plane with com- position in the series MnCO3—Ca003 has also been de- termined by Erenburg(1959), and a chart for deter- mining composition in the system CaCOa—MgCOg by X-ray methods has been presented by Harker and Tut- tle (1955, p. 277, fig. 2). Data in both these papers agree closely with those given by Goldsmith and Graf (1960) and shown here (fig. 1). Natural material is lmown from the calcite half of the series MnCOg-CaCOa, but except at high tempera tures, a gap exists between CaMn(COa)2 and MnC‘Oa. The series MnCO3—Mg003 is continuous (Goldsmith and Graf, 1960), but natural material is rare. That the MgCO3—Ca003 series is discontinous is well known. Iron carbonate, which when pure has n0=1.875 and d {m} =2.7 91 A, is the most common other phase that occurs in this system; its presence in a mineral would cause the composition as shown by the diagram (fig. 1) CaCO3 Calcite 9" A cog, :s .1" bd ‘1‘ 2 as \\ (9% 9-90 \ \f‘Ib CaMg (003)2' \\ \\ CaMn(COa)2 Dolomite ’ \\ Kutnahorite MgCOa Magnesite Mn003 Rhodochrosite FIGURE 1.—Variation in index of refraction of the ordinary ray (av—solid lines) and spacing (in angstrom units) of the strongest X-ray line ((1 ram—dashed lines) with composition (molecular percent) in the system MDOOrGaCOx-Mg‘COa. X-ray data from Goldsmith and Graf (1960, fig. 6) ; optical data from Wayland (1942, pl. 1) and Winchell and Winchell (1951, fig. 61). to be displaced toward the MnCOa and MgCO3 corners. Data presented by Zen (1956) and Howie and Broad- hurst (1958) for dolomite and ankerite and by Frondel and Bauer (1955) for kutnahorite suggest that the ac— curacy of the diagram around dolomite and kutna- horite is good if the amount of FeCOs in the mineral is less than 1 percent, that it is usable but less reliable if the amount is 2 percent, and that accuracy would be poor for samples containing more than 3 percent FeCOs. A search of the literature for analytical data to check the validity of other parts of the diagram proved unre- U.S. GEOL. SURVEY PROF. PAPER 501—0, PAGES CS4—C85 084 PRINZ warding. Most papers give composition and index of refraction but not X-ray data. Published analyses that give both are generally of relative pure end members in the system; these data fit very well. Both index of refraction of the ordinary ray and the spacing of the strongest X-ray line are easily and quickly measured, so the diagram should prove useful in determining the composition of relatively iron—free minerals in the system. Perhaps with more data it will be possible to refine this diagram and to construct similar ones to include FeCOa. REFERENCES Erenburg, E. G., 1959, Continuous isomorphism in the OaCOr MnCOs system: Russian Jour. Inorganic Ohemistry (trans— lation of Zhurn. Neorg. Khim.), v. 4, p. 859—861. CS5 Frondel, Clifford, and Bauer, L. 11., 1955, Kutnahorite, a man- ganese dolomite, GaMn(003)z: Am. Mineralogist, v. 40, p. 748—760. Goldsmith, J. R., and Graf, D. L., 1960, Subsolidu-s relations in the system CaCOa—MgCOa—MnCOa: Jour. Geology, v. 68, p. 324—335. Harker, R. 1., and Tuttle, O. F., 1955, Studies in the system CaO—MgO—002: Am. Jour. Sci., v. 253, p. 209—224, 274—— 282. Howie, R. A., and Broadhurst, F. M., 1958, X-ray data for dolomite and ankerite: Am. Mineralogist, v. 43, p 1210— 1214. Wayland, R. G., 1942, Composition, specific gravity, and refrac- tive indices of rhodochrosite from Butte, Montana: Am. Mineralogist, v. 27, p. 614—628. Winchell, A. N., and Winchell, Horace, 1951, Elements of optical mineralogy, pt. 2. descriptions of minerals, 4th ed.: New York, John Wiley and Sons. Zen. E-an, 1956, Correlation of chemical composition and physi- cal properties of dolomite: Am. J our. Sci, v. 254, p. 51—60. GEOLOGICAL SURVEY RESEARCH 1964 LITHIUM ASSOCIATED WITH BERYLLIUM IN RHYOLITIC TUFF AT SPOR MOUNTAIN, WESTERN JUAB COUNTY, UTAH By DANIEL R. SHAWE, WAYNE MOUNTJOY, and WALTER DUKE, Denver, Colo. Abstract—Lithium content of bedded rhyolitic tufl is un- usually high at the Roadside beryllium deposit, Spor Mountain, Utah. LizO averages 0.22 percent in 18 representative samples and is concentrated in clay fractions during sizing. It is prob- ably present chiefly in montmorillonite. Though perhaps not of economic importance by itself, the lithium may well be abun— dant enough to be a byproduct if the deposit is worked for beryllium. Unusually large amounts of lithium have been de— tected in samples from a beryllium deposit in bedded rhyolitic tuff at the Roadside claims, Spor Mountain, in western J uab County, Utah. The rhyolitic tufi' con- tains numerous crystals of quartz and sanidine, and pebbles of carbonate rock. The tufl' is hydrothermally altered and as a result also contains opal, chalcedony, montmorillonite, calcite, fluorite, manganese oxide, and bertrandite (Be4Si207(OH)2) ('Staatz, 1963, p. M27). LiZO content ranges from 0.04 to 0.43 percent; its aver— age Value is 0.22 percent in 18 samples that are represent- ative of tufl' exposed in a pit dug to develop the beryl- lium deposit at the south end of the Roadside No. 5 claim. The LizO content and Boo content of the 18 samples are given in table 1. Several of the samples contain very little beryllium, yet carry appreciable lithium, indicating that lithium mineralization was more widespread than beryllium mineralization. Lithium was determined by a flame photometric meth- od, employing a standard-addition technique similar to that described by Grimaldi (1960). The sample was completely dissolved by digestion in hydrofluoric and perchloric acids, thus facilitating accurate determina- tion of lithium. The lithium probably is in montmorillonite, Which IS the only clay mineral recognized in the Spor Mountain beryllium deposits according to Staatz and Griflitts (1961, p. 946) and Staatz (1963, p. M28). This View is supported by the data of table 2 which show that the lithium is most abundant in the clay-size fractions of TABLE l.—Li20 and BeO analyses of 18 samples from the Roadside [Lao determined by flame photometer method by Wayne Mountjoy, 1963. No. 5 claim BeO determined by photo-neutron activation method by Walter Duke, 1963] Sample No. Laboratory No. Field N 0. mm (percent BeO (percent by weight) by weight) 1 ________ D111323_ _ _ DRS—27—63_-- 0. 25 0. 84 2 ________ D111324- _ _ DRS—28-63--- .32 1.07 3 ________ D111325_ - _ DRS—30—63--- .27 1.25 4 ________ D111326_ _ _ DRS—31—63_-- .19 . 10 5 ________ D111327_ _ _ DRS—32—63--- . 11 . 56 6 ________ D111329___ DRS—34—63_-- .16 .016 7 ________ D111330- _ _ DRS—35—63__- .23 .011 8 ________ D111332___ DRS—37—63--- . 30 1. 05 9 ________ D111333- _ _ DRS—38—63--_ .08 1. 00 10 _______ D111334- _ _ DRS—39—63--_ .18 .15 11 _______ D111335_ _ _ DRS—40—63_-- .07 .073 12 _______ D111337- _ _ DRS—42—63___ .08 .005 13 _______ D111339_ _ _ DRS—44—63_-- . 28 . 70 14 _______ D111343- - - DRS—48—63__- . 04 . 41 15 _______ D111371_-- DRS—76—63_-- .35 1.15 16 _______ D111379___ DRS—84—63--- .36 .81 17 _______ D111388- _ _ DRS—93—63--- .43 .008 18 _______ D111389--- DRS—94—63__- .28 12 TABLE 2.—Li20, BeO, and F analyses of two samples, and Li20 and F analyses of three size fractions of the two samples, Road- side No. 5 claim [L120 determined by flamce‘fihotometerD method by Wayne Mountjoy, 1963. Fluorine determined volumetri y byW 0058, 1963. BeO determined by photo— neutron activation method by Walter Dbuke, 1963] Sam- LIaO F BeO ple Laboratory Field N 0. Approximate size (per- (per- (per- No. No. range (diameter) cent by cent by cent by weight) weight) weight) 1_-- D112129_ DRS—30— (Total 0. 24 1. 34 l. 25 63. sample) 2--- D112130_ DRSa30— >0.05mm . 12 . 76 _____ 63 . 3- _- D112131_ DRS—30— .05mm—5u . 33 1. 87 _____ 63 4-_- D112132_ DRSfi30— <5): .39 1. 88 ----- 63 . 5_-_ D112133- DRS—Q2— (Total . 19 1. 90 .006 63. sample) 6_-- Dll2134- DR8692— >.05mm .13 .96 _____ 63 . 7-_- D112135- DRS—92— .05mm—5p .21 1. 17 ----- 63M. 8_-- D112136_ DRSEQ2— <5u . 38 3. 10 ----- 63 . U.S. GEOL. SURVEY PROF. PAPER 501-0, PAGES 086-087 C86 SHAWE, MOUNTJOY, AND DUKE two samples. Several published articles have called attention to the high lithium content of some mont- morillonite (1 percent Li2O in hectorite, Ross and Hen- dricks, 1945, p. 27, 35, 38), and it has been suggested that such material may become a source of lithium (Norton and Schlegel, 1955, p. 336, 341). Lithium is commonly associated with beryllium in magmatic deposits, and the same may apply to hydro- thermal deposits. Staatz and Griflitts (1961, table 1) report as much as 700 parts per million lithium (0.13 percent LiZO) locally in berylliferous fluorite nodules from the Spor Mountain area, but the amount of lith— ium shown for the Roadside samples (table 1, this article) has heretofore not been detected in the Spor Mountain beryllium deposits. A berylliferous deposit described by McAnulty and Levinson 1 in the Honey- comb Hills, similar to the deposits at Spor Mountain, and about 20 miles west has an average of about 480 ppm lithium (0.09 percent LizO) in 14 samples. 1 W. N. McAnulty and A. A. Levinson, 1963, Rare alkali and beryllium mineralization in volcanic tufts, Honeycomb Hills, Juab County, Utah: Paper presented at Geol. Soc. America Annual Meeting, New York. 5% CS7 The lithium grade of the Roadside deposit does not appear to be high enough to make the deposit economi- cally valuable for lithium alone. Conventional lithium mines in pegmatite ordinarily have at least 1.0 percent LiZO (Norton and Schlegel, 1955, p. 344). If the Road— side deposit is worked for beryllium, however, lithium is likely to be recoverable as a byproduct. REFERENCES Grimaldi, F. S., 1960, Dilution-addition method for flame spec- trophotometry: Art. 225 in U.S. Geol. Survey Prof. Paper 400—B, p. B494—B495. Norton, J. J., and Schlegel, D.M., 1955, Lithium resources of North America: U.S. Geol. Survey Bull. 1027-G, p. 325—350. Ross, C. 8., and Hendricks, S. B., 1945, Minerals of the mont— morillonite group: U.S. Geol. Survey Prof. Paper 205—B. Staatz, M. H., 1963, Geology of the beryllium deposits in the Thomas Range, Juab County, Utah: U.S. Geol. Survey Bull. 1142—M, 36 p. Staatz, M. H., and Grifiitts, W. R., 1961, Beryllium-bearing tuff. in the Thomas Range, J uab County, Utah: Econ. Geology, v. 56, p. 941—950. GEOLOGICAL SURVEY RESEARCH 1964 A GEOCHEMICAL INVESTIGATION OF THE HIGH ROCK QUADRANGLE, NORTH CAROLINA By ARVID A. STROMOUIST,1 AMOS M. WHITE,2 and JOHN B. McHUGH ‘ Work done in cooperation with the North Carolina Department of Conservation and Development, Division of Mineral Resources Abstract—Silt to clay-sized alluvium was sampled from 55 streams, each draining an area of about 2 square miles. Because transport of the alluvium has been minimal, the results of chemical analyses are considered to be areally representative. Rapid colorimetric methods of analysis indicated slight, but significant, enrichment of copper, nickel, and zinc in alluvium of the western half of the quadrangle. These results are com- patible with the pattern of mineralization as indicated by the prospects and mines near Silver Hill on the northwest, Gold Hill on the west, and Georgeville on the southwest. Stream alluvium was sampled in the High Rock quad— rangle, North Carolin-a (fig. 1), and analysed for copper, lead, zinc, nickel, tungsten, and molybdenum by rapid geochemical methods. Results of the analyses are com- parable to those of similar investigations in nearby areas. All metal values in the stream alluvium are low, but the concentration of samples having a slightly anom— alous metal content in the western part of the quad- rangle suggests a trend of increasing abundance of copper and zinc in that direction. The High Rock quadrangle is underlain by rocks of the Carolina slate belt (Laney, 1910, 1917 ; Pogue, 1910; Stuckey, 1928, Stromquist and Conley, 1959; Conley, 1962a and 1962b) and is near the faulted complex of plutonic rocks of the Charlotte belt (King, 1955) that truncate slate-belt rocks on the west (fig. 1). Rocks of the Kings Mountain belt (King, 1955, map) lie to the west of the Charlotte belt. East of the slate belt are sedimentary rocks of the Newark Group and of the Coastal Plain. Lowlands of the High Rock quadrangle range in altitude from 500 to 600 feet above sea level. Flat Swamp Mountain, the most pronounced ridge in the quadrangle, attains an altitude of 1,200 feet; other ridges and hills are as much as 800 feet high. Volcanic and intrusive rocks form the ridges and highlands of 1 Denver, Colo. 2 Washington, DC. 80° NORTH CAROLINA .\ Area of VS HIGH ROCK OUADRANGLE CONCORD QUADRANGLE CONCORD SE QUADRANGLE 35° 20 MILES EXPLANATION Rocks of the Charlotte and Kings Mountain belts (Precambrian and Paleozoic) Volcanic and sedimem tary rocks of the Carolina slate belt (Ordovician) Coastal Plain rocks (Cretaceous and younger) and Newark Group (Triassic) FIGURE 1.—Geologic sketch map of a part of south-central North Carolina, showing location of quadrangles and mining areas. Geology generalized from geologic map of North Carolina (Stuckey and Conrad, 1958) and from King (1955). Circles indicate groups of mines and prospects; letters designate area : 8, Silver Hill; G, Gold Hill; Ge, Georgeville. U.S. GEOL. SURVEY PROF. PAPER 501-C. PAGES 088-091 088 STROMQUIST, WHITE, AND MCHUGH the area, whereas sedimentary rocks constitute the low- lands. Rocks in the High Rock quadrangle comprise rhyolitic and basaltic flows and tufls interbedded with tufl'aceous argillite, and argillaceous tufl‘, all of Ordo- vician age (White and others, 1963). Gabbroic sills and stocks, probably of Paleozoic age (King, 1955, p. 349), intrude the volcanic and sedimentary rocks and occupy about 2 percent of the area. The rocks have weathered to saprolite in some places, but nowhere in the quadrangle is saprolite more than a few feet thick, and in many places the streams flow on hard rock. The thickness of saprolite in the High Rock area contrasts sharply with that in the Concord area, where Bell and Overstreet (Bell and Overstreet, 1960; Overstreet and Bell, 1960) report saprolite developed to depths of 125 feet. The geochemical analyses were made on samples of fine-grained alluvium from 55 small streams, each draining an area of 2 square miles or less, whose drain— age basins cover 63 percent of the quadrangle (fig. 2). Each sample consisted of about 100 grams of clayey and silty alluvium taken upstream from the flood plains of the principal streams into which the 55 streams emptied. The sampling of small drainage basins limits the source of metals in the alluvium to the basin sampled. Except in areas of pervasively fractured rocks, ground water probably has distributed dissolved solids only short distances in rocks of the Piedmont province in North Carolina, for according to LeGrand (1958, p. 179), “The linear distance between the point where a drop of water first reaches the water table and the point where it is discharged at a spring or seepage area is almost every— where less than a mile, and commonly less than half a mile.” According to Hawkes (1957, p. 306) a clay sam- ple, rather than sand or gravel, is likely to have ad- sorbed metallic ions from the water in which it was transported. Colorimetric field methods of chemical analysis (Ward and others, 1963) Where used by John B. McHugh and W. W. J anes of the US. Geological Survey in determining the abundance of copper, lead, zinc, nickel, tungsten, and molybdenum in the 55 silt and 089 clay samples. The methods are sensitive, rapid (as many as 30 determinations per day), and accurate to :30 percent. . Figure 3 shows the frequency distribution of the ele- ments looked for. Copper was reported to the nearest 10 ppm, and lead, zinc, and nickel were reported to the nearest 25 ppm. All 55 samples werebelow the limits of detection with respect to molybdenum (<4 ppm) and tungsten (<20 ppm) ; most were below the limits of detection with respect to lead (<25 ppm). Hence results for molybdenum, tungsten, and lead are not significant. With respect to nickel, two samples con— tained at least 50 ppm and one contained 75 ppm (fig. 3) ; all three samples came from near the northwest cor— ner of the quadrangle (fig. 2). Because of this cluster- ing of the nickel “highs” these results have been con- sidered of “odd” significance and are shown on figure 2. The arithmetic mean of the results for zinc is about 50 ppm and that for copper is slightly more than 30 ppm (fig. 3). Figure 2 indicates, with chemical sym- bols, those basins in which the alluvium sampled con- tains at least 75 ppm zinc and 40 ppm copper. On the basis of an analytical error of i 30 percent, 75 ppm zinc is a boderline “anomaly” and a result of 40 ppm copper could be a submarginal one. Nevertheless, these ques- tionable small anomalies indicate a slight metal enrich— ment in the western half of the quadrangle (fig. 2) and suggest a trend of increasing mineralization northward, Westward, and southwestward, toward the mines and prospects clustered about Georgeville, Gold Hill, and Silver Hill (fig. 1). What relations, if any, the pattern of metal enrichment may bear to the south-plunging anticline shown on figure 2 is obscure. This fold has a wave length of about 10—12 miles and projects toward the Gold Hill district. Although this article reports only the preliminary re- sults of a geochemical study in the High Rock quad- rangle, the authors believe that study of a larger area in this part of North Carolnia will bear out more strongly the trends shown here. 090 GEOCHEMISTRY 80°15, 80°07’30” 35°37’30" : . . ,..‘. 'BAsA'LngXTROCKs: \_ '_ '. ROV_V_AN ', COU_I~_ITY, 4 _ ".'.STANLY ,' .' COUNTY. n 35°3o' 0 1 2 MILES I FIGURE 2.——Geochemical map of High Rock quadrangle, North Carolina, showing generalized lithology and the major geologic structure. Stippled areas are sampled drainage basins; heavy stipple designates basins in which samples contain at least 40 ppm copper (Cu), 75 ppm zinc (Zn), and 50 ppm nickel (Ni). Dots indicate sampled localities. Areas underlain by gabbro are indicated by y. STROMQUIST, WHITE, AND MCHUGH 60 Copper PARTS PER MILLION ‘ “ Nickel I I l I fi 10 20 30 4o 50 NUMBER OF SAMPLES FIGURE 3.—Frequency distribution of copper, lead, zinc, and nickel in 55 samples of stream alluvium, High Rock quadrangle, North Carolina. Values for molybdenum and tungsten, not shown on dia- gram, were <4 and <20 ppm, respectively. REFERENCES Bell, Henry, 3d, and Overstreet, W. C., 1960, Geochemical and heavy-mineral reconnaissance of the Concord quadrangle, Cabarrus County, North Carolina: U.S. Geol. Survey Min- eral Inv. Field Studies Map MF—234. Conley, J. F., 19623, Geology of the Albemarle quadrangle, North Carolina: North Carolina Dept. Conserv. and Devel., Div. Mineral Resources Bull. 75, 26 p., map. 1962b, Geology and mineral resources of Moore County, North Carolina: North Carolina Dept. Conserv. and Devel., Div. Mineral Resources Bull. 76, 40 p., map. Hawkes, H. E., J r., 1957, Principles of geochemical prospecting: U.S. Geol. Survey Bull. 1000—F, p. 225—355. King, P. B., 1955, A geologic section across the southern Appala- chians—an outline of the geology in the segment in Ten- 61‘ 732—760 O—64——-7 C91 nessee, North Carolina, and South Carolina, in Russell, R. J ., ed., Guides to southeastern geology: Geol. Soc. America, p. 332—373, map in pocket. Laney, F. B., 1910, The Gold Hill mining district of North Carolina: North Carolina Geol. and Econ. Survey Bull. 21, 137 p. ' 1917, The geology and ore deposits of the Virgilina dis- trict of Virginia and North Carolina: North Carolina Geol. and Econ. Survey Bull. 26, 175 p. LeGrand, H. E., 1958, Chemical character of water in the igneous and metamorphic rocks of North Carolina: Econ. Geology, v. 53, no. 2, p. 178—189. Overstreet, W. G., and Bell, Henry, 3d, 1960, Geochemical and heavy—mineral reconnaissance of the Concord SE quad- rangle, Cabarrus County, North Carolina: U.S. Geol. Sur- vey Mineral Inv. Field Studies Map MF—235. Pogue, J. E., Jr., 1910, Cid mining district of Davidson County, North Carolina: North Carolina Geol. and Econ. Survey Bull. 22, 144 p. Stromquist, A. A., and Conley, J. F., 1959, Geology of the A1- bemarle and Denton quadrangles, North Carolina: Carolina Geol. Soc. Field Trip Guidebook, 36 p. Stuckey, J. L., 1928, The pyrophyllite deposits of North Caro- lina: North Carolina Dept. Conserv. and Devel., Div. Min- eral Resources, 62 p. ‘ Stuckey, J. L._, and Conrad, S. G., 1958, Explanatory text for the geologic map of North Carolina: North Carolina Dept. Con~ serv. and Devel., Div. Mineral Resources Bull. 71, p. 3—51, map. Ward, F. N., Lakin, H. W., Canney, F, 0., and others, 1963, analytical methods used in geochemical exploration by the U.S. Geological Survey: U.S. Geol. Survey Bull. 1152, 100 p. White, A. M., Stromquist, A. A., Stern, T. W., and Westley, Harold, 1963, Ordovician age for some rocks of the Carolina slate belt in North Carolina: Art. 87 in U.S. Geol. Survey Prof. Paper 475—0, p. 0107—0109. GEOLOGICAL SURVEY RESEARCH 1964 EVALUATION OF WEATHERING IN THE CHATTANOOGA SHALE BY FISCHER ASSAY By ANDREW BROWN and IRVING A. BREGER, Norfhport, Ala., Washington, DC. Abstract—Weathering of the Chattanooga Shale leads to oxi- dation of the organic matter. On Fischer assay this is reflected by increased yields of water and decreased yields of oil. De- crease in oil/water ratios, when plotted against water yields, provides an index for evaluating the degree of weathering to which the shale has been exposed. Low ratios are indicative of a high degree of weathering. The pyrolytic oil yield of the Chattanooga Shale was determined on a large number of samples during studies of the shale as a possible source of uranium (Swanson, 1960). Brown (1956) had earlier reported the yields of oil from various parts of the shale. Analyses indicate a yield of 9 to 10 gallons of oil per ton over much of the area investigated—an oil content too low to be of present economic significance; in addition, the analyses pro— vide information on the loss of oil yield in surface sam- ples as a consequence of weathering processes. Fischer assays (Stanfield and Frost, 1949) of the black parts of the shale (the Gassaway Member and the lower unit of the Dowelltown Member) were made on samples from 13 surface exposures of different types, on samples from 5 drill holes that penetrated the shale at depths of from 136 to 360 feet, and on a sample from the abutment of a dam in southern Kentucky where the shale is far enough below the original land surface to be considered below the zone of surface oxidation and weathering. The area covered by the study, shown in figure 1, is a belt extending about 80 miles northeast from Cannon County, Tenn., into southern Kentucky along the strike of the Chattanooga Shale. Throughout this area the evidence is strong that the black parts of the shale, where unaffected by weathering, will yield 9 to 10 gallons of oil per ton as shown by Fischer assay. About 10 miles south of this area the oil yield of the shale drops rather sharply to 5 to 6 gallons per ton, and 25 or 30 miles to the south- east, in Walden Ridge, Tenn., the yield is only 1 to 3 gallons per ton. North and northwest of the area, data are insufficient to permit tenable conclusions. The lower unit of the lower or Dowelltown Member of the Chattanooga, which contains about 18 percent organic matter, is 5 to 6 feet thick south of the approxi- mate latitude of Cookeville, Tenn. (fig. 1) , but it thins northward and disappears as an identifiable unit about halfway between Cookeville and the Kentucky State line. Above it is the upper or gray unit of the Dowell- town, which contains less than 10 percent organic mat- ter and yields only 2 to 3 gallons of oil per ton; analyses of this unit are not included in the data given. The upper Dowelltown has an average thickness of about 10 feet in the southern part of the mapped area but, like the lower unit, thins and disappears as an identifiable unit in northern Tennessee. The upper or Gassaway Member contains 20 to 25 percent organic matter and is or has been present throughout all the mapped area. It is thickest, about 21 feet, near locality 73 (fig. 1), but thins in all directions, becoming 11 to 13 feet thick at localities 88 and 101 to the south and southwest, and 13 to 17 feet thick near the Kentucky State line. North of that line, however, it thickens again to about 30 feet at locality 12. In the area discussed, the oil yield of the lower unit of the Dowelltown Member is approximately the same as that of the Gassaway Member, and data from both units are given in the accompanying table. The data include assays of shale from the Gassaway Member at 19 locali— ties and of shale from the lower unit of the Dowelltown Member at 13 localities, all in the southern part of the mapped area. The Chattanooga Shale does not contain oil as such, its oil being derived from the carbonaceous constituents known as kerogen (Breger, 1961) on destructive distil- lation. The Fischer assays give not only the oil yield, but the water yield as well. Inasmuch as all samples are dried at 105° C before assay, the water shown is US. GEOL. SURVEY PROF. PAPER 501-0, PAGES C92-C95 092 BROWN AND BREGER C93 Oil and water yields and oil/water ratios of surface and subsurface samples of the Chattanooga Shale in parts of Tennessee and southern Kentucky [Localities are arranged generally from north to south and are shown on figure 1] Yield (gallons per ton) Oil/water ratios Locality No. Unit 1 Thickness (feet) Surface samples Subsurface samples Surface samples Subsurface samples 011 Water Oil Water 12 3 ___________ G __________ 29.10 ________________________ 10. 4 4.0 ____________ 2. 6 16 ____________ G __________ 17. 65 5. 6 6.0 ________________________ 0.9 ____________ 22 ____________ G __________ 13. 23 8.6 6. 1 ________________________ 1. 4 ____________ 27 ____________ G _________ 17. 82 6. 3 8. 0 ........................ . 8 ............ 58 ____________ G _________ 17.93 9. 2 5. 8 ........................ 1. 6 ____________ 60 ____________ G __________ 16.79 7. 9 7. 7 ________________________ 1. 0 ____________ 64 ____________ G _________ 19. 58 9. 5 5. 6 ________________________ 1. 7 ____________ Dl _________ 5. 15 8. 2 4. 8 ________________________ 1. 7 ____________ 66 ____________ G _________ 17. 27 5. 2 6. 8 ________________________ . 7 ____________ D1 _________ 6. 05 3. 2 7. 8 ________________________ . 4 ____________ 73 ____________ G _________ 21. 51 11.1 7.0 ________________________ 1. 6 ____________ D1 _________ 5. 59 10. 6 3. 4 ________________________ 3.0 ____________ C211 _________ G _________ 11.5 ________________________ 8. 2 2. 7 ____________ 3.0 Dl _________ 2. O ________________________ 9. 8 3. 1 ............ 3. 2 037 __________ G _________ 17.43 ________________________ 11. 6 3. 3 ____________ 3. 5 D1 _________ 3. 11 ________________________ 8. 8 3. 6 ____________ 2. 5 C77 __________ G _________ 15. 45 ________________________ 9. 7 3. 6 ............ 2. 7 D1 _________ 5. 74 ________________________ 8. 2 3. 4 ____________ 2. 4 78 ____________ G _________ 18. 45 4. 6 10. 9 ________________________ . 4 ____________ Dl _________ 4. 80 1. 0 10. 8 ________________________ . 1 ____________ 87 ____________ G _________ 16. 50 8. 3 7. 2 ________________________ 1. 2 ____________ D1 _________ 6. 47 10. 0 4. 6 ________________________ 2. 2 ____________ 92 ____________ G __________ 15.09 7.0 6. 4 ________________________ 1.1 ____________ D1 _________ 6. 10 5. 1 7. 7 ________________________ . 7 ____________ 093 __________ G _________ 14. 70 ________________________ 10. 7 2. 6 ____________ 4. 1 D1 _________ 6. 46 ________________________ 9. 0 3. 2 ____________ 2. 7 094 .......... G ......... 14. 00 ________________________ 10. 8 2. 1 ____________ 5. 1 D1 _________ 5. 85 ________________________ 10. 3 2. 8 ____________ 3. 7 88 ___________ G _________ 13.42 9. 6 9.0 ________________________ 1. 1 ............ Dl _________ 10. 38 12. 3 4. 3 ________________________ 3. 0 ____________ 101 ........... G _________ 13.35 8. 7 4. 6 ________________________ 1. 9 ____________ D1 _________ 7. 33 4. 1 7. 4 ________________________ . 6 ____________ I G, Gassaway Member; D1, Lower unit, Dowelltown Member. 1 Southern Kentucky; all other localities in northern Tennessee. derived from the organic matter and, in part, from the clay constituents. Oil and water yields obtained by Fischer assay of 32 samples of Chattanooga Shale are shown in the ac- companying table and are plotted on figure 2. Exami— nation of the points on figure 2 shows that a wide spread exists in values for outcrop samples, and that oil yields are generally higher and water yields lower for deep or core samples than for outcrop samples. These ob- servations suggest that oxidation or weathering of the shale has led to decreased oil yield and increased water yield as shown by Fischer assay. Although the higher water yield might have resulted from oxidation of the organic matter, it could also be explained on the basis of hydration of the clay minerals in the shale. In- asmuch as the mineral content of these shale samples is generally constant, and the clay is primarily hydro- mica (Bates and Strahl, 1957) it seems likely that the water obtained on assay originates in the oxidized or- ganic matter. Oil yield, water yield, and the oil/water ratio shown by Fischer assay of 32 samples are listed in the table, and the relation between the water yield and the oil/ water ratio is shown graphically on figure 3. For the subsurface samples of presumably unweathered shale (the subsurface localities, and locality 12) , the oil yield ranges from 8.2 to 11.6 gallons per ton, the water yield from 2.1 to 4.0 gallons per ton, and the oil/water ratio from 2.5 to 5.1. For surface samples the range in yield is much wider; 1.0 to 12.3 gallons of oil per ton, and 3.4 to 10.9 gallons of water; the oil/water ratio ranges from 0.1 to 3.0. For all subsurface samples the average oil yield is 9.8 gallons per ton, the average water yield, 3.1, and the oil/ water ratio, 3.2. For the surface samples the average values are 8.5 gallons of oil, 6.8 gallons of water, and an oil/ water ratio of 1.3, Unlike the rather consistent oil yield from subsurface samples, the yield from surface exposures differs in outcrops of different types. The highest yields are from the Gassaway Member at locality 73 where the 094 85°00’ GEOCHEMISTRY 3876“ 30' ’l i \ ADAII’. / l \\‘ , RUSSELL , .V . M ETCALFE - WARRI‘N BARREN \ ’ 7 /"' h / r q I S\ M 1 o / x l K \/ \ \ \ , L / ‘ x J CUMBERLAND / . \ }/ \ / Burkesville _ > 1 I ALLEN ” V ’ / CLINTON i 5 ’ T‘““--—————~—~ ——~——— ’ —‘-.—_—_._. , x / PICKETT ’ MACON ' {6% \ / :5, Lafayette WILSON \ ,./ \ \ Smithville 3 7 \c93' V094 ’ 101x RU l‘HERFORD / Woodburyw CANNON / / / \ com a \ \ kw \ BEDFORD 2' b 1 35°30’ DE KALB c77 x92 WARREN \\ , _ l dairiesboro OVERTON i JACKSON ! / / ‘ \ \\ \ / (_’\,.Cookeville c \ N);/ 64 PUTNAM r/ , 6 x , X _ /6\ , 5” \\ N 73 78x 87x 5 . Sparta W H ITE .y P - 8.41- K \ VAN BUREN / /’BLEDs0E / (’ RHEA l/K _/__ 20 30 410 MILES FIGURE 1. —Sketch map showing localities from which samples of the Chattanooga Shale were selected for analysis. the accompanying table rock is exposed in a waterfall, and from the Dowell- town Member at localities 7 3, 87, and 88, all of which are in the beds of perennial streams. The highest oil/water ratio (3.0) of all surface samples is from the lower unit of the Dowelltown at localities 73 and 88; the next highest (2.2) from the lower Dowelltown at locality 87. Dot subsurface locality; X, surface locality. Results of analyses are shown in Samples of both the Gassaway and Dowelltown Mem- bers from locality 64, and of the Gassaway Member at localities 87 and 88, were taken in bluffs protected to some extent by overhanging ledges of Fort Payne Chert. The oil yield at these exposures ranges from 8. 2 to 9. 6 gallons per ton, the water yield from 4. 8 to 9.0 gallons, and oil/water ratio from 1.1 to 1. 7. Compared to sub- BROWN AND BREGER er 11— + + 210— E fl:9_ + I.|.l a.8 Q + + + + 9 7 + + :(J — + o + g 5— + ++ 55. + '2 ++ + ;4_ . + . ', ' + . 3— ° _ . O 2 I I I I I l I I I I .I I I 0 1 2 3 4 5 6 7 8 9 10 ll 12 13 OIL. IN GALLONS PER TON FIGURE 2.—0il and water yields shown by Fischer assay of 32 samples of Chattanooga Shale. Dot, subsurface sample; cross, surface sample. surface samples, the shale has acquired considerable Water, but has lost little if any of its oil yield. Nine of the surface localities (16, 22, 27, 58, 60, 66, 78, 92, and 101) are in old roadcuts where the present shale outcrop is nowhere more than a few tens of feet behind the original outcrop; the roads have been cut into steep hillsides, and the shale has been exposed to weath- ering for decades or centuries. Shale from these road- cuts shows the lowest oil yield, the highest water yield, and the lowest oil/water ratio of all localities studied. The range in oil yield of the nine roadcut samples is from 1.0 to 9.2 gallons per ton, and the water yield ranges from 5.8 to 10.9 gallons per ton; the oil/water ratio is from 0.1 to 1.9. The lowest oil yield is in the surface shale from locality 78, which may be compared with that from drill hole C77, 0.3 mile to the north. The two samples from the outcrop show oil yields of 1.0 to 4.6 gallons per ton and oil/ water ratios of 0.1 and 0.4; the two samples from the drill hole show oil yields of 9.7 and 8.2 gallons per ton and oil/water ratios of 2.7 and 2.4. On the assumption, which seems well founded, that the shale at depth in the area shown in figure 1 yields 9 to 10 gallons of oil per ton and shows an oil/water ratio of about 2.5, certain conclusions as to the efl'ect of weathering on the oil yield of the rock can be drawn. All surface exposures have acquired some additional water, but where the oil/water ratio is between 1.0 and 2.5 the apparent loss of oil yield is small. As weather- ing “continues, however, to the point where the water yield is about the same or more than the oil yield, with ’X C95 5_ O \ _ \ \ 4_ \' \O Q _ \ o E \'\+ 3—— o + -\ _ .\' E - \ 3 \+ 6 2 “ +\ _ +¥\+ \+ + ,_ +¥\+\+ + + ++\*\ _ \ + \\+ o I I I I I I J I I I +I I o 2 4 6 8 10 12 WATER, IN GALLONS PER TON FIGURE 3.—Water yield and oil/water ratio shown by Fischer assay of subsurface (dot) and surface (cross) samples of Chattanooga Shale. oil/ water ratios of 1.0 or less, the continued addition of water is accompanied by loss of some of the kerogen in the rock, possibly through oxidation. It is recognized that only subsurface samples are re— liable indicators of the oil yield of rocks such as the Chattanooga Shale. The oil/water ratios of the rock from surface exposures in limited areas, however, can be used as a qualitative guide to loss through weather- ing. In the area here discussed, and in comparable areas where the yield and the oil/ water ratio at depth are known with reasonable certainty, an oil/ water ratio of 1.0 or less indicates that an appreciable amount of the oil yield has been lost through weathering. REFERENCES Bates, T. F., and Strahl, E. 0., 1957, Mineralogy, petrography and radioactivity of representative samples of Chattanooga shale: Geol. Soc. America Bull., v. 68, p. 1305—1313. Breger, I. A., 1961, Kerogen, in McGraW—Hill Encyclopedia of Science and Technology: New York, McGraw-Hill. Brown, Andrew, 1956, Uranium in the Chattanooga Shale of east- ern Tennessee, in Page, L. R., Stocking, H. E., and Smith, G. B., compilers, Contributions to the geology of uranium and thorium by the United States Geological Survey and Atomic Energy Commission for the United Nations Inter- national Conference on Peaceful Uses of Atomic Energy, Geneva, Switzerland, 1955: US. Geol. Survey Prof. Paper 300, p. 457—462. Stanfield, K. E., and Frost, I. C., 1949, Method of assaying oil shale by a modified Fischer retort: U.S. Bur. Mines Rept. Inv. 4477, 13 p. Swanson, V. E., 1960, Oil yield and uranium content of black shales: U.S. Geol. Survey Prof. Paper 356—A, 44 p. GEOLOGICAL SURVEY RESEARCH 1964 MEASUREMENT OF RELATIVE CATIONIC DIFFUSION AND EXCHANGE RATES OF MONTMORILLONITE By THOMAS E. BROWN, Denver, Colo. Abstract—To broaden the understanding of the effects of clay minerals on the quality of water, a technique was developed for determining the rate of cation exchange between a clay mineral and a contacting solution, together with the rate of cation difiusion into the clay and the solution. The technique consists of mounting the clay on a glass slide, converting the clay to a mono-ionic form, and then bring it into contact with a solution containing the cation that is to be exchanged. Mount- ing the clay on a glass slide permits instantaneous separation of the clay from the solution and therefore permits rate meas- urements for very brief intervals of time. Clay minerals, with their cation—adsorption and ex- change properties, have the ability to modify the chemi- cal quality of contacting solutions. The change in the chemical quality of a solution resulting from contact with a clay mineral or group of clay minerals is directly related to: (1) the quantity and type of clay minerals in contact with the solution, (2) the quantity and types of cations originally adsorbed on the clay minerals, (3) the composition of the solution before contact with the clay minerals, and (4) the length of time that the solution is in contact with the clay minerals. The first three variables can be evaluated by available techniques, but the fourth variable and its relation to the other three presents more of a problem. Numerous workers have studied the rates of cation ex- change between various clay minerals and neutral salt solutions. Gedroiz (1914), Cernsecu (1931), Borland and Reitemeier (1950), Lacy (1954), Faucher and Thomas (1954), Doehler and Young (1962), and Ha- agsma and Miller (1963) have described various aspects of ion exchange of clay minerals. A common difficulty of most workers who have studied exchange reaction rates is in the establishment of brief times of contact be- tween the clay mineral and a solution. The author has devised a simple technique by which contact between a clay mineral and a solution can be held to a time interval as brief as 1 second. The use of clay mounted on glass slides permits a clean and easy separation of the clay from a contacting solution. The technique involves an initial saturation of the clay with a particular cation and subsequent treatment of the clay with a different cation for a measured interval of time. A montmorillonite (Wyoming bentonite) was selected for this study. A suspension of the <2a-diameter frac- tion of the clay was prepared, and 2.5-millili’oer volumes of the suspension were pipeted onto 26X46 millimeter glass slides and allowed to dry. To convert the mont- morillonite to a calcium form in which calcium occu- pied the interlayer, the slides were soaked in 1.0N calcium chloride solution for 15 minutes. X-ray dif- fraction analyses of random samples of the converted montmorillonite confirmed that calcium occupied the interlayer of the clay mineral. The selection of calcium as the intial interlayer cation was based on the following considerations: (1) Calcium montmorillonites are relatively abun- dant in nature. (2) Calcium montmorillonites are characterized by two water layers in their interlayer position and, consequently, are easily recognized by the 15.4-A (angstrom) spacing of the d(001) planes at 50- percent relative humidity. (3) Montmorillonites have a marked preference for calcium over most monovalent cations. Thus, it was possible to contrast the exchange rates of less preferred cations (for example, potassium, sodium, and rubid- ium) with a more preferred cation (for example, cesium) when displacing calcium from a montmoril- lonite. (4) Calcium can be determined quite easily and ac— curately in small quantities (<1.0 parts per million). Alkali metals were selected to displace calcium on the montmorillonites for two reasons: (1) Only calcium and magnesium are more com- monly adsorbed than the alkali metals on montmoril- lonites in nature. U.S. GEOL. SURVEY PROF. PAPER 501-0. PAGES C96—099 C96 BROWN (2) At. 50-percent relative humidity, the single hy- dration level of alkali metals in the interlayer position of a montmorillonite results in a characteristic 12.4 A spacing of the d(001) planes, as contrasted with the 15.4 A spacing for calcium montmorillonite. After the samples of clay (on slides) had soaked for 15 minutes in 1.0N calcium chloride solution, they were removed from the solution, rinsed throughly in dis- tilled water, and then placed individually into separate 50-ml beakers filled with distilled water. Ten minutes of soaking effectively removed extraneous calcium chloride from the samples. Next, the samples of clay were transferred from the distilled water to 50-m1 beakers filled with a solution of the desired cation. After remaining submerged in the continuously agitated cation solution for a pre- determined time, the samples were removed and then rinsed in distilled water. Calcium exchange was deter- mined by measuring the calcium content of the cation solution, using the method given in Rainwater and Thatcher (1960, p. 127). The question arises as to the ability of montmoril- lonite to remain on a glass slide during immersion in various salt solutions, especially when such solutions are being vigorously agitated. Usually, there was no apparent loss of clay from the slide during the entire treatment procedure. Occasional groups of slides had to be discarded when the clay would not adhere during immersion in the different salt solutions. This lack of adherence of the clay resulted from too large a quantity of the clay being present on the slide. Measurements were not made to determine the op- timum thickness of the mounted clay. Slide—mounted kaolinite, illite, vermiculite, and nonmonominerallic clay-sized stream sediments were also checked as to their stability in agitated salt solutions and were found to be equally as stable as montmorillonite. Total cation exchange for each of a group of three calcium-saturated samples of clay prepared at the same time was determined after the slides had remained sub- merged in a 0.1N cesium chloride solution for relatively long periods of time, usually 1, 2, or 3 hours. When the amount of calcium displaced from each of the three samples was in good agreement, complete exchange was assumed. Invariably, the agreement among the samples was good (:5 percent). These data also sub- stantiated the assumption that weight differences among specimens prepared at the same time from the same suspension of clay were negligible. Knowing the total cation exchange and the quantity of clay on a slide, one can easily calculate the cation-exchange capacity of the clay. C97 100 O o o _ O/A /s/ C)/ )x/ +- _ / A ' m E 80 O /./ 6 A e _ // _ Lu 0 o D. / ‘ g 60 —O A/ m 5 _ /' z / / — < A 5 40—,0 . a 6 ,4 _J _. —‘ E / .9 20 4 —— l l l I l 200 400 600 800 1000 1200 TIME, IN SECONDS FIGURE 1.-—Rate curves for displacement of calcium from slide- mounted montmorillonite by various alkali metals. A, agi- tated 0.025N CsCl solution; B, agitated 0.025N RbCl solution; and 0, agitated 0.025N K01 solution. Exchange reactions between calcium montmorillonite and potassium or cesium cations resulted in the fixation of appreciable quantities (>10.0 percent of total ex- change) of the latter two cations. Cation fixation was the principal reason for not reusing the clay samples mounted on the glass slides. Figure 1 illustrates the rate at which cesium, rubid- ium, and potassium in mechanically agitated solutions displace calcium on a montmorillonite. The curves show the combined effect of exchange reaction rate and gross diffusion of different cations on the clay. “Gross dif- fusion” is used herein to indicate the combined effect of cationic diffusion in solution and counter-diffusion of difi'erent cations on the adsorbent. “Counterdifl'usion” is defined by Husted and Low (1954, p. 344) as the simul- taneous diffusion of two different cations in opposite directions. Diffusion Within the clay is anisotropic, and the two principal paths of diffusion are: (1) parallel to the d (001) planes, and (2) perpendicular to the d(001) planes along crystallite edges. Boyd and others (1947), in their work on “organic zeolites”, determined the exchange-rate controlling mechanism to be either diffusion in or through the adsorbent and (or) diffusional transport across a thin liquid. film enveloping the particle. They discounted the chemical exchange of different cations on the adsorb- ent as a rate-influencing factor. Diffusion in or through the adsorbent, if a major fac- tor, would manifest itself if mounted clays having dif- ferent clay thicknesses were subjected to the same treat- 098 ment for the same time interval. The standard clay suspension (thick) was then diluted 100 percent to form a relatively thin clay suspension (thin) from which slides were made. Combined exchange and difl'usion rates were meas- ured for thick and thin clay samples in both agitated and nonagitated solutions. The efl'ect of solution agita- tion, maintained by a magnetic stirrer, on the rate curves is shown on figure 2. The facts that both thick and thin samples when im- mersed in agitated solution yielded results that fell on the same rate curve (A) , and that this curve is markedly displaced with respect to the separate rate curves for thin (B) and thick (0) samples in unagitated solutions suggest that the measured exchange rates are in part functions of the mobility of ions in solution and (or) the diffusion of cations across the particle—enveloping film. The separation between curves 0 and D is attrib- uted to rapid depletion of exchanging cations in the unstirred solution next to the clay, with the result that a small amount of clay undergoes total exchange more rapidly than a large amount of clay. One of the principal benefits derived in using sam— ples of clay mounted on slides is the ease with which X—ray diffraction studies can be coordinated with rate studies. Figure 3 illustrates the diffraction results ob- tained in the calcium montmorillonite to cesium mont- morillonite transition. The X-ray‘ diffraction tracings illustrated on figure 3 were obtained at an approximate 20-percent relative humidity, with the exception of tracing A, which was obtained at 50-percent relative 100 FTC o 0 80 v é/ o ‘f/ " 60 ~ / // n o ‘ o 7/. x 40 -° / A 20 s— — TOTAL EXCHANGE,|N PERCENT 0 I l l 1 l 200 400 600 800 1 000 TIME, IN SECONDS 1200 FIGURE 2.—E£fect of solution agitation on rate curves for cal- cium clay-cesium solution exchange. A, agitated solution for both thick (open triangles) and thin (open circles) clay slides; B, nonagitated solution for thin clay; and 0 non- agitated solution for thick clay. GEOCHEMISTRY INTENSITY MOBIL l l I I 1 l l 10 8 6 4 2 DEGREES, 20 FIGUBE 3.—Smoothed X-ray diffraction tracings of the calcium montmorillonite to cesium montmorillonite transition, showing region of the d(001) peak. A, 100- percent calcium montmorillonite; B, 71.5—percent calcium montmorillonite; 0, 40.9-percent calcium montmorillonite; D, 9-percent calcium montmorillonite; and E, 100-percent cesium montmorillonite. (N i-filtered CuKa radiation). humidity. This would account for the similarity of the d(001) peaks for tracing 0, D, and E. Figure 3 is also noteworthy in that it emphasizes two .facts previously reported by many workers in the field of clay mineralogy, namely: (1) qualitative analysis of the interlayer cation of montmorillonite should not be based solely on the position of the d (001), and (2) a controlled humidity is essential when studying mont- morillonites with X-ray diffraction. In this work, a humidity control was not available and, consequently, ambient values were recorded. Temperature effects on cation exchange can be meas— ured with the aid of a constant-temperature bath. Studies on ‘montmorillonite in the temperature range from 24° to 48°C. showed that the rate of exchange increased significantly as the temperature of the solu- tion increased. All experimental work reported in this article was done at room temperature (about 26°C). The technique described inthis article applies not only to montmorillonite but also to other clay minerals. The rate of cation exchange between clay minerals and solutions and the diffusion of cations in the clay min- BROWN erals and solutions indicate the effect that these earth materials have on quality of water. In addition, rate studies may provide a means of differentiating various clay minerals in stream sediments. REFERENCES Borland, J. W., and Reitemeier, R. F., 1950, Kinetic exchange studies on clays with radioactive calcium: Soil Sci., v. 69, p. 251—260. Boyd, G. E., Schubert, J., and Adamson, A. W., 1947, The ex- change adsorption of ions from aqueous solutions by organic zeolites; pt. 2. Kinetics: Am. Chem. Soc. J our., v. 69, p. 2836—2848. Cernescu, N. 0., 1931, Kationenumtausch und Strucktur: Inst. Geol. Romaniei Anuar., v. 16 p. 777—859. (Chem. Abs., v. 29, 3897, 1935.) Doehler, R. W., and Young, W. A., 1962, Some conditions affect- ing the adsorption of quinoline by clay, in Swineford, Ada, ed., National Conference on Clays and Clay Minerals, 9th, Lafayette, Indiana, 1960, Proc. : New York, Pergamon Press, p. 468—483. ’X‘ 099 Faucher, J. A., and Thomas, H. C., 1954, Adsorption studies on clay minerals; pt. 4. The system montmorillonite-cesium- potassium: Jour. Chem. Physics, v. 22, ’p. 258—261. Gedroiz, K. K., 1914, Colloidal chemistry as related to soil science; pt. 2. Rapidity of reaction exchange in soil; the colloidal condition of the soil saturated with various bases; and the indicator method of determining the colloidal con- tent of the soil: Zhur. opyt. agron. [USSR], v. 15, p. 181— 205. (Translated by S. A. Waksman and distributed by U.S. Dept. Agriculture.) Haagsma, T., and Miller, M. H., 1963, The release of non- exchangeable soil potassium to cation—exchange resins as influenced by temperature and exchangeable ion: Soil Sci. Soc. America Proc., V. 27, p. 153—156. Husted, R. F., and Low, P. F., 1954, Ion diffusion in bentonite, Soil Sci, v. 77, p. 343—353. Lacy, W. J., 1954, Decontamination of radioactively contami- nated water by slurrying with clay: Indus. Eng. Chemistry, v. 46, p. 1061—1065. ' Rainwater, F. H., and Thatcher, L. L., 1960, Methods for collec- tion and analysis of water samples: U.S. Geol. Survey Water-Supply Paper 1454, 301 p. GEOLOGICAL SURVEY RESEARCH 1964 PRELIMINARY STRUCTURAL ANALYSIS OF EXPLOSION-PRODUCED FRACTURES, HARDHAT EVENT, AREA 15, NEVADA TEST SITE By F. N. HOUSER and W. L. EMERICK, Denver, Colo. Work done in cooperation with the U.S. Atomic Energy Commission Abstract—The HARDHAT nuclear explosion was detonated at a depth of 950 feet in a granodiorite and quartz monzonite stock. Postshot studies, conducted in the station-1500 tunnel at radial distances of from 430 to 520 feet from the center of the detonation, showed that many explosion-produced fractures (1) difier in orientation from pre-explosion fractures, (2) are re- lated to directions of shear and tension resulting from stress originating at the detonation point, and (3) indicate by their orientation that the direction of propagation of the stress wave was deflected to the southeast from the normal as a result of a predominant set of preexplosion joints. The HARDHAT nuclear explosion, with an approximate yield of 5 kilotons, was detonated on February 15, 1962, at a depth of 950 feet in granitic rock of the Climax stock (Houser and Poole, 1960). The Climax Stock consists predominantly of an older granodiorite and a younger porphyritic quartz monzonite in which aplite dikes are locally common. Although the proportions of essential minerals vary appreciably in the two gra- nitic rocks, the diiferences are not enough to greatly af- fect the bulk chemistry. Hydrothermal alteration in the granodiorite and quartz monzonite has formed small amounts of clay, sericite, albite, orthoclase, pyrite, and quartz. The stock is exposed over an area of about 11/2 square miles and probably has a minimum thickness of at least 15,000 feet. Prior to the event, the station-1500 tunnel, herein called the 1500 tunnel for convenience, extended directly toward the U15a drill hole at a depth of 783 feet (eleva- tion 4,253 feet) for a distance of 616 feet from the bot- tom of the station-1500 shaft (fig. 1). The end of the tunnel was 181 feet horizontally and 89 feet vertically from the shot point, which was at an elevation of 4,164 feet. The postshot structural features exposed in the :2. 2 7* Area of tunnel sampled Crushed rock zone’ for fractures or collapse zone — -Area examined, but no explosiomproduced fractures found 1500 Tunnel X 1500 Shaft Q 400 FEET L_I_J__._;i FIGURE 1.—Genera1ized map of the 1500 tunnel used in the HARDHAT event, showing zones crushed and collapsed by the U15a explosion. 1500 tunnel were mapped in May 1962, by W. L. Emer- ick, J. W. Hasler, R. P. Snyder, and W. H. Laraway. COMPARISON OF EXPLOSION-PRODUCED FRACTURES WITH THE PRE-HARDHAT NATURAL FRACTURES The two most conspicuous sets of explosion-produced fractures have the following average orientations: N. 42° W. (strike), 88° NE. (dip); and N. 65° W., 71° SW. (sets A and B respectively, fig. 2). Three less ob— vious groups of similarly oriented joint sets have the following average attitudes: N. 72° W. (strike), 85° NE. (dip) ; N. 70° E., 88° SE; and N. 65° 13., 50° NW. U.S. GEOL. SURVEY PROF. PAPER 501-C, PAGES C100—C102 C100 HOUSER AND EMERICK Approximate center of natural set: N.55°W., 85°N E. (strong; faults and fracture zones common) SET 0 N N.72°W., Approximate center of 85°NE. natural set: N.40°E., vertical N.60°E.to E.-W., ‘8; ' Approximate center of / natural set: N.36°W., 0 22°NE. N.5°W., vertical ' Trace of _ shear cone." Plot of straight-line direc- tion of wave prop- agation assumed FIGURE 2.—Contour diagram of 51 poles of explosion-produced fractures mapped in the 1500 tunnel. All plots are on the upper hemisphere of an equal-area projection; contour in- tervals are in percent. Preexplosion fractures are referred to as “natural.” Modified by annotation from contour dia- gram by Emerick, Snyder, and Bowers (written communica- tion, 1962). (sets 0, D, and E, respectively, fig. 2). It can be seen that none of the attitudes agrees with the three pre- dominant preexplosion natural fracture sets of N. 55° W. (strike), 85° NE. (dip) ; N. 36° W., 22° NE., and N. 40° E., vertical dip. The explosion-produced set strik- ing N. 42° W., and dipping 88° NE. is the only one that is close (about 13°) to a preexplosion set in attitude. This one set in the explosion—produced group of frac— tures is nearly parallel to a tension direction related to the stress-propagation direction in the vicinity of the tunnel, and its prominence may be attributed to its near relationship to the preexplosion set striking N. 55° W. and dipping 85° NE. The preexplosion set striking N. 36° W., and dipping 22° NE. is not represented in any way in the observed postshot fractures, and only a few individual postexplosion joints are near in attitude to the moderately strong preexplosion set striking N. 40° E. and dipping vertically. EXPLOSION-PRODUCED SHEAR AND TENSION FRACTURES It is to the less pronounced explosion-produced frac— tures that we must turn to define the relation between s 0101 the tension and shear fractures and the direction of propagation of the stress wave (fig. 2) . The fractures parallel to shear directions related to the direction of propagation are defined by 6 partly linear groups that comprise about 115° of the total 360° of the cone of shear. Although these groups are of low fracture density, they are designated “sets” on figure 2 for convenience in annotation only.‘ The moderately pronounced set B, striking N. 65° W. and dipping 71° SW., includes shear fractures, but it defines only part of a cone of shear, the approximate center of which is the stress-wave propagation direction. Explosion- produced fractures of five other general orientations further define the cone of shear. The attitudes of these are in the vicinity of (1) N. 75° E. (strike), 32° SE. (dip); (2) N. 33° E., 50°—70° SE.; (3) N. 50° E., 65° NW., (4) N. 60° E. to E—W., 50° NW.; and (5) N. 72° W., 85° NE. (fig. 2). Most of these fractures are joints, but explosion—produced faults are also common in the N. 65° W. (strike), 71° SW. (dip) (set B) and N. 70° E., 88° SE. (set D) groups. It is believed that the pronounced concentration of shear fractures with the general attitude of N. 65° W. (strike) and 71° SW. (dip) (Set B) were formed where a shear direction could avail itself of preexplosion natural fractures, probably belonging to the set striking N. 55° W. and dipping 85° NE. The trace of the cone of shear defined by these six groups is shown by lines of dots in figure 2. Points on this trace are at generally approximately equal angular distances from the polar plot of the direction of the streSS wave. The trace is asymmetric with respect to the center of the plot because the explosion occurred in a direction at about negative 12° below the interval of tunnel surveyed and represented on figure 2. The explosion—produced tension fractures approxi- mately perpendicular to the direction of propagation of the stress wave are indicated as striking about N. 70° E. and dipping 88° SE. (set D). Tension fractures ap- proximately parallel to the direction have two main attitudes: N. 42° W. (strike), 88° NE. (dip) (set A) and N. 5° W., vertical dip. Most of these tension frac- tures have orientations of the first of the above types and were influenced probably by the pronounced natural fracture set striking N. 55° W. and dipping 85° NE. DIRECTION OF PROPAGATION OF STRESS WAVE The 1500 tunnel is oriented parallel to, and 89 feet above, a horizontal radial line projected from the HARD- HAT shot point, as shown in figures 1 and 3. The in- terval of tunnel in which fractures were measured is be- tween 430 and 520 feet from the point of detonation. C102 SSE Drill hole NNW 5200's U15a ~ 1500 5115ft Shaft ’- 7~—_ soseft // i / 5000L » 800 ft " z: to no I\ 7 Area of tunnel sampled for 4400; fractures\ — 4253 ft F 'Ach 1500 Tunnel 0 300 600 FEET FIGURE 3.—Generali_zed section of the 1500 tunnel, showing relation of the tunnel to shot point. The average angle between the tunnel interval ex- amined and the shot point is 12° from the horizontal, but ranges from 13° at the end near the shot (430 feet) to 11° at the limit of fracturing (520 feet). Features of the explosion-produced fractures suggest that the stress wave did not pass parallel to the straight- line direction from the shot point to the tunnel, at the midpoint in the radial-distance interval of 430 to 520 feet. Rather, the stress wave was deflected slightly to the southeast. Four features which indicate this hori- zontal change in direction are: ( 1) The average counterclockwise deflection of about 6° of the shear fractures that strike approxi- mately perpendicular to the line of the tunnel. (2) The average counterclockwise deflection of about 7° of the tension fractures that strike approxi- mately perpendicular to the line of the tunnel. (3) The approximately 3° clockwise deflection of the center of the trace of the cone of shear as defined by the interpreted shear fractures. (4) The approximately 9° clockwise deflection of the bisectrix of the tensional fractures approxi- mately parallel to the theoretical direction of propagation. The bisectrix is used here rather than the average because it is thought that the ' GEOPHYSICS high frequency of the set striking N. 42° W. and dipping 88° NE. (set A, fig. 2) is due to the strong preexplosion set striking N. 55° W. and would unduly influence such an average. The reason for the horizontal deflection of 3° to 9° is thought to lie in the implied tendency of the stress waves to parallel the very strong preexplosion set strik- ing N. 55° W. and dipping 85° NE. The average angles of incidence of an assumed straight-line stress-wave propagation to the fractures striking N. 55° W. and dip- ping 85° NE. would be 42° horizontally and 70° verti- cally. The only other preexplosion set worthy of con- sideration is that striking N. 40° E. and dipping verti- cally. This set was found by pretest surface and sub- surface mapping to be somewhat less open than the set striking N. 55° W. and only about a third as frequent in occurrence. SUMMARY It is concluded that new, postshot fractures ( 1) differ in attitude from the preexplosion natural fractures, (2) are related to directions of shear and tension resulting from stress originating at the detonation point, and (3) indicate by their orientation that the direction of prop- agation of the stress wave was deflected 3° to 9° to the southeast from the normal as a result of a predominant set of preexplosion joints. This may be the first well—illustrated example for esti- mating the influence of preexisting fractures on the dis- tortion of a shock wave in a rock medium. Examples of deflection in strain are often observed in nature, but fre— quently the direction of stress is unknown or surmised. Here at the site of the HARDHAT event the source is known. . For any future experiments in the Climax stock, in which the direction of stress-wave propagation would be critical in interpreting effects, consideration should be given to the orientation and frequency of existing natural fracture systems so as to minimize their influ- ence. Those parts of stress waves moving in horizontal or nearly horizontal directions approximately parallel to the average strikes of the N. 55° W. and N. 40° E. natural sets should be influenced the least in the manner described in this report. REFERENCE Houser, F. N. and Poole, F. G., 1960, Preliminary geologic map of the Climax stock and vicinity, Nye County, Nevada: U.S. Geol. Survey Misc. Geol. Inv. Map 1-328, 2 sheets. GEOLOGICAL SURVEY RESEARCH 1964 SEISMICITY OF THE LOWER EAST RIFT ZONE OF KILAUEA VOLCANO, HAWAII, JANUARY 1962—MARCH 1963 By ROBERT Y. KOYANAGI, Hawaiian Volcano Observatory Abstract.~—Eight—hundred and forty small, shallow earth- quakes from the lower eastern part of the Kilauea east rift zone were recorded at Pahoa between January 1962 and March 1963. N inety-four percent of these earthquakes, including some that were felt, were smaller than magnitude 2. The largest was of magnitude 4.0. Instability of the flank of Kilauea south of the east rift zone is indicated by the concentration of foci south of the surface trace of the rift zone. Following the brief eruption of Kilauea along the central part of its east rift zone in September 1961 (Moore and Richter, 1962), frequent eathquakes ema- nated from the lower part of the rift zone and adjacent southeast flank of the volcano for many months. Earth- quakes from this region, lat 19°21’ N. to 19°33’ N. and long 154°46’ W. to 155°06’ W. (fig. 1), that occurred from January 1962 through March 1963 were studied to determine what light they might shed on the struc— ture of this portion of the volcano. The seismograph at Pahoa recorded 840 earthquakes ranging in magnitude from 0.5 to 4.0 on the Richter scale during this period. At Pahoa these earthquakes Were characterized by strong, sharp first motion, high frequency (5 to 10 cycles per second), and short total duration (1/2 to 2 minutes). Almost all the quakes pro— duced compressional first motion at Pahoa. Earthquakes of magnitude 2 or greater were gen- erally well recorded on the Kilauea seismic network and at Hilo, as well as at Pahoa (fig. 1) (see also Kri- voy and others, 1963; Koyanagi and others, 1963; Oka— mura and others, 1963; Okamura and others, 1964; and Krivoy and others, 1964, for a description of stations and instruments of the seismic network). Foci were determined from P arrival times interpreted on the basis of traveltime curves obtained from the March 7, 1955, earthquake in southeast Hawaii (Eaton, 1962, fig. 2, model B). The very large number of smaller quakes that originated within 15 to 20 kilometers of Pahoa EXPLANATION f? A Volcanic cones Hawaii Volcano Obser— and craters vatory seismograph stations 155° A ’4 Kilauea A ’ networkA A ' Cracks . . A 1 h 9:505: ,/ 2.0—3.0 3.0-4.0 19"— “ e u Fault traces Magnitude, Richter scale 0 50 K M O 5 10 KILOMETERS CONTOUR INTERVAL 250 FEET FIGURE 1.—Plot of earthquake epicenters (elongated dots) along the lower east rift zone of Kilauea, during January 1962— March 1963. Cones, craters, cracks, and fault traces after Stearns and Macdonald (1946). were poorly recorded at other stations, where their first arrivals were often indistinct. Epicenters of quakes of magnitude 2.0 and greater are plotted on figure 1. Most of these quakes came from depths of 3 to 8 km. The two deepest quakes of the group had magnitudes of 2.5 and 2.8 and originated at a depth of about 12.5 km at lat 19°22’ N., long 155°03’ W. Several deeper earthquakes (about 45 km) oc— curred a few kilometers southwest of the region con- sidered here (Koyanagi, 1964). US. GEOL. SURVEY PROF. PAPER 501-0, PAGES 01103-0105 0103 0104 MAGNITUDE N I 0: <2 I v 1 l I 1 1 0 100 200 300 400 500 600 700 800 NUMBER OF QUAKES FIGURE 2.—Magn1tudes of quakes along the Kilauea lower east rift recorded at Pahoa during January 1962—March 1963. The smallest earthquakes from this region that could be discerned on the Pahoa seismograms had magnitudes of about 0.5. Of the 840 quakes recorded at Pahoa, 790 (94.0 per- cent) were smaller than magnitude 2.0 (fig. 2). Forty- five (5.4 percent) had magnitudes of 2.0 to 3.0; and five (0.6 percent) had magnitudes of 3.0 or greater. The largest earthquake of the group was of magnitude 4.0. It took place 14 km southwest of Pahoa at a depth of about 5 km on January 7, 1962. It was felt through- out the island, but no damage was reported. Several earthquakes smaller than magnitude 2.0, presumably from the immediate vicinity of Pahoa or Kapoho, were felt as sharp vibrations lasting only 1 or 2 seconds by residents of these communities. The number of quakes recorded at Pahoa per week (fig. 3) ranged from O to 58. Periods of increased seis- mic activity alternating with relatively quiet periods occurred at intervals of 3 to 7 weeks. The most striking feature of the curve is the 2 months of very low seismic activity on the lower east rift zone after the brief erup- tion of Kilauea in and near Aloi Crater on the upper 60 50 9 :7 , 8 3 NUMBER OF QUAKES N O 10 01 15212 26 1226 9 23 7 21 JAN. FEB. MAR. APR. MAY JUNE JULY AUG. GEOPHYSICS east rift zone during December 7—10, 1962. This period of inactivity was terminated at the end of February 1963 by 2 weeks of frequent earthquakes; 48 quakes were recorded during the week that ended on March 11. When considered in the context of events at Kilauea following the 1960 flank eruption near Kapoho (Richter and Eaton, 1960) , the high level of seismic activity along the lower east rift zone from January 1962 through March 1963 appears to be closely related to the rapid refilling of the shallow reservoir beneath the Kilauea summit (Eaton, 1962) that began in the autumn of.1960. Also, the drop in reservoir pressure caused by the small eruption in December 1962 seems temporarily to have relieved stresses usually applied through the fluid core of the rift zone to the lower (eastern) part of the rift zone. The preponderance of shallow earthquakes and the absence of foci deeper than about 12 km indicate that the lower part of the rift zone is confined largely to the pile of volcanic rocks on the ocean floor and that it does not penetrate the mantle. Lateral transmission of magma demonstrated in recent flank eruptions (Eaton, 1962) also supports the idea of a shallow rift zone. The asymmetry in the distribution of earthquakes, with the rift zone itself being the northern limit of con- centrated epicenters, shows the instability of Kilauea’s southeast flank, which is broken by numerous normal faults that approximately parallel the rift zone and have downward displacement on the seaward blocks. The author wishes to express sincere appreciation to Jerry P. Eaton, US. Geological Survey, for his sugges- tions and assistance in organizing this article. 418216301327102482251931731142811251125 SEPT. OCT. NOV. DEC. JAN. FEB. MAR. FIGURE 3.—Weekly frequency of earthquakes along the lower east rift zone recorded at Pahoa, January 1962—March 1963. KOYANAGI REFERENCES Eaton, J. P., 1962, Crustal structure and volcanism in Hawaii, in Macdonald, G. A., and Kuno, Hisachi, eds., Crust of the Pacific Basin: Am. Geophys. Union, Geophys. Mon. 6, p. 13—29. Koyanagi, R. Y., 1964, Hawaiian seismic events during 1962: Art. 144 m U.S. Geol. Survey Prof. Paper 475—D, p. D112—D117. Koyanagi, R. Y., Krivoy, H. L., and Okamura, A. T., 1963, Ha- waiian Volcano Observatory summary: U.S. Geol. Survey Hawaiian Volcano Observatory Summary 25, (Jan, Feb., and March 1962). Krivoy, H. L., Koyanagi, R. Y., and Okamura, A. T., 1963, Ha- waiian Volcano Observatory summary: U.S. Geol. Survey Hawaiian Volcano Observatory Summary 24, (Sept, Get, and Dec. 1961). Krivoy, H. L., Koyanagi, R. Y., Okamura, A. T., and Kojima, George, 1964, Hawaiian Volcano Observatory summary: 6? 0105 U.S. Geol. Survey Hawaiian Volcano Observatory Sum- mary 28, (Oct., Nov., and Dec. 1962). [In press] Moore, J. G., and Richter, D. H., 1962, The 1961 flank eruption of Kilauea Volcano, Hawaii [abs]: Trans. Am. Geophys. Union, 43, p. 446. Okamura. A. T._. Koyanagi, R. Y., and Krivoy, H. L., 1963, Ha- waiian Volcano Observatory summary: U.S. Geol. Survey Hawaiian Volcano Observatory Summary 26, (April, May, and June 1962). Okaniura, A. T., Kojima, George, and Yamamoto, Akira, 1964, Hawaiian Volcano Observatory summary: U.S. Geol. Sur- vey Hawaiian Volcano Observatory Summary 27, (July, Aug., and Sept. 1962). Richter, D. H., and Eaton, J. P., 1960, The 1959—60 eruption of Kilauea Volcano: The New Scientist, v. 7, p. 994—997. Stearns, H. T., and Macdonald, G. A., 1946, Geology and ground- water resources of the Island of Hawaii: Hawaii Div. Hy- drography Bull. 9, 363 p. GEOLOGICAL SURVEY RESEARCH I964 PALEOLATITUDINAL AND PALEOGEOGRAPHIC DISTRIBUTION OF PHOSPHORITE By RICHARD P. SHELDON, Denver, Colo. Abstract—Recent phosphorite has been shown to occur at warm latitudes, between the equator and the 40th parallels. Ancient phosphorite commonly is found at much higher lati- tudes. When occurrences of ancient phosphorite are located according to their virtual geomagnetic poles, their resulting paleolatitudinal distribution closely matches the latitudinal distribution of young phosphorite. Also, the paleogeographic setting of ancient phosphorite matches the geographic setting of young phosphorite. Thus, the combined study of paleomag— netic and paleogeographic data will aid in the search for ancient phosphorite. V. E. McKelvey (1963) has shown that Recent and upper Tertiary phosphorite is a fairly common sedi- ment, but that it occurs only in certain geographic posi- tions. It is deposited in warm climates between the 40th parallels, mainly on the west coasts of continents, but also in small part on the other coasts. Older phosphorite shows no such clear-cut geographic distribution. For an extreme example, Mississippian and Triassic phosphorite occurs on the north slope of the Brooks Range in Alaska, north of the Arctic Circle (Patton and Matzko, 1959) . This difference in distribution between young (late Tertiary to Recent) and old (pre late Tertiary) phos- phorite suggests either that the warm climatic belts at one time extended to higher latitudes than at present, or that the positions of the climatic belts have changed with respect to the continents. In order to test these alternatives, the distribution of ancient phosphorite has been plotted with respect to the virtual geomag— netic poles at the time of its deposition. With this orientation, the difference in latitude at the time of deposition between the young and old phosphorite dis- appears, suggesting that the positions of climatic belts have changed with respect to the continents. Thus, a new approach to the exploration for ancient phosphorite is possible. Study of the paleogeography in the proper paleolatitude of each geologic system of each continent may reveal many areas favorable for the existence of phosphate deposits. This article is an outgrowth of the phosphate research of the U.S. Geological Survey, largely under the direc- tion of V. E. McKelvey. Many people have been help- ful in supplying data and in criticizing the article. In particular I would like to thank V. E. McKelvey, War- ren Hamilton, J. B. Cathcart, F. G. Poole, Cleaves Rogers, and E. R. Cressman of the US. Geological Sur— vey, T. M. Cheney of Nicol Industrial Minerals, and L. T. Grose of Colorado College. LATITUDINAL DISTRIBUTION OF YOUNG PHOSPHORITE McKelvey (1963, fig. 2) showed the distribution of Recent phosphorite in the ocean and pointed out that geologically young phosphorite has a similar distribu- tion. His data are given in table 1, together with those for a few occurrences of upper Tertiary phosphorite, and are plotted in graphical form on figure 1. The LATITUDE, IN DEGREES A. AREAS OF OCEANIC UPWELLING CAUSED BY DIVERGENCE "'I"":':"l ”2.. l- 1 l J 20 3O 40 50 6O 70 LATITUDE , IN DEGREES B. AREAS OF DYNAMICALLY CAUSED UPWELLING O NUMBER OF OCCURRENCES u. 5 o —I—l E u 50 60 70 LATITUDE, IN DEGREES C. TOTAL FIGURE 1.—Distribution of young (Recent and late Tertiary) phosphorite. U.S. GEOL. SURVEY PROF. PAPER 501-C, PAGES 0106-0113 0106 SHELDON TABLE 1.—Distr1.'butian of young phosphorite Area Latitude Source or data RECENT PHOSPHORITE Deposited in areas of oceanic upwelling caused by divergence Southwestern North America _ 25°—42° N- _ _ - McKelvey (1963). Western South America _____ 5°—40° S _ ___ _ - Do. Venezuela _________________ 11 ° N ________ D‘o. Northwest Africa __________ 1 5°—32° N_ - _ _ Do. Southwest Africa __________ 18°—35° S- _ _ _ Do. Ghana, Africa _____________ 5° N _________ Do. Australia _________________ 20°-23° S- _ - _ Do. Deposited in areas of dynamically caused oceanic upwelling Red Sea __________________ 12°—27° N- - - - McKelvey (1963). Southern India ____________ 8° N _________ Do. Brazil ____________________ 36°—38° S and Do. 1 3°—1 5° S Southern Florida ___________ 25° N ________ Do. North Carolina ____________ 34° N -------- Do. UPPER TERTIARY PHOSPHORITE Deposited in areas of oceanic upwelling caused by divergence California (Monterey For- mation, Miocene). Sechura, Peru (Miocene)___- 34°—37° N- _ _ _ 6° S _________ Bramlette (1964). T. M. Cheney (oral commun- ication, 1961). Deposited in areas of dynamically caused oceanic upwelling Florida (Hawthorn Forma- tion, Miocene). North Carolina (Miocene)__ 27°—29° N_ - - _ 35°—36° N- - _ - Cathcart and others (1953). J. B. Cathcart (oral commun- ication, 1962). H N I\) w w 01 O 01 O U! 8 l I I I I I LATITUDE, IN DEGREES ._. O I 0|l|I| 125 ||JlI| | i | 10 20 3040506070 80 90 95 98 99 PROBABILITY, IN PERCENT FIGURE 2.—Probability graph of the distribution of young (late Tertiary and Recent) phosphorite. #324160 0—64—8 0107 graph was constructed by taking the range latitude of each area of phosphorite deposition and plotting one point for each degree. of latitude covered. This is equiv- alent to random sampling on a grid pattern, and the graph is a frequency diagram. The results give an approximately bell—shaped dis— tribution with a mean latitude of about 23° and a range of from 5° to 42°. These data when plotted on a prob- ability graph (fig. 2) approximate a straight line, show- ing that the data approach a normal distribution. PHOSPHORITE DEPOSITION Most Recent phosphorite is deposited in areas of oceanic upwelling caused by divergence (Kazakov, 1937 ; McKelvey and others, 1953)., which generally are found in the trade-Wind belt where surface waters are blown offshore by the trade winds and where the ofl'shore cur- rent is augmented by the Coriolis force. Deeper, cold phosphorus-rich ocean water wells up to take the place of the seaward-moving surface water. In general, this upwelling occurs on the west coasts of continents, on the north coasts of continents in the northern hemisphere, and on the south coasts of continents in the southern hemisphere. The latitudinal distribution of Recent and upper Tertiary phosphorite is shown in figure 10'. The geographic setting of the Recent deposits 011' the coast of California and Baja California is shown in figure 3. Some phosphatic sediment is deposited in areas of dynamic upwelling (McKelvey, 1963). For example, off the south coast of Florida the deep-flowing Florida Current is forced up over the shallow submarine part of the Florida Peninsula (Sverdrup and others, 1946) and probably is the cause of the deposition of minor amounts of phosphorite (fig. 3). The latitudinal distri- bution of this type of phosphorite is shown in figure 13. Geologically young phosphorite commonly is found in rocks exposed adjacent to areas of modern oceanic upwelling (McKelvey, 1963). For example, the phos— phorite in the Monterey Formation of Miocene age in California (Bramlette, 1946) is located next to the mod- ern upwelling associated with the California Current (fig. 3), the Miocene phosphorite in the southeastern United States (J. B. Cathcart, oral communication, 1963) is located next to the areas of dynamically caused upwelling associated with the Florida Current (fig. 3), and the Miocene phosphorite of the Sechura Desert in Peru (T. M. Cheney, oral communication, 1961) is lo— cated next to the modern upwelling associated with the Peru Current (fig. 4). There is little doubt that these geologically young phosphorites were deposited by up— welling currents, just as the Recent phosphatic sediment offshore is being deposited by the modern upwelling currents. O 1500 MILES EXPLANATION Recent phosphatic sediment Miocene phosphorite deposits \ 14" Ocean current Prevailing wind FIGURE 3.—Recent and upper Tertiary phosphorite of North America. After Sverdrup and others (1946), McKelvey (1963), Bramlette (1946), Cathcart and others (1953), and B. F. d’Anglejan (written communication, 1963). In areas of both dynamic oceanic upwelling and up- welling caused by divergence, the basic cause of the deposition of apatite, the mineral forming marine phos- phorite, is the warming and decrease in pressure of cold phosphorus-rich waters. Kazakov (1937) showed that a rise in pH will saturate the water with respect to apatite, and J. R. Kramer (written communication, 1962) has shown that a rise of temperature alone also will saturate the water. These two factors partly are interrelated in that a rise in temperature drives ofl' CO2, resulting in a rise in pH. Thus the distribution of phos- phorite in the warmer latitudes is expectable and ap- pears to be ruled out for colder higher latitudes, much as is the case for autochthonous calcium carbonate sedi- mentation (Rodgers, 1957). In summary, phosphorite is deposited in warm lati- tudes, mostly between the 40th parallels. Most phos- phorite is found in areas of oceanic upwelling caused by divergence, which is found in the trade-wind belt on the west coast of continents, on the north coast of continents in the northern hemisphere, and on the south coast of continents in the southern hemisphere. Some phosphorite is found in areas of dynamically caused up— ECONOMIC GEOLOGY 8|O° 75° \ COLOMBIA 00V \wf\\_ _ L / 3-: I \ =2» ECUADOR I ‘x z /4 \--. V1 / // \- E \ ” / o I ‘ x g \./ K E PERU " L) b\ fi ‘Ii \ ’1 E N LL (\ é \ m \ \ . I \ h‘ 10°— \ _ O 300 MILES EXPLANATION . nag “.on W, 0.0- . a .Oun-‘Lu.; W—"inu .. plum-nu a... , Miocene marine rocks Miocene phosphorite deposits \ é ....... Ocean current Prevailing wind FIGURE 4.—Miocene phosphorite of Sechura, Peru. After ’1‘. M. Cheney (oral communication, 1961), Sverdrup and others (1946), and Harrington (1962). welling which can occur on the east coast of continents and in special geographic settings. DISTRIBUTION OF ANCIENT PHOSPHORITE Ancient phosphorite (table 2) has a much different latitudinal distribution than does young phosphorite. The distribution of ancient phosphorite (fig. 5A) does not appear to be a normal distribution; the range of known latitudes is from 6° to 70°. The processes now operating to form phosphorite could not have operated to form ancient phosphorite in its present positions. Thus, the ancient climatic belts either must have been drastically different than now, or the climatic belts must have moved with respect to the continents, or both. This dilemma has arisen with respect to other climate indicators (see the various articles in N airn, 1961; and Runcorn, 1962). The anomalous paleo- climatic evidence from evaporite, bauxite, bioherm, and glacial deposits largely has been resolved by recent SHELDON TABLE 2.—Present distribution and paleolatitudcs of ancient phosphorite 0109 Present location Locality Age and formation Paleolatitude Source Latitude Longitude Tennessee and Kentucky, Ordovician, Trenton and 34°—37° N---- 86°—87° W--- 12°—13° S---- Smith and Whitlatch U.S.A. Maysville Groups. ‘ (1940). Idaho, U.S.A ____________ Ordovician, Swan Peak 42° N -------- 111° W ------ 9° N --------- Mansfield (1927). Formation. Brooks Range, Alaska, Mississippian, Lisburne 68°—69° N---- 151°-157° W_- 30°-31° N---- Patton and Matzko U.S.A. Group. (1959). Utah, U.S.A ------------ Mississippian, Brazer 41°~43° N---- 111°—112° W-- 3°—5° N ------ Cheney (1957). Formation. Idaho, Wyoming, Mon- Permian, Phosphoria 39°-47° N---- 108°—115° W-_ 3°—9° N ______ McKelvey and others tana, and Utah, U.S.A. Formation. (1959). Alberta, Canada _________ Permian, Rocky Moun- 50°—51° N---- 115° W_. ----- 15° N -------- McGugan and Rapson tain Group. (1961). Brooks Range, Alaska, Triassic, Shublik 69°—70° N---- 144°—146° W-- 42° N -------- Patton and Matzko U.S.A. Formation. (1959). North-central Mexico---- Jurassic, La Caja and La 23°—26° N---_ 102°—104° W-- 15°-18° N_--- Rogers and others (1961). Casita Formations. Huancayo, Peru --------- Jurassic, Sincos Shale---- 11°—12° S---- 75°—76° W--- 4°—6° S ------ T. M. Cheney and L. T. Grose (oral communi- cation, 1963). Brazil ------------------ Cretaceous, Gramame 6°—7° S ------ 35° W ------- 3°-4° S ______ The British Sulphur and Maria Farinha Corp. (1961). Formations. , Turkey and northwest Late Cretaceous, Kara- 36°—37° N-__- 37°—40° E---_ 21°—22° N--__ Sheldon (report in Syria. bogaz Formation. preparation). Syria ------------------- Late Cretaceous --------- 34°-35° N---- 38°—39° E---- 19°—20° N---- Ca eux (1939, p. 283); C. L. Wendel (written communication, 1963). Iraq ------------------------ do ----------------- 34° N -------- 36° E -------- 16° N -------- C. L. Wendel (Written communication, 1963). Israel ----------------------- do ----------------- 30°—32° N---_ 35° E -------- 12°—14° N---_ Bentor (1953). Jordan ----------------- Cretaceous and Eocene--- 31°—32° N---- 36° E-'- ______ 14°—15° N---_ McKelvey (oral com- munication, 1958). Egypt ------------------ Cretaceous -------------- 26°—27° N---- 28°-34° E---- 8°—9° N ------ Cayeux (1941). Algeria and Tunisia ------ Cretaceous and Eocene--- 34°—36° N---- 0°—10° E ----- 18°—20° N_--_ Do. Libya ----------------------- do ----------------- 31° N -------- 15° E -------- 14° N -------- G. H. Goudarzi (written communication, 1963; - Desio, 1943). Morocco --------------------- do ----------------- 32°-—33° N---_ 8°—9° W ----- 15°—16° N---_ Cayeux (1950). studies (Irving, 1956; Blackett, 1961; Opdyke, 1962, p. 41—66) by relocating the localities with reference to their paleolatitudes as determined from magnetic studies. PALEOLATITUDINAL DISTRIBUTION OF ANCIENT PHO‘SPHORITE The paleolatitudes of the early Tertiary and older phosphorite, as determined from selected paleomagnetic results, are shown on figure 58. Its mean paleolati- tude is lower than that of young phosphorite and its distribution does not appear to be normal. However, the range of ancient phosphorite is from 3° to 42° paleolatitude, which closely corresponds to the range of latitude of young phosphorite. The lack of nor— mality may be due to the small sample and the lack of a randomizing element in the selection of the phos- phorite. The correspondence between the latitudes of young phosphorite and the paleolatitudes of ancient phos- phorite is close enough, in View of the inexactness of paleomagnetic data and poor sampling, to explain the anomalous present distribution of phosphorite by the shifting of climatic belts relative to the continents. The virtual geomagnetic poles used in the study are listed in table 3. The virtual geomagnetic pole most closely corresponding to the age of each phosphorite w 5" LIJ :: :::. .1. . o 0 I. L ..... r ........ r ....... ,. I m E 0 10 20 30 4o 50 60 70 g LATITUDE, IN DEGREES D 8 A. PRESENT DISTRIBUTION 0 LI. 0 0: Lu ED 2 5 3 17:3: ........... z o .......| ........ ,.. ,. L. 1 l I o 10 20 30 40 50 6O 70 PALEOLATITUDE, IN DEGREES B. PALEODISTRIBUTION FIGURE 5.—Present distribution and paleodistribution of an- cient (early Tertiary and older) phosphorite. C110 was used, providing that determination of the pole is reasonably reliable. Where several determinations are available an average was taken, and for the Upper Cre- taceous to Eocene pole for Africa, the pole was inter- polated between the Cretaceous and Recent geomagnetic poles. TABLE 3.~Virtual geomagnetic poles Age Latitude Longitude Source North America Early Jurassic _____ 83° N--- 63° E--- Cox and Doell (1960), Jurassic pole 20. Triassic ---------- 56.5° N_ 105° E-- Opdyke in Runcorn (1962, table 2). Permian 41° N_-_ 127° E-_ Cox and Doell (1960), (Leonard). Permian pole 55. Late Mississippian 30° N--_ 133° E-_ Cox and Doell (1960), and Early Penn- Carboniferous sylvanian (used pole 49. for Utah phosphorite). Mississippian 35° N--- 132° E__ Cox and Doell (1960), (used for Alaska average of phosphorite). Mississippian poles 43, 47, 49. Ordovician ------- 20° N--_ 153° E-- Collinson and Runcorn (1960). Africa and Arabia Late Cretaceous 75° N-__ 170° W- Cox and Doell (1960), and Eocene. Cretaceous pole l3. Interpolated be- tween Cretaceous and Recent poles. South America Cretaceous ------- 65.5° N- 118° W- Creer (1962). Jurassic ---------- 78° N_-- 126° W- Creer (1958, 1962), Serra Geral pole. In all examples the present position of the phospho- rite was used in the conversion to paleolatitudes, except for Mississippian and Triassic phosphorite of northern Alaska. In an analysis of the geology around the Arc- tic Ocean, Warren Hamilton (written communication, 1963) has postulated that the northern part of Alaska was detached from the Victoria and Melville Island region in late Mesozoic time and was rotated counter— clockwise to its present position. Hamilton’s evidence for this is based largely on stratigraphy. The Brooks Range miogeosyncline appears to be closely related to the Verkhoyansk miogeosyncline of Siberia, and if the miogeosynclines are restored to continuity, the Triassic and Mississippian phosphorite is moved to a paleolati— tude about 10° lower than that obtained by calculating from its present position relative to interior North America. ECONOMIC GE OLOGY PALEOGEOGRAPHY OF ANCIENT PHOSPHORITE Paleolatitudinal distribution of ancient phosphorite is similar to the latitudinal distribution of young phos— phorite. Geographic settings of ancient and modern phosphorite also appear to correspond. The paleogeo- graphic settings of most occurrences of the ancient phosphorite listed in table 2 are shown in figures 6 through 11, and in each occurrence, the basic paleogeo- graphic elements are the same. These occurrences of phosphorite are located in paleogeographic positions where trade winds and the Coriolis force would oper- ate in concert to produce maximum oceanic upwelling of the divergent type. Independent climatic evidence, where available, is shown on each figure; in general it consists of paleo- wind directions deduced from eolian crossbedding stu- dies, and the occurrence of evaporite deposits. Some of these are less well known than others, so that much work remains to be done to substantiate the paleogeographic details. But the consistency of the results makes it appear that the generalizations concerning the geo- graphy of young phosphorite can also be applied to ancient phosphorite. 1000 MILES EXPLANATION Shallow shelf seas Phosphorite deposits 1:" / Inferred wind Inferred ocean direction current FIGURE 6,—0rdovician phosphorite in the United States. After Mansfield (1927), Smith and Whitlatch (1940), and Sloss and others (1960). SHELDON 112° 108° 104° 48° — I I ' — Q" V $09.} ‘ : \ v A . M O N T A N A $0 NORTH 46 * x as I DAKOTA J-’\ ' a) ._____ \ l K __ - __ II SOUTH 44° — i DAKOTA # IDAHO . I OPEN ._ v 1 __ _ OCEAN ‘-. WYOMING | 42° - _ v [BASIN I n l I NEBRASKA —_§‘—i-———-——— —_——l a _ t l 5 Nobel l 40 U T A H .3 I V 090 r;— V I ea)“ COLORADO , i I I 1 O l l M O 300 MILES EXPLANATION Phosphorite deposits Evaporite deposits Inferred wind . . Inferred ocean dlrectlon current FIGURE 7.——Upper Mississippian phosphorite, Utah, U.S.A. After Cheney (1957). CONCLUSIONS The distribution of ancient phosphorite can be ex- plained in terms of processes known to form modern phosphorite only if there has been polar wandering or continental drift or both. When plotted against its paleomagnetic latitudes, ancient phosphorite shows a distribution and paleogeography similar to those Of young phosphorite, so that the \“z rmer latitudes and the trade-wind belts of the past may have been through- C111 1 04 ° NORTH J DAKOTA o 300 MILES EXPLANATION 1:1 Gypsum-anhydrite deposits Halite Phosphorite ' dep051ts deposits Wind direction Inferredwind Inferredocean deduced from _ direction current e011 3. n c r o s s - be d de d s a nd- stone FIGURE 8.—Permian phosphorite in the northwestern United States. After McKelvey and others (1959), Sheldon and others (1961), R. F. Wilson and E. K. Maughan (oral com- munications, 1960). out most Of geologic time as narrow as at present, and they probably alvays fell within the 40th parallels. Potential phosphogenic provinces (Sheldon, report in preparation) can perhaps be recognized On the basis of paleogeographic and paleomagnetic studies, and the search for phosphorite can be narrowed accordingly. 80° 70° 60" 50° 40° O 1000 MILES Ihl__l EXPLANATION fi Bioherm Evaporite Marine Jurassic deposits rocks Wdzdlu c115 e (3100!: Inferred wind Inferred ocean Phosphorite deposits ECONOMIC GEOLOGY 116° | 28K 24: 20 °\ 16°— O 500 MILES L.__I_l'__l__J EXPLANATION / w” 44" ' Inferred ocean Inferred Wind Phosphorite depOSitS currents direction FIGURE 10.——Jurassic phosphorite, north-central Mexico. After Rogers and others (1961) and C. L. Rogers (written communication, 1963). FIGURE 9.——Jurassic phosphorite, Huancayo, Peru. H, per- manent barometric high area; L, permanent barometric low area. After '1‘. M. Cheney and L. T. Grose (oral com- munications, 1962), Bigarella and Salamuni (1961), and EXPLANATION . ' ' current e011 an cross- direction Harrington (1962). bedded sand- stone 0° 10° 20° 30° 40" I I I I I E U R O P E 40° 8 o 4 /’ o 30 I {Z’Z/ /1§ g/fl/ AX/R’I O 500 7 \ YS SE?“ :1. ’ /, L I, ’lzg/I/ , Z/Vpaleolgtitud/e ////’" a," I Inferred ocean ASIA Phosphorite deposits 7 Land and shallow shelf seas k"- f Inferred wind // direction / current 1000 MILES FIGURE 11.—Upper Cretaceous and Eocene phosphorite, North Africa and the Middle East. After Cayeux (1939, 1941, 1950), Klemme (1958), Sheldon (report in preparation), 0. L. Wendel (written communication, 1963), and G. H. Goudarzi (written communication, 1963) . SHELDON REFERENCES Bentor, Y. K., 1953, Relations entre la tectonique et les depots de phosphates dan le Neguev Israelian: Internat. Geol. Cong, 19th, Algiers, Comptes rendus, sec. 11, pt. 11, p. 93—101. Bigarella, J. J ., and Salamuni, Riad, 1961, Early Mesozoic wind patterns as suggested by dune bedding in the Botucatu sand- stone of Brazil and Uruguay: Geol. Soc. America Bull., v. 72, p. 1089—1106. Blackett, P. M. S., 1961, Comparison of ancient climates with ancient latitudes determined from rock magnetic measure- ments: Proc. Royal Soc., A, v. 263, p. 1—3. Bramlette, M. N., 1946, The Monterey Formation of California and the origin of its siliceous rocks: U.S. Geol. Survey Prof. Paper 212, 57 p. Cathcart, J. B., Blade, L. V., Davidson, D. F., and Ketner, K. B., 1953, The geology of the Florida land pebble phosphate de- posits: Internat. Geol. Cong, 19th, Comptes rendus, sect 11, pt. 11, p. 77—91. Cayeux, Lucien, 1939, Les phosphates de chaux sedimentaires de France (Fran‘ce metropolitaine et d’outre-mer) : Services de la carte geologique de la France, Etudes des gites mineraux de la France, v. 1, Paris, Imprimerie Nationale, p. 1—349. 1941, Les phosphates de chaux sedimentaires de France (France metropolitaine et d‘outre-mer) : Bureau de docu- mentation miniere, v. II, Paris, Imprimerie Nationale, p. 351—659. 1950, Les phosphates de chaux sedimentaires de France (France metropolitaine et d‘outre-mer) : Services de la carte geologique de la France, Etudes des gitesmineraux de la France, v. III, Paris, Imprimerie Nationale, p. 661—1019. Cheney, T. M., 1957, Phosphate in Utah and an analysis of the stratigraphy of the Park City and Phosphoria Formations, Utah: Utah Geol. and Mineralog Survey Bull. 59, 54 p. Collinson, D. W., and Runcorn, S. K., 1960, Polar wandering and continental drift; evidence from paleomagnetic obser- vations in the United States: Geol. Soc. America Bull., v. 71, p. 915—958. Cox, Allan, and Doell, R. R., 1960, Review of paleomagnetism: Geol. Soc. America Bull., v. 71, p. 645—768. Creer, K. M., 1958, Preliminary paleomagnetic measurements from South America: Annales de Geophysique, v. 14, no. 3, p. 373—390. 1962, Paleomagnetic data from South America: J our. of Geomagnetism and Geoelectricity, v. 13, nos. 3 and 4, 154— 165. Desio, Ardito, 1943, L’esplorazione mineraria della Libia: Col— lezione Scientifica e Documentaria Dell‘Africa Italiana, In- stituto per gli Studi di Politica Internazionale, Milano, 333 p. Harrington, H. J ., 1962, Paleogeographic development of South America: Am. Assoc. Petroleum Geologists Bull., vs. 46, no. 10, p. 1773—1814. Irving, E., 1956, Palaeomagnetic and palaeoclimatological as- pects of polar wandering: Geofisica Pura e Applicata, vs. 33, p. 23—41. Kazakov, A. V., 1937, The phosphorite facies and the genesis of phosphorites, in Geological investigations of agricultural ores USSR: Sci. Inst. Fertilizers and Insectofungicides 6? 0113 Trans. (USSR), no. 142, p. 95—113. [Special issue in Eng- lish published for 17th Internat. Geol. Cong]. Klemme, H. D., 1958, Regional geology of circum-mediterranean region: Am. Assoc. Petroleum Geologists, v. 42, no. 3, pt. I, p. 477—512. Mansfield, G. R., 1927, Geography, geology, and mineral re- sources of part of southeastern Idaho: U.S. Geol. Survey Prof. Paper 152, 453 p. McGugan, Alan, and Rapson, J. E., 1961, Stratigraphy of the Rocky Mountain Group (Permo Carboniferous), Banff Area, Alberta: Jour. Alberta Soc. Petroleum Geologists, v. 9, no. 3, p. 73—106. McKelvey, V. E., 1963, Successful new techniques in prospecting for phosphate deposits: Science, Technology, and Develop- ment, United States papers prepared for the United Nations Conference on the application of science and technology for the benefit of the less developed areas, v. II, p. 163—172. McKelvey, V. E., Swanson, R. W., and Sheldon, R. P., 1953, The Permian phosphate deposits of Western United States: In- ternat. Geol. Cong, 19th Comptes rendus, sec. 11, pt. 11, p. 45—64. McKelvey, V. E., Williams, J. S. Sheldon, R. P., Cressman, E. R., Cheney, T. M., and Swanson, R. W., 1959, The Phosphoria, Park City and Shedhorn Formations in the Western phos- phate field: U.S. Geol. Survey Prof. Paper 313—A, 47 p. Nairn, A. E. M., 1961, Descriptive palaeoclimatology: New York, London, Interscience Publishers, 380 p. Opdyke, N. D., 1962, palaeoclimatology and continental drift, in Runcorn S. D., Continental Drift: New York, London, Aca- demic Press, p. 41—66. Patton, W. W., and Matzko, J. J., 1959 Phosphate deposits in northern Alaska: U.S. Geol. Survey Prof. Paper 302—A, p. 1—17. Rodgers, John, 1957, The distribution of marine carbonate sedi- ments, in Regional aspects of carbonate deposition: Soc. of Econ. Paleontologists and Mineralogists, Spec. Pub. 5, p. 2—13. Rogers, C. L., Cserna, Zoltan de, Tavera, Eugenio Van Vloten, Rogers Ojeda, Jesus, 1961, Reconocimiento geologico y depo- sitos de fosfatos del norte de Zacatecas y areas adyacentes en Coahuila, Nuevo Leon y San Luis Potosi: Consejo de Recursos Naturales No Renovables B01. 56, 322 p. Runcorn, S. K., 1962, Continental Drift: New York, London, Academic Press, 338 p. Sheldon, R. P., Maughan, E. K., and C‘ressman, E. R., 1961, Sedimentation in Wyoming and adjacent areas during :Leonard (Permian) time [abs] Geol. Soc. America Spec. Paper 68, p. 100—101. Sloss, L. L. Dapples, E. 'C., and Krumbein, W. C., 1960, Litho- facies maps: New York, John Wiley and Sons, Inc., 108 p. Smith, R. W., and Whitlatch, G. I., 1940, The phosphate re- sources of Tennessee: Tennessee Div. Geol. Bull. 48, 444 p. Sverdrup, H. U., Johnson, M. W., and Fleming, R. H., 1946, The oceans: New York, Prentice-Hall, Inc., 1087 p. The British Sulphur Corp. Ltd., 1961, World survey of phos- :phate deposits: Lon-don, The British Sulphur Corp. Ltd., v. I—VI. GEOLOGICAL SURVEY RESEARCH I964 RECONNAISSANCE OF ZEOLITE DEPOSITS IN TUFFACEOUS ROCKS OF THE WESTERN MOJAVE DESERT AND VICINITY, CALIFORNIA By RICHARD A. SHEPPARD and ARTHUR J. GUDE 3d, Denver, Colo. Abstract.—Vitric material in tuffaceous rocks of Tertiary age in the Mojave Desert is generally altered party or wholly to zeolites, clay minerals, potash feldspar, and (or) silica min- erals. The most abundant zeolite is clinoptilolite, but beds rich in analcime, erionite, and phillipsite have been found. Mordenite is a minor constituent of some beds. Potentially economic deposits of clinoptilolite, analcime, and erionite are listed. In recent years there has been accelerated interest in natural zeolites for industrial use. This article re- ports the results of a reconnaissance of potentially eco- nomic deposits in the western part of the Mojave Des- ert. Some of the more important products for which zeolites are used are: water softeners, desiccants for various liquids and gases, carriers for certain curing agents and catalysts ( O’Connor and others, 1959), hy- drocarbon separators, and decontaminators of radioac- tive wastes containing cesium137 (Brown, 1962). These uses depend upon the ion exchange and sieve properties of zeolites. Industry now uses synthetic zeolites almost exclusively, but as economic methods are developed to convert natural material into a commercial product, large natural deposits may become important. Since the early'studies of Bradley (1928) and Ross (1928), zeolites have been found to be common diage— netic minerals in tufls and tufl'aceous sediments (Def- feyes, 1959) . Clinoptilolite (commonly reported as heulandite) and analcime are by far the most common zeolites reported, although erionite (recently shown to be identical to ofl'retite (Hey and Fejer, 1962) ), phillip- site, and mordenite are known from several localities. Only rarely is chabazite or natrolite reported. Prior to this reconnaissance, a few scattered zeolite occurrences were reported from tufl'aceous rocks of Ter- tiary age in the Mojave Desert and vicinity. Kerr and Cameron (1936) described clinoptilolite in an altered tuif 5 miles east of Tehachapi Pass, where it comprises 10 percent or less of the rock. In their study of the Hector bentonite deposit, Ames and others (1958) found analcime and clinoptilolite in altered tufl’ beds associ- ated with the bentonite. Benda and others (1960) iden- tified analcime and heulandite (probably clinoptilolite) from several cores drilled near Kramer, Calif., and Smith and others (1958, p. 1070) reported beds of anal- cime-crystal sand from the Kramer borate district. Although zeolitized tufl's generally cannot be posi- tively recognized in the field, the following properties are characteristic of the material: (1) conchoidal to subconchoidal fracture, (2) chalky rather than vitreous appearance, (3) relatively low porosity, and (4) mod- erate hardness. Tuffs which are altered to mainly montmorillonite also have most of these properties but generally lack the conchoidal fracture and have a char- acteristic “pop corn” coating on weathered surfaces. Silicified tufi's commonly show a conchoidal fracture but are much harder than zeolitized ones. Color is not a criterion for identification, for although more than half of the zeolitized tufi's of the Mojave are white to light gray, many are pastel shades of red, green, or yellow. Unaltered tufl's and tufl'aceous rocks of Tertiary age are rare in the Mojave Desert. Some ‘tufl's contain minor remnants of vitric material and a few contain vitric particles that are altered only along their peripheries. Even though a tuff may be completely altered, the pyroclastic texture is generally well pre- served by the diagenetic minerals. A hand lens is ade- quate to confirm the pyroclastic nature of most altered tufl'aceous rocks, but fine—grained tuffs and rocks that contained a small amount of vitric material can be cor- rectly identified only in thin section. The identification of individual zeolite minerals is generally not possible in the field, owing to their very fine crystallinity. Some zeolites in altered tutfs are so U.S. GEOL. SURVEY PROF. PAPER 501—0. PAGES Cll4-C116 Cll4 SHEPPARD AND GUF) 0115 118° 117:: l i | 9 o ‘16 IJ O I 9 :q?‘ i cg, 9 . «0| , « Area of A 0‘“ | Q06 report YS‘ >‘ 0e «\é’ Q- E" -L g e ° E'S . a Cl ° 8 filo ~ A Tehachapi 0 o o E 0 .A olo VY‘ ALVORD MTN g Q o o DMojave é Z . 35°~ .: a: Ox 0 .‘ 49 aDKramer o __ \w“ MOJAVE lz DESERT CALI‘coME Q ‘0 < a» ROSAMOND HILLS [m X D. 0,, GA?" A. i Barstow 0k f_________@21flN_TL_______ . 4% Los ANGELES COUNTY o o 8 D ‘ l ‘ Hector 0 0 QA DLancaster I l 0 10 20 30 4o 50 MILES | l l l l I EXPLANATION, A ‘ A x Analcime Clinoptilolite Erionite Mordenite Phillipsite FIGURE 1.-—-Map of the western Mojave Desert, Calif., showing occurrences of zeolites in tufiaceous rocks found during recon- naissance described in this article. finely crystalline that even the necessary optical param- eters cannot be obtained for positive identification. X-ray powder techniques, however, are well suited for identification because the zeolites need not be separated from the other rock constituents (Defl'eyes, 1959). A concentration as low as 10 percent generally can be detected on dilfractometer traces. The zeolites of altered tuffaceous rocks of the Mojave Desert are commonly associated with other diagenetic minerals, such as clay minerals (mainly montmoril- lonite), potash feldspar, and (or) a silica mineral. In addition, the zeolitized rocks may contain pyrogenic crystals and cognate lithic fragments. Inasmuch as many of the tufl's have been reworked, they may also contain plutonic and metamorphic rock fragments and their constituent minerals that were derived from highlands surrounding the depositional basins. The amount of zeolite in altered tuffaceous rocks is variable and, in part, dependent upon the amount of vitric material originally present. Beds that are nearly monomineralic were deposited as vitric tuffs containing only a negligible percentage of crystal and lithic frag- ments. . Those zeolite occurrences found during this recon- naissance are shown on figure 1. Clinoptilolite, anal— cime, and erionite occur either as nearly monomineralic beds or in association with other zeolites and diagenetic minerals. Mordenite is present in many places, but generally this zeolite comprises less than 25 percent of the rock and is associated with clinoptilolite. Phillip- site so far has been found only in the Rainbow Basin north of Barstow and the southeast flank of the Calico Mountains, where it is associated with clinoptilolite and montmorillonite. Those formations of Tertiary age that contain zeo- lites i potentially minable quantities are listed in the accouipanying table. The altered tufl beds are more than foot thick and contain at least 80 percent zeolite at each of the localities listed. When ways to utilize natural zeolite are discovered through industrial tech- nology, these deposits in the Mojave Desert will provide large supplies. Cll6 ECONOMIC Localities of potentially economic zeolite deposits in the western Mojave Desert and vicinity, California Formation and member Zeolite Locality Ricardo Forma- Clinoptilolite-- El Paso Mountains, Last tion, Member 2 Chance Canyon, sec. (Dibblee, 1952). 17, T. 29 S., R. 38 E. Ricardo Forma- ..... do _______ El Paso Mountains, tion, Member 4 NE}£ sec. 18, T. 29 S., (Dibblee, 1952). R. 38 E. Barstow Formation- Analcime-_ _ _ - Vicinity of Rainbow Basin, sec. 24, T. 11 2 W. Clinoptilolite__ Black Can on, sees. 10 and 11, .32 S., R. 44 E., and vicinity of Rainbow Basin, sec. 24, T. 11 N., R. 2 W. Unnamed forma- _____ do _______ Southern flank of Cady tion. Mountains, SW}£ sec. 31, T. 9 N., R. 5 E. Unnamed forma- Erionite ______ Southern flank of Cady tion. Mountains, SWV4 sec. 6, T. 8 N., R. 5 E. Gem Hill Forma- Clinoptilolite__ Vicinity of Gem Hill, tion. SE corner, T. 10 N., R. 13 W. Pickhandle Forma- _____ do _______ Black Canyon, sec. 1, tion of Bowen T. 32 S., R. 44 E. (1954). Spanish Canyon _____ do _______ Alvord Mountain, head Formation. of Spanish Canyon, sec. 30, T. 12 N., R. 4 E., and southeast flank of Clews Ridge, NW% iEec. 3, T. 11 N., R. 4 GEOLOGY REFERENCES Ames, L. L., Jr., Sand, L. B., and Goldich, S. S. 1958, A contri- bution on the Hector, California, bentonite deposit: Econ. Geology, v. 53, p. 22—37. Benda, W. K., Erd, R. C., and Smith, W. C., 1960, Core logs from five test holes near Kramer, California: US. Geol. Survey Bull. 1045—F, p. 319—393. Bowen, 0. E., 1954, Geology and mineral deposits of Barstow quadrangle, San Bernardino County, California: Califor- nia Div. Mines Bull. 165. Bradley, W. H., 1928, Zeolite beds in the Green River Forma- tion: Science, v. 67, p. 73—74. Brown, R. E., 1962, The use of clinoptilolite: Ore Bin, v. 24, p. 193—197. Deffeyes, K. S., 1959, Zeolites in sedimentary rocks: Jour. Sed. Petrology, v. 29, p. 602—609. Dibblee, T. W., Jr., 1952, Geology of the Saltdale quadrange, California: California Div. Mines Bull. 160, p. 1—43. Hey, M. H., and Fejer, E. E., 1962, The identity of erionite and olfretite: Mineralog. Mag, v. 33, p. 66—67. Kerr, P. F., and Cameron, E. N., 1936, Fuller’s earth of ben- tonitic origin from Tehachapi, California: Am. Mineralo- gist, V. 21, p. 230—237. O’Connor, F. M., Thomas, T. L., and Dunham, M. L., 1959, Chemical-loaded molecular sieves—new approach to faster cures: Indus. and Eng. Chemistry, v. 51, p. 531—534. Ross, C. S., 1928, Sedimentary analcite: Am. Mineralogist, v. 13, p. 195—197. Smith, G. I., Almond, H., and Sawyer, D. L., 1958, Sassolite from the Kramer borate district, California: Am. Miner- alogist, V. 43, p. 1068—107 8. GEOLOGICAL SURVEY RESEARCH 1964 ORE CONTROLS AT THE KATHLEEN-MARGARET (MACLAREN RIVER) COPPER DEPOSIT, ALASKA By E. M. MchEVETT, JR., Menlo Park, Calif. Work done in cooperation with the Defense Minerals Emplomtion Administration Abstract—The Kathleen-Margaret copper prospect, near the terminus of the MacLaren Glacier on the southern flank of the Alaska Range, explores north-striking quartz veins that cut greenstone and contain subordinate bornite and chalcopyrite. The quartz veins are near an eastward-striking fault zone. Copper values in the largest and richest known vein apparently diminish northward away from the fault zonchein intersection. This article supplements and updates a report by Chapman and Saunders (1954), who described the Kathleen-Margaret copper prospect during the early stages of its development, and is largely an outgrowth of investigations made under the auspices of the DMEA (Defense Minerals Exploration Administration). The article is based mainly on geologic mapping of the underground workings at a scale of 1 inch equals 20 feet and on examination of several thin sections and polished sections. The writer participated in three brief exam- inations of the prospect in 1957 and 1958 for the DMEA and made an additional 2-day examination in 1960. Emphasis in this article is placed on the structure and local geologic setting of the ore deposit as determined from exposures in the underground workings. Little new information concerning the areal geology at the prospect has been obtained'since the work of Chapman and Saunders (1954). Information in the DMEA files has been drawn upon freely, and grateful acknowledgment is made to those who participated in the DMEA program at the pros- pect, particularly to R. M. Chapman, Fred Barker, and A. E. Weissenborn of the U.S. Geological Survey, and to E. W. Parsons of the US. Bureau of Mines. The prospect is in the southern part of the central Alaska Range, about 10 miles north of the Denali High- way (fig. 1) . It is in the Mount Hayes B—6 quadrangle (US. Geological Survey 1 : 63,360 topographic series, 147° 146° 148° RANG (\Gzamr Kathleen-Margaret}: 54% Copper pr ' / 63° 200 MILES J FIGURE 1.—Index map showing the location of the Kathleen— Margaret copper prospect. 1951), approximately 1 mile west of the terminus of the MacLaren Glacier, at an altitude of about 4,000 feet. Access is most practical by small aircraft, which can utilize a landing strip on the flats of the MacLaren River about 11/2 miles southeast of the prospect. The prospect is also accessible from the Denali Highway by foot or amphibious vehicle. U.S. GEOL. SURVEY PROF. PAPER 501-0, PAGES Cll7-C120 Cll7 0118 A road, approximately 11/2 miles long and suitable for tractors and four-wheel-drive vehicles, connected the prospect with a base camp on the river flats about half a mile northwest of the airstrip. Both the road and the camp buildings are now in disrepair (R. M. Chapman, written communication, 1963). The MacLaren River copper deposit probably has been known since 1918 (Martin, 1920, p. 20)‘, but its early history is sketchy. F. S. Pettyjohn, J r., relocated the copper-bearing quartz veins in 1952 while associated with E. O. Albertson in a prospecting venture. The prospect was explored, partly under DMEA sponsor— ship, between 1953 and 1959, by an adit and connecting underground workings totaling about 800 feet (fig. 2), by diamond drilling, and by shallow trenching. Most of the trenches sloughed and became partly filled with surficial debris soon after they were excavated. Approximately 2 tons of ore, estimated to contain be- tween 1 and 2 percent copper, was stockpiled at the property in 1960. The Kathleen-Margaret prospect is in the altered volcanic rock (greenstone) that is extensively distrib- uted along the southern flank of the central part of the Alaska Range and throughout nearby terranes (Moffit, 1912, pl. 2). This rock constitutes a thick sequence, mainly of lava flows, and was considered by Moflit (1912, p. 30) to be of late Carboniferous or Early or Middle Triassic age. Little geologic mapping has been done in the region since Moffit’s pioneering reconnais- sance. Undoubtedly, detailed geologic mapping would reveal more complicated geology than has been recog- nized by reconnaissance methods and would disclose diverse lithologies and structures. Most of the ground at the prospect is covered by low vegetation and by un- consolidated surficial debris. The dominant rock at the prospect is greenstone that forms a flow sequence dipping southward gently. The greenstone is greenish gray, very fine grained, and is composed largely of secondary minerals. Most of it is cut by numerous veinlets and some is porphyritic and (or) amygdaloidal. Thin sections of the greenstone consist largely of altered plagioclase, epidote, and chlo- rite. Quartz, calcite, and actinolite are less abundant, and sphene, opaque minerals and their alteration prod- ucts, and prehnite( ?) are uncommon. Scattered specks of chalcopyrite are rare constituents of some of the greenstone. The amygdules and veinlets contain epi— dote, chlorite, calcite, and quartz. The porphyritic greenstone consists of phenocrysts of altered plagioclase, as much as 2 mm long, in a felty groundmass that is rich in altered plagioclase less than 0.1 mm long. The primary texture in much of the greenstone has been obliterated during alteration. ECONOMIC GEOLOGY The greenstone is cut locally by hypabyssal rocks, by several discontinuous quartz veins (some containing copper minerals), and by numerous faults. The hypabyssal rocks consist of diabase and a highly altered porphyritic rock. The diabase is known only from a few outcrops where it commonly forms sills as much as 20 feet thick and is slightly altered. It is fine grained, has a diabasic texture, and consists chiefly of pyroxene (augite ? ) , plagioclase, and uralitic hornblende in nearly equal amounts. Its lesser constituents are secondary iron oxides that are mainly alteration prod-. ucts of opaque minerals, and clay minerals. Quartz- chlorite—epidote veinlets cut some of the diabase. A narrow altered porphyritic dike is exposed in the underground workings along a fault a few feet from a mineralized quartz vein, the “main” vein (fig. 2). Rock making up the dike is light gray and contains medium- grained phenocrysts of altered feldspar in a fine—grained groundmass that is ' rich in plagioclase and calcite. Phenocrysts constitute about 25 percent of the rock’s volume. They are largely altered to calcite, chalcedony, epidote, and clay minerals. Subordinate constituents in the groundmass are apatite, altered opaque minerals, and chlorite. The rock is cut by numerous veinlets con- taining epidote, calcite, iron oxides, and quartz. Both the diabase and the porphyritic dike are probably Tertiary in age, although field evidence for their age assignment is meager. Faults are numerous and well exposed in the under- ground workings, but little is known of their areal dis- tribution. A steep fault zone, which strikes eastward and whose component fractures dip between 65° S. and vertical, and several steep subsidiary faults that strike north- eastward are exposed in the underground workings (fig. 2). The fault zone is about 35 feet thick and is characterized by abundant gouge and breccia. The subsidiary faults commonly contain minor gouge and, uncommonly, breccia. The “main” quartz vein is cut by the fault zone and is partly bounded by north— striking faults that dip nearly vertically. Several copper-bearing quartz veins crop out at the prospect (fig. 3), but they commonly are not trace— able along strike for more than 100 feet because of inherent discontinuities or poor exposures. Most of the veins strike nearly north, dip vertically or steeply east or west, and range from a few inches to about 20 feet in thickness. Only one of the veins, the “main” vein, is large enough and rich enough to have en— couraged exploration. It has been explored by both the underground workings and by some of the surface cuts. The copper content of the “main” vein dimin- ishes northward from the intersection between the vein MACKEVET’I‘ 0 10 20 3O 40 L_L_.L__l___l FEET 0 10 20 30 40 50 FEET l_.;|_l_l__l Base map from MacLaren River Copper Corporation, 1957 C119 EX F’ LA N ATI O N :2 ; v V :1: .: Altered porphyritic rock E U 2 m «2 'ECg g 8 2 m _ n: u a: Greensbone 5 E; 0 V L Quartz vein 0 o o 4» .9 , o q. , Copper minerals Chiefly borm'te and chalcopyrite Contact Dashed where approximately located 60 Fault, showing dip Dashed where approximately located _.9L___ Vertical fault Dashed where approximately located \A-v ..~.. Shear zone A A A A A A A Fault breccia XI Foot of raise Geology mapped by A. E. Weissenborn, E. M. MacKevett,Jr., G. 0. Gates, and E. W. Parsons, 1957,1958 FIGURE 2.-—Geologic map of the level workings, Kathleen-Margaret prospect. 0120 unces Trace 0.40 .7 .75 2. 1.7 7 “MAIN"VEIN PORTAL 314,15, 16 Discover“! OF ADIT {so . $0 . . Copper-bearlng quartz vem showmg dip 16 Sample number and approximate location O 200 400 1000 FEET Modlfied from Chapman and Saunders, 1954 EXPLANATION FIGURE 3.—Location and sampling data of outcrop samples, Kathleen-Margaret prospect. and the fault zone (fig. 2). The small quartz bodies that are exposed in the northern part of the adit may be parts of the “main” vein, in which case a size diminution of the vein to the north is also indicated. The “main” vein is not known with certainty south of the fault zone, although the two small quartz veins south of Discovery Creek that were sampled by Chap- man and Saunders (fig. 3, Nos. 12 and 13) may be branches of an offset segment of the “main” vein. The veins consist largely of quartz in the form of strained anhedral crystals between 1 and 2 mm in diam- eter. Much of the quartz is fractured and cut by a system of calcite veinlets that intersect approximately at right angles. The veinlets contain minor quanti— ties of quartz along with the calcite. Most of them are less than 0.1 mm thick. Irregular masses of chal- copyrite and bornite, mostly a few millimeters but as much as several centimeters across, cut and replace the early quartz, and are also cut by the calcite veinlets. Bornite and chalcopyrite are intimately associated throughout most of the ore, with chalcopyrite forming irregular blebs in bornite—rich samples and the con- verse prevailing in the chalCopyrite-rich samples. Bornite is the most abundant sulfide mineral in most of the ore. Surface coatings of malachite are con- spicuous in some of the vein outcrops and also on breccia fragments within the pervious fault zone. 5% ECONOMIC GEOLOGY The grade of ore ranges from a few tenths of a per- cent to about 30 percent copper, but commonly it is between 1 and 5 percent. The ore also contains minor values in silver and traces of gold. The zone of richest ore, about 60 feet long, 5 feet wide, and 100 feet high, extends northward from the fault zone and is adjacent to the west wall of the “main” vein. The diminution in copper values in the “main” quartz vein northward from the fault zone suggests that the fault zone may have been significant in the ore genesis. Possibly the copper-bearing solutions ascended a conduit formed at the intersection between the fault-controlled “main” vein and the incipient fault zone and found receptive hosts in the adjacent frac— tured vein quartz. The copper minerals may have been derived from late-stage fluids associated with the por- phyry dike. The process of ore formation probably was part of a sequence involving (1) the formation of the “main” vein and similiar veins by quartz deposi- tion in open spaces formed by previous fracturing; (2) fracturing of the vein quartz; (3) intrusion of the por— phyry dike; ({1) deposition of chalcopyrite and bornite in the quartz vein near the fault zone during the initial stage of development of the fault zone; (5) addi- tional faulting, particularly along the fault zone; (6) deposition of calcite-rich veinlets in the quartz vein; and (7) mobilization and deposition of the secondary copper minerals in the fault zone and outcrops of the veins contemporaneous with recurrent movements along the fault zone. All the known copper-bearing veins at the prospect are near the projection of the east-striking fault zone, which tends to strengthen the belief that the fault zone had a role in the ore formation. However, additional field and laboratory work should be done before a theory on the genesis of the MacLaren River deposits can be advanced with reasonable assurance. REFERENCES Chapman, R. M., and Saunders, R. H., 1954, The Kathleen- Margaret (K-M) copper prospect of the upper MacLaren River, Alaska: US Geol. Survey Circ. 332, 5 p. Martin, G. 0., 1920, The Alaskan mining industry in 1918: US. Geol. Survey Bull. 712—A, p. 1—52. Moflitt, F. H., 1912, Headwater regions of the Gulkana and Susitna Rivers, Alaska, with accounts of the Valdez Creek and Chistochina placer districts: U.S. Geol. Survey Bull. 498, 82 p. GEOLOGICAL SURVEY RESEARCH 1964 CAVITIES, OR “TAFONI," IN ROCK FACES OF THE ATACAMA DESERT, CHILE By KENNETH SEGERSTROM and HUGO HENRiQUEZ 1 Denver, Colo., Santiago, Chile Work done in cooperation with the Instituto de Investigaciones Geolégtcas de Chile under the auspices of the Agency for International Development, 0.8. Department of State Abstract—Cavities that resemble certain “niches” in rocks of the southwestern United States and “tafoni” of the Medi- terranean area are well developed in granitoid rocks and argil- lite bordering the Atacama Desert along the coast of northern Chile. Similar cavities are developed to a minor degree in granitoid rocks in the Andes. Differential wetting and drying, hydration of feldspar to clay minerals, and removal of waste by wind are believed to be the causal processes. Hollowed-out exfoliated blocks and similarly sculp- tured bedrock outcrops are picturesque landscape fea- tures of the Atacama Desert of northern Chile. Excep— tionally fine cavities are developed in spheroidally ‘ weathered granitoid rocks of the area near Caldera (approximate 27° S.), along the marine terrace that borders most of the coast of northern Chile, but occur- rence of the cavities is not restricted to the coastal area, nor to granitoid rocks. Similar cavities are also found in the foothills of the Andes, and in the high Cordillera (fig. 1), in both granitoid rocks and in, argillite. Openings in the rock are of all sizes from pits a few centimeters in depth and diameter to caves large enough to shelter several people (fig. 2). The smaller cavities tend to develop on sloping surfaces, where they form a wafilelike pattern (fig. 3). The large caves develop in vertical faces. The shapes of the cavities are typically spheroidal (Segerstrom, 1962, fig. 93.4), but ellipsoidal and spiral-like forms (fig. 4) are common. A few of the openings have perforated the opposite wall of some outcrops, forming windows or small natural bridges. Many of the cavities are in pairs resembling owl’s eyes. Walls around the openings are almost paperthin in places; at other places they are more than a meter thick. Intersections of the cavities with each other and with 1 Geologist, Instituto de Investigaciones Geolfigicas de Chile. the outer surfaces of the rock have produced monoliths and other bizarre forms; the appearance of some out- crops is reminiscent of Swiss cheese. Exposure of the cavities is not restricted to a single orientation nor to a small range of orientations, but the largest openings tend to be on the windward side (west to southwest) of bedrock outcrops or exfoliated blocks. The cavities are in rock surfaces ranging in steepness from vertical to gently sloping and may be found either in the base or top of the exposure; however, the largest openings are in vertical or nearly vertical faces and near the base of the outcrops. TAFONI IN AREAS OUTSIDE C’HILE The Corsican term “tafoni” (singular, “tafone”) has been adopted for cavities in rock faces (Penck, 1894, p. 214) and is a suitable term for cavities observed in the Atacama Desert. The term has had wide accept- ance in foreign literature (Cotton, 1948, p. 8—11, pl. III), particularly in French, where the spelling is “taf- foni,” and in German-language publications. Oddly enough, this useful term does not appear in American literature or even in those glossaries and dictionaries that have been published in the United States. Tafoni in granitic rocks have been described from many arid and semiarid regions of the world. Low granite hills on the east side of Rogers playa, in the Mojave Desert of southeastern California (Black- welder, 1929, fig. 4), are pitted with cavities apparently identical with those of Chile. Tafoni in granite are also cited from the Tule and Tinajas Altas Mountains of Arizona (“niches”, Bryan, 1923, p. 49), the Sierra de Dolores of west Texas (Walther, 1892, p. 58), and from the islands of Elba (Wilhelmy, 1958, p. 159—163), Corsica (Kvelberg and Popoif, 1937), and Sardinia U.S. GEOL. SURVEY PROF. PAPER 501—C, PAGES C121—C125 0121 GEOMORPHOLOGY AND PLEISTOCENE GEOLOGY C122 71 “ 70° 69° :' I X x ADP/ANITAS Llano de Caldera X 0 lo . b 0 0019““) e Y‘ Quebrada del Bm‘tre)? gt? / Tierra I On Cerro ~11 Lagmm de 64?:qu $.36“ Bdil Amarl a Negro Francisco I UI re / l / W m/2 H “’ S N film .- O/ C: 3/ D: V [ 50 KILOM ETERS 0 10 2O 3O 40 FIGURE 1.—Index map of Chile between lat 27° and 28° S. x, tafoni localities. The FIGURE 3.—Cavities in granite 19 km north of Caldera. smaller pits exhibit a wafflelike pattern on sloping faces of the outcrop. FIGURE 2.—Large cave in granite about 15 km south-southwest of Caldera. Scale is shown by the human hand that proj- ects from a small cavity in the roof. SEGERSTROM AND HENRiQUEz '5‘ " FIGURE 4.—Spiral-1ike series of cavities in a granitic outcrop about 19 km north of Caldera. (Pelletier, 1962, p. 192—193). Other tafoni-in-granite localities have been reported in northern Portugal (Neiva, 1940), the central Sahara (Schwarzbach, 1954), Korea (Wilhelmy, 1958, p. 152), northeastern Brazil (Tricart and Cailleux, 1960), and Uruguay and west- ern Argentina (Wilhelmy, 1958, p. 170—17 5). Tafonvi are also found in other types of rock. The cavities have developed in rhyolite tufl" and conglom- erate of the southwestern United States (Blackwelder, 1929, p. 393 and fig. 1), trachyphonolite lava of the A‘haggar volcano of north Africa (Termier and Termier, 1960, fig. 50) , and volcanic breccia of the North Island of New Zealand (Bartrum, 1936; Cotton, 1942, pl. III—1). Bryan (1923, p. 51) describes niches in conglomerate in Arizona, and Cotton (1948, pl. III— 2) depicts t'afoni in conglomerate in New Zealand. Cavities in rock faces of the cold deserts at polar lati- tudes have similarly been termed “tafoni.” In north- west Greenland the hollows are in diabase sills (Davies and others, 1963, fig. 16), in southern Greenland they form in granite (Nordenskjiild, 1914, p. 517), and on the western slope of the Hekla-Hook Mountains in Spitzbergen they are found in siliceous rock (Blanck and others, 1928, p. 669). In Antarctica, granite and gneiss glacial erratics exhibit tafoni as much as a meter or more in depth in Victoria Valley, where the mean annual precipitation is 70 to 100 millimeters (Calkin and Cailleux, 1962). Cavernous weathering of boul— ders has also been described from other localities in An- arctica (Philippi, 1912; Nichols, 1953; Avsyuk and others, 1956). Locally, through overlapping, the pits have produced mu‘shroomlike and other bizarre skeletal forms (Calkin and C'ailleux, 1962; Nordenskjold, 1914). 732—760 0—64———9 Cl23 FIGURE 5.—Cavities in well-foliated argillite near Quebrada Seca, 56 km south of Caldera. o TAFONI IN NORTHERN CHILE The tafoni near Caldera, Chile, are in granitoid rocks, of generally homogeneous composition and tex- ture, composed of plagioclase, quartz, orthoclase, and biotite, with minor accessory minerals. The grains range in size from 0.5 to 2.5 mm. Xenol'it‘hs of diorite and gab‘bro are present, but their exposures are of re- latively small extent. Near Quebrada Seca the pits are in argillite (figs. 1 and 5), but they are not as large and abundant as those which have been formed in the granitoid rocks near Caldera. Tafoni are also found in the foothills of the Andes (for example, Quebrada del Buitre) or in the high Cordillera (fig. 1). A low hill of weathered grano- diorite on the north side of the Quebrada del Buitre, 4 km west of Tierra Amarilla (fig. 1) is covered with a lag deposit, several hectares in extent, that consists of ex- foliated blocks of homogeneous, coarse-grained gran- odiorite as much as 3 or 4 meters in diameter. Many of the blocks, particularly those which are on the top and windward sides of the hill, contain round cavities a meter or more in diameter resembling the potholes of a riverbed (Segerstrom and Ruiz, 1962, p. 62). Some of the blocks are completely perforated.1 The cavities are developed in outcrop faces of diverse orientation, but most of the largest ones open toward the southwest, or windward side. On the northern summit of the Cerro del Buitre, 3.7 km west of the Quebrada del Buitre 1 R. I. Tilling, 1962, Bathollth emplacement and contact meta- morphism in the Paipote—Tierra Amarilla area, Atacana province, Chile: Yale Univ., Ph. D. dissert, 202 p. 0124 GEOMORPHOLOGY AND locality and about 600 In higher, a block of fine-grained granite is perforated by a natural hole 30 centimeters in diameter. In the. Cordilleran valley of the Rio de la Gall‘ina (fig. 1), at an altitude of 3,600 m above sea level, large boulders of pyroxene diorite porphyry con- tain rounded cavities as much as 75 cm in diameter. The climate of the western and central parts of the Atacama Desert is dry and temperate in the winter, dry and subtropical in the summer; the slightly less arid eastern part is cool to cold at altitudes above 2,000 m. Throughout the area there are greater differences of temperature between day and night than between win- ter and summer. During most nights a fog called “camanchaca” forms over the coastal area, drifts inland up the principal valleys to altitudes of 750 m or more above sea level, and is usually not dissipated until mid— morning. Typically the afternoons are clear and windy, with the prevailing winds from the west—southwest. In summer the winds often attain high velocities. At dusk the west wind dies and is often supplanted by an east Wind, of much less velocity. At Copiapé (fig. 1) the average temperatures range from 23°C in summer to 13°C in winter, and the maximum and minimum tem- peratures are 32°C and —2°C. During the period 1911—60 the mean annual precipitation at Copiapo was only 25 mm (Segerstrom and Ruiz, 1962, p. 11). Rain— fall along the coast is little if any greater than that at Copiapé (altitude 380 m), but at high altitudes in the eastern part of the area shown in figure 1 the precipita- tion is perhaps 3 or 4 times as great, practically all of it in the form of snow. Tafoni observed in the Atacama Desert tend to have damp interiors and dry exteriors much of the time, be- cause of shading of the interior and exposure of the ex- terior to the sun. Near the coast and in Quebra-da del Buitre, where the cavities are best developed, the source of moisture is early morning fog; at higher altitudes the source is not known. The interior walls are scaly and crumbly, whereas the exterior surface of the rock is sound. The hard faces of outcrops are fresh and not noticeably impregnated with iron; the relatively soft inside walls exhibit thin coatings of white clay minerals on many of the feldspar grains. In the granite there is no readily visible joint control of cavities, nor do tex- tural and compositional differences seem to be influen- tial. F inc—grained mafic inclusions in the granite, likewise, have no apparent relation to the distribution of tafoni. The less homogeneous argillite, on the other hand, exhibits some bedding-plane control of the tafoni. CAUSES OF TAFONI The formation of tafoni has been ascribed to the fol. lowing physical processes by the authors who have been PLEISTOCENE GEOLOGY cited: scouring by wind, beating of rain, insolation, freezing and thawing, differential expansion and con- traction of curved surfaces, differential humidity be tween exterior and interior of cavities, and burrowing by animals. Chemical processes believed to be respon— sible for cavities in rock faces are solution of certain minerals, crystallization of salt introduced by sea air, case hardening of the exterior by impregnation with iron oxide, and hydration of feldspar and other min- erals with related chemical changes. Some authors maintain that the size, shape, and orientation of t’afoni are controlled by joint system's, bedding, foliation, and other structures, as well as by small differences in tex- ture and composition of the rock. It has been held that formation of the hollows takes place either in a coastal climate which is periodically damp and subject to frequent winds or one with long dry seasons and high temperatures (Wilhelmy, 1956, p. 55). A plausible hypothesis which has been advanced for development of the rock cavities in the southwestern United States seems equally applicable to the Chilean occurrences. The explanation is in part the same as that which has been advanced for exfoliation; namely, that the hydration of feldspar and other minerals plays a major role (Blackwelder, 1925, p. 793). Dampness promotes hydration, and hydration may produce new minerals of larger volume (principally clay minerals) ; hence, rupture due to katamorphism is more prevalent in moist rocks than in dry rocks (Blackwelder, 1925, p. 805—806). Normally, sunshine dries out the lower part of the cavity sooner than the more shady upper part, thus favoring the inward and upward growth of the cavity (Blackwelder, 1929, p. 396). The results of fieldwork in Corsica and detailed petrographic studies of Corsican samples suggest that cavity formation in granite is a result of differential expansion and con- traction of curved surfaces; that is, a physical process more than a chemical one (Kvelberg and Popoff, 1937). Once a cavity has started, differential humidity and a resulting hydration probably could produce the required differential expansion and contraction of concentric “shells” in the wall surrounding the cavity. Wind may assist in removing the debris, but it is probably a minor agent in development of the cavities (Bryan, 1923, p. 49). In the Atacama Desert and in the southwestern United States the abrasive action of windblown sand has produced polishing, pitting, and grooving of outcrops and boulders (Segerstrom, 1962, fig. 93.2; Blackwelder, 1929, fig. 3), but such phenomena are absent in the tafoni of those regions. Despite state- ments that the rocks were hollowed out by sandblasting (Segerstrom, 1962, p. 91 and 93), the conclusion is inescapable that the role of the wind is more important SEGERSTROM AND HENRiQUEz in the removal of particles already loosened by other processes than in actual abrasion of the inner walls of niches (Bryan, 1923, p. 49; Blackwelder, 1929; Tri- cart and Cailleux, 1960). In closing, the authors wish to acknowledge the help of Roland Pascofi', of the Instituto de Geografia, San- tiago, Chile, who supplied numerous bibliographical references. REFERENCES Avsyuk, G. A., Markov, K. K., and Shumsky, P. A., 1956, Geo- graphical observations on an Antarctic “oasis”: Moscow, USSR. Natl. Comm. for Internat. Geophys. Year 1957—58, Acad. Sci., Antarctic Council, 69 p. Bartrum, J. A., 1936, Honeycomb weathering of rocks near the shoreline: New Zealand J our. Sci. and Technology, p. 593— 600. Blackwelder, Eliot, 1925, Exfoliation as a phase of rock weather- ing: J our. Geology, v. 33, p. 793—806. 1929, Cavernous rock surfaces of the desert: Am. J our. Sci., 5th sen, v. 17, p. 393—399. Blanck, E., Rieser, A., and Mortensen, Hans, 1928, Die wissen- schaftlichen Ergebnisse einer bodenkundlichen Forschungs- reise nach Spitzbergen im Sommer 1926: Chemie der Erde, v 3, p. 588-698. Bryan, Kirk, 1923, Erosion and sedimentation in the Papago country, Arizona, with a sketch of the geology: U.S. Geol. Survey Bull. 730—B, p. 19—90. Calkin, P, and Cailleux, Andre, 1962, A quantitative study of cavernous weathering (taffonis) and its application to glacial chronology in Victoria Valley, Antarctica: Zeitschr, f. Geomorph., v. 6, p. 317—324. Cotton, G. A, 1948, Climatic accidents in landscape making, a sequel to landscape as developed by the process of normal erosion: New York, John Wiley and Sons, Inc, 354 p. Davies, W. E., Krinsley, D. B., and Nicol, A. H., 1963, Geology of the North Star Bugt area, northwest Greenland: Copen- hagen, Meddeleser om Gr¢nland, v. 162, no. 12, 68 p. 0125 Kvelberg, Irma, and Popoff, Boris, 1937, Die Tafoni-Verwit- terungserscheinung: Riga, Acta Universitatis Latviensis, Fac. of Chem, ser. 4, no. 6, p. 129-370. Neiva, J. M., 1940, Alguns aspectos erosivos dos granitos do Norte de Portugal: Pub]. do Museu e Laboratério Minera- légico e Geolégico da Fae. de Ciencias do Porto, v. 14, p. 1—8. Nichols, R. L., 1953, Geomorphology of Marguerite Bay, Palmer Peninsula, Antarctica: Washington, US Office of Naval Research, Ronne Antarctic Research Exped., Tech. Rept. 12, 151 p. N ordenskjold, Otto, 1914, Einige Zuge der physischen Geographie und der Entwicklungesgeschichte Sudgro'nlands: Geogr. Zeitschr., p. 425—441,505—524, 628—641. Pelletier, Jean, 1962, Le relief de la Sardaigne: Annales de Ge- ographie, no. 384, p. 192—193. Penck, Albrecht, 1894, Morphologie der Erdoberfliiche: Stutt- gart, v. 1. Philippi, E., 1912, Geologische Beschreibung des Gaussbergs: Deutsche Siidpolarexpedition, 1901—03, hrsg., v. E. v. Dry- galski, v. 2, p. 47—71. Schwartzbach, Martin, 1954, Geologie in Bildern; eine Einfiir— ung in die Wissenschaft von der Erde: Wittlich, Georg Fischer Verlag, 132 p. Segerstrom, Kenneth, 1962, Deflated marine terrace as a source of dune chains, Atacama province, Chile: Art 93 in US Geol. Survey Prof. Paper 450—0, p. 091—093. Segerstrom, Kenneth, and Ruiz, Carlos, 1962, Geologia del cuad- rangulo Copiapoz Santiago, Instituto de Investigaciones Geologicas, Carta Geolégica de Chile, v. 3, no. 1, 115 p. Termier, Henri, and Termier, Genevieve, 1960, Erosion e1: sedi- mentation: Paris, Masson, 412 p. Tricart, Jean, and Cailleux, Andre, 1960, Le modelé des regions seches: Paris, Centre de Documentation Universitaire, 308 p. Walther, Johannes, 1892, Die nordamerikanischen Wiisten: Berlin, Verhandl. d. Ges. f. Erkunde, p. 52—65. Wilhelmy, Herbert, 1956, Cavernous rock surfaces (taffoni) in semi-arid and arid climates: Internat. Geog. Cong., 18th, Rio de J aneiro, Abstracts of Papers, p. 55-56. 1958, Klimamorphologie der Massengersteine: Braun— schweig, Westermann Verlag, 238 p. GEOLOGICAL SURVEY RESEARCH I964 NEGAUNEE MORAINE AND THE CAPTURE OF THE YELLOW DOG RIVER, MARQUETTE COUNTY, MICHIGAN By KENNETH SEGERSTROM, Denver, Colo. Abstract—The Negaunee moraine of Wisconsin age borders the Yellow Dog Plains on the Upper Peninsula of Michigan and marks a zone Where ice blocked “the preexisting drainage t0 the north and east. A glacial stream that drained southward to Dead River was captured in postglacial time by the east- flowing Yellow Dog River. Headward cutting of the north- flowing Salmon Trout River now threatens to capture head- waters of the Yellow Dog River. The Yellow Dog Plains, a terracelike sandy area about 10 miles long and 2 to 3 miles wide, is an eye—catching topographic feature among the generally knobby land- forms northwest of Marquette, on the Upper Penin- sula of Michigan (fig. 1). A steep escarpment lacking bedrock exposures drops to the north as much as 400 feet below the surface of the plains, and a highland to the south—marked by dozens of rock knolls—rises as high as 400 feet above the plains. A narrow lowland at the base of the escarpment is bordered to the north by a belt of granitic hills known as the Huron Moun- tains. As explained below, a gap in the southern high- land near Pinnacle Falls formerly permitted a glacial stream to discharge southward along Mulligan Plains, but drainage is now directed north and east—via the Salmon Trout and Yellow Dog Rivers (figs. 1 and 2). The drainage history, beginning with the ice—con- tact origin of the plains and concluding with post- glacial drainage changes, is summarized below. The highly irregular escarpment and the lowland at its base were mapped by Leverett (1929, pl. 1) as part of a morainal belt extending from Marquette to Kewee- naw Bay, a little west of the area of figure 1. This belt, currently termed the Negaunee moraine (Flint and others, 1959), is on the western limb of the Green Bay Lobe of Wisconsin Drift (Martin, 1957), and it is assigned to the Mankato Stade. The vaguely defined Negaunee moraine, although marked locally by kame- and-kettle topography, is characterized by its negative geomorphic aspect. Thus, it is not a typical end Qefid River S to/ragXBasin Champion 46 ° 0 30' Ish emin- O p - O Nega/uéee O 5 10 MILES FIGURE 1.—‘Index map of area northwest of Marquette, Mich., showing location of area of figure 2 (outlined). Shaded area is Negaunee moraine, after Martin (1957). moraine, a “ridgelike accumulation of drift built along any part of the margin of a glacier” (Flint, 1957, p. 131 and fig. 7—19). Near the Yellow Dog Plains the moraine is part of a thick accumulation of sand and other materials, locally studded with kames or pitted with small kettles; elsewhere, it consists mostly of thin drift dotted with numerous bedrock knobs and a few small gravelly kames. Near the Yellow Dog Plains there is a pronounced change in size of particles in the Negaunee moraine. The materials at the base of the escarpment to the north are extremely heterogeneous; particles of all sizes are present, but in only a few places is clay sufficiently U.S. GEOL. SURVEY PROF. PAPER 501—C. PAGES C12le9 C126 SE GERSTROM .n/{l ' N .MOUNTA :1 ‘ 0127 87°45’ FIGURE 2.—Topographic map of Yellow Dog Plains and vicinity, showing location of sections A—A’ and B—B’. Geological Survey Huron Mountain and Champion 15-minute quadrangle maps. abundant to cement the materials to a hard, typically till-like consistency. Southward, the morainal mate- rials grade into coarse- and medium—grained sand con- taining scattered cobbles and boulders at the upper edge of the escarpment (fig. 3) . On the Yellow Dog Plains the boulders diminish in number southward, and the sand becomes finer and better sorted. Near the southern edge of the plains no boulders are seen, and very little of the surficial mate rial is finer or coarser than medium-grained sand. From US. The late-glacial history of the area is generally as follows: Prior to the last glaciation the ancestral Yel- low Dog River evidently flowed eastward in a broad valley eroded in slate and bordered on the north and south by relatively hard crystalline rocks. During the Mankato( ?) Stade the area was covered by a conti- nental glacier of unknown thickness. Locally the ice was thickest over the valley immediately south of the Huron Mountains; therefore, during stagnation the margin of the glacier temporarily stood there. Melt C128 2000’ 1500’ Yellow Dog River Gneiss and schist YELLOW DOG PLAINS GEOMORPHOLOGY AND PLEISTOCENE GEOLOGY NEGAUNEE MORAINE 1000' B 1500’? Pinnacle Falls (Yellow Dog River) BEND IN SECTION BEND IN SECTION MULLIGAN PLAINS Granite, gneiss, and sclhist "/ ‘ | Slate : I East Branch Salmon Trout River b? YELLOW DOG PLAINS NEGAUNEE MORAINE Slate 1000' 0 FIGURE 3.—Cross sections A—A’ and B—B’. 5000 10,000 FEET Location of sections is shown on figure 2. Swamp deposits shown as solid black. Vertical exaggeration about X 10. water deposited kames on the underlying ground— moraine surface, and spilling southward constructed a broad kame terrace—the Yellow Dog Plains. The flow of melt water was obstructed by the high bedrock hills to the south, causing brief ponding, until increas- ing depth of the water permitted it to breach a gap near the present Pinnacle Falls. Erosion of the gap resulted in drainage of the lake. Along the north and east edges of the kame terrace, where glacial and outwash materials were interlayered, bedding features were largely destroyed through col- lapse caused by melting of the underlying blocks of stagnant ice. This produced debris slopes ranging in steepness from 15° or 20° near the top of the section to 1° or 2° near the bottom, accounting for the concave— upward profile at the ragged edge of the plain. The Negaunee moraine was thus formed; locally it consists of debris slopes interrupted by scattered kames and kettles. The capture of the Yellow Dog River came about as follows: After the terrain between the Yellow Dog Plains and Lake Superior was deglaciated, the former drainage systems were reactivated. The Salmon Trout and Yellow Dog Rivers reexcavated their old channels or incised new ones in their drift—covered lower valleys and soon cut headward into the Negaunee moraine. The steep slope of the moraine resulted in unusually rapid headward cutting by streams consequent on the newly exposed land surface. Meanwhile, the glacial drainage—southward through the Mulligan Plains to the Dead River—survived briefly, but with the loss of melt water this drainage system must have become very sluggish and was therefore a less effective cutting agent than the revived Yellow Dog River to the north- east. Inevitably, through stream capture, most of the drainage of the Yellow Dog Plains was diverted east- ward, and the Yellow Dog River acquired its present course. The river, superposed upon the sand plain, cut into bedrock at the present Pinnacle Falls. This indicates that the present river channel occupies a posi- tion on the shoulder of the ancestral valley (fig. 3, sec— tion B—B’). Near Pinnacle Falls the river has cut an exceptionally steep, narrow gorge that extends down- SEGERSTROM stream for about 2 miles. Except at the falls, the walls of the gorge are almost entirely sand, and they slope as much as 26° or 27° (the angle of repose for this mate- rial is about 33°). With disappearance of the ice from the Huron Moun- tains and Negaunee moraine area, the Salmon Trout River cut headward across the plains. Because the divide between this stream and the Yellow Dog River is today less than 20 feet high and the Salmon Trout is at a lower elevation, beheading, or capture, of the Yel- low Dog River is imminent. 0129 REFERENCES Flint, R. F., 1957, Glacial and Pleistocene geology: New York, John Wiley, 553 p. Flint, R. F., chm, and others, 1945, Glacial map of North America : Geol. Soc. America Spec. Paper 60. 1959, Glacial map of the United States east of the Rocky Mountains: New York, Geol. Soc. America. Leverett, Frank, 1929, Moraines and shore lines of the Lake Superior Basin: U.S. Geol. Survey Prof. Paper 154—A, 72 p. Martin, H. M., 1957, Map of the surface formations of the northern peninsula of Michigan: Michigan Geol. Survey Pub. 49. GEOLOGICAL SURVEY RESEARCH I964 ANCIENT LAKE IN WESTERN KENTUCKY AND SOUTHERN ILLINOIS By WARREN |. FINCH, WILDS W. OLIVE,- and EDWARD W. WOLFE, Paducah, Ky.; MenIo Park, Calif. Work done in cooperation with the Kentucky Geological Survey Abstract.—Elongate, narrow, round-crested gravel ridges with accordant crests at an altitude of about 355 feet above sea level suggest that during late Pleistocene time a lake occupied the valley of the Ohio River and its tributaries near the confluence of the Ohio and Tennessee Rivers. Accordant gravel ridges found in the valleys of the Ohio, Tennessee, and Clarks Rivers in an area extend- ing at least 40 miles up the Ohio and Tennessee Rivers from Metropolis, 11]., indicate that a lake flooded these valleys below an altitude of 355 feet at some time in the late Pleistocene. The evidence consists of elongate, narrow, round-crested ridges believed to represent former bay-mouth bars and beach ridges, composed of gravel, which rest on presumed lacustrine deposits of loess-like silt. The crests of the ridges are accordant at altitudes of slightly more than 350 feet, 5 to 20 feet above an extensive silt deposit whose upper surface lies at altitudes between 330 and 350 feet and which presumably represents an old lake bed. The distribu- tion of the ridges is shown on figure 1. Most of the ridges are along the margins of the old lake bed through which the Ohio, Tennessee, and Clarks Rivers flow, and most cross the mouths of the tribu— taries of these rivers. Typically, a long segment abuts against the downriver wall, and a short segment abuts against the upriver wall; the tributary flows between the two segments (fig. 2). A swale 2 or 3 feet below the general level of the crestline is common where the long segment joins the valley wall. Other gravel ridges are found at the base of adjoining upland slopes and are separated from the uplands by a swale 2 or 3 feet be- low the general level of the ridge crestline. The ridges are generally 200 to 500 feet wide, a few hundred feet to as much as a mile long, and 5 to 20 feet high. The gravel of the ridges consists Chiefly of poorly sorted subrounded chert pebbles and cobbles rarely larger than 3 inches in diameter, and sparse small rounded quartz pebbles. Matrix material generally is clay or silt, but the gravel in some ridges is nearly free of matrix material. Gravel also occurs in widespread continental deposits of Pliocene( ?) and Pleistocene age, which blanket adjacent uplands, but this older gravel has a matrix dominantly composed of sand and is easily distinguished from the ridge deposits. The gravel ridges overlie silt and clay deposits, which are believed to be of lacustrine origin. At depth these deposits contain sand and gravel in varying quantities, which may be in part alluvial in the Tennessee, Ohio, and Clarks River valleys. Drill holes west and north- west of Sy-msonia penetrated as much as 73 feet of un- consolidated material below gravel ridge deposits. None of the ridges are capped by loess, although Peorian Loess (Leighton and Willman, 1950) forms an extensive blanket on the adjacent uplands. Shaw (1911, p. 484,-; 1915, p. 147) described similar features, which he identified as beach ridges that de- veloped in a lake of late Quaternary age near Madison— ville, Ky., 65 miles east-northeast of Paducah. Ba‘y- mouth bars similar in form to those of the ancient lake are currently accumulating along the edges of Kentucky Lake, which was impounded in 1945. One of the bars is shown on figure 3. Although the modern bars are sim- ilar in form to the ancient bars, they differ in composi— tion in that they are composed of angular chert ru‘bble derived from erosion of wave-cut scarps in residuum of Paleozoic rocks, whereas the older bars are composed of subrounded chert gravel evidently derived mainly from erosion of Pliocene( ?) and Pleistocene continental deposits. The bases of the modern bars are above an altitude of 350 feet and their crests rarely rise more US. GEOL. SURVEY PROF. PAPER 501-0. PAGES (3130—0133 0130 C131 FINCH, OLIVE, AND WOLFE SM .3558 =aAmnaE and 63.26 .noxoauOoS 5 53:8 ecomémm 05 on“ mwuui figs...“ «o :oEaqulA BEBE ~Omoww _ wmnzz w a bimw / —_—__ —_ VHSHVW \\\\ coacom _ I100 sfiAvus _ _ Ammo 'I'I ' MN 098‘ H N 05m: :0 :muwu SEEM E :39? m9< an: .335» ES fifisd 3.33:0 :SfisaE ES» {$2 .233: ~33» 3.3.35 $.9de .Quugzi gawk? 3.3.3.0 :0E3:s$:ab SSW M15 .233: SQéwhé §8~3§Do§~ \e 2&3: $3. fiscxk $33 fie @3625 mvmflh $520 ilgmL ZO_._. bzmao‘. mequu we: a» x o .50 E265 Ho... 96.. »xosacoxv 9 Eco zxuacwv. yo cot—mug «NX/ flg >v. ODHZMX toaw‘. «o 33 mmqomomfimz 0132 GEOMORPHOLOGY AND PLEISTOCENE GEOLOGY _ 1‘4? CRAc_KEN CQUNTY GRAVES COUNTY _ ‘ Quaternary deposits " . Mainly silt of lacustrine origin. Includes: thin alluvium along major streams and above 360 feet gr, gravel ridge Quaternary and Tertiary deposits, undifferentiated Contact 350 Topographic contour line 36° 52' 30” 1 1/2 o 1 MILE 1 FIGURE 2.—Lacustrine deposits in part of the Symsonia quadrangle, Kentucky. FINCH, OLIVE, AND WOLFE FIGURE 3.-Modern gravel bar across a small bay of Kentucky Lake, east of Aurora, Ky. (photograph taken during low water level). ' than 1 or 2 feet above the normal level of Kentucky Lake, 359 feet above sea level. The approximate shoreline of the ancient lake in part of western Kentucky is indicated by the 350-foot con- tour as shown on figure 1. Although gravel ridges have been observed at an altitude of about 350 feet along the margins of the Ohio River lowlands in southern Illinois, the ridges have not been mapped; therefore, the extent of the lake in Illinois is not shown on figure 1. The lake probably extended down the Ohio to the vicinity of Metropolis, 6 to 8 miles northwest of Pa- ducah, as indicated by the distribution of the distinc— tive gravel ridges. The relation of ridge deposits to upland and lacus- trine deposits is illustrated on figure 2. The bay-mouth bars extending across the valley of the West Fork of Clarks River may have developed subsequent to the beach-ridge deposits farther upstream. A succession in the development of these deposits could have been caused by deltaic deposition above the bars which 5? 0133 caused shoal water, the site of gravel bar development, to migrate toward the middle of the lake. The townsite of Kaler is on an island hill surrounded by lacustrine deposits and accompanying ridge deposits, a type of feature that also was noted in the area of ancient lakes described by Shaw (1915, p. 156). The cause and exact age of the lake are unknown. The lake may have formed during the diversion of the Ohio River through the Metropolis Gap from its former Cache Valley course (Fisk, 1944, p. 39—40). Another possibility is that the Ohio may have been impounded near Metropolis either by rapid alluviation or by fault- ing. Absence of loess on the gravel ridges indicates a fairly young age, probably late Wisconsin. The sur- face on which PaduCah is situated, which is well within the area of the ancient lake, is described by Ray (1963, p. B127) as a terrace deposit that may be of Mankato age. REFERENCES Fisk, H. N ., 1944, Geological investigation of the alluvial valley of the lower Mississippi River: Vicksburg, Miss, Missis- sippi River Comm, 78 p. Leighton, M. M., and Willman, H. B., 1950, Loess formations of the Mississippi Valley: Jour. Geology, v. 58, no. 6, p. 599— 623; Illinois Geol. Survey Rept. Inv. 149. Leighty, W. J ., and Wyatt, C. E., 1950, 'Soil survey of Marshall County, Kentucky: U.S. Dept. Agriculture, Ser. 1938, no. 29, 109 p. 1953, Soil survey of Graves County, Kentucky: US. Dept. Agriculture, Ser. 1941, no. 4, 139 p. Ray, L. L., 1963, Quaternary events along the unglaciated lower Ohio River valley: Art. 33 m U.S. Geol. Survey Prof. Paper 475—B, p. B125—B128. Shaw, E. W., 1911, Preliminary statement concerning a new system of Quaternary lakes in the Mississippi basin: Jour. Geology, v. 19, p. 481—491. 1915, Newly discovered beds of extinct lakes in southern and western Illinois and adjacent States: Illinois Geol. Survey Bull. 20, p. 139—157. GEOLOGICAL SURVEY RESEARCH 1964 OUTLINE OF PLEISTOCENE GEOLOGY OF MARTHA'S VINEYARD, MASSACHUSETTS By CLIFFORD A. KAYE, Boston, Mass. Abstract—Six glacial drifts and the deposits of one inter- glaciation are recognized on Martha’s Vineyard. It is thought that these represent Nebraskan Glaciation, Aftonian Inter- glaciation, and Kansan, early Illinoian, late Illinoian, early Wisconsin, and late Wisconsin Glaciations. In addition, the terminal moraine of middle Wisconsin Glaciation is nearby, at the Elizabeth Islands, and the periglacial effects of this ice sheet are preserved on Martha’s Vineyard. The Pleistocene stratigraphy was worked out independently of earlier work and is in remarkably close agreement with the conclusions reached by Fuller and Woodworth a half century ago. The following discussion and the diagrammatic cross section (fig. 2) summarize the major conclusions that the author has reached concerning the stratigraphic divisions of the Pleistocene deposits of Martha’s Vine- yard, an island just off the coast of Massachusetts. The conclusions are the result of a field study begun in 1957 that will be reported on more fully later. Early workers on the glacial deposits of the southern New England islands recognized the existence of a complex stratigraphic sequence of drifts. Fuller (1914) distinguished 7 drift units and 1 interglacial unit on Long Island, comprising all 4 glacial stages of the Pleistocene. Woodworth' and Wigglesworth (1934) recognized approximately the same sequence on Martha’s Vineyard. However, the conclusions of these earlier workers were later questioned (for example, Flint, 1947, p. 296), and in recent decades most pub- lications on the Pleistocene geology of eastern North America have tried to explain all deposits as the product of Wisconsin Glaciation. The writer approached the geology of Martha’s Vineyard with few preconceptions, working independ- ently of the results of earlier writers. He soon became convinced, however, that deposits and structural effects of several ice sheets that apparently represent a wide time range are present. The problem of arranging the drifts in stratigraphic order was complicated by the fact that most of the deposits are fragmentary. No single exposure contains the entire section, and the 70°30’ l MARTHA’S VINEYARD / .‘ Wequobsque \J Cliff Squibnocket Point Il ' 7 Area of Nomans "vgrepon 15' 0 5 10 MILES L_A_J__L_L__I.—-—I FIGURE 1.—Map of Martha’s Vineyard and surrounding islands, showing localities and inferred ice margins referred to in text. Iice markins: 11, early Illinoian; 12, late Illinoian; W1, early Wisconsin; and Wz, middle Wisconsin. See figure 1 of the following article (p. 0141) for location of mapped m0- raines on Martha’s Vineyard. stratigraphic sequence had to be put together piecemeal by a series of comparisons between widely separated outcrops. Moreover, the deposits are almost every- where very much deformed by glacially produced thrust faulting and some folding. Thus, deposits that were laid down as much as several miles apart have been telescoped together by the glacial imbrication. This complicated the recognition of facies differences and variations of the type to be expected within a single drift. A series of value judgments had to be made as to whether differences in adjacent deposits were due to faulting, differences in age, or compositional and tex- tural variations within a single drift. When all the fragments were pieced together, how- ever, there was strong evidence of 6 drifts and the periglacial effects of a 7th glaciation, thought to be that which produced the nearby Elizabeth Islands mo- raine several miles to the northwest (fig. 1). Moreover, U.S. GEOL. SURVEY PROF. PAPER 501-0, PAGES Cl34-C139 0134 KAYE sediments deposited during an interglacation are pres- ent, and the weathering and erosional effects of several other interglaciations have been deduced. This con- firms the deductions of Fuller (1914) and Woodworth and Wigglesworth (1934) as to the number of drifts and interglacial deposits present. The writer differs with these earlier workers, however, on the strati- graphic position of some of the deposits; therefore, in the following brief account only stage names are used. The drifts were assigned ages by matching them with all the known major glacial stages and substages of the upper Mississippi Valley, working back from the late Wisconsin and taking into account the lengths of in. terglacial intervals as suggested by weathering effects and interglacial deposits. It is recognized that this method leaves much to be desired as a means of corre- lation, and therefore must be considered as a provisional interpretation, at best. Nonetheless, it is apparent that Martha’s Vineyard possesses one of the most complete sections of Pleistocene deposits known, and possibly the most complete and varied within the confines of such a small area (81 sq mi). NEBRASIKAN DRIFT Nebraskan drift consists of a till that has been recog- nized at only one locality on Martha’s Vineyard, the eastern part of Wequobsque Clifi' (fig. 1), where it overlies greensand of Miocene age and attains a max- imum exposed thickness of 20 feet. It is very compact and well graded in the clay to fine-gravel size range; clasts larger than 3 inches are very rare. It is light gray (dry) or medium gray (moist), and is massive in the upper part but thinly banded or stratified in the lower part. About 97 percent of the coarse clasts in the till consist of quartz pebbles and nodular rocks derived from Tertiary and Cretaceous coastal-plain sediments, which are exposed on Martha’s Vineyard; thus only 3 percent are derived from crystalline rocks of the New England upland. This is significant because the per- centage of crystalline rocks of New England upland provenance increases in successively younger tills. The sand, silt, and clay show by their mineral composition that they, too, are largely reworked coastal—plain sedi- ments. At two places in the cliff the upper part of the till has been profoundly altered by weathering to a maxi- mum depth of 13 feet beneath sand of early Illinoian age. This old truncated regolith (which, like most interglacial weathering profiles, has been partially to completely removed by later glacial erosion) is nearly white. Study of the clay mineralogy by John Hatha- way, US. Geological Survey, showed that the regolith is considerably richer in kaolinite than the unweathered C135 till from which it was derived. Little can be deduced about the direction of movement of the Nebraskan ice, although dark-gray phyllite pebbles in the till, which resemble rocks in southern Rhode Island, suggest south- east or east-southeast movement. There is no evidence indicating the maximum extent of the ice sheet, This till was not recognized by Woodworth and Wiggles- worth and may not have been exposed in their day. AFTONIAN DEPOSITS Deposits of probable Aftonian age consist of several bodies of quite dissimilar sediments that are thought to represent both marine and nonmarine depositional fa— cies in a coastal area (fig. 2). In eastern Wequobsque Cliff there is a bright pistachio—colored greensand inter- bedded with quartzose gravel (the content of crystalline rock pebbles is about 2 percent of the total pebbles) containing reworked Miocene shark teeth and other fossils. In Wequobsque Clifl’ these sediments overlie the Nebraskan till. The greensand does not resemble the Miocene greensand or the glauconitic fine sand of Late Cretaceous age, both of which crop out on the island. The glauconite may therefore be authigenic; an attempt is being made to date it by the potassium- argon method. Cropping out in the central part of Gay Head Cliff is a massive bed that consists mainly of reworked Miocene and Cretaceous sand, gravel, and fossils, which in part is loosely cemented by phosphate. This peculiar bed was called the Aquinnah Conglomer- NORTH SOUTH z/wrtm~\\\ W1 outwash W1 till W1 sa .- . W I, till |1 sand Upper Cretaceous and Tertiary FIGURE 2,—Diagrammatic north-south cross section through Martha’s Vineyard, showing succession of drifts and their spatial relationships. Symbols: N, Nebraskan; A, Aftonian; K, Kansan; 11, early Illinoian; 12, late Illinoian; W1, early Wisconsin; W3, late Wisconsin; gs, greensand ; g, gravel. The serrated contact between early Illinoian and late Illinoian till indicates imbrication of all older deposits by late Illinoian ice. 0136 GEOMORPHOLOGY AND ate by Woodworth and Wigglesworth (1934), and al- though it strongly resembles the Miocene deposits of Gay Head, its Pleistocene age was established by the finding of the bone of a Pleistocene horse. This odd sediment is probably talus that accumulated on the lower slopes of a sea clifl' that was cut into Miocene and Upper Cretaceous sediments in Aftonian time. In the southern part of Gay Head it can be seen grading into greensand and quartzose gravel very similar to those of Wequobsque Clifl'. In south and central Gay Head these sediments unconformably overlie white clayey coarse sand of the Raritan Formation of Late Cre- taceous age; in some places they underlie Kansas till, and in others sand of early Illinoian age. The Aquinnah Conglomerate and the greensand— quartzose gravel complex are not found in the northern part of Gay Head. Instead, a massive ferruginous clay and fossiliferous glauconitic sand lie between Miocene greensand and Kansan drift. Mollusks from the sand were studied by Dall (1894), who dated them as Plio— cene. More recently Raup and Lawrence (1963), work- ing with another collection of shells, considered the fauna to be Pleistocene. Further study is being carried on to resolve the difference of opinion. At this stage of the study, one can only suggest that if these deposits are Pleistocene in age they probably are equivalent to the greensand and gravel to the south. KANSAN DRIFT Kansan drift is found at several places in Gay Head Clifl' overlying the Aquinnah Conglomerate, the Plio- cene or Pleistocene fossiliferous sand, or where this is missing, Upper Cretaceous or Miocene sediments. It is also exposed in the cliff in the northern end of Lam- berts Cove and in several sand and gravel pits in the interior of the western part of the island. It is a com- pact, medium—gray to greenish—gray till that is poor in cobbles and boulders. However, a lag deposit of boulders, mostly of crystalline rocks (termed the “Dukes boulder bed” by Woodworth and Wigglesworth, 1934), marks the stratigraphic position of the Kansan drift in a few places in Gay Head Cliff. The content of crys- talline rocks in the till is higher than in the Nebraskan till, but nodular sedimentary rocks (siderite, dolomite, limestone, and phosphorite) frOm the coastal—plain sediments make up 60—80 percent of the clasts larger than 1 inch. In the lag gravel the content of crystalline rocks is higher, mainly because these rocks are generally harder and more durable than the nodular rocks. In Lamberts Cove Clifl', Kansan till is oxidized beneath its contact with overlying sand of the Illinoian drift to a depth of more than 40 feet. In the northern part of Gay Head, lag pebbles and boulders of Kansan till are deeply PLEISTOCENE GEOLOGY wind cut and polished where they are overlain by basal fine sand (eolian '9) of the Illinoian drift. In other places, some of the crystalline boulders are much de- composed. The direction of movement of Kansan ice is deduced from very tenuous evidence as having been al- most due south. There is no evidence as to the maximum extent of the Kansan ice sheet. ILLINO‘IAN DRIFT The patchy Kansan till is overlain by a widespread and varied sequence of sediments that are thought to be Illinoian in age. The Illinoian drift is divided into a lower unit of sorted, stratified sediments overlain by till, believed to be of early Illinoian age, and an upper till that may represent late Illinoian Glaciation. In the central and northern part of Gay Head Clifi' and in several pits in the interior of the island the basal Illinoian drift consists of fine—grained light-gray lami- nated sand that grades up into crossbedded, somewhat glauconitic, uniform fine to medium sand and finally up into a somewhat quartzose gravel. In the southern part of Gay Head Clifl' and in Lamberts Cove, the basal Illinoian consists of glauconitic sand and quartz- ose gravel that somewhat resemble the Aftonian se- quence of Wequobsque Cliff. In the southern part of Gay Head Clifl’, in Squibnocket Clifl', and in the cliff of Nomans Land (fig. 1), the basal Illinoian is brown to gray clay and silt overlain by fine to medium sand. There is no evidence of weathering of any of these basal deposits beneath Illinoian till. These sorted, basal sediments are unfossiliferous (except for fossil-s that were obviously reworked from Miocene beds) and for the most part are probably non— marine. The glauconite is probably reworked from older greensand. Indeed, in texture and type of bedding and crossbedding, some of the deposits resemble out- wash sand and gravel, and eolian sand. The thick clay- sand sequence may be marine and quite comparable to the clay—sand sequence at the base of the Wisconsin drift, which is thought to be a marine deposit made up of rock flour and sand derived from the advancing ice sheet. Because of these reasons and the absence of a pre-till weathering profile it seems more reasonable to consider these sediments as Illinoian rather than Yar- mouth in age. The early Illinoian till is best exposed in cliffs at Squibnocket Point and in the cliffs on the south shore of Nomans Land, 31/2 miles to the south. It also is found at the north end of Lamberts Cove and in pits in the interior of the western part of the island. It is an exceedingly compact well-graded till, eroding into “bad- land” forms. In places it is strikingly stratified. The color is slightly mauve to pinkish gray. More than 60 KAYE feet of till is present in the cliffs of Nomans Land and Squibnocket. This very compact stratified till was called the Montauk Till Member of the Manhasset Formation in Long Island by Fuller (1914), and the name Montauk was extended to Martha’s Vineyard and Block Island by Woodworth and Wigglesworth (1934). Unlike the Kansan and Nebraskan tills but in com— mon with all later tills, the pebbles, cobbles, and boul- ders of the early Illinoian till are predominantly of crystalline rock. Much of the deep pre-Pleistocene regolith had been removed from the New England crystalline terrane by the two earlier ice sheets, and by Illionian time a large expanse of unweathered rock lay exposed for the glacial ice to quarry. From rock types in the till the direction of movement of the early Illinoi- an ice is thought to have been toward the east-southeast. The thick till exposed at Squibnocket Point and Nomans Land probably represents parts of the terminal moraine, and the limits of the ice are inferred to have been a deep lobe, the edge of which trended southwest from Lam— berts Cove through Nomans Land, curving northward to the west to include Block Island, where this till is also well exposed (Kaye, 1960, fig. 51). The bathym- etry of open waters between the islands gives evidence of this lobate ice margin. Hydrographic charts and recent surveys show that a broad ridge marked here and there by boulder concentrations follows this aline- ment. The late Illinoian till can be seen in only a few small exposures in the eastern part of Wequobsque Cliff. The former widespread presence of this till, however, is deduced from the marked structural effects that the ice sheet had on all older deposits and from the wide- spread occurrence of a lag concentration of large boul- ders of a characteristic type that were carried by the ice and that may have once been part of a till sheet. Where exposed in Wequobsque Clifl’, the till is medium to dark gray and has an abundance of cobbles and boul- ders. Two rather distinctive rock types are found in the clasts: a coarsely porphyritic granite containing large pink to red microcline phenocrysts, and a dark- gray diorite. Boulders of these rocks, commonly of very large size, litter the surface of much of western Martha’s Vineyard. Their greatest concentration is in areas of pronounced structural imbrication, and they are particularly abundant in the hilly western section of the island. These hills are the remains of a great pushed, or imbricated, terminal moraine of the late Illi- noian ice. The intervening valleys are erosional, cut by streams in Sangamon time. The lobate outline of the late Illinoian terminal moraine is suggested by the change in strike of the thrust sheet produced by it. 0137 It is also shown by the topographic axis of the western part of the island. The southernmost point reached by this lobe was just north of Squibnocket. No deposits of Sangamon age have been recognized. Sangamon time was, however, a time of considerable erosion and profound weathering. Deep oxidation de- veloped during this interval is found on Sangamon ero- sion surfaces in all the cliffs. EARLY WISCONSIN DRIFT The earliest Wisconsin deposit is thick gray clay overlain by sand. The sequence very much resembles the clay and sand of the early Illinoian drift and prob— ably formed under similar conditions. The early VVis— consin clay and sand crop out in the high central and western part of Wequobsque Clifl' where they have been repeated by a series of thrust faults, and in the cliffs on the north side of the island where they were pushed up from Vineyard Sound against the north flank of the eroded Illinoian, moraine by early Wisconsin ice. In Wequobsque Cliff the lower 10 feet of the clay is varved, grading up into an unfossiliferous medium- gray massive clay. Pollen studies of this clay indi- cate a fairly mild climate at the outset of deposition, becoming colder as clay was deposited toward the top of this zone. The sediment probably represents a pro- glacial deposit formed by rock flour coming from the distant early Wisconsin ice. As the ice advanced, crus- tal subsidence caused by ice loading produced a relative rise of sea level. This changed the estuarine or laws- trine depositional environment (varved clay) to a ma— rine environment (massive clay). The overlying uni- form sand is in effect a deltaic continuation of the same deposition and marked the approach of the ice front. In western Wequobsque Cliff the sand grades up into gravelly outwash, which in turn is overlain by compact early Wisconsin till. The morainic deposits of the early Wisconsin ice range from a well-graded till containing some inter- stratified thin lenticular sand and gravel, on the west, to a stratified medium to coarse sand containing minor amounts of gravel in the eastern part of the island. In the central part of the island the two types of deposits tend to grade into each other. In the westernmost part of the island the cobbles and boulders in the till con- sist of an unusually wide variety of rock types and include many that are recognized as coming from dis— tant outcrops to the northwest, in Massachusetts and Rhode Island. The erratics in the eastern part of the island lack the diversity of type and the distinctive and sometimes traceable rocks that are found in the till to the west. This is very probably due to differ- ences in the direction of ice movement as suggested by the bilobate configuration of the ice front (fig. 1). 0138 The broad triangular outwash plain maln'ng up the central section of Martha’s Vineyard is a product of the early Wisconsin glaciation. The plain was fed mainly by the eastern lobe of the ice, although some sediment was contributed by the western lobe where small tongues of ice broke through the north ridge of the eroded Illinoian moraine (fig. 1) . MIDDLE WISCONSIN GLACIATION Martha’s Vineyard was probably free of ice during the middle Wisconsin. It was during part of this in- terval that the large moraine of the Elizabeth Islands, only 4 miles to the northwest, was formed. Some oxi- dation of earlier deposits and the development of podsol soil took place on Martha’s Vineyard during the in- terval between early Wisconsin glaciation and the max- imum advance of middle Wisconsin ice. Later, when the ice front stood at the Elizabeth Islands moraine, solifluction and other frost action occurred on Martha’s Vineyard. Large soil involutions, ice-wedge structures, and deeply cut and polished ventifacts are found on the early Wisconsin moraine, outwash plain, and the up- lands. Even the previously developed podsol soil was involuted. Solifluction carried surface material down- slope; characteristic deposits of iron-stained solifluc- tion debris can be seen rimming the lower flanks of hills in many sea cliffs. LATE WISCONSIN D'RIFT? The presence of late Wisconsin drift on Martha’s Vineyard, dating from about 13,000—14,000 years B.P., is inferred from several lines of evidence. A radio— carbon date of 15,300i800 years B.P. (W—1187, Wash- ington laboratory, U.S. Geological Survey) was ob- tained from leaves of tundra plants embedded in clay in Zacks Cliff, a low sea cliff about midway between Squibnocket Point and Gay Head. The clay overlies middle Wisconsin solifluction gravel and compact early Wisconsin till. The clay is overlain by foreset bedded sand. The outlines of the body of water in which this material was deposited are no longer evident and prob- ably were removed by erosion. At two places the clay and sand are overlain by till, or a till-like deposit (cob- bles, gravel, in a silty sand matrix). Inland from here, low roadcuts show similar till (?) interbedded with sand. . About 2 miles southeast of Zacks Cliff, about 10 feet of postglacial peat and organic sediment is ex- posed in the upper part of the sea cliff at Squibnocket (Kaye, 1962; Ogden, 1963). The lower 2 feet of this GEOMORPI-IOLOGY AND PLEISTOCENE GEOLOGY deposit contains fossils of tundra plants, and pollen studies indicate that a tundra flora existed when the earliest sediments were deposited here. A radiocarbon date of 12,700: 300 years B.P. (IV—710, Washington laboratory, U.S. Geological Survey, Rubin and Alex— ander, 1960) was obtained from a very thin sample at the base of the section resting on early Illinoian till. The two Martha’s Vineyard dates viewed in isolation do not in themselves provide a very strong basis for deducing the presence of an ice sheet of intermediate age. However, such an interpretation is given strong support by the fact that no basal material from post- glacial organic sediments in eastern Massachusetts and Rhode Island has yielded a date older than that at Squibnocket. The deposition of sediment in depres- sions seems to have begun sometime after 13,000 years B.P. In the Boston area the earliest date obtained is 12,170 years B.P. (Kaye and Barghoorn, 1964) ; on Block Island, 12,090 years B.P. (Kaye, 1960). All of these are thin samples collected in open exposures. In Boston a date of 14,000 years B.P. was obtained from shells in marine clay, but these clays have been precon- solidated to considerable depth, and it is believed that this is the result of overriding by an ice sheet, presum— ably the same glacial advance that reached Martha’s Vineyard. Another line of evidence for glaciation that was ap- proximately contemporaneous with the Port Huron ice advance of the Great Lakes area (Flint, 1963) is that the middle Wisconsin solifluction deposits of eastern Wequobsque Cliflf are faulted and the entire surface has been planed smooth, removing the upthrown scraps of the faults. The faulting may be the result of ice shove, as are so many of the structures exposed in the cliffs, and the smoothly truncated surface may have been caused by glacial erosion. Other examples of surface planation have been noted in the cliffs. An interesting one is in the western part of Wequobsque Cliff where an undrained depression has been entirely removed and only the well-developed gley zone that formed beneath it is preserved. REFERENCES Dall, W. H., 1894, Notes on the Miocene and Pliocene of Gay Head, Martha’s Vineyard, Massachusetts, and on the “land phosphate” of the Ashley River district, South Carolina: Am. Jour. Sci., 36 sen, v. 48, p. 296—301. Flint, R. F., 1947, Glacial geology and the Pleistocene Epoch: New York, John Wiley and Sons, Inc, 589 p. 1963, Status of the Pleistocene Wisconsin stage in cen- tral North America : Science, v. 139, p. 402—404. Fuller, M. L., 1914, The geology of Long Island, New York: U.S. Geol. Survey Prof. Paper 82, 231 p. KAYE 0139 Kaye, C. A., 1960, Surficial geology of the Kingston quadrangle, Raup, D. M., and Lawrence, D. R., 1963, Paleocology of Pleis- Rhode Island: US. Geol. Survey Bull. 1071—1, p. 341-396. tocene mollusks from Martha’s Vineyard, Massachusetts: 1962, Early postglacial beavers in southeastern New Jour. Paleontology, v. 37, p. 472—485. England: Science, v. 138, p. 906-907. Rubin, Meyer, and Alexander, 0., 1960, US Geological Survey Kaye, C. A., and Barghoorn, E. S., 1964, Late Quaternary sea- Radiocarbon dates V: Am. Jour. Sci. Radiocarbon Supple- level change and crustal rise in Boston, Massachusetts, ment, v. 2, p. 129—185. with notes on the autocompaction of peat: Geol. Soc. Amer- Woodworth, J. B., and Wigglesworth, Edward, 1934, Geog- ica Bull., v. 75, p. 63—80. . raphy and geology of the region including Cape God, the Ogden, J. G., 111, 1963, The Squibnocket cliff peat: radio- Elizabeth Islands, Nantucket, Martha’s Vineyard, No Mans carbon dates and pollen stratigraphy: Am. Jour. Sci., v. Land and Block Island: Harvard Univ. Museum Compara- 261, p. 344—353. tive Zoology Mem. 52, 322 p., 38 pl. % 732—760 0—64—10 GEOLOGICAL SURVEY RESEARCH 1964 ILLINOIAN AND EARLY WISCONSIN MORAINES OF MARTHA’S VINEYARD, MASSACHUSETTS By CLIFFORD A. KAYE, Boston, Mass. Abstract—Three well-defined morainic systems are present on Martha’s Vineyard. Remnants of an early Illinoian mo- raine occur at the southernmost point of the island and on No- mans Land, a nearby island. Hydrographic surveys show a deeply lobate submarine continuation to the west. The hills and valleys of western Martha’s Vineyard are the eroded re- mains of a very large moraine pushed up by late Illinoian ice. Early Wisconsin ice was partly stopped by this moraine in the western part of Martha’s Vineyard but overrode it in the east- ern part. The entire eastern half of the island consists of the early Wisconsin moraine and its outwash plain. Six drifts, very probably representing Nebraskan, Kansan, two Illinoian, and two Wisconsin Glaciations are found on Martha’s Vineyard. The two earliest drifts, the Nebraskan and Kansan,‘ and the late Wiscon- sin do not give evidence of the maximum extent of their respective ice sheets, and it is very likely that the ice terminated well south of the island. However, study of the two Illinoian and the early Wisconsin drifts, and their respective topographic characteristics, indicates that the drifts are terminal moraines. By some curi- ous coincidence, therefore, the terminal moraines of three successive continental glaciations appear to have crossed what is now western Martha’s Vineyard (fig. 1) . EARLY ILLINOIAN MORAINE The oldest moraine is probably early Illinoian in age. It is made up mainly of exceedingly compact mauve t0 pinkish-gray till that is commonly strikingly stratified. The topography is low and hummocky with many shal- low swampy depressions. The depressions, however, may be partly the result of erosion by late Wisconsin ice, which seems to have occupied the area but which left only a very thin and fragmentary drift cover. On Martha’s Vineyard the early Illinoian moraine as such is restricted to Squibnocket Point (fig. 1), the south— ernmost tip of the island. In the interior of the western part of Martha’s Vineyard, pinkish compact early Illi- noian till is found within the moraine of the succeeding late Illinoian ice sheet where it had been faulted up, along with earlier deposits, in an imbricated series of thrusts. The same type of thick till and similar terrane fea- tures as at Squibnocket are found on Nomans Land, a small island 31/2 miles south-southwest of Squibnocket. Hydrographic charts Show a low, interrupted subma- rine ridge of broadly lobate form connecting Nomans Land and Block Island, lying about 40 miles to the west, where similar very compact stratified till crops out with considerable thickness in the cliffs. The same type of very compact stratified till also occurs in eastern Long Island, where it was called the Montauk Till Member of the Manhasset Formation by Fuller (1914). The prob— able ice margin of the early Illinoian ice in the Martha’s Vineyard area is shown on figure 1. LATE ILLINOIAN MORAINE The high—standing, hilly western section of Martha’s Vineyard is the terminal moraine of late Illinoian ice. Northeast of Menemsha the moraine has been much eroded, both by stream action and by landsliding. Two rather deep northeast—trending valleys and a number of tributary valleys and gullies have been cut into it, producing a pleasant hill-and-dale topography with a relief of up to 175 feet. To the west the moraine is interrupted by a low sag occupied by two large ponds between Menemsha and Squibnocket Point; farther west the moraine occurs in the high land near Gay Head. The interior of the moraine is well exposed in Gay Head Cliff, the high sea clifl' at the western tip of Mar- tha’s Vineyard. Here the moraine is seen to consist of Late Cretaceous, Miocene, and pre-late Illinoian Pleistocene deposits, broken by a great number of faults and, at several places, distorted into complex folds. These structures continue below sea level, and there is no evidence of how thick the morainic complex is here. A detailed study of the structure exposed in US. GEOL. SURVEY PROF. PAPER 501—0, PAGES C140—0143 C140 KAYE Cl41 70° 30’ 41°30»— - a equobsque Cliff Squibnocket Point Nomans Land 41°15’— °—' :MARTHA’Sfa.” '.o . ..u .a'«. Middle Wisconsin moraine Early Wisconsin moraine Early Wisconsin outwash MASSACHUSETTS Area of - re p0 rt 0 V - «- EXPLANATION Late Illinoian moraine :] s Early Illinoran moriane .°.°. I . . . _2— a._°.. Ice margin Letter and number designate glaciation 5 10 MILES | | FIGURE 1.——Map of Martha’s Vineyard and surrounding islands, showing inferred ice margins and moraines of early Illinoian (I1), late Illinoian (12), early Wisconsin (W1), and middle Wisconsin (W2) ice sheets. the clifl’ shows that the moraine is mainly made up of imbricated thrust sheets pushed from the north. Dis- tortions of the thrust plates—presumably formed as they piled up in front of the ice~created secondary fault structures and large-scale rumpling. The impres- sion conveyed by Gay Head, that the structure is an imbrication of thrust plates moved from the north, is confirmed by detailed mapping and study of exposures in the hilly section of the moraine northeast of Menom- sha. Here the same imbrication of thrust plates, with individual plates attaining thicknesses of 100 feet or more, can be seen. Upper Cretaceous deposits are re- peatedly thrust over Pleistocene. The major thrust sheets in Gay Head Clifl' strike nearly east. East of Menemsha, the strike is northeast; the shift in orientation reflects the lobate form of the moraine. A study of aerial photographs shows that the eroded moraine northeast of Menemsha is marked by a series of low parallel ridges. From exposures in some of these ridges, one can see that they parallel the strike of the thrust sheets and are, in fact, small ero- sional cuestas produced by the outcrops of more resist- 0142 GEOMORPHOLOGY AND ant beds (mostly of early Illinoian till) within the thrust sheet-s. They therefore are useful in outlining the deformational structure of the moraine and they nicely indicate the form of the ice lobe that produced the deformation. Over most of this moraine late Illinoian till is absent. At many places, however, there is an impressive con- centration of boulders. Many of these are of a char- acteristic coarsely porphyritic granite with pink to red euhedral phenocrysts of microcline, 2 inches or more in length, that is not found in older drifts. These boul- ders are thought to have been transported by the late Illinoian ice and, in part, may represent a lag concen- tration left after whatever late Illinoian till that may have been deposited on or in the moraine had been re- moved by interglacial erosion. The late Illinoian ice was not unique in producing thrust or push structures. All the glaciations appear to have deformed to varying degrees the preexisting sediments. In Gay Head and other cliffs, there is a problem of distinguishing the deformation produced by the several ice sheets. It is clear, however, that the late Illinoian ice produced the most important defor— mation. The mechanism responsible for the imbricated mo- raine was probably the shearing off of broad flat frag- ments of the ground surface lying in front of the ice and the piling up of these plates as the ice moved for- ward. Plates were successively added at the base, rather than the top of the pack, and the moraine in effect was built from the base upwards. Something of the sort can be seen if one pushes his hand horizontally against the surface of a sandy beach on which there is a thin crust of salt-cemented sand. The essential condition is that the surface plates have greater rigidity and strength than the substrata along which they shear. Perhaps, therefore, the ground in front of the ice was frozen and the thrust plates may therefore largely rep- resent the permafrost zone existing at the time, and the thickness of each thrust sheet may measure the thickness of the carapace of frozen ground. The stripping and bulldozing effect was probably facilitated by the exist— ence of weak clayey beds beneath the permafrost. Moreover, the piling from the base upwards may have been aided by a thawed surface (the “active zone”) on the frozen ground. This would have reduced frictional resistance to the movement of the heavy morainic pile as it was pushed out over the ground surface. The late Illinoian moraine appears to have had a deep sag in the area now occupied by ponds between Menemsha and Squibnocket Point. Elements of the moraine are now lacking in this lowland, a fact that cannot be entirely explained by erosion by the early PLEISTOCENE GEOLOGY lVisconsin ice known to have passed through here. More likely the absence of the moraine is a result of a low point in the pre—late Illinoian surface. The lack of porphyry boulders and of characteristic deformational structures in the Squibnocket area sug- gests that the southern margin of the late Illinoian moraine probably passed immediately north of here. With this as a point of control, the lobate southern margin of the moraine has been drawn (fig. 1). EARLY WISCONSIN MORAINE The next ice sheet to have reached Martha’s Vine- yard was probably early Wisconsin in age. The mo- raine of this ice probably correlates with the Ronkon- koma moraine of Long Island (Fuller, 1914). Many of the physiographic features produced by this ice are still evident on Martha’s Vineyard and can be best appreciated on aerial photographs. In the western part of Martha’s Vineyard, the ice was stopped by the late Illinoian moraine. Northeast of Menemsha the ice lapped up against the north flank of the northernmost of the three erosional ridges, generally reaching no higher than the present 150-foot contour. Till de- posited by this ice rarely exceeds 25 feet in thickness, and the ice left little in the way of an actual moraine One effect of the glaciation was the rumpling and thrusting up of the early Wisconsin proglacial de- posits into ridges. These consisted of thick marine clay overlain by sand that had been deposited in Vine- yard Sound, in the Menemsha sag, off the south coast, and in fact, in all low-lying places. Besides the result- ing push ridges and thin till, another topographic ef- fect of the glaciation was the erosion of the late Illinoian moraine and the removal of many of its more delicate features. For example, the thrust ridges were destroyed, and today we can see many of these ridges truncated at the margin of the early Wisconsin moraine. The strip occupied by the early Wisconsin moraine along the northwest coast of the island is narrow, aver- aging about half a mile in width. However, where low cols or small transverse valleys had cut across the crest of the northern ridge of the late Illinoian moraine, the ice front was able to project south for short distances into the erosional valley beyond. The largest of these projecting tongues of ice was south of Lamberts Cove, where a bulbous lobe of ice reached about a mile south of the main front. West of the main late Illinoian moraine the ice pushed through the Menemsha sag and then spread east and west. The ice also flowed south through Vineyard Sound, around the highlands of Gay Head, joining the ice pushing through the Menemsha sag. The highest KAYE land near Gay Head rose above the ice as low nunataks. Today three patches of high ground, including the higher part of Gay Head Cliff and the land immediately behind it, give evidence of having been ice free. The early \Visconsin ice may have reached as far south as Nomans Land. Thin drift that may be early or late Wisconsin in age caps all but the highest ground of this small island. In the eastern part of Martha’s Vineyard the early Wisconsin ice was able to push south across the entire width of the late Illinoian moraine and to form a very broad lobe. The entire eastern half of Martha’s Vine- yard is the product of this lobe, as is most of Nantucket Island to the east. On Martha’s Vineyard the moraine of this lobe is a belt of low hummocky ground, about 2 miles wide, that follows the northeastern shore. From many good exposures in cliffs it is clear that much of the moraine is made up of horizontally stratified sand 6% 0143 with some interbedded gravel. This material is not noticeably different from the sand and gravel in the outwash plain that spreads from the foot of the moraine to the south shore of the island. The morainic sand may represent a superglacial, headward continuation of the outwash plain. However, the moraine stands higher than the outwash plain. This relationship is diflicult to explain in terms of the topographic inversion to be expected in superglacial deposits (Kaye, 1960, p. 358). The manner in which the early Wisconsin mo- raine in eastern Martha’s Vineyard was built is there— fore a question that merits further study. REFERENCES Fuller, M. L., 1914, The geology of Long Island, New York: US. Geol. Survey Prof. Paper 82, 231 p. Kaye, G. A., 1960, Surficial geology of the Kingston quadrangle, Rhode Island: U.S. Geol. Survey Bull. 1071—1, p. 341—396. GEOLOGICAL SURVEY RESEARCH 1964 GLACIAI. GEOLOGY OF THE MOUNTAIN IRON—VIRGINIA—EVELETH AREA, MESABI IRON RANGE, MINNESOTA By R. D. COTTER and J. E. ROGERS, St. Paul, Minn., Alexandria, Lo. Work done in cooperation with the Minnesota Department of Iron Range Resources and Rehabilitation Abstract—The surficial clayey till in' the vicinity of Mountain Iron, Virginia, and Eveleth is of post-Cary age. In the southern part of the area studied, this till is overlain by deposits of glacial Lake Upham, and throughout the area it is underlain successively by stratified drift and bouldery till, both of Cary age, and by remnants of older tills. Unconsolidated deposits related to 3, or possibly 4, Pleistocene glaciations have been recognized in the Mountain Iron—Virgina—Eveleth area in St. Louis County, Minn. The area described here is roughly square and is bordered on the north and northeast by the Laurentian divide; it extends about 9 miles both westward and southward from Virginia. The glacial deposits occupy a southwest-trending structural trough in rocks of Precambrian age. The Precambrian bedrock consists of granite, gray- wacke, greenstone, slate, schist, and gneiss, and an over- lying sequence of metamorphosed sedimentary rocks that consist, in ascending order, of the Pokegama Quartzite, the Biwabik Iron-Formation, and the Vir- ginia Slate. The Biwabik is exposed in a 2-mile-wide belt south of the older bedrock. South of this the entire _ area is underlain by the Virginia Slate. These rocks were deeply weathered before the first Pleistocene gla— cier passed over the area. GLACIAI. STRATIGRAPHY The surface deposits are shown on figure 1. Most of the area is mantled with reddish-brown clayey till, but to the south, silt and sand of glacial Lake Upham over- lie the till. A wave-cut beach at an altitude of 1,370 feet marks the contact between the till and the lake de- posits, except in the southeast where it is obscured by eolian deposits. In the report area, 7 types of till are diiferentiated on the basis of color, texture, or lithology; 3 types (1, 2, and 3 in the accompanying table) have not previously been described. Two bouldery types (3 and 4) prob- R.19W R18W R.17W. DIVIDE IM....,Mountain » I 1 Iron J ’ ‘ n 3“, veleth ‘ (”iv \fi [ EXPLANATION C7 Reddish»brown clayey till , Rainy lobe WW I Area of > «$0 / relay't e ’ a M 6‘ mi 9'» ex suv (905‘ MINNESOTA i FIGURE 1.—Surficia1 geology of the Mountain Iron—Virginia— Eveleth area, St. Louis County, Minn. Swamp deposits Glacial-lake deposits Eolian deposits ably represent a single interval of deposition, and 3 clayey types (6, 7, and 8) another interval. The stratigraphic relations of the several tills are shown on figure 2 and in the accompanying table. U.S. GEOL. SURVEY PROF. PAPER 501—0, PAGES C144-Cl46 0144 COTTER AND ROGERS Cl45 Stratigraphy of glacial deposits in the Mountain I ron—Vfrginia—Eveleth area, Minnesota [Numbers in parentheses keyed to text discussion] Known Known distribution within Mountain Iron— Age Type of deposit Distinguishing characteristics thgpékepgss Virginia-Eveleth area Very well sorted, fine-grained sand and silt; Surficial (fig. 1). Deposits are prob- (10) Eolian probably derived largely from glacial lake beds; 0—5 ably more extensive than shown. contains numerous wind-faceted pebbles (9) Glacial Finely laminated, well-sorted, fine- grained sand, 0-26 Surficial (fig. 1). lake silt, and clay. Surface very flat. (8) Reddish brown; contains a Surficial (fig. 1). In subsurface be- few pebblesofvolcanic rock 0—26 neath the lake deposits. Clayey, silty; and agate; also contains contains a lenses of unit 6. few pebbles of local (7) Brownish gray; contains a In subsurface; discontinuous bodies Post-Caryl Till origin. few pebbles of volcanic 0—61 within the areal extent of reddish- rock and agate; also con- brown clayey till. tains lenses of unit 6. (6) Greenish gray; contains peb- In subsurface; a few lenses are within bles of limestone and 0—28 the reddish-brown and brownish- shale; also occurs as lenses gray clayey till. in units 7 and 8. Clay, silt, sand, and gravel; bedded, sorted; rock 0—129 In subsurface; underlies reddish- (5) Stratified types are of local origin. brown clayey till, except within drift about 1 mile of its north and east limits. Gray to buff, bouldery, sandy; contains numerous In subsurface beneath lake deposits Cary (4) Till coarse fragments of local origin. 0—~95 and reddish-brown clayey till, except where removed by stream channeling. Orange, bouldery, sandy; contains coarse frag- In subsurface; scattered lenses Within (3) Till ments of local granite, slate, and iron-formation. 0—25 a few miles of the Laurentian Color is from hematitic silt. divide. Chocolate brown, silty and sandy; contains frag- In subsurface; scattered lenses within (2) Till and ments of volcanic rock, weathered igneous and 0—32 afew miles of the Laurentian divide. outwash metamorphic rock, calcareous concretions, lime- Pre—Cary stone, and banded agate. Black; consists largely of decomposed slate and a In subsurface; scattered lenses in (1) Till few pebbles of fresh slate. 0—8 central and southern part of the area, overlying the Virginia Slate. 1 Age in doubt; see Wright (1956, p. 19—23) and Zumberge and Wright (1956, p. 65—80). The oldest Pleistocene unit identified is a black till ( 1) as much as 8 feet thick, resting on the Virginia Slate. Samples, which were obtained only from test holes, contained pebbles of fresh slate in a matrix of decomposed slate. In open-pit iron mines the oldest exposed glacial de- posit consists of remnants of a. chocolate-brown silty and sandy till and associated outwash (2). This til] contains fragments of volcanic rock, calcareous concre- tions, limestone, banded agate, and weathered local igneous and metamorphic rock. Locally, an orange, bouldery, sandy till (3) overlies the chocolate-brown till in the iron mines. The coarse fraction is composed of fragments derived from local bedrock. More than 50 percent of the fragments are granite, and the remainder are slate, metamorphic rock, and Biwabik Iron-Formation. The orange color is due to included fragments of red hematitic silt. Stratigraphically above the orange till, but resting on the Virginia Slate in much of the area, is a gray to buff, bouldery, sandy till (4). The lithology of this till is similar to the orange till. Stratified drift (5) gen- erally overlies this gray bouldery till. It consists of clay, silt, sand, and gravel that is lithologically similar to these size fractions in the underlying gray bouldery till. The pitted topography of the central and west- central part of the area reflects the highly irregular upper surface of the stratified drift. A series of three clayey, silty tills overlie the bouldery fills and associated stratified drift. The lowest of these three is a. greenish-gray clayey till (6) which occurs also within and between overlying reddish-brown and EXPLANATION Post-Cary Pre-Cary r—-——A————fi E Reddish-brown Brownish-gray Greenlsh-gray Chocolate-brown Black clayey till (8) clayey till (7) clayey till (6) silty till (2) till (1) Precambrian D Bedrock Cary ii ('7 I? :l l 3 1 Gray to buff Orange bouldery bouldery till (4) till (3) li-i~:-J Stratified drift (5) FIGURE 2.——Diagrammatic cross section of glacial till and strati- fied drift in the Mountain Iron—Virginia—Eveleth area, St. Louis County, Minn. brownish-gray clayey tills. In addition to local rock types, the greenish-gray till contains numerous lime- stone and shale pebbles. Locally resting on the greenish-gray till is a brownish- gray, clayey, silty till (7) containing few pebbles, most of which are of local rock, but a few of which are of volcanic rock and banded agate. It is discontinuous throughout the area, but commonly forms the lower part of thick sections of the clayey tills. The uppermost till (8), exposed at the surface in the north and central parts of the area, is reddish brown, clayey, and silty. Contained rock types are the same as in the underlying brownish-gray till. The color break between these two tills is sharply defined, but other- wise they are the same. GLACIAL HISTORY The observed sequence of tills permits some additions to the current interpretation of the glacial history of the area. The earliest Pleistocene glaciers to cross the area re- worked the weathered slate surface and deposited the black till (unit 1 in table). A later glaciation deposited the chocolate-brown till (2). Volcanic rock fragments and agate in the chocolate-brown till indicate that the ice moved into the area from the Lake Superior Basin. According to Wright (1956, p. 10, 11), the Rainy lobe advanced through the area from the northeast during the Cary Substage of Wisconsin time. It 6% GEOMORPHOLOGY AND PLEISTOCENE GEOLOGY crossed the Laurentian divide and deposited the gray boulder till (4) . The authors believe that the orange bouldery till (3) is a part of this same till sheet, the orange color being caused by inclusion of fragments of altered Biwabik Iron-Formation. Because the gray bouldery till (4) rests on bedrock in most of the area, the glacier must have incorporated most of the older glacial deposits. After the ice front of the Rainy Lobe wasted to a po- sition north of the Laurentian divide, melt water poured through notches in the divide and cut channels into or through the gray bouldery till. Stratified drift (5) was deposited around residual ice blocks, which later melted, resulting in the present pitted topography. Wright (1956, p. ‘20) suggested that the Superior lobe of Post-Cary ‘ age advanced southwestward out of the Lake Superior Basin, encountered the St. Louis sublobe of the Des Moines Lobe advancing southeastward, and split into two segments. One segment presumably was diverted northward to the Mesabi Range, where it de- posited a till that is referred to in the present article as reddish-brown clayey till (8). The authors’ current view is that the reddish—brown (8) and brownish-gray (7) clayey tills are different facies of one unit deposited by the Superior lobe and that oxidation accounts for the reddish-brown color. The color difference might alternatively be explained if the brownish-gray till (7 ) represents an advanced stage of Post-Cary ice that is less red because of the incor- poration of gray glacial lake deposits. However, the lack of any significant deposition separating the two units and the presence of brownish-gray till (7) only Where the till fills depressions in the surface of the stratified drift supports the former hypothesis. The greenish-gray clayey till. (6) probably was de- rived from the St. Louis sublobe. Abundant limestone and shale pebbles indicate a source area to the north- west. Be'cause this till is not continuous in the sub- surface, it is postulated that the St. Louis sublobe did not actually advance into the Mountain Iron—Virginia— Eveleth area, and that the lenses of greenish-gray till represent materials carried into the area by the Superior lobe from the confluence of Superior and St. Louis ice. REFERENCES Wright, H. E., J r., 1956, Sequence of glaciation in eastern Minne— sota, in Geological Society America Guidebook, 1956 Annual Meeting, Minneapolis, Minn.: p. 1—24. Zumberge, J. H., and Wright, H. 'E., Jr., 1956, The Cary- Mankato-Valders problem, in Geological Society America Guidebook, 1956 Annual Meeting, Minneapolis, Minn.: p. 65—81. 1 Age in doubt ; see Wright (1956, p. 19—23) and Zumberge and Wright (1956, p. 65—80). GEOLOGICAL SURVEY RESEARCH 1964 RECENT RETREAT OF THE TETON GLACIER, GRAND TETON NATIONAL PARK, WYOMING By JOHN C. REED, JR., Denver, Colo. Abstract—Comparison of a plane-table map of the Teton Glacier made in 1963 with a map prepared from aerial photo- graphs taken in 1954, and with older maps and photographs, indicates that the rate of retreat of the terminus has decreased, and that the thickness of the upper part of the glacier has im creased since 1954. These observations suggest that the ter- minus of the glacier may begin to advance within the next few years. The Teton Glacier i, one of about a dozen small alpine glaciers cradled in shady east- or north-facing cirques among the high peaks of the Teton Range in Grand Teton National Park, Wyo. The glacier, which occupies a spectacular east-facing cirque between the east ridge of the Grand Teton and Mount Owen, has been well described by Fryxell (1933a, 1933b, 1935). The glacier is apparently nourished in large part by avalanches from the encircling cliffs, some of which are more than 3,000 feet high. Because of its scenic setting and relatively easy access, the Teton Glacier is one of the most frequently visited and photographed glaciers in Grand Teton National Park, but it has received little systematic study. In addition to the studies by Fryxell (1933a, 1933b, 1935), brief surveys of the glacier were made by Carl E. J ep- son in 1949 and 1950, and by M. T. Millett in 1960. Re- ports of these studies were not published, but are avail- able in the Grand Teton National Park library. In August 1963, the writer made a plane-table survey of the lower part of the Teton Glacier, with the assist- ance of R. Alan Mebane, Assistant Park Naturalist, David D. Steller, and A. C. Chidester. The map has been placed on open file by the U.S. Geological Survey, and stable base copies at the original scale (1 inch=200 feet) are available for examination at park headquarters and at the US. Geological Survey offices in Denver, Colo. In addition, a contour map of the glacier has been prepared with a. Kelsh plotter, from 1954 high-altitude aerial photographs. The two maps are combined on figure 1. The position of the terminus in 1950 is taken from J epson’s map; the 1929 terminus is sketched from a photograph (Fryxell, 1935, fig. 5) and Fryxell’s description. Photographs taken by W. 0. Owen in 1898 indicate that at that time the ice had already retreated 10 to 20 feet from the crest of the terminal moraine, but the photographs were taken from a considerable distance at a time when the glacier and moraine were snow covered, so that the position of the terminus could not be sketched accurately on the map. Millett’s report does not include a map showing the terminus in 1960, but his photographs indicate that it was at virtually the same position as in 1963. Profiles (fig. 1) sketched from the map show thinning and re- treat of the terminus. The general character and condition of the glacier at the time of the 1963 survey are shown in the photo- graphs (fig. 2, 3, and 4), negatives of which are on file in the field-records file of the US. Geological Survey, Denver, Colo. The location and marking of the control points shown on figure 1 are given in table 1. In addition, iron pipes were driven into the ice along a line extending across the glacier through control points E and F for use in any future studies of movement and ablation. The location and altitude of points on this line are given in table 2. The map and profiles (fig. 1) show that the terminus of the glacier has retreated markedly since 1929. The approximate volume of ice lost since 1929 from the gla— cier below the line of profile Y —Y ’ of figure 1 has been calculated from the 1954 and 1963 contours and from approximate contours reconstructed on the basis of the positions of the ice margin in 1950 and 1929. These data (fig. 5) show that the rate of loss of ice between 1954 and 1963 was much less than between 1929 and 1954. Profile X—X’ (fig. 1) shows that the upper part of the glacier was thicker in 1963 than in 1954. The decreasing rate of loss of ice from the lower part of the glacier and the thickening of the upper part may result in an advance of the terminus within the next few years. U.S. GEOL. SURVEY PROF. PAPER 501—0. PAGES Cl47-0151 Cl47 GLACIOLOGY 0148 H EDGE hum—n. Om n_<>mm._.z_ ”.5th00 _ _ _ _ _ _ _ Eu... ooofi 00m 0 vmmfi .ZOTZZZOMD Z. m E 50 z E '2 m 40 O n: Lu 0. 3O 20 — ‘ 10 — _ I l | | I I III I I l l -« N m 4 and Nye, 1933) . g— — {V 5‘ _ N v— ; , Western limit of artesian head -- 51 £91833} ELSE—[,LN-TL above water table in January gl CHAV E5 (‘OL’NTY 1957 (Mower, 1960) I i ' l r “l 1' 'f \n 113,” , l \. "I \1?30 H Cloudcroft I 1 - —‘:. ' . o \\ \' 5'6 “fiwlgwl! 56 \ YR; . / | , 1" \~» ._/' I \_ , ~ ;. w“ R120 5 \ / :7 1' I / “f \S‘ >4 N ,._, '-_‘ 70 . E 1 pews“ 18 NEW MEXICO v u _.__. ‘47 ‘ “ l 336 Area of 6‘ .: Lake 4/ v . 287 t ’0 . m Mfiml . = 19 '°°°' 47% I E % / 1 g 235 T- l v 120 20 E L . S. i __.1_._1.q-_._..__ m- . _ R. 12 E 13 14 15 16 17 18 19 20 21 23 24 2: 26 R, 27 E- O 5 10 15 20 MILES Buttlar, Haro von and Libby, W. F., 1955, Natural distribution of cosmic-ray produced tritium II: Jour. Inorganic Nu~ clear Chemistry, v. 1, no. 1, p. 75—91. Fiedler, A. G., and Nye, S. S., 1933, Geology and ground-water resources of the Roswell artesian basin, New Mexico: FIGURE 1.-—Map showing sampling sites and tritium content of water samples. REFERENCES U.S. Geol. Survey Water-Supply Paper 639, 372 p., 46 pls. Kaufman, Sheldon, and Libby, W. F., 1954, The natural distri- bution of tritium: Phys. Rev., v. 93, no. 6, p. 1337—1344. Mower, R. W., 1960, Pumpage in the Roswell basin, Chaves and Eddy Counties, New Mexico: U.S. Geol. Survey open-file report, 88 p., 21 figs. 6% GEOLOGICAL SURVEY RESEARCH I964 RELATION OF SURFACE-WATER HYDROLOGY TO THE PRINCIPAL ARTESIAN AQUIFER IN FLORIDA AND SOUTHEASTERN GEORGIA By V. T. STRINGFIELD, Washington, DC. Abstract—The main source of some of the largest limestone springs in the world and of some streams in Florida and Georgia is discharge from the principal artesian limestone aquifer where it is at or near the surface on two major geologic structures in Florida and in the belt of outcrops in Georgia. During flood stage, water from some of the larger streams may enter the aquifer, but recharge is chiefly in interstream areas. The principal artesian aquifer in Florida and south- eastern Georgia is one of the most extensive and productive artesian systems in the United States. The aquifer underlies all the drainage basins in Florida, southeastern Georgia, and adjacent parts of Alabama and South Carolina. In some parts of the region, the surface streams are connected hydrologically with the aquifer, but in other areas they are completely uncon- nected. In recharge areas, the water level in the principal aquifer may represent the water table, but in other areas, there is a separate water-table aquifer wherein the water table may be above or below the piezometric surface of the artesian water. The purpose of this article is to outline briefly some of the relations of the water in the limestone to the surface-water hydrology, including the coincidence and lack of coincidence between surface drainage and ground-water flow. The principal artesian aquifer consists chiefly of limestone of Tertiary age as much as 1,000 feet thick. In Florida, it is known as the Floridan aquifer and is the source of some of the largest limestone springs known in the world (Ferguson and others, 1947). It yields water to thousands of wells and is the source of most large industrial, irrigation, and municipal supplies. The aquifer includes as many as seven geo- logic formations, ranging in age from middle Eocene to middle Miocene. In Florida the basal unit of the aquifer is the Lake City Limestone of middle Eocene age. In Georgia also, limestone of middle Eocene age is the basal unit. Limestone in the lower part of the Hawthorn Formation of Miocene age forms the top of the aquifer in a large part of the area. The principal aquifer is at or near the land surface in a belt extending northeast from western Florida and southeastern Alabama across Georgia into South Carolina (fig. 1). In general, it dips toward the Atlantic and Gulf coasts except where the dip is inter- rupted by geologic structures, such as the Ocala uplift in north-central Florida, and the Chattahoochee anti- cline in west Florida and southwest Georgia. The aquifer is as much as 150 feet above sea level on the Ocala uplift and 175 feet on the Chattahoochee anti- cline. It dips in all directions from the Ocala uplift. Its depth below sea level along the Atlantic coast is about 200 to 250 feet at Savannah and 500 feet in northeastern Florida and southeastern Georgia. It is only about 100 feet below sea level along much of the Atlantic coast in northern Florida. In south Florida, the principal aquifer is as much as 1,000 feet below sea level. The aquifer is at or near the surface along the west coast of Florida from Tampa Bay north to the panhandle, and in the western part of the panhandle it dips to more than 1,000 feet below sea level. Precipitation can infiltrate to the aquifer where the aquifer is exposed at the land surface or covered only with permeable materials. In addition to these re- charge areas, water enters the aquifer where sinkholes extend from the ground surface through relatively im- pervious beds of the Hawthorn Formation to the under- lying principal aquifer. Lakes with no surface outlet in the upland regions of Florida and in the Valdosta area of southern Georgia occupy many of these sinks (fig. 1). Some of the sinks are more than 200 feet deep, and a few of these are free from sediment and are occu- U.S. GEOL. SURVEY PROF. PAPER 501-C. PAGES 0164-0169 0164 STRINGFIELD 87" 1 32° — \ \ 0‘ ‘0 g % 31° '7‘— \ \ (9 \ % / \ \/ ‘a 30° — 00 29° — EXPLANATION Recharge through sinkholes 28° — and lakes breaching relatively impermeable beds Recharge through soils and 27° _ sinkholes where aquifer is at or near land surface — —200 Structure contour of top of aquifer 26° —— Contour interval 200feel; datum is mean sea level 25° ~ 1 l l l we I ‘S W I , f ' e A 200 : § — E z 100’ 5 Piezometric as; surfaceL SEA — '_ — — — \ LEVEL vTop of aquifer —100’ B 100’— SEA LEVEL —lOO 190 1?0 MILES FIGURE 1.—-Map showing geologic structure of top of principal artesian aquifer in Florida and southeastern Georgia, and location of recharge areas. (1955) ; Georgia portion after Warren (1944). Florida portion after Vernon 0165 GROUND WATER C166 86° 84° 82° 80" I ‘\ | , SOUTH CAROLINA 099/ g’ g A L A B A M A “ r\ o _ 32 a _ g? Savannah 26" chain “VJ WWWK [NDEX MAP OF AREAS REFERRED TO IN TEXT AND TABLE EXPLANATION I 00 Piezometric contour Contour interval 20feet; datum is mean sea level Major spring with flow of 100 cfs or more a. Large spring with average flow less than 100 cfs 50 A A Withlacoocéee *9 \ J ZOOMILES l 40 BIG CYPRESS S WA MP Miami \:. 40 20 ‘ ‘ / 00 / as of 1960. FIGURE 2.—Configuration of the piezometric surface of the principal artesian aquifer in Florida and southeastern Georgia In part after Healy (1962), Stewart and Counts (1958), and Stewart and Croft (1960). STRINGFIELD pied by lakes and springs (Ferguson and others, 1947). Many of these sinkholes are now almost completely filled with permeable sand through which water moves downward to the aquifer. The altitude of the land surface and the sinkholes compared to the water level or artesian head in the aquifer determines whether the sink is a place of re- charge or discharge. Recharge occurs where the water level in the sink, or of the lake which occupies the sink, is higher than the water level or artesian head in the aquifer. Where the head in the aquifer is higher than the land surface at the sink, an artesian spring flows from the sink. This is the explanation of nearly all the large springs of Florida and Georgia. Water enters the aquifer in recharge areas and moves down the hydraulic gradient to points of discharge at lower elevations. Natural discharge of the principal aquifers occurs through springs and at places where the aquifer is exposed in surface streams and in the ocean, and by upward leakage into the overlying formations. The location of the major streams and springs is shown in figure 2. The average flow of each of 17 of the largest springs is more than 100 cubic feet per second. Dis- charge occurs to the ocean where the artesian head at the submarine outcrop is greater than the pressure of sea water. There are many submarine springs in the Gulf of Mexico west of areas 8 and 9 (fig. 2), and a large spring is known to discharge in the Atlantic east of area 7. Some recharge may occur through relatively im- Cl67 pervious beds of the Hawthorn Formation- where the head in the artesian aquifer is less than that of the Haw- thorn. However, such recharge is not revealed on maps of the pressure surface of the artesian water. RELATION OF SURFACE DRAINAGE TO RECHARGE AND DISCHARGE A map (fig. 2) representing the piezometric surface of the water in the artesianaquifer shows the height, in feet, to which water would rise in tightly cased water wells penetrating the aquifer as of 1960. Except in a few areas of large withdrawal of water, the major fea- tures of this map are virtually the same as those shown on earlier maps and described by Stringfield, (1936, 1950) and by )Varren (1944), indicating that there is no detectable net change in the artesian head in areas unaf- fected by heavy Withdrawal by pumping or natural flow from wells. Earliest available records indicate that in coastal Georgia, as of 1885, movement of water in the principal aquifer was northeast toward a submarine dis- charge area northeast of Savannah (Stringfield and others, 1941). These maps of the piezometric surface indicate the general areas of recharge and discharge and the directions of lateral movement of the water. Ground water moves down the hydraulic gradientat right angles to the contours. In general, recharge is in the relatively high areas of the piezometric surface, and discharge is in the low areas; in some areas, both dis- charge and recharge occur. Some of these features are given in the accompanying table. Relations of piezometric surface to surface hydrology Area 1 Recharge Discharge Surface drainage Georgia—outcrop of aqui- fer in belt extending from southeastern Ala- bama, northeastward across Georgiainto South Carolina. Piezometric surface ranges from 250 feet to about 100 feet above sea level. Recharge occurs in interstream areas. Discharge to streams where piezometric surface is higher than stream level, as on the Flint, Ocmulgee, and Savan- nah Rivers. Rivers such as the Savannah, Ogeeche, and Ocmulgee cross the outcrop belt of the aquifer. The Flint River cuts deep into the aquifer in southwestern Georgia (Wait, 1963). Withlacoochee Valley and Valdosta area in south- ern Georgia. Piezometric surface is as much as 100 feet above sea level in Vald0sta area where recharge occurs through sinkholes and drainage wells. Discharge along the Withla- coochee River. Surface drainage is into lakes, sinkholes, and drainage wells in the lake region in Valdosta area. Southeastern Georgia _____ Little or no recharge because the aquifer is overlain by as much as 500 feet of the Hawthorn Formation. Recharge through sinkholes may occur in the Okefenokee Swamp. Artesian water in the limestone moves east and northeast. Original piezometric surface indicated submarine dis- charge northeast of Savannah. Surface streams not related to the aquifer; drainage is slug- gish. West Florida, area 1 ______ Aquifer is recharged where it is near the surface in northern part of the area and adjacent parts of Alabama. Some discharge to streams in the eastern part. of the area. Water in the aquifer moves generally south. One‘ spring has an average discharge of more than 100 cfs. Aquifer is too deep to be related to surface streams in the western part of the area. C168 GROUND WATER Relations of piezometric surface to surface hydrology—Continued Area 1 Recharge Discharge Surface drainage Area 2 __________________ Recharge through lakes and A broad valley in the piezomet- Much of the drainage is under— sinkholes. The aquifer is ric surface is caused by under- ground in limestone. Some of near the land surface in the ground flow to the Gulf of it reappears at the surface, southern part of the area. Mexico and to springs. Wa- forming Wakulla Spring, Wa- kulla Spring and two other kulla River, and other streams. springs each have an average discharge of more than 100 cfs. Area 3 __________________ Recharge occurs in the inter- Discharge occurs to the Suwan- Poor surface drainage in inter- stream area. nee and Aucilla Rivers. stream areas. Area4 ___________________ Recharge occurs in interstream Large discharge occurs chiefly as The Suwannee and Santa Fe areas. During flood stages springs and directly into the Rivers cut into the aquifer the Suwannee and Santa Fe Suwannee and Santa Fe (Clark and others, 1962). Rivers lose water to the Rivers and forms large valleys aquifer. in the piezometric surface. Five springs have average dis- charge of more than 100 cfs. 'Area 5 __________________ Recharge through sinkholes in Water moves laterally in all In upland lake region, drainage the southwestern part causes directions from recharge area. is into sinkholes and lakes. the piezometric surface to Part moves into the Santa Fe Aquifer is too deep to affect the stand as much as 80 feet River drainage basin. St. Johns River and other above sea level. A recent streams. description oépart of this area is given by lark and others (1963). Area 6 __________________ Aquifer at or near the surface. Although there is large local re— Water from Silver Springs flows Large recharge from precipi- charge and artesian water to the east and that from Rain- tation. moves into area from north bow Springs flows to the west. and south, discharge through In most of area, there are no Silver Springs and Rainbow surface streams. Springs, averaging 1,507 cfs, causes a saddle in the piezo- metric surface. Area 7 __________________ Recharge is through sinkholes Piezometric surface is onlyafew The St. Johns River, a tidal in the upland lake regions east feet above sea level in part of stream, flows northward of the St. Johns River. the St. Johns valley where through area in which its there is large discharge of artesian water to the river. There is submarine discharge in the Atlantic Ocean. channel is cut into deposits overlying the aquifer. In that part of the valley, each of four springs has an average dis- charge of more than 100 cfs. Areas 8, 9, and 10 ________ Aquifer is at or near the surface in most of the area and is re- charged by precipitation. In the upland lake region, where the piezometric surface is as much as 80 feet above sea level, recharge is through sinkholes. Large discharge through springs, many of which are in the Gulf of Mexico. Artesian water constitutes a large part of the flow of the Withlacoo- chee and Hillsborough Rivers and other streams. Largest streams are the With- lacoochee and Hillsborough Rivers. Drainage is poor in the upper courses of the streams where the piezometric surface is near the land surface. Two of the springs each have an average discharge of more than 100 cfs. Area 11 _________________ Recharge through sinkholes and lakes in the lake region in the central part of the area causes the piezometric surface to be more than 100 feet above sea level. Lateral movement of water is in all directions from recharge areas in the upland lake region. In the lake region surface drainage is into lakes and sinkholes. Sur- face streams are not related to the aquifer except in the northern, northeastern, and northwestern parts, where some artesian water discharges directly into streams. Area 12 __________________ No detectable recharge to the aquifer. Piezometric surface is above the land surface. No detectable discharge to sur- face streams. Discharge off- shore may occur where the ar- tesian pressure at submarine outcrop exceeds ocean pres- sure. Surface drainage not related to aquifer. 1 In Florida, areas are numbered as shown on index map, figure 2. STRINGFIELD SUMMARY AND CONCLUSIONS' The flow of some of the largest limestone springs known in the world and some of the principal streams of Florida is discharge from the artesian aquifer. Each of 17 of the largest of these springs has an average flow of more than 100 cfs. The surface hydrologyis closely related to the recharge and discharge of the aquifer un- der the following conditions, as indicated by patterns on figure 1: (1) Where the streams cross the belts of outcrop of the aquifer, water from nearby recharge areas discharges into the streams. (2) Where the Haw— thorn Formation has been removed by solution and ero- sion in the Flint River valley in Georgia and in a large region in north-central and north Florida (bordering the Gulf of Mexico from west Florida to Tampa Bay) the major streams occupy channels cut into the aquifer, and water discharges from the aquifer into the stream. In east—central Florida, a large area of artesian dis- charge occurs where the St. Johns River cuts through deposits overlying the aquifer. The large limestone springs in Florida and Georgia occur in the areas where the Hawthorn has been removed and the principal artesian aquifer is at or near the surface. (3) Where sinkholes in the lake region extend from the land sur- face through the Hawthorn to the aquifer, local re- charge occurs. In some of these areas there are no sur- face streams, indicating that all drainage is subsurface. Surface-water hydrology is unrelated to the aquifer where the aquifer is far below the land surface, as in southeastern Georgia and northeastern, southern, and western Florida. In these areas, representing more than half of the extent of the aquifer, local recharge is not sufficient to be recognized on the piezometric surface of the principal aquifer. In the discharge areas, the chemical quality of the artesian water affects the quality of the surface water. In the recharge areas, the surface water affects the qual- ity and temperature of the artesian water. Discharge of water from the aquifer to streams and springs has increased the permeability of the aquifer and caused more rapid circulation. This circulation has acceler- ated the removal of salt water that entered the aquifer in some areas when the sea stood higher in Pleistocene time than at the present. The surface drainage has a dendritric pattern charac- terized by many tributaries where the streams are inde- 0169 pendent of the aquifer, except on coastal Pleistocene terraces where the drainage pattern is influenced by the topography left by the sea. In areas where recharge or discharge of the aquifer is sufficient to cause anoma- lies on the piezometric surface, as in the Suwannee and Santa Fe basins in Florida, the streams have few tributaries. , In studies of the water resources and planning for their development in this region, the relation between the artesian system and the surface hydrology should be recognized and understood to determine whether the surface and subsurface hydrology should be considered separately or be treated as a unit. REFERENCES Clark, W. E., Musgrove, R. H., Menke, C. G., and Cagle, J. W., J r., 1962, Interim report on the water resources of Alachua, Bradford, Clay, and Union Counties, Florida: Florida Geol. Survey Inf. Circ. 36. 1963, Hydrology of Brooklyn Lake near Keystone Heights, Florida: Florida Geol. Survey Rept. Inv. 33. Ferguson, G. E., Lingram, C. W., Love, S. K., and. Vernon, R. 0., 1947, Springs of Florida: Florida Geol. Survey Bull. 31. Healy, H. G., 1962, Piezometric surface and areas of artesian flow of the Floridan aquifer in Florida, July 6-17, 1961: Florida Geol. Survey map sen, No. 4. Stewart, J. W., and Counts, H. B., 1958, Decline of artesian pressures in the coastal plain of Georgia, northeastern Florida and southeastern South Carolina: Georgia Geol. Survey Mineral Newsletter, v. 11, No. 1. Stewart, J. W., and Croft, M. A., 1960, Ground-water with- drawals and decline of artesian pressures in the coastal counties of Georgia: Georgia Geol. Survey Mineral News- letter, v. 13, No. 2. Stringfield, V. '1‘., 1936, Artesian water in the Florida peninsula : U.S. Geol. Survey Water-Supply Paper 773—0, p. 115—195. 1950, Ground-water geology in the southeastern States, in Proceedings of symposium on mineral resources of the southeastern States: Knoxville, Tenn., Univ. Tennessee Press. Stringfield, V. '1‘., Warren, M. A., and Cooper, H. H., Jr., 1941, Artesian water in the coastal area of Georgia and north- eastern Florida: Econ. Geology, v. 37, No. 7, p. 699—711. Vernon, R. 0., 1955, Safe and adequate and you drink it: Florida Eng. and Indus. Exept. Sta. Bull. 72. Wait, R. L., 1963, Geology and ground-water resources of Daugherty County, Georgia: US. Geol. Survey Water- Supply Paper 1539—P. Warren, M. A., 1944, Artesian water in southeastern Georgia, with special reference to the coastal area: Georgia Geol. Survey Bull. 49. GEOLOGICAL SURVEY RESEARCH 1964 CONTAMINATION OF GROUND WATER BY DETERGENTS IN A SUBURBAN ENVIRONMENT—SOUTH FARMINGDALE AREA, LONG ISLAND, NEW YORK By N. M. PERLMUTTER; MAXIM LIEBER,1 and H. L. FRAUENTHAL,2 MineoIa, N.Y.; HempsieacI, N.Y. Work done in cooperation with the Nassau County Department of Health and the Nassau County Department of Public Works Abstract—Water in the upper 20 feet of the water-table aqui- fer, composed of glacial-outwash deposits, is contaminated by ABS (alkylbenzenesulfonate) in concentrations generally be tween 1 and 5 ppm but locally as high as 32 ppm. Most of the water in the remainder of the aquifer contains less than 1 ppm and does not foam. Efliuent from hundreds of randomly dis- tributed cesspools is the source of contamination. Large-scale suburban development of Long Island since World War II has brought not only the pleasures of suburban living to many former city dwellers but also, in some areas, the problem of foaming and bad- tasting ground water. Foaming is caused by ABS, a surface-active organic compound which constitutes about 30 to 40 percent of the ingredients in common household detergents. The ABS, along with associated contaminants such as chloride, phosphate, nitrate, ni- trite, bacteria, and possibly viruses in domestic wastes, has entered the shallow water-table aquifer by seepage of effluent from thousands of cesspools. Substitution of detergents for soap has increased markedly during the past 15 years, and in places Where detergent in water supplies has resulted in deterioration of quality, users have become more acutely aware of the recircula- tion of wastes in the ground water. ABS in water gen- erally is regarded as more of an appearance or taste problem than a menace to health, as ABS by itself is not considered to be toxic in concentrations commonly found in ground water. Nevertheless, the presence of 1Assistant Director, in charge of Sanitation Laboratories, Division of Laboratories and Research, Nassau County Department of Health. 2Hydraulic Engineer, Division of Sanitation and Water Supply, Nas- sau County Department of Public Works. ABS may indicate the occurrence, possibly in harmful concentrations, of other contaminants from cesspool wastes. Hence, the US. Public Health Service (1962) recommends that the concentration of ABS in water to be used for drinking or cooking should not exceed 0.5 parts per million. Contamination by detergents is particularly Wide- spread in unsewered parts of southern Nassau and Suffolk Counties. What is the extent of the contam— ination? HOW deep has it penetrated and in what concentrations? Are public supply wells in danger of contamination? These and related questions have been the subject of much speculation. Consequently, during the past few years investigations have been made individually and cooperatively in parts of Nassau and Sufl'olk Counties by State and County agencies and the US. Geological Survey to find answers to some of these questions (New York State, 1963, p. 69— 90). Of the current investigations, some deal with contamination in the immediate vicinity of a single cesspool or well field, whereas others are of wider areal scope. This article is a summary of the results of an areal investigation in east-central Nassau County (figs. 1 and 2). Appreciation is expressed to Commissioner Eugene F. Gibbons of the Nassau County Department of Public Works and to Dr. Joseph H. Kinnaman, Commissioner of the Nassau County Department of Health, for their enthusiastic support of the investigation. We also thank all the Nassau County and US. Geological Sur- vey personnel who assisted in the field and laboratory work. U.S. GEOL. SURVEY PROF. PAPER 501-0, PAGES C170—Cl75 Cl70 PERLMUTTER, LIEBER, AND FRAUENTHAL NASSAU Area of co 0" report 0 25 MlLES l_l_l_|_|_l | 1 FIGURE 1.—Map of Long Island, N.Y., showing location of the South Farmingdale area. 0171 During an investigation in 1962 of contamination of ground water by plating wastes in the South Farming- dale area (Perlmutter and others, 1963), samples of water at various depths in test wells were analyzed for ABS as well as for the principal contaminants in the plating wastes. This area is well suited for a study of ABS contamination because it is unsewered and the wastes from about 250. small homes are disposed of by means of individual cesspools or septic tanks. The area investigated by test drilling is about 4,000 feet long and about 400 to 1,400 feet wide. The land surface is a gently rolling plain that slopes southward from about 70 to about 40 feet above sea level. Surface FIGURE 2.—Aerial photograph of South Farmingdale area, showing water-table contours (heavier lines), in feet, and location of hydrogeochemical sections (lighter lines). Arrows indicate direction of ground-water flow. Datum is mean sea level. 732—780 0—64—12 0172 drainage consists of several narrow, shallow tributary streams which form the headwaters of Massapequa Creek (fig. 2). Scattered catch basins and storm- drainage trunk lines carry runoff from paved areas to nearby Massapequa Creek. METHODS OF INVESTIGATION In 1962, the Nassau County Department of Public Works installed about 90 test wells along selected streets and in the Vicinity of Massapequa Creek (figs. 2, 3, and 4). Nearly all the wells were constructed with 114— inch casing and a 3-foot drive point. Water samples were collected by means of a pitcher pump at 5-foot intervals during the driving of the wells. The samples were analyzed for ABS in the laboratory of the Nassau County Department of Health, generally 1 day after collection. The concentration of ABS was determined by a ten- tative method (American Health Association, 1960, p. 246—248), using methylene blue dye, chloroform extrac- tion, and colorimetric comparison of the extract with standard solutions. Although certain organic and inorganic compounds are known to interfere with the determination of ABS by the methylene blue method, the writers have considered this fact as well as the over- all chemical quality of the ground water and have con- cluded that determinations of ABS as low as 0.1 ppm are significant in the report area. Hence, the lower limit of contamination shown by the shading in figures 3 and 4 is indicated by the depth at which the concen- tration of ABS was approximately 0.1 ppm. Because of the limitations of the data the position of the zero isopleth of ABS could not be determined accurately. It is estimated, however, to be less than 20 feet below the lower limit of the shaded area shown on the sections. Water-level measurements made in selected wells were referenced to mean sea level to determine the shape and altitude of the water table and the direction of ground-water movement (fig. 2). GEOLOGIC AND HYDROLOGIC CONTROLS The water-bearing units of chief interest in the South Farmingdale area are an upper unit of glacial outwash of late Pleistocene age and an underlying unit of sand and clay of Late Cretaceous age (fig. 3). The upper Pleistocene deposits consist of beds of brown fine to coarse sand and gravel and some scattered thin lenses of silt, and have an average thickness of about 80 feet. Two core samples of the outwash deposits were tested for hydraulic properties by the Hydrologic Laboratory of the US. Geological Survey in Denver, Colo. One sample, typical of most of the QUALITY OF WATER upper Pleistocene deposits, consists of fine to coarse sand and some gravel. It has a permeability of 1,600 gallons per day per square foot and a porosity of 33 percent. The other sample, which represents a facies common in the lower part of the unit, consists of fine to medium sand, and has a reported permeability of 440 gpd per sq ft and a porosity of 37 percent. The higher value of permeability probably is more representative of the upper Pleistocene deposits as a unit. The Upper Cretaceous deposits consist chiefly of lenticular deposits of nonmarine gray fine sand, clayey and silty sand, and thin layers and lenses of clay. These deposits have relatively low permeability. As there is no evidence that water in the Cretaceous deposits is contaminated by ABS, they are not described further in this article. Water in the upper Pleistocene deposits is under water-table, or unconfined, conditions. It is derived mainly by subsurface inflow from the area north of South Farmingdale but also by downward percolation of precipitation (such recharge averages about 1 million gallons per day per square mile), effluent from cess— pools, and possibly some leakage from water mains and storm sewers. The water table ranges from about 15 feet below the land surface in the northern part of the area to less than a few inches at and near Massapequa Creek in the southern part (figs. 3 and 4). Contours of the water table (fig. 2) show that most of the water is moving southerly toward Massapequa Creek. The upstream bending of the contours in the vicinity of Massapequa Creek indicates that part of the ground water is discharged into the stream. The arrows on section A—A’ (fig. 3) show that the ground water is moving nearly horizontally, except for local downward components at shallow depths beneath the recharge basins and cesspools (not shown) and upward com- ponents beneath Massapequa Creek. Ground water is discharged from the area by sub- surface outflow, by lateral and upward seepage into Massapequa Creek, by discharge from a small number of lawn-sprinkling wells, and to a lesser extent, by di- rect evaporation from the water table and transpiration of plants whose roots tap the water table. By substi- tuting in Darcy’s law an average hydraulic gradient of about 12 feet per mile, laboratory determinations of permeability of 440 and 1,600 gpd per sq ft and a po- rosity of 33 percent, an average lateral ground—water velocity of about 0.5 to 1.5 feet per day is calculated for the upper Pleistocene deposits. On the basis of the overall lithology of the deposits, the average velocity is estimated to be about 1 foot per day under natural conditions. In the vicinity of pumped wells the rate of movement is somewhat greater. PERLMUTTER, LIEBER, AND FRAUENTHAL 0173 NORTH SOUTH MOTOR AVE K, . LAMBERTAVE , 0 Recharge basms A FALLWOOD PKWY ( c» I M C k KENTST PL’TT‘VE q Ia: o 2 N o g assapequa rec m l R ,\ ....-. ID ,\ vs 3 L; a SIB N __ __q _WatembLL .. . . . 40. 6.5;... 7 SEA 3 , LEVEL __________ 2393“". .————————————_—~ _— ‘—_ EXPLANATION (— Upper Pleistocene deposits é— ,\ \ (chiefly sand and gravel) / Q ___ _ / / 0.3 — — _ \ _ _ _ 80' lsopleth of ABS. in Contact <" parts per million Upper Cretaceous deposits Dashed where approximate/y lo- . . (— (chiefly fine sand,silt.and clay) _ 120, Test well and can-d. Haclmres ind/care decrease Directnon of ground- number in cancen/ran'on. lnrerva/ irregular water flow 0 400 800 1200 1600 FEET I . i . l I I A FIGURE 3.——Hydrogeochemical section parallel to the direction of ground-water flow, showing isopleths (lines of equal concentration) of ABS in 1962. CONCENTRATION AND MOVEMENT OF ABS The distribution of ABS in the ground water is the resultant of the coalescence of several hundred ran- domly distributed slugs of cesspool waste that have infiltrated to the zone of saturation. The slugs differ in volume and in concentration of ABS, and while moving downgradient they commingle and are diluted mainly by recharge from precipitation and by mixing with less contaminated ground-water underflow. The concentration of ABS in cesspools may be as high as 60 ppm, and the highest concentrations in the ground water generally are found within a distance of about 40 feet downgradient from a source cesspool and less than 20 feet below the water table. The pattern of distribu- tion of ABS is shown by the isopleths (lines of equal concentration) in the section parallel to the direction of ground-water flow (fig. 3) and in the sections oblique to the direction of ground-water flow (fig. 4). In evaluating the isopleths it is important to note that the first water sampled in most of the wells ranged from about 3 to 18 feet below the water table, so that water containing higher concentrations of ABS than those illustrated doubtless is in the upper few feet of the zone of saturation in some places. Determinations of ABS ranged from less than 0.02 to about 32 ppm. The depth of detectable contamination ranged from the water table to about 60 feet below. Although the ABS is distributed throughout the upper two-thirds of the saturated part of the upper Pleistocene deposits, at most depths the concentration is less than 1 ppm and would not be detected by the user. However, in a few places, such as the middepth intervals in well 67 on Motor Avenue (B—B’, fig. 4) and in wells 1 and 2 on Lambert Avenue (0—0’, fig. 4) the concentrations ranged from about 1 to 5 ppm. This local center of relatively high concentration of ABS may be due to wastes from an industrial park north of Motor Avenue, Contaminated water is shaded; lower limit shown at about 0.1 ppm of ABS. from commercial buildings on Motor Avenue, or from both sources. The downward sag in the isopleths of relatively high concentration at the extremities of sec- tion B—B’ (fig. 4) results from these areas being occu- pied by facilities such as parking lots and buildings which do not contribute cesspool effluent to the under- lying water table. An unusually high concentration of ABS, about 32 ppm, in water collected from a depth of about 6.5 feet below the water table in test well 28 (section F-F’, fig. 4), suggests that the well penetrates the center of a slug of wastes from a nearby cesspool. Except for anomalous patterns of contamination in the immediate vicinity of individual disposal systems, the zonation shown in sections D—D’ to F —F ’ (fig. 4) is probably typical of the general pattern of contamination beneath most unsewered residential areas in southern Nassau and Suffolk Counties. A few analyses of the contaminated water show a range in chloride content of 8 to 30 ppm, whereas the natural chloride content in the area is about 5 ppm. Similarly, the observed range in nitrate as N03 is 10 to 22 ppm in contaminated water, whereas the natural content is commonly less than 5 ppm. Concentrations of ABS, chloride, and nitrate higher than those re- ported above probably characterize the ground water immediately adjacent to cesspools. The bulk of the highly contaminated ground water flows at shallow depths toward the headwaters of Massapequa Creek and is discharged as surface water. lV‘ater at greater depths, containing moderate to low concentrations of ABS, moves downgradient as under- flow and discharges eventually in the lower reaches of Massapequa Creek. Although the ABS content of Mas— sapequa Creek in April 1963 decreased from about 1 ppm near the headwaters to about 0.6 ppm near the mouth of the stream (south of the report area), the actual load of ABS increased from about 0.5 pound per 0174 QUALITY OF WATER B WOODWARD Plevg. B ’ 2 3 3 :8 8 g EXPLANATION 50' Watermble 65 68 75 A O Test well and number Horl'zonra/ ticks [ha’l'cafe sampling po/nrs , C wooo WARD PKWY C 78 14 16 —o.5 ————— lsopleth of ABS, in parts per million - Dashed where approximateb/ lacs/ed. Hachures/nd/ca/e decrease in concenrrah'an. Inferva/ irregular Water table Ix deposfis EAST DRIVE KENT sr 7.”. z._.._r_‘.-.. -...J.r~ Upper Pleistocene deposits O 100 200 300 400 500 FEET 1 l I J LIJJII|I|A1 FIGURE 4.—Hydrogeochemical sections oblique to the direction of ground-water flow, showing isopleths (lines of equal concentration) of ABS in 1962. Contaminated water is shaded; lower limit shown at about 0.1 ppm of ABS. PERLMUTTER, LIEBER, AND FRAUENTHAL day near the headwaters to about 25 pounds per day near the mouth, due to the pickup of contaminated ground water by the stream. POTENTIAL THREAT OF CONTAMINATION OF WATER IN THE CRETACEOUS DEPOSITS Because the contaminated water in the South Farm- ingdale area is moving mostly laterally, it is unlikely under present conditions that significant amounts of ABS, if any, have moved down from the upper Pleisto- cene deposits into the Cretaceous deposits, which are the source of water for most public-supply wells. No public-supply wells are in the immediate area of investi- gation, but analyses of water from nearby public-supply wells, which range in depth from about 150 to 600 feet, Show no indication of ABS to date. In the vicinity of the main ground-water divide, north of the report area, ground water has a natural downward gradient which favors slow contamination of the Cretaceous deposits by downward leakage, but evidence of this has not been reported. Near the north and south shores of Nassau County, water in the deep aquifers generally moves upward to discharge areas at the shore or ofl'shore. This natural flow pattern inhibits downward leakage of cesspool waste in the south shore areas. In some parts of Nassau County, however, par- ticularly in the southern half, heavy and continuous pumping of public—supply wells screened in the Cre- taceous deposits could disturb the natural flow pattern described above and create local and, eventually, exten— sive areas of downward gradient between the upper Pleistocene deposits and the Cretaceous deposits, which would induce some downward movement of contami- nated water. Such movement would be extremely slow where, as is generally the case, thick_beds of relatively low permeability separate the water-bearing zones, and the hydraulic gradients developed by pumping are low. Although, under present hydraulic conditions, pump— ing is unlikely to cause extensive downward movement of contaminated water into the Cretaceous deposits for many tens of years, additional studies should be made to locate and to monitor those areas where unusual geo- hydrologic conditions could result in contamination sooner than anticipated. Parts of the deep aquifers may be contaminated locally through breaks in well casings or inadequate grouting of the annular space around casings of wells drilled by the rotary method. 6% 0175 Regulatory agencies should be constantly alert to this subtle method of contamination so that it does not become a serious problem. Further studies of hydraulic gradients and variation in vertical permeability of the Cretaceous deposits as well as the adsorptive and ion—exchange capacities of Cretaceous silts and clays are required before more quantitative predictions can be made of the rate of movement of ABS and associated contaminants into the deeper water-bearing zones in Nassau County. Even if more degradable detergents are produced in the near future, the problem of contamination by other cesspool wastes will not be eliminated. Therefore, most investi— gators agree that a public-sewer system is the only practical remedy. Southwestern Nassau County is sew- ered already and, within the next 20 years, the South Farmingdale area and most of the remainder of the county probably will be sewered also. As cesspools are eliminated, ABS already in the ground water generally will be diluted gradually by recharge from precipitation, underflow, dispersion, and diffusion. On the other hand, the ABS concentration may increase temporarily in some places after sewering, as slugs of contaminated water move downgradient through uncontaminated or less contaminated areas to points of natural discharge. The time required for the removal of the bulk of the ABS from the water by nat— ural discharge from the upper Pleistocene deposits may be several tens of years. However, in most places, dilu— tion of the contaminated water below the lower limit of foaming, about 1 ppm, should take place within a few years after sewering, as the highest concentrations are generally found a short distance below the water table where recharge from precipitation is most effective as a dilutant. REFERENCES American Public Health Association, 1960, Standard methods for the examination of water and waste water: New York, Am. Public Health Assoc, Inc, 11th ed., 626 p. New York State, 1963, Progress report of the Temporary State Commission on Water Resources Planning: Legislative Doc. (1963) No. 40, 210 p. Perlmutter, N. M., Lieber, Maxim, and Frauenthal, H. L., 1963, Movement of waterborne cadmium and hexavalent chro- mium wastes in South Farmingdale, Nassau County, Long Island, N.Y.: Art. 105 in US. Geol. Survey Prof. Paper 475—0, p. Cl79—C184. Public Health Service, 1962, Drinking water standards: U.S. Public Health Service Pub. 956, p. 22—25; also in Fed- eral Register, Mar. 6, p. 2152—2155. US. GEOLOGICAL SURVEY RESEARCH 1964 RELATION OF CHEMICAL QUALITY OF WATER TO RECHARGE TO THE JORDAN SANDSTONE IN THE MINNEAPOLIS-ST. PAUL AREA, MINNESOTA By MARION L. MADERAK, Lincoln, Nebr. Work done in cooperation with the Division of Waters, Minnesota Department of Conservation Abstract—Maps that show areal variations in concentration of dissolved solids can be used to detect possible recharge areas and direction of ground-water movement. For the Jordan Sandstone in the Minneapolis-St. Paul area, the anomalous areas of low concentration of dissolved solids coincide with the recharge areas indicated by the highest elevations on a piezo- metric map. Lines of equal dissolved-solids concentration of ground water from the Jordan Sandstone of Cambrian age in the Minneapolis-St. Paul area, Minnesota, agree closely with patterns of ground-water movement as deduced from water-level contour maps. Recharge to the Jordan is indicated by high head and low dissolved- solids concentration of the ground water; migration of water is toward areas of 10W head and high dissolved’ solids concentration. Alluvial and glacial deposits of Quaternary age, rang- ing from clay to boulders, are the youngest deposits in the area (fig. 1). Limestone, dolomite, shale, silt- stone, and sandstone of Ordovician age and shale, silt- stone, and sandstone of Cambrian and Precambrian age form the bedrock. Crystalline basement rocks un- derlie sedimentary rocks of Precambrian age. The con— solidated sedimentary rocks have been folded into a broad basin, slightly elongated northeast-southwest and centered several miles north of the confluence of the Minnesota and Mississippi Rivers. The approximate extent of the structural basin is indicated in figure 2 by the lines showing the eastern and western limits of the Jordan Sandstone. Small yields of water can be obtained from almost all rocks in the basin, but large yields of water sufficient for municipal and industrial supplies generally are available only from the glacial drift, St. Peter Sand- System Geologic unit “2:23“ Lithology Alluvium 0—150 V 1 2' (U I: L 8 g Glacial drift 0-400 0 _ , becorah Shale 0-95 , Platteville Limestone 30-50 53,—? I: I. K.“ ' 1‘ E St. Peter Sandstone 140—160 ’ 13 ° ShaRoitge Dolomite 35—60 New Richmond _ ' Sandstone _0_19_7 Oneota Dolomite 70'90 Jordan Sandstone 80—105 'i P I St. Lawrence I Formation 35'70 C Franconia 100_200 E g Sandstone ' 5 i E I—i— N U Galesville Sandstone Eau Claire Sandstone 250—400 ' Mount Simon Sandstone :: Hinckley Sandstone I {if of Winchell (1886) 75'175 . 1 ~ ' ’ E Fond du Lac Sand— to stone of Winchell i 1 (1899) 1000+ E (Red clastic beds) St. Peter aquifer Shakopee- Oneota- Jordan aquifer Franconia- Galesville aquifer Mount Simon- ? Hinckley aquifer FIGURE 1.—Se(limentary sequence in the Minneapolis- St. Paul area. U.S. GEOL. SURVEY PROF. PAPER 501-0, PAGES C176—Cl79 C176 MADERAK 94° EXPLANATION 700—— Elevation of piezometric surface above sea level Contour interval 20 feet » Direction of ground-water flow 452 Jordan —/ J SCOTT / / Western limit of lJordan Sandstone 0177 Eastern limit of Jordan Sandstone in Minnesota ’3‘ M Rose ou/\ O 5 Illiil 10 15 MILES l J FIGURE 2.—Map of the piezometric surface of water in the Jordan Sandstone (after Liesch, 1961). stone, Shakopee Dolomite, Oneota Dolomite, Jordan Sandstone, Franconia Sandstone, Galesville Sandstone, Mount Simon Sandstone, and Hinckley Sandstone of Winchell (1886). Because the Jordan Sandstone un- derlies most of the basin, has a uniform thickness, lies at fairly shallow depths, yields the large amounts of water necessary for industrial and municipal demands, and contains water of fairly good quality, it is the most commonly used source. The Jordan is a loosely ce- mented fine- to coarse-grained White sandstone that dips about 20 feet per mile toward the center of the basin. Exposure of the sandstone to an oxidizing atmosphere changes the Jordan from white to yellow. Immediately underlying the glacial drift in much of the area are the St. Peter, Shakopee, Oneota, and Jordan aquifers. The Shakopee, Oneota, and Jordan C3178 Ca Cl + F + N0: CATIONS ANIONS No. on No. of wells or Average dis- diagram sources of surface solved solids Geologic unit water sampled (ppm) Ground water 1 _______ 43 384 Glacial drift. 2 ______ 8 360 St. Peter Sandstone. 3 ______ 7 360 Shakopee and Oneota Dolomites. 4 ______ 23 266 Jordan Sandstone. 5 ______ 12 356 Franconia and Galesville Sandstones. 6 ______ 9 309 Mount Simon Sandstone and Hinckley Sandstone of Winchell (1886). Surface water 7 ______ 9 (8 lakes and 205 1 stream). FIGURE 3.—Average chemical character of water from principal sources in the Minneapolis—St. Paul area, in percentage of total equ1valents per million. are hydraulically connected and have, therefore, been re— garded as a single aquifer. According to Liesch (1961) water in the central part of the basin (downtown Min- neapolis—St. Paul area) can move directly from the St. Peter through the dolomite section to the Jordan Sand- stone. The New Richmond Sandstone of Ordovician age is thin and yields little water to wells. Except in the central part of the basin and in recharge areas, the Oneota Dolomite contains a shale or siltstone that partly restricts the downward movement of water to the Jordan. Because of the restriction of the downward movement of water, the quality of the water in the QUALITY OF WATER Jordan Sandstone is slightly different from that in the overlying formations. Underlying the Jordan Sand- stone is the St. Lawrence Formation, which forms the lower confining layer for the Shakopee-Oneota—Jordan aquifer. Recharge to the aquifers overlying the St. Lawrence Formation is mostly from the glacial drift. Natural discharge is mostly from springs and seeps along the Minnesota and Mississippi Rivers. Because they are hydraulically connected, the Franconia Sandstone and underlying Galesville Sandstone are here referred to as the Franconia—Galesville aquifer, and the Mount Simon Sandstone and Hinckley Sandstone of Winchell (1886) are referred to as the Mount Simon—Hinckley aquifer. Water from the principal sources in the Minneapolis— St. Paul area is of the calcium bicarbonate type and is similar in chemical character to water from eight rep- resentative lakes and one stream in the area (fig. 3). Of the principal sources of water, the Jordan Sand- stone has the lowest average dissolved-solids content and the Mount Simon—Hinckley has the next lowest average. The direction of ground-water flow in the Jordan is shown by a piezometric map (fig. 2). An isocon map (fig. 4) shows areal variations in the total concentration of dissolved solids in water from 23 wells that tap the Jordan Sandstone and are evenly spaced across the Minneapolis-St. Paul artesian basin. Each isocon on the map connects points of equal concentrations of dis— solved solids. Except for the anomalous areas near Ex- celsior and White Bear Lake, the dissolved-solids con- centrations indicated by the isocons tend to increase toward the west; the recharge from the glacial drift in the western part of the basin generally has a higher average dissolved—solids concentration than the recharge in the eastern part of the basin. The anomalous areas near Excelsior and White Bear Lake (fig. 4) coincide fairly well with the highest water-surface elevations (fig. 2) ; future investigations may show that detailed chemical—quality data can be useful in determining areas of recharge and direction of ground-water move- ment. The recharge moves generally from the Ex- celsior and White Bear Lake areas into the drift aqui- fers, through the St. Peter, Shakopee, and Oneota to the Jordan, and then downdip to the central part of the basin. Some recharge to the Jordan also occurs in the downtown Minneapolis—St. Paul area from the over- lying St. Peter, Shakopee, and Oneota (Liesch, 1961) ; this recharge may account for the irregularity of the isocons in the downtown area. Although the isocon anomalies and the recharge areas coincide for the Minneapolis-St. Paul artesian basin, some anomalous dissolved—solids concentrations may not MADERAK 0179 94° 93° 1 I J/ l / Eastern limit of EXPLANATION i % //// Jordan Sandstone ' M. t 275— . // T_L_'En_eso;>/ Line of equal concentration /’ % of dissolved solids A N O K A ’/ Forest Contour interval 25 ppm // I Lake ‘e~ ’ _.—r' 6:915" Anoka // SI ‘ ’1 - —/ ( /,§a¢{ ,2 / / / .- // I /’ l / / / H E N N E P I N I I // .— 1 R A M S E Y I 1/ b )7. :/ / I 5 ./ / I 37 , / 45° ’ “3‘90 V \' . ..—_—_ r . I /.' r ‘§_ ~\ .. . St P l - ‘ .dl‘h—i ‘V‘ 26 / au anetonka ‘7‘,- yr 3 , Lake (L , 500 winneapoli . \ ' 2.. 00 / ' " ,_m\-___..2.... 9/ ,/ é ) \ \ M 8.001 lia CARVER 50W ’ ’/"Bi1’i>14‘ .@ v e e ame aw ,xrA ’JJI/ l I /Western limit of I, Jordan Sandstone l 4 | LLIIII 10 I 1'5 MILES FIGURE 4.—Isocon map of dissolved solids in water from the Jordan Sandstone. indicate recharge areas and instead may only be the result of well construction that allows water from one zone to mix with that of another. However, if piezo- metric information for an aquifer is scanty or unre— liable, isocon maps used in conjunction with the piezo— metric information may be of value in locating major recharge areas and in relating changes in the dissolved— solids concentration to the ground-water movement. 51‘ REFERENCES Liesch, B. A., 1961, Geohydrology of the Jordan aquifer in the Minneapolis—St. Paul area: Div. Waters, Minnesota Dept. Conserv., Tech. Paper 2. Winchell, N. H., 1886, Revision of stratigraphy of the Cambrian in Minnesota: Minnesota Geol. Survey Ann. Rept. 14. 1899, Geology of St. Louis County, Minn: Minnesota Geol. Survey final rept., v. 4, p. 502—580. GEOLOGICAL SURVEY RESEARCH 1964 GEOHYDROLOGY OF STORAGE OF RADIOACTIVE WASTE IN CRYSTALLINE ROCKS AT THE AEC SAVANNAH RIVER PLANT, SOUTH CAROLINA By GEORGE E. SIPLE, Columbia, SC. Work done in cooperation with the US. Atomic Energy Commission Abstract—Geologic, hydrologic, and water-quality studies indicate two distinct aquifer systems at the Savannah River Plant: one in crystalline basement rock, and the other in the overlying 900—foot sequence of sedimentary strata. A confining layer of saprolite separates the two systems, preventing signifi- cant exchange of water between them and retarding circulation within the crystalline rocks. Safe storage of radioactive wastes in sound crystalline rocks appears feasible. A major question in appraising the feasibility of storage of partially cooled high-level radioactive waste in mined excavations deep in crystalline basement rocks at the Atomic Energy Commission Savannah River Plant is whether, in case of accidental escape of radio- active material to the basement rocks, the radioactive material would contaminate overlying aquifers and surface streams. Two basic considerations are whether the basement rocks are permeable and whether water in the basement rocks can move freely into the overlying sedimentary rocks. Geologic and hydrologic studies reported here indicate that a laterally extensive layer of saprolite effectively separates an aquifer system in the basement rocks from aquifers in the overlying sedimentary sequence. This affords one of several substantial barriers to the migra- tion of the waste; the presence of kaolinitic clay in the overlying Tuscaloosa Formation, with its attendant high ion-exchange capacity, represents another. Thus, at this intermediate stage of the project, storage of high-level waste in cavities in the basement appears feasible. Subsequent reports, based on information from at least 11 additional test wells and extensive hydrologic and chemical data, will indicate in a more definitive manner the possibility of using this storage medium. The crystalline rocks in the vicinity of the Savannah River Plant consist of chlorite-hornblende schist, quartz—feldspar gneiss, hornblende gneiss, and slate of Precambrian age intruded by granite of Paleozoic age (Carboniferous?). The schistosity strikes northeast and dips 55° to 75° SE. The crystalline rocks are over- lain by a succession of gently southeast-dipping uncon- solidated sediments of marine, deltaic, estuarine, and continental origin of Cretaceous and younger age. The thickness and general description of the lithology and water-bearing characteristics of the individual rock units are given in the accompanying table. In the preliminary investigation reported here, four test holes (DRE 1, 2, 3, and 4) were drilled in an area near the center of the plant property (fig. 1 and inset of fig. 2). These holes, which were more than 1,900 feet deep, encountered fresh crystalline rock at depths ranging from 895 to 970 feet. The holes were drilled by conventional rotary methods until hard crystalline rock was reached. A log was made as the hole pro— gressed, and continuous core was taken of about 1,000 feet of the crystalline rocks at each test hole. Gamma- ray, neutron, and temperature logs and a directional survey were made of the entire section at each hole. Resistivity logs were made of several observation wells in the sediments. In addition, sonic logs were made in the crystalline-rock section of holes DRB 2, 3, and 4; caliper and microlaterolbgs were made in the crystal— line-rock section of all four holes. The gamma-ray logs were particularly useful for distinguishing the contact of the Tuscaloosa Formation with the saprolite at the top of the crystalline zone (fig. 2). Neutron logs provided supplemental confir- mation of this identification. The sonic logs and U.S. GEOL. SURVEY PROF. PAPER 501-C, PAGES ClSO—C184 0180 SIPLE C181 Geologic units in the vicinity of the Savannah River Plant System Series Geologic unit Thickness Lithology and water-bearing characteristics (feet) Recent Alluvium (unnamed) Quaternary Wicomico, Sunder- land, Coharie(?), and Hazlehurst(?) Formations. Pleistocene Stream-deposited clay, silt, sand, and gravel; tan to gray; underlies flood plains and bordering terraces; of minor importance as an aquifer. 0—40 Alluvial and estuarine deposits of tan, orange, and red sand and sandy clay; underlie coastal terraces; yields sufficient Water for domestic supply. Miocene Hawthorn Formation Marine and colluvial deposits of sandy clay enclosing lenses of gravel and cut by elastic dikes; yields small to moderate amounts of water to wells. 0-80 Upper Barnwell Formation Marine and colluvial deposits of sandy clay and crossbedded to massive fine to coarse sand; red, brown, yellow, and buff; yields sufficient water for domestic supply. 0—90 Tertiary Eocene Middle McBean and Congaree Formations. Marine deposits of fine to coarse glauconitic quartz sand interbedded with clay, sandy marl, and siliceous limestone; sand is yellow brown to mus- tard green, and clay and marl are green, red, yellow, and tan; yields sufficient water for moderate to large-scale industrial and municipal use. Water generally is hard and in places high in dissolved iron content. 100—250 Upper Cre- Cretaceous ('3) taceous(?) Ellenton Formation Marine and estuarine deposits of medium- to dark- gray micaceous coarse sand and gravel and dark- gray to black lignitic micaceous sandy clay con- taining disseminated crystals of gypsum; yields moderately large to large amounts of water to wells. Water generally moderately high in sulfate and quite high in iron content. 10—100 Upper Cre— Tuscaloosa Formation C retaceous taceous Marine, estuarine, deltaic, and continental deposits of micaceous quartzitic and arkosic sand and gravel interbedded with clay and kaolin; sand and gravel is tan, buff, red, and white; clay is gray, red, brown, and purple; kaolin is white; yields as much as 2,000 gpm to 8- to 12-inch gravel-packed wells. Water is soft and is low in dissolved-solids content. Average coefficient of transmissibility, about 200,000 gpd per foot. 300—600 Precambrian Crystalline rocks of the Carolina slate belt and Charlotte belt. to Carboniferous (?) Basement rocks consisting of chlorite-hornblende schist, quartz-feldspar gneiss, hornblende gneiss, and slate of Precambrian age intruded by granite of early Paleozoic to Carboniferous(?) age; upper- most part consists of saprolite formed during long exposure to weathering. Fractures in fresh rock yield small amounts of water to wells. In out- crop areas, water in granite generally is soft and low in total dissolved-solids content, Whereas water in mafic rocks generally is harder and more mineralized. In deeply buried rocks, water is very highly mineralized. caliper logs were valuable in distinguishing fractured from unfractured crystalline rock. In most holes the zone of fractured rock extended 400 to 500 feet below the base of the saprolite layer. Although saprolite was identified at each of the four test holes, the principal evidence for its lateral conti- nuity and impermeable character is the marked differ- ence in head and quality between confined water in the basement rocks and water in the Tuscaloosa Formation. Fractures are common, much more so in the upper part of the fresh crystalline rock than at greater depths. Many of these fractures have been healed by quartz, calcite, chlorite, and zeolite, but the open fractures are interconnected and will transmit water to a well that intersects them. The crystalline rocks thus constitute a deeply buried artesian aquifer. The water is confined by a layer of saprolite, or disintegrated rock (mostly clay) Which formed in a subaerial environment when the basement rocks were exposed to weathering prior to the deposition of the Tuscaloosa Formation in Late Creta- 0182 82°OO’ 33" 30’ @Wilhston ( Barnwell p SAVANNAH RIVER PLANT 1 O M | L ES Allendaleg/J 33° FIGURE 1.—Location of Savannah River Plant and report area. ceous time. Presumably the saprolite was compacted and possibly somewhat altered after being buried beneath the sedimentary strata. The piezometric surface of the water in the crystal- line rocks is less than 100 feet below the land surface throughout the test area and is above the valley floor of the Upper Three Runs (fig. 2). Moreover, the head in the basement rocks is about 20 feet higher than in the Tuscaloosa throughout the test area. The configuration of the piezometric surface in the Tuscaloosa, as shown by Siple (1957), indicates that the direction of water movement in the vicinity of the Savannah River Plant is toward the south and south- west and that discharge is effected laterally toward streams draining the outcrop area and vertically (up- ward) by leakage into the Savannah River in an area downstream from the outcrop. The hydraulic gradient between the test area and the Savannah River is 4 to 5 feet per mile; permeability and porosity of the coarser beds were determined to be approximately 1,500 gallons per day per square foot and 30 percent, respectively. Substitution of these values in an expression for the Darcy law (Darcy, 1856) indicates an average velocity of water movement in the Tuscaloosa Formation in this area to be about 0.5 foot per day, or about 185 feet per year. Chemical analyses indicate a marked difference in quality between water from the Tuscaloosa and water from the basement rocks at the test area. The specific conductance of water from the basement rocks exceeds ENGINEERING HYDROLOGY 1,000 micromhos, while that of water from the Tusca- loosa is generally less than 100 micromhos. For ex- ample, preliminary tests indicate a conductivity of 1,250 micromhos for water from well DRE—3, whereas the water from well 35—H, screened in the Tuscaloosa Formation in the same area, has a conductivity of only 43 micromhos. The principal cation in the water from the crystalline rocks at the test area is sodium, and the principal anion is sulfate. The concentration of these constituents—and also of chloride, potassium, magne- sium, and bicarbonate—is much higher than in areas where the crystalline rocks crop out or are near the sur- face. Water from the Tuscaloosa is typically of the sodium chloride type with low dissolved-solids content. A plausible explanation for the occurrence of fresh water in the crystalline rocks in and near the area where they crop out and of highly mineralized water in the crystalline rocks when they are deeply buried is illus- trated on figure 3. In the outcrop area the water in these rocks is unconfined because the saprolite is not continuous and, where present, it is more permeable than where deeply buried beneath thick sedimentary strata. Recharge results from the direct infiltration of precipi- tation, and water in the zone of saturation is free to move laterally to places where it can escape either to the land surface or into overlying sediments. Down- gradient from the “lip” of the continuous sheet of sapro- lite, little or no escape of water from the crystalline rocks is possible and the water in these rocks is stagnant or nearly so. An alternate explanation to this continuity system is the possibility that the saprolite functions as a semi- permeable membrane and that osmotic diffusion (by movement of Tuscaloosa water across the membrane of saprolite confining the highly concentrated rock water) might account, in whole or in part, for the greater hy- drostatic pressure of water in the crystalline rock over that in the overlying sediments. The evidence presented here lends support to a ten- tative conclusion that storage of high-level radioactive wastes in mined caverns within the crystalline rocks would not result in either contamination of water in the overlying sedimentary strata or in contamination of streams. Even if the water filling fractures in the upper part of the crystalline rocks were to become con- taminated, the layer of saprolite would present a formi- dable barrier to the escape of the contaminated water into the overlying aquifers and thence to points of natural discharge or withdrawal through wells. The chemical or physical factors involved in the compati- bility or suitability of the basement rock for storage of the radioactive waste are discussed in general terms by Horton (1961) and Front (1962). 0183 SIPLE .53.» anon?” 95 5 $695 B>3L3a3 Eda .38: amen we mwog wnmkonm 37% £5on oBoBeGIN 853% 00w | VV 1000 I I00? I :oZmEgom mmoofiomz... IOON l lIIlIIIlIIII|IIlIII|IllllI\| [dig 3=< corn—thou. 2035mm. :oszLOL EoctsmI \v‘ OOV+ .mEEmo I 5% gang >9. ENE mum—mo 3.3: mEso ow 33:33. E< NH >m...wEEm0 Hum—mo _ 0184 ENGINEERING HYDROLOGY SE Water table in out- crop area of crys- talline rocks Piezometric surface of water in crystalline rocks SAVANNAH : RIVER l l PLANT . l l of saprolite Outflow of water into sedimentary rock Interface between fresh and stagnant water Continuous layer of saprolite Confined, almost stagnant Unconfined fresh or partially water in crystalline rocks mixed water in crystalline rocks FIGURE 3.—Diagrammatic section illustrating a possible explanation for the occurrence of both fresh and salty water in the crystalline basement rocks. REFERENCES River Plant: Second General Disposal of Radioactive Wastes Conference, Chalk River, Canada, Sept. 26—29, 1961, Darcy, Henri, 1856, Les fontaines publiques de la ville de Dijon: U.S. Atomic Energy Comm., Div. Tech. Int, TID—7628, p. Paris, Victor Dalmont, 647 p. 380—390. Horton, H. 1-1., J r., 1961, Radioactive waste management at the Siple, G. E., 1957, Geology and ground water in parts of Aiken, Savannah River Plant: DP—564, E. I. du Pont de Nemours, Barnvvell and Allendale Counties, South Carolina: US. 13 p. Geol. Survey open-file report, 131 p. Prout, W. G., 1962, Studies of the containment of radioactive US. Army, Corps of Engineers, 1952, Geologic-Engineering In- wastes in underground mined caverns at the Savannah vestigations, Savannah River Plant. 5% GEOLOGICAL SURVEY RESEARCH I964 STREAM DISCHARGE REGRESSIONS USING PRECIPITATION By H. C. RIGGS, Washington, D.C. Abstract—Monthly mean discharge from two pairs of basins, one pair adjacent and one pair 100 miles apart, is related by use of each of four regression models. Best results were ob- tained from the two models which included basin precipitation. A common problem in hydrology—that of estimating stream discharge at times not included in the period of gaging—is commonly solved by a regression on stream discharge at a nearby site having a longer record, or by a regression on basin precipitation. D. R. Dawdy (written communication, 1960) has pointed out that three different types of regression models are useful in estimating stream discharge and that the appropriate one for a particular problem de- pends on the distance between the basins producing the discharges. He postulates that for adjacent basins of small size, the difference in precipitation would be negligible and a simple regression between discharges would give results as good as those from a more sophis- ticated model. For basins a great distance apart the relation between discharges would be slight and best results would be expected from a regression of discharge on precipitation. For an intermediate distance between basins, multiple regressions on discharge and precipita- tion would give the best results. This article suggests useful regression models and presents results of a limited empirical study that partly verify Dawdy’s postulates. The majority of the dis- charge-precipitation relations in the literature are ap- plied to annual mean discharge. This study is con— cerned with monthly mean discharge. Monthly mean discharges of a stream for different calendar months are not homogeneous data because the discharges for individual calendar months have differ- ent means and variances. In order that the data used in this study be homogeneous and not serially correlated the data for only 1 calendar month of each year is used in each regression. The monthly mean discharges of nearby streams for any given calendar month are quite similarly affected by antecedent conditions. If streams are similar hy- drologically, particularly with respect to base-flow characteristics, the variation of individual points from a curve of relation between concurrent discharges is largely due to differences in precipitation during the month. Therefore, inclusion of precipitation values on the two basins should improve the relation. Precipitation can be included in the regression model in several ways. No one way is entirely satisfactory from a physical standpoint because an effect (discharge) is being related to another effect (discharge) and to the two respective causes (precipitation on each of the ba- sins). Nevertheless, the addition of the precipitation values in some arbitrary form often results in appre- ciable improvement in the discharge-discharge rela- tion. The model used in this investigation is log QA=log a+b1 log (23+le log (PA/PB), (1) where QA and QB are discharges from the two basins, PA and PB are the respective concurrent precipitation values, 61 and 62 are regression coefficients, and a is the regression constant. Model 1 is considered suitable for the condition in which the discharge from a nearby basin is the primary independent variable and the precipitation values of the two basins are additional but less influential variables. As the distance between the two basins increases, it is postulated that the relation between the discharges de- teriorates until the simple relation between discharge from the dependent basin and precipitation on that basin is better than the simple relation between dis- charges from the two basins. If the two basins are gen- erally affected by the same storms the discharge from the independent basin may be used as a measure of the effect of antecedent conditions on the discharge-precipi- tation relation. One way to do this is suggested below. It is a variation of a method used by Carter and others (1949). U.S. GEOL. SURVEY PROF. PAPER 501-C. PAGES 0185—0187 0185 C186 02 LOG QA LOG o a O3 03 LOG PA LOG Plg FIGURE 1.—Schematic discharge-precipitation relations for two basins affected by the same storms. Symbols: QA and Q3, discharges from the two basins; PA and Pa, respective concurrent precipitation values. Suppose it is desired to extend the short record of March mean discharges from basin A on which long records of precipitation are available. Long records of both discharge and precipitation are also available on basin B which is at a considerable distance from basin A. If antecedent conditions similarly affect the dis- charges from the two basins the deviations of corre— sponding points from the respective discharge—precipi- tation relations would be in the same direction. (See figure 1.) Under these conditions the simple discharge-precipi- tation relation for basin A can be improved by use of the deviations of plotted points from the discharge- precipitation relation for basin B. On figure 1, the plotting of point 1 on both relations indicates greater discharge than expected from the measured precipita- tion, presumably as a result of greater than average carryover from the preceding period. Points 2 and 3 indicate less than average carryover. Deviation of a plotted point from the relation line for basin B can be expressed as log (QB/ QB) where QB is the measured value and QB is the value from the rela— tion line corresponding to P3. Then the regression model utilizing this variable would be log QA=10g a+ 5. log PA+bz log (QB/QB) (2) The usefulness of models 1 and 2 can be measured against the results obtained from the corresponding simple models: log QA=log a-H)l log PA, and log QA=log a+61 log Q3. (3) (4) Empirical tests were made using each of the 4 models and data from 3 basins in the Mississippi Embayment of Tennessee. Figure 2 shows location of the basins and of the precipitation stations. Drainage areas of Wolf River at Rossville, Hatchie River at Bolivar, and North Fork Obion River near Union City are 503, 1,430, and 480 square miles, respectively. The Hatchie River and Wolf River basins are adjacent. The North Fork THE ORETICAL HYDROLOGY 36°- TENNESSEE MISSISSIPPI 35°- 0 10 20 3O 40 50 MILES FIGURE 2.——-Map of western Tennessee showing the location of the drainage basins (broken lines) and precipitation sta- tions used in this study. Precipitation stations: A, Mayfield, Ky.; B, Union City, Tenn; 0, Dresden, Tenn; D, Moscow, Tenn. ; E, Bolivar, Tenn. ; F, Selmer, Tenn.; G, Corinth, Miss. ; H, Holly Springs, Miss; and I, Boonville, Miss. 16 (/2 LL 0 8 12——~————— ._. E a a: 8 < I o 9 o z 4“— < Lu 2 0 OCT NOV DEC JAN FEB MAR APR." MAY JUNE JULY AUG SEPT FIGURE 3.—Distribution of discharge, by months, of Wolf River at Rossville, Tenn, 1930—50. Obion River and the Wolf River basins are 100 miles apart. The distribution of discharge by months for Wolf River at Rossville is shown on figure 3. RIGGS The discharge variables used were monthly means. Precipitation for each month was obtained by averag- ing precipitation measured at several stations in each basin. Precipitation on the Wolf River basin above Rossville is the mean of precipitation totals for Moscow and Bolivar, Tenn., and Holly Spring, Miss. Precipita- tion on the Hatchie River basin above Bolivar is the mean of precipitation totals for Bolivar and Selmer, Tenn., and Corinth, and Booneville, Miss. Precipita- tion on the basin of the North Fork Obion River above Union City is the mean of precipitation totals at Union City and Dresden, Tenn., and Mayfield, Ky. The discharge of Hatchie River at Bolivar was re— lated to precipitation and to discharge of and precipi- tation on the basin of Wolf River above Rossville for each of the months January, March, May, July, Septem- ber, and November, using each of the four regression models. The discharge of North Fork Obion River at Union City was related to the same factors in the Wolf River basin for the same months and using the same regression models. Values of QB were obtained from graphical relations between discharge and precipita— tion for Wolf River. Results are shown in figure 4 in terms of the standard error of estimate. Study of figure 4 indicates the following: (1) In general the discharge of Hatchie River can be estimated more closely from the discharge of the adjacent basin of Wolf River than from precipitation on the Hatchie River basin (model 4 shows lower standard errors than model 3 except for March). (2) In general the discharge of North Fork Obion River can be estimated more closely from basin precipi- tation than from the discharge of Wolf River 100 miles away (model 3 has lower standard errors than model 4 except for January). (3) Use of model 1, which includes a precipitation variable, reduces the standard error appreciably for most months with respect to model 4, both for adjacent basins and for basins 100 miles apart. (4) Model 2, which includes an index of antecedent conditions based on discharges of another stream, pro- vides a smaller standard error than model 3 which is the simple discharge-precipitation relation. The ad« vantage of model 2 over model 3 is large for the adja- cent basins and moderate for the basins 100 miles apart. (5) N 0 clear superiority of one regression model for a particular pair of stations for all months is indicated. (6) The reliability with which monthly mean dis— charges can be estimated varies considerably with the calendar month. The results of this empirical study partly verify 6% 732—760 0—64—-—13 0.3 0.2 / 0‘1 C‘\ \’ ///’ Hatchie vs.Wolf \\‘\ /’ (adjacent basins) \:—'/ ~I g o I I | I z 3 (D 9 0.5 _ E of O E DJ 0.4 — D I: < D E 0.3 — ’— w 0.2 —- 0 1 _ ‘.,I' North Fork of the Obion vs. ' ‘ Wolf (basins 100 miIes apart) 0 I I I I I I JAN. MAR. MAY JULY SEPT. NOV. EXPLANATION 1. log 04:10g a,+b, 10g Qz+b2 log (Pa/Pa) 2. log 94:10g a.+b, log P4+b2 log (QB/bx) 3. log Qi=log c+b, log P4 4. log Qx=log a+b, 10g QB FIGURE 4.—Reliability of the regressions based on models 1—4. Dawdy’s postulates as to the conditions under which each of the three types of regression models are useful for estimating stream discharge. However, the inclu- sion of a variable describing the precipitation totals on each basin apparently will improve the discharge-dis- charge relation even for adjacent basins which are as large as 500 square miles. Results of this study also showed that the discharge-precipitation relation on a basin may be improved by including an index of ante- cedent conditions based on discharge of a stream basin 100 miles away. REFERENCE Carter, R. W., Williams, M. R., LaMoreaux, P. E., and Hastings, W. W., 1949, Water Resources and hydrology of southeast- ern Alabama: Alabama Geol. Survey Spec. Rept. 20, p. 187—195. GEOLOGICAL SURVEY RESEARCH 1964 RELATION OF ANNUAL RUNOFF TO METEOROLOGICAL FACTORS By MARK W. BUSBY, Topeka, Kans. Abstract—The average annual runoff at 62 selected stations throughout the conterminous United States was related to 9 meteorological factors as recorded at a US Weather Bureau first-order weather station near each point of runoff study. Seven of these factors were significant at the 80—percent level or higher. On the basis of these 7 factors, the standard error of estimate of the average annual runoff is about 30 percent. A statistical study of records from 62 stream-gaging stations and nearby first—order weather stations distrib- uted throughout the conterminous United States indi- cated that, of 9 meteorological factors tested, 5 were highly significant, 2 were moderately significant, and 2 showed only slight relation to annual runoff. Lack of US. Weather Bureau first—order weather stations near long-record streamflow stations limited the num- ber of stations available for study. The length of rec— ord at the 62 streamflow stations ranged from 11 years to 45 years and averaged 24 years. The size of the basins studied ranged from 8.5 square miles to 1,680 square miles and averaged 286 square miles. Stream— flow records were used as defined and were not combined or adjusted to a common base period. The meteorological records were from Weather Bu— reau reports entitled, “Climates of the States” (pub- lished for each State). The nine factors tested were: (1) average annual precipitation, (2) average annual temperature, (3) average snowfall, (4) average wind velocity, (5) average number of days with measurable precipitation, (6) average number of days with temper- atures of 90°F or more, (7) average heating degree days,1 (8) average relative humidity, and (9) percent of total possible sunshine. The factors of precipita- tion, temperature, and degree days were averages for the period 1921—50 as computed and published by the Weather Bureau. All other meteorological factors were averages for the full period of weather record. The 1 The value for heating degree days is determined by subtracting the average temperature for each day from 60°F and multiplying by the number of days. When the average temperature is above 60°F, no value is computed. weather data were considered representative of condi— tions over a Whole basin upstream from the nearby streamflow station. Because only annual averages are used, this assumption is probably valid. Of the 9 factors tested, 4 were statistically significant, at higher than the 99—percent level, in relation to an- nual runoff. One factor was statistically significant at the 95-percent level, and 2 more factors at the 80-percent level. The 2 remaining factors had significance levels below 60 percent. The equation determined from seven factors was as follows: R:150+0.42P*—2.23T*+0.08SS*—0.38WT +0.071DpI+0.054D,T-—0.008d, where R =average annual runoff, in inches, P=average annual precipitation, in inches, T =average annual temperature, in degrees F, S=average annual snowfall, in inches, W=average wind velocity, in miles per hour, Dp=average number ‘of days with measurable precipitation, Di =average number of days with temperature of 90° F or more, and d=average heating degree days. ' Statistically significant at greater than 99-percent level. ’rStatistically significant at greater than 80-percent level. tStatistically significant at greater than 95-percent level. The standard error of estimate from this relation was computed to be 30 percent. Of the 9 factors tested the 2 not included in the equation are average relative humidity and percent of total possible sunshine. By eliminating the two factors that were significant at the 80-percent level, the equation changes to: R=118+0.39P*— 1 .73T*+0.0888*+0.059D,T —0.007d,* where the terms are the same as before. The standard error of estimate from this relation was 31 percent. The effect of precipitation on runoff is self evident. The temperature is a measure of the potential evapo— transpiration, or losses in runofi. A better measure of U.S. GEOL. SURVEY PROF. PAPER 501-C, PAGES C188-CIS9 0188 BUSBY this would be solar radiation, since this is the source of energy for the evapotranspiration. However, because solar radiation is measured at only about 50 Weather Bureau stations throughout the country, temperature was used instead. The snowfall afi'ects runoff to the extent that it is an important part of total precipita— tion in many regions where most of the runoff is from snowmelt. The average wind velocity afi’ects runofl' as it affects the actual evapotranspiration. The average number of days with measurable precipitation, the aver- age number of days with 90°F temperature or more, and the average heating degree days are general cli- matic factors describing features such as the variability of the temperature, the intensity of rainfall, and the severity of the winters. Because runoff in inches expresses discharge as an average over the whole basin, drainage area is already in the relation. By substituting discharge and drain- age area for runoff, the first equation would become: (2 = 150 + 0.07411 + 0.42P — 2.23T + 0.0835 — 0.38W + 097le+ 0.054Dt — 0.008d, 0189 where Q =average annual discharge, in cubic feet per second, and A = drainage area, in square miles. The standard error of estimate is, of course, unknown. Experience, however, has shown that discharge and drainage area are not related arithmetically, but more nearly logarithmically. The meteorological factors will only explain part of the runoff relations. As soon as the water comes into physical contact with the land surface of the basin, the physical characteristics of the basin, such as drainage area, slope, drainage density, and geology, modify the runofi". A further study, therefore, should use annual runoff in cubic feet per second and introduce physical characteristics of the basin into the relation. Such a study might indicate which factors to consider when attempting to explain other discharge probabilities such as high or low flow. GEOLOGICAL SURVEY RESEARCH 1964 PHOTOGRAMMETRIC CONTOURING OF AREAS COVERED BY EVERGREEN FORESTS By JAMES HALLIDAY, Washington, DC. Abstract—New studies have been undertaken to establish the accuracy and elevational consistency of contouring by photogrammetric methods where dense evergreen stands of timber obscure the ground detail. By comparing compilations from several distinctive sets of aerial photographs for an area 3in northern Maine, the photographic conditions most conducive to accurate contouring in such areas were evaluated. Best results were obtained with a flight—height/contour-interval ratio of about 700, panchromatic film, and photography in early spring with light snow cover and no deciduous leaves. Obtain- ing accurate contours of the ground surface in such areas by applying corrective data to treetop contours proved unpromising. A perennial difficulty in topographic mapping by photogrammetric methods has been the problem of compiling planimetry (the plan details) and hypsog— raphy (topographic relief) in areas of dense evergreen timber with suflicient accuracy to meet National Map Accuracy Standards. The fundamental obstacle to accurate compilation is the dense evergreen foliage canopy which obstructs a clear view of the ground in all seasons. The latest Geological Survey research on the subject has been directed toward more exact determinations of the accuracy and consistency to be expected when con— touring areas of dense evergreen forests. Also, by compiling from aerial photographs representing vari- ous combinations of flight height, film emulsion, and prevailing seasonal conditions, it was anticipated that those photographic conditions most conducive to con- sistently accurate contouring in dense evergreens might be determined. In a supplementary study, a determi- nation was to be made of the consistency attained by a number of compilers when the upper surface of the evergreen canopy was contoured intentionally. This information was to be used to evaluate the desirability of further study to develop a method for contouring the ground surface beneath dense evergreens by apply- ing corrective data to treetop contours. A 6-square-mile area in the vicinity of Baker Lake in northern Maine was selected as typical of the ever- green—forested portions of that State. The terrain in this locality displays many of the topographic features common to areas of continental glaciation, including numerous swamps and ponds. The moderate relief consists of medium but occasionally irregular slopes. The area selected has 100-percent timber cover, pre- dominantly evergreen. The trees are 30 to 60 feet high. The accepted contour interval for US. Geological Sur- vey quadrangle mapping for this type of terrain is 20 feet. A test line was surveyed on the ground through the densest evergreen woods in the area. Accurate hori- zontal positions and elevations were obtained for more than 120 points along the line for use in evaluating the accuracy of contour compilations. The typically short flying season and the generally poor photographic weather in northern Maine added to the difficulty of obtaining photography under the de- sired conditions. Nevertheless, four sets of acceptable vertical, wide-angle photographs covering the general area were obtained. The distinguishing characteristics of these coverages are given in table 1. TABLE 1.—Characteristics of the photographic coverages of the Baker Lake area, Maine Fli ht Cover- height Deciduous Snow cover age above Type of film Season leaves on ground ground (feet) 1 _____ 7, 000 Panchro— Late Partial- __ None. matic. spring. 2 _____ 14, 000 Panchro- Late None- _ - _ None. matic. fall. 3 _____ 14, 000 Panchro- Early None- _ _ _ Light. matic. spring. 4 _____ 14, 000 Infrared__ Early None- _ - - Light. spring. PROC E DU R ES A group of 18 employees especially proficient in photogrammetric surveys was selected to produce the contour manuscripts required in this research. The selections were based on high levels of visual acuity, general ability, background, experience, and, most US. GEOL. SURVEY PROF. PAPER 501—C, PAGES Cl90-Cl93 0190 HALLIDAY important, a demonstrated competence with the Kelsh plotter, the instrument to be used in this study. The participants were furnished with identical compilation materials, including print copies (on Mylar stable bases) of the appropriate quadrangle manuscript, for which the aerotriangulation and compilation of planim- etry had been completed. Also furnished were elec- tronically dodged Kelsh diapositive plates, appropriate photographic prints annotated with the necessary pass- point and supplemental vertical control information, and lists of other pertinent basic horizontal- and verti- cal-control data. All information relating to the test line was purposely withheld from the participants be- fore and during contouring operations to prevent acci- dental misuse of the data. Each compiler was directed to contour the designated project area four times by using appropriate exposures from a different set of photographic coverage for each compilation. The stereomodels were oriented, adjusted in horizontal scale, positioned to provide a best fit between the pass points and the previously compiled planimetry, and leveled to a vertical datum determined 0191 by the supplemental elevations. Each compiler was instructed to use his customary procedures for contour- ing the ground surface in areas of dense evergreen timber. In addition, the compilers were directed to contour the upper surface of the foliage canopy for one designated model using coverage 1 (table 1), for use in the previously mentioned supplementary study. The ground-contour compilations were evaluated for accuracy by comparison with the test-line survey in accordance with standard Topographic Division prac- tice. To form a basis for evaluating the consistency of the contouring of the upper canopy surface, these compilations were compared with test—line data to determine apparent tree heights at the test points. Deviations from the mean apparent tree-height values at the various test points were then used to determine the consistency of such contouring among the several stereocompilers. RESULTS Table 2 lists the accuracy attained by the various compilers each time they contoured the ground surface beneath the dense evergreen trees. Results are given TABLE 2.——-Results of photogrammem'c ground contouring Coverage 1 Coverage 2 Coverage 3 Coverage 4 Average of all tests RMSE Percent RMSE Percent RMSE Percent RMSE Percent RMSE Percent Compiler (ft) passing (ft) passing (ft) passing (it) passing (it) passing Be- After Be- After Be- After Be- After Be- After Be- After Be- After Be- After Be- After Be- After fore shift fore shift fore shift fore shift fore shift fore shift fore shift fore shift fore shift fore shift shift shift shift shift shift shift shift shift shift shift 1 ......................... 11.6 9. 7 72 76 15. 3 12. 3 55 66 9. 3 7. 3 74 85 12. 610. 2 57 67 12.2 9. 9 65 74 2 _________________________ 10.0 7. 6 73 8110.9 8. 4 67 86 8. 6 6. 9 79 91 7. 6 5. 4 83 95 9. 3 7. 1 76 88 3 _________________________ 8. 9 6. 8 71 84 10. 6 8. 4 78 80 7. 0 5. 2 86 94 6. 5 4. 7 89 92 8. 3 6. 3 81 88 4 _________________________ 9. 2 7. 1 78 87 14. 7 12. 2 58 70 7. 6 5. 7 93 96 7. 6 5. 7 88 94 9. 8 7. 7 79 87 5 _________________________ 9. 1 6. 3 69 92 10. 7 8.0 72 76 8. 3 6. 4 77 88 9. 6 7. 5 76 88 9. 4 7. 1 74 86 6 _________________________ 7. 6 5. 4 80 93 10. 2 8. 4 77 84 6. 3 4. 5 90 96 8. 3 6. 1 80 89 8. 1 6. 1 82 91 7 _________________________ 14311.7 51 63 9. 4 6. 9 75 87 6.8 4 8 90 92 8. 6 6. 8 88 93 9. 8 7. 6 76 84 8 _________________________ 8. 7 6. 4 88 92 14. 7 12. 5 46 57 5. 2 3. 6 97 97 6. 1 4 2 94 97 8. 7 6. 7 81 86 9 _________________________ 9.4 6.6 72 91 8.4 6.2 78 87 5.4 3.4 96 97 5.8 3.9 91 96 7.3 5.0 84 93 10 ________________________ 25. 1 21. 7 29 4120. 817. 9 40 50 6. 8 4. 3 89 97 8. 5 5. 8 79 91 15. 312.4 59 70 11 ________________________ 17.7 14. 7 43 57 13. 5 10. 1 39 65 6. 2 3. 8 92 96 8.0 5. 1 78 9211.4 8. 4 63 78 12 ________________________ 17. 4 13. 8 42 53 14. 7 11. 6 48 61 7. 1 4. 5 89 97 8. 5 6. 1 79 83 11. 9 9. 0 65 74 13 ________________________ 19. 7 16. 0 23 35 14. 7 12. 1 51 65 8. 9 6. 1 85 90 8. 5 5. 8 82 90 13. 0 10. 0 60 70 14 ________________________ 11.5 8. 9 68 78 14912.1 49 61 9. 4 6. 4 81 91 10. 3 7. 9 71 7611. 5 8.8 67 77 15 ________________________ 11. 1 8. 8 67 87 8. 2 6. 0 84 94 9. 2 6. 7 80 93 7. 8 5. 0 90 94 9. 1 6. 6 80 92 16 ________________________ 8. 3 6. 1 74 89 6. 2 4. 3 91 98 5. 5 3. 9 95 96 6. 1 4.6 93 96 6. 5 4. 7 88 95 17 ________________________ 13. 2 9. 3 56 80 9. 4 7. 0 71 87 10.0 7.0 71 79 11. 7 9. 2 73 8011. 1 8.1 68 82 18 ________________________ 7. 3 5. 0 81 94 6. 9 4. 7 87 93 6. 3 3. 8 91 96 6. 5 4.0 90 98 6. 8 4. 4 87 95 Average ___________________ 12. 2 9. 6 63 76 11. 9 9. 4 65 76 7. 4 5. 2 86 93 8. 3 6. 0 82 90 10. 0 7. 6 74 84 No. of compilers meeting ver- tical accuracy standards--- -_-- ---- 0 5---_ _--_ 1 3_--_ _-_- 8 15 ___- ---- 5 12--__ _-_- _-_- ____ RMSE: root mean square error=\/Ee2/n, where e=vertical compilation error, at a point on the test—line survey, determined by comparing the elevation indicated by the ground contours with field-established elevation at that point. n=number of test-line points involved. Percent passing: percentage of points tested at which the vertical error does not exceed 10 feet (% contour interval). Before shift: value before allowable horizontal shift. After shift: value after allowable horizontal shift. 0192 in terms of root mean square error (RMSE) in feet, also in terms of the percentage of points tested at which the vertical error did not exceed 10 feet (one-half con- tour interval).1 The accuracy values for both presen- tations have been computed both with and without allowance for the horizontal shift permitted by Survey Order 160. Table 3 shows the consistency of contouring attained when the participating compilers attempted to contour the upper surface of the foliage canopy in accordance with the requirements of the supplementary study. The standard deviation values in this table have been com— puted on the basis of deviations from values of mean apparent tree height at the various test points. The allowable horizontal shift was not considered in this study, primarily because the necessary basic data were not readily available. TABLE 3.—Results of photogrammetric treetop contouring Number of Standard Percentage Compiler points tested deviation (ft) evaluation 1 __________________ 24 5. 8 83 2 __________________ 23 11. l 52 3 __________________ 26 11. 4 50 4 __________________ 26 6. 9 88 5 __________________ 26 6. 6 88 6 __________________ 26 5. 2 96 7 __________________ 26 5. 1 92 8 __________________ 26 5. 4 92 9 __________________ 26 14. 8 50 10 _________________ 21 4. 0 100 11 _________________ 21 10. 6 57 12 _________________ 21 5. 0 95 13 _________________ 21 5. 4 95 14 _________________ 21 5. 7 95 15 _________________ 21 5. 3 95 16 _________________ 26 5. 1 100 17 _________________ 26 6. l 88 18 _________________ 26 6. 6 92 Average values ________________ 7. 0 84 Standard deviation=v 2(Hi— Hm)2/(n— 1), where Hi=apparent height of trees at a point on the test-line survey determined by comparison of the elevation indicated by treetop contours with field-established ground elevation at that point. Hm=mean apparent height of trees at a point on the test- line survey determined by averaging all Hi data at that point. n=number of test-line points involved. Percentage evaluations are given in terms of the percentage of points tested at which the deviations from the mean apparent tree height value do not exceed 10 feet 04 contour interval). 1 For a map to comply with National Map Accuracy Standards, Survey Order 160 requires that “vertical accuracy, as applied to contour maps . on all publication scales, shall be such that not more than 10 percent of the elevations tested shall be in error by more than one—half the contour interval. In checking elevations taken from the map, the apparent vertical error may be decreased by assuming a horizontal displacement within the permissible horizontal error for a map of that scale.” PHOTOGRAMMETRY CONCLUSIONS The accuracy and consistency of ground contouring varied through a considerable range, depending pri- marily on the characteristics of the aerial photographs that were used. Of the combinations studied, the pho- tographic conditions that appear to be most conducive to consistently accurate ground contouring in dense evergreen woods in Maine are thOSe found in coverage 3. They include: a flight-height/contour-interval ratio (C-factor) of about 700, panchromatic film, early spring photographic season, no leaves on deciduous trees in the area, and a light snow cover on the ground. Of partic- ular significance in this respect was the finding that a considerably lower flight height (represented in cover- age 1) did not result in improved contouring accuracy or consistency for the dense evergreen—forested condi- tions under study. This is contrary to general photo- grammetric experience. The ground-contouring results attained with coverage 3 displayed surprisingly excellent accuracy and con- sistency; 2 however, further research is needed to find ways and means of improving this record. Studies should be aimed at providing the stereocompiler with more and better ground information, so that photo- graphs obtained under less than the ideal conditions outlined above may be used to produce maps of stand— ard quality. The stereocompiler would be aided by (1) more precisely photoidentified, more accurately located pass points, (2) more accurate supplemental eleva- tions for model control, (3) additional elevations on controlling topographic features, such as tops, saddles, and drain forks, within the stereomodels, and (4) mul— tiple photographic coverage aimed at most advantage- ous recording of specific types of ground detail. Further exploration of the potentials of infrared photography and infrared electronic sensors for map- ping in this type of country appears to be warranted because of the good quality of the ground contouring results attained with coverage 4,3 and the recognized usefulness of infrared coverage in the detection and delineation of the more obscure hydrographic details. The contouring of the upper surface of the evergreen canopy was remarkably consistent; 4 however, serious 2 After the allowable horizontal shift, 15 of the 18 compilations met standard accuracy requirements, while another fell just short, at 88 percent. See table 2. 3After the allowable horizontal shift, 12 of the 18 compilations met standard accuracy requirements, while 2 more fell just short, at 89 and 88 percent. See table 2. 4 In 10 of the 18 compilations the contours werevwithin 10 feet (one- half contour interval) of the mean compiled values at 90 percent or more of the points tested. See table 3. HALLIDAY obstacles bar the way to successful development of ground contours by the method of applying corrective data to treetop contours. Because tree heights vary with microclimatology in different parts of the terrain and important topographic details are very often ob— scured by the canopy, the tree-canopy surface is at best only a generalized representation of the ground surface 0193 beneath. Also, despite the commendable consistency of the contouring, significant differences were noted in the contour shaping in the various compilations. For these reasons, treetop contouring could not be properly transformed into an acceptable ground-contour pres- entation Without considerable additional effort and expense. SUBJECT INDEX [For major headings such as “Economic geology,” “Geophysics," “Structural geology," see under State names or refer to table of contents] ABS. contaminant of ground water, New York ............................. Alaska, copper deposit, south-central part...- laumontite, western part ____________ Analcime, potential deposits, California ...... Analysts, chemical, rating of ability .......... Apache Group, Arizona, stratigraphy.-.. Arizona, paleontology, Grand Canyon area--. stratigraphy, Grand Canyon area.. . south-central part .................... Artesian aquifers, Florida-Georgia, efl'ect on surface water ..................... Attapulgite, in cave flll, New Mexico... Basement rocks, New J etsey, petrography.... Beryllium, association with lithium in tufl, Utah ............................. Bolsa Quartzite, Arizona, stratigraphy ________ C Calcite-rhodochrosite-magnesite system, dia- gram ............................. California, potential zeolite deposits, MojAve Desert ............................ structural geology, northwestern part. Cambrian, Arizona, Stratigraphy ............. Maine, stratigraphy ...................... structural geology .................... Cationic diffusion rate, of montmorillonite, measurement ..................... Catoctin Formation, Virginia, petrology ...... Cave filling, clay content ..................... Cavities (tafoni), in bedrock, northern Chile-_ Channel deposits, Devonian, Montana ....... Chattanooga Shale, Tennessee—Kentucky, geochemistry ..................... Chemical quality, ground water, relation to recharge .......................... Chemists, analytical, rating of ability--. Chi-square method, use in rating chemists.. Chile, geomorphology, northern part ......... Clay, effect on subsidence, Texas ............. in cave filling, New Mexico ............... Clay minerals, montmorillonitic, cationic diffusion and exchange rates ...... occurrence in Pleistocene sediments, Texas ............................ Clinoptilolite, potential deposits, California.- Colorado, petrology, west-central part ........ Connecticut, petrology, east-central part ...... Contouring, photograrnmetric, oi evergreen- forest areas ....................... Copper, abundance in alluvium, North Carolina .......................... Copper deposits, ore controls , Alaska ......... Corals, Mississippian, Arizona .......... .. Cretaceous, Alaska, occurrence of laumontite. South Carolina, ground water ............ Detergents, contaminants of ground water, New York ________________________ Page 0170 117 74 114 164 82 55 43 176 157 157 121 79 82 96 79 114 16 22 190 88 117 39 74 180 170 Devonian, Maine, stratigraphy ............... Maine, structural geology ....... .. Montana, stratigraphy ................... Disaggregation, sedimentary samples, ultra- sonic method ..................... Discharge, stream, estimation from precipita- tion records ....................... Dripping Spring Quartzite, Arizona, stratig- raphy ............................. Earthquakes, island of Hawaii, Kilauea rift zone.--. Eocene, Florida-Georgia, ground water._ .- Georgia, paleontology .................... stratigraphy .......................... Erionite, potential deposits, California ........ Exchange rate, of montmorillonite, measure- ment ............................. F Faults, strike-slip, Idaho-Montana ........... tear, west-central Utah .............. .-- Fischer assay, use in study of weathering of shale .............................. Fish fossils. Devonian, Montana ............. Florida, ground water, Statewide artesian aquifer ........................... surface water, efieet of artesian aquifer on- Floridan aquifer, FloridarGeorgia, efiect on surface water ..................... Foraminifera, Eocene, Georgia ................ Fractures, explosion-produced, structural analysis . . . . G Gabbro, intrusive body, Connecticut ......... Geochemical prospecting, metals, North Carolina .......................... Georgia, ground water, southern part ......... paleontology, eastern part ................ stratigraphy, Savannah area. surface water, southern part ______________ Glacial deposits. See Moraines. Glaciers, retreat of Teton Glacier, Wyoming.. Greenstone, chemical composition, Virginia - - H HARDHAT event, Nevada, study of explosion- produced fractures ................ Hawaii, geophysics, island of Hawaii _________ Idaho, structural geology, east-central part. ..- Illinois, sedimentation, southern part ......... Iodine, method of determination invegetation. J Jordan Sandstone, Minnesota, ground water.- Page C28 28 50 159 185 43 14 19 92 50 164 164 164 64 100 103 14 130 154 176 K Page Kentucky, geochemistry, southern part ______ 092 sedimentation, western part ........ 130 Kilauea volcano, seismicity of east rift zone--. 103 L Laccoliths, Colorado, post-Paleocene ......... 66 Lake deposits, Pleistocene, Kentucky-Illinois- 130 Laumon tite, occurrence and origin, in Alaska.- 74 Lithium, association with beryllium, in tufl.. 86 M Magneslte-calcite—rhodochrosite system, dia- gram ............................. 84 Maine, stratigraphy, northeaStern part- . 28 structural geology, northeastern part ..... 28 Massachusetts, glacial geology, Martha’s Vineyard ...................... 134, 140 Maywood Formation, Montana, stratigraphy. 50 Mesoal Limestone, Arizona, stratigraphy ..... 43 Mesozoic, California, structural geology ...... 1 Nevada, structural geology --------------- 10 See also Cretaceous. Meterological factors, effect on runoff ......... 188 Michigan, glacial geology, Upper Peninsula-- 126 Minnesota, glacial geology, Mesabi iron range- 144 ground water, Minneapolis—St. Paul area.- 176 Miocene, Florida-Georgia, ground water. ...._ 164 Georgia, stratigraphy ..................... 61 Mississippian, Arizona, stratigraphy. _ . . .-_-. 39 Montana, paleontology, southwestern part... 50 stratigraphy. southwestern part .......... 50 structural geology, western part ---------- 14 Montmorillonite, cationic diffusion and ex- change rates ...................... 96 Moralnes, lllinoian and Wisconsin age, Massachusetts .................... 140 Wisconsin age, Michigan ................. 126 N Nevada, structural geology, Nevada Test Site. 100 structural geology, northwestern part ..... 10 Nevada Test Site, study of explosion-produced fractures .......................... 100 New Jersey, petrography, coastal plain ------- 55 New Mexico, ground water, southeastern part- 161 mineralogy, Carlsbad Caverns. ---------- 82 New York, ground water, Long Island ....... 170 Nickel, abundance in alluvium, North Carolina. - ........................ 88 North Carolina, geochemistry, south—central part .............................. 88 Nuclear explosions, cause of rock fractures.-.. 100 O Oligocene, Florida-Georgia, ground water--_- 164 Georgia, stratigraphy.: ............ 61 Ordovician, Maine, stratigraphy. . 28 Maine. structural geology ..... 28 Ore controls, copper deposit, Alaska .......... 117 0195 0196 Page Oregon, structural geology, southwestern part. Cl Oxygen sheath, for flame photometer. new design ............................ 152 P Paleogeography, relation of phosphorite distri- bution to _________________________ 106 Paleomagnetism, relation of phosphorite distri- bution to ......................... 106 Paleozoic, California, structural geology ______ 1 South Carolina, ground water ____________ 180 See also Cambrian, Ordovician, Silurian, Devonian, Mississippian. Particle-size analyses, use of ultrasonic disag- gregation ......................... 159 Phosphorite, paleolatitudinal and paleogeo— graphic distribution ______________ 106 Photogrammetric contouring, evergreen-forest areas _____________________________ 190 Photometer, flame, new oxygen sheath _______ 152 Pioneer Formation, Arizona, stratigraphy. .._ 43 Pleistocene, Georgia, stratigraphy ______ . 61 Kentucky-Illinois, sedimentation. . 130 Massachusetts, glacial geology.. 134, 140 Michigan, glacial geology _________________ 126 Minnesota, glacial geology ________________ 144 Texas, clay mineralogy ......... . 79 Precambrian, Arizona, stratigraphy 43 South Carolina, ground water. . .- 180 Virginia, petrography ____________ 69 Precipitation records use in estimating stream discharge _________________________ 185 Q Quaternary, South Carolina. ground water.. 180 See also Pleistocene. SUBJECT INDEX R Page Radioactive waste, storage, possible effect on ground water ..................... 0180 Recharge, ground water, eflect on chemical quality-.. .._ _____________ 176 Redwall Limestone, Arizona, stratigraphy.... 39 Regression models, use in estimating stream discharge _________________________ 185 Rhodochrosite-magnesite—calcite system, dia- gram _____________________________ 84 Runofl, relation to meteorological factors ______ 188 5 Seismic studies, island of Hawaii ............. 103 Silurian, Maine, stratigraphy ................. 28 structural geology ........................ 28 South Carolina, ground water, Savannah River Plant ...................... 180 Stream capture, Recent, Michigan ........... 126 Streamflow, estimated from precipitation records ........................... 185 relation to meteorological factors. 188 Subsidence, Texas, effect of clay on ___________ 79 T Tafoni (cavities), in bedrock, northern Chile- 121 Tennessee, geochemistry, northern part _______ 92 surface Water, Western part _______________ 185 Tertiary, California, potential zeolite deposits. 114 Colorado, petrology ...................... 66 South Carolina, ground water ............ 180 See also Eocene, Oligocene, Miocene. Page Texas, clay mineralogy, Houston-Galveston Bay area ............... .._ C79 Thrust sheets, Mesozoic age, Califorma and Oregon ........................... 1 Topographic maps, contouring, evergreen- iorest areas ....................... 190 Tritium, as indicator of age and movement of ground water ..................... 161 U Ultramafic rocks, California and Oregon, structural geology ................ l Ultrasonic disaggregation, sedimentary samples .......................... 159 Utah, geochemistry, J uab County ...... .._ 86 potential base-metal and silver deposits, west—central part ............. 19 structural geology, west—central part ..... 19 V Vegetation, determination of iodine content. . 154 Virginia, petrography, Blue Ridge area ....... 69 W Weathering, formation of tafoni, in bedrock... 121 of shale, evaluation by Fischer assay ...... 92 Wyoming, glaciology, Grand Teton Park _____ 147 Z Zeolite deposits, in tufiaeeous rocks, California . 114 Zinc, abundance in alluvium, North Carolina. 88 B Page Boucot, A. J ................................ 028 Breger, I. A... _____________ 92 Brown, Andrew__ 92 Brown, '1‘. E... 96 Busby, M. W .............................. 188 C Condon, W. H ............................. 74 Corliss, J. B.. _________ 79 Cotter, R. D .............. 144 Cuthbert, Margaret ........................ 154 D Davies, W. E .............................. 82 Dinnm, J. I ................................ 152 Duke, Walter. _____________________________ 86 E Emerlck, W. L ............................. 100 F Finch, W. I ................................ 130 Flanagan, F. J ............................. 157 Frauenthal, H. L ........................... 170 G Gasklll, D. L ............................... 66 Godwin, L. E.. 66 Gude, A. J., 3d ............................. 114 H Halllday, J ames ............................ 190 Helnd], L. A..-..-. 43 Henriquez, Hugo ___________________________ 121 AUTHOR INDEX Page Herrick, S. M ____________________________ 061,64 Hoare, J. M.- 74 Houser, F. N _______________________________ 100 I Irwin, W. P ................................ 1 J Johnson, A. I ............................... 159 K Kane, M. F.. -._ 22 Kaye, C. A ..... ___ 134,140 Koyanagi, R. Y ............................ 103 L Lleber, Maxim _____________________________ 170 M McClymonds, N. E ........................ 43 McCollum, M. J-..-.. 61 McHugh, J. B .............................. 88 MacKevett, E. M., Jr... ................... 117 McMannls, W J ............................. 50 Maderak, M. L .............................. 170 May, Irving .................................. 152 Meade, R. H ................................. 79 Mencher, Ely ................................ 28 Morris, H. T ................................. 19 Moston, R. P ................................ 159 Mountjoy, Wayne ............................ 86 N Naylor, R. S ................................. 28 O O Page Ollve, W. W ................................. 0130 P - Patton, W. W., Jr ............................ 74 Pavlldes, Louis.... 28 Perlmutter, N. M ............................ 170 Prinz, W. C __________________________________ 84 R Reed, J. 0., Jr _______________________________ 69,147 Reader, H. 0.. ......................... 161 Riggs, H. C... ..................... 185 Rogers, J. E.. .................. 144 Rosenbsum, Fred- . 152 Ruppel, E. T _________________________________ 14 S Sandbag, C. A ............................... 50 Sando, W. J .................................. 39 Segerstrom, Kenneth ....................... 121, 126 Shawe, D. R ................................. 86 Sheldon, R. P-.. ....................... 106 Shepard, W. M...- ..................... 19 Sheppard, R. A. ..................... 114 Sllberllng, N. J .. ................. 10 Siple, G. E.- ................. 180 Snyder, G. L.. ............. 22 Southwick, D. L ...... . 55 Stringfleld, V. T ...... . 164 Stromqulst, A. A ............................. 88 W Wallace, R. E ........ 10 Ward, F. N .................................. 154 White, A. M ................................. 88 Wolfe, E. W ................................. 130 0197 SHORT PAPERS IN— (Analytical techniques L 7. Fartography [Economic geology gineering geology p Geochemical exploration .vi {Geochemistry Geomorphology Geophysics Glacial geology Ground water ~ Marine geology Mineralogy Ore deposits ? Paleontology l , Petrology l iduality of water I V" l l" Sedimentation ‘_~ Stratigraphy ’4 l . Structural geology k V LSurface water > l 5 Theoretical hydrology @575 #106?!" flé /. 6'0/ ’3 GEOLOGICAL SURVEY RESEARCH 1964 Chapter D GEOLOGICAL SURVEY PROFESSIONAL PAPER 50i—D GEOLOGICAL SURVEY RESEARCH I 964 Chapter D GEOLOGICAL SURVEY PROFFESSIONAL PAPER SOI—D Scientific notes and summaries of investiga- tions prepared by members of the Geologic, Conservation, Water Resources, and Topo- graphic Divisions in geology, hydrology, topographic mapping, and related fields UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: I964 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For saIe by the Superintendent of Documents, US. Government Printing Office, Washington, D. C., 20402 FOREWORD This collection of 43 short papers is the last of the chapters of Geological Survey Re- search 1964. The papers report on scientific and economic results of current work by members of the Geologic, Conservation, Water Resources, and Topographic Divisions of the US. Geological Survey. Some of the papers present results of completed parts of continuing investigations; others announce new discoveries or preliminary results of investigations that will be discussed in greater detail in reports to be published in the future. Still others are scientific notes of limited scope, and short papers on techniques and instrumentation. Chapter A of this series presents a summary of results of work done during the present fiscal year. THOMAS B. NOLAN, Director. III CONTENTS Page Foreword ___________________________________________________________________________________ III 1 GEOLOGIC STUDIES Mineralogy and petrology Temperatures in the crust and melt of Alae lava lake, Hawaii, after the August 1963 eruption of Kilauea Volcano—a. pre- liminary report, by D. L. Peck, J. G. Moore, and George Kojima ______________________________________________ D1 Variation in modes and norms of an “homogeneous” pluton of the Boulder batholith, Montana, by R. I. Tilling ________ 8 Mafic lavas of Dome Mountain, Timber Mountain caldera, southern Nevada, by S. J. Luft _________________________ 14 Structural geology Preliminary report on the structure of the southeast Gros Ventre Mountains, Wyoming, by W. R. Keefer _____________ 22 Pre-Fall River folding in the southern part of the Black Hills, South Dakota, by G. B. Gott ________________________ 28 Stratigraphy and paleontology Chinle Formation and Glen Canyon Sandstone in north astern Utah and northwestern Colorado, by F. G. Poole and J. H. Stewart ________________________________________________________________________________________________ 30 Significance of Triassic ostracodes from Alaska and Ne ada, by I. G. Sohn _______________________________________ 40 Middle Devonian plant fossils from northern Maine, b J. M. Schopf ____________________________________________ 43 Geochronology Radiometric ages of zircon and biotite in quartz diorite,lEights Coast, Antarctica, by A. A. Drake, Jr., T. W. Stern, and H. H. Thomas ___________________________________________________________________________________________ 50 Geochemistry l Qualitative X-ray emission analysis studies of enrichment of common elements in wallrock alteration in the Upper Missis- sippi Valley zinc-lead district, by J. W. Hosterman, . V. Heyl, and J. L. Jolly __________________________________ 54 Suggested exploration target in west-central Maine, by . C. Canney and E. V. Post _______________________________ 61 Geophysics . Radioactivity- and density-measuring devices for oceandgraphic studies, by C. M. Bunker __________________________ 65 Aeromagnetic interpretation of the Globe-Miami copper district, Gila and Final Counties, Arizona, by Anna Jespersen- _ 70 Economic geology ‘ Epigenetic uranium deposits in sandstone, by W. I. Fin h _______________________________________________________ 76 The occurrence of phosphate rock in California, by H. . Gower and B. M. Madsen _______________________________ 79 The distribution and quality of oil shale in the Green iver Formation of the Uinta Basin, Utah-Colorado, by W. B. Cashion ________________________________________________________________________________________________ 86 Btu values of Fruitland Formation coal deposits in Colori+do and New Mexico, as determined from rotary-drill cuttings, by J. S. Hinds ______________________________________________________________________________________________ 90 Marine geology Giant submarine landslides on the Hawaiian Ridge, by J. G. Moore ______________________________________________ 95 Engineering geology A zone of montmorillonitic weathered clay in Pleistocerle deposits at Seattle, Washington, by D. R. Mullilneaux, T. C. Nichols, and R. A. Speirer_______________________T _______________________________________________________ 99 , Quaternary geology and glaciology Three pre—Bull Lake tills in the Wind River Mountains, Wyoming—a reinterpretation, by G. M. Richmond ___________ 104 Post-hypsithermal glacier advances at Mount Rainier, Washington, by D. R. Crandell and R. D. Miller ______________ 110 Sedimentation Occurrence of dissolved solids in surface waters in the United States, by W. B. Langbein and D. R. Dawdy ___________ 115 Statistical parameters of Cape Cod beach and eolian sands, by John Schlee, Elazar Uchupi, and J. V. A. Trumbull _____ 118 V VI CONTENTS Analytical techniques An instrumental technique for the determination of submicrogram concentrations of mercury in soils, rocks, and gas, by W. W. Vaughn and J. H. McCarthy, Jr ____________________________________________________________________ Determination of mercury in vegetation with dithizone—a single extraction procedure, by F. N. Ward and J. B. McHugh__ Ion-exchange separation of tin from silicate rocks, by Claude Huffman, Jr., and A. J. Bartel __________________________ Determination of carbonate, bicarbonate, and total 002 in carbonate brines, byS. L. Rettig and B. F. Jones ______________ TOPOGRAPHIC MAPPING Cartography Mapmaking applications of orthophotography, by M. B. Scher __________________________________________________ HYDROLOGIC STUDIES Ground water Ground-water conduits in the Ashland Mica Schist, northern Georgia, by C. W. Sever _______________________________ Temperature and chemical quality of water from a well drilled through permafrost near Bethe], Alaska, by A. J. Feulner and R. G. Schupp__ __________________-________-____-__________; _________________________________________ Hydrogeologic reconnaissance of the Republic of Korea, by W. W. Doyel and R. J. Dingman __________________________ Source of heat in a deep artesian aquifer, Bahia Blanca, Argentina, by S. L. Schoff, J. H. Salso, and José Garcia __________ The Carrizo Sand, 9. potential aquifer in south-central Arkansas, by R. L. Hosman __________________________________ Geohydrology of the Spiritwood aquifer, Stutsman and Barnes Counties, North Dakota, by T. E. Kelly ________________ Variation of permeability in the Tensleep Sandstone in the Bighorn Basin, Wyoming, as interpreted from core analyses and geophysical logs, by J. D. Bredehoeft _________________________________________________________________ Ground-water—surface-water relations Uniformity of discharge of Muddy River Springs, southeastern Nevada, and relation to interbasin movement of ground water, by T. E. Eakin and D. 0. Moore _____________________________________________________________________ Geologic factors affecting discharge of the Sheyenne River in southeastern North Dakota, by Q. F, Paulson _____________ Surface water Magnitude and frequency of storm runofl’ in southeastern Louisiana and southwestern Mississippi, by V. B. Sauer ________ Correlation and analysis of water-temperature data for Oregon streams, by A. M. Moore _____________________________ Engineering hydrol‘ogy Elimination of thermal stratification by an air—bubbling technique in Lake Wohlford, Calif., by G. E. Koberg ____________ Theoretical hydrology Field methods for determining vertical permeability and aquifer anisotropy, by E. P. Weeks __________________________ Two-variable linear correlation analyses of water—level fluctuations in artesian wells in Florida, by H. G. Healy __________ Hydrologic instrumentation A periscope for the study of borehole walls, and its use in ground-water studies in Niagara County, N.Y., by F. W. Trainer and J. E. Eddy __________________________________________________________________________________________ INDEXES Subiect ______________________________________________________________________________________________________ Author ______________________________________________________________________________________________________ Page D123 128 131 134 138 141 144 149 153 158 161 166 171 177 182 185 190 193 199 203 207 209 GEOLOGICAL SURVEY RESEARCH 1964 TEMPERATURES IN THE CRUST AND MELT OF ALAE LAVA LAKE, HAWAII, AFTER THE AUGUST 1963 ERUPTION OF KILAUEA VOLCANO—A PRELIMINARY REPORT By DALLAS L. PECK,1 JAMES G, MOORE,2 and GEORGE KOJIMA,1 lHawaiian VoIcano Observatory, Hawaii, 2 Menlo Park, Calif. Abstract—The August 1963 eruption of Kilauea Volcano pro- duced a lake of basaltic lava as much as 50 feet deep in Alae pit crater. Repeated drilling and temperature measurements in the crust and underlying melt of the lake during a 6-month period beginning 6 days after the eruption have identified the base of the crust as the 1,067°C isotherm and have followed the growth of the crust as it increased from 3.4 to 19 feet in thickness. An eruption of Kilauea Volcano in August 1963 created a pond of lava in the bottom of Alae pit crater, Hawaii (fig. 1). The lava contains rare olivine pheno- crysts and has the composition of silica-saturated tholeiitic basalt. On August 28, five days after the end of the eruption, an aerial tram was completed for lowering equipment and water into the crater, and on 155°10’ l Kilauea i“. K Caldera 1 9 a O bservatory 25’ Alae Crater Makaopuhi Crater Area of report Area at Iigure 2 /_ 50 w“ HAWAII I I 2 MILES 0 2 KILOMETERS L4_L_4 CONTOUR lNTFRVAl. 250 FEET FIGURE l.—Index map of the summit and the upper east rift zone of Kilauea Volcano, Hawaii. Boundaries of craters and Kilauea caldera are shown by heavy lines. the following day a hole (DH 1 of fig. 2) was drilled 34 inches into the crust of the lake, an estimated 3 inches less than the thickness of the crust. During the following 6 months the drill hole was extended in the thickening crust, and 4 other holes were drilled (see accompanying table). The base of the crust was pene- trated 6 times between September 6 and November 27. On December 3 a ceramic probe 71/2 feet long was pushed into the underlying melt. Temperature gradi- ents were measured on 27 days during the 6 months following the eruption. The temperature measurements of the cooling lava lake are part of a continuing program of study that includes continuous recording of rainfall at the rim of the crater, detailed mapping, leveling, and mag- netic studies of the lake, and chemical, petrographic, and density studies of drill core and of selected samples from the crust. Alae lava lake offers an excellent op- portunity to supplement the data on cooling of basaltic lava in the nearby Kilauea Iki lava lake formed in 1959. The absence of continuing eruptions, the availa- bility of equipment, and the experience gained from Kilauea Iki allowed us to obtain temperature data in a shorter time after the eruption of Alae Crater. Moreover the shallower depth of the lake will result in complete solidification of the lava in a much shorter period of time, about 1 year for Alae compared with more than 50 years for Kilauea Iki. We gratefully acknowledge the assistance and ad- vice of Drs. T. Minakami and Shigeo Aramaki of the University of Tokyo, and of the staff of the Hawaiian Volcano Observatory, in the study described in this paper. U.S. GEOL. SURVEY PROF. PAPER 501-1). PAGES D1—D7 D1 D2 Base modlfled from USGS 1:24,000 Keauhou quadrangle (1963) 0 200 400 FEET o 50 100 METERS L_;l CONTOUR INTERVAL 100 FEET FIGURE 2.—Map of Alae Crater, showing distribution of volcanic rocks from the August 1963 eruption, and location of num- bered drill holes (DH 1 to 5) in the crust of Alae lava lake. Lava lake, coarse stipple; spatter, thin flows, and pumice, fine stipple. Eruptive vents are shown by heavy lines and dots. Location of crater is shown on figure 1. THE ERUPTION On August 21—23, 1963, a small but spectacular flank eruption occurred in and near Alae Crater, a small pit crater on the upper east rift zone of Kilauea Vol- cano. Alae Crater is 34 of a mile east of Aloi Cra- ter, the site of the December 1962 eruption, and 5 miles southeast of the summit caldera (fig. 1). The eruption was preceded by three epochs of subsurface magma migration (on May 9, July 1, and August 3) that were marked by seismic activity, detumescence of the summit, and tumescence and surface cracking along the upper east rift zone. The first indication of the impending eruption, however, was the onset at 13‘46‘n 1 August 21 of nearly continuous earthquakes and tremors that recorded stronger on a seismograph near the Makaopuhi Crater than on seismographs near Kilauea Caldera. At 13h50m, displacement of the Press-Ewing instruments in the Uwekahuna vault near the Hawaiian Volcano Observatory indicated the be- ginning of a distinct southeastward tilt (detumescence 1 All times given are in hours and minutes, Hawaiian standard time. lVIINERALOGY AND PETROLOGY Drilling data in Alae lava lake Drill-hole Depth of interval No. 1% drilled (feel) M’ 1963: Aug. 29 _____ 1 1 0 — 2. 83 Sept. 3 _____ 1 2. 67— 3. 75 Sept. 6 _____ 1 3. 62- 4. 6 To base of crust. 2 2 0 — 2. 15 Do. Sept. 17_-__ 1 4. 2 — 5. 58 Do. Oct. 1-2_-__ 3 3 0 — 9. 33 Do. 0012. 24 _____ 3 7. 80—11. 40 Do. Nov. 7 _____ 3 9. 9 ~13. 35 Do. Nov. 20-- -- 4 4 0 —15. 8 D0. Nov. 27- --_ 4 11. 3 —15. 3 Do. Dec. 16 _____ 5 5 0 —29. 2 To near base of lake. 1964: Jan. 29 _____ 5 17. 5 —21. 0 Plug of ooze. 1 Near the major axis of the lava lake on the opposite side from the vents, 165 feet S. 44° E. of the center of the lake (fig. 2). 2 16 feet N. 75° E. of drill hole 1. 3 20 feet S. 15° E. of drill hole 1. 4 1 foot N. 75° E. of drill hole 3. 5 305 feet S. 49° E. of drill hole 1. of the summit region). Earthquake and tremor died to a low level after 15"00'“, but at 18‘100m they began to increase again. The eruption was first observed between 181115“1 and- 18“30m by an employee of the National Park Service; at that time an en echelon line of active lava fountains extended for 0.3 mile across the floor and north wall of Alae Crater and in the forest on the north rim. At 1920‘“, when scientists of the Hawaiian Volcano Observatory arrived at the crater, the fountains on the floor formed an almost continuous curtain 20 to 30 feet high and 265 feet long (long eruptive vent, fig. 2). Lava from 11 vents on the north wall cascaded down the clifl‘ and plunged beneath the surface of the grOW* ing lava lake, the dark crust of which was broken by glowing cracks that splayed outward from the curtain of fire and the base of the lava cascades. Maximum temperature measurements of the fountains, using 2 optical pyrometers of incandescent filament type, ranged from 1,090°C to 1,100°C. The line of foun- tains in the forest on the north rim died by 191145”, after sending thin flows of Shelly pahoehoe over an area of about 8,000 square yards. During the night, activity on the north wall con- solidated into two main fountains, the length of the curtain of fire on the floor shortened to 125 feet, and the rate of extrusion decreased from 150x103 cubic yards an hour at 201‘00m August 21 to 35X103 cu yd an hour at 03h00In August 22. Comparison of photo— graphs of the lake taken at 10—minute intervals between 01‘140m and 0210'“, August 22, show that the crust of the lake was being rafted outward on lava flowing from the vents at a rate of about 600 feet an hour, to be piled in a narrow slabby levee at the edge of the far end of the lake. By 061100“1 the lava lake had PECK, MOORE, reached its maximum thickness (about 62 feet) ; there- after it slowly subsided at a rate of 5X103 cu yd an hour. The vents on the floor of the crater began to fountain erratically, spewing bursts of spatter to heights of 20 to 150 feet. The two remaining foun- tains on the north wall were spattering weakly and sending two sluggish rivers of aa down to a low delta on the lake. The eruption continued at a diminished rate dur- ing daytime of August 22. At 18h30m, a party of ob- servers reached the edge of the lava lake and found that it was impounded by a slabby levee that stood 15 to 20 feet above the adjacent talus at the foot of the crater walls. At this time the surface of the lake was broken by widely spaced, glowing, radial and trans- verse cracks. At 21h20‘“, optical-pyrometer measure- ments of the fountains gave maximum temperatures of 1,130°C to 1,140°C. During the evening the glow- ing cracks began to darken, beginning at the end of the lake farthest from the vents, and by 00‘103m August 23, the lake was dark except for scattered spots. The fountains became progressively fewer in number and less active, and by 07"00‘“ only one small fountain about 10 feet in diameter was bubbling at intervals of 5 to 7 seconds. The surface of the lake near the foun- tain appeared to have sunk several feet as the result of drainback into the vent. All activity at the foun- tain stopped at 08h10m, and the eruption was over. On August 24, vertical—angle transit sights from the rim of the crater showed that drainback and degassing had lowered the surface of the lava lake about 10 feet since 19h00m August 22, leaving about 800x103 cu yd of lava in the lake, and 30X103 cu yd in the spatter cones and in the flows in the forest on the north rim. The lava lake formed by the eruption in Alae Crater is a lens 1,000 feet long, 800 feet wide, and as much as 50 feet deep, covered and bordered on the northwest side by a low spatter ridge that continues as coalescing spatter cones on the north wall of the crater. A 100— foot wide levee of discontinuous pressure ridges and uptilted slabs borders all but the northwest end of the lake, and is bounded for most of its length by a moat 10 to 15 feet deep and 50 to 100 feet wide (fig. 2). The lake within the levee has a hummocky surface that slopes almost imperceptibly toward the vent. Sharp pressure ridges and linear squeezeups that stand as much as 3 feet above the lake surface trace the position of glowing cracks during the later phase of the erup- tion, and a row of blocky pressure domes 5 to 10 feet high cross the northern side of the lake. Jagged ten— sion cracks, formed during drainback of lava near the end of the eruption, radiate outward from the center AND KOJIMA D3 of the lake. Secondary contraction cracks are growing in the intervening areas as the crust thickens and cools. TEM PERATU RE DATA Temperature measurements were made with thermo— couples of chromel-alumel and platinum—platinum plus 10 percent rhodium, using a portable millivolt poten— tiometer and a 0°C reference junction in an ice-filled vacuum bottle. Holes in the solidified lava were drilled with tungsten carbide bits in a portable 11/8- inch diameter core drill powered by a 9—horsepower gasoline engine. The drilling in August and Septem— ber was done by holding the drill and pouring cooling water into the hole by hand. After the first of October the drill was mounted on a portable mast anchored in the crust, and cooling water was pumped through the drill pipe by a Sig-hp gasoline engine. The coolant water drastically lowered the tempera- tures in the drill holes, particularly in those drilled after October 1, when 150 to 200 gallons of water were used in each operation. In each of the 5 drilling op- erations of October and November, the base of the crust was depressed 1.7 5 to 3.2 feet. Temperatures in the lower part of the crust recovered to near pre- drilling levels within a few days, but those in the upper part required many weeks; as much as 32 days after the November 27 drilling, the 300°C isotherm was still rising. Three temperature profiles are shown on figure 3: one measured August 30, 7 days after the end of the eruption; another measured December 30, 129 days after the eruption; and a third, which includes the highest temperature measured in Alae and Kilauea Iki lava lakes, measured November 5 and 8. During the 6 months following the eruption, the solid crust of Alae lava lake at the main drilling site increased in thickness from 1 to 19 feet. Temperatures in the lake measured during this period ranged from 45°C at the surface on December 30, to 1,135°C at a depth of 18 feet in molten lava 7.6 feet below the base of the crust on November 8. Extrapolation from this value 5 feet downward to the center of the lake suggests a maximum temperature of about 1,140°C, in good agreement with the maximum temperature measured during the eruption of 1,140°C. The temperature at the base of the crust was deter- mined to be 1,067°i2°C during 4 penetrations, using the method described by Ault and others (1962). This is the temperature at which a pointed mullite probe 1 inch in diameter with walls 0.1 inch thick can be pushed slowly under a load of about 200 pounds MELT 10r DEPTH, IN FEET 12* 14~ 9 am uup ‘8"‘°N l l l | | | 18 l 400 600 800 1000 TEMPERATURE, IN DEGREES CENTIGRADE | O 200 FIGURE 3.——Graph showing temperature gradients in Alae lava lake on August 30, November 5 and 8, and December 30, 1963. The gradient of November 5 was measured immedi- ately before drilling; that of November 8 was measured soon after drilling. through the chilled lava after drilling, and corre- sponds to the yielding temperature of the basaltic glass under these conditions. Actually the base of the crust is a zone several feet thick in which the abun— dance of the solid material and the strength gradually increase upward; at 1,067 °C the lava consists of equally abundant melt and crystalline material. The depth of the 500°C isotherm, the 800°C iso— therm, and the 1,067°C isotherm (the base of the crust) are plotted against the square—root of time on figure 4. The data from measured gradients are sup plemented by depths to the base of the crust where penetrated in drilling, and estimated thicknesses of the crust during the eruption. Thickness a (fig. 4) of 3 to 4 inches is based on the average thickness of pahoehoe slabs in the lava levee at the edge of the lake; the slabs are from crust that was rafted across the lake in about 11/; hours during the night of August 21—22. Thickness b of 6 to 9 inches was estimated during a trip to the edge of the lava lake at 18"30m August 22; MINE RALOGY AND PETROLOGY at that time the crust was barely thick enough to walk upon with caution. Thickness c of 10 to 12 inches is based on the thickness of slabby crust in tumuli on the lake that were formed during drainback of molten lava into the vent at about 061‘00'n August 23. The rate of depression of the isotherms has markedly decreased since the formation of the lava lake; for ex- ample, the thickness of the crust increased at the rate of 25 feet per month after 0.01 month (7.3 hours), 3.5 feet per month after 1 month, and 2.0 feet per month after 6 months. With respect to the square root of time, however, the rate of depression of the isotherms has been constant over extended periods. Thus for the 6-month interval shown on figure 4, each isotherm can be represented by 3 straight line segments, each of which differs in slope from the adjacent segments. These differences are small, however, and not readily apparent where the data from Alae and Kilauea Iki lava lakes are compared over a 36-month period on the smaller scale of figure 6. The isotherms of figure 4 were temporarily displaced by rainfall (as in mid- September) or by drilling water (as in November), but they recovered over periods of several days or weeks in the absence of rain and of drilling. A linear relation between the depth of an isotherm and the square root of time follows from the equations for the conductive cooling of a body, such as that of Carslaw and Jaeger (1959, equation 7, section 2.4) for a semi-infinite body initially a uniform temperature, V, by reducing its surface temperature to zero at time, 23:0:2 0 v x 17— erf 2m’ Where v=temperature at depth m at time t, k=diffusivity, and erf=the tabulated error function. Comparing the depths, x1 and 222 of an isotherm, 7), at times t1 and t2, 1) 9:1 932 T7: erf2m= erf 2x/k—tz- Thus 151 _ 132 247671— Zw/k—tz and a_ VI 952 JE 2 Note that the equation is an idealization, assuming heat loss by conduction only, and neglecting heat loss by convection, radiation, and volatile transfer, and heat gain from the latent heat of fusion of the lava. PECK, MOORE, AND KOJIMA D5 1964 EXPLANATION DEC. JAN. | FEB. I I DEPTH, IN FEET N O ,— L Depth to base of crust where penetrated by drilling A Depth estimated during eruption (discussed in text) DRILL HOLE 1 0 Measured depth 0 Depth, from projected gradient DRILL HOLES 3 AND 4 I Measured depth u. IN INCHES w w 4> o o o l l l cu M u LATIVE RAINFALL 8 I Depth, from projected gradient O 1 2 3 4 5 6 7 8 9 SQUARE ROOT OF TIME, IN DAYS FIGURE 4.—Depth of 500°C isotherm, 800°C isotherm, and 1,067°C isotherm (base of crust) in Alae lava lake, and cumulative rainfall as a function of the square root of time. to the points least affected by rainfall and drilling water. The rate of depression of isotherms at the main drilling site (drill holes 1, 2, 3, and 4) has not remained constant with respect to the square root of time during the 6 months following the eruption. The rate of depression of the base of the crust, dx/dt, has changed from 2.5/x/Z (with time t in months of 30.4 days) during the later part of the eruption, to 3.5/Jf during Sep- tember, to 5.0/JE during January and February. The reason for the change is obscured by the drastic effect at the main drilling site of cooling water used during the drilling. Possibly the change took place only at this site as the result of the abundant use of water during repeated drilling. The change probably is not the result of heavy rainfall, as can be seen by /comparing the major inflection points on the cumulative rainfall curve with the discontinuities in the isothermal curves on figure 4. However, it may be caused by a progres- sive increase with time in the diffusivity of the lava solidifying at the base of the crust. The vesicularity Dashed lines are idealized isotherms fitted Vertical bars at top of figure represent drilling dates. of the crust of Alae lava lake decreases with depth from an average of 30 to 40 percent in the upper 1 foot to about 10 percent below 10 feet. The vesicularity-depth curve breaks sharply between 1 and 2 feet and between 8 and 10 feet——depths that correspond approximately to the discontinuities in the 1,067 °C isothermal curve. If the thermal conductivity of the crust increases with decreasing vesicularity more rapidly than does density, then diffusivity will also increase, since k—K __—J pc k: diffusivity, K = conductivity, c=specific heat, and p= density. Where On December 16, a hole (drill hole 5 in the table) was drilled 29 feet to near the base of the lava lake at D6 a site 50 feet from the southeast edge of the lake. Microscopic study of the core indicates that the drill hole did not reach the base of the lake, but the increas- ing vesicularity of core from the lower 3 feet suggests that the base is close. Comparison of the location of the hole with a special 122400 scale map of the pre- eruption topography of the bottom of the crater (pre- pared photogrammetrically with 5-foot contour inter- vals by the Topographic Division of the Geological Survey) indicates a lake thickness of 25i5 feet. Thus the lake is about 30 feet thick at the site. Tempera- ture profiles (fig. 5) during the period December 18 to February 26 show maxima between 18 and 20 feet, 60 to 70 percent of the depth to the base of the lake. These depths are comparable to those that would be anticipated from theoretical analysis of cooling at the center or edge of a sheet, such as that of J aeger (1961, figs. 1, 2, and 11). COMPARISON WITH KILAUEA IKI LAVA LAKE The thickness of the crust of Alae lava lake as a function of the square root of time is compared with that of Kilauea Iki lava lake on figure 6. Estimates of thickness based on gradients strongly affected by 0 I I I I I I I I l 12— ‘ 16— —‘ DEPTH, IN FEET X0 20' — 24— A 28% l l | l | d l i I O 200 400 600 800 1000 TEMPERATURE, IN DEGREES CENTIGRADE FIGURE 5.—Temperature gradients in the thin edge of Alae lava lake on December 30, 1963, and February 26, 1964, and depth of maximum temperatures on December 18 and 30, 1963 (a); January 29, 1964 (b), and February 17 and 26, 1964 (c). MINE RALOGY AND PETROLOGY drilling water or rainfall have been omitted. The dashed line on figure 6 is a theoretical curve for Kilauea Iki lava lake (Ault and others, 1962, fig. 3) during the first 4 months after the formation of the lake, a period when no temperature data were obtained from the cooling lake; the curve is based on calcula- tions from 2 temperature profiles obtained 6 and 8 months after the formation of the lake (Ault and others, 1961, p. 793). These calculations led to the suggestion that the crust of Kilauea Iki lava lake was 2.4 feet thick after 1 month (Ault and others, 1961, p. 793; 1962, p. 2811). However, later data from Kilauea Iki shown on figure 6 (J. G. Moore and D. H. Richter, written communication, Jan. 1964) and data from Alae show that the calculated rate of increase in thickness of the crust of Kilauea Iki lava lake for the period from 1 to 4 months was too great, and that 0 _ FKLL'IIlllllllllllllrll'filllIll-J - %\ -I — \ - _ \ _ 10— 0:) — _ \ s _ 0Q _ _ o _. ,_ _ _ 520— — u. _ ‘ _ g r _ 1‘ _ - Eso— — Iu — _ D — 4 40— — 50 IIIIlIiIIliIIIlIIIIlILIIlIiIIlI o 1 2 3 4 5 6 SQUARE ROOT OF TIME, IN MONTHS EXPLANATION ALAE LAVA LAKE KILAUEA IKI LAVA LAKE O A 1067°C isotherm 1065°C isotherm 0 A Base of crust Base of crust ——.— Average thickness of crust (1065‘C isotherm) Thickness of crust, from extrapolated data FIGURE 6.—Selected thicknesses of crust in Alae and Kilauea Iki lava lakes as a function of the square root of time. Depths of the 1,067°C isotherm in Alae lava lake and the 1,065°C isotherm in Kilauea Iki lava lake are based on (1) measured or extrapolated gradients least affected by drilling water or rainfall, and (2) an estimated thickness of the crust during the August 1963 eruption. The extrapolated curve for the thick- ness of the crust of Kilauea Iki lava lake during the first 4 months is from Ault and others (1962, fig. 3). Time for Alae lava lake is measured from 061100m August 22, 1963; time for Kilauea Iki lava lake is. measured from December 23, 1959. Data on Kilauea Iki is from Ault and others (1961, 1962) and J. G. Moore and D. H. Richter (written communication, Jan. 1964). PECK, MOORE, the suggested crustal thickness of 2.4 feet after 1 month was too small. The crust of Alae lava lake was 6.5 feet thick after 1 month. Comparison of the data from the two lakes (fig. 6) indicates that the crusts of both grew at about the same rate; both had about 19 feet of crust 6 months after they formed. Since both lakes had similar in- itial temperatures, the similarity of their cooling rates indicates that the lava in both lakes had about the same thermal diffusivity. l AND KOJvIMA D7 REFERENCES Ault, W. U., Eaton, J. P., and Richter, D. H., 1961, Lava tem- peratures in the 1959 Kilauea eruption and cooling lake: Geol. Soc. America Bull, v. 72, p. 791—794. Ault, W. U., Richter, D. H., and Stewart, D. B., 1962, A tem- perature probe into the melt of the Kilauea Iki lava lake in Hawaii: Jour. Geophys. Research, v. 67, p. 2809—2812. Carslaw, H. S., and Jaeger, J. C., 1959, Conduction of heat in solids: London, Oxford Univ. Press, 510 p. Jaeger, J. 0., 1961, The cooling of irregularly shaped igneous bodies: Am. Jour. Sci., v. 259, p. 721—734. GEOLOGICAL SURVEY RESEARCH 1964 VARIATION IN MODES AND NORMS OF AN “HOMOGENEOUS” PLUTON OF THE BOULDER BATHOLITH, MONTANA By ROBERT I. TILLING, Washington, DC. Abstract—In outcrop and in hand sample, the granodiorite of Rader Creek is one of the most homogeneous-appearing plu— tons in the composite Boulder batholith. However, detailed study of 36 chemically analyzed specimens of the granodiorite shows significant variations in mode and norm which indicate that the apparently “homogeneous” pluton is actually zoned compositionally. The Boulder batholith is a composite intrusive mass which ranges in composition from syenogabbro to alaskite and is exposed over an area of approximately 1,200 square miles in southwestern Montana. Field relations demonstrate that the syenogabbroic plutons (too small to be shown on fig. 1) are earliest in the intrusive sequence. Next in sequence in the southern part of the batholith is the granodiorite of Rader Creek. The Butte Quartz Monzonite, which is coex- tensive with the Clancy Granodiorite of Knopf (1957), cuts the granodiorite of Rader Creek and is in turn out by younger plutons of leucogranodiorite and alas— kite. In the northern part of the batholith, the Union- ville Granodiorite of Knopf (1957) is younger than the syenogabbroic bodies and older than the Butte- Clancy rocks. As the Unionville Granodiorite and the granodiorite of Rader Creek occupy similar positions in the intrusive sequence, they are perhaps correlative. The Boulder batholith intrudes rocks ranging from Precambrian to Late Cretaceous in age and is uncon- formably overlain and locally injected by the Eocene Lowland Creek Volcanics (Smedes and Thomas, 1964). Thus, the emplacement of the batholith was post-Late Cretaceous and pre—Eocene. K—Ar radiometric ages of biotite (7 0—76 million years) of the batholith rocks are consistent with the age of the batholith inferred from stratigraphic and structural relations (M. R. Klepper and W. H. Smedes, oral communications, 1963). This study is a progress report of a recently initiated systematic investigation of the petrology and chemis- try of the Boulder batholith. The 36 specimens studied in this report were collected in the summer of 1962 from the best exposed portions of the granodiorite pluton of Rader Creek along two east—west traverses and from quarry pits (fig. 2). The modal and norma— tive data presented here not only serve to test the homogeneity of the pluton but also to provide a valu- able and necessary adjunct to the detailed mineralogic and chemical investigation currently underway on the individual mineral phases in the granodiorite and other batholith rocks. MAC‘ROSCOPIC AND MICROSCOPIC DESCRIPTION Where not exposed in roadcuts and quarry pits, the granodiorite of Rader Creek crops out as round boul- dery masses with grayish-brown weathered surfaces. Freshly fractured surfaces always have a distinctive bluish-gray color. In hand sample, the rock is medium grained and typically displays equigranular granitoid texture, spotted by small clots of mafic minerals which are generally at least several inches apart. The char- acteristically equigranular granodiorite, however, grades imperceptibly into porphyritic varieties( with plagioclase phenocrysts up to 1 cm in length) at the easternmost margin of the outcrop area adjacent to Tertiary valley fill. It should be emphasized that all specimens, with the exception of porphyritic variants collected from the two easternmost localities (fig. 2), are remarkably uniform macroscopically. In fact, it was because of this monotonously homogeneous appear- ance in outcrop and hand sample that the granodiorite of Rader Creek was selected as the most suitable unit of the batholith to test the homogeneity of a mappable unit. U.S. GEOL. SURVEY PROF. PAPER 501-1), PAGES D8-Dl3 D8 TILLING Under the microscope, the granodiorite, with the exception of the macroscopically porphyritic speci- mens, has a hypidiomorphic—granular texture composed of grains which range from 0.5 mm to 3.5 mm across and average 1.5 mm. A specimen from the western- 112"50' IOMILES 46 , Butte MONTANA I Area of report EXPLANATION Butte Quartz Monzonite and related rocks Rocks of post» or pre—batholithic age Granodiorite of Rader Creek / x / I Leucogranodiorite I‘ v 7 1 r v Granodiorite, Unionville Granodiorite undivided FIGURE 1.—Index map of the Boulder batholith, showing dis- tribution of major intrusive units and location of area studied in detail (shown on fig. 2). D9 most locality near the contact with the Butte Quartz Monzonite (fig. 2), however, exhibits an atypical microporphyritic texture which is not detectable in hand sample. The principal constituents of all sam- ples are plagioclase, K—feldspar, quartz, hornblende, and biotite; accessory minerals include opaque min- erals, apatite, sphene, zircon, tourmaline, and, prob- ably, monazite. Subhedral plagioclase crystals, gen- erally with myrmekitic borders, show moderate to strong normal zoning from calcic andesine to Oligo- clase, and weaker oscillatory zoning. Reconnaissance of plagioclase composition by flat-stage methods indi- cates that the anorthite content ranges from Ans“6 in the core to An32_20 at the margins. The cores of some plagioclase grains are sericitized and (or) slightly epidotized. The K-feldspar is orthoclase microper- thite which forms large poikilitic optically continuous plates. In any given thin section, the microperthite grains show extreme variability in the extent of grid twinning, ranging from completely untwinned grains to distinctly microclinic grains; moreover, portions of a single grain may exhibit varying degrees of grid twinning. Anhedral quartz characteristically occupies interstices and commonly displays undulatory or patchy extinction. Green hornblende, some of which contains ragged relict cores of augite, occurs as slightly biotitized and (or) chloritized subhedral prisms. Sub- hedral biotite flakes, pleochroic from pale yellow to dark brown or greenish brown, are generally associated with irregular aggregates of sphene. The opaque minerals are concentrated in the mafic minerals, par- ticularly in areas where the mafic minerals themselves are clustered to form clots which give the granodiorite its distinctive sparsely spotted appearance in hand sample. VARIATIONS IN MODAL .AND NORMATIVE COMPOSITION At least two standard—size thin sections were cut from each hand specimen, which, on the average, weighed close to 10 pounds. All modes, determined by means of a Chayes click stage, are based on at least 1,000 point counts per thin section. To facilitate de- termination of K-feldspar, all thin sections were stained with sodium cobaltinitrite. The accompanying table (p. D11) shows the reproducibility of the mode of a given thin section. There is excellent agreement be- tween the modes, regardless of the number of point counts and the bias of the various operators. D10 MINE RALOGY AND PETROLOGY Z \ a “Normal Zone" <24 percent normative or >10 percent femic ”Less mafic zone'” < 24 percent normative or _,_ 24 percent normative or > 10 percent femic ‘ EXPLANATION .x\\ s‘ Tertiary rocks \ / I S /\‘/ Leucogranodiorite Butte Quartz Monzonite Granodiorite of Rader Creek Rocks of pre- batholithic age X Sample locality ' ""17! .. "'5. Q I’u- ... A , ,1. .. , Arbitrary zonal boundary FIGURE 2.—Map showing sample localities and compositional zonation in the granodiorite of Rader Creek, about 15 miles southeast of Butte, Mont. Modal compositions of the granodiorite of Rader Creek are plotted on figure 3A. It is important to note that modes determined from several thin sections of the same hand specimen often exhibit a greater range than do the modes of single samples of rocks from separate localities. Thus, from even casual examina~ tion of figure 3A, it is apparent that the mode based on a single thin section is rarely representative of the modal composition of the hand specimen, let alone the entire rock unit. To test the possibility that some unrecognized linear or planar fabric might cause the often wide range in mode, modes were determined for three randomly selected specimens, each represented by three mutually perpendicular thin sections. These specimens showed smaller range in mode than the range observed in most of the other rocks represented by only two sections cut at random. This suggests that the variations in mode do not reflect any subtle planar or linear fabric, because if the modes did, in fact, reflect rock fabric, then the differences in mode in the specimens repre- sented by three mutually perpendicular sections should be as great as, or greater than, those in specimens with only two random sections. Rather, the modal differ- ences between thin sections cut from the same speci- men can generally be accounted for by the differing proportions of the characteristically poikilitic, blebby K—feldspar and quartz in the sections. Figure 3B is a plot of CIPW normative minerals computed from rapid rock chemical analyses, each of which is based on several pounds of chips from the same large specimen from which thin sections were cut. Although the range in normative quartz is ap- proximately the same as that in modal quartz, the scatter in the ratio plagioclase/K-feldspar, represented by the width of fields 1 and 3 on figure 3 (excluding points bounded by the dashed line), is only about half as wide for the normative as for the modal plots, if averages of at least two modal determinations (open circles) are used. The scatter is only a third as Wide if single modal determinations (ends of bars) are used. In other words, the variation in modal quartz cannot be “averaged out” by chemical analysis, but the scatter in plagioclase/K—feldspar is significantly reduced. The data plotted on figure 3 have spatial signifi- cance. On figure 3B, the field enclosed by a solid line contains points which represent rocks collected from the area west of the arbitrarily drawn stippled line (shown on fig. 2), all of which have less than 10 per— cent of normative femic minerals (in terms of quartz— TILLING femic minerals—total feldspar). Those points enclosed by the dashed line represent rocks collected from the area east of another arbitrarily drawn stippled line (fig. 2) ; these rocks contain more than 24 percent of normative K-feldspar (in terms of quartz-plagioclase— K-feldspar) and are distinctively more potassic than rocks from the rest of the sampled area. These arbi- trary zones—less mafic, normal, and potassic—based on normative compositions can likewise be established by modal compositions; the zones based on modal data, however, are not as sharply defined (fig. 3A). The plot of the specimen with the lowest normative quartz content (collected at the western end of the northern east-west traverse) is anomalous and may indicate contamination by Paleozoic carbonate rocks present in the nearby screen of prebatholithic rocks (see fig. 2). The variations in modal and normative compositions of the grandodiorite of Rader Creek are summarized on figure 4, on which the plotted data of figure 3 have been contoured and superimposed. There can be no question that the clearly defined maxima of the norma- tive data have their counterparts in the somewhat more diffuse maxima of the modal data. The normative and modal maxima are slightly offset in the manner to be expected from a comparison between mode and norm. These discrepancies are inherent in the calculation of the CIPW norm, in which orthoclase is computed as 01‘100; in determination of the mode the composition of the K-feldspar (orthoclase microperthite) is ap- proximately Ormso. Also, in calculation of the norm, certain oxides may be assigned to a specific mineral and no other; for example, K20 is assigned solely to K-feldspar even though it is present in other modal minerals, mainly biotite. Discrepancy between the normative and modal maxima caused by the‘use of inconsistent units—weight percent (norm) versus vol- ume percent (mode)—is probably insignificant. This is because of the quartz—total feldspar—mafic (femic) minerals plot (fig. 43), where such discrepancy would be greatest due to the large differences in specific D11 gravities of the minerals plotted, the conversion of modal data into weight percent would shift the modal maximum toward the mafic minerals corner, thus in- creasing, rather than decreasing the discrepancy. The petrologic significance of the variations in modes and norms observed in the granodiorite of Rader Creek is unknown at present and can better be evaluated when the other units of the Boulder batho- lith also are studied in detail. Nonetheless, it is per- haps petrologically and (or) structurally significant that the arbitrarily delimited zones here described are very crudely parallel to the contact between the grandodiorite and the younger leucogranodioritic plutons to the west and, at the same time, are roughly perpendicular to the trend of the screen of prebatho- lithic rocks which separates the granodiorite from the Butte Quartz Monzonite (figs. 1 and 2). Moreover, the data presented here clearly demon- strate that even an exceedingly homogeneous-appear- ing mappable unit such as the granodiorite of Rader Creek may not be mineralogically or chemically homogeneous. To be sure, differences in the propor- tion of dark minerals from locality to locality within the unit were noted during the course of fieldwork but were interpreted as minor random departures from the overall homogeneity of the unit. However, with the accumulation of more detailed data, it became evident that the apparently homogeneous Rader Creek pluton is actually compositionally zoned. Obviously then, the assessment of “homogeneity” must be tempered by the degree of detail required or desired in a particular study, by the amount of data available, and by the reservation that a certain amount of variation may exist. What are considered as systematic and, pos- sibly, significant departures from “homogeneity” in this study—approximately 10 percent K—feldspar rela- tive to a gross average of the other leucocratic con— stituents and 5 percent mafic minerals relative to a gross average in the total rock—perhaps might only be considered as expectable variations within the Reproducibility of the mode of a single thin section of granodiorite of Rader Creek 1 [Results in volume percent] 2,000 point counts 1,000 point counts Average Mean deviation 1 2 3 4 5 ‘6 7 8 9 Plagioclase ........................... 51. 3 51. 0 51.3 50. 7 53.0 50. 2 50. 3 47. 3 50. 7 50. 7 0.8 K-feldspar ___________________________ 14. 7 16. 6 13. 2 14. 7 13. 3 15. 3 16. 2 16. 2 14. 0 14. 9 1. 0 Quartz _______________________________ 20. 3 19. 7 20. 1 19. 1 20. 3 20. 5 18. 2 22. 1 20. 4 20. 1 - 7 Hornblende __________________________ 6. 8 5. 7 6. 9 7. 0 6. 1 7. 0 6. 3 6. 4 7. 2 6. 6 . 4 Biotite __________________________________ 5. 6 5. 1 6. 6 6. 5 5. 1 4. 8 7. 5 7. 2 5. 8 6. 0 - 8 Opaque accessory minerals _____________ . 9 1. 2 1. 4 1. 3 1. 6 1. A 1. 0 . 6 . 8 1. 1 - 3 Non-opaque accessory minerals _________ . 4 . 7 . 5 . 7 . 6 . 8 . 5 . 2 1. 1 . 6 . 2 1 Modes 1-6 are by the writer, mode 7 by M. R. Klepper, mode 8 by H. 742—652 0—64 2 W. Smedes, and mode 9 by T. L. Wright. D12 MINERALOGY AND PETROLOGY Quartz Fields of modal plots l i Plagioclase Total feldspar Mafic minerals Mafic m nerals Flelds of normative 'ih . l» Orthoclase Femic minerals Plug oclase Total feldspar o Plagioclase B. Normative ' TILLING D13 Fields of contoured Plagioclase Total feldspar Quartz K-feldspar Mafic minerals ‘1 A "a r? ' ‘5 5' "5 4:? ’6 /,9 , d), Plagioclase K-feldspar . Total feldspar Mafic minerals (orthoclase) (femic minerals) B FIGURE 4.—Contour diagram showing proportions of normative (solid contours) and modal (dashed contours) minerals in the granodiorite of Rader Creek. tive data in weight percent. (inset). limits of “homogeneity” in other petrologic applica- tions. If so, then the variations representative of the unit could be determined merely by the study of 3 or 4 properly spaced hand specimens. In any event, this preliminary investigation emphasizes the commonly neglected fact that selection of supposedly “represem tative” samples for purposes of comparing modal and (or) chemical compositions of diflerent rock units Data compiled from the plotted circles on figure 3; modal data in volume percent and norma- Contours shown represent 1, 2, 4, and 6 points per 0.06 percent of area of compositional tr1angle must be done with great caution to avoid erroneous conclusions from misleading comparisons. REFERENCES Knopf, Adolph, 1957, The Boulder bathylith of Montana: Am. J our. ‘Sci., v. 255, p. 81—103. Smedes, H. W., and Thomas, H. H., 1964, Re-assignment of the Lowland Creek volcanics to Eocene age: Jour. Geology. [in press] FIGURE 3.—Relative proportions of modal (A) and CIPW normative (B) minerals in the granodiorite of Rader Creek. Fields of modal plots (1, 2) in volume percent and normative plots (3, 4) in weight percent, with reference to the complete com— positional triangles, are outlined in insets. Open circles are plots in the quartz-plagioclase-K-feldspar (or orthoclase) triangle; filled circles are plots in the quartz-total feldspar-mafic (or femic) minerals triangle. Ends of bars indicate compositions of different thin sections (or analyses) from the same hand specimen, whose average composition is marked by the position of the circle. Fields enclosed by a solid line represent rocks from the less mafic zone; fields enclosed by a dashed line repre- sent rocks from the potassic zone (see text and fig. 2). fl GEOLOGICAL SURVEY RESEARCH 1964 MAFIC LAVAS OF DOME MOUNTAIN, TIMBER MOUNTAIN CALDERA, SOUTHERN NEVADA By STANLEY J. LUFT, Washington, D.C. Work done in cooperation with the U.S. Atomic Energy Commission Abstract—Eleven or more mafic flows of Dome Mountain were erupted in Pliocene time within the moat of the Timber Mountain caldera of southern Nevada. They consist of a lower group of trachybasalt, basalt, and andesite flows; a middle group of trachyandesite flows; and an upper group of trachy- andesite to latite flows. Difierentiation toward the upper flows is clearly indicated by decreasing abundance of mafic minerals, color index, and content of normative anorthite, and by in- creasing content of alkalies and silica, K/Ca ratio, and differ— entiation index. The rocks are silica saturated. A Peacock index slightly below 56 puts the suite near the boundary of the alkali-calcic and calc—alkalic fields. The normal calc-alkalic differentiation trend shows marked chemical variation for erup- tions of limited extent and duration. A sequence of mafic lava flows forms a subarcuate outcrop area of about 25 square miles on the southeast flank of Timber Mountain on the Nevada Test Site in southern Nye County, Nev. (fig. 1). Dome Mountain, 6,195 feet high, is the most conspicuous landmark in this area. Eleven or more flows having a maximum stratigraphic thickness of more than 900 feet are present on the northeast slope of the mountain where it is cut by Chukar Canyon. The sequence thins abruptly away from Dome Mountain and is repre- sented by a single flow near, and north of, Cat Canyon. Dome Mountain itself is an erosionally truncated pile of mafic to intermediate lava flows which in general appearance can be described as a miniature shield volcano. These flows were first noted by Ball (1907, p. 153), who along with later workers considered them basalts. The chemical and petrographic data obtained during the present study show them to be primarily trachy— basalt and trachyandesite. The flows are of particular interest because they show a considerable degree of magmatic differentiation for rocks erupted during a short time span. GE‘OLOGIC RELATIONS The mafic lavas of Dome Mountain are part of a volcanic sequence that includes bedded and massive tuft, welded tufl', rhyolitic and mafic lava flows, and poorly consolidated tufl'aceous sand and gravel de- posited in the structural depression or moat of the Timber Mountain caldera (Byers and others, 1963). The attitude of the sequence varies from horizontal to gently dipping away from Timber Mountain. The Dome Mountain lavas flank the faulted and eroded welded tufis of Cat Canyon, but generally rest uncon— formably upon the younger rhyolitic lava flows and tufls of Fortymile Canyon. Locally the Dome Moun~ tain flows overlie scoriaceous basaltic andesite older than the rhyolite of Fortymile Canyon. Rliyolite lava flows of Shoshone Mountain overlie the Dome Moun- tain lavas east of Fortymile Canyon, and two thin flows of olivine-andesine trachybasalt overlie the Dome Mountain lavas on the west and north slopes of Dome Mountain. The Dome Mountain and younger lavas are overlain conformably by the Spearhead Member of the Thirsty Canyon Tuff (Noble and others, 1964) at Buckboard Mesa and along Beatty Wash. Tuffa- ceous sand and gravel, locally indurated, are inter— layered with the Dome Mountain lavas and with the overlying volcanic rocks. Source vents clearly related to the Dome Mountain lava flows were not recognized in the field. The upper flows on Dome Mountain dip away from the summit, suggesting that this area was the major source for the upper flows. One or perhaps two thin and discontinu- U.S. GEOL. SURVEY PROF. PAPER 501—D, PAGES D14—D21 D14 LUFT 116° 22’30“ Buckboard Area of report Timber Mountain 37°OO' Dome A ‘Mountain I Shoshone \ 0 Mountain O 1 2 3 4 MILES FIGURE 1.—Map of a portion of the Nevada Test Site, Nye County, Nev., showing principal topographic features and general distribution of the mafic lavas (stippled) of Dome Mountain. ous dikes of olivine trachyandesite, which chemically and mineralogically resemble the lower Dome Moun- tain flows, are present along a north-northwest-trend- ing normal fault of minor displacement in tufi north of Cat Canyon and west of Buckboard Mesa, outside the principal outcrop area of the Dome Mountain lavas. Although a dike is known to be a feeder for a very small flow, most of the lavas probably issued from fissures which now are buried beneath and near Dome Mountain. A small extinct fumarole occurs below the summit of the mountain. Spatter cones near the bottom of Fortymile Canyon appear to be related to the scoriaceous basaltic andesite that under- lies the rhyolite of Fortymile Canyon. D15 Rocks above, and below, the mafic lavas of Dome Mountain have been dated by the K—Ar method by R. W. Kistler of the U.S. Geological Survey. The overlying Spearhead Member of the Thirtsy Canyon Tufl' is about 7.5 million years old (Noble and others, 1964), and the underlying tuifs of Cat Canyon are about 10.9 million years old (F. A. McKeown, written communication, 1963). The age of the Dome Moun— tain lavas is bracketed as Pliocene and, on the basis of field relations with the overlying and underlying vol- canic rocks, is probably not more than 8 million years. Individual flows range in thickness from 0 to about 170 feet; the average thickness is about 70 feet. A typi— cal flow has a reddish, glassy, scoriaceous, and rubbly basal zone, less than 5 feet thick. The basal zone grades upward through a few feet of transitional rock, characterized by closely spaced horizontal jointing or sheeting, into a massive central zone that forms the thickest part of the flow. Fractures and joints in this zone are widely spaced and usually broadly curving. The central zone grades upward into a zone of varia- ble thickness, usually less than 25 feet, of scoriaceous rock at the top of the flow. The top few feet of this upper zone are reddish. Distal ends of flows are contorted, blocky, scoriaceous, and rubbly. The rubble and scoria commonly are mixed with sediment of the caldera moat. Vesicles, which may be completely absent from the main part of the central zone, form as much as 40 percent of the lower and upper zones of a flow. Most of the vesicles are less than 1/2 inch long, but a few are as much as 3 inches long. Length-to—height ratios are greatest in the lower part of the flow and may reach 10:1 or more. The ratios are generally less than 2:1 in the central and upper zones. The lavas in most places are fresh, and are dark to medium gray and rarely medium light gray (Rock- color chart, Goddard, 1948). Weathering colors vary, but are chiefly pale and moderate yellowish brown, grayish orange, and yellowish gray. PETROGRAPHY Petrographically, the mafic lavas of Dome Mountain are similar to andesitic rocks described in standard works such as those of Johannsen (1937, p. 162-166) and Williams and others (1954, p. 93-95). The rocks generally have a fine—grained matrix set with poorly discernible phenocrysts, giving the rocks a uniform megascopic appearance. Textures are generally seri— ate, and intersertal or intergranular to subophitic. Pilotaxitic texture characterizes the matrix of about D16 half the specimens studied, but true trachytic texture is rare. Phenocrysts commonly tend to form glomero- porphyritic clusters. Many of the upper flows are diktytaxitic, but few of the lower flows are. The flows are divisible chemically and mineralogi- cally into three groups. The lower flows are charac- terized by phenocrysts of iddingsite after olivine and are the most mafic rocks of the sequence. They are chiefly trachybasalt, but also include basalt and ande- site. The lower flows are present in the topographi- cally lower parts of Fortymile and Chukar Canyons and are the only flows present near and north of Cat Canyon. Two flows overlying the lower flows in the measured section are only slightly less mafic than those below but are almost indistinguishable in the field from the upper flows and have generally been mapped with them. These middle flows are trachyandesite. The upper flows form an uninterrupted pile within the major area that includes Dome Mountain and lies be- tween Cat Canyon and Beatty Wash. These flows MINERALOGY AND PETROLOGY are characterized by ragged and cloudy plagioclase phenocrysts and are also trachyandesite. Chemically, however, the highest flow on Dome Mountain is close to latite in composition. The primary minerals of the mafic flows and the products of magmatic or deuteric alteration, together with the modal composition of chemically analyzed flows, are given in table 1. The modes were deter- mined by counting 2,000 or more points per thin sec- tion. An arbitrary minimum size limit of 0.2 mm for microphenocrysts was empirically found to be useful in accentuating the modal differences between the lower and upper flows. Secondary minerals and voids, never more than 5 percent, were excluded from the modes. Phenocrysts appear to be more abundant in the more mafic of the lower flows than in the rest of the sequence. Although the frequencies of some minerals show progressive increases or decreases that are related to the sequence of eruption, preliminary optical studies do not indicate large variations in the TABLE 1.—Modal composition of chemically analyzed mafic lavas of Dome Mountain [Modes recalculated to 100 percent after excluding secondary minerals and voids. All data in volume percent. Chemical analyses given in table 2] Lower flows—basalt, trachybasalt, and andesite Middle flows— Upper flows—traehyandesite and latite trachyandesite Sample No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Laboratory No. 161242 161018 161017 161693 161129 161016 161128 161019 161694 161021 161024 161022 161696 161025 161695 161023 161020 Field No. ’l‘M— s1.— SL- SL— SL— SL— L— SL— SL— SL— SL— SL— SL- SL— SL— SL— SL— 9724a 62—85 62—84 62—83 62—102 62-82 62—99 62—86 62-88 62—89 62-95 62—92 63—52 62—96 63—50 62—94 62—87 Phenocrysts: Plagioclase, ragged phenocrysts ________ 0 0 0 0 0 0 0 0 2. 6 6. 3 6. 0 6. 9 7. 4 5. 2 5. 0 6. 3 l. 6 Plagioclase, laths ______ 19. 7 25. 0 19. 8 17. 7 21. 9 5. 5 7. 4 12. 2 1. 4 2. 2 5. 2 3. 9 6. 0 6. 4 7. 5 5. 3 4. 2 Clinopyroxene ________ l. 2 1. 4 1. 0 4. 1 1. 2 . 8 . 5 l. 2 . 1 . 4 2. 1 . 9 . 8 1. 3 . 7 . 8 1. 4 Orthopyroxene ________ 0 0 0 0 0 Tr. Tr. 0 . 2 0 . 2 . 2 . 2 Tr. . 1 0 0 Olivine and iddingsite--- 8. 0 5. 8 3. 0 4. 4 7. 5 1. 2 . 3 Tr. Tr. . 2 . 4 . 1 Tr. . 4 . 9 . 2 . 1 Magnetite ____________ 0 0 0 0 O 0 0 . 4 0 0 . 1 . 1 0 . 1 . 1 Tr. Tr. Total phenocrysts- 28. 9 32. 2 23. 8 26. 2 30. 6 7. 5 8. 2 13. 8 4. 3 9. 1 1 14. 0 12. 1 14. 4 13. 4 15. 1 2 12. 7 7. 3 Matrix: Plagioclase a __________ 32. 9 27. 5 32. 1 3‘7. 1 34. 1 34. 8 50. 0 8. 0 53. 7 40. 4 40. 8 48. 7 47. 1 50. 0 31. 9 45. 1 36. 5 Clinopyroxene _________ 16. 3 17. 2 16. 0 8. 3 14. 5 10 5 14. 2 2. 2 16 2 11. 2 7. 8} 9 0 6. 5 6. 9 3. 3 6. 8 7. 3 8fthopyroxene ________ 0 0 0 0 0 ' Tr. 0 ' 0 1. 0 ' . 2 3. g 0 7 0 g ivine _______________ 3. 2 0 0 0' 1. 6 2. 9 . 5. Iddingsite ____________ 7.3 7.1}5~9 10.9}11-8} 8-2 9.0} 3-4}1°-9}8-9 3.1}7-6 3.6 1.7 0 it” 6.1 Opaque minerals ______ 7. 3 7. 4 10. 8 9. 2 6. 7 17. 0 7. 8 2. 7 6. 4 3. 4 4. 2 4. 1 2. 6 3. 6 2. 2 2. 3 6. 2 Glass and crypto- crystalline materiaL- 4. 1 8. 6 11. 4 8. 3 2. 3 ‘22. 0 10. 8 69. 9 8. 5 27. 0 27. 5 18. 5 22. 7 20. l 41. 8 26. 9 36. 6 Total matrix ______ 71. 1 67. 8 76. 2 73. 8 69. 4 92. 5 91. 8 86. 2 95. 7 90. 9 86. 0 87. 9 85. 6 86. 6 84. 9 87. 3 92. 7 Total lava ________ 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. 0 100. O 100. 0 Estimated maximum “___ anorthite content of plagioclase laths _______ A1153 A1157 An“ A1157 Am» An“ An” An” An" An” An53 ___ _ _ Anw Anw A1150, An” An” Sum of mafic minerals (volume percent) ______ 43 39 37 37 42 38 32 (4) 34 24 20% 22 17 18 (4) 16 21 1 Includes trace of homblende(?). 2 Includes 0.1 percent of hornblende (7). ’ May include minor amounts of alkali feldspar and silica minerals. 4 Sum of mafic minerals is anomalously low due to the high content of glass and cryptocrystalline material. LUF'I‘ composition of these minerals. The maximum crystal size remains relatively constant throughout the se- quence. DESCRIPTIVE MINERALOGY The ragged and cloudy plagioclase phenocrysts (to 10 mm) of the upper flows and of one middle flow, best seen on weathered surfaces, closely resemble those described by Kuno (1950, p. 967—968, and figs. 5 and 6) from Hakone Volcano, Japan. They commonly are zoned and twinned and are filled with zonally concen- trated “dust” inclusions and microlites of mafic min- erals. Borders commonly are embayed and corroded, and resorption borders may be alkalic. Some of these crystals appear to be more sodic than the labradorite‘ to andesine laths. Their appearance and textural re- lations suggest an intratelluric origin. Similar crys- tals, described by G. A. Macdonald as inclusion-filled and “moth-eaten,” are considered by him to be charac— teristic of calc-alkaline andesite provinces (in Stark, 1963, p. C5). Plagioclase laths (to 3.5 mm) are sub- hedral to euhedral and irregularly terminated. Larger ones, particularly in the lower flows, show pronounced oscillatory zoning and albite twinning; carlsbad, peri- cline, and baveno twin laws are also represented. Phenocryst-size laths are sodic labradorite to calcic andesine, whereas those of the matrix are chiefly andesine. Differentiation of the laths toward the sodic end was not observed in the preliminary optical study of the sequence of flows (table 1). Minor amounts of alkali feldspar and silica minerals are also present but were counted together with the plagioclase laths. Quartz xenocrysts (to 1 mm) are present in trace quantities in one specimen from a lower flow. The grains are rounded and fractured, and surrounded by reaction rims of radiating acicular clinopyroxene inter- mixed with fine—grained quartz, feldspar, and magnetite. Similar xenocrysts may constitute as much as 0.5 percent of, the later olivine-andesine trachybasalt flows. Clinopyroxene (to 2.3 mm) forms stubby to elongate (axial ratios as high as 5:1) euhedral to anhedral prisms. Simple twins and indistinct zones are present, and mafic inclusions, chiefly magnetite, are common. Phenocryst compositions lie within the diopside and augite fields (colorless or very pale green, pleochroism absent or faint, 2V,=45° to 70°, estimated bire- fringence as much as 0.03). Pigeonite (colorless, length-slow, 2V,z 15°, estimated birefringence as much as 0.01) rarely forms phenocrysts. Subequal amounts of high- and low-calcium pyroxene are present in the matrix. Clinopyroxene commonly jackets ortho- D17 pyroxene phenocrysts, locally forms overgrowths on olivine, and may in turn be jacketed by hornblende(?). Orthopyroxene (to 1.6 mm) forms stubby to elong- ate (axial ratios 2:1 to 10:1) subhedral to euhedral prisms. Most crystals are near enstatite in composi- tion (colorless, 2Vz = 60° to 70°, birefringence esti- mated as up to 0.012), but some hypersthene is also present. Minute crystals are difficult to distinguish from clinopyroxene and olivine. Orthopyroxene, pres- ent in trace quantities only in a few specimens from lower flows, is found in most specimens of the upper flows where it may form more than 1 percent of the rock. It is absent, however, in the most silicic upper flows. No explanation is ventured here for the rela- tive abundance of this early precipitate mineral in the later differentiates of the Dome Mountain sequence, and for the apparent reversal of the usual calc-alkalic trend of diminishing orthopyroxene: clinopyroxene ratios. Olivine (to 2.2 mm) forms stubby to elongate (axial ratios as high as 4:1) euhedral to subhedral dipyra- mids and dipyramidal prisms that are most abundant in the lower flows. The optic sign ranges from (+) to (-—), with a very large 2V. Magnetite inclusions are abundant except in large, probably intratelluric crystals that commonly are resorbed and enclose cryptocrystalline matrix material. Olivine generally is largely to entirely replaced by iddingsite or similar minerals inward from borders and fractures. Matrix- size grains of upper flows tend to be less altered than those of lower flows. Olivine commonly is found in glomeroporphyritic clusters with large later forming plagioclase laths. Magnetite (to 0.6 mm) is the principal opaque min- eral of the lavas, and has a trend similar to that of olivine. Phenocrysts, absent in lower flows, are rounded and embayed or ragged and were probably late forming. Matrix-size grains are euhedral to sub- hedral octahedrons, fresh or partly to completely altered to hematite. Rods, also present, probably in- clude some ilmenite. Apatite and zircon( 2), present in trace quantities throughout the flows, form slender minute prisms in plagioclase and in the glassy matrix. Glass is colorless or red- and gray-brown to black, according to the state of oxidation and quantity of con- tained magnetite “dust.” Colorless and brown glasses are typical of the upper flows. Cryptocrystalline ma- terial includes all matrix material too fine to be iden- tified at 250x magnification. The norms indicate that it probably consists mainly of K-feldspar and silica, probably as tridymite or cristobalite. MINERALOGY AND PETROLOGY D18 o .2: A .2: H .2: A .2: o .2: o .2: m .3 A .2: m .2: 3 .3 o .2: N .2: m .2: A .2: N .2: N .2: o .2: m .2: H .2: m .3 ....... ASPA. A .N N .N ............ w . A .n w .m N . m A 3 .3 m A o .3 m . ...... o .3 N. . ...... N. . ................... SHAHmotwm N. .w m A: w .mA 9 .w m .3 w .w m .N. o .w m .c m. .N. N. .w o AA N. .3 w .3 0 .mA w A: N. .3H N. .3H o .mA m mH ........ 3333M H .N o .m 3 .3 N. .A m A m .N w A o .m N .N a A 3 .m N .c 3 .m o .m H .3 w .3 o .c 3 .m a .m 3 .3 ..... BanmmHHo m A m. A o .N m .A m A m A m A m A o A m A o A m A N. A o .N o .N N A N. A 3 .N 3 .N N A ......... 333 < N .N 3 .m N. .m 3 .N N. .N 3 .N 3 .N 3 .N N. .N N. .N 3 .N N .m N. .m w .m w .m N. .N o .m o .3 m .3 3 .m ......... 3:58: ............ N.N -------------------------------- Nd ---- --- 3.m ---- wA m3 ----ooEaEeA-A w .3 3 .w m .o w .m w .m o .N N. .N m .m o .m m .m w .n w .m H .w w .N o .w 3 .w m .m 3 .w o .N. ------------- ofipmamwg N .3 N am N .8 m .E N .3 H .2 N .NH a .2 3 .2 m .2 3 .2 a .8 m «a o N“ a .3 m .Nm 3 .3 3 .mm m .mm a .wm ....... SENSE a N” w .mm m Nu m .mm a .5 a .3” 3 .mm 3 d. a .3 m .Nm 3 «m w .3... c .8 m «N w Nu m .Nm w .Nm w .mm w .8 w .Nm ........... 852 m .wH o .2 m. .m m .wH 3 .wH o .8 a .2 m .2 N .2 w .2 N .S w .2 H .2 o .S N .2 m .N o .3 m. .m o .3 m .w ....... $28.35 w .w a .m m .m 3 .2 m .2 N .e N .N c .o m A: w .c m .w 3 .o m .m m .w a .H m .a m .m o .m m .m o .m .......... $530 ”was: EH35 ------ mo.V om. mo.V N.A. mo.V mo. N.A. mo.V 3A. mo.V ANo.V mo.V 3o. mo.V Nm. NA S. 3. 3. --..-.-.----N00 3N. . m . 3 A 33. 3.. mm . N3 . no. 3.. ma mm . NN.. A A N A NN.. N .A w A N. .H w A N. A ----------- +ONA.A 3. we. A A 3. NN. N.A . NA . wm. N3. 3. m3. on. ow. w A mN. ma. o .N mo. ow. m. A ----------- ION: Samoan Emmi Aamhoe‘me 23.32:? c .2: o .2: o .2: o .2: o .2: A .2: o .2: H .2: o .2: a .3 o .2: o .2: A .2: o .2: o .2: o .2: o .2: o .2: o .2: o .2: ....... H308 oA . NA . .N. . oA . mo . no . oA . mA . AA. oA . mo . MA . NA . wA . NA . N.A . 0A . MA . NA . N.A . ----------- OaA>A on. 8. 3m. mm. 9... mm. 8. E. 8.. mm. N3. 3. 3N. mm. Nw. 3N. 3N. 33. mm. oN. ............ “OS 3A w .A 3 A m A 3 A m .A m A m .H 3 A 3A m .A N. A m .A o .N o .N 3 A w .A A .N N .N w A -------- 7-405. A .m o .N w .A N .m A .m 3 .m N .m m. .m m .N o .m m .N N .N a .A N. .A o .N m .A N. .A w .A N. .A 3 .A ------------ CNN 3 .3 w .m m .m w .3 3 .3 m .3 N .3 m .3 N .3 3 3 A .3 A .3 w .m m .m m .m N .m m .m 3 .m m .m m .m ----------- ONmZ A .m m .N. w .w m .3 o .m m .m. m .m o .m N .w H .m A .w 3 .N. m .N. o .w m .w w .w o .3 3 .w 3 .w H .3 ------------ OuO N. .N 3 .3 m .m 3 .N w A N. .N a .N 3 .N o .N o .m m .m 3 .3 m .3 a .m N .m. N. .o a .m m .m o .w m .m. ----------- OwA>A 3.3 3.3 3.3 3 .3 3.3 3.3 3 .3 3.3 3 .3 3.3 3.3 3.3 3.3 3.3 3 .3 3.3 3 .3 3.3 3.3 3.3 ---_AOoNA ma 8:3 w .m m .3 w .m c .m 3 .m N. .3 N .3 o .m o .m w .3 m .m m .m 3 .3 m .N N .m. A .3 3 .N N. .3 o .3 m. A ------------ Ooh N .m w .3 w .w w .m 3 m N. .H m .N N. .m w .m m .N w .m o .3 w .m A .w H .3 w .m m .N N .m w .w m .3 ----------- 55m A .3 w .N.: m .3 m A: N. A: w .3 N. A: N. A: N. .3 w A: 3 .mA N. A: 3 A: 3 .NA A .NA w A: o A: w .3 w A: 3 .NA ----------- MON? 0 dm a Na w .om 0 do o .3. 3 .3. N .3 A .3 o .3 o .3 3 .3 o .3 w .Nm 3 Am m Am 0 An w .3. m .3 N .3 o .om ....... $13“me “ AA 2365 noEHwoafioO NA: 3N5 Nw-Nw-Am 33-ij on-va-‘Aw 3-No-Aw Nn-nw-Am 3|ij mm-NoLAm meNw-Aw ww-wa-Aw ow-No-‘Am 33-N3-Aw NwINw-Am INcLAm mw-NwLAm 3m-Nc-Aw nw-NwLAm -A>H..A. .oZ 3me 333 mNcHoH 33m: mNvoA 33:: NNkoA 3NkoA ANkoA 331.: 38:: mNAAwA 3cm: mNAHmA mmcHuA NAkoA onAwA N3NAwA .oZ 303.585 NA-oA m was m NA NA A: nA 3A mA NA AA A: m w N. w w 3 N N A .02 oHQEam Esau m3 2: 0: 9». ca .5938 .388 $2520 352 Avg cfimwcngnomslmaou NEED 353223: 33335 $8253 cushy/3 33.34 1952: 2322 Avg JAawunhaomb .uHmwaAA-Imbpoc SBoA Amenmduzmnoo 25.2322, 38592: 8 3323288 $3533 ”8555 .3 2035328 .550 Aim unto: ”mus. AHwBoA was .335 Am .820 :3:sz .mfiem .D .w .QSEAMA .D {A .AA ”$3153“ $538 NONm uflmaeuofl .o 53.8 5 «5.3: can £5838 Ema» .3 mwmfianfl £3328: “ESQ .8 «.33 owES 36 2:3: 3:3 :QENQNSS 3%Ewfi0lN mqmfiA. D19 LUFT .5 5m 210% 8 :55 H 8. mm mm on we mm mm mm. mm mm. ww 3. «m wfi cw AN am mm. mm 3w 3» aw mH co. mm mm ma ww hm ON wm cm mm. mm mm“ am 5 we Hm mm mm ea. mm 3» mm am mm Hm NN mm ma . om mm mm «N on mm 6 .mm m. .mw m .mm mm . a“ 5 mm 3 mm cm an. mm a.” @N on «N mm «m mm. Hm N@ am «N mm Hm mm mm. mm mm am um «um «um mm aw. am ww mm cm 3 «m mm 3“ am. am 5“ «é pm 5 mm vw «w Hm . a. ww 3‘ mH am mm am wm. mm 1v wv ow ma ww om mm. mm mm on «A» a Na. mm mm. «m ow ww ow m: 3» mm mm. «m ow 5“ 3‘ mm. 3 Na. mm om. «um ow ww 0* 3 am cm 3. mm. mm E «w 2 ........... cw: ...... oaz +on ........... M com ma COMM :30er “3:3th E39295 mqoshcmonm -353 080% «O u M ........ 5?: .530 ........... 565 ‘ nomoafiafiommfl oufiiona + 35? A3853 3:55.82 Emma, 2: x 3:38am $23882 ....... BEiGQ< .......... 352 ....... wwfloonfio ” Gawopwm Ewmoav hnmwgfl oiaafiuoz D20 Secondary minerals include calcite and zeolite, and are found principally in vesicles. Calcite also fills fine fractures and rarely occurs as a replacement of plagio- clase phenocrysts. Potassium—bearing clay minerals line voids and fractures and also locally replace cryptocrystalline matrix. PETROCHEMISTRY Chemical composition, norms, and other petrochemi- cal parameters of the Dome Mountain rocks are given in table 2. Normative color indices (sum of normative femic constituents) are between 17 and 35, thus falling within the andesite range of Kuno (1950, p. 958) and Stark (1963, p. C3). The chemical analyses and norms of the lower and middle flows lie between the values of average basalt and average andesite of Nockolds (1954, tables 6 and 7) and between the average Columbia River Basalt and the average andesite complex of the Cascade Range (Waters, 1955, table 1). Values for Si02, total iron plus MgO, and TiOz are closer to those for basalt, whereas values for A1203 and alkalies are nearer those for andesite. P205 content is unusually high in all analyses of Dome Mountain rocks. The average composition of the lower flows lies between the fields of trachybasalt and basalt, in the classification of Rittmann (1952). The slightly more salic middle flows are olivine trachyandesite by Rittmann’s classifi- cation, but the low modal olivine content and the ab- sence of normative olivine make trachyandesite a better term for these middle flows. The upper flows are higher in SiOz and alkali content, and lower in MgO and CaO than the average doreite of Nockolds (1954, table 5), and are trachyandesite to latite by Rittmann’s classification. All the rocks are silica saturated. The analyses are plotted on a Harker variation dia- gram (fig. 2) which, together with a triangular FeO- MgO—alkali diagram (fig. 3), shows a normal calc- alkaline difl'erentiation trend for the Dome Mountain lavas. The threefold stratigraphic division of the Dome Mountain sequence follows this trend, but the succession within these divisions is random. The high degree of difierentiation of the lavas is further empha- sized by variations in the differentiation index of Thornton and Tuttle (1960), the proportion of norma— tive anorthite, and the KzCa ratios summarized in table 2. Rittmann’s suite index, .9, (1962, p. 110—111) aver— ages 3.1 for the trachybasalt and allied lavas of the MINERALOGY AND PETROLOGY lower flows and 3.5 for the trachyandesite and latite of the middle and upper flows, defining a weakly calc- alkaline suite. The Peacock alkali-lime index (1931, p. 55—56) taken from figure 2 is slightly less than 56, defining the suite as alkali—calcic but near the cal- calkalic field. Lower Middle Upper flows flows flows H‘s Sample No. 123456 7 89 10 1112141617 I Hi Ll 1'3 15 HIIIH H l 17- 15 ,_ _ z LLJ t2 4— Lu 1:. P _ I 9 2 + Lu e At TiO 0 + 2 3 ++ +\r——Hfi1’l Z _ L’i Q 0 >7 0 _ 8— Si02, IN WEIGHT PERCENT FIGURE 2.—Variation diagram for chemically analyzed rocks of the mafic lavas of Dome Mountain. Data from table 2. LUFT EXPLANATION UPPER FLOWS + Latite o Trachyandesite MIDDLE FLOWS A Trachyandesite LOWER FLOWS x Pigeonite andesite D Andesine basalt O OIivine-andesine trachybasalt Total iron as FeO X7 l 160 12 ‘8 "3 17 ° 1° ‘9 6.4 25 + +‘9‘l: 131514 V Al kal ies 8° 5° 4° 2° MOLECULAR PERCENT MgO FIGURE 3.~—FeO-MgO-al‘(ali diagram, showing trend of differen- tiation for the mafic lavas of Dome Mountain. Data from table 2. REFERENCES Ball, S. H., 1907, A geologic reconnaissance in southwestern Nevada and eastern California: U.S. Geol. Survey Bull. 308, p. 153. Byers, F. M., Jr., Orkild, P. P., Carr, W. J ., and Christiansen, R. L., 1963, Timber Mountain caldera, Nevada Test Site 'X‘ D21 and vicinity—a progress report: Am. Geophys. Union Trans, v. 44, p. 113. Goddard, E N., chm., and others, 1948, Rock-color chart: Washington, DC, Natl. Research Council. Johannsen, Albert, 1937, A descriptive petrography of the igne- ous rocks, v. III. The intermediate rocks: Univ. Chicago Press, 360 p. Kuno, Hisashi, 1950, Petrology of Hakone Volcano and the adjacent areas, Japan: Geol. Soc. America Bull., v. 61, p. 957—1020. Noble, D. C., Anderson, R. E., Ekren, E. B., and O‘Connor, J. T., 1964, Thirsty Canyon Tuff of Nye and Esmeralda Coun- ties, Nevada: Art. 126 in U.S. Geol. Survey Prof. Paper 475—D, p. D124—D127. Nockolds, S. R., 1954, Average chemical compositions of some igneous rocks: Geol. Soc. America Bull, v. 65, p. 1007-— 1032. Peacock, M. A., 1931, Classification of igneous rock series: Jour. Geology, v. 39, p. 54—67. Rittmann, A., 1952, Nomenclature of volcanic rocks: Bull. Volcanology, ser. II, v. XII, p. 75—102. (E. A. Vincent, translator), 1962, Volcanoes and their activity: New York, Interscience, 305 p. Stark, J. T., 1963, Petrology of the volcanic rocks of Guam: U.S. Geol. Survey Prof. Paper 403-0, p. 01—032. Thornton, C. P., and Tuttle, O. F., 1960, Chemistry of igneous rocks, I. Differentiation index: Am. Jour. Sci, v. 258, p. 664-684. Waters, A. C., 1955, Volcanic rocks and the tectonic cycle, in Poldervaart, Arie, ed., Crust of the Earth: Geol. Soc. America Spec. Paper 62, p. 703—722. Williams, Howel, Turner, F. J ., and Gilbert, C. M., 1954, Pe- trography: San Francisco, W. H. Freeman, 407 p. GEOLOGICAL SURVEY RESEARCH 1964 PRELIMINARY REPORT ON THE STRUCTURE OF THE SOUTHEAST GROS VENTRE MOUNTAINS, WYOMING By WILLIAM R. KEEFER, Denver, Colo. Abstract—The Gros Ventre Mountains are an asymmetric anticlinal uplift, steep and faulted along the southwest margin. The range lies between structures typical of Laramide deforma— tion (Late Cretaceous and early Tertiary) in central Wyoming and those of late Tertiary deformation (post-Early Pliocene) in northwestern Wyoming. Tentative interpretations are that the Gros Ventre Mountains and adjacent Hoback Basin were formed during the Laramide and were modified by later movements. The Gros Ventre Mountains of northwestern Wyom- ing (fig. 1) lie amidst large, diverse, complex tectonic features formed at different times. The southwest edge of the range is within a. mile of the easternmost thrust sheets of the overthrust belt. Farther south the range is bounded by the synclinal Hoback Basin, which forms the northern extension of the Green River Basin and is one of the deepest structural depressions in Wyoming. Structural elements to the east, in central Wyoming, were formed in latest Cretaceous and early Tertiary times, whereas others, to the west and north— west in Jackson Hole and the Teton Mountains, were formed in late Cenozoic time. The time of maximum Gros Ventre uplift has, therefore, been a problem of some interest. Although much is already known about the geology of the region (Nelson and Church, 1943; Richmond, 1945; Baker, 1946; Horberg and others, 1949; Love and others, 1951; Eardley, 1951, p. 320— 325; Love, 1956a, 1956b; Dorr, 1956, 1958; Berg, 1961), critical data are still too meager to permit recognition of each tectonic event. The present paper is based on the detailed field study of approximately 125 square miles of the southeast end of the range and an adjacent narrow strip of the Hoback and Green River Basins (figs. 1 and 2). STRATIG‘RAPHY Strata exposed in the southeastern Gros Ventre Mountains range in age from Ordovician to Late Cre- taceous (fig. 2) and are about 7,500 feet thick. Cam— brian rocks underlie the area and crop out to the northwest, where they are 1,250 feet thick. The for- mations are described by Blackwelder (1918), Rich- 110° I — I ' YELLOWSTONE I I ’1 l E 3 l NATIONAL \S’PARK \ C: s 4 - ': t 1.—. -—-.% WJ s o“ ’1 M 2, a a 44° ‘ i = 3, /// ’7 U) § ; / 0/, « - | .E \\\ § /// L A b s a r o k a I 3 :— 2 3 ///l g 6 /// g 3 o :: Mt Leidy ; 94. 4/0,, 0 S I .: Z s 9/ M o u n t a i n s I 2 0° c é and 0/1,, ////,,,,I L O : ’ / :— ll) '_ ' k / // c : x i Pmyon Pea 9/ "Fe 00"“, 8 C 8 ’2 . /// ’7 // '1, 0% 3 \\\\II/I Highland$\¢ ”II”? 86 /// a \ II, E // /’//,, I4, S § Q’s //// c"////// /////Im, \ // \\ \ 47 o / t . /// ,'\\\\\ I III ’////////S 0 °b ,I/ I C ’I) ”II“ /4 g o e / : : . 54 9/ °’$,~ ’78}. ///l :— ///////// fi/l’sr 4 / . : " ////I” 05‘ : ’4 I L; 7/ 2 \ L1, u////// as]. IE 3 E ////, 5 fl) 4/ r’ o I: .— 3 I. o ’H// E E E ii 3 Hoback : 5 47 ////// Q a n: m 5. Basin : : o ,9 5, D—Il LLI ’, O — Q /’ 3 > ’- \ : r; V I o 2 \\\\\‘ . o_ 2‘ e, 43.. .11“ Green River : 9/0 E Basin 2 s _ l I \\ 1 ’1’ O 10 20 30 MILES L__;__I__I FIGURE 1.—Index map showing location of mapped area (diag- onal pattern) with respect to major physiographic and structural features in northwestern Wyoming. The over- thrust belt includes the Wyoming, Salt River, and Hoback Ranges. U.S. GEOL. SURVEY PROF. PAPER 501-D. PAGES D22—D27 D22 KEEFER mond (1945), Love and others (1948, 1951), Horberg and others (1949), Wanless and others (1955), and Love (1956a). Cretaceous rocks younger than the Frontier Forma- tion are extensively exposed along the northeast flank of the range, where they are about 8,300 feet thick (Love and others, 1948, p. 25—41; Love, 1956a, p. 79— 83). Along the southwest flank, about 20 miles north— west of the map area, the post—Frontier Cretaceous sequence may be nearly 10,000 feet thick (J. D. Love, oral communication, 1963). Comparable thicknesses of these strata probably are present in the deep part of the Hoback Basin along the southwest edge of the map area (fig. 2). Tertiary rocks in the Hoback Basin include the Hoback Formation of Paleocene and early Eocene age, and the Pass Peak Formation of probable middle Eocene age, both formations of Horberg and others (1949). The Hoback Formation is exposed across the central part of the basin, where it is more than 15,000 feet thick and consists chiefly of fine—grained sandstone, siltstone, and shale (Dorr, 1956, p. 102). The Pass Peak Formation crops out along the south— west edge of the map area (fig. 2); it is about 1,500 feet thick and composed of massive conglomerate beds with minor amounts of sandstone and shale (Dorr, 1956, p. 106). The conglomerate consists almost en— tirely of rounded boulders of Precambrian quartzite resembling, and undoubtedly derived from, those in the Pinyon Conglomerate of Paleocene age now ex— posed along the north side of the Gros Ventre Moun— tains (Love, 1956a, p. 84). STRUCTURE The Gros Ventre Mountains were formed primarily from a broad asymmetric anticline that is steep and faulted along its southwest flank. The major boundary fault is the Cache thrust fault which has been traced from the southwest corner of the range southeastward along the entire mountain front (Dorr, 1958, p. 1218; Love, 1956b, p. 141). Within the range proper, exten- sive vertical faults, trending partly west and partly northwest, divide the uplift into three major structural segments (Nelson and Church, 1943, fig. 7). This re— port concerns the easternmost of these segments. At its southeast end the main anticlinal structure of the Gros Ventre Mountains plunges 10° to 15° east and southeast, and is separated from the north end of the adjacent Wind River Mountains, along the east slope of the Green River valley, by a series of shallow north-trending folds (Richmond, 1945; Skinner, 1960). D23 The crest of the uplift is remarkably flat over broad areas, although subsidiary folds are evident (fig. 2). Strata along the northeast flank dip 5° to 10° north- east. Normal faults cut the crest of the uplift in the cen- tral part of the map area (fig. 2). The dominant trend of the faults is northeast, but a secondary set trends northwest at an oblique angle of about 120°, nearly parallel to the major structural trend of the range. Displacements range from less than 100 feet to as much as 1,250 feet; there is no consistent pattern regarding which sides were upthrown or downthrown. Whether the Pass Peak Formation is involved in the faulting along the Cache fault has been a matter of controversy. Horberg and others (1949, p. 198, pl. 2) show the fault terminating before it reaches the south- east margin of the Gros Ventre Mountains, whereas Dorr (1958, p. 1218) and Eardley (1951, figs. 182 and 183) indicate that the Pass Peak was overridden in this region. Though the fault surface was not ob- served during the present investigation, the following field relations suggest strongly that the contact be- tween the Pass Peak Formation and older rocks is tectonic rather than sedimentary: ( 1) the contact appears to be very sharp and linear in most places, showing little irregularity suggestive of overlap; (2) residual debris from the highly conglomeratic Pass Peak strata was not found on adjacent slopes of the older rocks examined north of the contact; (3) con- versely, there appears to be little debris locally derived from these older rocks in the Pass Peak; and (4) in places, strata of the Pass Peak are turned up sharply near the contact. There is little doubt that the next older Hoback Formation was overridden by the upper plate of the Cache fault. Approximately 15,000 feet of Hoback beds exposed on the southwest limb of the Hoback Basin syncline dip toward the Gros Ventre Mountains, but do not emerge at the surface on the opposing (northeast) limb. Maximum structural displacement between the trough of the Hoback Basin and the crest of the Gros Ventre uplift is about 35,000 feet, much of it having taken place along the Cache fault (fig. 2). The fault surface dips about 45° northeast Where observed by J. D. Love (oral communication, 1963) northwest of the map area. The Elbow Mountain fault (Nelson and Church, 1943, p. 158) is a major fracture which extends west-north— west through the central part of the area, nearly paral- lel to and 1 to 3 miles north of the Cache fault; at the T 2 STRUCTURAL GEOLOGY D24 "M LCM ,OTeOTT spoq poun4.1040 o dip pue aying spoq Jo dip pus axing Im posiafur a.aym poysng sexe PJOA ourpudg ouronuy aioym porzop Ajomurzoiddn acoym poysng coprs umoiy2dn uo neg 3sn44y, nnnnn in alos aon amen ard apps unowypumop uo 110g pwb wig Arorpuzzoaddn paysng ine; reagan paz, acsym poysng iSTeOTT 'M ZH 'H NVIUBWYO dIA0di0 [ NYINOA3G any -SISSI W 7-3 NVINYA Nyvidais NY! snod341N084vD -TASNN3d (>a DISSVIHL DISSYanr A AUVNUILVNO suopoos ut uray;ed ; (6F6T) pus S1oq4of JO ; Ruo $u02998 up Syo01 UELIQUEOOIq Ajuo $401,008 up pue son #4. , suoneurt04 1oyStg pus 4q1e(G suoneumo,, uopsury pus 2d ertoydsoug -o Apoomurg pun aoppmbnyy ny. suompuso, 3066npf pun 'Buridg wnsdhs 'counpung 'nf syoo1 orsseELL], puse otsse inp yage SST uostLiop; pue o suonpeuL1o,f pue 'Amopy Ajuo suon098 up Jor} UOI,J-48504 f Ajuo up , uoneuno, yoeqopq brig | uoneunoy yeaq sseq suomoas ur unoys 100 sqrsodop [erotying NOILYNYT4X3 D25 LoaAimg 'g' wou; aseq 10 4q sdeta poysttqndun wor; suontppe YIM (20-0061 , 'ey;oipuy 'g 'G pus 419fooy 'Y 'M 4q Surddewr orsojoan KEEFER ng pue nod 13A37 v3S 'sutequnopy arjuoj sour Wojsgaygnos ay} yo suomoas pus deur arSojoan-'z ZHADIA ng pue nog NIYVLNNOW moST13 Ni aN38 LINnVv4 NIYVLNNOW moO#73 v re. ng pue nod I2 7 477 r 227 A HA- r W mid \ Re wan rani W M W s wi 8 atid & summed W 7,7-,000°'0t- ran wu mo 8 B: \ \ |_13A37 % v3S cee Th fooodfi D26 west edge of the area, however, it turns abruptly north- ward. This feature bounds the south and west sides of the easternmost structural segment of the Gros Ventre Mountains. Spectacular scarps rise 1,500 to 2,000 feet in the upthrown block north and east of the fault and form a prominent "sawtooth" ridge. One segment of the fault extends from the southwest corner of the upthrown block south to the Cache fault. Strata in the upthrown block turn down sharply against the Elbow Mountain fault in places along the west edge of the map area, but toward the southeast little or no drag folding is evident. Maximum structural displace- ment is about 3,000 feet. Reliable dips were not ob- served along the fault plane, but it may be nearly vertical. Horberg and others (1949, pl. 2) considered it to be a high-angle reverse fault, although they meas- ured a 65° southward dip on slickensided surfaces along the trace of the fault near its southeast end. The pattern of faulting and the steepness of the scarps suggest, but do not prove, that the Elbow Mountain is a normal fault. The fault shown at the northwest corner of the map (fig. 2) is the eastern extension of the Shoal Creek fault which forms the south side of the central struc- tural segment of the Gros Ventre Mountains. This fault extends westward for about 6 miles beyond the area shown on figure 2, thence it swings sharply north for another 6 miles, thus resembling the trace of the Elbow Mountain fault (Nelson and Church, 1943, fig. 7). The Shoal Creek fault may also be nearly vertical, and undoubtedly is genetically related to the Elbow Mountain fault. INTERPRETATION OF STRUCTURE AND GEOLOGIC HISTORY Major diastrophism in the Gros Ventre Mountains has been variously dated as Late Cretaceous to late Tertiary. Horberg and others (1949, p. 207-208), for example, conclude that uplift must have begun in Late Cretaceous time because the range appears to have formed a buttress against which the eastward-moving thrust sheets of the overthrust belt impinged (fig. 1). Dorr (1958, p. 1239) interprets the initial movements to have been in post-early Eocene time, based on rela- tions observed in the Hoback and Pass Peak Forma- tions. Eardley (1951, p. 325) places the major uplift in post-middle or late Eocene time, because the Pass Peak was overridden by the Cache fault. In the west- ern part of the range, Love (1956b, p. 145; oral com- munication, 1963) has found that significant move- ments took place in early Eocene time and again in post-early Pliocene time. Pre-Paleocene folding is STRUCTURAL GEOLOGY indicated in some places along the northeast margin of the Gros Ventre Mountains by an angular discord- ance between the Pinyon Conglomerate and older rocks (Love and others, 1951). Major structures in central Wyoming are interpreted by Keefer and Love (1963) to have formed by (1) basin subsidence in Late Cretaceous time, continuing through all of Paleocene and early Eocene time; and (2) progressive folding of the mountain ranges during or at the close of the Cretaceous, culminating in pro- nounced uplift along high-angle reverse faults at the end of Paleocene time or during earliest Eocene time. Basin sinking was as important tectonically as moun- tain uplift; in large segments of some basins, subsi- dence equalled, or exceeded, uplift of the adjacent mountains. Events in the mapped area were analogous in part to those in central Wyoming. The Hoback Basin be- gan to sink in Late Cretaceous time, and subsidence was virtually continuous through all of Paleocene, early Eocene, and possibly middle Eocene times. The actual downward movements probably exceeded 20,000 feet in the deepest parts of the basin. The Gros Ventre Mountains probably were folded early in Tertiary time, but it is doubtful that the range stood very high with respect to the Hoback Basin before major uplift in probable middle Eocene time; Pinyon strata (Paleocene) were then stripped off the area now occupied by the mountains and re- deposited in the Pass Peak Formation. After deposi- tion and lithification, perhaps as late as post-early Pliocene time, the Pass Peak was overridden by the upper plate of the Cache fault. Though there is no direct evidence, it seems likely that considerable move- ment must also have taken place along this major boundary fault during uplift of the range at the be- ginning of Pass Peak time. Whether the Elbow Mountain and Shoal Creek faults originated in early Tertiary time is likewise conjectural. The steepness and fresh appearance of the fault-line scarps, however, suggest that the most significant movements along these faults may have taken place in late Tertiary time, concomitant with extensive faulting in Jackson Hole and the Teton Mountains to the west. Available data thus suggest that the Gros Ventre Mountains and Hoback Basin were well outlined as positive and negative tectonic units, respectively, dur- ing Laramide deformation, but that the mountains may have been modified considerably by late Tertiary movement. KEEFER REFERENCES Baker, C. L., 1946, Geology of the northwestern Wind River Mountains, Wyo.: Geol. Soc. America Bull., v. 57, p. 565- 596. Berg, R. R., 1961, Laramide tectonics of the Wind River Moun- tains, in Wyoming Geol. Assoc. Guidebook 16th Ann. Field Conf., 1961 : p. 70-80. Blackwelder, Eliot, 1918, New geologic formations in western Wyoming: Washington Acad. Sci. Jour., v. 8, p. 417-426. Dorr, J. A., Jr., 1956, Post-Cretaceous geologic history of the Hoback Basin area, central western Wyoming, in Wyoming Geol. Assoc. Guidebook 11th Ann. Field Conf., 1956: p. 99-108. 1958, Early Cenozoic vertebrate paleontology, sedimen- tation, and orogeny in central western Wyoming: Geol. Soc. America Bull., v. 69, p. 1217-1248. Eardley, A. J., 1951, Structural geology of North America: New York, Harper and Bros., 624 p. Horberg, C. L., Nelson, V. E., and Church, Victor, 1949, Struc- tural trends in central western Wyoming: Geol. Soc. America Bull., v. 60, no. 1, p. 183-215. Keefer, W. R., and Love, J. D., 1963, Laramide vertical move- ments in central Wyoming: Wyoming Univ. Contr. to Geol- ogy, v. 2, p. 47-54. Love, J. D., 1956a, Cretaceous and Tertiary stratigraphy of the Jackson Hole area, northwestern Wyoming, in Wyo- *% 742-652 O-64--3 D27 ming Geol. Assoc. Guidebook 11th Ann. Field Conf., 1956: p. 76-94. Love, J. D., 1956b, Summary of geologic history of Teton County, Wyoming, during Late Cretaceous, Tertiary, and Quater- nary times, in Wyoming Geol. Assoc. Guidebook 11th Ann. Field Conf., 1956 : p. 140-150. Love, J. D., and others, 1948, Stratigraphic sections of Jurassic and Cretaceous rocks in the Jackson Hole area, northwest- ern Wyoming: Wyoming Geol. Survey Bull. 40. 1951, Geologic map of the Spread Creek-Gros Ventre River area, Teton County, Wyoming: U.S. Geol. Survey Oil and Gas Inv. Map OM 118. Nelson, V. E., and Church, Victor, 1943, Critical structures in the Gros Ventre and northern Hoback Ranges, Wyoming: Jour. Geology, v. 51, no. 3, p. 143-166. Richmond, G. M., 1945, Geology of the northwest end of the Wind River Mountains, Sublette County, Wyoming: U.S. Geol. Survey Oil and Gas Inv. Map 31. Skinner, R. E., 1960, Tectonic elements of the northern Green River area of Wyoming, in Wyoming Geol. Assoc. Guide- book 15th Ann. Field Conf., 1960: p. 86-88. Wanless, H. R., Belknap, R. L., and Foster, H. L., 1955, Paleo- zoic and Mesozoic rocks of Gros Ventre, Teton, Hoback, and Snake River Ranges, Wyoming: Geol. Soc. America Mem. 63. GEOLOGICAL SURVEY RESEARCH 1964 PRE-FALL RIVER FOLDING IN THE SOUTHERN PART OF THE BLACK HILLS, sOUTH DAKOTA By GARLAND B. GOTT, Denver, Colo. Abstract.-Outcrop and drill-hole data show discordant rela- tions between the Fall River Formation and the underlying Lakota Formation, both of Early Cretaceous age. This indi- cates that structural movement was contemporaneous with deposition of the Lakota Formation. Subsurface data indicate a pre-Fall River structural dome 744 miles north of Edgemont, S. Dak. A small quantity of petroleum produzsed from the Minnelusa Formation of Pennsylvanian and Permian age at the Barker dome, Custer Couty, S. Dak. (Gries, 1964) attracts attention to small structural traps in pre-Cretaceous rocks of the southern Black Hills. Some of these structures are concealed by dis- cordant post-Jurassic rocks. Along the southwest margin of the Black Hills up- lift the regional dip averages about 3° SW. Small anticlinal folds, such as the Barker dome, occur in some places. Elsewhere the structural irregularities consist of a steplike series of terraces and monoclines of low relief. Locally, small faults exist that are prob- ably related to subsidence. Detailed studies (Gott and Schnabel, 1963, p. 170 and pl. 14) of the formations in the Lower Cretaceous Inyan Kara Group, consisting of the Fall River For- mation and the underlying Lakota Formation, have brought out evidence that structural readjustments were in progress at the time that the Lakota Forma- tion was being deposited. Although most of the fold- ing occurred during post-Fall River time, discordance of the attitude of the Fall River Formation with all the major units of the underlying Cretaceous Lakota Formation indicates that some of the folding had occurred before the end of Lakota time. This folding resulted in the deposition of a relatively thick sequence of rocks in the structural troughs and a thin sequence of rocks on the structural highs. The thickness of the Lakota thus ranges from a minimum of about 325 feet to a maximum of about 650 feet. Interpretation of subsurface data indicates a pre- Fall River structure located about 7%, miles north of Edgemont, S. Dak., in see. 26, T. 7 S., R. 2 E. It is domal in shape and is concealed by discordant beds of the Lakota and Fall River Formations. The top of the Morrison Formation of Jurassic age has about 40 feet of closure (fig. 14), while the base of the Fall River Formation of Cretaceous age has none (fig. 12). One drill hole on a pre-Fall River anticline in the area penetrated the Lakota and Morrison Formations and the Redwater Shale Member of the Sundance Forma- tion of Jurassic age. At that point the total maximum thickness of about 100 feet of Morrison Formation was present. This indicates that there was little, if any, post-Morrison and pre-Lakota erosion and, therefore, little, if any, folding prior to the beginning of Lakota time. Folding apparently continued through Lakota time, resulting in pronounced depositional and struc- tural troughs. It is possible that this pre-Fall River folding was part of the structural deformation accompanying the beginning of the Black Hills uplift. The post-Fall River Cretaceous marine invasion of the Black Hills, however, suggests that the area was more likely up- lifted at the end of Cretaceous time. Folding ac- companying the uplift was then superimposed on the earlier folding. Outcrop data and logs of core holes supplied to the U.S. Geological Survey by the U.S. Atomic Energy Commission were the basis for the structural inter- pretation. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D28-D29 D28 coTr D29 37900 3821\ 3862 \ e__ 4554 t. c 0 260° 7 3ns® A / 51 its 0 U 36" . 3622, 3594 A. TOP OF MORRISON FORMATION 0 SOUTH DAKOTA Area of la report 1.-Structure-contour maps of part of the Edgemont NE quadrangle, Fall River County, S. Dak. \ 3 04g, On" 1100% ©4078 ©4083 R: 2 €. B. BASE OF FALL RIVER FORMATION } MILE EXPLANATION U ror rr.!!! D Fault D, downthrown side; U, upthrown side Dot, elevation of top of the Morrison Formation or base of the Fall River Formation in drill hole ; X, elevation of exposed base of the Fall River Formation. Contours dashed where inferred. Contour interval 25 feet; datum is mean sea level. REFERENCES Gott, G. B., and Schnabel, R. W., 1963, Geology of the Edge- mont NE quadrangle, Fall River and Custer Counties, South Dakota: U.S. Geol. Survey Bull. 1063-E. Gries, J. P., 1964, Barker dome oil field, Custer County, South Dakota: The Mountain Geologist, v. 1, no. 1, p. 48. 5b GEOLOGICAL SURVEY RESEARCH 1964 CHINLE FORMATION AND GLEN CANYON SANDSTONE IN NORTHEASTERN UTAH AND NORTHWESTERN COLORADO By F. G. POOLE and J. H. STEWART, Denver, Colo., Menlo Park, Calif. Work done in cooperation with the U.S. Atomic Energy Commission Abstract.-The Chinle Formation of Late Triassic age is com- posed of six lithologic units, in ascending order: (1) Gartra Member (new usage), (2) mottled member, (3) ocher siltstone member, (4) a local sandstone and conglomerate member, (5) red siltstone member, and (6) upper member. The ocher silt, stone is correlated with the Popo Agie Member of the Chug- water Formation of Wyoming, and the red siltstone is corre- lated with the Church Rock Member of the Chinle of southeast Utah. A regional angular unconformity occurs at the base of the Chinle throughout the area and at the top of the Chinle in northwestern Colorado. The Glen Canyon Sandstone (new usage) of Late Triassic and Early Jurassic age overlies the Chinle in northeastern Utah and part of northwestern Colorado. The Chinle Formation of Late Triassic age and the Glen Canyon Sandstone of Late Triassic and Early Jurassic age are widely exposed in northeastern Utah and northwestern Colorado. In northeastern Utah, exposures of the Chinle and the Glen Canyon are re- stricted to the flanks of the Uinta Mountains (fig. 1). In northwestern Colorado, the Chinle is exposed in the eastern part of the Uinta Mountains, along the mar- gins of the Park and Gore Ranges, around the White River Plateau, along the southern extension of the Grand Hogback, and near State Bridge, Wolcott, East Brush Creek, Basalt, and Aspen (fig. 1). In north- western Colorado, the Glen Canyon Sandstone is ex- posed in the eastern part of the Uinta Mountains and along the northern and western flanks of the White River Plateau. Study of these exposures has led to the summary of the stratigraphic character and relations presented here, and is part of a regional investigation of the Chinle Formation and related strata of the Colorado Plateau region. Most of the information presented in this paper was collected during 1955-57, and concerns work done on behalf of the U.S. Atomic Energy Com- mission. CHINLE FORMATION The Chinle Formation unconformably overlies red beds of Early Triassic age in the Uinta Mountains; red beds of Early Triassic and(or) Permian age around the White River Plateau, along the southern extension of the Grand Hogback, and in the vicinity of State Bridge, Wolcott, and East Brush Creek; and red beds of Permian and possibly Pennsylvanian age along the margins of the Park, Gore, and Tenmile Ranges, and in the vicinity of Basalt and Aspen. In general, the Chinle rests on progressively older strata eastward from the Uinta Mountains to the Park, Gore, and Tenmile Ranges. The Glen Canyon Sandstone appears to conformably overlie the Chinle Formation in the Uinta Mountains of northeastern Utah and northwestern Colorado, whereas in the vicinity of the White River Plateau, it overlies the Chinle with apparent unconformity. South and east of Meeker, Colo., beyond the wedge- edge of the Glen Canyon Sandstone, the Chinle is unconformably overlain by the Entrada Sandstone or equivalent strata of Late Jurassic age. The Chinle Formation in northeastern Utah and northwestern Colorado is composed of six members (figs. 2, 3), in ascending order: (1) a unit of light- colored sandstone and conglomerate called the Gartra Member (new usage); (2) a unit of purple and red U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D30-D39 D30 D31 POOLE AND STEWART "4x99 uf possnostp sory[ed01 put 'eje1}s pus uo suo ay} Jo (yo%Jq) sdoaojno Surmoys put UE} Jo deur xapay-'1 » 6€ [ _ T t r t ) SIJTIW OOT oS 0 4 awwsUV/V Ine ©20204 a rw. ___ yooug uoriabpst _ T yeseg goo) fo Te % yooip I 5 flu. € fimsmflafi‘m ) ssunudg O | 5 - (» 7 - urequnow #., Q2" 7 zouum pue pdr ~* aoug |< \M M 3; p09 1 # ay > @ . Aw cw & 110910 M M3340 I f merest O. uofuep : _ 3 > 9 . "aus NiSyg § 5g ¥ 7 3JDONV3OId I l fs" >.. weal Av f ies c t H si Hth ,. n " Meo" \" 4 | sSuudg '~ .A z 2% \Boxoop; ng punoSdurep - nyd[ng 104 - sseg-eion |/ / ndd ga gaa 1 \- £1p8uey | yseussgey, fl > va I 30049 i-, ._ - 30949 a00q 120 WBM | L yoor Burddriq 1 Z “nu £ 30049 \—\ L itr z x= qusupuoddosiq J ol erecta s a a- A A ¥ - *--. o M #: ,- sSuudg I //uw:_:fi yeoqureagg MRS- urequnow sigs; : 7 ssoip 30 aje : .w\ .ll UNVSONIC fl \—_L \ xwwsb/ iy worudaA - f 4 - T / . sj ___ _Goyuolor ___I L L_ Ln _ f __. "@ olf he f DNINOA M | | | +901 LOT +801 +601 D32 LAKE FORK RIVER BRUSH CREEK CLIFF CREEK MILLER CREEK STRATIGRAPHY AND PALEONTOLOGY SHEEPHORN CREEK OAK RED RIDGE CANYON A l&----- 50 MILES------#-20 MILES-4-- 28 MILES -#<------ 55 MILES MILES------¥-15 Ml—fA GLEN CANYON Upper member CHINLE FORMATION MOENKOPI AND OLDER SANDSTONE FORMATION ROCKS MORRISON _ FORMATION AND CURTIS _ FORMATION UNDIVIDED siltstone member Gartra Member 200 FEET 100 10 20 MILES Figaur® 2.-Generalized west-to-east section, A-A', showing relation of members within the Chinle Formation. Vertical exaggeration 660. shown on figure 1. mudstone, mottled siltstone, and mottled sandstone re- ferred to as the mottled member; (3) a unit of ocher siltstone, and some red siltstone, called the ocher siltstone member; (4) a local unit of gray, pink, and brown sandstone, mudstone, and mudstone-limestone pebble conglomerate referred to as the sandstone and conglomerate member; (5) a unit of red siltstone, and minor amounts of sandstone and siltstone-limestone pebble conglomerate, called the red siltstone member; and (6) a unit of orange, brown, and gray sandstone and red and green mudstone, called the upper member. Some of these units are local; others are widespread. The Gartra Member and mottled member are persist- ent throughout the region, whereas the other siltstone and upper members occur only in the Uinta Moun- tains, the red siltstone member in the eastern Uinta Mountains and throughout northwestern Colorado, and the sandstone and conglomerate member only locally in the easternmost Uinta Mountains. Gartra Member The Gartra Grit Member of the Stanaker Formation was named and described by H. D. Thomas and Krueger (1946) for a thin unit within Upper Triassic Location of section strata in the Vernal area of northeastern Utah. These names were not generally accepted because the well- established Colorado Plateau names Shinarump Con- glomerate and Chinle Formation were already in use for these strata in northeastern Utah and northwestern Colorado (Powell, 1876; C. R. Thomas and others, 1945). Subsequent to Thomas and Krueger's work in the Uinta Mountains, geologists working there con- tinued to use the names Shinarump Conglomerate and Chinle Formation (Huddle and McCann, 1947; Kin- ney and Rominger, 1947; Kinney, 1951, 1955; and Hansen, 1955). Regional stratigraphic work, however, has shown that the Shinarump is a member of the Chinle Formation that does not extend north of cen- tral Utah (Stewart, 1957) and that the Gartra is confined to the northern and northeastern parts of the Colorado Plateau (fig. 4). As the Gartra and Shinarump probably are not correlative and their rela- tive age is uncertain, the name Gartra is preferred for the basal sandstone and conglomerate unit of the Chinle Formation in the area described in this paper. The lithologic term "grit" is not part of the formal name in the report area. The name Chinle Formation is retained for Upper Triassic strata as it is well estab- POOLE AND STEWART D33 VERMILION CROSS OAK SOUTH CANYON ASPEN BOREAS RED CREEK MOUNTAIN RIDGE CREEK PASS _ HILL B MILES-HK------52 MILES------$---34 MILES---#$----39 MILES HC 50 MILES Ar‘r‘M'lfsg Fis MORRISON FORMATION AND GLEN CANYON SANDSTONE CURTIS FORMATION UNDIVIDED z w— o Upper member F <| [ 4 g fisher siltstone member 9 Red siltstone member A G 7 &) 21 a Sandstone and «* x artra conglo merate o Member member / Gartra Member 2 ge m & a otisy is Gartra Member _ ,/ \ 5 Gartra Member 200 FEET MOENKOPI FORMATION é)” A £? 100 MAROON FORMATION AND OLDER rocks & 10 _ 20 mires §. Figur® 3.-Generalized northwest-to-southeast section, B-B', showing relation of members within the Chinle Formation. Location of section shown on figure lished and the Chinle Formation of northeastern Utah and northwestern Colorado can be demonstrated to be continuous with part of the Chinle Formation in the central part of the Colorado Plateau. Hence, the name Stanaker Formation is not used in this report. The Gartra Member is present throughout northeastern Utah and most of northwestern Colorado. Quartzose sandstone and conglomerate lenses within the Temple Mountain Member (Robeck, 1956) of the Chinle For- mation in the San Rafael Swell, south of the Uinta Basin, are lithologically similar to the Gartra Member. The Gartra Member consists mainly of light-colored sandstone, conglomeratic sandstone, and some con- glomerate. Locally the member is stained purple and red. The sandstone is composed dominantly of sub- angular to well-rounded grains and granules of quartz, some feldspar, and sparse chert and quartzite; the matrix and cement consist of clay minerals, calcite, and locally silica (R. A. Cadigan, written communication, 1958). The gravels are subrounded to well-rounded pebbles and scattered cobbles composed of quartz, some chert and quartzite, and sparse feldspar, quartz- ose sandstone, and limestone. In general, the maxi- mum gravel size increases eastward. The maximum 1. Vertical exaggeration X660. measured diameter of quartz gravels ranges from about 1 inch at Farm Creek in Utah to about 3 inches at Red and White Mountain, East Brush Creek, Deer Creek, and Boreas Pass in Colorado. The Gartra is cross stratified in most areas, and contains silicified log fragments. The Gartra Member varies widely in thickness, though in northeastern Utah the member is generally 20-50 feet thick. It is generally only 5-30 feet thick in northwestern Colorado (see accompanying table). Thickness is greatest where the member fills channels cut into the underlying rocks. The Gartra is discon- tinuous, especially in northwestern Colorado; where it is absent the mottled member is the basal unit of the Chinle. In the exposures examined, a sharp erosional contact was noted between the light-colored Gartra Member and the underlying red beds. The contact is undulat- ing and marked by small channels and scours. Beds above and' below the contact appear concordant at all outcrops, and the contact is an apparent erosional dis- conformity; however, eastward the Gartra rests on older and older beds and the contact is clearly a re- gional angular unconformity. D34 EXPLANATION 7 Moss Back Member Gartra Member § , o 5 A* wf o 0° a $ 353 Shinarump Member +C CHINLE FORMATION STRATIGRAPHY AND PALEONTOLOGY WYOMIN\G Overlap of Moss Back ai air Deva ys and Shinarump *y +l a ys n "o o 1 Members ! COLORADO ARIZ | NEW MEXICO 0 50 100 150 MILES & 315 MILES >| i 1000' 500 Gartra Member Fiaur® 4.-Map and diagrammatic section showing inferred depositional limits and stratigraphic relations of Moss Back, Gartra, and Shinarump Members of the Chinle Formation. X 416. The mottled member is intimately related to the Gartra Member; the contact between them is placed at the top of the rather continuous light-colored sand- stone and conglomerate that extends to the base of the Chinle Formation. The contact is gradational and intertonguing. Gartra-like sandstone and conglomer- ate occur as lenses within the mottled member, es- pecially in northwestern Colorado, and tongues of mottled rock extend into the Gartra. The general decrease in grain size toward the west and the westerly dip of cross strata indicate that the Gartra Member was deposited by westerly flowing streams (Poole, 1961). These streams probably origi- nated in central and possibly west-central Colorado. The source rock was probably older red beds, such as the Maroon Formation, and exposed lower Paleozoic rocks and Precambrian igneous and metamorphic rocks in central and west-central Colorado. Vertical exaggeration Mottled member The mottled member is persistent throughout north- eastern Utah and northwestern Colorado. The mot- tled member north and east of the Uinta Basin may be equivalent to part or all of the Temple Mountain Member (Robeck, 1956) of the Chinle Formation in the San Rafael Swell (south of Price, Utah). The mottled member is made up of purple and red mudstone and mottled siltstone and sandstone. The purple and red mudstone consists predominantly of silt and clay and variable amounts of sand. Dominant components of the mottled siltstone and sandstone are subangular to well-rounded grains of quartz, some feldspar, chert, quartzite, mica, and sparse tuff (?); the matrix and cement consist of silica, clay minerals, calcite, and iron oxide (R. A. Cadigan, written com- munication, 1958). Iridescent purple iron-oxide blebs, bedded chert, and jasper also are abundant. Many of POOLE AND STEWART the sandstone layers are very coarse grained and con- glomeratic. The gravels are composed of subrounded to rounded quartz and chert. Overall the member generally is crudely stratified, but the mottled siltstone and sandstone units locally are well bedded. A few of the silty and very fine to medium-grained sandstone beds are crossbedded. The member consists mainly of mottled sandstone at Boreas Pass in Colorado, whereas elsewhere it is mostly sandy mudstone. The member is absent locally, as at Vermilion Creek and East Brush Creek. The mottled member is gen- erally 30-50 feet thick in northeastern Utah and 20-40 feet thick in northwestern Colorado (see table). The mottled member is overlain by the ocher silt- D35 stone member in the Uinta Mountains of northeastern Utah and northwestern Colorado, and by the red silt- stone member in northwestern Colorado (fig. 2). The contact between the mottled member and ocher silt- stone member is difficult to locate in many parts of the central Uinta Mountains where a thin reddish mud- stone characteristic of the basal part of the ocher siltstone member is well developed and rests on similar rocks of the mottled member. is marked by a subtle color change from purple and red strata of the mottled member to reddish strata of the basal part of the ocher siltstone member. mottled member overlies the Gartra Member or pre- Chinle strata where the Gartra is missing. The contact generally The Thickness of Chinle Formation and its members in northeastern Utah and northwestern Colorado [P, present at section, but not measured. PP, probably present, but not differentiated; unit occurs either as a wedge edge or as thin tongues in adjacent unit. A, absent at section, but present nearby. NP, not present in area. NE, not exposed, but probably present in areal Thickness (feet) Members County Locality (fig. 1) Total formation Ocher Sandstone Red Gartra Mottled siltstone and con- siltstone | Upper glomerate Utah Duchesne. ...... Lake Fork River. 443+) 23-100 68 215 NP PP 137 Uintah... ../... vernal (Brush 340 65 19 122 NP PP 135 Red o ae sma 287 53 P P P P 110 Chit Creek: sis lcd _? 212 A 50 68 PP 36 59 Colorado Moflat:z::-...:... Dripping:Rock Creek -_... P NE NE NE NP T 18 Miler L- .u _ slc sil ue bd ou aun 266 21 52 66 NP 127 A Disappointment ___} 259 A 42 21 53 143 1 Valo of: Tears. . 0 ald 291 A 78 19 83 100 10 Crogs Mountain.... ...l cucu. 244+ NE NE 10+ 115 100 20 Vermilion 20022. 246 110 A 64 NP 67 6 Rio Blanco. ...... Oak: Ridge.. . cA s 388 A 42 NP NP 346 NP Gatheld .._ _ Cast Rifle Creek. P 6-15 P NP NP P NP Main'PIk u} 1 311 0-5 P NP NP P NP Routh Canyon _.. t. 226 NP 17 NP NP 209 NP Fourmile Creek.. l 00s} 100+ PP 20+ NP NP 80 + NP Edgerton Creok: LPC s 60+ PP 20+ NP NP 40 + NP PitKihi........... North Thompson Creek: 2.._.,_.-_L.:_lzl.l NP? |- Julio MADE c lcs Potato Bill: Creek Ely NP. 1. ._.. Sellars os Aspen (Maroon .J. 413 A 35 NP NP 378 NP Lan: L Gulch Anil s -en s 635 A 28 NP NP 607 NP Summit..........; Snake River 2.0.0: L000 re. t.. NP .!: PASS - Tl c HBoreae Pass.: _L n S. O1 XO. 150 8 50 NP NP 92 NP Patk......__.. % sA Rod Mill . 202. s tvo NP |_ s.. alr e eal un P Lenin aio ne {een a Fast Brush Creek.! _j 1, 083 70 A NP NP | 1,013 NF _ P 30 P NP NP i NP Red and White 250 25 25 NP NP 200 NP Red Canyon.... :C. "L ROLL: P 1000" 3 344 3 36 P NP NP P NP State- cl + 90 12-24 P NP NP P NP phecphorn 15 A 15 NP NP NP NP Grand....:..._. Cal l. L_ _d CM LAI P A P NP NP 1 NP CGorePasg iL nus Loti uel dost P 10 10+ NP NP NE NP 2. AL. cul anale wal P 20 15+ NP NP NP NP Tabernash Campground 3. .... .._... _. NP |-: s al { L toto mre tee c nce tua ' Thomas and others (1945). * Just outside the limit of the Chinle; zero isopach nearby. * Sheridan (1950). + Donner (1949). D36 The clay mineralogy and mottled coloration of the mottled member suggest that it is derived from a residual weathered zone (Schultz, 1963). Coarse detritus and cross strata in some of the siltstone, sand- stone, and conglomerate therein indicate that these sediments were reworked and transported by streams. Ocher siltstone member The informal name ocher siltstone member is as- signed to a unit of ocher siltstone and minor amounts of red siltstone, which is present throughout the Uinta Mountains. The member consists of structureless siltstone, clayey siltstone, and minor silty claystone. The ocher and reddish siltstone and claystone commonly contain oolites, carbonate nodules, and secondary gypsum vein- lets. Many oolites and nodmes contain analcite (Kel- ler, 1953). The ocher color probably is due to goethite (L. G. Schultz, written communication, 1958). Thickness increases from east to west in the Uinta Mountains (figs. 2, 3, and table). Range of thickness is 50 to 200 feet in the central and eastern Uinta Mountains. The ocher siltstone member is overlain at Miller Creek and Cliff Creek by the red siltstone member, at Cross Mountain by the sandstone and conglomerate member, and at Vernal and Lake Fork River by the upper member (figs. 2, 3). The contact between the ocher siltstone member and overlying units is placed at the top of the distinctively colored siltstone. The ocher siltstone member is lithologically identical to part of the Popo Agie Member of the Chugwater Formation in the Lander area, Wyoming, as was sug- gested originally by Keller (1953). South and east from the Uinta Mountains the ocher siltstone member apparently wedges out. The composition of the ocher siltstone member sug- gests that it was deposited in a shallow water body, perhaps a marshy lake, in a broad basin or lowland (Keller, 1952). Sandstone and conglomerate member The sandstone and conglomerate member is com- posed of gray, pink, and brown siltstone, sandstone, and conglomerate. This member is restricted to out- crops in the easternmost Uinta Mountains at Cross Mountain, Vale of Tears, and Disappointment Creek. The sandstone and conglomerate member is considered a basal coarse facies of the red siltstone member. The basal part of the member is mainly sandstone and subordinately siltstone and conglomerate. This basal part is composed of quartz, some feldspar, chert, STRATIGRAPHY AND PALEONTOLOGY and mica; the matrix and cement consist of calcite and clay minerals (R. A. Cadigan, written communication, 1958). The granules and pebbles are dominantly limy siltstone and sparse siliceous rock types. The remain- der of the member consists of siltstone, sandstone, and mudstone pebble conglomerate. Phytosaur bone frag- ments and teeth (S. H. Mamay and G. E. Lewis, writ- ten communication, 1957) are numerous in this member and particularly abundant in the coarser parts. Strati- fication consists of horizontal laminae and thin beds with ripple laminae, current lineation, and cross strata. The contact between the sandstone and conglomerate member and the overlying red siltstone member is gen- erally placed at the base of the continuous or dominant red siltstone section. A flood-plain environment is indicated by lithology, sedimentary structures, and phytosaur remains. Cusp ripples, current lineation, and cross strata indicate stream deposition. One study of orientation of cross strata in the top of the member at Cross Mountain indicates a southwesterly direction of sediment trans- port. Red siltstone member A unit of red siltstone and minor amounts of sand- stone and conglomerate occurs in the eastern Uinta Mountains and in northwestern and west-central Col- orado. This unit, referred to here informally as the red siltstone member, is correlated with the Church Rock Member of the Chinle, a member named and de- scribed by Witkind and Thaden (1963) in Monument Valley, Ariz. The name Church Rock is used widely in Utah south of the Uinta Basin (Stewart, 1957). The siltstone, very fine grained sandstone, and the matrix of the conglomerate are composed dominantly of silt- and sand-sized grains of quartz, some feldspar, and sparse mica and tuff (?); the matrix and cement consist of iron oxide, calcite, and clay minerals (R. A. Cadigan, written communication, 1958). The red siltstone member is generally very calcareous. The conglomerate contains well-rounded elongate granules and pebbles of limy siltstone and silty limestone set in a siltstone matrix. The basal part of the red siltstone member at East Brush Creek contains lenses of sub- angular to rounded sand and locally conglomerate layers containing granules and pebbles, as well as a few cobbles composed of quartz, chert, feldspar, silt- stone, and limestone. Quartz granules and pebbles occur in the basal part of the red siltstone member in many areas in northwestern and central Colorado. The basal siltstone at Cliff Creek contains gravel com- posed of material from the underlying ocher siltstone member. POOLE AND STEWART From a distance the red siltstone member appears to be thin to thick bedded; however, close inspection shows that the member is either structureless or only crudely stratified. Locally it contains cross strata, mud cracks, and low-index ripple marks. Conspicuous purplish vertical cylindrical structures in red siltstone beds were noted in several areas. These structures appear to contain more lime than the adjacent silt- stone and may have formed along vertical fracture intersections. The only fossils found were sparse bone fragments at the base of the member at Cliff Creek and near the top of the member at Disappointment Creek. The red siltstone member is generally absent in the vicinity of the Gore Range and is erratic in thickness in many parts of northwestern and west-central Col- orado (see table), owing to pre-Late Jurassic erosion. In the Uinta Mountains, the red siltstone member is underlain by the ocher siltstone member at Miller Creek, Cliff Creek, and Vermilion Creek; it is under- lain by the sandstone and conglomerate member at Disappointment Creek and Cross Mountain. In north- western Colorado, the red siltstone member is under- lain by the mottled member in nearly all areas. At East Brush Creek it overlies the Gartra Member, which fills the stratigraphic position normally occu- pied by the mottled member. The red siltstone interfingers laterally with the upper member between Cliff Creek and Vernal. The contact is generally placed between the highest struc- tureless red siltstone and the lowest brown sandstone of the upper member. Where the upper member is absent, the Glen Canyon Sandstone overlies the red siltstone member of the Chinle. In northwestern Colorado, beyond the eastern limit of the Glen Canyon Sandstone, the Entrada Sandstone or equivalent strata overlies the Chinle Formation (figs. 2, 3). Beds above and below the contact appear disconformable at nearly all outcrops; however, re- gional study indicates that from west to east younger and younger beds rest on the Chinle and that the con- tact is clearly a regional angular unconformity. The red siltstone member is probably mainly a flood- plain deposit but, in part, a deltaic and lake deposit. The source rock was probably mostly older red beds such as the Maroon Formation and Lower Triassic equivalents and, in part, exposed lower Paleozoic rocks and Precambrian igneous and metamorphic areas in central Colorado. Upper member The name upper member was applied by Kinney (1955) to a sequence of orange, brown, and gray sand- | | D37 stone; red, gray, and brown siltstone; and red, brown, gray, and green claystone. The member is at the top of the Chinle Formation and is best developed in the western and central Uinta Mountains. Many of the sandstone beds in the member resemble the overlying massive-weathering Glen Canyon Sandstone and may represent lenses or tongues of the Glen Canyon. The upper member may be transitional into the Glen Canyon Sandstone. The sandstone layers are composed of subrounded to well-rounded very fine to medium grains of quartz, some feldspar, and sparse quartzite, chert, and tuff (?) ; the matrix and cement include calcite and clay min- erals (R. A. Cadigan written communication, 1958). The layers are horizontally laminated to thick bedded. Ripple laminae and thin to thick planar and trough sets of small- and medium-scale cross laminae are present in the upper part of a few sandstone beds. Some cusp ripples, current lineation, and mud cracks were noted on a few stratification surfaces. - Three studies of cross-strata orientation made of a lower sand- stone (partly eolian) in the Vernal area indicate a wide range in direction of sediment transport from northeast to southwest, averaging southeasterly. The siltstone is composed of quartz, some feldspar, and sparse mica ; the matrix and cement consist of iron oxide, calcite, and clay minerals (R. A. Cadigan, writ- ten communication, 1958). The siltstone is horizon- tally thinly laminated to thick bedded ; some parts are structureless. A few units contain ripple laminae, mud cracks, and clayey siltstone pellets. The claystone is generally silty and horizontally thinly laminated. A pale-red to grayish-red silty claystone unit 15-25 feet thick is at the top of the upper member throughout the central and most of the eastern Uinta Mountains. The upper member at Vernal consists of about 72 percent sandstone, 20 percent siltstone, and 8 percent claystone. The proportion of sandstone decreases both to the east and to the west from Vernal. At Lake 30 percent claystone. At Cliff Creek, east of Vernal, Fork River, west of Vernal, the upper member con- sists of 19 percent sandstone, 51 percent siltstone, and the upper member intertongues with the red siltstone member and is thin. Here the upper member consists of 4 percent sandstone, 70 percent siltstone (which may be chiefly tongues of the red siltstone member), and 26 percent claystone. The upper member overlies the ocher siltstone mem- ber west of the Green River. East of the Green River, the upper member overlies the red siltstone member (fig. 2). The contact between the upper member and red siltstone member is characterized by intertonguing, and the upper member wedges out eastward near Mil- D38 ler Creek above or at the top of the red siltstone mem- ber (fig. 2). The upper member is overlain by the Glen Canyon Sandstone with apparent conformity. The contact between them in the central and eastern Uinta Moun- tains is at the top of a persistent grayish-red silty claystone which underlies a massive cliff-forming sandstone of the Glen Canyon Sandstone. Sedimentary structures and lithology indicate that the upper member is mainly a flood-plain deposit but that it includes some wind deposits. GLEN CANYON SANDSTONE A thick sandstone overlying the Chinle Formation in the western Uinta Mountains has been generally called Nugget Sandstone, whereas in the eastern Uinta Mountains and in the vicinity of the White River Plateau it has generally been called Navajo Sandstone. Continuity and uniformity of this sandstone in the Tinta Mountains indicate the desirability of one name for this unit. The available evidence indicates that the sandstone body is equivalent to part or all of the Glen Canyon Group of the Colorado Plateau province to the south. MacLachlan (1957) showed the Navajo Sandstone of the Uintas as being equivalent to the Wingate, Kay- enta, and Navajo exposed south of the Uinta Basin. Later work by R. F. Wilson (written communication, 1962), however, indicates that in some areas the sand- stone of the Uinta Mountains may be equivalent largely to the Wingate Sandstone. According to Wilson, drill-hole data north of the San Rafael Swell (east and southeast of Price, Utah) and along the Colorado- Utah State line (northwest of Grand Junction, Colo.), show the Wingate thickening northward and the Kay- enta and Navajo thinning. If these trends continue northward, it seems likely that the Kayenta wedges out and that much of the sandstone of the Uinta Mountains is equivalent to strata older than Navajo. A widespread pre-San Rafael Group unconformity bevels older beds eastward in the eastern part of the Uinta Basin (Wright and Dickey, 1963), and the Navajo and Kayenta may have been partly or com- pletely removed by erosion in the eastern Uinta Moun- tains and in northwestern Colorado. This evidence indicates that the name Navajo is undesirable for this sandstone unit. The name Nugget also is opposed by many geologists because of lithologic differences be- tween the Nugget in the type area and that in the Uinta Mountains. As the existing evidence indicates that this sandstone body is equivalent to part or all of the Glen Canyon Group to the south, the name Glen Canyon is extended into this area and given forma- STRATIGRAPHY AND PALEONTOLOGY tional rank. The Glen Canyon Sandstone is above the Chinle Formation and below rocks of the San Rafael Group in the Uinta Mountains and in the vicinity of the White River Plateau. The Glen Canyon Sandstone is designated as Late Triassic and Early Jurassic in age in accordance with the current age assignment of the Glen Canyon Group in the southern part of the Colorado Plateau. The Glen Canyon Sandstone extends throughout northeastern Utah and part of northwestern Colorado but wedges out southeastward in the vicinity of the White River Plateau. The Glen Canyon Sandstone is overlain by the Middle and Upper Jurassic rocks assigned to the Twin Creek Limestone in the western Tinta Mountains and to the Carmel Formation in the eastern Uinta Mountains. In the easternmost Uintas the Carmel wedges out to the east, and the Entrada Sandstone rests unconformably on the Glen Canyon Sandstone. The two sandstones, however, can usually be distinguished on the basis of type and orientation of cross strata and locally by the presence of scattered ventifacts or pebbles along the contact. The Glen Canyon Sandstone consists of gray, orange, brown, yellow, pink, and white sandstone. It is com- posed of subrounded to well-rounded very fine to fine grains of quartz, some feldspar, and sparse chert and quartzite; the matrix and cement consist of calcite and clay minerals (R. A. Cadigan, written communication, 1958). The Glen Canyon contains varying amounts of flat-bedded strata in the lower 50-100 feet. Most of the Glen Canyon, however, contains thick wedge- planar, tabular-planar, and subordinate lenticular trough sets of large- and medium-scale cross strata. Parallel and cusp ripple marks, and mud cracks were noted in the basal part in some areas. Sedimentary structures in the Glen Canyon Sand- stone suggest that the basal 50 feet is mainly water laid but that the thick upper part is mainly eolian in origin. Cross-strata orientations indicate that the winds that deposited the eolian sandstone blew from the north and northeast (Poole, 1962). REFERENCES Donner, H. F., 1949, Geology of the McCoy area, Eagle and Routt Counties, Colorado: Geol. Soc. America Bull., v. 60, no. 8, p. 1215-1248. Hansen, W. R., 1955, Geology of the Flaming Gorge quadrangle, Utah-Wyoming: U.S. Geol. Survey Geol. Quad. Map GQ-75. Huddle, J. W., and McCann, F. T., 1947, Pre-Tertiary geology of the Duchesne River area, Duchesne and Wasatch Coun- ties, Utah: U.S. Geol. Survey Oil and Gas Inv. Prelim. Map 75. Keller, W. D., 1952, Analcime in the Popo Agie Member of the Chugwater Formation: Jour. Sed. Petrology, v. 22, no. 2, p. 70-82. POOLE AND STEWART Keller, W. D., 1953, Analcime in the Chinle Formation of Utah correlative with the Popo Agie of Wyoming: Jour. Sed. Petrology, v. 23, no. 1, p. 10-12. Kinney, D. M., 1951, Geology of the Uinta River and Brush Creek-Diamond Mountain areas, Duchesne and Uintah Counties, Utah: U.S. Geol. Survey Oil and Gas Inv. Map 123. 1955, Geology of the Uinta River-Brush Creek area, Duchesne and Uintah Counties, Utah: U.S. Geol. Survey Bull. 1007, 185 p. Kinney, D. M., and Rominger, J. F., 1947, Geology of the Whiterocks River-Ashley Creek area, Uintah County, Utah: U.S. Geol. Survey Oil and Gas Inv. Prelim. Map 82. MacLachlan, M. E., 1957, Triassic stratigraphy in parts of Utah and Colorado, in Intermountain Assoc. of Petroleum Geologists Guidebook, Field conference in Uinta Basin, 1957: p. 82-91. Poole, F. G., 1961, Stream directions in Triassic rocks of the Colorado Plateau: Art. 199 in U.S. Geol. Survey Prof. Paper 424-C, p. C©1389-C141. 1962, Wind directions in late Paleozoic to middle Meso- zoic time on the Colorado Plateau: Art. 163 in U.S. Geol. Survey Prof. Paper 450-D, p. D14T-D151. Powell, J. W., 1876, Report on the geology of the eastern por- tion of the Uinta Mountains: U.S. Geol. and Geog. Survey Terr., 2d div. Robeck, R. C., 1956, Temple Mountain Member-new member of Chinle Formation in San Rafael Swell, Utah: Am. R D39 Assoc. Petroleum Geologists Bull., v. 40, no. 10, p. 2499, 2506. Schultz, L. G., 1963, Clay minerals in Triassic rocks of the Colorado Plateau: U.S. Geol. Survey Bull. 1147-C, p. Cl- C71. Sheridan, D. S., 1950, Permian(?), Triassic, and Jurassic stratigraphy of the McCoy area of west central Colorado : The Compass, v. 27, no. 3, p. 126-147. Stewart, J. H., 1957, Proposed nomenclature of part of Upper Triassic strata in southeastern Utah: Am. Assoc. Petro- leum Geologists Bull., v. 41, no. 3, p. 441-465. Thomas, H. D., and Krueger, M. L., 1946, Late Paleozoic and early Mesozoic stratigraphy of Uinta Mountains, Utah: Am. Assoc. Petroleum Geologists Bull., v. 30, no. 8, p. 1255-1293. Thomas, C. R., McCann, F. T., and Raman, N. D., 1945, Corre- lation of exposed rocks in northwestern Colorado and northeastern Utah, and logs of deep wells in northwestern Colorado: U.S. Geol. Survey Oil and Gas Inv. Prelim. Chart 16. Witkind, I. J., and Thaden, R. E., 1963, Geology and uranium- vanadium deposits of the Monument Valley area, Apache and Navajo Counties, Arizona: U.S. Geol. Survey Bull. 1103, 171 p. Wright, J. C., and Dickey, D. D., 1963, Block diagram of the San Rafael Group and underlying strata in Utah and part of Colorado: U.S. Geol. Survey Oil and Gas Inv. Chart 68. GEOLOGICAL SURVEY RESEARCH 1964 SIGNIFICANCE OF TRIASSIC OSTRACODES FROM ALASKA AND NEVADA By 1. G. SOHN, Washington, D.C. Abstract.-Marine ostracodes are recorded for the first time from sedimentary rocks assigned to the Upper Triassic of Alaska and Middle Triassic of Nevada. These occurrences ex- tend the range of the Cytherellidae downward into the Middle Triassic and tentatively extend the ranges of the Paleozoic Beyrichicopina and Thlipsuracea into the Triassic. Identifiable marine Triassic ostracodes have hitherto not been recorded in North America, although non- marine forms have been known for more than a cen- tury in the continental Triassic beds of the Eastern United States (Jones, 1862). Jones described and illustrated Candona? rogersii and C.% emmonsi from the Triassic of North Carolina and Pennsylvania. These are probably decalcified films of ostracode shells, and are therefore unidentifiable (Sohn, 1958). Marine ostracodes are present in limited numbers in samples collected for the U.S. Geological Survey by E. G. Sable in 1948 and C. L. Whittington in 1952 from the upper part of the Shublik Formation (Upper Triassic) of the Arctic slope of Alaska. The Fora- minifera from this formation were described by Tappan (1951). Harlan Bergquist kindly segregated the ostracodes from the collections. Silicified marine ostracodes from the Grantsville Formation of late Middle Triassic age (Silberling, 1959) in the Shoshone Mountains, Nev., were sent to me by Prof. David L. Clark, Department of Geology, University of Wisconsin. These specimens were ex- tracted along with conodonts by Mr. Cameron Mosher, University of Wisconsin, from the insoluble residue of a limestone sample collected by N. J. Silberling of the Geological Survey. Although the ostracodes from Alaska are pyritized and very poorly preserved, and those from Nevada are not perfectly silicified, several genera can be identified. The samples from Alaska are from the Shublik For- mation, on Dodo Creek 2 to 2.3 miles above the junc- tion with the Sadlerochit River, in the foothills of the Sadlerochit Mountains, northern Alaska. The 30 col- lections made contain the following: Hungarella sp. or spp. Paracypris? sp. or spp. Darwinula® sp. Steinkerns unident. The sample from Nevada is from USGS Mesozoic loc. M76, in the Grantsville Formation, in the Sho- shone Mountains, and contains the following: Acratia® sp. Carinobairdia® sp. Gen. indet. Bairdiidae Cytherelloidea n. sp. 1 Cytherelloidea n. sp. 2 New genus Thlipsuracea ? Gen. indet. Cytheracea Gen. indet. Healdiidae Gen. undet. Beyrichicopina ? Prof. Clark informs me (written communication, 1964) that ostracodes are present in other Triassic samples from Nevada, so that additional collecting will doubtless increase the list. The available infor- mation, though meager, is of interest because it begins to fill the gap in the knowledge of Triassic ostracodes and the relation of Paleozoic to post-Paleozoic ostra- code groups. Figure 1 shows the current interpretation of the range and affinities of superfamilies and higher cate- gories of the Ostracoda, upon which is superposed the information obtained from this study. Sylvester- Bradley (1962) discussed the classification and sug- gested alternate groupings. The stratigraphic ranges of the groups as illustrated by Scott and Sylvester- Bradley in Moore (1961) are indicated by dashed lines in the Triassic, with the exception of the family Cythe- rellidae which extends down to the Upper Triassic. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D40-D42 D40 D41 SOHN a TERTIARY Plat R g ® f & aan ag 8 A Darwin- 4 Cytherellidae 3 é laces g CRETACEOUS £, - & s 3 O JURASSIC [1 § -& h LL REF} J 3 A U 3 H1 H} H- H L TRIASSIC NJ 1 I| U H [] A l H I H PERMIAN I| L J 11 //// 8 U/ 9 PENNSYLVANIAN g E .3 3 fis] 3 MISSISSIPPIAN $ ma m DEVONIAN / Myodocopina SILU 2 Thlipsuracea k of Quasillitacea ORDOVICIAN S5 ei eel aes Kloedenellocopina CAMBRIAN Leperditicopida Archaeocopida FircurE 1.-Diagram showing stratigraphic distribution and inferred relations of the super- families and higher categories of Ostracoda, after Scott and Sylvester-Bradley, in Moore (1961, figs. 32 and 34). More recently, Hartmann discussed the phylogeny of Ostracoda and published a diagram (1963, p. 28, text fig. 8) in which the entire scheme is shown by dashed lines through the Triassic System. The reasons for the revisions shown by the stippled pattern on figure 1 are given below: Suborder Beyrichicopina Kollmann (1963, p. 144-146) recorded Kirkbyidae? indet., a family that is included in the Byrichicopina, from the Upper Triassic of the Alps, and Hornibrook (1949) described the Recent family Punciidae that is tentatively placed in this suborder. The specimens from Nevada listed above as gen. undet. Beyrichico- pina? substantiate the extension of the range of this suborder into the Middle Triassic. Suborder Platycopina The presence of Cytherelloidea in the assemblage from Nevada extends the range of this suborder into the Middle Triassic. Superfamily Healdiacea Hungarella in the Upper Triassic of Alaska, and gen. indet. Healdiidae in the Middle Triassic of Ne- vada are the basis for extending Healdiacea through the Triassic. Stippled pattern shows age revisions discussed in text. Superfamily Thlipsuracea The new genus of Thlipsuracea? in the Middle Triassic of Nevada suggests that this taxon has a longer stratigraphic range than has been supposed. Superfamily Cytheracea The presence of an indeterminate genus of Cythe- racea in the Middle Triassic of Nevada extends the range of this taxon into the Middle Triassic. Superfamily Bairdiacea Acratial, Carinobairdia®, and Bairdiidae gen. indet. from Nevada document the presence of this group in the Triassic. Superfamily Cypridacea The Upper Triassic specimens from Alaska, identi- fied is Paracypris? sp. or spp., are very poorly pre- served. The fact that Styk (1962, p. 733) listed with- out illustrating sp. from the Muschelkalk of Poland supports the extension of this superfamily into the Triassic. Superfamily Darwinulacea Although the identification of Darwinulae in the Upper Triassic of Alaska is based on extremely poorly preserved specimens, the genus has been recorded many D42 times from the Triassic in Europe. Drawings of the diagnostic muscle sear of Darwinulacea by Beutler and Griindel (1963, pl. Ta, fig. 3) firmly establish the occurrence of this superfamily in the Triassic. Suborder Myodocopina Although several fragments in the assemblage from Nevada might possibly represent myodocopid ostra- codes, they are inadequate for positive identification and are not mentioned in the faunal list. However, the description and illustration of Cypridina balber- steinensis Kittl in Trauth (1918) from the Middle Triassic, and C. tonkinensis Patte (1926) from Upper Triassic supports the inclusion of this taxon in the Triassic. REFERENCES Beutler, Gerhard, and Griindel, Joachim, 1963, Die Ostracoden des Unteren Keuper im Bereich des Thiiringer Beckens: Freiberger Forschungshefte, C 164, p. 33-92, 9 pls. Hartmann, Gerd, 1963, Zur Phylogenie und Systematik der Ostracoden: Zeitsch. zool. Syst. Evolutionsforsch. v. 1, 154 p., 35 figs. Hornibrook, N. de B., 1949, A new family of living Ostracoda with striking resemblances to some Paleozoic Beyrichiidae: Royal Soc. New Zealand Trans., v. 77, pt. 4, p. 469-471, pls. 50, 51. Jones, T. R., 1862, North American Lower Mesozoic Cypridae. Appendix in A monograph of fossil Estheriae: Palaeontogr. Soc. London, p. 123-127, pl. 5, text fig. 12. ps STRATIGRAPHY AND PALEONTOLOGY Kollmann, Kurt, 1963, Ostracoden aus der alpinen Trias IL. Weitere Bairdiidae: Jahrb. Geol. Bundensanst., Wien, v. 106, p. 121-203, pls. 1-11, 3 tables, 8 text figs. Moore, R. C., ed., 1961, Treatise on invertebrate paleontology, pt. Q. Arthropoda, 3. Ostracoda: Geol. Soc. America and Univ. Kansas Press, 442 p., 334 figs. Patte, Etienne, 1926, Etudes paléontologiques relatives a la géologie de l'Est du Tonkin (Paléozoique et Trias) : Service Géologique de l'Indochine, Bull., v. 15, fase. 1, 240 p., 12 pls. Silberling, N. J., 1959, Pre-Tertiary stratigraphy and Upper Triassic paleontology of the Union district, Shoshone Mountains, Nevada: U.S. Geol. Survey, Prof. Paper 322, 67 p., 9 pls., map [1960]. Sohn, I. G., 1958, Chemical constituents of ostracodes; some application to paleontology and paleoecology: Jour. Pale- ontology, v. 32, p. 730-736. Styk, Olga, 1962, Triassic microfauna in borings of Sulechow and Ksiaz [abs.]: Poland Inst. Geol. Kwartalnik Geol., v. 6, no. 4, p. 732-733. Sylvester-Bradley, P. C., 1962, The taxonomic treatment of phylogenetic patterns in time and space, with examples from the Ostracoda in David Nicols, ed., Taxonomy and geography : Systematic Assoc. Pub. 4, London, p. 119-133, 4 figs. Tappan, Helen, 1951, Foraminifera from the Arctic slope of Alaska ; General Introduction and pt. 1, Triassic Foraminif- era : U.S. Geol. Survey Prof. Paper 236-A, 20 p., 5 pls. Trauth, Friedrich, 1918, Uber einige Krustazeenreste aus der mediterranen Trias: Vienna Naturhistirisches Hofmu- seums, Annalen, v. 32, p. 172-192, 1 pl. CEOLOGICAL SURVEY RESEARCH 1964 MIDDLE DEVONIAN PLANT FOSSILS FROM NORTHERN MAINE By JAMES M. SCHOPF, Columbus, Ohio Abstract.-A new collection of plant fossils, including new species described as Barrandeina(?) aroostookensis and Calo- mophyton forbesii, is reported from the Mapleton Sandstone of northern Maine. Calamophyton is not previously recorded in North America. These fossils are allied with European fossils of the early Givetian, so the age of the Mapleton is probably equivalent. The Mapleton Sandstone is flat lying and was deposited in this region after Acadian folding. Specimens of Mapleton Sandstone bearing spiny psilophytic remains were collected by Richard S. Naylor in the vicinity of Presque Isle in northern Maine and referred to me in February 1961 for paleo- botanical study and age determination. Subsequently, additional specimens from the same area were sent by Mr. W. H. Forbes of Washburn, Maine. The psilo- phytic remains seemed to suggest an age not later than Middle Devonian for the Mapleton Sandstone. A later study of spores and other fragments from macer- ation residues suggested the possibility of an early Middle Devonian age and indicated that further col- lecting was needed. Shortly afterward, very charac- teristic spiny psilophytes were reported by Hueber and Grierson (July, 1961) in the lower part of the Upper Devonian deposits in New York State. This occur- rence indicated that the spiny psilophytes were less restricted in age than had previously been supposed and reemphasized the need for additional collecting and study of collections from northern Maine. Last summer (1963) I was able to visit the Maine locality personally and obtain an ample collection of plant material. These additional plant fossils are from Mapleton Sandstone at a quarry on the Winslow farm, about 3 miles west of Presque Isle. Shaly material rejected in quarrying the flat-lying and not highly indurated sandstone contains a variety of fossil plants. A proto- articulate member was recognizable in the field, in addition to both smooth and spiny representatives of psilophytes. Other elements have been recognized in subsequent study which show marked similarity with plants of the classical late Middle Devonian assemblages from Bohemia, the Rhineland, and Belgium that have been studied so thoroughly by Kriausel and Weyland, LeClereq, Hgeg, and others (see references). A Middle Devonian age determination based on plant remains from the Mapleton Sandstone seems fully justified. The purpose of the present paper is to describe this new evidence and examine the possibility of more exact correlation. The age of the flat-lying Mapleton Sandstone in northern Maine is of particular interest because the sandstone appears to be the oldest formation not affected by Acadian folding in that area. Beds of the Trout Valley Formation of Dorf and Rankin (1962) in the Traveler Mountain quadrangle, 60 miles south- west of the Presque Isle area, are only slightly inclined and may be a little older. The Chapman Sandstone, at Edmunds Hill, 3 miles southwest of the Winslow quarry, contains Early Devonian marine fossils and plant fragments and resembles the Mapleton Sandstone in general lithologic appearance, but the beds are strongly inclined and more indurated. Nematophycean propagula (see Schmidt, 1958) classified as Pachytheca sp. (see figs l1@ and 1e) have been collected by W. H. Forbes and me at the Edmunds Hill exposure. These bodies were originally very readily disseminated, but I have found none in searching my more extensive collections of Mapleton Sandstone at the Winslow quarry locality. Such a locally restricted distribution would be unlikely if the two sandstones merely rep- sented different aspects of the same deposit, so these plant remains add confirmation about the difference between Chapman and Mapleton Sandstones. The time interval between deposition of the two sandstones of the Presque Isle area thus seems to bracket a terminal point of the Acadian orogeny. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D43-D49 742-652 O-64--4 D43 D44 STRATIGRAPHY AND PALEONTOLOGY Frcur® 1 SCHOPF The plant assemblage from the Mapleton Sandstone at the Winslow quarry includes spiny psilophytes of the Psilophyton princeps var. ornatum type, and smooth psilophytes corresponding well with those Kriusel and Weyland (1923) have assigned as Hostimella hostimensis, and Dorf and Rankin assign as Hostimella sp. and Aphyllopteris sp. Larger smooth axes, some of them more than 20 mm in diameter, can perhaps be classed with Taeniocrada. Several specimens longitudinally grooved and striate and up to 8 em broad are assigned tentatively and with considerable hesitation to the genus Barrandeina Stur (1882), and one unusually fine specimen with petioles attached is referable to a new species. These plants, if not directly congeneric with Barrandeina, seem to have a similar habit and structure and to be rather closely allied. A considerable number of fragments can be identified with Calamophyton as described below. Only brief descriptions of forms assigned to Barrandeina(?) and Calamophyton will be given at this time. Fraur® la.-Pachytheca sp. Spheroidal mold of a nema- tophycean _ propagulum; - X10. Chapman _ Sandstone, Edmunds Hill, about 5 miles southwest of Presque Isle, Aroostook County, Maine. Specimen 3. b, Barrandeina(?) aroostookensis, new species. Axis tip showing decurrent, phylloidal petioles; X1. Inverted U-shaped petiolar scars appear on the caulome at points where petioles are lacking. Mapleton Sandstone, Winslow farm, 3 miles west of Presque Isle, Aroostook County, Maine. Specimen 44, holotype; repository U.S. National Museum (Cat. No. 42302). Counterpart of specimen in b; X1. Photographed under xylol. Recurved petiole second from the top on the right shows part of the foliated tip. d, Calamophyton sp. Stem, X1, showing coarse punctation, possibly owing to sclerotic nests in outer cortex, and longi- tudinal striation; nodal ridges obscure. Mapleton Sand- stone, same location as b. e, Pachytheca sp. Nematophycean propagulum; X 10, show- ing cortex and medulla along a median fracture plane. Chapman Sandstone, same location as a. Specimen 4. Calamophyton sp. Stem segment, X 2.28, showing close-set nodal ridges and longitudinal striation. directly on a nodal ridge, other similar scars (emergences?) are in the internodal zone. Mapleton Sandstone, same location as b, c, and d. Barrandeina(?) sp. Axis, X1, showing longitudinal ribs becoming diffuse toward the top. The specimen may be oriented basal end uppermost on the figure. h, Calamophyton sp. Stem segment, X1, with abrupt trans- verse fracture at the base (possibly an indication that the structural organization of the node continues within the axis) and broadening of distal end near point of digitate branching. Surface shows cortical punctation, linear striation, and nodal ridges. Only a few leaf or emergence scars are present. - Mapleton Sandstone, same location as b. i, Calamophyton sp. Asymmetric stem crown, 2.6, showing successive bifurcations, punctate surface, and nodal grooves. Deep longitudinal fissures with intervening coaly layers suggest that an alternation of persistent tissues (coal) and softer structures were radially alined within the axis. Mapleton Sandstone, same location as b. Calamophyton sp. Stem crown X1, showing double bi- furcation and punctate surface. - Mapleton Sandstone, same location as b. 9 J. 9 J One leaf scar is D45 GENUS BARRANDEINA STUR (1882) (see also: Pontonié and Bernard, 1903; Kriusel and Weyland, 1933). Barrandeinal?) aroostookensis n. sp. The specimen shown on figures 1b and 1¢ includes the distal part of a leafy ' axis about 12% ecm long, nearly 15 mm broad at the base, and about half as wide at the top. The attached petioles are strongly reflexed away from the axis, tapering and with a median keel; they are strongly decurrent along the axis which appears deeply fluted and made up chiefly of the overlapping petioles. The leaves evidently are arranged spirally, although at the tip they appear to be sub-opposite and the arrangement may actually be irregular. Some petioles are missing, leaving a scar resembling an inverted U in which no simple vascular trace is apparent. Coalified films commonly show thin longitudinal bands on the sears and on the decurrent and excurrent parts of petioles which may reflect vascular organization or the presence of thin sclerotic strands in the cortex. The smaller counterpart photographed under xylol on figure 1¢ appears to show a foliar continuation of the petiole at the right, second from the top. Several linear segments seem to be curled circinately as if not fully expanded. At the tip they appear with bifurcate digitation, not necessarily different from a Psygmophyl- lum or Platyphyllum type of megaphyllous leaf in juvenile condition (see Hgeg, 1942, p. 98-113). Some cellular striation is visible parallel to the margin of the segments, but true venation is not apparent. Further details may become available when additional collec- tions have been studied. If actually referable to Barrandeina, this leafy spec- imen would seem to be the only one that has been found which clearly includes part of an axis adjacent to the stem tip. All others, including Krejci's type specimen of B. dusliana, the type species (see the excel- lent photographic illustration by Stur, 1882, pl. 5, fig. 8), provide very uncertain information about axis termination. In the Aroostook County specimen the reflexed petioles are more rapidly attenuate and sharply keeled than in other species. Some stubs of petioles seem persistent, generally strongly reflexed, and others are broken close to the axis, leaving a deep character- istic scar in specimens from Bohemia (Stur, 1882; ' Apparent similarity of lateral appendages on these axes with leaves may be more evident than real. - The nature of leaves in Devonian time is not as definite as in later periods, yet the present examples could be prototypic megaphylls. Additional morphologic evidence will be sought. | In the meantime, leaf and petiole terminology, discussed by Stur (1882) and followed both by Potonié and Bernard (1903) and by Kriusel and Weyland (1933), may readily be interpreted descriptively. D46 Potonié and Bernard, 1903; Krause and Weyland, 1933) and from western Norway (Hgeg, 1931). Peti- oles of Enigmophyton hoegii Ananiev (1959) from cen- tral Siberia are somewhat similar to those of the Aroostook specimen, but other resemblances are much less evident. - The leaves or lateral appendages in Bar- randeina are notably decurrent and seem to be spiral in arrangement. - The axis is grooved or fluted on this account and may have been a type of "false" stem consisting chiefly of adnate or adherent appendages. These plants grew erect and some of them must have been 1 or 2 meters tall. All these features accord well with the new material, but none of them provide any decisive indication of affinity. The base of the new petiolate specimen, shown on figures 1b and 1¢, is about the same size as the Bohe- mian specimens and shows the same type of pronounced cortical fluting. - Other specimens without petioles from the Winslow quarry show a similar fluting and one of them is about 8 cm in diameter. The larger fluted specimens usually do not show petioles or clearly de- fined scars, so their identification is questionable. Commonly one end seems "feathered out," as at the top of the specimen shown on figure 1g. Some of the "feather'' probably consists of sclerotic fibers, but in part it may be vascular. At the present time, it is problematic which end of this specimen is proximal. Rather similar cortical impressions have been described by Hgeg (1942, p. 43-46) from the Middle Devonian of Wijdefjord, Spitzbergen. Axes probably enlarged without aid of a cambium and growth may have been related to cortical roots. The origin and nature of the roots on these plants is an open question. However, an axis with structure similar to that shown at the bottom of figure 1g might easily correlate with that shown at the bottom of fig- ure 1b below the stem tip. The nature of the vascula- ture of these stems is not yet known; however, a strong woody cylinder probably is lacking. A diffuse system of vascular strands similar to that described for Duis- bergia by Krausel and Weyland (1929) would appear consistent with what is now known from compression structures. Diagnosis.-Plants erect, caulescent, probably as much as a meter high, axis distally tapering, fluted according to disposi- tion of strongly decurrent lateral appendages, with coaly surface films striated to suggest separate strands of strength- ening tissue. Foliation with bifurcate ultimate divisions, circinate in juvenile condition, possibly fairly large. Repro- ductive organs and organization and mode of substratal anchorage and growth, unknown. The species is named for the county of its origin in north- ern Maine. STRATIGRAPHY AND PALEONTOLOGY CALAMOPHYTON KRAUSEL AND WEYLAND (1926) Calamophyton sp. Specimens consisting of axis segments like those illustrated on figures 14, 1f, 1A, and 1j may be specifi- cally indeterminable if taken out of the context of their occurrences in association with other specimens, but the habit unmistakably is that of the main stem of Calamophyton as described by Kriusel and Wey- land (1926, 1929). Nodal ridges are clearly shown on figures 1f, 14, and 17. The sharp fracture line across the base of the stem shown on figure 12, and shown less well on figure 1f, suggests natural articulation. Leaves or emergences are very similar in their dis- tribution to those of C. bicephalum as described by Leclereq and Andrews (1960). The sandy matrix is well cemented, so it has not yet been possible to make preparations necessary for comparison of details of appendages, which in many instances are not pre- served. The characteristically punctate outer cortex, best shown on figure 14, is virtually identical to the Calamophyton cortex that has been illustrated by sev- eral authors for C. primaevum. Probably the cortical punctation of Calamophyton is caused by the presence of sclerotic nests similar but more rounded than those Leclereq and Banks (1962) have demonstrated in Pseudosporochnus, another of the very characteristic elements of the Middle Devo- nian flora in Bohemia and Belgium. Cortical struc- tures commonly are nearly duplicated in plants not very closely related. Nevertheless, the plants assigned to these two genera are very similar in size and habit. The presence of nodal ridges and longitudinal striation serves best to differentiate the main stems of plants belonging to the two groups. This difference may actually signify contrasting vascular arrangements more important than the superficial differences might seem to indicate. Those who have studied both genera concur in their taxonomic separation owing to verticil- late tendency, separation of fertile and sterile parts, and the anatropous sporangia of Calamophyton. Pseudosporochnus commonly is regarded as a member of the Psilopsida and Calamophyton as a member of the Hyeniales assigned to the Sphenopsida. However, to some degree the implication of extreme systematic separation may well be synthetic owing to the fact that members of the major classes become more closely ap- proximated toward their source. The Sphenopsida apparently originated from the psilopsids no later than the early part of the Middle Devonian (see Zim- mermann, 1959). SsCHO The size, general conformation, nodal ridges, longi- tudinal striation, and branching of the stem specimens from the Winslow quarry all conform better with our present understanding of the genus Calamophyton than they do with Pseudosporochnus. Leclereq and Andrews (1960, p. 3, 17) emphasize the importance of general habit in distinguishing Calamophyton. It is entirely possible that additional study will show that all the specimens illustrated should be referred to the species based on a fertile frond described below. Calamophyton forbesii, n. sp. The specimen illustrated by figure 2 consists of an ascending system of fertile branches that is sufficiently distinctive to be specifically identified. The apparent irregularity in branching may chiefly be a result of dichotomy in alternating planes. Nodal ridges are lacking from fertile branches. The lower (sterile ?) appendages apparently are not arranged in any defi- nite pattern. The fine sandy matrix has preserved gross relations satisfactorily, but finer structure has been modified by compression. Pairs of compressed sporangia may be observed in position in relation to their rachis on the prepared counterpart fragment, but details of the con- nective sporangiophore have not been seen. As in other representatives of Calamophyton, the arrange- ment of sporangiophores on the rachis and the degree // ////// / MW”? T TP t "w 4 wl J ///4,// " P //’/ - //////// ,/////// yp /,,//v;;i////N%/// A ll/W’ f j pa /7// ; ' ///////////”/%%7/% \\\\ | y". a IP //,,/ in”! a Arf H & 1C /,/ IK ”7/4ch \ e , WéMWWW/ #4 "Kye d 3 Ac \/ ou " _ / oo ass." c -s, =n ¥ a ola LP - game "(§ :A 7 \ $ D47 PF of separation of sterile and fertile appendages is not too clear. Many of the small flecks of carbonaceous material shown around the upper branches on figure 2 represent sporangia. From this, one might infer that fertile rachises were distal, but it would be premature to suggest that sterile appendages were always absent in these areas. Along a line of longitudinal fracture showing a distal, fertile rachis 2-3 mm in diameter, sporangiophores probably were spaced at about 4-mm intervals. - Judged by positions of sporangia, the sporangiophores were distally inclined at an angle of about 45° ; bifurcation of the sporangiophore may have occurred 4 or 5 mm from the rachis. Paired sporangia, like those shown on figure 2, inset A, may be observed in several places in a symmetrical spacing to suggest that arms of the sporangiophore were recurved and to suggest that at least two sporangia may be borne on each of the arms. Such an arrangement has also been observed in C. remeri Leclereq (1940). However, a number of addi- tional isolated sporangia also are present which are not easy to account for, and greater complexity may occur than can immediately be determined. The sporangia, usually paired, are fusiform, about 2%-mm long, smoothly tapered distally and a little more obtusely rounded at the base; a dehiscence mechanism has not been detected. Spores, probably 128 in each sporangium, are thin walled, spheroidal, (f ¢ ///////// RH) f Jt.. : / ad ins® \ \n i= Fiaur® 2.-Calamophyton forbesii, new species. Fertile shoot system, slightly reduced (scale indicated), showing apparent irregu- d numerous sporangia; most of the small flecks indicated in the distal area repre- 10 (scale indicated), taken from a distal counterpart fragment. Mapleton All specimen 2 photoline larity of bifurcation, irregular spiny emergences an sent broken sporangia. - A, paired sporangia, about X Sandstone, Winslow farm quarry, about three miles west of Presque Isle, Aroostook County, Maine. drawings from holotype; repository U.S. National Museum (Cat. No. 42303). D48 about 80-110 u in diameter, with ornamentation of tiny, well separated granules, and trilete rays about equal to half the normal radius. Sutures are probably straight and lips evidently are not prominent, but details are difficult to interpret in the preparations available. The demonstration of spores all of one kind in these sporangia suggests that C. forbes may be an isosporous plant. Diagnosis.-Plants shrubby, erect in habit, with fertile shoots branched dichotomously, commonly in alternating planes, very probably ascending from a digitately dichotomized caudex of which examples are in association, none attached. Mode of substratal growth and anchorage, unknown. Sterile appendages short, arranged irregularly on proximal parts of fertile shoots, probably mostly borne separately on vegetative branches. Numerous sporangiophores attach to stout distal rachises, probably inclined distally at about 45° on the rachis, as inferred from positions of sporangia. - At least two pairs of closely paired sporangia are borne on delicate stalks in reflexed position on each dichotomized(?) sporangiophore. Sporangia elongate, about 2.6%X0.7 mm maximum, probably containing about 128 spores per sporangium. Spores apparently all one kind (isosporous), trilete, originally spheroidal, 80-110 u diameter, with thin, distinctly granulated coat, commissural rays extend about half the normal radius of the spore. It is a pleasure to name this species for Mr. W. H. Forbes of Washburn, Maine, whose enthusiasm, knowledge, and interest in the geology of northern Maine is appreciated, and whose assist- - ance in the field is gratefully acknowledged. DISCUSSION Very little new paleobotanical information on Devo- nian floras of Maine has been presented since David White's (1905) study of plant fossils from the Perry Basin along the seacoast in the southeastern part of the State. Dorf and Rankin (1962) recently discussed an assemblage of plant fossils from the Traveler Mountain area 60 miles southwest of Presque Isle, and Kriusel and Weyland (1941) have restudied much of Dawson's original material, some of which was ob- tained in the Perry Basin. Incidental occurrences of Psilophyton or other fragments of plants are men- tioned in various geologic reports. Devonian terri- genous deposits in the Acadian highlands of eastern North America tend to occur in local or provincial intermontane basins which make stratigraphic corre- lation more difficult. White's detailed consideration fully established the Late Devonian age of the Perry Formation, a matter upon which there had been long controversy. Arche eopteris, Leptophloeum, Barinophyton, and other plants are present in the Perry Formation that have not been found in the Mapleton Sandstone. Apart from similarities in the intermontane types of sedi- ments, there is little to suggest that the Perry and Mapleton Formations are correlative. Dorf and STRATIGRAPHY AND PALEONTOLOGY Rankin have interpreted their Trout Valley psilophytic material as indicative of late Early Devonian age. The age differences between their Psilophyton flora and that of the Winslow quarry characterized by psilophytes and protoarticulates, is not nearly as clear as the distinction from the Late Devonian flora of the Perry Basin, in spite of a greater difference in sedi- mentary facies. It may be premature to think of the age relations of these deposits as well established. Barrandeina is characteristic of the lower Givetian in Bohemia. It has not been widely identified else- where. Outside of the Bohemian area, Kriusel and Weyland (1933) admit that only Hgeg's species from western Norway has been correctly identified with Barrandeina. They believe that all the American specimens White referred to this genus are unidentifi- able, and suggest that stems of this type might also be confused with those of Pseudobornia (Kriusel and Weyland, 1983, 1941). I am not convinced that White's report of the genus from the Perry Formation is in error, although further evidence is badly needed. It is possible that the Perry Formation may be a little older than White believed (still well within the Upper Devonian, possibly "Portage" rather than "Chemung") ; Jahn's (1903) and later studies appar- ently were not available to White and he did consider the plant remains from Barrande's H (h-i) stage, which he drew on for comparison, to represent a Late, rather than Middle, Devonian assemblage. Jahn showed that the Srbsko beds of Krejci occur below the zone of Stringocephalus burtini. Thus, if the oc- currence of Barrandeina from the Perry Basin can be substantiated, it might represent the youngest record of the genus. The genus Calamophyton is particu- larly characteristic of the lower Givetian in the Rhine- land and in Belgium. Marine fossils as well as other plants, such as Pseudosporochnus and numerous psilo- phytes, are in common within the Givetian of western Europe so that the similarity in age of these occur- rences is fully authenticated. Hueber and Grierson's report (1961) of PsilopAhyton princeps var. ornatum from early Upper Devonian beds appeared while Dorf and Rankin's paper was in press. More recently, Grierson and Banks (1963) show Prepanophycus gaspianus Dawson, also reported at Trout Brook, is present at least as high as the Tioughniogan stage of the Middle Devonian in New York. Drepanophyeus spinosus is characteristically associated with the Middle Devonian Srbsko assem- blage in Bohemia. Plants similar to Taeniocrada, Aphyllopteris, and Hostimella that Dorf and Rankin report at the Trout Brook localities also are present at the Winslow quarry and, in view of Grierson and SCHOPF Banks report, the fact that Drepanophycus has not yet been found there cannot be assigned weight in age determination. It seems clear now that the traditional Early Devonian associations of Psilophyton and Drepanophycus may easily be given an undue promi- nence. At present the Early Devonian age assign- ment of the Trout Brook assemblage seems principally to depend on identification of one fragmentary speci- men of Sporogonites. This positive evidence may be highly significant but it is undeniably scanty. Banks (1961) has pointed out that many of the Devonian genera "enjoyed a great vertical range," and Seward (1933, p. 130) expressed uncertainty as to whether Halle's original Roragen source for Sporogomnites was "of Lower or possibly of Middle Devonian age." Un- der these circumstances the greater emphasis probably should be placed on presence of plants like Barren- deina and Calamophyton for interpretation of age relations. Nevertheless, plants from the Mapleton Sandstone identified as Barrandeina (%) and Calamophyton are not identical with European plants, and not enough is known about them for the specific interpretation of evolutionary sequences. In comparison with plants of the western European assemblage, B. (?) aroostookensis might be slightly more specialized in foliar develop- ment, but C. forbesii seems to nearly duplicate some European material in arrangement of sporangiophores. Both types of plants are complexly organized and, taken altogether, they indicate a stage of evolutionary development in both groups which is very close to that shown by the genera in their European occur- rences. They surely represent a very similar ecologic plant association. Within the limits imposed by pos- sible inaccuracies of this paleontologic method, it seems most reasonable therefore to suppose that the age of the Mapleton Sandstone is also early Givetian, probably comparable to the Tioughniogan stage of the American standard section. REFERENCES Ananiev, A. R., 1959, Vazhneyshie mestonakhozhdeniya Devon- skikh flor v sayano-altayskoy gornoy oblasti [The most important Devonian floral localities of Saian-Altai Moun- tains Oblast]: Izdatel'stvo Tomskogo Univ., Tomsk [Punp. Tomsk Univ.)], 99 p., 25 pl., 22 figs., chart. Banks, H. P., 1961, The stratigraphic occurrence of Devonian plants with application to phylogeny, in Phylogeny of Tracheophyta symposium in Recent advances in Botany: Univ. Toronto Press, p. 963-968. D49 Dorf, Erling, and Rankin, D. W., 1962, Early Devonian plants from the Traveler Mountain area, Maine: Jour. Paleon- tology, v. 36, p. 999-1004, 1 pl., 1 fig. Grierson, J. D., and Banks, H. P., 1963, Lycopods of the Devo- nian of New York State: Palacontographica Americana, v. 4, no. 31, p. 217-295, pl. 32-42, 9 tables. Hgeg, Ove Arbo, 1931, Notes on the Devonian flora of western Norway: Det Kgl. Norske Vidensk. Selsk. Skr., Trondheim, no. 6, p. 1-33,.8 pl., 2 figs. 1942, The Downtonian and Devonian flora of Spits- bergen: Norges Svalbard- Og Ishavs-Undersgkelser Skr., no. 83, 228 p., 62 pl., 35 figs. Hueber, F. M., and Grierson, J. D., 1961, On the occurrence of Psilophyton princeps in the early Upper Devonian of New York: Am. Jour. Botany, v. 48, no. 6, p. 473-479, 15 figs. Jahn, J. J., 1903, Ueber die Etage H im mittel-bohmischen Devon: Verhandl. K. K. Geol. Reichsanstalt, Jahrg. 1903, p. 73-79. Kriusel, R., and Weyland, H., 1923, Beitrige zur Kenntnis der Devonflora: Senckenbergiana, v. 5, no. 5/6, p. 154-184, pl. 6-9. 1926, Beitrige zur Kenntnis der Devonflora II: Abh. senckenberg. naturf. Ges., v. 40, no. 2, p. 113-155, pl. 3-17, 46 fig. 1929, Beitrige zur Kenntnis der Devonflora III: Abh. senckenberg. naturf. Ges., v. 41, no. 7, p. 315-360, 15 pl., 34 fig. 1933, Die Flora des bohmischen Mitteldevons: Palacon- tographica, v. 78, Abt. B, no. 1/2, p. 1-46, pl. 1-7, 39 fig. 1941, Pflanzenreste aus dem Devon von Nord-Amerika: Palacontographica, v. 86, Abt. B, no. 1/3, p. 1-78, pl. 1-15, 15 fig. Leclereq, Suzanne, 1940, Contribution a etude de la flore da Devonien de Belgique: Acad. Roy. de Belgique Mem., v. 12, no. 3, p. 1-65, pl. 8, 10 fig. Leclercq, Suzanne, and Andrews, H. N., Jr., 1960, Calamophyton bicephalum, a new species from the Middle Devonian of Belgium: Missouri Bot. Garden Annals, v. 47, no. 1, 23 p., 5 pl., 16 fig. Leclereq, Suzanne, and Banks, H. P., 1962, Pseudosporochnus nodosus sp. nov., a Middle Devonian plant with cladoxyla- lean affinities: Palacontographica, v. 110, Abt. B., no. 1-4, p. 1-34, pl. 1-10, 7 fig. Potonié, H., and Bernard, Ch., 1903, Flore Dévonicene de etage H de Barrande: Leipzig, Raimund Gerhard and Wolfgang Gerhard, 68 p., 156 fig. Schmidt, Wolfgang, 1958, Pflanzen-reste aus der Tonschicfer- Gruppe (unteres Siegen) des Siegerlandes. II Pachytheca reticulata Corsin aus den Betzdorfer Schichten nebst neuen Beobachtungen an Pachytheca: Palacontographica, v. 104, Abt. B, no. 1-3, p. 1-38, pl. 1-5, 2 fig. Seward, A. C., 1933, Plant life through the ages: Cambridge Univ. Press. Stur, D. R. J., 1882, Die Silur-Flora der Etage H-h;, in Bohmen: K. Akad. Wiss., Sitzungsb., math. naturw. Classe, [Wien}, v. 84, Abt. 1, p. 330-391, 5 pl. White, David, 1905, Paleontology, chap. III of Smith, G. O., and White, David, The geology of the Perry Basin in southeastern Maine: U.S. Geol. Survey Prof. Paper 35, p. 35-84, pl. 1-6. Zimmermann, Walter, 1959, Die Phylogenie der Pflanzen: Stuttgart, Gustav Fischer Verlag, 777 p., 331 fig. % GEOLOGICAL SURVEY RESEARCH 1964 RADIOMETRIC AGES OF ZIRCON AND BIOTITE IN QUARTZ DIORITE, EIGHTS COAST, ANTARCTICA By AVERY ALA DRAKE, JR., T. W. STERN, and H. H. THOMAS, Washington, D.C. Work supported by the National Science Foundation Abstract.-Zircon and biotite separated from quartz diorite of the Eights Coast area, Antarctica, were found to have lead- SPEEEEELLT L Tha n in uid Seok l oem ier t acd guan gong y - alpha and potassium-argon ages of 150+200 m.y. and 97+5 [ m.y., respectively. This quartz diorite is both petrographically | and chemically distinct from Andean plutonic rocks. The zircon age suggests that the Eights Coast-Thurston Island composite batholith is at least middle Mesozoic in age. If so, the younger biotite age possibly reflects later heating of | the area during the Late Cretaceous Andean orogeny. | (13; Antarctic Weddell 605 5 %Peninsula 1 $ 4 Sea Plutonic rocks exposed on Thurston Island and along the Eights Coast of the Bellingshausen Sea, Antarctica (fig. 1), consist mostly of hornblende- Mamxberite biotite-quartz diorite (Craddock and Hubbard, 1961; Tos Drake, 1962). These rocks are thought to belong to a | re , w”; composite batholith that is predominantly quartz 2 Mountains §\\““'t 3 Sun w diorite but which also has granodiorite, adamellite, and Bellinghause" Ellsworth £ a s resis P a ea %> minor gabbro phases. The batholith is intrusive into } M°un§fw§21 (tury o f i 3 8 us 4 Thiel metasedimentary rocks on Thurston Island and at caw esert f munis 088" $72 Mountains ~ hg *- C t places along the Eights Coast, and into leucocratic augite norite near lat 72°35'37" S., long 95°07°00" W. | The batholithic rocks are cut by abundant mafic dikes _| (K? 4+ x g (nt Jones Mountains l | Thurston Islan (Craddock and Hubbard, 1961; Drake, 1962). In ad- | dition, the quartz diorite probably is intruded by fine- to medium-grained pink granitic rocks that range Amindsen from granodiorite to granite and are characterized by Sea abundant myrmekite. The intrusive relation is in- ferred from inclusions of white quartz diorite in pink granite seen only in float. One sample of quartz diorite (table 1) sufficiently large for age determination was collected from the ette" ssl Eights Coast at a station informally known as "Peel- Ez kes m-. er's Pinnacle," lat 72°34'56" S., long 9302300” y s n - ace Sec map.of Vest Aniatotice Showing saimplo February 1961. A lead-alpha age of zircon concen- locality (X) on the Eights Coast. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D50-D53 D50 DRAKE, STERN, Tapur 1.-Chemical analysis, C.I.P.W. norm, and mode of quartz diorite from lat 72°34'56"" S., long 98°28'00" W., Eights Coast, Antarctica Chemical analyist ! C.LP. W. norm Mode * Constituent | Weight Mineral Percent Mineral Volume percent percent $10;.'. ... 62.9 | Quarts..__.. 17. 8) Plagioclase 60. 6 Al;O;.... ..| 17. 2 | Orthoclase... 7. 2) Quartz...... 22.5 FeqO3. ._.. 1.0 | Albite....._.| 88.2) Blotite:.... 7.1 Feo..:.... 2. 4 | Anorthite 23. 4) Hornblende.. 6. 1 MeO... . 1. 8 (Wo, 2.1). 1. 6 Cad..:...: 6. 2 | Diopside 4. 0| Magnetite- . 8 NO.:... 4. 5 (En, 1.5) ilmenite. 1.2 (Fs, 0.4) Apatite. .._. ~B H;0+..... . 60, Hypersthene. 3. 8 Zireon...._. Pr: 10 -.... . 05) Magnetite__. 2. 8| Sericite_._. .. Tr. . 97) IImenite__. .. 1. 8| Epidote.___. Tr. . 44] Apatite... 1. 0| Myrmekite_. 'Ir. . 08 Total:. .... 100. 0 Total. _ _|100. 24 ' By rapid methods; analysts: Paul Elmore, Samuel Botts, and Gillison Chloe. * Based on 2,000 points counted by the Chayes method. * Average composition is sodic andesine, about as determined optically. trated from this sample (table 2) is the first of this type to be reported from this area. The zircon age of 150+20 million years suggests that the quartz dio- rite is at least as old as mid-Mesozoic (early Jurassic). Biotite concentrated from the same sample was dated by the potassium method (table 3) at 97+5 my. This biotite age is considerably younger, and suggests another orogenic event in the early Late Cretaceous. The rocks of the batholith are medium to coarse grained, and very light gray to white, although some plagioclase grains are tannish due to alteration. The rocks are fresh to slightly weathered ; iron oxide coat- ings are fairly common on joint surfaces. Other joints are filled by white adamellite pegmatite. The quartz diorite of the dated sample has a well-developed folia- tion marked by alined biotite, hornblende, and plagio- clase. In other exposures along the Eights Coast and on Thurston Island, related rocks are massive to well foliated. Float at the sample site includes a number of specimens of strongly mylonitic quartz diorite, suggesting that a shear zone is probably present at the locality. Microscopic study shows that much of the plagio- clase has oscillatory zoned andesine cores with caleic oligoclase rims. Many plagioclase crystals are broken, and zones of mortar structure are present. Quartz occurs both as large grains interlocking with plagio- clase and in pockets of small grains interstitial to the feldspar and large quartz. Brown and green biotite form at the expense of hornblende. Many of the bio- tite flakes are kinked, suggesting deformation subse- quent to crystallization. Trace amounts of myrmekite D51 occur as interstitial patches. Small zircon crystals occur as separate grains in plagioclase, quartz, biotite, and hornblende. Relatively abundant quantities of sphene are spatially related to altered hornblende, as are minor quantities of magnetite-ilmenite. The quartz diorite has been deformed locally, subse- quent to its emplacement, as is shown by the broken plagioclase, areas of mortar structure, and kinked biotite. Late alteration and partial recrystallization is suggested by the formation of biotite at the expense of hornblende. The rock has not completely recrystal- lized, however, as the minerals interlock in a primary igneous fabric; the feldspars, though locally broken, are subhedral; and the delicate, euhedral oscillatory zonation is preserved in the plagioclases. Little is known of the geologic age of the plutonic rocks of West Antarctica in general and of the Bel- lingshausen Sea area in particular. Granitic rocks of possible Tertiary age are present in the southern part of the Antarctic Peninsula (Knowles, 1945); they probably belong to the Antarctic Peninsula Andean intrusive suite which was assigned a Late Cretaceous or early Tertiary age by Adie (1955). Late Cretaceous to early Tertiary isotopic ages were reported by Hal- pern (1962) on minerals from intrusive rocks in the northern part of the Antarctic Peninsula that are petrographically similar to those farther south studied by Knowles and Adie. Older intrusive granites in the Marguerite Bay area were recognized by Adie (1954), who arbitrarily assigned them an early Paleozoic age. To the south of Eights Coast in the Thiel Mountains, Ford and others (1963) and Aaron and Ford (1963) report lead-alpha (zircon) and potassium-argon (bio- tite) ages that suggest Precambrian and early Paleo- zoic metamorphic events. In the absence of geologic data the Bellingshausen Sea area has been assumed to lie within a Mesozoic fold belt coextensive with the Antarctic Peninsula. Hamilton (1963) interpreted the batholith exposed along Eights Coast and on Thurston Island as being continuous with the Andean batholith AND THOMAS TaBu® 2.-Lead-alpha age of zircon from quartz diorite, Eights Coast, Antarctica l Alpha counts | Lead ! | Calculated Sample Location per milligram | (ppm) | age? (m.y.) per hour 3012. .:., ..i Lat. S., 173.| 10.7 | 150 %20 long. 93°23'00"' W. ' Determination by Harold Westley. All values are averages of duplicate determinations. ? Age equation: ¢+=c-Pb/alpha, where c=constant, 2,485 for Th/U=1, Pb=lead in ppm, and alpha=a/mg-hr. Age is rounded to nearest 10 m.y. D52 GEOCHRONOLOGY TaBugr 3.-Analytical data and potassium-argon age of biotite from quartz diorite, Eights Coast, Antarctica [Analysts: H.H. Thomas, R. F. Marvin, P. L. D. Elmore, and H. Smith] Sample Location K0 K# *Ar40 *Ar#/ KA Age (m.y.) (percent) (ppm) | (ppm) (percent) Lat 72°%34'506'' S., long 985°25'00'' W._..._.__.__ 9. 14 9. 26 | 0. 0539 88 0. 00582 97 +5 Symbol: *Radiogenic. Decay constants, K®: 0.585 X 10-"/yr (electron capture), 4.72 X 10-"/yr (beta decay). Abundance, K": 1.22 X 10-~! g/g K. of the Antarctic Peninsula. The quartz diorite of the Eights Coast differs from the Andean quartz diorites of the Antarctic Peninsula in its distinctive white to very light gray color, its flow structure, and its lack of inclusions which are characteristic of the Andean quartz diorites. It is more quartzose and contains in general a more sodic andesine. The petrochemistry of the rocks is strikingly different as well (fig. 2). In their study of the Jones Mountains, Craddock and others (1963) found that volcanic rocks uncon- formably overlie a basement terrane of pink to tan granite that is cut by both basaltic and felsic dikes. Muscovite in the granite has a potassium-argon age of m.y. The felsic dike rock, a quartz latite por- phyry, has a whole-rock potassium-argon age of 104+4 my. Age relations of the basement granite and the felsic dikes to the Eights Coast quartz diorite are not known. Two of the geologic stations established during the 1961 Bellingshausen Sea expedition are near the Jones Mountains, but only typical Eights Coast quartz dio- rite and older gabbro are exposed. Early or middle Mesozoic ages have rarely been re- ported from Antarctica, and most of those have been of diabase sills, principally from Victoria Land (Mc- Dougall, 1963). Miller (1960), however, reports po- tassium-argon ages of 176 to 199 m.y. on biotite and muscovite separated from quartz-mica schists from the South Orkney Islands. These ages suggest a meta- morphic event in Late Triassic to Early Jurassic time. Craddock and others (1964) report a rubidium-stron- tium age (biotite) of 280 m.y. (late Carboniferous) for gneiss from Thurston Island. This gneiss is not the same unit as the quartz diorite described herein, as it is reported to be a granular garnet-bearing quartz diorite gneiss that is compositionally layered. This gneiss is interpreted as having a metamorphic origin (Craddock and others, 1964). The age of the biotite agrees closely with the age of intrusive felsites, 104+4 my., reported by Craddock and others (1963) from the Jones Mountains. It seems reasonable to suggest that biotite formed, or recrystal- lized, as a result of Late Cretaceous Andean plutonism in the Eights Coast-Jones Mountains area. It is pos- sible, also, that a single lead-alpha age can be com- pletely erroneous, as old zircon ages have been reported from known young intrusive rocks. In the present case, however, it is felt that the Eights Coast batholith is indeed older than the Andean batholith of the Ant- arctic Peninsula, as the rocks are dissimilar, an Early Triassic potassium-argon age has been reported by Craddock and others (1963) from a nearby area, and older plutonic rocks have been reported from the Ant- arctic Peninsula itself. A substantial part of the crystalline rocks of the area, therefore, is not Late Cretaceous in age as has been assumed, but is probably at least as old as middle Mesozoic. The possibility cannot be eliminated that the Mesozoic zircon age re- ported herein reflects the age of a younger metamor- phic event and that the quartz diorite is of late Paleo- zoic age. An Femic or Ab Quartz Feldspar Ficur® 2.-Larsen plots showing normative comparison of rocks of the Eights Coast batholith (solid lines) with those of the Andean granite-gabbro intrusive suite (dashed lines). Sym- bols: X , data from Adie (1955) ; © , data from samples collected by Drake on the Eights Coast; and A, data from samples collected by Drake on the Antarctic Peninsula. Numbers or lines in triangle are sample numbers. DRAKE, STERN, AND THOMAS It appears that the Antarctic Peninsula orogenic belt does follow along the Eights Coast as far as Thurston Island, although events as young as Andean are apparently of minor importance in this area. More data are needed, of course, to better interpret the tim- ing of orogenic events in this little known region. REFERENCES Aaron, J. M., and Ford, A. B., 1964, Isotope age determinations in the Thiel Mountains, Antarctica [abs.]: Geol. Soc. America Spec. Paper 76, p. 1. Adie, R. J., 1954, The petrology of Graham Land, I. The basement complex; early Paleozoic plutonic and volcanic rocks: Falkland Islands Dependencies Survey, Sci. Rept. 11, 22 p. 1955, The petrology of Graham Land, II. The Andean granite-gabbro intrusive suite: Falkland Island Depend- encies Survey, Sci. Report 12, 39 p. Craddock, Campbell, and Hubbard, H. A., 1961, Preliminary geologic report on the 1960 U.S. expedition to Belling- shausen Sea, Antarctica: Science, v. 133, no. $456, p. 886- 887. Craddock, Campbell, Bastien, T. W., and Rutford, R. H., 1963, Geology of the Jones Mountains area, West Antarctica: #5 D53 Cape Town, Sci. Comm. for Antarctic Research-Internat. Union of Geol. Sciences Symposium on Antarctic Geology. Craddock, Campbell, and others, 1964, Rubidium-strontium ages from Antarctica: Geol. Soc. America Bull., v. 75, p. 237- 240. Drake, A. A., Jr., 1962, Preliminary geologic report on the 1961 U.S. expedition to Bellingshausen Sea, Antarctica: Science, v. 135, no. 3504, p. 671-672. Ford, A. B., Hubbard, H. A., and Stern, T. W., 1963, Lead- alpha ages of zircon in quartz monzonite porphyry, Thiel Mountains, Antarctica-a preliminary report: Art. 208 in U.S. Geol. Survey Prof. Paper 450-E, p. E105-E107. Halpern, Martin, 1962, Potassium-argon dating of plutonic bodies in Palmer Peninsula and southern Chile: Science, v. 138, no. 3546, p. 1261-1262. Hamilton, Warren, 1963, Tectonics of Antarctica, in Backbone of the Americas: Am. Assoc. Petroleum Geologists Mem. 2, p. 4-15. Knowles, P. H., 1945, Geology of southern Palmer Peninsula, Antarctica: Am. Philos, Soc. Proc., v. 89, no. 1, p. 132-145. McDougall, Ian, 1963, Potassium-argon age measurements on dolerites from Antarctica and South Africa: Jour. Geophys. Research, v. 68, no. 5, p. 1585-1545. Miller, J. A., 1960, Potassium-argon ages of some rocks from the South Atlantic: Nature, v. 187, no. 4742, p. 1019-1020. GEOLOGICAL SURVEY RESEARCH 1964 QUALITATIVE X-RAY EMISSION ANALYSIS STUDIES OF ENRICHMENT OF COMMON ELEMENTS IN WALLROCK ALTERATION IN THE UPPER MISSISSIPPI VALLEY ZINC-LEAD DISTRICT By JOHN W. HOSTERMAN, ALLEN V. HEYL, and JANICE L. JOLLY, Beltsville, Md. Work done in cooperation with the Wisconsin Geological and Natural History Survey Abstract.-Mineral alteration in a carbonaceous shale bed associated with a hydrothermal zinc-lead deposit in the Upper Mississippi Valley district is marked by the addition and migration of at least seven common elements (iron, manganese, titanium, potassium, silicon, aluminum, and magnesium) by ore-forming solutions. Calcium was leached from the ore body and moved to the edge of the alteration aureole. The sugges- tion is made that magmatically heated connate brines may have deposited the ore and altered the wallrocks. Alteration of clay minerals associated with zinc- lead ore deposits in the Upper Mississippi Valley dis- trict was investigated by Heyl and others (1964) dur- ing 1960-63. This earlier study led to further investi- gations of the same suite of wallrock samples from the Thompson-Temperly mine in southwestern Wisconsin. Qualitative X-ray fluorescence analyses were made of samples to determine possible variations in relative quantities of the principal elements that are in the basal shale unit of the Quimbys Mill Member of the Platteville Formation in and adjacent to the Thomp- son ore body. The Thompson-Temperly mine is at the southwest edge of New Diggings, Wis., a village about 10 miles north-northeast of Galena, Ill. It is in the highly productive south-central part of the Upper Mississippi Valley zinc-lead district of southwest Wisconsin, northwest Illinois, and northeast Iowa (fig. 1). The mine is opened by a truck incline that slopes to the northeast into the small Temperly ore body. From this body a truck haulage crosscut extends for about 1,500 feet into the large Thompson ore body (fig. 3). Madison © 43° |- - UPPER MISSISSIPPI VALLEY > ZINC-LEAD DISTRICT " me THOMPSON __Rife "___ "_ wisconsmm ___ __ ws ILLINOIS 0 110 20.MILES (aer. FraurRrE 1.-Index map showing location of the Thompson-Tem- perly mine. The samples studied were taken from the Thompson ore body and alteration aureole, the barren wallrock zone between the two ore bodies, and the Temperly ore body and alteration aureole. The Quimbys Mill Member of the Platteville For- mation is a thin dolomite, limestone, and shale unit of distinctive lithology that can be traced for many tens of miles. At the Thompson-Temperly mine, where the member was studied, it passes from the Temperly ore body and its surrounding alteration aureole into a barren rock zone and then into the Thompson ore body and its alteration aureole. This study indicates that variations in the concentration of the elements in the U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D54-D60 D54 HOSTERMAN, HEYL, AND JOLLY wallrock may be helpful in prospecting for ore in the mine and in exploratory drilling elsewhere in the Upper Mississippi Valley district. GEOLOGY The two zinc-lead ore bodies of the Thompson- Temperly mine, like many others in the Upper Missis- sippi Valley district, occur chiefly in the Quimbys Mill Member of the Platteville Formation, in the Decorah Formation, and in the lower part of the Galena Dolo- mite (fig. 2), all of which are of Middle Ordovician age. The Temperly ore body is a small irregular linear mass, whereas the Thompson ore body is an elliptical doughnut-shaped mass (fig. 3). Mining sub- sequent to preparation of figure 3 confirms that the shape inferred here is basically correct. The ore is in veins, replacements, and impregnations along small reverse and bedding-plane faults related to gentle folds. The main primary minerals in the ore bodies are quartz (mostly cherty jasperoid), dolomite, 21/7 illite, microcline, pyrite, marcasite, sphalerite, galena, cobaltite, chalcopyrite, barite, and calcite. Unlike galena in most deposits in the vicinity, galena in the Thompson-Temperly mine is common only locally in the ore bodies. The Quimbys Mill Member (fig. 2) consists of dark- brown dolomite and limestone with thin carbonaceous D55 shale partings and a carbonaceous shale bed at the base. The limestone is fine grained, dense, sublitho- graphic, and has a conchoidal fracture. The basal dark-brown shale bed is a very persistent and uniform marker bed about 3 inches thick. Because it can be accurately traced throughout mineralized and barren areas, this shale bed was selected for detailed sampling in the Thompson-Temperly mine. Ore solutions have produced alteration aureoles (fig. 3) in the host rock limestone, shale, and, to a lesser extent, in dolomite surrounding the deposits. The aureoles extend laterally as much as 200 feet from the sides of the ore bodies, and are known from drilling to extend out much shorter distances from the top and bottom of the bodies. The alteration aureoles result from a combination of six main processes (Heyl and others, 1959, p. 101-108; 1964) : solution, dolomiti- zation, silicification, development of sanded dolomite, clay- mineral alteration, and low-temperature felds- pathization marked by the formation of microcline. Solution has considerably thinned the limestone of the Quimbys Mill Member as well as other carbonate beds above and below it (Reynolds, 1958, p. 157-159). The calcite in the carbonaceous shale bed at the base of the Quimbys Mill has been largely replaced by less soluble dolomite, thus preventing much thinning. Fossils and some shale beds have been silicified, but less markedly Frour® 2.-Stratigraphic column of the Platteville and Decorah Formations and lower part of the Galena Dolo- mite in the Upper Mississippi Valley zinc-lead district. C Member and Thickness of Fo tion Atk legs rma subdivision Description foni'tffreedt) c e Dolomite, drab to buff, thick- to thin-bedded, cherty; Galena | Prosser Crazy AZA Receptaculites abundant. $f Dolomite and limestone, light-gray, argillaceous; 20 lon he grayish-green dolomitic shale. Dolomite Limestone, brown, fine-grained, thin-bedded, nodular, 12-16 32- p 1—1 4 conchoidal; dark-brown shale. 44 ecorah Guttenberg t Shale [=d ~d , ; ; ; rI 7 lI Dolomite and limestone, dark-brown, fine-grained, Quimbys Mill accupril sugary, medium-bedded, conchoidal; dark-brown 0-18 -I shale, especially at base. McGregor _ |/-l7- Limest d dolomite, light fi ined 13-18| 55 j imestone and dolomite, light-gray, fine-grained. - = Platteville Limestone --- 75 t +: 1 Limestone, light-gray, fine-grained, thin-bedded, 12-17 Pecatonica nodular, conchoidal. polomite Dolomite, brown, medium-grained, sugary, thick-bed- 20-24 Glenwood ded; blue gray where unweathered. Shal *. Shale, green, sandy. 0-3 St. Peter Sandstone, quartz, medium- to coarse-grained, poorly #0 + cemented, crossbedded. D56 in these two ore bodies than in some nearby ones, such as those in the Hoskins mine (Heyl and others, 1959, p. 105-107; Agnew, 1955, p. 492). - Within the ore bodies the previously dolomitized limestones have been sanded, forming a friable or noncoherent mass of dolo- mite crystals in which the cementing bond between the erystals has been weakened or removed by intergranu- lar solution. Wavy bands of brown shale, the residue of solution, separate the layers of sanded dolomite. GEOCHEMISTRY The amount of shale relative to carbonate rocks in- creases within the aureoles, and shale becomes the major component within the ore bodies. ALTERATION STUDIES In 1960 the Quimbys Mill Member was first sampled at regular intervals in the long haulageway between the Thompson and Temperly ore bodies. The samples, though restricted to the Quimbys Mill Member, were Unaltered dense sublithographic limestone TT-62-15 TEMPERLY ORE BODY TT-62-19 TT-62-5 TT=62-7 ~STT-62-8 2 TT-62-9~ TT-62-10 THOMPSON ORE BODY EXPLANATION »s3y Mine workings Chevrons point downslope Alteration aureole Dashed line shows margin where known or inferred. _ Scratch boundary used where limits of essense! Iterati t alteration nol kiown Portal and opencut fale r P m Inclined shaft Approximate margin of ore Fiaur®E 3.-Sketch of the Thompson-Temperly mine, showing approximate location of shale samples. Cans ao. body nd TT-62-20 p Bottom of shaft TEE—— Reverse fault, showing dip Bench and relative movement 4 Dashed where approximately located; D, downthrown side; U, upthrown Sample location and F o A side number SE:COR. BEC: 27, T. 1 N.,.B. 1 °G. Mapped by A.V. Hey! and M. A. Brock , 1960 0 500 FEET 1 Et pct 2d Map is a horizontal section of the ore bodies at an elevation where they lie within the Quimbys Mill Member of the Platteville Formation of Middle Ordo- vician age. HOSTERMAN, HEYL, AND JOLLY scattered vertically throughout the member in both limestone and shale and in altered and unaltered rocks. The initial sampling showed that the basal shale bed was better than the limestone for clay-mineral altera- tion studies because of its more uniform lithology. Moreover, clay is very sparse in the limestone, and the acid treatment required to separate the clay from the limestone may alter the clay. In 1962 the basal shale bed was sampled at intervals of about 30 feet within the Thompson ore body and in the alteration aureole on the southwest side of the Thompson ore body, at intervals of 30 to 200 feet through the barren zone be- tween the two ore bodies, and at a few places in the Temperly ore body and the alteration halo on either side of it (fig. 3). All 24 samples were first studied by X-ray diffrac- tion (Heyl and others, 1964), using CuKa radiation, to determine the whole mineral content (varieties and relative amount). A select few samples, which gave the complete range of variations between the unaltered rock and rock from the Thompson ore body, were treated to remove the calcite and dolomite from the carbonaceous shale. Six selected samples were further studied by X-ray emission, using a platinum-target tube as a primary source of X-rays, and lithium fluo- COUNTS PER SECOND (RELATIVE) | | % k------ Ore Aureole TY-65-1 % TT-62-4 § TT-62-7 COUNTS PER SECOND (RELATIVE) C D57 ride as a diffracting erystal. The samples were TT- 62-1 from the center of the Thompson ore body; TT-62-4, TT-62-7, and TT-62-9 from the inner, cen- ter, and edge, respectively, of the alteration auerole surrounding the ore body; and TT-62-11 and TT-62- 13 from the unaltered carbonaceous shale. Normally, X-ray emission is used for determining the quantity of elements present in a given sample, and when compared with known chemical standards the elements are reported in percent oxide. Since only the relative amount rather than the calculated percentage of each element was necessary in the present study, no attempt was made to assign percentage values to the 8 elements (iron, manganese, titanium, calcium, potas- sium, silicon, aluminum, and magnesium) found in the 6 samples. These X-ray emission data are illus- trated by a series of graphs for each element on figure 4. The ordinate is measured in counts per second, with the highest count obtained for each element arbi- trarily given the maximum scale height; all other counts for the particular element are shown by bars proportional in length to that maximum. This pro- cedure emphasizes the variation of each element from sample to sample but does not show the relative abun- dance of the different elements. Each shale sample 7 Ca © ~ Unalitered wallrock TT-62-11 § TT-62-13 TT-62-9 Fiaurs 4.-Graphs showing relative amounts of 8 elements in 6 samples of shale from the Thompson-Temperly mine, as determined by X-ray emission analysis. D58 used in the X-ray emission analysis was ground and homogenized to pass through a 230-mesh sieve and pressed into a large pill. Several reruns of each sample were made and the results were found to be reproducible. The graphs illustrate two outstanding features. All the elements, except calcium, give the highest count in sample TT-62-1, which is from the center of the Thompson ore body. Also, all the elements, except calcium and magnesium, give the lowest count in sample TT-62-9, which is from the outer edge of the alteration aureole. Calcium shows an inverse relation to all the other elements. The small variations of the elements in samples TT-62-11 and TT-62-13 from the unaltered host rock show the uniformity of the car- bonaceous shale bed away from the ore bodies. Pre- liminary results of semiquantitative spectrographic analyses by Helen W. Worthing of many of these samples confirm the trends that are shown on figure 4. Figure 5 shows graphically the quantities of potassium and magnesium in 18 of the 24 samples of the carbon- aceous shale. The amounts of potassium and mag- nesium in the shale bed within the ore bodies are 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 | GEOCHEMISTRY larger than the amounts in the aureoles in the haul- ageway, and both elements are least abundant near the outer edges of the wallrock alteration zones. Fig- ure 6 shows graphically the quantities of aluminum, iron, titanium, and manganese in some of the samples from the Thompson ore body only. The quantities of these elements shown by the additional analyses fur- ther confirm the variations obtained by qualitative X-ray emission analyses on the similar samples. Cal- cium and silicon contents were for the most part greater than 10 percent, and hence were too high for semiquantitative determination by the method used. The X-ray diffraction information (Heyl and others, 1964, figs. 4 and 5) supports the data on figures 4 and 5. Calcite decreases with decrease in calcium from the outer edge of the alteration aureole toward the ore body, and the wallrock of the ore body contains only a trace of calcite. The only other calcite is in scattered crystals occurring as a late gangue mineral in the ores. Dolomite increases with increase in mag- nesium from the outer edge of the aureole to the ore body. Less quartz is present at the outer edge of the aureole than in the unaltered rock, but it becomes a Potassium Magnesium ~- 'a 0.5 § UNALTERED WALLROCK 1 1 1 4 6 7 8 10 12 13 14 TT-62-1 2 1 1 16 17 18 SAMPLE NUMBER Ficur® 5.-Results of semiquantitative spectrographic analyses of potassium and magnesium from the Thompson-Temperly mine. Results are reported in percent to the nearest number in the series 1, 0.7, 0.5, 0.3, 0.2, 0.15, and 0.1, and so forth, which represent approximate midpoints of group data on a geo- metric scale. 30 percent of the time. The assigned group for semiquantitative results will include the quantitative value about HOSTERMAN, HEYL, AND JOLLY predominant constituent in the inner part of the aureole and in the ore body. Illite, a clay-size diocta- hedral mica, is present in all samples. It occurs as an Md polymorph in the unaltered rock, a 1J/ polymorph in the alteration halo, and a 2J/ polymorph in the ore body. This change in polymorphic form is attributed to the potassium and aluminum added in the ore body (fig. 4), as well as to the decrease in water content in the ore body and alteration aureole (Heyl and others, 1964, p. 452). Migration of elements can be postulated from the data presented on figure 4. The large counts for al- most all elements, as shown by comparing the graphs of samples TT-62-1, TT-62-4, TT-62-7 with those of samples TT-62-11 and TT-62-13, indicated that iron, manganese, titanium, potassium, silicon, aluminum, and magnesium were, in part, epigenetic and were intro- duced with the ore-forming solutions. Samples TT- 62-4 and TT-62-7 show that most of the introduced elements (iron, titanium, potassium, especially silicon, and aluminum) also diffused and migrated beyond the ore zone to the inner part of the alteration aureole. The low counts in sample TT-62-9 for most elements indicate a decrease in the amount present at the edge of the alteration aureole and show that along with the introduction and outward migration, some leaching occurred at the edge of the aureole, and inward migra- tion of iron, titanium, potassium, silicon, and alumi- num occurred from the outer edge of the aureole. Magnesium shows a similar but larger leached zone. Calcium increases to the outer margin of the alteration aureole and decreases in the unaltered rocks, indicating that the ore solutions leached calcite from the ore body plus the inner part of the aureole and concentrated it in the outer fringe of the aureole. The leached zone suggests the presence of a diffusion front between the mineralizing solutions and the normal ground water at the time of deposition. The elements leached from the wallrock aureole were transferred inward by lateral secretion to the ore bodies, contributing to the total amounts of the iron deposited in pyrite and marcasite, the manganese deposited in the sphalerite and calcite, the potassium and aluminum deposited in illite and microline, the silicon deposited in quartz, and the magnesium deposited in dolomite. The titanium may be in several of these minerals, as anatase, or in the clay minerals. In the final stage. of deposition the calcium remaining in solution was deposited as calcite crystals in open spaces in the ore bodies. Part of the wallrock alteration, especially some silicification, dolomitization, and minor wallrock leach- ing, probably occurred prior to sulfide deposition by the ore-bearing solutions in the initial stages of min- 742-652 O-64--5 D59 eralization (Heyl and others, 1959, p. 97-98, 101-108). The main period of solution of the wallrock limestone and dolomite, however, probably began not too long before the start of sulfide mineralization, and con- tinued during sulfide deposition. The process appar- ently continued all through the period of sulfide depo- sition and ceased simultaneously as the last marcasite was deposited during the middle of the period of cal- cite deposition. The data available are not sufficient to clarify whether the bulk of the elements other than the sulfides that are found in the ore deposits and their aureoles were introduced by the heated connate waters possibly mixed with a smaller magmatic fraction, or whether they were hydrothermally leached from the wallrocks and redistributed in the ore deposits. Only a three-dimensional study backed by geologic mapping and detailed quantitative sampling, already in prog- ress, will probably yield enough data to answer this question. It is known by drilling that the aureoles extend 50 or 100 feet above ore bodies and 5 to 30 feet 7.0 5.0 sC Al 2.0 1.5 1.0 Fe 0.7 0.5 0.3 PERCENT 0.2 0.15 Ti 0.1 0.07 0.05 0.03 0.02 Mn i AUREOLE UNALTERED WALLROCK AEL OSS _ 1 1 4 7 8 12 13 SAMPLE NUMBER Fraur® 6.-Results of semiquantitative spectrographic analyses of aluminum, iron, titanium, and manganese from the Thomp- son ore body. Results are reported in percent to the nearest number in the series 1, 0.7, 0.5, 0.3, 0.2, 0.15, and 0.1, and so forth, which represent approximate midpoints of group data on a geometric scale. - The assigned group for semiquantitative results will include the quantitative value about 30 percent of the time. D60 below ; likewise, they do not extend far into the central core of elliptical ore bodies. The almost-uniform composition of the unaltered Quimbys Mill wallrock in the long haulageway indi- cates quite clearly that the source of redistributed elements in the Platteville Formation is restricted to the wallrocks themselves within the alteration aureoles. The volume of the altered rock is far too small to pro- vide more than a small proportion of the lead, zinc, and iron sulfides deposited in the ore bodies, but it is quite sufficient to provide for the increase in calcium in the narrow outer part of the aureoles (fig. 4), and in the calcite in the ore. The major increases in amount of all other elements in the ore bodies and in the wide inner part of the aureoles above the back- ground in barren wallrock (figs. 4, 5, 6) and the nar- row width of the outer leached part, suggest to the writers that the bulk of the elements were introduced by the ore-bearing solutions. A substantial lesser part of the elements was probably redistributed during mineralization and the accompanying alteration. Much of the added elements may have come from limestones, sandstones, and shales, through which the solutions passed; but also some may come from the heated con- nate waters themselves. In addition, further pre-ore mingling of connate and magmatic solutions may have provided some elements from the granitic basement rocks, and from the juvenile waters supplied by the igneous magma. Magmatically heated connate brines derived from the Illinois or Forest City basins may have provided the main solutions from which the ore bodies were de- posited. When heated the brines may have migrated updip through aquifers, deposited the ores, and altered the host rock when they were trapped beneath the cap of Upper Ordovician shale. Such concentrated heated brines may have formed diffusion fronts with dilute meteoric water already present in the wallrocks along fracture zones above the aquifers, and these diffusion fronts altered the host rocks and deposited the ores. Hall and Friedman (1963) have shown that the liquid inclusions in galena, sphalerite, and calcite from the Upper Mississippi Valley mining district contain nearly saturated brines similar in composition to present-day deep-seated connate waters of the Illinois GEOCHEMISTRY basin. These solutions are highly concentrated sodium- calcium chloride brines that have a relatively high deuterium concentration. Potassium and magnesium are fairly abundant in the liquid inclusions that formed during the main stages of sulfide deposition; the much more dilute solutions of the late calcite stages are relatively enriched in sulfate. Such con- centrated brines, especially if heated magmatically, would have provided solutions that could be trapped, could readily alter the wallrocks, and could add potassium, magnesium, and other major elements to the deposits. Bailey and Cameron (1951, p. 625, 626) found the filling temperatures (uncorrected for pressure) of fluid inclusions in the Upper Mississippi Valley dis- trict to range from 121°C to 75°C for sphalerite and 78°C to 50°C for stage-2 and stage-3 calcite. The lower filling temperature and the lower concentration of salts and deuterium in the inclusions in the calcite may be attributed to the dilution of heated brines by meteoric water during the late stages of mineraliza- tion. Such heated brines could well have provided the type of solutions that formed the alteration aureoles and the described changes in host-rock composition. REFERENCES Agnew, A. F., 1955, Application of geology to the discovery of zinc-lead ore in the Wisconsin-Illinois-Iowa district: Min- ing Eng., v. 7, no. 8, p. 781-795. Bailey, S. W., and Cameron, E. N., 1951, Temperatures of mineral formation in bottom-run lead-zinc deposits of the Upper Mississippi Valley, as indicated by liquid inclusions: Econ. Geology, v. 46, p. 626-651. Hall, W. E., and Friedman, Irving, 1963, Composition of fluid inclusions, Cave-In-Rock fluorite district, Illinois, and Upper Mississippi Valley zinc-lead district: Econ. Geology, v. 58, no. 6, p. 886-911. Heyl, A. V., Agnew, A. F., Lyons, E. J., and Behre, C. H., Jr., 1959, The geology of the Upper Mississippi Valley zinc-lead district: U.S. Geol. Survey Prof. Paper 309, 310 p. Heyl, A. V., Hosterman, J. W., and Brock, M. R., 1964, Clay- mineral alteration in the Upper Mississippi Valley zinc- lead district, in Clays and clay minerals: Proc. 12th Natl. Conf. on Clay and Clay Minerals, p. 445-453. Reynolds, R. R., 1958, Factors controlling the localization of ore deposits in the Shullsburg area, Wisconsin-Illinois zinc-lead district: Econ. Geology, v. 53, no. 2, p. 141-163. GEOLOGICAL SURVEY RESEARCH 1964 SUGGESTED EXPLORATION TARGET IN WEST-CENTRAL MAINE By F. C. CANNEY and E. V. POST, Denver, Colo. Abstract.-Stream-sediment sampling has suggested that the drainage basin of a stream tributary to Bean Brook in the Long Pond quadrangle, Somerset County, has a mineral poten- tial distinctly above average for the region. Analysis of active stream sediment indicated lead and zinc contents as high as 2,500 ppm and 7,000 ppm, respectively. The lead anomaly is the highest so far revealed in Maine by the regional geochemi- cal mapping program of the U.S. Geological Survey. The known exposures of quartz veins containing sparse bismuth- and silver-rich galena and pyrite appear to be inadequate to produce this intense anomaly. Reconnaissance geochemical drainage surveys have located a stream in the southern part of the Long Pond quadrangle in Somerset County, Maine, in which the active stream sediment contains as much as 2,500 parts per million lead and 7,000 ppm zinc. Although a heavy-metal anomaly has been known here for some time (Post and Hite, 1963), its apparent significance has recently increased. Reappraisal of the anomalous pattern in the light of a large quantity of geochemical data obtained by a regional geochemical mapping pro- gram during the past 2 years has shown that this lead anomaly is by far the strongest one yet found by the U.S. Geological Survey in Maine. Galena- and pyrite- bearing quartz veins are present in the drainage basin of this stream, but the exposed veins are not believed to contain enough lead to be the principal cause of the geochemical anomaly. Accordingly, the drainage basin of this stream is believed to be above average in mineral potential. The officially unnamed stream in which the lead and zinc anomalies occur, here named Pyrite Creek for convenience, is the northeastern branch of a major tributary to Bean Brook. Figure 1 presents the data of the detailed geochemi- cal survey along Pyrite Creek, reconnaissance geo- chemical data in the surrounding area, and the ap- proximate distribution of the major rock types. The rocks in the general vicinity of Pyrite Creek (fig. 1) are on the southeastern limb of the Boundary Mountain anticlinorium (Albee, 1961) and comprise quartz monzonite of probable Cambrian or Ordovician age, and metasedimentary rocks and diabase of Early Devonian age. The metasedimentary rocks are not exposed in the immediate vicinity of Pyrite Creek, but elsewhere in the area of figure 1 they include slate, metasiltstone, and fine-grained argillaceous sandstone of the Seboomook and Tarratine Formations (Boucot, 1961). These rocks are, in part, overlain conformably by a sheetlike body of altered diabase. The metasedi- mentary rocks rest unconformably on the quartz mon- zonite, and dip easterly at a moderate angle. The quartz monzonite in this area is typically coarse grained, pinkish green, and consists of quartz, pink euhkedral to subhedral phenocrysts of microcline, plagioclase, and a small amount of chloritized mafic minerals. In thin section, the plagioclase is moder- ately sericitized, the mafic minerals (probably prin- cipally biotite) are completely altered to chlorite, quartz is strained, and the rock is crisscrossed by an anasto- mosing network of tiny fractures healed with fine- grained granular quartz and sericite. The quartz monzonite at several places in the area of figure 1 is extensively silicified so that in hand specimen it resembles a dense pinkish-green felsite. Remnant outlines of the original crystals of the coarse- grained quartz monzonite can be seen in thin section within a groundmass of fine-grained granular quartz and sericite. The reconnaissance nature of our geo- logic mapping does not permit us to outline the areas of silicified rock on figure 1. A waterfall 20-25 feet high is present on Pyrite Creek about 700 feet upstream from the unpaved road in Parlin Pond Township. A 10- to 12-inch quartz vein, which strikes N. 70° W., and dips about 80° to the southwest is well exposed in a narrow gorge at the U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D61-D64 D61 D62 GEOCHEMISTRY 70°10" 45°35" C Tyr \ AY + 25:100 As \ ._ Area of \\ f report A: go A »\° f m \ 'A MAINE __ & Gilt a \ \»z } : Ms df Phin 5 F "* wie > \ 6 0 j C Na % me . =u. Pyritic quartz vein \ \~\y Va \ "o pig pice. it be \ .// 1 Nim \ -/// tane 223 iy xs,. [ils & v " ge > Saw Pip hor * ra + /l \\ <8 p \ 4 / y 7 - Galena-bearing outcrop hy + '\ fy £ x |A P % y y \o6 : 1 - $ l! y /\ os. \ g o 1 - \\ DIABASE QUARTZ MONZONITE METASEDIMENTARY . ROCKS ,\\~ ¥ Crear < g \\\ / MISERY GORE ung J AV/ <= Nudd 25: 100\2o/\-;/ G «\ <25:100 W‘Nsfifi’ ro Q‘ / - OND T0 p \ vA 1 P p \' 1 J weal &'25 PA \ * ho ags. Galena-pyrate-beanng 0:4000 5 # ales quartz vein 250 ma =. A MHZ \4.§ 7/0- A\\‘ "ssl + \' Y -+41500:7000 \ 4 - gullet. - 80 L ra \ cemeX yn" _ ,j@===-1i"~"' IY" _ MR" ] w" ss" | sf ¢" [__'=«- 2000 3500 17 Fang R [VZ & oe 25:100 | 1000:4000 [ JDM A I- ( 50:150 \,150:250 Fake Ph , 1 25:200 //~ - 25:75 4 gat 75:150 150 £ pyar g /. te. es. 75 150 § Po //// /// It Ir f—fi ge". e See 25:50 /. a id : P 0 2000 40IOO FEET L i i 1 1 EXPLANATION 20 obo 2000.) . . =.; a x cnAP Sampled locality Inferred contact Strike and dip of beds Spring Figures show lead : zinc ratio of stream sediment, in parts per million Frgur® 1.-Geochemical and geologic map of the Pyrite Creek area, southern part of the Long Pond quadrangle Somerset County, Maine. Geology modified from Boucot (1961). Base from U.S. Geological Survey Long Pond 1 :62,500 quadrangle, 1922. CANNEY AND POST foot of the falls. On strike and about 150 feet to the southeast, a quartz vein bordered by silicified and pyritized rock is exposed on a steep hillside. Presum- ably this is the same vein. The vein in the gorge at the foot of the falls appeared to be mostly barren quartz, but when broken open, it was found to contain small pockets of galena, pyrite, and very sparse chalco- pyrite. The country rock adjacent to the vein is highly silicified and pyritized. This vein apparently does not extend far to the northwest, for a shallow, angled diamond drill hole collared near the edge of the stream at the top of the falls did not intersect the vein at its projected position. The galena from the vein is rich in silver and bis- muth. One sample containing selected pieces of galena-bearing quartz assayed 1.6 percent lead and 5.4 oz of silver per ton; no gold was detected. A semi- quantitative spectrographic analysis of a sample of relatively pure galena showed the bismuth and silver contents to be about 2 percent and 0.7 percent respec- tively. Approximately 3,300 feet north-northeast of the waterfall zone an outcrop of silicified quartz monzonite is cut by narrow stringers of galena-bearing quartz. A little more than a mile north of the waterfall, a highly pyritic quartz vein is present on the southwest side of U.S. Route 201 (fig. 1). It trends N. 37° W., and is surrounded by iron-stained and silicified quartz monzonite. No galena was seen, but its presence has been reported. The quartz monzonite locally contains stringers and clots of specular hematite where the rock is extensively silicified and altered. Although the hematite is not known to be related to the sulfide minerals in the quartz veins, it does characteristically accompany ex- treme alteration of the quartz monzonite in this area. The geochemical data were obtained by analyzing the fine-grained fraction (minus-250 micron) of sam- ples of stream sediments collected from the active chan- nels. Field methods of chemical analysis described by Ward and others (1963) were used. The most striking feature of the geochemical pattern is the exceedingly high contents of lead and zinc in Pyrite Creek from a point just north of the Parlin Pond Township line to the junction of Pyrite Creek with the western branch of the tributary to Bean Brook. Although the heavy-metal content of the stream sediment is anomalous along the entire length of Pyrite Creek (lead background in this part of Maine is about 10-30 ppm and zinc background about 50-125 ppm), a marked decrease in the anomalous values occurs at the confluence of Pyrite Creek with D63 the western branch of the tributary. This is due to the much greater load of fine sediment carried by the western branch. The stream sediments of Pyrite Creek also have ex- tremely high contents of manganese, with numerous samples containing between 1 and 15 percent man- ganese. Visible manganese in the form of black coat- ings on boulders in stream courses, and in many places as discrete nodules, is not uncommon in streams in Maine, especially in streams draining swampy areas. Pyrite Creek does drain a northeasterly trending swamp; nevertheless, the manganese content of the Pyrite Creek sediments appears to be unusually high when compared with the manganese content of sedi- ments from other streams draining similar environ- ments, and therefore these high manganese values are in themselves suggestive of a mineralized area. Interpretation of the data of geochemical drainage surveys in Maine is complicated by the scavenging action of manganese coatings and nodules. Zinc, co- balt, molybdenum, and barium are among the elements we know to be concentrated by this material. Accord- ingly, the variability in the zinc pattern along Pyrite Creek is controlled partially by the varying man- ganese content of the stream sediment. Nevertheless, the ratio of zinc to manganese is considerably above average. This suggests that the zinc is derived from a mineral deposit, rather than being merely the prod- uct of manganese oxide scavening. The significance of the lead anomaly is also increased by the fact that much of our data on the lead and manganese content of stream sediments suggest that lead is not scavenged by manganese to any significant extent. Appraisal of the possible economic significance of this anomaly is difficult. The known exposures of mineralized rock appear to be inadequate to produce this very intense anomaly. The galena-bearing vein exposed in the gorge at the foot of the waterfall ap- pears to have little effect on the anomaly, for the highest lead content (2,500 ppm) was measured about 300 feet upstream from the vein. It is conceivable that a swarm of similar weakly mineralized zones is concealed beneath the extensive glacial cover and swamp upstream and that sufficient lead and zinc is being leached by circulating ground water to account for this anomaly. On the other hand, the possible presence of larger and richer zones cannot be ruled out on the basis of present knowledge. It is our opin- ion that the intensity of this anomaly justifies a more detailed exploration program of the upper Pyrite Creek area by geological, geophysical, and geochemi- cal surveys. GEOCHEMISTRY D64 REFERENCES Albee, A. L., 1961, Boundary Mountain anticlinorium, west- central Maine and northern New Hampshire: Art. 168 in U.S. Geol. Survey Prof. Paper 424-C, p. C51-C54. Boucot, A. J., 1961, Stratigraphy of the Moose River syn- clinorium, Maine: U.S. Geol. Survey Bull. 1111-E. # Post, E. V. and Hite, J. B., 1963, Heavy metals in stream sediment, west-central Maine: U.S. Geol. Survey Min. Inv. Field Studies Map MF-278. Ward, F. N., Lakin, H. W., Canney, F. C., and others, 1963, Analytical methods used in geochemical exploration by the U.S. Geological Survey: U.S. Geol. Survey Bull. 1152. GEOLOGICAL SURVEY RESEARCH 1964 RADIOACTIVITY- AND DENSITY-MEASURING DEVICES FOR OCEANOGRAPHIC STUDIES By CARL M. BUNKER, Denver, Colo. Abstract.-Field tests with modified gamma-ray logging equipment indicate that it is feasible to make continuous pro- files of gamma radioactivity and relative bulk density on lake or ocean bottoms. Lack of adequate geologic control in the test area prevented correlation of the peaks and valleys in the profiles with specific changes in the lithology. On the basis of these experiments an underwater vehicle and sensing sys- tem were designed to make simultaneous measurements of radioactivity and relative bulk density for routine mapping programs. Preliminary studies and equipment tests to deter- mine the feasibility of measuring the gamma radio- activity and relative bulk density of recent lake-bottom sediments were made in Lake Superior (fig. 1) and in Burt Lake, Cheboygan County, Mich., during the summers of 1961 and 1962, respectively. Measure- ments of these types have been proposed for use in the U.S. Geological Survey oceanographic program and are expected to provide a method of mapping the upper few inches of the ocean bottom in conjunction with geologic and mineralogic studies. When carried on together with an adequate bottom- sampling program to provide geologic control the technique makes possible inferences about the physical properties of the lithologic units exposed on the sea floor. Such inferences are of potential value in harbor construction and in related engineering problems. In addition, the submarine radioactivity measurements may permit (1) outlining underwater ore deposits when such deposits are associated with radioactive materials as, for example, the Florida phosphates, and (2) plotting the course of low-level radioactive wastes along the ocean bottom after waste-bearing waters have left the mouths of rivers into which they have been dumped. The efficiency of the detection system is low because of the inherent insensitivity of the Geiger-Mueller Clay rse B Mnd Rock SUPERIOR WISCONSIN 0 5 10 MILES 1.-Index map showing location of traverses made in western Lake Superior. tubes, and the absorption of the radiation by the de- tector housing and the water layer between the sedi- ments and the housing. The low counting rate which results from the low efficiency and low intensity radia- tion in the sediments precludes the possibility of ob- taining gamma-ray spectral data from a small area while the detector is being towed across the sediments. Thus, only a gross measurement of the radiation in- tensity is obtained, from which isotope identification is impossible. The gross radiation intensity may be from natural radioisotopes of uranium, thorium, and potassium, from nuclear-explosion-produced fission products in fallout, or from a combination thereof. Semiquantitative data expressed in terms of equiva- lent uranium or milliroentgens per hour can be ob- tained from the gross radioactivity measurements. Disequilibrium of the natural radioisotopes and the presence of fission products may lead to erroneous conclusions concerning the radioisotope content of the sediment. A bottom-sampling program in areas of anomalously intense radioactivity in conjunction with the gross radioactivity measurements will permit iso- tope identification to determine the source of the radioactivity. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D65-D69 D65 D66 The author gratefully acknowledges the cooperation of the U.S. Coast Guard and of Commander C. G. Porter and the crew of the USCG cutter Woodrush without which the Lake Superior measurements could not have been made. M. D. Shutler aided with the Lake Superior and Burt Lake studies; T. H. Cleveland - also assisted at Burt Lake. EQUIPMENT AND PROCEDURE The equipment used is similar to that used by the U.S. Geological Survey for borehole logging in con- junction with geologic studies and uranium exploration (Vaughn and others, 1959; Bell and others, 1961). It consists of a probe containing a gamma-ray detector and an impedance matching circuit; a reel unit con- taining several hundred feet of coaxial cable for tow- ing the probe, for transmitting power to the detection equipment, and for transmitting signals from the de- tectors to the monitoring equipment; a high-voltage power supply; a pulse amplifier which sometimes in- cludes a pulse gating circuit; a ratemeter, and a re- corder. The system operates on 115-volt a-c power. Measurements of gamma radioactivity in Lake Superior were made with a single Geiger-Mueller tube or with a scintillation detector consisting of a sodium iodide crystal coupled to a photomultiplier tube. The monitoring circuitry is adjusted to accept gamma-ray energies greater than about 100 thousand electron volts to measure the gross radioactivity; no attempt was made to measure individual gamma-ray energies or to identify the gamma-emitting radioiso- topes. Measurements of relative bulk density were made with the above detectors separated by 0.6 foot of lead from a 1.0 millicurie source of cobalt-60. The radia- tion from the source penetrates the sediment, where it is scattered or absorbed. The amount reaching the detector depends on the bulk density of the material through which the photons pass. An increase in den- sity results in a decrease in the path length of the photons, thereby causing less radioactivity to be measured at the detector. The measurement of this radioactivity therefore is a measure of the bulk density of material, including the water, adjacent to the space between the source and the detector. The gamma radioactivity and relative bulk-density measurements were made independently. However, the measurements can be made simultaneously if the detector for measuring the radioactivity in the sedi- ments is spaced at a sufficient distance from the radio- active source and shielded to prevent measuring the radiation from the radioactive source used for the density measurement. GEOPHYSICS Two traverse lines in Lake Superior near Duluth, Minn., were chosen on the basis of available, though sparse, data on the type of lake-bottom sediments indi- cated by hydrographic charts. Measurements were made from the USCG cutter Woodrush. The moni- toring equipment was installed in the chart room, with direct communication lines to the bridge and to the winch operator on the quarterdeck. Power and signal cables also connected the winch and underwater equip- ment with the electronics and data-recording systems. The detector was towed at various speeds up to 10 miles per hour; the detector could not be held on bot- tom above this speed in water depths ranging from 40 to 150 feet. The ship's location along the traverse was determined at the instrument operator's request and at prearranged locations; the location was then indicated on the recording chart to provide a means of comparing several types of data at a given location. A traverse along the predetermined line was required for each type of data required and for each instrumen- tation change. The measurements at Burt Lake were made simi- larly, except that the traverse lines were located be- tween the shore and points in the lake. The monitor- ing equipment was located in a laboratory vehicle parked at the lake shore. Flag buoys were set about 900 feet from shore to establish the in-lake position from which repeated traverses were made. The sedi- ments ranged from mud in the offshore locations to sand and gravel at the shore. RESULTS AND PROBLEMS The lack of geologic data with which the geophysical data might have been related confined the field studies to problems of instrumentation. Records from re- peated measurements along the same traverse lines often showed similar configurations (fig. 2), suggesting that changes in the records were related to changes in the characteristics of the bottom sediment. There- fore, the field studies were directed toward increasing the sensitivity of the sensing systems to indicate these changes. The radiation intensity was greater in the areas indicated as sandy on the hydrographic charts than in the areas of clay. The records showing rela- tive bulk density indicated changes along the traverses, but these could not be related to sediment type. The sensitivity of the single Geiger-Mueller tube was generally insufficient for measuring gamma radioactivity, although some records obtained with this equipment could be related to others obtained with the more sensitive scintillation equipment. Use of the scintillation equipment resulted in records show- BUNKER Rate increases Scintillation detector COUNTING RATE Geiger-Mueller detector DISTANCE FicurE 2.-Portion of gamma-ray logs of lake bottom of Lake Superior, near Duluth, Minn. Logs reproduced from curvi- li/near recording chart. Horizontal distance represents about }s mile. ing relatively large changes in counting rate. On the basis of sensitivity, the scintillation equipment gave the best results. However, experience with this equip- ment when used in other applications has shown that it is affected by temperature and voltage changes. Instability of this type would preclude its use for obtaining semiquantitative data. Therefore, a probe containing a bundle of seven Geiger- Mueller tubes was partially tested at Burt Lake to increase the sensitivity and to utilize the relatively high stability of the Geiger-Mueller detection system. Although the system requires further modifications, the sensitivity was im- proved with the tube bundle. EQUIPMENT FOR FUTURE STUDIES On the basis of field studies and the problems re- lated thereto, an underwater vehicle and instrument package (fig. 3) was designed, and requirements for the monitoring system (fig. 4) were decided upon. The instrument package provides for two detection systems, which allows simultaneous measurements of D67 gamma radioactivity and relative bulk density, thereby avoiding repeated measurements on each traverse line. The instrument package is transported on a skid designed to hold the package on the bottom and to minimize the possibility of its snagging in weeds and rocks. Diving planes are included at the front of the unit to counteract the upward pull of the cable. The weight of the lead shielding in the package should be sufficient to keep the back of the vehicle against the sediment. A vertical plane on top of the vehicle is provided to prevent fishtailing. Based on previous experience, the detection package will easily withstand the pressure of 1,500 feet of water. Two identical monitoring and recording systems are required for simultaneous measurements of natural radioactivity and density. Detailed requirements pro- vide for a wide range of readouts and time constants. Discriminator circuits are included to provide for scintillation detectors, if required by special conditions. The distance between the radiation detector and the radiation source (the lake or ocean bottom) must remain virtually constant because of the effects of source-to-detector geometry and radiation absorption by water. The half-thickness value of water is about 3.3 inches for the average gamma-ray energy (about 0.7 million electron volts) from uranium and its daugh- ter products. This means that the radiation incident on the detector is reduced by about one half for each 3.3 inches of water between the detector and the radia- tion source. The value is related directly to gamma- ray energy. The effect of distance is greater than the effect of water because the radiation varies as a func- tion of the square of the distance between the detector and the radiation source. Small changes in distance can cause large changes in the amount of radiation incident on the detector. Ideally, the detection system should be in constant contact with the sediment to eliminate the effects of distance and water absorption, and to keep the detector in the area of maximum radiation intensity. However, some finite distance is required between the sediments and the waterproof housing encasing the detector to provide protection against abrasion. Although maintaining the detector in constant contact with the sediments is extremely difficult in actual operation, the distance between the detector and the sediment can be kept to about 1 inch as the detector is dragged along the lake or ocean bottom. A problem greater than reducing the sediment-to- detector spacing to a minimum is maintaining a con- stant distance while the measurements are being made at the relatively high speeds required to conduct a mapping program economically. During the Lake D68 Waterproofing 3-coaxial cable Pressure switch Bottom indicator and battery pack Impedance matching circuit GEOPHYSICS Gamma-ray source CUTAWAY VIEW OF INSTRUMENT PACKAGE Stress line Skid runner SIDE VIEW OF VEHICLE O F O O Skid runner -Cross brace Diving plane £ S- s R 12 Stress" ~ __ 11 a I line s 1 & Instrument package n "-- o 0 o 3 TOP VIEW OF VEHICLE Cross brace REAR VIEW OF VEHICLE Instrumen package Fraur® 3.-Diagrammatic sketch showing preliminary design of vehicle for measuring radioactivity and density of underwater sediments. - Dimensions are in inches. Superior studies the winch operator could generally detect changes in the vibration or tension on the towline when the probe lifted from the lake bottom. The ship's speed was then reduced until the probe re- mained on bottom. A more reliable system to indicate automatically when the probe is in contact with the sediments is required for routine measurements to aid equipment operations and to provide a method for determining when the data are valid. A bottom indi- cator was designed to send a signal to a side-marker pen on the recording equipment to show when the vehicle is in contact with the lake or ocean bottom. The bottom indicator consists of a strip of spring steel which is depressed against a contact switch in the probe shell to close a battery-powered electrical cir- cuit when the probe is on bottom. BUNKER D69 RADIOACTIVITY MEASUREMENT DENSITY MEASUREMENT FraurE® 4.-Diagrammatic sketch of arrangement of instruments for measuring radioactivity and density of under- water sediments. REFERENCES Bell, K. G., Rhoden, V. C., McDonald, R. L., and Bunker, C. M., - Vaughn, W. W., Rhoden, V. C., Wilson, E. E., and Faul, Henry, 1961, Utilization of gamma-ray logs by the U.S. Geological 1959, Scintillation counters for geologic use: U.S. Geol. Survey, 1949-1953: U.S. Geol. Survey open-file report, Survey Bull. 1052-F, p. 213-240. 89 p. 5, GEOLOGICAL SURVEY RESEARCH 1964 AEROMAGNETIC INTERPRETATION OF THE GLOBE-MIAMI COPPER DISTRICT, GILA AND PINAL COUNTIES, ARIZONA By ANNA JESPERSEN, Silver Spring, Md. Abstract.-No correlation appears to exist between the mag- netic highs and the known ore deposits in the Globe-Miami copper district, but the ore-bearing structures have a north- easterly trend that is reflected in the magnetic pattern. The large positive anomalies in the southern part of the mapped area are attributed to Madera Diorite. Irregular clusters of smaller anomalies are associated with diabase dikes. The major part of the Globe 15-minute quadrangle, in Gila and Pinal Counties, southeast-central Arizona (fig. 1), covers a copper-mineralized belt that is about 6 miles wide. This belt extends east-northeastward across the middle part of the quadrangle (Peterson, 1962, fig. 14, p. 142) and includes the Globe-Miami copper-mining district. The terrain is rugged; alti- tudes range from 7,850 feet on Pinal Peak, in the southeastern part of the quadrangle, to 3,050 feet where Pinal Creek crosses the north boundary of the quadrangle.. Prospecting in this area, which began as early as 1874, led to the discovery and development of the Globe-Miami, Castle Dome, and Copper Cities copper deposits. As about 60 percent of the mineral- ized belt is buried under volcanic sheets and surficial deposits, it was hoped that an airborne magnetic sur- vey might delineate additional ground favorable for further copper prospecting. Such a survey was made in 1946. Total-intensity aeromagnetic measurements were made with a continuously recording AN/ASQ-3A air- borne magnetometer installed in a twin-engine aircraft. The distance from plane to ground was measured with a continuously recording radar altimeter. Trav- erses were flown north-south at quarter-mile intervals and about 1,000 feet above the ground. Because of the rugged terrain this altitude could not be continu- ously maintained; it ranged between 500 and 2,000 feet. Alternate flight lines were omitted in areas of broad magnetic features. A preliminary version of the contoured map (Dempsey and Hill, 1952) was released in 1952. GENERAL GEOLOGY The generalized geologic map (fig. 2) is adapted from Peterson (1962) and Ransome (1904). The oldest rocks are the lower Precambrian Pinal Schist and dioritic and granitic intrusions into this schist. Overlying the lower Precambrian rocks are the Apache Group of late Precambrian age, and Paleozoic sedi- mentary rocks. The younger rocks comprise intrusive and volcanic rocks, conglomerate, and surficial deposits. Intrusive rocks underlie about a fourth of the mapped area. The region is strongly faulted along northeasterly and northwesterly trends. The earliest faulting pre- ceded the intrusions of diabase, and the latest was later than the accumulation of Gila Conglomerate. The Globe Hills block, the Globe Valley graben, the Inspiration block, and the Castle Dome horst are all bounded by mapped or inferred fault zones. The Globe Hills block occupies the northeastern part of the map area, the Globe Valley graben coincides in general with the Pinal Creek drainage, and the Castle Dome horst forms Porphyry Mountain. The ore deposits of the Miami-Inspiration, Castle Dome (now mined out), and Copper Cities mines are large tabular generally horizontal zones of dissemi- nated copper sulfides. The host rocks for the Miami- Inspiration deposit are Pinal Schist and granite porphyry and for the Castle Dome and Copper Cities deposits are quartz monzonite and granite porphyry intruded by thin sills of thoroughly brecciated diabase. The copper mineralization of the district occurred U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D70-D75 D7O JESPERSEN after the intrusions of Schultze Granite and granite porphyry and before the eruption of the dacite (Peter- son, 1962, p. 67, 82, 89; Peterson and others, 1951, p. 103; Ransonie, 1919; p. 169). The principal ore minerals are pyrite, chalcopyrite, chalcocite, malachite, and chrysocolla. Although the original iron minerals of the host rocks were com- pletely destroyed by hydrothermal alteration during mineralization, the iron content of the mineralized rock generally was greatly increased owing to introduction of pyrite and chalcopyrite. During oxidation and enrichment most of these minerals were altered to limonite (Peterson, written communication, March 6, 1964), which is nonmagnetic. The deposits at Globe are vein deposits. The veins were formed by replacement of breccia and wallrock along faults and fissures that cut upper Precambrian and Paleozoic sedimentary rocks and bodies of diabase intruded into them (Peterson, 1962, p. 97). The ore is localized in west-pitching shoots and irregular masses, as replacement of the different types of wall- rock. No magnetic minerals are present. The wall- 113° 112° 111° 110° 109° Flagstaff o nos, GP b 402 F % | TTucson =_ # 20 ho °C Nogales 50 0 50 100 MILES FrGur® 1.-Index map of Arizona, showing location of the Globe 15-minute quadrangle (cross hatched) and other areas covered by published aeromagnetic maps (in the Geophysical Investiga- tions, GP, series) of the U.S. Geological Survey. D71 rocks are strongly altered adjacent to the veins, but the altered zones are generally only a few feet wide, rarely more than 10 feet. The veins commonly contain abundant specular hematite, earthy hematite, and limonite. CORRELATION OF MAGNETIC DATA WITH GEOLOGY AND MINERAL DEPOSITS The aeromagnetic map of the area (fig. 3) shows a general east-northeast magnetic trend, which correlates with the trend of the geologic structure and with the trend of the ore zone (see Peterson, 1962, fig. 14, p. 142). The overall magnetic pattern comprises north- ern and southern anomalous areas of steep gradient, divided by a broad middle east-west band of gentle gradients. Although many of the highs in the north- ern half of the area coincide roughly with topographic highs, the magnetic expression is believed to be due mainly to the character of the rock itself rather than to the relative nearness of the magnetometer to the mountain peaks. Magnetic minerals seem to be rare or absent from the ore deposits in the Globe quadrangle, but the ore- bearing structures have a persistent northeasterly trend throughout the region, and that trend is reflected in the magnetic pattern. No correlation appears to exist between the magnetic highs and the known ore de- posits. In fact, the principal mines are associated not with the maxima of the highs but with their flanks. In general, the magnetic anomalies appear to be asso- ciated with rock masses of varying magnetic properties rather than with known ore deposits. The diabase sills show a characteristic pattern of small magnetic highs and lows, particularly in the northeastern and the northwestern parts of the area (figs. 2 and 3). According to Peterson (1962, p. 29), the diabase varies considerably in mineral composition even within relatively small outcrops. Some of the diabase contains as much as 10 percent olivine or its alteration products, and magnetite is abundant in all the diabase. The variation in magnetite content and in thickness of the sills, the irregularity in distribu- tion, and the intense faulting and fracturing of the diabase contribute to the lack of uniformity in the magnetic pattern associated with the exposed and postulated buried bodies of this rock. Some of the lows in the northern part of the mapped area may be due to reverse remanent magnetization of the dacite sheets. The two kidney-shaped magnetic lows, the one on the southwest and the other on the southeast flank of Webster Mountain, appear to be typical expressions of reverse magnetization. D72 GEOPHYSICS 111" R. 14 E. 110°52'30" 8. 15 E. R. 1514E. 110°45" 33°30' fos $3°22'30" 33*156' '/4%/ .> ‘ ¥ \\3% Y 4 IP f Z. ////////5 Nall ._ )Tst . B.13 E. ; ‘Q -s‘. ost dacite sedimentary rocks and flows Schultze Granite TERTIARY TERTIARY (?) AND QUATERNARY : EXPLANATION CRETACEOUS OR TERTIARY Apache Group and younger sedimentary rocks | PRECAMBRIAN AND PALEOZOIC # Ruin Granite P # Madera Diorite Contact - Fault Dashed where approximate- ly located; dotted where concealed PRECAMBRIAN Base from U.S. Geological Survey topographic quad- rangles: Globe 1945, Inspiration 1945, Pinal Ranch 1948, and Globe SE advance sheet } 0 1 1 2 I 3 MILES 1 Ki FiaurE 2.-Generalized geologic map of the Globe quadrangle, Arizona. Geology generalized from Peterson (1962, 1963) and Ransome (1904) JESPERSEN D73 R. 1514E. 110°45" i* R. 14 E. 110°52' 30" 1 33°30 33°2230"|- i 3400-1 I I ; # 1 8. ‘ - EXPLANATION EAC Flight path 0 Showing location and spacing of data NOTE Aeromagnetic data are obtained and compiled along Magnetic contours showing total intensity a continuous line, whereas ground magnetic surveys T. magnetic field of the earth in gammas are made at separate points. Errors within the 3 relative to arbit dat normal limits of any magnetic measurement may 5. Aroitrary datum cause slight discrepancies between flight lines in an Hachured to mdwatev closed areas of lower aeromagnetic map, which would be more obvious than magnetic intensity similar discrepancies between points in a ground magnetic map. For this reason as much care should 3654 be exercised in evaluating magnetic features that 3 Uk appear as elongations along a single aeromagnetic .Meas|.1red wafclmum or fnmlmum trayerse as in interpreting an anomaly indicated by Asie! - mtensity within (lzlosed high or low a single ground station § £126. R. 14 E. R. 15 £. R.16 E. Base from U.S. Geological ‘Sur_vey topographic quad- Aeromagnetic survey by W. J. Dempsey rangles: Globe 1945, Inspiration 1945, Pinal Ranch 1 o 1 2 3 MILES and M. E. Hill, 1946. Flight elevation 1948, and Globe SE advance sheet bas ite 3 1 1 1 about 1000 feet above ground CONTOUR INTERVAL 40 AND 200 GAMMAS FraurE 3.-Aeromagnetic map of the Globe quadrangle, Arizona. D74 A large magnetically flat pattern is associated with the Globe Valley graben. This flat pattern is due, at least in part, to the fact that here the magnetic rocks are not only at a relatively greater distance from the magnetometer, but are, in addition, buried by younger deposits of nonmagnetic material. The various granitic rocks generalized on the map as quartz monzonite, the Ruin Granite, and the Schultze Granite are all associated with a distinctive magnetic pattern of low gradient. The pattern in places is somewhat complicated by the influence of buried diabase sills, as, for example, a 200-gamma gradient that crosses longitude 110°52'30" W. in a northeasterly direction a mile south of the common corner of Ts. 1 and 2 N., Rs. 14 and 15 E. (see Ran- some, 1904, structure section B-B). The rather large anomaly just west of longitude 110°52'30" W. in the southern half of the mapped area and the one 4 miles farther west are attributed to the mapped and concealed Madera Diorite. The concealed diorite is interpreted to lie a few hundred to 1,000 feet below the surface. The magnetic lows northeast of these highs indicate a vertical or steep northern face on the batholithic body of diorite (see Vacquier and others, 1951). The large elongated low at the south- east corner of the mapped area is believed to be due to a steep north face on the body of Madera Diorite that crops out there and to the south. If the aero- magnetic survey had been extended farther southward it would doubtless have shown a magnetic high to the south of this low, similar to the two highs farther west. The sharp linear gradient to the north of this low suggests a fault boundary at the south edge of the (Globe Valley graben (see also Peterson, 1962, fig. 14, p. 142). CONCLUSIONS AND RECOMMENDATIONS This survey was made to determine the magnetic expression associated with ore-deposit host rocks and structures as a basis for interpreting similar expression over buried rock masses and thus possibly delineating favorable ground for further prospecting. In an area that has been prospected and mined for nearly a cen- tury, undiscovered ore deposits are likely to be few or nonexistent. It must also be emphasized that aero- magnetic mapping is a reconnaissance method and is not expected to pinpoint the spots best suited for drilling. Attention is called, however, to a few locali- ties of possible buried rock masses and structures that GEOPHYSICS are similar magnetically and in their geologic rela- tions to exposed host rocks. Contacts of diabase with Pinal Schist.-In past min- ing in the region, ore has been found at the contact of diabase with Pinal Schist and favorable granitic rocks. Several such contacts are shown on detailed geologic maps of various parts of the quadrangle (Peterson and others, 1951, p. 126; Peterson, 1962, p. 97). Other similar but buried contacts are sug- gested by comparable magnetic patterns; for example, the small lows that form an are around the large anomaly in the southwestern half of T. 1 S., R. 14 E. The past history of prospecting in these areas, as in all other areas pointed out for possible future pros- pecting, should be kept in mind in any plans for further search for ore deposits here. The area northeast of Willow Spring Gulch (fig. 2) marked by an elongated anomaly, has already been thoroughly prospected. However, the area southeast of that gulch, that is, the east flank of Camelback Mountain, may warrant further prospecting. This area is delineated by a paired magnetic high and low. Dacite-covered anomalous areas.-Ransome (1919, p. 169-173) has shown that the hypogene copper de- posits near Miami had been exposed and a chalcocite ore body produced by supergene enrichment before the dacite covered the area. Dacite-covered areas that coincide with magnetic lows could conceivably con- ceal oxidized and enriched deposits. Only a few faults have been mapped in the large Tertiary dacite flow south of Webster Mountain. Peterson (1962, p. 141) has called attention to an occurrence of exotic copper in a fracture zone in the dacite body on the Empress claim, 2.2 miles east- northeast from Porphyry Mountain; a few shallow pits and a 40-foot shaft explored the fracture zone. From the magnetic pattern associated with this dacite flow it can be postulated that the diabase, Pinal Schist, and other concealed rocks are highly fractured. If this is the case, this area appears to have mineral possibilities; yet it is the least prospected part of the entire mineral belt. The magnetic pattern, the small fault and the small Tertiary-Quaternary and basalt flows mapped by Peterson (1962, pl. 1), and the drain- age across the dacite-covered area all suggest that if prospecting is undertaken it should cross the area in a southeast-to-northwest direction close to and parallel to the fault, the basalt outcrops, and the streams, thus coinciding with the flanks of the anomalies. D75 JESPERSEN REFERENCES Dempsey, W. J., and Hill, M. E., 1952, Preliminary aeromag- netic map of Globe quadrangle, Arizona: U.S. Geol. Survey open -file report. Peterson, N. P., 1962, Geology and ore deposits of the Globe- Miami district, Arizona: U.S. Geol. Survey Prof. Paper 342, 151 p. 1963, Geology of the Pinal Ranch quadrangle, Arizona : U.S. Geol. Survey Bull. 1141-H, p. H1-H18. 742-652 0O-64--6 Peterson, N. P., Gilbert, C. M., and Quick, G. L., 1951, Geology and ore deposits of the Castle Dome area, Gila County, Arizona: U.S. Geol. Survey Bull. 971, 134 p. Ransome, F. L., 1904, Description of the Globe quadrangle, Arizona: U.S. Geol. Survey Geol. Folio 111, 17 p. 1919, The copper deposits of Ray and Miami, Arizona : U.S. Geol. Survey Prof. Paper 115, 192 p. Vacquier, Victor, Steenland, N. C., Henderson, R. G., and Zietz, Isidore, 1951, Interpretation of aeromagnetic maps: Geol. Soc. America Mem. 47, 151 p. R GEOLOGICAL SURVEY RESEARCH 1964 EPIGENETIC URANIUM DEPOSITS IN SANDSTONE By WARREN 1. FINCH, Paducah, Ky. Work done in part in cooperation with the U.S. Atomic Energy Commission Abstract.-Nearly all of the approximately 4,600 sandstone uranium deposits in the United States are in continental sediments that accumulated in shallow, poorly drained fore- land or postorogenic basins. Data from these deposits suggest that the uranium was precipitated from alkaline connate-water solutions during and after diagenesis under reducing conditions at normal rock temperatures and pressures. Some 4,600 epigenetic uranium deposits in sandstone constitute the Nation's chief source and reserve of uranium ore. About 95 percent of the deposits lie in two belts: a major belt extending northeasterly from Arizona and New Mexico through the Colorado Plateau and Wyoming into South Dakota, and a minor belt extending easterly through New Mexico into northern Texas and Oklahoma (fig. 1). This principal uranium region or province also contains other kinds of large uranium ore deposits (Butler and Schnabel, 1956; Klepper and Wyant, 1956) and has been related to tectonic elements in Precambrian rocks of the Cor- dilleran foreland by Osterwald (1956). Most of the remaining 5 percent of uranium deposits in sandstone are in California and Nevada, southeast Texas, and Pennsylvania. Most deposits have been described as peneconcordant (Finch, 1959) and the remainder as vein deposits. This paper summarizes the major con- clusions from a longer report that describes the geology of the uranium deposits in sandstone formations in the conterminous United States. Nearly all the sandstone in which the deposits lie is continental and formed in shallow, poorly drained basins either within foreland areas or between fault- block uplifts. Some of the sandstone is marine and formed in epicontinental seas along margins of the craton. None of the deposits are in geosynelinal sand- stone. Most of the Paleozoic host sandstone in the Western States formed on the Ouachita foreland; and in the Eastern States, on the Appalachian foreland (fig. 1). Most Mesozoic host sandstones in the West formed on the Cordilleran foreland; in the East, in rift valleys of New Jersey and Connecticut. Tertiary host sand- stones in the principal uranium region and in Cali- fornia and Nevada formed in basins between fault- block uplifts; in southeast Texas, they formed on the coastal foreland. Exceptions to these generalizations include lower Mesozoic host sandstones that formed east of the Cordilleran foreland, mainly along the late Paleozoic Quachita foreland, and Paleozoic sandstones that contain vein rather than peneconcordant deposits and formed in areas west of the Quachita foreland. Water within the basins of sandstone deposition was mostly fresh, but associated coal and saline rocks in many basins suggest that drainage was poor and in- ternal, at least locally, especially in the last stages of deposition. Thus, concentrations of metals, salts, and humic acids in the water may have increased during deposition, with subsequent entrapment of this water in the rocks at the close of each sedimentary cycle. The host sandstones are mainly stream-deposited lenses. They are chiefly quartzose, arkosic, or tuffa- ceous; most of the quartzose sandstones are closely associated with tuffaceous rocks. Carbonized plant remains are common in ore-bearing beds, and some sandstones are impregnated with epigenetic asphaltlike material that was probably derived from humic matter dissolved in connate water. Deformation since the accumulation of the host sandstones has been slight to moderate and seems, in most areas, to have occurred after most of the uranium mineralization. Igneous activity is not evident in some areas of sandstone uranium deposits. In other areas, igneous activity bears little direct relation to the dis- tribution and nature of deposits, except for two iso- U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D76-D78 " D76 D77 FINCH *(L961 'uonsotunwuuo09 Uoj}IIM) 19%[¥AM 'M pus p[eMAIO}SQ 19je Sourepunog 1930 {(T $4 '1961) pleaiojso 4repunoq pusjoio; 'Soje]lg pojluq of} UI start pajejor put 'ouogspurs UI sqsodop wntu®im onouastdo jo «HOODIA ¢ y 2 @ fp antes 4904 soy 210z09]ed S3 1IW OO€ 0 V »9041 jsou o10zosap U 4901 soy Aeta | X sLIsod30 WNINYHN NOILYNYTId4X3 D78 lated districts where vein deposits are inferred to have formed from magmatic differentiation or volcanic ema- nations (Neuerburg and Granger, 1960 ; Kern, 1959). The ore bodies are chiefly tabular masses, but roll- like pods, concretionary masses, and mineralized fossil logs are common. In peneconcordant deposits the ore bodies virtually follow the bedding, but in vein de- posits the ore bodies mostly follow faults and shear zones that cut sharply across bedding. The minerali- zation was not intense, and little or no gangue mineral matter was introduced. Ore solutions were nearly in equilibrium with the host rocks, which are altered but slightly. Bleaching is the principal alteration, but it can hardly be distinguished from diagenetic bleaching. Primary minerals of the sandstone ores consist of low-valent uranium and vanadium oxides and silicates, and of common sulfide minerals of iron, copper, lead, and zinc. Uraninite and coffinite are the chief primary uranium minerals. Uraninite occurs chiefly as grains, either dense and structureless or with a microbotry- oidal structure. Coffinite is mostly very fine grained and intergrown with other minerals. Some vanadium and uranium substitutes for other elements in certain sedimentary minerals. The chief ore-mineral textures include erystals partially filling open spaces, and re- placements of fossil plant matter, sand grains, cement- ing materials, and earlier minerals. Paragenetic se- quences of the ore minerals consist of numerous over- lapping stages that cannot be clearly separated, particularly the early stages from the sequence of dia- genetic minerals. The primary ores commonly oxidize to produce a wide variety of secondary minerals, the most common of which are carnotite and tyuyamunite. Inferences regarding genesis must account for sources of the metals, for the transporting media, and for mineralization controls indigenous to the host rocks. Although a possible telethermal origin is by no means eliminated, mineralization by connate water is here regarded as more likely for most of the sand- stone uranium deposits, particularly for those that are peneconcordant, and the following conclusions seem to best fit the field and laboratory observations. Uranium and associated metals are believed to have been derived from the weathering of granite and re- lated rocks, from the devitrification of volcanic glass during sandstone deposition and during diagenesis, and from the alteration of heavy minerals. It is inferred that the metals were transported in moderately concentrated metallic and alkaline bicar- bonate solutions (Hostetler and Garrels, 1962), of con- nate and (or) ground water at temperatures and pres- sures about the same as those of the enclosing rocks. Pa ECONOMIC GEOLOGY Mineralization was protracted, and it began early dur- ing diagenesis. During compaction of the sediments, especially of the tuffaceous muds, the connate solutions moved into the permeable sandstone beds, particularly those beneath thick beds of volcanic material. Fur- ther movement was laterally along the beds. The ores were modified by changes in movement of the solution due to (1) ground-water recharge, (2) reactivation in response to tectonic and igneous activity, and (3) Recent erosion and weathering. Mineralization in most areas probably ceased when the mineral-bearing waters were flushed out and replaced by normal ground water, most likely at the time of major struc- tural deformation. Precipitation of the low-valent ore minerals was due chiefly to reduction by carbonized plant remains, asphaltlike material, hydrogen sulfide gas from decay- ing plant matter, and (or) diagenetic iron sulfide minerals. Colloidal deposition predominated, perhaps brought about by anerobic bacteria, but crystallization, ion-exchange, adsorption, and replacement were also prevalent. Concretionary growth of ore through diffu- sion seems to have been common. Deposits were local- ized mainly by sedimentary structures and also partly by deformational structures. REFERENCES Butler, A. P., Jr., and Schnabel, R. W., 1956, Distribution and general features of uranium occurrences in the United States, in Page, L. R., Stocking, H. E., and Smith, H. B. compilers, Contributions to the geology of uranium and thorium . ..: U.S. Geol. Survey Prof. Paper 800, p. 27-40. Finch, W. I., 1959, Peneconcordant uranium deposit-a pro- posed term: Econ. Geology, v. 54, no. 5, p. 944-946. Hostetler, P. B., and Garrels, R. M., 1962, Transportation and precipitation of uranium and vanadium at low tempera- tures, with special reference to sandstone-type uranium deposits: Econ. Geology, v. 57, no. 2, p. 137-167. Kern, B. F., 1959, Geology of the uranium deposits near Stanley, Custer County, Idaho: Idaho Bur. Mines and Geology Pamph. 117, 40 p. Klepper, M. R., and Wyant, D. G., 1956, Uranium provinces, in Page, L. R., Stocking, H. E., and Smith H. B., com- pilers, Contributions to the geology of uranium and thorium . ..: U.S. Geol. Survey Prof. Paper 300, p. 17-25. Neuerburg, G. J., and Granger, H. C., 1960, A geochemical test of diabase as an ore source of uranium deposits of the Dripping Spring district, Arizona: Neues Jahrb. Mineral- ogie, Abh., v. 94, Festband Ramdohr, p. 759-797. Osterwald, F. W., 1956, Relation of tectonic elements in Pre- cambrian rocks to uranium deposits in the Cordilleran foreland of western United States, in Page, L. R., Stock- ing, H. E., and Smith, H. B., compilers, Contributions to the geology of uranium and thorium ...: U.S. Geological Survey Prof. Paper 300, p. 329-335. 1961, Critical review of some tectonic problems in Cor- dilleran foreland: Am. Assoc. Petroleum Geologists Bull., v. 45, no. 2, p. 219-287. GEOLOGICAL SURVEY RESEARCH 1964 THE OCCURRENCE OF PHOSPHATE ROCK IN CALIFORNIA By HOWARD D. GOWER and BETH M. MADSEN, Menlo Park, Calif. Abstract.-More than 60 occurrences of phosphate rock in California are located and briefly described. Most of the phos- phate occurs in siliceous rocks of Miocene age in the southern Coast Ranges and along the west side of the San Joaquin Valley. Carbonate-fluorapatite is the principal phosphate mineral. Pelletal phosphorites of middle and late Miocene age appear to offer the most promise of containing commercial deposits. The initial phase of a current U.S. Geological Sur- vey study of the occurrence of phosphate in California included a search of the literature for references on phosphate in the State and a compilation of known but previously unpublished phosphate-bearing locali- ties. Reconnaissance field examination was made of some of the more promising of these known localities, and in addition, nine new localities were found in areas where the geologic conditions seemed favorable for the occurrence of phosphate. This paper gives the location of 67 localities in California that contain significant quantities of phos- phate in sedimentary rocks (fig. 1), briefly describes each occurrence from north to south in the State (table 1), and summarizes the chemistry and mineralogy of the phosphate rock. Most of the occurrences are small and of little economic importance, but they offer a starting point for more detailed investigations and, because of the current interest in phosphate in Cali- fornia, they are presented here. Most of the phosphate localities are in the southern Coast Ranges between San Francisco and Los Angeles and along the west side of the San Joaquin Valley. At nearly all these localities the phosphate is in rocks of Miocene age. West of the San Andreas fault, phosphate commonly occurs in rocks of middle and late Miocene age. East of the fault, phosphate ap- pears to be most abundant in rocks of early Miocene age. The phosphate-bearing rocks are commonly thin bedded and closely associated with siliceous shale and bentonite. Bentonite laminae and thin beds make up as much as 10 percent of some phosphatic sections. In this paper, phosphorite refers to rocks composed dominantly of phosphate. There are three principal types of California phosphorite : pelletal, nodular, and argillaceous laminar. Most phosphorites are composed dominantly of one type, but may contain minor amounts of others. Pelletal phosphorites are composed of light-gray to dark-brown spherical pellets 0.1 mm to 1 mm in diameter. The pellets are structureless and contain silt-sized inclusions of nonphosphatic ma- terial, chiefly quartz and feldspar. Pellets are usually concentrated in soft to moderately hard beds 1 to 4 inches thick. Phosphate nodules are dark brown to white, ellipsoidal or irregular in shape, and up to 8 inches in length. They usually contain chalcedony and abundant inclusions of nonphosphatic clastic material, microfossils, and fragments of bone. Argillaceous laminar phosphorites consist of finely divided phos- phate and abundant silt-sized nonphosphatic clastic material in light-gray laminae. These laminae are often cemented with phosphate. Nodular and argilla- ceous laminar phosphorites usually contain appreciable amounts of calcium carbonate, chiefly in the form of Foraminifera tests, while most pelletal phosphorites contain little or no calcium carbonate. Dark-brown phosphatic mollusk shells are found in sandstone beds in several places. They usually occur with scattered phosphate pellets and nodules. In a few places phos- phatic fossils are abundant enough to form a phos- phorite. The chemistry and mineralogy of the California phosphorites are poorly known. The only material examined in detail thus far in the current investiga- tion was from the Indian Creek area of San Luis Obispo County (fig. 1, loc. 32). The deposit is in the Monterey Formation, here of middle Miocene age. The main phosphate-bearing zone is about 35 feet thick. This zone is composed of 75 percent siliceous U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D79-D85 D79 D80 ECONOMIC GEOLOGY |- TERamMa /.fi 120° c ‘i LASSEN ] 1 run' ax. l s %, # ~I PLUMAS } (r Az . ee wens te. f SIERRA & /a hon _, _.4}?~ NEVADA P. _ / PLACER k Xeixh "o> 09)», " \ o }‘\ " ', MONO 'x-38 Z ~ I Ay 118° -s 2] is »"Asig? "A,. | *+" XT \L 4 ® PW 2 ne o ae of cade 2 & %% . f AND]? f RENTQR}'54L\O:S \ $8 5 5 & 052 _ l’fiANGEIEfi‘IO g 36 < 557 £ & * co »65¢ - 59 ©6560 SANTA 200 MILES | SAN BERNARDINO 7~__’____ -pe" RIVERSIDE i \ p * rv34" 1 7 a- - \ ~ 1.-Map showing phosphate-rock localities of California. GOWER AND MADSEN TaBus 1.-Occurrence of phosphate rock in California [H. B. and M., Humboldt base line and meridian; M. D. B. and M., Mount Diablo base line and meridian; S. B. B. and M., San Bernardino base line and meridian} D81 TABLE 1.-Occurrence of phosphate rock in California-Con. [H. B. and M., Humboldt base line and meridian; M. D. B. and M., Mount Diablo base line and meridian; S. B. B. and M., San Bernardino base line and meridian] Locality Description Location No. Trinity County 1.«/... Phosphate in nonmarine sedi- | S% sec. 13, T. 3 N., mentary rocks of Oligo- R. 6 E. (H. B. cene(?) age (P. H. Lydon, and M.). California Div. Mines and Geology, oral communica- tion, 1963). Humboldt County Small specimen of presumably | Near Yager, probably sedimentary phosphorite in in T. 2 N., R. 3 E. the mineral collection of the (H. B. and M.). California - Division _ of Mines. Stratigraphic posi- tion and detailed locality de- scription are - unknown (Rogers, 1944, p. 419). Butte County Scattered phosphatic material | T. 20 N., R. 1 W. (M in shales of Late Cretaceous D. B. and M.). age (Thomson, 1962, p. 27). Solano County Limonitic phosphatic inter- | T. 4 N., R. 1 W. (M. beds in Eocene shales (Tol- D. B. and M.), man, 1943, p. 596). Potrero Hills gas field. San Joaquin County 6.1.1... Phosphatic nodules in shales | T. 2 N., R. 4 E. (M. of Paleocene and Eocene D. B. and M.), age (Knox, 1943, p. 590). McDonald Island gas field. Marin County 6: :. Phosphatic nodules and mud- | West side of Drakes stone _ interbedded _ with Bay. siliceous and _ calcareous shales, upper Miocene. San Francisco County veallaat " Phosphatic nodules in highly | South side of sheared graywacke and Clarendon Ave., black shale, Franciscan 200 feet east of Formation, Mesozoic (J. G. Seventh Ave., San Schlocker, oral communica- Francisco. tion, 1964). Santa Cruz County Phosphate pellets associated | SEM, see. 31, T. with a Tertiary glauconite, 8 S., R. 2 W. (M. San Lorenzo Formation ! D. B. and M.). (Cummings and others, 1962, p. 186-187). Phosphatic - nodules _ and | T. 9 S., R. 4 W. laminae in middle Miocene (M. D. B. and siliceous and - calcareous M.), Afio Nuevo shales. Point. See footnote on p. 83. Locality Description Location No. Inyo County 10. ..." Phosphate in Pleistocene sedi- | T. 9 S., R. 35 E. ments (Tucker, 1926, p. (M. D. B. and 520). M.). 6 miles east of Big Pine on the Big Pine-Saline Valley road. Fresno County Scattered phosphate pellets in | Sec. 19, T. 14 S., R. soft mudstone in lower part 12 E. (M. D. B. of the Eocene and Oligocene and M.). (?) - Kreyenhagen - Shale (Payne, 1951, p. 20). 12.-....L Nodules of apatitized wood | Sees. 6 and 7, T. and leucophosphite in lower 15 S., R. 12 E. part of the Upper Cretace- (M. D. B. and ous and Paleocene(?) M.). Moreno Formation (Gul- brandsen and others, 1963). 19 rse Phosphate pellets in basal | T. 20 S., R. 16 E. part of the upper Miocene (M. D. B. and McLure Shale Member of M.), Guijarral Hills the Monterey Formation oil field. (Anderson, 1952, p. 187). 14... Phosphate pellets in Eocene | T. 21 S., R. 16 E. and Oligocene(?) Kreyen- (M. D. B. and hagen Shale (Woodring and M.), Kettleman others, 1940, p. 147). Hills oil field. Monterey County 15..... Phosphate-pellet beds in sili- | SEMSW! sec. 16, ceous shales of the Miocene T. 16 S., R 2 E. Monterey Formation. (M. D. B. and M.), exposed in roadcuts. 16... Phosphate-pellet beds as | SEM projected sec. much as 1 foot thick in sili- 24, T. 16 S., R. ceous shales of the Miocene 6 E. (M. D. B. Monterey Formation and M.). (Galliher, 1931, p. 266; Rogers, 1944, p. 411). 17.".... Three 2- to 6-inch phosphate- | T. 17 S., R. 3 E. pellet beds in thin-bedded (M. D. B. and slightly phosphatic siliceous M.), roadcuts shale, of the Miocene(?) along Tularcitos Monterey(?) Formation. Creek, about 4 mile NW of USGS bench mark 1153, Rana Creek quad- rangle. 18.::.: Pellet phosphate beds in the | 450 feet W. of SE. Miocene Monterey Forma- cor. see. 21, T. tion. 19 S., R., 5 E. (M. D. B. and M.), roadcuts along Arroyo Seco road. Abundant phosphate pellets | T. 20 S., R. 6 E. in siltstone in the Miocene (M. D. B. and Vaqueros Formation M.), Vaqueros (Thorup, 1943, p. 466). Creek. 20... Pellet phosphate beds 4 to 6 | T. 20 S., R. 6 E. (M. inches thick in the Miocene 1). b. and - M.), Néggterey Formation (Reed, Vaqueros Creek. 1 £ Pellet phosphate beds in lower | NW sec. 13, T. 20 part of the Miocene Mon- terey Formation (D. L. Durham, oral communica- tion, 1963; Kleinpell, 1938, fig. 4). §., R. 6 E. (M. D. B. and M.), Reliz Canyon. D82 ECONOMIC GEOLOGY TABLE 1.-Occurrence of phosphate rock in California-Con. [H. B. and M., Humboldt base line and meridian; M. D. B. and M., Mount Diablo base line and meridian; S. B. B. and M., San Bernardino base line and meridian} TABLE 1.-Occurrence of phosphate rock in California-Con. [H. B. and M. Humboldt baselineand meridian; M. D. B. and M., Mount Diablo base line and meridian; S. B. B. and M., San Bernardino base line and meridian} Locality Description Location Locality Description Location No. ‘ No. Monterey County-Continued San Luis Obispo County-Continued P2 .. ew Phosphatic mollusk shells, | T. 20 S., R. 9 E. (M. | 33... Minor pelletal phosphate in | SEMSEM} see. 14, T. nodules and scattered pel- D. B. and M.). the Miocene Monterey For- 11 N., R. 28 W. lets in the lower Pliocene mation. (S. B. B. and M.). Egncll‘loDRiltio Formation . L. Durham, oral com- munication, 1963). Kan Comb 28... Phosphate pellets in the basal | On east line of sec. 15, part of the Pliocene, Pancho T_ 21 B.. R. 9 B. | 34... Phosphate pellets and pellet | NWMSEM see. 9, T. Rico Formation (Bramlette (M. D. B. and M.). beds in the Miocene Tem- 29 S., R. 20 E. and Daviess, 1945; Hughes, blor Formation (Woodring (M. D. B. and M.), 1963, p. 94-95). _ y and others, 1940, p. 130). Zemorra Creek. ills.; Phosphate pellets in the SE soc. 09, T. 21 S.,; | s5.-... Phosphatic nodules in the | T. 27 S., R. 28 E. Miocene Monterey Forma- K. 7 E. (M. D. B. Kern River Series (Plio- (M. D. B. and M.), tion (D. L. Durham, oral and M.) cene?) of Diepenbrock Mount Pozo oil communication, 1964). (1933, p. 12). field. 25-5; Phosphate pellet beds in the | sec. 32, T. | 36_____ Scattered phosphate streaks | T. 28 S., R. 25 E. Miocene Monterey Forma- 21 8., R. 9 E. (M. in shale of Miocene age (M. D. B. and M.), tion (Durham, 1964). D, B. and M.). (Kasline, 1941, p. 9). Rio Bravo oil field. 20-.-.-__- Phosphate pellets and phos- | T. 22 S., R. 10 E., | 37_____ Considerable number of phos- | T. 27 S., R. 20 E. phatic mollusk shells in the see. 5 (M. D. B. phate pellets in lower Mio- (M. D. B. and M.), lower Pliocene Pancho Rico and M.). cene rocks (Wharton, 1943, Belridge oil field. Formation (D. L. Durham, p. 503; Galliher, 1931, p. oral communcation, 1964). 258). Hughes (1963, p. 94-95) 88...... Phosphate nodules and string- | T. 29 S., R. 20 E also mentions phosphate in ers in the Miocene Mon- (M. D. B. and the Pancho Rico Formation - terey Formation (Wood- M.), - Chico- Mar- in the Salinas Valley. : ring and others, 1940, tinez Creek. Pi Thin phosphate-pellet bed in | T. 23, S., R. 8 E. p. 125). the MiozzlgneL Mlgntfirey Fori (M. D. B. {Eng lid), mation (D. L. Durham, ora west side of Tule communication, 1963). Canyon. Santa Barbara County Kings County Pelletal phosphate in sili- | 1,482,000 ft. W., ceous shale, lower part of 5092600 ft. N., as...... Phosphate pellets in lower | T. 23 S., R. 17 E. the Miocene Santa Mar- California plane part of the Miocene McLure (M. D. B. and M.), garita Formation (J. G. coordinate system, Shale Member of the Mon- Kettleman Hills oil Vedder, oral communica- east side of Branch terey Formation (Wood- field. tion, 1963). Pellets not Canyon. ring and others, 1940, p. 126; identified as phosphate Galliher, 1931, p. 258; Gal- mentioned by Hill and loway, 1943, p. 492; and others (1958, p. 2,996). Henny, 1930, p. 404). 40...... Phosphate pellets and pellet | T. 9N., R. 26 W., 29..___-] Phosphate pellets in the Mio- | T. 24, S., R. 18 E. beds in siltstone and sili- S. B. B. and M., cene Temblor Formation (M. D. B. and ceous shale, upper part of exposed in roadcuts (Curtin, 1955, p. 28). M.), Pyramid Hills the Miocene Santa Mar- 1,491,000 ft. W., oil field. garita Formation. - Phos- 509,600 ft. N., phate zone is more than 80 California plane San Luis Obigpe County feet thick (J. G. Vedder, coordinate system. oral communication, 1963). 41...2.4 Phosphate nodules and lami- | T. 10 N., R. 36 W. 30..._--| Five-inch nodular phosphate | NWMSW!M4 see. 24, nae in siliceous and calcar- (S. B. B. and M.), bed in middle Miocene shale. T. 25 8, R. 16 E. eous shales, lower member on the coast near (M. D. B. and M.), of the Miocene Monterey Mussel Rock. roadcut east side Formation (Woodring and U.S. Highway 466. Bramlette, 1950, p. 21.) T. 9 N.;, R. 36 W. S1. _<. Phosphate pellet beds and | NE@ANW!14 sec. 13, 42%... Phosphatic nodules and lami- (S. B. B. and M.), scattered pellets through T. 290 S., R., 16 E. nae in siliceous and cal- on the coast near T5-foot section of siliceous (M. D. B. and M.). careous shales of the lower Lions Head. shale and siltstone of the member of the Miocene Miocene Santa Marga- Monterey Formation rita(?) Formation. (Woodring and Bramlette, Abundant phosphate pellet | Indian Creek area, 1950, p. 18-20). beds in the upper part of the sec. 20, T. 28 S., 49...c. Phosphatic pellets and nod- | T. 9 N., R. 32 W. (S. Miocene Monterey Forma- tion (Reed, 1927, p. 195; Kleinpell, 1938, p. 121-122; and Bramlette, 1946, pl. 2). R; 15 E. (M. D. B. and M.). ules in the upper Miocene to lower Pliocene Sisquoc Formation (Woodring and Bramlette, 1950, p. 29). B. B. and M.), Gato Ridge, Foxen Canyon area. GOWER TABLE 1.-Occurrence of phosphate rock in California-Con. [H. B. and M., Humboldt base line and meridian; M. D. B. and M., Mount Diablo base line and meridian; S. B. B. and M., San Barnardino base line and meridian} AND MADSEN D83 TABLE 1.-Occurrence of phosphate rock in California-Con. [H. B. and M., Humboldt base line and meridian; M. D. B. and M. Mount Diablo base line and meridian; S. B. B. and M., San Barnardino base line and meridian] Locality Description Location No. Santa Barbara County-Continued 44... Phosphatic nodules in upper | T. 6 N., R. 33 W. (S. Miocene to lower Pliocene B. B. and M.), Sisquoc Formation (T. W. along Santa Ynez Dibblee, Jr., oral commu- River. nication, 1963). 45..... Phosphate pellets in the lower | West of Gaviota Pass Miocene Rincon Shale (T. on south side of W. Dibblee, Jr., oral com- Santa Ynez Moun- munication, 1963). tains. 146... Phosphatic shale (probably | Along Bixby Canyon not pelletal), in the Miocene near Point Concep- Monterey Formation tion. (Bramlette, 1946, pl. 2). 47.2... Phosphate pellets in rocks of | T. 5 N., R. 30 W. (S. early Miocene age (Kribbs, B. B. and M.), 1943, p. 375). Capitan oil field. 48... Phosphatic shales (probably | T. 4 N., R. 29 W. (S. nonpelletal), in the Mio- B. B. and M.), sea cene Monterey Formation cliffs west of (Bramlette, 1946, pl. 2). Naples. 4907 }.. Phosphate pellets in rocks of | T. 4 N., R. 29 W. (S. early Miocene age (Hill, B. B. and M.), El- 1943, p. 381). wood oil field. 50.....- Abundant phosphate pellets | T. 5 N., R. 27 W. (S. in lower Miocene rocks B. B. and M.), in (Bandy and Kolpack, 1963, Tecolote Tunnel. p. 136, 155). Ventura County Abundant phosphate pellets | Sec. 1, T. 6 N., R. and pellet beds in upper 24 W., and sec. 6, Miocene shales (W. R. T. 6 N., R. 285 W. Dickinson, oral communi- (S. B. B. and M.). cation, 1964). b2:.... Phosphate reported by Tucker | T. 3 N., R. 21 W. and Samson (1932, p. 270). (S. B. B. and M.). May be in Pliocene sedi- mentary deposits. Phosphatic shales in the | Sec. 31, T. 4 N., R. Monterey Formation 19 -W. (8. B. B. (Bramlette, 1946, pl. 2). and M.), Grimes Canyon. Los Angeles County $4.1... Phosphatic "material'" in up- | T. 4 N., R. 17 W. per Miocene sedimentary (S. B. B. and M.), rocks (Nelson, 1952, p. 60). Del Valle oil field. §55..... Phosphatic shales in the Mio- | T. 3 N., R. 16 W. cene Modelo Formation (S. B. B. and M.). (Winterer and Durham, 1962, p. 287). 56..... Phosphatic shales in the basal | Sec. 35, T. 1 N., R. part of the Miocene Modelo 1; W. (8. B. B. Forr;1)ation (Kleinpell, 1938, and M.). p. 47). $7.1... Pelletal phosphate in the basal | T. 1 S., R. 15 W. part of the Miocene Modelo Formation (Hoots, 1930, p. 105-106; Bramlette, 1946, pl. 2). (8. B. B. and M.). Locality Description Location No. Los Angeles County-Continued §$8.)... Phosphatic nodules in silice- | T. 2 S., R. 18 W. ous shales of the Miocene (8. B. B. and M.), Monterey Formation (R. F. south side of Dume Yerkes, oral communica- Cove. tion, 1963). 50:..... Nodular phosphate in the | T. 2 S., R. 15 W. upper Miocene Puente For- (S. B. B. and M.), mation (Hodges, 1944, p. Playa del Ray oil 6). field. 60:....: Phosphatic nodules in upper | T. 4 S., R. 14 W. Miocene shale (Davis, 1943, (S. B. B. and M.), p. 299). Torrance oil field. Phosphate nodules in Pleis- | T. 4 S., R. 14 W. tocene Lomita Marl (S. B. B. and M.), (Tucker, 1927, p. 328; Dietz Lomita quarry. and others, 1942, p. 831; Rogers, 1944, p. 421; and Emery and Dietz, 1950, p. 12). Phosphatic shale, Altamira | T. 5 S., R. 15 W. Shale Member of the Mio- (S. B. B. and M.), cene Monterey Formation Lunada Bay. (Woodring and - others, 1936, p. 139). 63...... Phosphatic laminae in Val- | T. 4 S., R. 15 W. monte Diatomite Member (S. B. B. and M.), of the Miocene Monterey Malaga Cove. Shale (Woodring and others, 1946, p. 34). 64:.-... Phosphatized Foraminifera of | Wilson Cove, San early(?) Miocene age (Olm- Clemente Island. sted, 1958, p. 65). San Bernardino County 65.:1... Phosphatic nodules in upper | Secs. 21 and 22, Miocene Yorba Member of T. 3 S., R. SW. the Puente Formation (8. B. B. and M.); (Durham and Yerkes, 1964, in San Juan p. B59). Tunnel. Orange County 66..2... Phosphate nodules in the Mio- | 4,200 ft. N., 700 ft. cene Monterey Formation E. of SE cor. see. (J. G. Vedder, oral com- 26, T. 6 10 munication, 1963). Emery W. (S. B. B. and and Dietz (1950, p. 12) re- M.), Newport Bay. port _ large phosphatic nodules in marine conglom- erate overlying the Monte- rey Formation at Newport Bay. San Diego County 67:22 White phosphatic calcareous | T. 18 S., R. 2 W. (S. bed (Merrill, 1916, p. 717). Probably in the Pliocene San Diego Formation. B. B. and M.), mesa east of Otay. 1 E. E. Brabb, 1960, Geology of the Big Basin area, Santa Cruz Mountains, Cali- fornia: Stanford Univ., unpub. Ph.D. thesis, 192 p. D84 shale, 18 percent phosphate pellet beds, and 7 percent bentonite laminae and beds. The siliceous shale is laminated to very thin bedded and locally contains abundant fish remains, chiefly scales, and scattered phosphate pellets. The pellet beds range from a frac- tion of an inch to 10 inches in thickness. They have sharp irregular to planar bases and grade upward into the overlaying siliceous shale. Most pellet beds con- tain a few (less than 1 percent) coarse quartz grains. Foraminiferal studies by Patsy B. Smith (oral com- munication, 1963) indicate that the phosphatic zone contains a shallow-water fauna. A chemical analysis of a pellet concentrate from Indian Creek is shown in table 2. The chemical analy- sis and the results of X-ray diffraction studies show that the phosphate mineral is carbonate-fluorapatite. X-ray studies of phosphorite samples from 20 other localities listed in table 1 have been made, and all but 2 had similar mineralogy. The two exceptions are the nonmarine phosphate of locality 1 and the leucophos- phite of locality 12. TaBu® 2.-Chemical analysis of a pelletal phosphate concentrate from locality 32, Indian Creek area, San Luis Obispo County ' Constituent Percentage s. ees di sao ean ne ew sia sen uas ee 1. 8 :.: ri een nde 1.0 F6203 ____________________________________________ . 28 n. l cl.. annem uae sie e.,. . 08 F cell ick e ei al. . 19 CAFE eer .i cu nae nabe bebes eee nan 51. 8 NagO ____________________________________________ . 43 Urr eee el cin Lene ne be rer s on O07 HMO HEL EUL eee re are weusese bo wen 1. 5 H;OF ssc LLL Ll an ede awa nan o aam eee bas s 2. 2 NOs s e ol rone enn eal dl ee r aer ie dee a nea ase nl . 10 Taos. se el . nol dil aL dao e. aie een t 35. 7 sree cero. nana nie ana aad ae naa s o 0 CO.. sake an ere ee ce 2. 5 P ae ree Pee a al am ana aan a an aa aaa adil 4. 0 Deduct {O,; equivalent to F. -L. c (-1.7) Totals. lst nessun aas 99. 45 + Collected by R. A. Gulbrandsen. Rapid rock analysis by P. Elmore, S. Botts, G. Chloe, and H. Smith. Among the California occurrences, the pelletal phos- phorites of middle and late Miocene age appear to offer the most promise of being commercially valuable. Particularly promising are deposits in the upper Mio- cene Santa Margarita Formation along the southeast- trending belt through localities 31, 40, and 51 (fig. 1) of San Luis Obispo, Santa Barbara, and Ventura Counties, and those in the middle and upper Miocene Monterey Formation in Monterey and San Luis Obispo Counties. The. lower Miocene pelletal phos- phorites along the west side of the San Joaquin Valley also deserve attention. Some of the nodular and argillaceous laminar phosphatic shales of western and southern Santa Barbara and western Los Angeles ECONOMIC GEOLOGY Counties are more than 200 feet thick and appear to contain large tongues of phosphate. They are of low grade, however, and their high calcium carbonate con- tent would hinder their use by normal acid-treatment procedures. REFERENCES Anderson, J. Q., 1952, Guijarral Hills oil field, in Field trip routes, geology, oil fields: Am. Assoc. Petroleum Geolo- gists, Soc. Econ. Paleontologists and Mineralogists, and Soc. Econ. Geologists Guidebook, Joint Ann. Mtg., Los Angeles, Calif., 1952, p. 184-188. Bandy, O. L., and Kolpack, R. L., 1963, Foraminiferal and sedimentological trends in the Tertiary sections of the Telcolote Tunnel, California: Micropaleontology, v. 9, no. 2, p. 117-170. Bramlette, M. N., 1946, The Monterey formation of California and the origin of its siliceous rocks: U.S. Geol. Survey Prof. Paper 212, 57 p. Bramlette, M. N., and Daviess, S. N., 1945, Geology and oil possibilities of the Salinas Valley, California: U.S. Geol. Survey Oil and Gas Inv. Prelim. Map 24. Cummings, J. C., Touring, R. M., and Brabb, E. E., 1962, Geol- ogy of the northern Santa Cruz Mountains, California: California Div. Mines Geol. Bull. 181, p. 179-220. Curtin, George, 1955, Pyramid Hills oil field [California] : California Oil Fields, v. 41, no. 2, p. 25-33. Davis, E. L., 1943, Torrance oil field, in Geologic formations and economic development of the oil and gas fields of California: California Div. Mines Bull. 118, p. 298-300. Diepenbrock, Alex, 1933, Mt. Poso oil field: California Oil Fields, v. 19, no. 2, p. 4-35. Dietz, R. S., Emery, K. O., and Shepard, F. P., 1942, Phos- phorite deposits on the sea floor off southern California: Geol. Soc. America Bull., v. 53, no. 6, p. 815-848. Durham, D. L., 1964, Geology of the Cosio Knob and Espinosa Canyon quadrangles, Monterey County, California: U.S. Geol. Survey Bull. 1161-H. Durham, D. L., and Yerkes, R. F., 1964, Geology and oil re- sources of the eastern Puente Hills area, southern Cali- fornia: U.S. Geol. Survey Prof. Paper 420-B, p. B1-B62. Emery, K. O., and Dietz, R. S., 1950, Submarine phosphorite deposits off California and Mexico: California Jour. Mines and Geol., v. 46, no. 1, p. 7-15. Galliher, E. W., 1931, Collophane from Miocene brown shales of California: Am. Assoc. Petroleum Geologists Bull., v. 15, no. 3, p. 257-269. Galloway, John, 19483, Kettleman Hills oil fields, in Geologic formations and economic development of the oil and gas fields of California: California Div. Mines Bull. 118, p. 491-4983. Gulbrandsen, R. A., Jones, D. L., Tagg, K. M., and Reeser, D. W., 1963, Apatitized wood and leucophosphite in nodules in the Moreno Formation, California: Art. 85 in U.S. Geol. Survey Prof. Paper 475-C, p. ©100-C104. Henny, Gerard, 1930, McLure shale of the Coalinga region, Fresno and Kings Counties, California: Am. Assoc. Petro- leum Geologists Bull., v. 14, no. 4, p. 403-410. Hill, M. L., 1943, Elwood oil field, in Geologic formations and economic development of the oil and gas fields of Cali- fornia: California Div. Mines Bull. 118, p. 380-383. GOWER Hill, M. L., Carlson, S. H., and Dibblee, T. W., Jr., 1958, Strati- graphy of Cuyama Valley-Caliente Range area, California : Am. Assoc. Petroleum Geologists Bull., v. 42, no. 12, p. 2973-3000. Hodges, F. C., 1944, Gas storage and recent developments in the Playa del Rey oil field [California]: California Oil Fields, v. 30, no. 2, p. 3-10. Hoots, H. W., 1930, Geology of the eastern part of the Santa Monica Mountains, Los Angeles County, California: U.S. Geol. Survey Prof. Paper 165-C, p. 83-134. Hughes, A. W., 1963, The two sides of Salinas, in Guidebook to the geology of Salinas Valley and the San Andreas fault: Am. Assoc. Petroleum Geologists, Pacific Sec., Ann. Mtg. 1963, p. 94-97. Kasline, F. E., 1941, Rio Bravo oil field [California]: Califor- nia Oil Fields, v. 27, p. 9-12. Kleinpell, R. M., 1938, Miocene stratigraphy of California: Tulsa, Okla., Am. Assoc. Petroleum Geologists, 450 p. Knox, G. L., 1948, McDonald Island gas field, in Geologic for- mations and economic development of the oil and gas fields of California: California Div. Mines Bull. 118, p. 588-590. Kribbs, G. R., 1943, Capitan oil field, in Geologic formations and economic development of the oil and gas fields of California: California Div. Mines Bull. 118, p. 374-376. Merrill, F. J. H., 1916, The counties of San Diego, Imperial: California Mining Bur., 14th Rept. State Mineralogist, pt. 5, p. 635-748. Nelson, L. E., 1952, Del Valle and Ramona oil fields, in Field trip routes, geology, oil fields: Am. Assoc. Petroleum Geologists, Soc. Econ. Paleontologists and Mineralogists, and Soc. Econ. Geologists Guidebook, Joint Ann. Mtg., Los Angeles, Calif., 1952, p. 57-63. Olmsted, F. H., 1958, Geologic reconnaissance of San Clemente Island, California: U.S. Geol. Survey Bull. 1071-B, p. 55-68. Payne, M. B., 1951, Type Moreno formation and overlying Eocene strata on the west side of the San Joaquin Valley, Fresno and Merced Counties, California: California Div. Mines Spec. Rept. 9, 29 p. A AND MADSEN D85 Reed, R. D., 1927, Phosphate beds in the Monterey Shales [abs.]: Geol. Soc. America Bull., v. 38, no. 1, p. 195-196. Rogers, A. F., 1944, Pellet phosphorite from Carmel Valley, Monterey County, California: California Jour. Mines and Geology, v. 40, no. 4, p. 411-421. Thomson, J. N., 1962, Geology of the Kione Formation: Joaquin Geol. Soc. Selected Papers, v. 1, p. 27-85. Thorup, R. R., 1943, Type locality of the Vaqueros formation, in Geologic formations and economic development of the oil and gas fields of California: California Div. Mines Bull. 118, p. 463-466. Tolman, F. B., 1943, Potrero Hills gas field in Geologic forma- tions and economic development of the oil and gas fields of California: California Div. Mines Bull. 118, p. 595-598. Tucker, W. B., 1926, Inyo County: California Mining Bur., 22d Rept. State Mineralogist, v. 22, no. 4, p. 453-530. 1927, Los Angeles County: California Mining Bur., 23d Rept. State Mineralogist, no. 3, p. 287-345. Tucker, W. B., and Sampson, R. J.. 1932, California Mining Bur., 28th Rept. State Mineralogist, no. 3, p. 247-277. Wharton, J. B., 1943, Belridge oilfield, in Geologic formations and economic development of the oil and. gas fields of California: California Div. Mines Bull. 118, p. 502-504. Winterer, E. L., and Durham, D. L., 1962, Geology of south- eastern Ventura basin, Los Angeles County, California: U.S. Geol. Survey Prof. Paper 334-H, p. 275-366. Woodring, W. P., and Bramlette, M. N., 1950, Geology and paleontology of the Santa Maria district, California: U.S. Geol. Survey Prof. Paper 222, 185 p. Woodring, W. P., Bramlette, M. N., and Kew, W. S. W., 1946, Geology and paleontology of Palos Verdes Hills, Califor- nia: U.S. Geol. Survey Prof. Paper 207, 145 p. Woodring, W. P., Bramlette, M. N., and Kleinpell, R. M., 1986, Miocene stratigraphy and paleontology of Palos Verdes Hills, California: Am. Assoc. Petroleum Geologists Bull., v. 20, no. 2, p. 125-149. Woodring, W. P., Stewart, Ralph, and Richards, R. W., 1940, Geology of the Kettleman Hills oil field, California; strati- graphy, paleontology, and structure: U.S. Geol. Survey Prof. Paper 195, 170 p. San GEOLOGICAL SURVEY RESEARCH 1964 THE DISTRIBUTION AND QUALITY OF OIL SHALE IN THE GREEN RIVER FORMATION OF THE UINTA BASIN, UTAH-COLORADO By W. B. CASHION, Denver, Colo. Abstract.-Oil-shale beds of the Green River Formation (Eocene) were deposited in an unusual lacustrine environment that preserved thick sequences of kerogenaceous material. These beds are an important potential source of liquid syn- thetic fuel. Incomplete oil-yield assay data indicate that in the Uinta Basin a sequence of kerogen-rich beds 15 feet or more thick with an average oil yield of 15 gallons per ton contain about 321 billion barrels of oil. The extensive thick oil-shale beds of the Rocky Mountain region are of prime importance as a possible source of synthetic liquid fuel. The Green River Formation of Eocene age underlying parts of Utah, Colorado, and Wyoming contains much of the oil- shale resources of the United States. A large portion of the Green River oil-shale beds lies in the Uinta Basin of Utah and westernmost Colorado. The physical and mineralogic characteristics of the oil-shale beds of the Green River Formation have been described in detail by Bradley (1931, p. 22-37, 39-40), and some of these characteristics are discussed below. The oil shales are dense magnesian marlstones with a high content of organic matter. The organic matter is of two types: (1) structureless, translucent, and lemon yellow to reddish brown material, and (2) com- plete or fragmentary remains of organisms such as algae, protozoa, and insects, and parts of higher plants -spores, pollen grains, or minute pieces of tissue. The predominant inorganic constituents of the shale are dolomite, calcite, and clay minerals. Oil shale contains little or no free oil that can be removed by petroleum solvents, but the organic matter (kerogen) can be converted to oil by destructive dis- tillation at high temperature, commonly known as retorting. The Green River Formation is composed predomi- nantly of lacustrine beds deposited for the most part in two large lakes. One of these lakes was north of the present Uinta Mountains and lay almost entirely in southwestern Wyoming and northwesternmost Col- orado. The other was south of the Uinta Mountains in eastern Utah and western Colorado and lay prin- cipally in the area now occupied by the Uinta and Piceance Creek basins. Bradley (1930, p. 88) referred to the northern lake as Lake Gosiute and the southern lake as Lake Uinta. The precise age relation of the two Eocene lakes is not known, but they were, in part, contemporaneous. During part of Green River time these lakes may have been connected around the eastern end of the Uinta Mountains, but evidence of such a connection, if it ever existed, has been removed by erosion. The present-day Uinta and Piceance Creek basins are separated by a structurally high area, the Douglas Creek arch, but it is postulated that during much of Green River time these areas were covered by one body of water, for there is a remarkable simi- larity between the oil-shale sequences in the two basins. In many cases, precise correlation can be achieved by a comparison of oil-yield histograms representing assays of cored sections of the basin. The strata of the Green River Formation can be divided roughly into three lithologic groups, each one representing a particular lacustrine environment. One group is characterized by beds of algal, ostracodal, and oolitic limestone, shale, siltstone, and sandstone, and contains negligible amounts of kerogenaceous mat- ter. These beds were deposited in shallow water near the margins of the lake and are peripheral to, and interfinger basinward with, beds deposited in the other two environments. A second group contains beds of marlstone, siltstone, tuff, and minor amounts of oil shale. The environment of this group of beds was located far enough from shore to prevent the deposi- U U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D86-D89 D86 CASHION tion of coarse clastic material and was in water deep enough to prevent disturbance by wave or current action. If abundant kerogenaceous matter was de- posited in this environment it was not preserved. The third group of beds, composed of oil shale, marlstone, and tuff, was, for the most part, deposited along the trough of the lake near the axis of deposition:. This environment was conducive to the accumulation and preservation of kerogenaceous matter and thus pro- duced the thick oil-shale sequence of the Green River Formation. Bradley (1926, p. 127) postulated that the rich oil shale formed in water that was probably less than 100 feet deep, and apparently resulted from a periodic concentration of organic matter due to a very pronounced reduction in the volume of the lake. Chemical and thermal stratification of the lake waters played an important role in the deposition of oil-shale beds (Bradley, 1948, p. 644). Stratification must have been a more critical factor than depth of water, for numerous widespread continuous thin rich oil-shale beds can be correlated from the Uinta Basin to the Piceance Creek basin, and it is unlikely that the lake was of uniform depth over such a large area during the deposition of each bed. Also, in the areas where oil-shale sequences interfinger with nearshore se- quences, some oil-shale beds show mud cracks or lie adjacent to algal limestone, denoting shallow-water deposition. Many fluctuations in the size and depth of the lake produced complex interfingering and facies changes between the lithologic groups described above, as well as interfingering and facies changes involving near- shore lacustrine deposits and fluvial deposits. Above, below, and peripheral to the main body of the Green River Formation there are sandstone, conglomerate, and shale beds of fluvial formations that interfinger with it. Fluctuations of the lake, and the accompany- ing decrease or increase of the inflow of clastic ma- terial, enlarged or reduced the area in which oil-shale beds were being deposited but had little effect on these beds near the axis of deposition. The position of this axis did not change greatly during much of Green River time, and a thick sequence of organic-rich beds accumulated. The axis trends roughly east-west, and its position can be determined from the location of lines showing. maximum thickness of oil-shale beds on figure 1. The position of the axis is obvious in the area east of the Green River, but is poorly defined in the area west of the river. Reliable assay data in the western area are scarce, so the reason for the poor delineation of the axis by oil-shale thickness is not known. Perhaps the environmental conditions of this area were not favorable for the accumulation of a D87 thick oil-shale sequence or perhaps assay data from additional drill holes will show a more pronounced depositional trend. The richest and thickest oil-shale bed in the Green River Formation is the Mahogany bed. This bed, deposited during a stage when Lake Uinta was wide- spread, is found over a very large area in the Piceance Creek and Uinta basins. Its outcrop in the Uinta Basin is shown on figure 1. The maximum outcrop thickness of the Mahogany bed in the Uinta Basin is about 8 feet, along the White River approximately 5 miles west of the Utah-Colorado boundary. Its maximum thickness is in the subsurface along the depositional axis of the basin, and it thins in all directions away from the depositional axis. The Mahogany bed and adjacent rich oil-shale beds form a prominent outcrop feature-the Mahogany ledge, the subsurface correlative of which is the Mahogany zone. The maximum thickness in outcrop of the ledge is about 60 feet at the White River locality mentioned above. The ledge thins more abruptly away from the depositional axis than does the Mahogany bed, and in much of the southern part of the Uinta Basin the Mahogany ledge is formed by only the Mahogany bed. Near the axis of deposition, stratigraphic sequences a few hundred feet thick above and below the Mahogany ledge contain many oil-shale beds. In the southwest- ern part of the Uinta Basin a significant lower oil- shale zone (fig. 1), below the Mahogany bed, was mapped by Bradley (1931, pl. 1). This zone is not present in the southernmost part of the basin and was not mapped in the easternmost part. Estimates of oil-shale resources are based on the oil-yield assay data from groups of samples that, for the most part, represent continuous rock sequences. These sequences are represented by assays of cores, rotary-drill cuttings, and outcrop channel samples. Actual oil yields of stratigraphic sections are most accurately represented by assay data from cores. Ro- tary cuttings are less accurate than cores, owing to the possibility of contamination during drilling or human- error during collection. Generally, surface samples are less reliable than subsurface samples, be- cause of weathering. For example, a sample of weath- ered shale from the Mahogany bed assayed 12.8 gal- lons of oil per ton, whereas an unweathered sample of the bed taken 2 feet beneath the surface at the same locality assayed 45.5 gallons per ton (Guthrie, 19838, p. 99). Although assay oil yields of weathered sam- ples are known to be low, a constant upgrading factor cannot be applied because of great variation in the weathering of oil-shale beds. ECONOMIC GEOLOGY "(1 'Id 'I86T) 4opeig wou; pogytpouw 1oary usor ay) ;o qsom gore dorogn( £uesoyep; 94} mcffiwowaz uonsuno Joary usoirn oy} Jo qued Jo sore smoys tojjeg 'J [to ;o suofe8 ¢1 Jo aSeJoat use pjol4 [IIA Jey; uonsuio Joary Uoolr) oY} ut spoqg oreys-[IO JO '499; UI I I SIIIW OZ OT 0 *(w) pag ojno j00J-GT E (499; (QT St ssouyory p - 'uo4 god 'ssouyxorgy; Surmoys 'eare uiseqg oy) Jo depy-'T sxap1I4 OI I serem o ofone gored I I 1 I | f cavi#0100 __ — HyiLn _ A # ua KN qi0d I | - sganag* mWwflMVfl chwmfimwfi fo esiy | sm Asa I apueadlg a g k CZ surequnow +x hs we acane mee ms me 70 axy1 | _ Liys I saas acaoym paysU() 1joeu0) popo.a si aquanbas paysop pioys 'parnoo acsym paysup Buo; wl areys [to Jo yoedost % Ho A c NOILYNYT4X3 fam: 2, ALNAOYNCS--~__NOSHYO $ s Il/ flWfiIII|I|IIIII 9 is exult | C_ 0—H 5 t n mw T / 21g ~> x cap hel R F "v—Ww I ;/;/{\ ”NJ auoz ajeys Hf - |Z K 10 19m07 (fl & " 5C y 0 A al 3 _AN -. Op '% A 3 & lA } ate Hf >> \ \ le 73 4 C x O10 N_D # $ 88 / ~ e +\\VH < iI } A) 3 H| 4 elles fix S(\m le Te 2|Z - AYC ya Hl Auagnoug 219 !> - | < OY O \ | ue _ ,,,,,,,,,,,,,,,, Uyevm/? I Xz, 1 — waa _ ; | x*: . eO1l ell CASHION Assays of groups of samples representing 40 core holes, 110 exploratory wells, and about 25 surface localities were used in the estimate of oil-shale re- sources given here. Core-hole and exploratory-well assay data used to calculate resource figures for this report have been published by the U.S. Bureau of Mines (Stanfield and others, 1954; 1964). All the core holes are located in the southeastern part of the basin, and most of the exploratory wells are located in the eastern part of the basin. Thus, control points of any type are sparse in the western part of the basin, and there are no core- assay data to substantiate rotary-cuttings data from a critical part of the eastern Uinta Basin. In addition, assays of cuttings from some wells in the east-central part of the basin show anomalous thicknesses of rich oil shale. Therefore, oil-shale beds in the area of relatively closely spaced core holes are classed as indi- cated resources, and the remainder of the oil-shale beds are classed as inferred resources. The estimate of oil-shale resources given in this re- port is for a sequence of rocks, including the Mahog- any ledge and adjacent beds, 15 feet or more thick having an average oil yield of 15 gallons per ton. No allowances are made for losses in mining or retorting. It is estimated that oil-shale beds of the Uinta Basin D89 contain indicated resources amounting to 31 billion barrels of oil, most of which is in an area east of the Green River and south of the latitude of the mouth of the White River; the beds contain inferred resources of 290 billion barrels. This 321 billion barrels of re- sources is in an area of approximately 3,000 square miles and is in a sequence that is believed to have a maximum thickness of more than 700 feet. REFERENCES Bradley, W. H., 1926, Shore phases of the Green River Forma- tion in northern Sweetwater County, Wyoming: U.S. Geol. Survey Prof. Paper 140-D, p. 121-131. 1930, The varves and climate of the Green River epoch : U.S. Geol. Survey Prof. Paper 158-E, p. 87-110. 1931, Origin and microfossils of the Green River For- mation of Colorado and Utah: U.S. Geol. Survey Prof. Paper 168, 58 p. 1948, Limnology and the Eocene lakes of the Rocky Mountain region: Geol. Soc. America Bull., v. 59, no. 7, p. 635-648. Guthrie, Boyd, 1938, Studies of certain properties of oil shale and shale oil: U.S. Bur. Mines Bull. 415, 159 p. Stanfield, K. E., Rose, C. K., McAuley, W. S., and Tesch, W. J., Jr., 1954, Oil yields of sections of Green River oil shale in Colorado, Utah, and Wyoming, 1945-52: U.S. Bur. Mines Rept. Inv. 5081, 153 p. Stanfield, K. E., Smith, J. W., and Trudell, L. G., 1964, Oil yield of sections of Green River oil shale in Utah, 1952- 62: U.S. Bur. Mines Rept. Inv. 6420, 217 p. GEOLOGICAL SURVEY RESEARCH 1964 BTU VALUES OF FRUITLAND FORMATION COAL DEPOSITS IN COLORADO AND NEW MEXICO, AS DETERMINED FROM ROTARY-DRILL CUTTINGS By JIM S. HINDS, Farmington, N. Mex. Abstract.-Btu values of coal obtained from wells show that coal from the Fruitland Formation of Late Cretaceous age is of highest quality in the northwest part of the San Juan basin when reported on an "as received" basis. On a "moisture and ash free" basis the Btu values show a steady increase from southwest to northeast. A comprehensive study of the coal deposits of the Upper Cretaceous Fruitland Formation, which under- lies the San Juan basin at depths of as much as 4,500 feet, was made to provide a basis for coal classification of public land remaining in outstanding coal-land withdrawals within the basin. To satisfy this objec- tive it was necessary to determine the thickness, depth, and heating value of Fruitland coal deposits through- out the basin. As the Fruitland Formation crops out only in a narrow band on the north, west, and south sides of the basin (fig. 1), the study was necessarily a subsurface one and was conducted through examina- tion of electric logs, drilling-rate logs, cores, and sam- ples from rotary drill cuttings. This paper concerns the well sampling, which was undertaken primarily to obtain representative Btu values of Fruitland coal beds throughout the San Juan basin. GEOLOGY The Fruitland Formation of Late Cretaceous age consists of very irregularly bedded brackish and fresh-water deposits of sandstone, siltstone, shale, and coal. It lies conformably above the regressive marine Pictured Cliffs Sandstone and grades into the over- lying Kirtland Shale of fresh-water origin. The beds are lenticular throughout the formation, and few of the rock units are persistent for distances greater than 1 or 2 miles. The coal beds, however, are more per- sistent than the associated sandstone and shale beds; some coal beds may be traced in the outcrop and sub- surface for 4 to 6 miles. In addition to its lenticu- larity, the Fruitland Formation is characterized in the subsurface throughout the basin by intertonguing with the underlying Pictured Cliffs Sandstone. The intertonguing indicates temporary pauses and minor transgressions in the general regression of the sea. Because of their lenticularity, the coal beds of the Fruitland Formation must be studied collectively. Generally speaking, the coal beds are thickest and most numerous in the northwest quadrant of the basin, where many wells have penetrated coal beds 30 to 40 feet thick, as indicated by samples and electric logs. The quality of Fruitland coal is also better in the northwest quadrant, ranging usually between 12,000 and 13,000 Btu per pound on an "as received" basis as opposed to values elsewhere generally of 10,000 to 12,000 Btu. The coal beds become progressively fewer and thinner toward the southern and eastern margins of the basin. On the east side of the basin, from Dulce to Cuba, N. Mex., the Fruitland Formation is missing from the outcrop, its eroded edge being covered by younger sedimentary rocks. Figure 2 shows a well section of the Fruitland For- mation, the electric-log response to the coal beds, and an analysis of Fruitland coal. This particular well, about 10 miles northeast of Farmington, N. Mex., was chosen for illustration because it depicts very nearly the average lithic character of the Fruitland Forma- tion. Coal beds occur at random throughout the ver- tical extent of the formation, although there is usually a concentration or zone of coal beds in the lowest part of the formation. The coal may be directly overlain, underlain, or interbedded with either sandstone, silt- stone, shale, or carbonaceous shale. This sequence of U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D90-D94 D90 HINDS county ? o1 1,230 108° ) f | Durango 1 § - // ARCHULETA MONTEZUMA F '% LA PLATA COUNTY COUNTY Area of report NEW MEXICO 12,07 12,1 / o 0 o 40 92 a COLORADO _ _ & * 10,6405 NEW MEXICO f 611,020 , Dulce BY p13.09%0 12.350 { 11,550 12,040 * 012'630 f 2 11,250 A pla 390 ois o y yT pitas tg fe 10,800 is € p11.840 o 12.960 g\\ 12,020 11,460 \ Farmingtony fae 0 I $0 (4 \ S 12,3600 12.830 I 710,780 { 13,310 1 Y ' 11,0003 " 411.910 12 190 $"! & $ 11,7409 _ 12,010 on 11,670 11.580 I , 760 1 11,7 19.270 p10,640 \| 11,970 11,440 1 \ 0 12,370 p11449 9170 a 560 \ 11810 p12690 _ 11.080 a p10.780 4 11,540 CY. , p12.130 \ \ SAM.. 4UAY . COUNITE 3 11,760 RIO __ ARRIBA _ COUNTY 3 I I Eroded edge of Fruitland III 010’270 d280 Formation, concealed / S &! 010,440 by younger rocks \{ «" Outcrop of Fruitland 9,960 1 Formation v? ao \ 9 10,990 \ 1 G ) 11.790 7 O pa 11,840 ye p11 410 . Y P Vac f 1 | | I I \ ..... } EXPLANATION t J I 11.230 \ l ; Cuba _ / Sampled locality / Number indicates "as received" SS I Btu value of coal Well section given on figure 2 MC KINLEY COUNTY f f 1IO 1‘5 210 MILES Fiaur® 1.-Map showing outcrop of the Fruitland Formation, location of drill holes sampled, and "as received" Btu values of coal 742-652 O-64--7 samples. D92 SPONTANEOUS RESISTIVITY POTENTIAL (Ohms m*/m) (Millivolts) 0 50 100 my wifi. 1500-+ & w 1600+-F Fruitland 4 Formation T '— O. L o 1700 1 N Pictured Cliffs Sandstone 'FicurE 2.-Lithologic section and electric log of a well in the Fruitland Formation, showing Location of well shown on figure 1. | typical occurrence of coal. rocks definitely does not represent cyclic deposition, but rather a complex interbedding of coastal-swamp, flood-plain, and sluggish stream deposits which were laid down behind the shores of the Cretaceous sea as it withdrew to the northeast. SAMPLING AND ANALYSIS As of January 1964, various coal beds of the Fruit- land Formation had been sampled at 64 separate well locations in the San Juan basin. The attempt was made at each locality to sample the lowest economically important coal bed or zone of the formation; later, one analysis per well was made of coal sampled. Sampling uncertainties prevented absolute consistency, but all samples were from the lower part of the for- mation if not the lowest coal bed. The samples were obtained by collection of cuttings from shale shakers as the cuttings from coal zones were discharged from the bore hole. After collection, the cuttings were thoroughly mixed to insure representative sampling, and then were washed at the well site to remove drill- ing mud. The samples then were dried by a cool forced-air current and floated in carbon tetrachloride (specific gravity 1.59) to remove rock cuttings and cavings picked up by the sample in the mud column during circulation (the specific gravity of coal ranges generally from 1.2 to 1.5). The lighter fraction from ECONOMIC GEOLOGY EXPLANATION Sandstone RESULT OF SAMPLE ANALYSIS Btu 12,370 | Moisture 2.2 | Volatile material 38.8 | Fixed carbon 45.3 Ash 13.7 | Sulfur .6 | <} Analyzed sample from this interval the floating process was then sent to the U.S. Bureau of Mines laboratory at Pittsburgh, Pa., for finalysis. Because of the flotation, the resultant Btu values rep- resent maximum figures for the heating values of the coals sampled. Any shale or sand partings and car- bonaceous material with a specific gravity greater than 1.59 present in the sampled zone were removed through flotation. Hence, the reported values represent the heating value of the coal without partings. These samples would be comparable to regular channel mine samples from which all partings are exclude} In addition to Btu data, information was obtained and recorded on moisture, volatile matter, fixed carbon, ash, and sulfur content of coal of the Fruitlafid For- mation. These data are summarized in the accom- panying table. Major constituents of coal from the Fruitland Formation Average Constituent Range (percent) _ (percent) Moisture........... {bn cusps = enaneuue 0. 8- 6. 7 2. 6 Volatile 20. 6-41. 7 35. 8 Fixed 33. 3-56. 4 - 43. 2 .S. .A LGC USA L Lean a o a 9. 8-30. 5 _ 18. 4 Sulfurs_.... 2 csc eus ake o % of ag 0. 5- 2. 2 0. 75 The location of sampled wells and the "as reézeived” Btu values obtained at each location are shown on figure 1. The values range from 9,170 to 13,350. The distribution. of the Btu values shows that the quality HINDS D93 108° 3 ' | Durango f Gece . f / COLORADO / ARCHULETA MONTEZUMA * LA PLATA COUNTY Area of _| county ? Teron ’% NEW MEXICO U Outcrop of Fruitland \ 1 Formation 015'440 15,600 golorabo __ NEW MEXICO _ 15,440 O 15,100 R Dulce a%% 15.280 o15,470 2 R 15,190 ~ 14,570 014,770 O M f‘, 015,380 \ \\ 0 ~~ x ) 14,700 tal a - 0 14,790 's. / 14,4605 gf5170 > 25 X 14,800 Farmington ( no 0 is p15.470 $3 \ \ 0 p o & 9 is." SY 14,820 ( 14,750 x 15,330 ( 014,420 15,160 er to 5s \ o:" Bx 14,4000 ©14,370 14,670 Sy \\ O 15,480 14,2900 014,430 {4.87 hs ©14,920 (s 0700 f : ©14,920 o \ 14,190 14,820 14,700 4 | \\ S o o. o. 14,7200 § R 14,440, 14,600 14,800 14,700 15.159 15.010 V 15,020 ( O + 14,4305 Y? - 15.120 \\ 5° 1 $;000 o- __ |_ AS county \ RIO ARRIBA coUntTy / U U S \/4’5 p14,510 Eroded edge of Fruitland {I Outcrop of Fruitland 14.410 00 Formation, concealed ; Formation d O by younger rocks \'\ 1 14,370 ) / ©14,480 jet ms c 7 ..... 014’2—40 s L & 3 8 I, 4 l /§‘O 1 } °o\ \ 1 I \ Aa od 1 v \ EXPLANATIGN SANDOVAL COUNTY \ , 14.700 Ca Cuba 8 , 7 | Sampled locality and _-_ : oo s uy >. s "moisture and ash »» free" Btu value of coal MC KINLEY COUNTY 5 0 5 10 15 2|O MILES 1 1 1 FicurE 3.-Map showing "moisture and ash free'" Btu values of coal samples from the Fruitland Formation. D94 of Fruitland coal, on an "as received" basis, is best in the northwest part of the San Juan basin, where most values exceed 12,000 Btu. In the rest of the basin most of the "as received" values are less than 12,000 Btu. CONCLUSIONS Figure 3 shows the "moisture and ash free" Btu values of the coal samples. In contrast to the "as re- ceived" values of figure 1, these values show a definite pattern, a regular increase from 13,460 in the south- west to 15,720 in the northeast. Zones characterized by about the same Btu values trend northwest across the basin. This direction nearly parallels the strand- lines of the Pictured Cliffs and Fruitland Formations ECONOMIC GEOLOGY and is at right angles to the northeastward withdrawal of the sea. Thus the oldest coal deposits, those in the southwest part of the basin, have the lowest Btu values on a "moisture and ash-free" basis. The highest "mois- ture and ash-free" Btu values are found in the young- est coals in the northeast part of the basin. What this pattern of Btu values reflects is open to conjecture. It does not represent a pattern in the moisture and ash content, for these are random. The pattern could be due to differences in depth of burial, different types of original vegetation, slowly changing climatic condi- tions in Late Cretaceous time, thermal gradients affect- ing the buried coals, or possibly other factors as yet unrecognized. GEOLOGICAL SURVEY RESEARCH 1964 GIANT SUBMARINE LANDSLIDES ON THE HAWAIIAN RIDGE By J. G. MOORE, Menlo Park, Calif. Abstract.-Topographic evidence indicates the presence of two large submarine landslides on the slope of the Hawaiian Ridge northeast of Oahu. One slide is more than 150 km long and moved on a slope with an overall gradient of about 2 de- grees. A concave escarpment marks the head of the slides, and flat-topped tilted blocky seamounts occur on the middle and lower parts. Several thousand square kilometers of irregular top- ography, quite distinct from surrounding regions, oc- curs northeast of the island of Oahu in Hawaii. The area is on the northeast slope of the Hawaiian Ridge, a volcanic ridge which extends 2,600 kilometers west- northwest from the island of Hawaii to Ocean Island. The irregular topography of the area is well shown on a U.S. Navy Oceanographic Office preliminary bathymetric map, part of which is reproduced on figure 1. The topography is characterized by elongate blocky seamounts with tilted relatively flat upper sur- faces, as shown in the geologic section (fig. 2). The topography and geologic setting of this area suggest that it represents the surface of two giant sub- marine landslides. The slides extend down the north- east slope of the Hawaiian Ridge and out on the adjacent ocean floor. They cross the axis of the Hawaiian Trench, an ocean deep flanking the ridge and presumably formed by downwarp of the crust due to the load of the volcanic pile which forms the ridge. Only the higher points on the surface of the lower end of the slides project above the level of the young sediments of the trench. TOPOGRAPHY The larger landslide, northeast of the island of Oahu, extends northeastward down the slope of the Hawaiian Ridge and is more than 160 km long and 50 km wide. The area of the slide is marked by a concave escarpment at its upper end and by a blocky welt in the middle and at the lower end. The blocky seamounts on the slide are commonly from 8 to 25 km long and 5 to 15 km wide. Almost all the seamounts are oriented with their long axes perpendicular to the long axis of the slide. Several of the blocks, includ- ing the largest one, are relatively flat on top, and this upper flat surface is tilted either toward or away from the Hawaiian Ridge. The majority of the blocks are tilted toward the ridge. A geologic section through the axis of this slide (figs. 1 and 2) shows the rugged blocky relief of its upper surface. The individual blocks are commonly bounded by steep slopes up to 2,000 meters in height. | The distance between crests of the blocky seamounts, or between the troughs of the intervening basins, is rather constant and averages about 15 km. Based on the surface topography, the geologic section was drawn to show the inferred subsurface structure of the slide (fig. 2). The sole of the slide is believed to be at a depth of about 6,000 m below sea level, and the slide averages 2,000 m in thickness. The gradient of the upper part of the landslide, extending down to a depth of about 3,000 m, is ap- proximately 6°. The average gradient of the surface of the slide from sea level to its lower end is about 2°. The sole of the slide is shown as being horizontal and at its lower end upward sloping, as is common with smaller landslides (Eckel, 1958, p. 24). The second landslide extends northward down the slope from the north side of the island of Molokai. This feature is also about 50 km wide and is more than 80 km long; however, both slides coalesce at their lower ends, and the overall length of the second one is not known with certainty. Very likely it is older than the first one, because the lower part of it appears to be more deeply buried by deep-sea sediment near the axis of the Hawaiian Trench. The upper end of this slide is also marked by a distinct concavity in the regional slope. The west- facing lateral scarp on the east side of this amphi- theater is typical of such lateral scarps on many U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D95-D98 D95 D96 MARINE GEOLOGY PACIFIC OCEAN\ \\ a 23° --- _ - A pial . Des \ Sp : e IJ RO) . Cg]? e fess. ""X s f ¥ N/ oan > Base from U.S. Navy Oceanographic Office preliminary sheet BCO4N 0 a o ho o t 0 B 0 50 MILES 1 * T I 20 40 60 80 KILOMETERS DEPTH CONTOURS IN FEET CONTOUR INTERVAL 600 FEET 8 - FiaurE 1.-Map of submarine topography adjacent to the islands of Oahu and Molokai. Inferred boundaries of landslides are shown by dotted lines. Geologic section A-A' is shown on figure 2. MOORE D97 A A' FEET METERS 07 SEA LEVEL f 3 6000 D I ly z @ 0 br > S 0 - - 0 2 T § & R l.: Till (Vashon) Esperance Sand Member C Vashon Drift Lawton Clay Member -__ __ Nonglacial deposit _ -- Tay Undifferentiated Pre-Vashon drift (not exposed) weathered clay SEA LEVEL: 0 C. i i i 1 1000 2000 FEET L I Fraur® 2.-Diagrammatic geologic section of deposits exposed in and above freeway excavations on Capitol Hill. color change from gray unweathered material up through grayish-green and olive-green weathered ma- terial; with exposure, the green color generally changes to brown or brownish green. The upward color change is accompanied by progressive eradication of bedding structures and increase of deformation. In the upper, most weathered part of the deposit, the bedding is almost indistinguishable, and the clay is highly de- formed and crossed by closely spaced, slickensided fractures of seemingly random orientation. The prin- cipal clay minerals identified in a sample of the un- weathered varved silt and clay were chlorite, illite, and montmorillonite, in order of decreasing abundance. These same clay minerals are present in the same order of abundance in all unweathered glaciolacustrine clay samples from Seattle that have been analyzed during the current investigation. In a sample from the lower part of the weathering profile, however, montmorillonite is as abundant as chlorite, illite is only a minor constituent, and some kaolinite was iden- tified. In a sample from higher in the profile, a mixed- layer clay composed chiefly of montmorillonite was the most abundant constituent, kaolinite and chlorite were next most abundant, and illite was not found. The alteration of clay minerals evident in the weathering profile, from chlorite and illite to mont- morillonite, montmorillonitic mixed-layer clay min- erals, and kaolinite, is apparently a common result of surficial weathering (Jackson and others, 1948; Harri- son and Murray, 1959). The profile exposed at Roanoke Street indicates that the montmorillonite-rich clays there were formed by weathering, and their stratigraphic position immediately underlying the un- weathered Lawton Clay Member indicates that the 1 Kaolinitic clay has been reported as the principal clay mineral in some clays interpreted as glacial or melt-water deposits in Seattle (McManus, 1963), but it has not been identified in our samples of unweathered glaciolacustrine clays. weathering occurred during the unnamed interglacia- tion that immediately preceded the Vashon Glaciation. Consequently, it is inferred that the mineralogically similar clays that directly underlie the Lawton Clay Member farther south along Capitol Hill are also weathering products formed during the same inter- glaciation. Green silt and clay strata similar to those ex- posed at Roanoke Street were exposed in several exca- vations farther south along the freeway. A sample of indistinctly varved strongly deformed green clay exposed near Nelson Place (fig. 1) consisted chiefly of a mixed-layer clay composed mostly of montmorillon- ite; kaolinite was the only other clay mineral identi- fied. Thus, composition as well as color and structure suggests that the clay sampled at Nelson Place had been strongly weathered. WEATHERED MATERIAL IN THE NONGLACIAL DEPOSIT No profile of weathering was seen in the nonglacial deposit, but the deposit contains interbeds of appar- ently strongly weathered material. Interbedding of weathered and unweathered material suggests that the nonglacial sediments were not weathered in place, but merely contain varying proportions of previously weathered clay. The weathered clay probably was derived from the slopes of adjacent hills of pre- Vashon drift by slopewash and creep. The weathered clay in the nonglacial deposit occurs mostly in layers of green to brown silty clay as much as 3 feet thick, and in layers of massive green to brown stony clay 2 to 3 feet thick. Most of these clays are similar to weathered glaciolacustrine clay in color, but locally the silty clay is brown because of abundant organic matter and shows no evidence of weathered material. A sample of one such brown clay, however, D102 300'- 200" Colluvial(?) stony clay 198 W-1305 Mammoth fossils SEA LEVEL NonglaciaJ deposit Weathered drift ENGINEERING GEOLOGY Till (Vashon) Esperance |_ Sand Member Lawton Clay Member Pre-Vashon drift a. 0 500 FEET L. hea Ficur® 3.-Diagrammatic section in the vicinity of the Fairview Avenue approach, showing postulated relation of hill of pre-Vashon drift to the nonglacial deposit, the stratigraphic position of wood samples W-1227 and W-1305, and the position of mammoth fossils. consisted almost entirely of a mixed-layer montmoril- lonitic clay mineral. The beds of stony clay are sandy, unsorted, un- stratified, and much more cohesive than other clays exposed along the freeway. The only structures noted in them were polygonal shrinkage cracks on exposed faces. One sample of stony clay consisted of a mixed- layer montmorillonitic clay, kaolinite, and chlorite, in decreasing order of abundance, suggesting a high proportion of weathered material. A sample of simi- lar clay from another locality, however, consisted of chlorite, montmorillonite, illite, and perhaps a little kaolinite, indicating a lower proportion of weathered material. ENGINEERING PROPERTIES Clay deposits with a high content of montmorillonite commonly have unusual properties of special impor- tance to engineers (Grim, 1962, p. 272; Lambe and Martin, 1957). The extreme properties sometimes as- sociated with montmorillonite are not expected from the weathered clays on Capitol Hill because the prin- cipal mineral is calcium montmorillonite, which usu- ally is less troublesome than sodium montmorillonite. However, both field and laboratory observations indi- cate that the weathered clays are significantly different in some engineering properties from the unweathered glacial clays that are far more common in the Seattle area. Relatively low shear strength, perhaps at high water content, is suggested because the weathered varved clays appear to be more susceptible to slope failure, and also to other deformation. For example, the strongly deformed, slickensided beds appear to be limited to the zone of weathered clays; it appears that the weathered clays were deformed selectively, be- tween undeformed unweathered clays, perhaps during loading by sediments or ice during Vashon time. Fur- thermore, potentially higher swell pressures in the weathered clays were indicated by preliminary swell- index (Lambe, 1960) and confined swell-pressure tests of remolded samples, which were made on 4 samples of weathered glacial clay, 2 samples from nonglacial beds containing weathered material, and 8 samples of unweathered glacial clay. Although these tests are complicated by factors that are unknown or are diffi- cult to control, the pressures measured for the weath- ered clay samples were consistently higher, averaging about twice as high as those for unweathered clay samples of comparable grain size. The principal conclusion of this preliminary work is that these green to brown clays should be recognized as different from the common gray unweathered clays of the Seattle area, and, until proved otherwise, re- garded as possibly unstable. Their mineralogy should be determined and their properties investigated to determine whether or not they will significantly affect engineering projects. Not all laboratory tests indicate that they will act differently from unweathered clays. Although measured swell pressures were higher for weathered clay samples, neither Atterberg limits nor activity values of the same samples were consistently higher. Besides laboratory tests, investigations should particularly include evaluation of the behavior of these green to brown clays when disturbed by con- struction activity; the properties of montmorillonite- rich clays may change markedly with changes of water content or chemical environment. DISTRIBUTION OF THE WEATHERED ZONE For clarity, the weathered glaciolacustrine clay has been described separately from the weathered material derived from drift and incorporated in the nonglacial deposit, yet the two deposits are commonly superposed along the freeway. For most engineering purposes, they can be considered as a single unit, because of their MULLINEAUX, NICHOLS, AND SPEIRER proximity and apparent similarity. The entire zone of weathered clay near Roanoke Street lies between altitudes of about 145 and 120 feet (fig. 2). It thick- ens as it decreases in altitude to the south, and nowhere else has the base of the zone been seen. South of Roy Street, only one small outcrop of weathered clay was seen, but exploratory drilling for the freeway indicates that the weathered clay may continue at least half a mile farther south (D. E. Wegner, Washington State Highway Department, oral communication, 1963). The weathered zone appears to lie along the slope of an older hill that has been buried by younger de- posits. The shape of the older hill cannot be deter- mined at present, but it appears likely that the south- ward decrease in altitude of the exposed part of the zone results from the freeway alinement crossing the west-facing slope of the old hill at a slight angle. Unfortunately, the distribution of weathered clays elsewhere in Seattle cannot be accurately predicted, for little is known about the weathered clay zone ex- cept on the west side of Capitol Hill. The problem is complicated because: (1) the topography during the unnamed interglaciation, and thus the shape and loca- tion of the zone as originally developed, is not well known; (2) erosion during and after weathering may have removed the weathered material in many places; and (3) some nonglacial sediments deposited in the Seattle area during the unnamed interglaciation do not contain abundant weathered clay. The fact that the zone has not been recognized previously suggests that it is not widespread as a well-developed zone in the city. Nevertheless, weathered clays should be anticipated in parts of the city that are underlain by older drift or by nonglacial deposits that lie near hills of older drift. Furthermore, it seems likely that the weathered clays will be best preserved where they # D103 have been buried and protected by the Lawton Clay Member, as along Capitol Hill. The most important locality in which the zone of weathered clays might be encountered is downtown Seattle. Nonglacial deposits probably underlie a large part of the downtown district, where they are overlain by the Lawton Clay Member; older drift makes up much of the adjacent hills to the northeast (Capitol Hill) and to the south (south end of First Hill and Beacon Hill). Green clay associated with organic material dated as about 20,000 years old has been found in one excavation in downtown Seattle, at an altitude of about 125 feet (H. H. Waldron, oral com- munication, 1964). Thus the weathered clay zone probably is present there. However, not enough infor- mation is available now to determine whether or not the weathered zone is extensive or well developed in the downtown district. REFERENCES Grim, R. E., 1962, Applied clay mineralogy: New York, Mc- Graw-Hill, 422 p. Harrison, J. L., and Murray, H. H., 1959, Clay mineral sta- bility and formation during weathering, in Swineford, A., ed., Clays and clay minerals, Sixth National Conference on clays and clay minerals, Proc.: Internat. Ser. Mons. Earth Sci., v. 2, p. 144-153. Jackson, M. L., Tyler, S. A., Willis, A. L., Bourbeau, G. A., and Pennington, R. P., 1948, Weathering sequence of clay- size minerals in soils and sediments, I: Jour. Phys. and Colloid Chemistry, v. 52, no. 7, p. 1237-1260. Lambe, T. W., 1960, The character and identification of ex- pansive soils: Federal Housing Administration Tech. Studies Rept., FHA-7OL. Lambe, T. W., and Martin, R. T., 1957, Composition and engi- neering properties of soil, V: Highway Research Board, 36th ann. mtg., Proc., p. 693-702. _ McManus, D. A., 1963, Postglacial sediments in Union Bay, Lake Washington, Seattle, Washington: Northwest Sci., v. 37, no. 2, p. 61-78. GEOLOGICAL SURVEY RESEARCH 1964 THREE PRE-BULL LAKE TILLS IN THE WIND RIVER MOUNTAINS, WYOMING- A REINTERPRETATION By GERALD M. RICHMOND, Denver, Colo. Abstract.-Detailed mapping at Bull Lake shows that the Dinwoody Lake Till is in fact the lower till of the Bull Lake Glaciation. The name Dinwoody Lake Till therefore is aban- doned. Three pre-Bull Lake tills successively underlying the lower till of the Bull Lake Glaciation are: Sacagawea Ridge Till, Cedar Ridge Till, and a newly discovered till, here named the Washakie Point Till. In a recent paper (Richmond, 1962) the author de- scribed a stratigraphic section at Bull Lake (fig. 1), on the northeast flank of the Wind River Mountains, Wyo., in which three tills and partly preserved inter- vening buried soils underlie undoubted till of the Bull Lake Glaciation. The Bull Lake Glaciation is next older than the Pinedale Glaciation, the last major glaciation of the region. The Bull Lake Glaciation was defined from a sequence of broad mature end moraines that lie just beyond the rough bouldery end moraines of the Pine- dale Glaciation at Bull Lake (Blackwelder, 1915). The end moraines of the Bull Lake Glaciation have been interpreted as representing at least two and pos- sibly three major advances of the ice. They form two and locally three groups; outwash channels extend from younger groups through older groups. Down- stream from the moraines, the outwash deposits rest on two and locally three sets of terraces. Where outwash deposits of the two older groups are super- posed, they are commonly separated by a mature zonal soil so like the interglacial soil separating youngest Bull Lake and oldest Pinedale deposits that a considerable recession of the ice, if not deglaciation, is indicated. No soil has yet been found between deposits of the middle and younger groups at Bull Lake. Currently, the oldest group of moraines define the early stade of Bull Lake Glaciation, and the middle and youngest groups together define the late stade. The stratigraphic section described in 1962 occurs in the precipitous bluff on the north side of Bull Lake, in the center of SW! see. 28, T. 3 N., R. 3 W. (fig. 2). The three tills beneath undoubted Bull Lake Till at the top of the section were named, from oldest to youngest: Cedar Ridge Till, Sacagawea Ridge Till, and Dinwoody Lake Till. All were considered of pre- Bull Lake age because they differ in composition from the undoubted Bull Lake Till above, and because the Cca (lime enriched) horizons of partly preserved pedocal soils on the lower two tills are intensely im- pregnated with calcium carbonate, a characteristic common to pre-Bull Lake tills at lower altitudes in this region. Further study, detailed mapping, and R. 5 W. R. 4 W. \< Dinwoody Lake a2 a - y Upper Dinwoody Lake P* Sad ICJNIM ( $4 m A \% [: C ~~ Bull Lake & -- -|, \_ t s Kay-c a \‘ 109° < 0 5 MILES I d FigurE 1.-Sketch map showing location of Bull Lake, on the northeast side of the Wind River Mountains, Wyo., and location of area shown on figure 2 (cross- hatched). U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D104-D109 D104 RICHMOND discovery of additional exposures of buried soils sepa- rating the tills have shown that the youngest till, the Dinwoody Lake Till, can be traced into, and actually forms the end moraine of the early stade of Bull Lake Glaciation. In addition, a previously unrecognized till and associated thick weathered zone were found beneath the Cedar Ridge Till. A revised interpreta- tion and correlation of the deposits are therefore in order. The undoubted Bull Lake Till at the top of the sec- tion in the bluff is a compact brown to light-brown stony silty sand, less pink than the underlying Din- woody Lake Till. It forms two large mature end moraines that extend north from the rim of the bluff and represent the late stade of Bull Lake Glaciation (fig. 2). The Dinwoody Lake Till is also a compact stony silty sand, but has a distinctly pinkish hue imparted by silt derived from Mesozoic red rocks. It is con- sidered to represent the early stade of Bull Lake Glaciation for four reasons: (1) The till can be traced westward from beneath the undoubted Bull Lake Till to the top of the bluff where it forms a large end moraine previously identi- fied as that of the late stade of Bull Lake Glaciation. The moraine extends northward from the bluff rim outside moraines of the late stade. (2) The moraine formed by the Dinwoody Lake Till is similar in form and surface characteristics to moraines of the Bull Lake Glaciation. (3) A buried soil found on the Dinwoody Lake Till beneath the undoubted Bull Lake Till is similar to that on the undoubted Bull Lake Till and dissimilar to soils on pre-Dinwoody Lake tills. The Cea horizon of this soil is thinner and has a much lesser concentra- tion of calcium carbonate than the thick intensely calicified soils on the older tills. (4) Outwash gravel from the end moraine formed by the Dinwoody Lake Till, extends to the highest of three gravel-capped terraces, 80 to 200 feet above the Wind River, on all of which the soil is very similar to soils on moraines of the Bull Lake Glaciation. The stratigraphic, physiographic, and pedologic fea- tures of the Dinwoody Lake Till thus are more closely related to the Bull Lake Glaciation than to older glaciations. The terms "Dinwoody Lake Till" and "Dinwoody Lake Glaciation" are therefore abandoned in favor of the informal terms "lower till" and "early stade" of Bull Lake Glaciation. In the stratigraphic section described in 1962 the D105 "Dinwoody Lake Till", now the lower till of the Bull Lake Glaciation, is underlain successively by the Sacagawea Ridge Till and the Cedar Ridge Till. These tills are lithologically distinct; the Sacagawea Ridge Till is buff and contains sedimentary and crys- talline rocks in about equal proportions. The Cedar Ridge Till is gray and contains mainly crystalline rocks. More complete buried soil profiles than those described on these tills in 1962 have subsequently been found and are presented below. Their thick massive Cea horizons support the interpretation that the tills represent separate glaciations, each followed by a distinct interglaciation. Discovery of an additional till and an associated very strongly developed soil beneath deposits of the Cedar Ridge Glaciation define still another, and earlier, glacial-interglacial cycle. The till is here named the Washakie Point Till for Washakie Point, an abrupt promontory along Cedar Ridge on the north side of Bull Lake (center, NEY sec. 32, T. 3 N., R. 3 W.). The point is not named on the 1952 edition of the Bull Lake West quadrangle, but its location on Cedar Ridge is marked by two large adjacent elongate glaciated boulders in upright position. The type locality of the Washakie Point Till is in the bluff of Cedar Ridge below a small promontory 2,000 feet east of Washakie Point (SEZ SEL sec. 29, T. 3 N., R. 3 W.) and about 2,000 feet west of the section described in 1962. The Washakie Point Till lies disconformably beneath varved lake silts sub- jacent to the Cedar Ridge Till and overlies lake beds that rest unconformably on a conglomerate of Ter- tiary age. It has a thick pedocal soil developed on it and is characterized by abundant material from the conglomerate. The following stratigraphic section measured in the bluff at the type locality includes not only the Wash- akie Point Till but the entire column of overlying glacial deposits and soils to the top of the upper till of the Bull Lake Glaciation. Section in escarpment of Cedar Ridge on the north side of Bull Lake, 2,000 feet northeast of Washakie Point (SE SE} sec. 29, T. 3 N., R. 3 W.). Measured by G. M. Richmond and J. F. Murphy. Post-Bull Lake soil: ”$9,275” B horizon (partly stripped); brown (7.5YR 4/4), loose stony silty fine sand .________._.__._____. 0. 5-0. 8 Cea horizon; light-brown (7.5YR 6/4) stony silty sand. Calcareous coatings on cobbles and boulders; matrix slightly sticky, slightly plastic, firm, hard seiko ancl 1-2 D106 QUATERNARY GEOLOGY AND GLACIOLOGY 109°07 "30" R.3 W. 0 1 MILE | l t 1 1 Fiaur® 2.-Quaternary geology of part of the Bull Lake area, Bull Lake East and Bull Lake West quadrangles, Wind River Mountains, Wyo. Recent Pleistocene RICHMOND D107 EXPLANATION Section in escarpment of Cedar Ridge on the north side of Bull k Lake, 2,000 feet northeast of Washakie Point (SHY,SHY Qa sec. 29, T. 3 N., R. 3 W). Measured by G. M. Richmond and J. F. Murphy-Continued Alluvium Thickness a Bull Lake Till: (feet) MORAINE OoUTWwaASH . pEposits GRAVEL Upper till, light-brown (7.5YR 4/4-6/4); locally light olive brown (2.5YR 5/4); compact friable silty sand and unsorted, unsized subangular to angular pebbles to boulders. Boulders numer- Qpm |Qpms Qpgm ous. Most stones of fresh crystalline rock but Qpmf some of sedimentary rock, mostly limestone. A few stones decomposed ; a few soled, faceted, or opt ... /as dunham f aln able min mtn gn a 46 Pinedale Till Qpm and Qpmf-Qpmt, middle till. Qpl, lower till Qbi Qbu Qbgu Qpmt Middle gravel Pinedale Glaciation Disconformity Intra-Bull Lake soil: B horizon; light-reddish-brown (2.5 6/4 stony silty sand. Weak angular blocky structure; nonsticky, nonpiastic, firm, fria- ple: - cece a etn nes sl a a alue a an to are' ua Be . 1. 8 Cea horizon, pink (7.5YR 7/4); stony silty sand; weak platy structure; moderately impregnated with calcium carbonate; slight- ly sticky, slightly plastic, firm, friable... 2 Lower till; light-brown (7.5YR 6/4) to light-yel- lowish-brown (10YR 6/4) compact massive stony silty sand; very bouldery. Matrix has distinctive pinkish hue owing to silt derived from Mesozoic red beds. A few stones soled, faceted, or striated. About half of rock material is crystalline, about half sedimentary. Lenses of Qc pinkish bedded silt throughout; local layers of angular gravel and silty sand at base_______. 84 Qbo Qbi Upper gravel QUATERNARY Bull Lake Till Qbi and Qbo, upper till Qbi, lower till (formerly Dinwoody Lake Till) Bull Lake Glaciation Qs Sacagawea Ridge Sacagawea Ridge Till Cedar Ridge Glaciation Glaciation - Glaciation Cedar Ridge Till i edar Ridge Ti Disconformity Buried soil developed on colluvium: B horizon (partly stripped); light-brown (7.5 YR 6/4) to brown (7.5YR 5/4) oxidized partly leached pebbly sandy silt; coarse blocky struc- ture; slightly sticky, slightly plastic, firm, crumbly . . . ..I II-III Pulla neue th om 1. 5 Qw Washakie Point Washakie Point Till J Tog Conglomerate 1 Location of section described in 1962 2 Location of section described in this paper FiaurE 2.-Explanation. 742-652 O-64--8 TERTIARY Cea horizon; white (10YR 8/2) fine granular silt with local pebbles; coarse platy structure; sticky, plastic, firm, hard. Less calcareous and more friable in lower Disconformity Deposits of Sacagawea Ridge Glaciation: Lake beds: Varved silt and clay, buff:.............L... Fine sand and pebbles, loose Varved silt and clay, buff...._.___.__L_L_L_. Lake silt, white, fine-grained, well-sorted.____. 5. 5 o a D108 Section in escarpment of Cedar Ridge on the north side of Bull Lake, 2,000 feet northeast of Washakie Point (SHY, SHY sec. 29, T. 3 N., R. 8 W). Measured by G. M. Richmond and J. F. Murphy-Continued ia C Deposits of Sacagawea Ridge Glaciation-Continued Sacagawea Ridge Till, very pale brown (10YR 7/4), massive, calcareous, nonsorted, unsized. Sandy silt matrix is nonplastic, nonstocky, firm, hard, very compact; preserves casts of stones. About 50 percent of cobbles are of Paleozoic rock, mainly buff limestone and dolomite; very little Flathead Sandstone; about 50 percent are of crystalline rock. Practically no Mesozoic rock. Striated cobbles, mostly of limestone. Fewer boulders than in tills above ar below; most are of crystalline rock. Deposit thickens to west_____. Disconformity Buried soil developed on Cedar Ridge Till: B horizon (mostly stripped); yellowish-brown (10YR 5/4) to pale-brown (10YR 6/3) compact stony silty sand. Stones mostly crystalline; many rotted. - Wavy irregular bands and zones. Rotted biotite-gneiss cobbles smeared out as streaks. Matrix partly leached, nonsticky, nonplastic, firm, hard. - Gradational boundary __ Cea horizon; white (7.5YR 8/2) compact coarse to fine sandy silt and stones; strongly impregnated with calcium carbonate; streaky local material like B horizon along joints and as irregular streaks. - Matrix slightly sticky, slightly plastic, firm, hard. Stones mostly crystalline, several rotted; gradational lower boundary .___.______. Cedar Ridge Till; light-gray (2.5YR 7/2) to brownish- gray (10YR 6/2) stony silty sand; calcareous, non- sticky, nonplastic, loose to compact. Nonsorted, unsized. Cobbles and boulders subangular to sub- round, some soled and faceted, a very few striated, most are of crystalline rock-granite, biotite gneiss; sharp lower boundary. 20 Lake beds of Cedar Ridge Glaciation: Sand and fine crystalline gravel, light-gray (2.5Y R 0. 5-1. 0 2. 5-3 7/2); gradational lower boundary____-________. 5 Sand, gray, clean, medium- to fine-grained, loose. Sharp lower 15 Fine-grained sand and silt, light-gray (2.5YR 7/2); in 2- to 12-in. layers, not true varves. Grada- tionallower boundary....................1nl... 6 Varved silt and clay, pale-yellow (2.5Y R 7/3), thin- bedded, well-sorted, nonsticky, plastic, smooth. Lenses of gravel and sand in lower part_______. 12 Disconformity Soil developed on Washakie Point Till: B horizon, light-brown (7.5YR 6/4), bouldery; many broken and deeply weathered rocks, mostly crystalline, some of Paleozoic rock, many derived from conglomerate of Tertiary age. Silty sand matrix is compact, partly leached, slightly sticky, slightly plastic, firm, hard; coarse angular blocky structure. Gradational lower boundary with streaks extending into zone QUATERNARY GEOLOGY AND GLACIOLOGY Section in escarpment of Cedar Ridge on the north side of Bull Lake, 2,000 feet northeast of Washakie Point (SEHVY,SHY sec. 29, T. 3 N., R. 3 W). Measured by G. M. Richmond and J. F. Murphy-Continued Thickness (feet) Soil developed on Washakie Till-Continued Cea horizon; white (2.5YR 8/2) to pale-brown (10YR 6/3) bouldery till, as above, but strongly impregnated with calcium carbonate; boulders coated with carbonate. Till thickens to 11 feet immediately westward where fresh material beneath the soil has greenish cast (2.5YR 7/2) owing to its high content of material derived from conglomerate of Tertiary age- ___. Cea horizon on lake beds; white (2.5YR 8/2) stony silty sand,; slightly sticky, slightly plastic, firm, hard. Carbonate concentrated along joints and permeable 2 Deposits of Washakie Point Glaciation: Lake beds: Silt, pale brown (10Y R 6/2), massive and thin- bedded, Sand, pebbly, loose, clean, fine-grained. Rusty zone at top. Pebbles, angular to subangular, mostly of crystalline rock; some pebbles of Paleozoic rock and some derived from conglomerate of Tertiary age.. Silt, pale-brown (10YR 6/3), massive to banded; gravelly at base.........._....._ 0 4-11 5. 5 8. 4 Total thickness of Pleistocene deposits... 254 Angular unconformity Conglomerate of Tertiary age: Boulders, cobbles, and pebbles, rounded to sub- rounded; all of crystalline rock in arkosic sandy matrix. Material stained brownish to greenish; many stones deeply 150-200 The Washakie Point Till and underlying associated deposits extend in the wall of the bluff beneath the Cedar Ridge Till about 1,500 feet to the west and 1,000 feet to the east of the type section. Similar deposits occur beneath the Cedar Ridge Till in the bluff of a morainal reentrant in see. 35, T. 3 N., R. 4 W., north of the west end of Bull Lake. There, the Washakie Point Till contains many huge blocks of Bighorn Dolomite and is separated from the Cedar Ridge Till by crudely stratified colluvium, derived largely from red Triassic rocks that form the canyon wall. In my 1962 report, the "Dinwoody Lake," Sacagawea and Cedar Ridge Tills were correlated with a sequence of outwash terraces along the Wind River on the basis of extensions of the terrace deposits to moraines and deposits of till on the south side of Bull Lake. There, however, the moraine identified as "Dinwoody Lake" is in fact of pre-Bull Lake age, and is actually the equivalent of the Sacagawea Ridge Till at its type exposure. Similarly, tills on the south side of the lake and terrace deposits correlated in 1962 as Sacagawea Ridge and Cedar Ridge are here correlated with the RICHMOND type exposures of the Cedar Ridge and Washakie Point Tills respectively. This revised correlation is tabulated as follows: Terrace height, in feet, above Wind River near Glaciation or stade Bull Lake Pinedale 40 sai late 50 and 100 Bull Lake Glaciation {early 200 Sacagawea Ridge __ 380 and 500 Cedar Ridge Olaciation..........____...._. 660 Washakie Point 760 A corresponding revision in regional correlation suggests that the respective counterparts of the Washakie Point, Cedar Ridge, and Sacagawea Ridge Tills are the three pre-Bull Lake or "pre-Wisconsin' tills of the La Sal Mountains and Glacier National Park (Richmond, 1957, 1960, 1961), the Rocky Flats Alluvium, Verdos Alluvium, and Slocum Alluvium of the Denver basin (Scott, 1960, 1963), and the Nebraskan, Kansan, and Illinoian Tills of the mid- continent region. % D109 REFERENCES Blackwelder, Eliot, 1915, Post-Cretaceous history of the moun- tains of central western Wyoming: Jour. Geology, v. 23, p. 97-117, 193-217, 307-340. Richmond, G. M., 1957, Three pre-Wisconsin glacial stages in the Rocky Mountain region: Geol. Soc. America Bull., v. 68, p. 239-262. 1960, Correlation of alpine and continental glacial de- posits of Glacier National Park and adjacent High Plains, Montana: Art 98 in U.S. Geol. Survey Prof. Paper 400-B, p. B223-B224. 1961, Quaternary stratigraphy of the La Sal Moun- tains, southeast Utah: U.S. Geol. Survey Prof. Paper 324, 135 p. 1962, Three pre-Bull Lake tills in the Wind River Mountains, Wyoming: Art. 159 in U.S. Geological Survey Prof. Paper 450-D, p. D132-D136. Scott, G. R., 1960, Subdivision of the Quaternary alluvium east of the Front Range near Denver, Colorado: Geol. Soc. America Bull., v. 71, p. 1541-1544. 1963, Quaternary geology and geomorphic history of the Kassler quadrangle, Colorado: U.S. Geol. Survey Prof. Paper 421-A, 70 p. GEOLOGICAL SURVEY RESEARCH 1964 POST-HYPSITHERMAL GLACIER ADVANCES AT MOUNT RAINIER, WASHINGTON By DWIGHT R. CRANDELL and ROBERT D. MILLER, Denver, Colo. Abstract.-Presence or absence of distinctive dated layers of volcanic ash on moraines, in addition to ring counts of trees on moraines, provides chronologic evidence of a rebirth or reexpansion of glaciers on Mount Rainier between 3,500 and 2,000 years ago, and again at some time prior to 750 years ago. The two glacial episodes are here named the Burroughs Mountain Stade (older) and Garda Stade (younger) of the Winthrop Creek Glaciation. The glaciers of Mount Rainier, Wash., have long been of interest because of their size, relative accessi- bility, and economic importance in providing melt water used for hydroelectric power. At times during the recent geologic past these glaciers have been sub- stantially smaller than now, and at other times far larger. During part of the Fraser Glaciation, which lasted from about 25,000 to 10,000 years ago, ice and snowfields mantled the slopes of Mount Rainier vol- cano above an altitude of about 5,000 feet. Alpine glaciers fed by this source and by ice from cirques in the Cascade Range extended to distances of 15 to 40 miles down valleys that head on the volcano. This glaciation was followed by a period of relative warmth and dryness, the "hypsithermal interval," when glaciers on the volcano were smaller than now, and when many probably disappeared altogether (Matthes, 1942). Following this period of maximum warmth and dryness, a resumption of somewhat cooler and moister conditions permitted rebirth and reexpansion of glaciers within the last few millennia. The purpose of this paper is to describe evidence of two post-hypsithermal episodes of glacier advance at Mount Rainier and to name these episodes. The paper is based on fieldwork undertaken as part of a broader program of mapping the surficial deposits of Mount Rainier National Park. Only the moraines on the north, east, and south sides of Mount Rainier have been studied to date. The age of post-hypsithermal moraines at Mount Rainier has been determined by identification of sev- eral ash layers that overlie the moraines, and deter- mination of the age of the oldest trees that grow on the moraines. The pyroclastic deposits that are most helpful in limiting the age of the moraines are layers called W, C, and Y by Crandell and others (1962), all of which have been deposited within the last 3,500 years (table 1). Ash layer W, the youngest, is prob- TaBu® 1.-Age and source of five distinctive layers of volcanic ash on the flanks of Mount Rainier [Modified after Crandell and others, 1962] Radiocarbon ages and sample numbers ' of interbedded organic matter (years) Pyroclastic ayer Source 290 +200 (W-1120). 320 + 200 (W-1119). 1,500 +200 (W-1397). 2,040 +200 (W-1393). 2,340 + 200 (W-1396). 2,460 +200 (W-1394). 2,550 +200 (W-930). 2.980 £250 (W-1118). 3,500 +250 (W-1115). 4,000 £250 (W-1116). 8,750 +280 (W-950). Mount St. Helens__-_. Mount Rainier________ Mount St. Helens. ___. Mount Mazama___-_- Mount Rainier_______. 1 Radiocarbon determination by U.S. Geological Survey Radiocarbon Laboratory, Washington, D.C. 2 At least 400 years old, on the basis of tree-ring counts. 3 Resulted from an eruption 6,500 years ago of Mount Mazama at present site of Crater Lake, Oreg. ably between 400 and 500 years old. Organic matter above and below the ash layer yielded radiocarbon ages of about 300+200 years, indicating that an age of less than 500 years is likely. The layer probably U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D110-D114 D110 CRANDELL AND MILLER is more than 400 years old, however, because the ash is not present on either a lateral moraine of Emmons Glacier or a terminal moraine of South Tahoma Glacier, both more than 400 years old as determined by tree-ring counts. The age of the oldest trees that grow on a moraine provides a minimum age for the formation of the moraine (Sigafoos and Hendricks, 1961). However, several factors tend to make even the oldest trees ex- amined substantially younger than formation of the moraine on which they grow. These factors are the possible lapse of time between stabilization of the moraine and germination of the first trees that sur- vived on it, the possibility that the oldest tree on the moraine is no longer living or was not sampled, and the possibility that many years of stunted growth early in the life of the tree are not recorded in a core taken a foot or two above the base of the trunk. The net result of these combined factors is that a moraine may be older by at least several decades than the trees on it that were sampled. While this difference is substantial in a consideration of moraines formed within the past hundred years, it becomes propor- tionately less in the case of moraines several centuries old. On the other hand, with increasing age of moraines, there is a decrease in the chances of sam- pling a tree that started to grow soon after formation of the moraine, because of the possibility that many of the oldest trees are no longer living. WINTHROP CREEK GLACIATION Two episodes of glacier advance within the last 3,500 years are included in the Winthrop Creek Glaciation, which is here named for Winthrop Creek on the northern side of Mount Rainier (fig. 1). Mo- raines along Winthrop Creek form the type section of the glaciation. The two episodes are separated in time by at least 1,000 years, and thus constitute two separate stades. The older stade, represented by a lateral moraine on the northwestern slope of Bur- roughs Mountain, its type section, is here named the Burroughs Mountain Stade. The younger stade is here named the Garda Stade for lateral and terminal moraines near Garda Falls, which is also designated as the type section. During the Winthrop Creek Glaciation, many cirques whose floors are at or above an altitude of 6,500 feet were occupied by glaciers. In contrast, cirques occupied by glaciers during the last Pleisto- cene glaciation have a lower limit of about 4,500 feet at Mount Rainier. According to Bender and Haines (1955) the snowline at Mount Rainier moved upward from about 5,900 feet in 1910 to nearly 7,600 feet in D111 1952. During the past decade, the firn line has gen- erally been at altitudes between 6,900 and 8,600 feet (Mark F. Meier, written communication, 1963). Burroughs Mountain Stade Densely forested and well-stabilized lateral moraines on both the east and west sides of Winthrop Glacier are overlain by, and hence older than, ash layers C and W. The moraines are younger than ash layer Y, which is absent from the moraines, but present on the valley wall just beyond the lateral moraine east of Winthrop Glacier. The crest of this lateral moraine is about 300 feet higher than the oldest adjacent lateral moraine of Garda age in the vicinity of the Wonderland Trail. A terminal moraine of Burroughs Mountain age was not recognized in front of Win- throp Glacier, but the terminal moraine of Garda age lies on an outwash terrace that is mantled with ash layer C and is, presumably, of Burroughs Moun- tain age. Moraines of Burroughs Mountain age have also been recognized along the east side of Carbon Glacier, near Fryingpan Glacier, and at a few other places (fig. 1). These moraines typically are only a few yards beyond the maximum extent of ice during the Garda Stade, and moraines of comparable age in most valleys and in most cirques may have been overridden by that ice. Based on the limiting dates of ash layers, the Bur- roughs Mountain Stade occurred between 3,500 and 2,000 years ago. It is noteworthy that a glacial ad- vance in the La Sal Mountains of eastern Utah (Rich- mond, 1962) and an advance of glaciers on the north- ern side of the Brooks Range in Alaska (Porter, 1964) are both thought to have occurred about 2,800 years ago. Garda Stade Drift of Garda age along the Wonderland Trail near Winthrop Glacier includes forested lateral mo- raines that probably were formed during the latter part of the 17th century and bare, unstable moraines formed within the last decade and still partly under- lain by stagnant ice. The terminal moraine of Garda age north of Winthrop Glacier has trees as old as 140 years growing on it, suggesting that it was formed in the early part of the 19th century. The oldest terminal moraine of Garda age yet recognized in Mount Rainier National Park lies in front of Cow- litz Glacier; it was formed some time before 1363 A.D. The oldest lateral moraine of Garda age yet recog- nized is adjacent to Carbon Glacier at Moraine Park. It bears trees that started to grow early in the 13th century, and its topographic position indicates that D112 QUATERNARY GEOLOGY AND GLACIOLOGY 121°50' 121°40' I N T Ela I,’ “3345,“ WASHINGTON \ \ 9. ®-Area of \\\ \\6 report k.... 4 Garda Falls & LW} y | z/ if) s j * & 5 l/ \\ 7 7 k } Cm 5 ( Cea < # \Jp aA [ XBL N § : s VE & \§\,\\ s) ) "I 3 e ne Sarvent 222 Lal 2 Coro , ' CZ E nR cA | ase (g Emm‘m Glaciers 3 3 S"" a & f ts { 46°50 ~< \\ ~ <3 Af Ny 2 a’f' pstN 10 MIP" Pyramid Glacier ord Williwakas Glacier Stevens Glacier 5090 0 5000 10 000 15 lCJOO FEET 1 1 1 Fiaur® 1.-Location map of glaciers on Mount Rainier. Heavy lines, maximum extent of glaciers during Garda Stade; light solid lines, portion of glacier margin surveyed in 1910-13 extending beyond presert area (stippled pattern) of glacier; heavy dotted lines, moraines of Burroughs Mountain Stade. CRANDELL AND MILLER Carbon Glacier was thicker at Moraine Park in the early part of the 13th century than it is today. Thus, the Garda Stade may have begun some time in the late 12th century or early 13th century. The episode of glacier expansion culminated in various valleys at different times ranging from the middle of the 14th century to the middle of the 19th century. Moraines of Garda age can be differentiated from those of Burroughs Mountain age by the absence of pumice layer C. Some of the oldest moraines of Garda age are mantled with ash layer W, but most are ash free. DESCRIPTION OF MORAINES OF SOME REPRESENTATIVE GLACIERS A terminal moraine of South Tahoma Glacier is at the intersection of Tahoma Creek Trail and Wonder- land Trail on the north side of Tahoma Creek. This moraine consists of a single narrow ridge of drift on which very large trees are growing, among which one, nearly 4 feet in diameter, started to grow some time before 1554 A.D. Ash layer W was not found on the moraine. Banked against the upvalley side of the ter- minal moraine is a younger moraine, on which trees as old as 110 years are growing. This younger mo- raine probably was formed shortly before 1850, and both moraines were formed during the Garda Stade. Apparent lack of moraines of Burroughs Mountain age may be due to the presence of a thick debris flow of post-Y, pre-W age on the floor and lower slopes of the Tahoma Creek valley. Stevens and Williwakas Glaciers once were lobes of the larger Paradise Glacier, but recent glacier shrinkage has destroyed both lobes. The part of Paradise Glacier that remains includes two small isolated remnants and a higher and larger icefield from which they are separated by a cliff. End mo- raines of Garda age formed by Paradise and Stevens Glaciers are both older and younger than ash layer W. The pre-W terminal moraine of Paradise Glacier is a single low ridge of drift; immediately behind it is ash-free drift and in front of it is a Pleistocene mo- raine covered by layers of old volcanic ash. At its maximum extent during the Garda Stade, Stevens Glacier formed two small tongues near its terminus. The western tongue extended into the head of the canyon of Stevens Creek, and the eastern tongue formed a low terminal moraine now forested and covered with ash layer W. Within a distance of about 1,500 feet north of this terminal moraine, there are at least 15 bare, arcuate ridges that mark suc- cessive stands of the receding Stevens Glacier; all of these moraines are younger than ash layer W. D113 The outermost terminal moraine formed by Cowlitz Glacier during the Garda Stade lies only a few hun- dred yards beyond the ice terminus of 1910-13. The moraine consists of a single, sharp-crested ridge, about 100 feet wide at the base, which is mantled with ash layer W. Trees as old as 590 years were found on the moraine in 1963; trees are only as old as 190 years on the next-younger, ash-free moraine, whose crest is less than 100 feet away. In front of the older moraine is drift of late Pleistocene age which is mantled with ash layers W, C, Y, and O; no moraine of Burroughs Mountain age was recognized. At its maximum extent during the Winthrop Creek Glaciation, Ohanapecosh Glacier was a large continu- ous body of ice, but its lower and upper parts are now separated by a cliff. A pre-W terminal moraine of Garda age is well preserved ; it is flanked on the down- valley side by drift of late Pleistocene age which is mantled with ash layers as old as layer R. The bulkiest terminal moraine of Garda age is that of Emmons Glacier, which is about 1,000 feet from the upstream side to the downstream toe. A tree that started to grow about 1700 A.D. was found on the downstream toe, and the topographic map of Mount Rainier National Park, surveyed in 1910-13, shows the front of Emmons Glacier in contact with the up- stream side of the moraine. Some of the bulk of this ter- minal moraine might be due to superposition of a Garda moraine on a preexisting terminal moraine of Bur- roughs Mountain age. The terminal moraine includes three distinct morainal ridges formed at ice fronts in about A.D. 1745, 1850, and 1895, respectively (Sigafoos and Hendricks, 1961). Thus, the moraine apparently was formed at the front of a glacier that was char- acterized by a slow but persistent recession, punctu- ated by occasional stillstands or slight readvances over a period of about 200 years. Segments of terminal moraine on both sides of the Carbon River valley record two successive stands of Carbon Glacier, the older in the early part of the 16th century and the younger near the end of the 18th century. Lateral moraines are particularly numerous at Moraine Park (altitude about 5,500 feet), located on the east side of the glacier about a mile upvalley from the present glacier terminus. Here at least 15 lateral-moraine segments range in age from less than 100 years to at least 750 years. The oldest dated mo- raine of Garda age bears trees that started to grow early in the 13th century, and is the oldest moraine thus far recognized from tree-ring counts. The ab- sence of a terminal moraine of comparable age may be attributed either to destruction by stream erosion on the valley floor of the Carbon River or to over- D114 riding by ice represented by the 16th century terminal moraine. A lateral moraine of Burroughs Mountain age lies outside the moraines of Garda age south of Moraine Park. CORRELATIONS BETWEEN GLACIERS DURING THE GARDA STADE In order to show possible correlations from valley to valley, moraines of Garda age are listed below (table 2) with a limiting date for formation of the moraine provided by the oldest trees growing on them. Taste 2.-Limiting dates of formation of moraines of Garda age at Mount Rainier [All dated trees are on end moraines except the oldest (1217), which is on a lateral moraine of Carbon Glacier. Year shown is the earliest known date of tree growth on moraine.) Year Moraine of- 1802. - ann sans calan anld Ohanapecosh Glacier. 1858 . 22 LLL Te an bave ae wire s adie a Van Trump Glacier. T85l. .n s ssl nn on enn iene iate South Tahoma Glacier. $850 12 Lo LLL LLL LL sp Emmons Glacier. sone Nisqually Glacier. 1835 . Os OD LuLu cs ad ste ia. Tahoma Glacier. GEA G ene n weds ans dele alas i Winthrop Glacter. $800 : 2 rss n nel noon dav ea ven ex Carbon Glacier. l luc Cowlitz Glacier. $ ADL: ..o olen ie pln oy cuba neu Emmons Glacier. 1700 > ea on n beni ial Emmons Glacier. 1605 1°. } c el ill po Tahoma Glacier. 1551; . ede 22 an ne ie nle aims South Tahoma Glacier. 1010. .. ru ll nage an a Carbon Glacier. JRL ALIA L s Le san Cowlitz Glacier. ) puo ve ivete a Cone a damit fon Carbon Glacier. ! Sigafoos and Hendricks (1961). QUATERNARY GEOLOGY AND GLACIOLOGY End moraines formed during the middle part of the 19th century have been recognized in front of six glaciers on Mount Rainier. Moraines of this age mark the maximum stand of Nisqually, Van Trump, and Ohanapecosh Glaciers during Winthrop Creek time. Older moraines seemingly do not fall into a con- sistent pattern from glacier to glacier. This may be a result of insufficient data, or may reflect different behavior patterns of various glaciers. REFERENCES Bender, V. R., and Haines, A. L., 1955, Forty-two years of recession of the Nisqually Glacier on Mount Rainier; Erdkunde, v. 9, p. 275-281. Crandell, D. R., Mullineaux, D. R., Miller, R. D., and Rubin, Meyer, 1962, Pyroclastic deposits of Recent age at Mount Rainier, Washington: Art. 138 in U.S. Geol. Survey Prof. Paper 450-D, p. D64-D68. Matthes, F. M., 1942, Report of committee on glaciers, 1941- 42: Am. Geophys. Union Trans., pt. 2, p. 374-392. Porter, S. C., 1964, Late Pleistocene glacial chronology of north-central Brooks Range, Alaska: Am. Jour. Sci., v. 262, p. 446-460. Richmond, G. M., 1962, Quaternary stratigraphy of the La Sal Mountains, Utah: U.S. Geol. Survey Prof. Paper 324, 135 p. Sigafoos, R. S., and Hendricks, E. L., 1961, Botanical evidence of the modern history of Nisqually Glacier, Washington: U.S. Geol. Survey Prof. Paper 387-A. GEOLOGICAL SURVEY RESEARCH 1964 OCCURRENCE OF DISSOLVED SOLIDS IN SURFACE WATERS IN THE UNITED STATES By W. B. LANGBEIN and D. R. DAWDY, Washington, D.C., Menlo Park, Calif. Abstract.-Records show that the load of dissolved solids carried by rivers increases directly with the amount of runoff only up to about 3 inches mean annual runoff. The load in- creases less rapidly in those rivers whose annual runoff ex- ceeds 3 inches, and it attains a generalized maximum of 150 tons per square mile per year in rivers having a runoff in excess of 10 inches. Dissolved load carried by rivers is commonly less than the suspended load, but the proportion increases with the humidity of the climate. In dry climates, less than 10 percent of the total load may be carried in solu- tion, whereas in humid climates the percentage may be 50 percent or more. The quantity of dissolved solids and the chemistry of a flowing stream are commonly considered to de- pend primarily on the types of rocks or soils through, or over, which the water has passed in reaching the stream, and on the length of time the water has been in contact with the rocks and soils However, it also is of interest to consider the effect of the quantity of water on the quantity of dissolved solids in surface waters. In order to study the countrywide variation in quantity of dissolved solids in surface waters, records of chemical quality of water at 168 stations where water was sampled regularly were abstracted from U.S. Geological Survey water-supply papers. The mean annual runoff, in inches, the mean annual dis- solved load, in tons, and the mean dissolved-solids concentration, in parts per million, at each station were listed. The annual dissolved load per unit of drainage of each stream was computed (annual runoff, in inches X concentration of dissolved solids, in parts per million X 0.072 = tons of dissolved solids per square mile per year). These data were then grouped by mean annual runoff, and median values for each group were determined for runoff, concentration of dissolved solids, and dissolved annual load. The results for concentration and annual load are shown in the accompanying table and are plotted on figure 1. Dissolved solids in surface waters of the United States Dissolved solids Range in mean Number of| Median annual runoff stations runoff (inches) in group (inches) Median Median annual concentration | load (tons per (ppm) sq mi per year) 0-0 25........... T 0. 2 720 10 ...... 10 . 855 950 25 0.51-1£.00........ 19 4A 630 33 £.01-1.950........ 15 1. 5 460 50 1:81-8.00........ 13 2. 8 460 T7 2.01=6.00........ 14 4. 7 360 123 12 6. 8 2835 115 $:01-11.0... ..:... 17 9. 7 140 99 $1.1-150..1...... 15 | 13.5 90 88 16.1-18.0......_. 15 | 16. 5 110 132 19.1-22.0........ 13 | 19. 6 100 140 22.1-205.0........ 9 | 22. 9 108 180 25.1-80.8.!:...... 9 | 29.7 57 136 168 It should be emphasized that the data in the table and on figure 1 apply only to the generalized varia- tion in concentration among streams with different rates of runoff. The data should not be used to pre- dict the concentration in any given stream. For dissolved load, the relation pictured is rather as one might hypothesize. With increased runoff the load increases until a point is reached at which the rate of dissolution becomes the controlling factor. Above this point, increased water is less and less effec- tive in the weathering process and the amount of total dissolved solids approaches a constant. These are the characteristics of the load curve shown by figure 1. Dissolved load increases directly with runoff, up to about 3 inches of runoff, with a slope of approxi- U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D115-D117 D115 D116 1000 ; - 1000 500 [- 200 |- 100 - 50 |- DISSOLVED LOAD, IN TONS PER SQUARE MILE PER YEAR 20 |- CONCENTRATION, IN PARTS PER MILLION 10 1 | i 1 | i 10 $1. 02 os ~ 10" '> 5 10 to . 40 MEAN ANNUAL RUNOFF, IN INCHES 1.-Variation of dissolved-solids concentration and dissolved load in surface waters, with annual runoff. mately unity. Beyond 3 inches of runoff, the dis- solved load increases less rapidly, attaining a maxi- mum of about 150 tons per sq mi per year. Conversely, for concentration of dissolved solids the evidence indicates a decrease in concentration with increase in runoff. The concentration ranges down- ward from an average of 800 parts per million in arid climates, to as little as 50 ppm in humid climates (fig. 1), where mean annual runoff exceeds 10 inches. In humid climates, concentration is inversely related to runoff, representing a straight dilution effect. All stations with less than 5 inches annual runoff are west of the Mississippi River, and most are from areas of widely varying climate. Part of the curva- ture of the graphs from these stations may be due to the fact that the major portion of the dissolved solids may originate in one part of a catchment area and the major part of the water in another, and that both are measured in a channel in the midst of a large non- contributing arid area where only water losses occur. This would reduce the runoff and the apparent load per unit area when computed over the entire area, so that neither statistic would have any simple mean- ing as computed. Even if a drainage area were com- posed of two regions, one of greater than 2.5 inches of runoff and the other of less than 2.5 inches, the resultant load would plot lower than the curve of figure 1, since the two regions would be on different sides of the break in the relation. Thus, if half the area had 0.2 inch and the other half had 20 inches of runoff, the combined area would have a runoff of 10.1 inches, and a load of 75 tons per sq mi per year rather than the 120 tons expected from the mean runoff. Tonnages of dissolved solids per square mile for major drainages in the United States are given by SEDIMENTATION 500 T T T T T to o 0 T 1 100 |-- SQUARE MILE PER YEAR on 0 T DISSOLVED LOAD, IN TONS PER 20 |- 0.1 0.2 0.5 1.0 2 5 10 20 40 RUNOFF, IN INCHES Fraur® 2.-Variation in dissolved load among major river basins in the United States. 1, North Atlantic slope basins. 2, South Atlantic slope basins. 3, Eastern Gulf of Mexico basins. 4, Mississippi River basin. 5, Western Gulf of Mexico basins. 6, Colorado River basin above Yuma, Ariz. 64, Colorado River basin above Grand Canyon. ?, Pacific slope basins in galifornia, and 8, Columbia River and North Pacific slope asins. Durum and others (1960). Their results, slightly modified and plotted on figure 2, define a graph with values somewhat lower than those of the correspond- ing graph for load shown on figure 1. The difference reflects in large part the effect of the nonlinear rela- tion between load and runoff described above. Inferences about the shape of the curves on figure 1 may be obtained from a consideration of Nernst's law, according to which, the rate of dissolution of rocks would be proportional to the saturation deficit, which in a general way is the same as evaporation. Thus a g-C ti-DA (——S > where L is dissolved load; D is the maximum rate of dissolution of a given kind of lithology per unit area; A, is area; S is the concentration at saturation; and C the concentration at time t. Considering a rock being dissolved by a flow of water at rate Q, when the rate of dissolution equals the rate of removal, then a and ~ ' where C, is the concentration of the influent water (rainfall) and the other terms are as before. The concentration decreases with the ratio Q/DA from a value S for Q=0 to C,, the concentration of rainfall as Q goes to infinity. LANGBEIN AND DAWDY Interpreting the ratio Q/A as the runoff in inches, r, and if C,=0, then C 8 < 1-+0.073r9/D Where concentrations are in parts per million, r is in inches of runoff per year, and D is in tons per sq mi per year. Values of S and D can be estimated from the data shown on figure 1. The maximum concentration is about 1,000 ppm, and the maximum annual load is 150 tons per sq mi per year. - These values are set equal to 8 and D, respectively. 1000 Thus, O~_—1+O.5r shown on figure 1. This analysis assumes that the rate of dissolution varies with the saturation deficit and assumes that ionic composition remains the same. - However, composition varies with concentration. As might be expected, is the equation of the graph river records show that the percentage of highly soluble , salts, called "lake constituents'" by Langbein (1961, p. 13), increases with the concentration. (See fig. 3.) T T T T £ E 100 |- A -A-A- S C a -z so- - w D 5 m 40 |- - 4 o o & 20 |- -I < 3 § § | 1 1 10 100 1000 10,000 100,000 CONCENTRATION, IN PARTS PER MILLION Figur® 3.-Variation of highly soluble "lake constituents" in rivers, with total concentration of dissolved solids. All quantities computed in parts per million. These comprise chiefly the sodium salts, magnesium sulfate and chloride, and calcium chloride. Comparison of data on dissolved load with those of suspended load of rivers at gaging stations where both kinds of information are collected indicates that the dissolved load is commonly less than the sus- pended load (fig. 4), and that the proportion carried in solution tends to vary with the climate. The dashed D117 [ T 1 100 T I l T T 5000 [- Data on susperided load X 7328 from Wolman and Miller y- ** *~* (1960, table 5) y- * ho o o ls] v o o 0 on o 0 PERCENTAGE OF TOTAL LOAD CARRIED IN SOLUTION ro o o T ~ 1 ro w o 0 I an o T Dissolved load (this paper) TONS PER SQUARE MILE, PER YEAR A i I 1 1 l i 1 0.5 1.0 2 5 10 20 50 100 10, A 9.1. 62 RUNOFF, IN INCHES Ficur®E 4.-Comparison between dissolved load, suspended load, and sediment yield of rivers. Solid-line curves refer to scale on left; dashed curve to scale on right. line on figure 4 is the ratio, in percent, between dis- solved load and total load (dissolved load plus sus- pended load). Also shown are data on this same ratio published by Wolman and Miller (1960, p. 63). Thus in dry climates, less than 10 percent of the total load may be carried in solution; in these regions the far greater part of the load consists of clastic sedi- ments. In humid climates the inhibiting effect of vegetation on erosion and the abundance of water for weathering and solution tend to increase the per- centage carried in solution. Thus, in humid regions, say where runoff exceeds 20 inches, 50 percent or more of the total load may be carried in solution, but gen- erally the amount of dissolved load remains below that carried in suspension. REFERENCES Durum, W. H., Heidel, S. G., and Tison, L. J., 1960, World- wide runoff of dissolved solids: Internat. Assoc. Sci. Hydrology, Comm. of Surface Waters, Pub. 51, p. 618-628. Langbein, W. B., 1961, Salinity and hydrology of closed lakes: U.S. Geol. Survey Prof. Paper 412, 20 p. Langbein, W. B., and Schumm, S. A., 1958, Yield of sediment in relation to mean annual precipitation: Am. Geophys. Union Trans., v. 89, no. 6. Wollman, M. G., and Miller, J. P., 1960, Magnitude and fre- quency of forces in geomorphic processes: Jour. Geology, v. 68, no. 1, p. 54-74. GEOLOGICAL SURVEY RESEARCH 1964 STATISTICAL PARAMETERS OF CAPE COD BEACH AND EOLIAN SANDS By JOHN SCHLEE, ELAZAR UCHUPI, and J. V. A. TRUMBULL, Woods Hole, Mass. Abstract.-Statistical parameters of size of 6 beach and 9 eolian sand samples, as determined by the sieving method and the settling-tube method, reveal no significant size differ- ence between sand of the 2 environments. With the excep- tion of skewness, values obtained by the two methods are similar. Plots of kurtosis versus skewness, standard deviation versus mean grain size, and skewness versus mean grain size show no parts of the fields restricted to a particular environ- ment. Size distribution of sediments has been used by many workers to infer something about the type of transporting medium and ultimately the environment of deposition. Behind this approach is the expecta- tion that transport by wind, ice, or water uniquely affects the sediment size distribution through selective transport of certain grain sizes. As a test of this ap- proach, a suite of beach and dune samples was col- lected from the outer arm of Cape Cod, Mass., and analyzed to determine whether sediments from the two environments could be distinguished by statistical parameters. J. A. Udden (1914) first noted the manner in which grain size is related to the transporting medium- wind or water. He related the genesis of the deposit to certain descriptive features of the grain-size histo- gram. Later workers refined this use of grain-size analysis through visual examination of the size-dis- tribution curve (Doeglas, 1946; van Andel and Postma, 1954) and through the use of statistical parameters that summarize the distribution (Folk and Ward, 1957; Friedman, 1961). Results of previous investigations have not been consistent. Harris (1957, 1959), Mason and Folk (1958), Friedman (1961), and Mabesoone (1963) have 1 Contribution No. 1408 from the Woods Hole Oceanographic Insti- tution. reported that they could distinguish between the two environments by statistical parameters. Mason and Folk (1958) stated that the best means of differentiat- ing between the two environments was by plotting skewness versus kurtosis, inasmuch as geologic proc- esses seem to have their greatest effects on the tails of the size distribution. Friedman (1961) found that a scatter plot of mean grain size against skewness re- sulted in a complete separation of the fields represent- ing dune and beach sands. Others, like Udden (1914) and more recently Shepard and Young (1961), found that statistical parameters are unreliable for distin- guishing beach from dune sands. Folk (1962), in a review of Shepard and Young's article, stated that their failure to find any grain-size difference between - their samples was because they used the settling tube for grain-size analysis of their samples rather than a set of calibrated sieves. Folk considered that the settling tube lacks the ability to detect the subtle dif- ferences in genetically important parts of the size distribution-the tails. PROCEDURE Six beach and nine dune samples were collected from the outer arm of Cape Cod (fig. 1). Beach sand was collected from the uppermost centimeter of sedi- ment in the swash zone and in the first berm. Eolian sand was collected from the lee and windward sides of active dunes and from small ripplelike accumula- tions in the flats behind the berm. Samples were washed, dried, and split for me- chanical analysis. Before sieving, screens were cali- brated by making 100 measurements of the mesh opening for each screen with a microscope and ocular micrometer. Results of screen calibration are shown in table 1. Maximum departure from the correct mesh opening was 0.05 phi units. A 15-gram split of each U.S. GEOL. SURVEY -PROF. PAPER 501-D, PAGES D118-D122 D118 SCHLEE, UCHUPI, AND TRUMBULL I Area of report a2°L. + CAPE COD BAY 5: q O O is C14, 15 § ' Yarmouth 5; & % 1 o 5 10 MILES Teed eh neden Aner acronis, 0 5 10 KILOMETERS beans s LLE OL, 1 Fiaur® 1.-Map showing sampled localities. Beach sand, open circles; eolian sand, dots. sample was sieved for 15 minutes on a Rotap shaker using 8-inch screens at 4-phi intervals. Fractions were weighed to the nearest milligram, and the results were plotted on probability paper. Clotted aggregates were not detected in finer fractions, though an exami- nation was made under the binocular microscope. Settling-tube analyses were made with a modified version of the Woods Hole rapid sediment analyzer (Zeigler and others, 1960). This analyzer measures pressure changes induced in a water column by sedi- ment settling through a measured distance. Samples weighing between 10 and 15 g were used. Settling D119 time was converted to equivalent phi size. On each record the 5, 16, 25, 50, 75, 84 and 95 percentiles were read. 1.-Results of screen calibration based on 100 measurements of the mesh of each screen Mean of Stated opening measured opening Difference ¢ (a $ ¢ ..o o. 98 624...... 3. 99 +. 01 TA erals ss a #D 8. 72 -. 08 5.00. 3. 46 -. 04 105.::.... 3.25 106.....}1 3. 24 -. Ol 120....... 3.00. 2. 97 -. 03 M9..:.... 270: 153...2.}L 2. T0 -. 05 2.100 - 182...-.... 2. 45 -. 05 10....... 2:20 2. 28 -. 02 200......; 2:00. 256....... 1. 96 -. 04 2 1.75 $08......_._ 1. 71 -. 04 1.80 ' 350....... 1. 48 -. 02 417.;..... 1:25 431....... 1.21 -. 04 500-...... 1.00 504....... . 97 -. 03 b50........ 70; D95... 74 -. O1 TZ10.i..... 50. 703....... . 51 +. Ol m40....... 20. S14....... . 28 +. 08 $,000....... 00 1,015..... -. 02 -. 02 ! -lo5 1,150 ___. >~.20 +. 05 1,410...... -. 50 1,8383..._._. -. 46 +. 04 1,080...... -.10 1,005..... -. 72 +. 03 2,000...... -1. 00 2,008..... -1. 00 . 00 2;080...... -1;25 2972... -1. 25 . 00 2,550...... -1,. 50 (2,787... -1. 48 +. 02 2,060...... -1.75 83,2901... -1. 72 +. 03 4,000.-._.... -2. 00 4,101..... -2. O1 -. Ol Previous workers have not used the same formulas to compute size parameters. Mason and Folk (1958) used formulas from an earlier report by Folk and Ward (1957) to summarize their analyses. Shepard and Young (1961) used formulas published by Inman (1952). Friedman (1961, table 1) used moment meas- ures to calculate his statistical parameters. In an effort to present our data in a form comparable with most other workers, Folk and Ward's formulas have been used. According to Shepard and Young (1961), the values obtained with these formulas differ only slightly from those obtained with Inman's. RESULTS Results of the grain-size analyses are shown in table 2 and on figures 2 to 4. Wind-deposited sand (average mean size 0.75 phi) appears to be slightly finer grained than the beach sand (average mean size 0.46 phi), although the values show a considerable overlap (fig. 2). In order to determine whether the difference in mean values is significant, Student "t" tests were made separately on the sieve and tube analyses. Values of "t" at 1.64 for sieve analyses and 1.33 for tube analy- ses are both less than 2.16 and hence there is no differ- ence at the 95-percent significance level (Hoel, 1954, p. 320) between the means of the samples from the beach and eolian environments. Settling-tube values D120 SEDIMENTATION 2.-Statistical parameters for grain-size distribution of Cape Cod sands Mean (¢) Standard deviation (¢) Skewness Kurtosis Sample No. Sieve Tube Sieve Tube Sieve Tube Sieve Tube Beach sand -0. 10 - 0. 37 0. 37 0. 36 -0. 27 0. 20 1.16 1.12 nene . 64 - 57 . 20 . 25 -. 13 . 31 1. 12 1. 00 ule . 57 . 55 +27 . 28 . 06 . 47 . 96 1. O7 O00. :.. a 2 e+ - ul as o ain a wie in inin mle i ie . 67 . 74 . 48 . 44 -. 06 . 29 1. 08 . 90 2.0 -.. s . 85 . 25 . 29 . 83 -. 33 . 38 1. 32 1.10 . 69 . 70 . 831 . 34 . O1 . 84 1. 05 . 93 . 46 . 41 . 31 . 88 -. 12 . 88 1.12 1. 12 RANGC. _ cc ele reuses -.01to. 69 |-.37t. 74 |. 20 to. 43 |. 25 to. 44 |-.83t. 06 |. 20 to. 47 |.96to1. 32 |. 90 to 1. 72 Eolian sand 4s 0. 29 0. 17 0. 31 0. 29 -0. 15 0. 25 1. 03 0. 85 C4. ... ceara al eee read a a aise . 50 . 45 . 81 . 83 -. 13 . 40 . 96 1. 03 CCS... ns . 69 . 62 . 36 . 42 -. 05 . 28 1. 03 1. 02 s . 65 . 44 : 97. . 42 -. 03 Gl 1:1! . 85 ans nes . 80 . 59 . 28 . 82 0 . 40 1. 25 1. 04 COI. _: cel ce dvi cot sabs mim in ad a . 97 . 91 . 46 AT -. 15 . 08 1. 15 1. 16 CCOH.... . Al- ec 1. 26 1. 37 27. . 87 20 . 19 1.10 . 81 .c: ted a walks . 88 . 81 . 85 . 40 -. 03 er 1: 17 . 93 CCI5... _. . T9 . 81 . 85 . 835 -. 05 . 30 1. 05 . 965 Mean. cre 160 . 69 . 34 +37 -. 04 27 1.10 . 96 RANGE: cl .29to 1. 26 |.17to1. 37 |. 27 to. 46 |. 29 to. 47 |-.15t. 20 |. 03 to. 40 |.96 to 1. 25 |. 81 to 1. 16 for mean grain size tend to be lower than the corre- sponding sieve measures, though the differences are minor. Sands from Mustang Island, Tex., studied by Mason and Folk (1958), are much finer grained and have much less variation in grain size than the Cape Cod sands. Mean grain size ranges from 2.65 to 3.00 phi for the samples from Mustang Island and -O0.31 to 1.37 phi for the samples from Cape Cod. Coarseness of grain size probably reflects the inclusion of glacial out wash and morainal material reworked from nearby deposits. The Cape Cod sands are also coarser than beach sands near Cadiz, Spain, studied by Mabesoone (1963). Standard deviation of Cape Cod sand from both en- vironments averages less than 0.35 phi, and hence by Folk and Ward's criterion the sand is well sorted. 0.50 T ~I T T T 0.50 ; ; ; ; 0.40 |- -| |- - 0.30 |- s{ {L- s 0.40 |- ¥ > 0.20 |- -| } - e < bu 0 M WA a a 80.10 o & a 9.30 |- =i 3 Fa x 0 r- FAL] - $ m Z < in -0.10|- sf "L. a 0.20 |- ~. K - -0.20 |- 4 |- - -9.30(- SE ~ 0.10 L B 1 I 1 i- 1 1 =0.40 "0° d40 oso 1.20 L60-0.40 0. 640 Oo%6- 1.30 1.60" | | 3 1 | | | | MEAN SIZE (¢) MEAN SIZE (¢) -6.40 .:0 " wo O80 1.20 1.60 0 ~ 640° 680. 1.20 1.60 A B MEAN SIZE (¢) MEAN SIZE (¢) A B Fiaur® 2.-Mean size versus standard deviation. A, sieve analysis; B, settling-tube analysis. enclosed by solid line; eolian sands, dots enclosed by dashed line. Beach sands, open circles Fraur® 3.-Mean size versus skewness. A, sieve analysis; B, settling-tube analysis. Beach sands, open circles enclosed by solid line; eolian sands, dots enclosed by dashed line. SCHLEE, UCHUPI, AND TRUMBULL D121 I I I 0.57 -| 0.87 oal 0.56 -| 0.56 = & o 0.55 £- o55 P - J 3 x < 0 0 a § 8 5; :0.04 Q- 0.54 a- 35 _ Mt Fa ® A - ¢ g oss % 0.53 te 3 x ® #: J | =p 953 - o -' % 2 0.51 *+ 3. ost g -l 8 P 0 0 0.50 =- 0.50 = 0.49 ->. 64g _ 0.48 1 0.48 | -0.40 -0.30 -0.20 -0.10 _ 0 0.10 . 0.20 -ws6e -g %0 o (6.10 0.30 skewness skEwnEss A B Fraur® 4.-Skewness versus kurtosis expressed as Kp. Beach sands, open circles enclosed by solid line; eolian sands, dots enclosed analysis. by dashed line. As with mean grain size, standard-deviation values from beach and eolian sands overlap almost com- pletely (fig. 2). Mean sorting values tend to be slightly lower in the beach sands, in contrast to the results of Mason and Folk (1958) and Shepard and Young (1961), who report that dune sands are better sorted. Student "t" tests for the sorting values reveal no significant differences at the 95-percent level be- tween the values of the two environments. Sieve and tube analyses of sand give similar results; mean sort- ing values differ by only 0.03 phi. Skewness values from the two environments show considerable overlap (fig. 3), and Student "t" tests again indicate that there is no significant difference at the 95-percent level (tsieve =0.74, ttupe =1.76; tos percent =2.16). This contrasts with the results of Mason and Folk (1958, p. 218), Friedman (1961, p. 517), and Mabesoone (1963, p. 38), who found that dune sands tend to be positively skewed and beach sands tend to be negatively skewed. Shepard and Young (1961, p. 200-201) analyzed size by settling tube, and their re- sults show a complete overlap of values from beach and eolian areas. However, almost all their values are negative, in contrast with the positive skewness obtained by settling-tube analysis in this study. As pointed out by Folk (1962, p. 146), some differences may result because Shepard and Young used a for- mula to estimate skewness that emphasizes the 95th and 5th percentiles with respect to the median, rather A, sieve analysis; B, settling-tube than comparing the 95th and 5th percentiles to the 84th and 16th percentiles as is done here. Though our skewness values of sands from the two environments overlap, sieve and settling-tube values do not. Sieve values are mostly negative, whereas those obtained by the settling-tube analysis are all positive. A plot of mean grain size versus skewness (fig. 3) shows a large degree of overlap for beach and eolian values. - This is in contrast to Friedman's results (1961, fig. 2), which show a nearly complete separation of fields representing beach and dune sands. A partial explanation of the difference may be due to his use of moment measures rather than percentile measures or the coarseness of the Cape Cod sands. As with the other parameters, a nearly complete overlap of beach and eolian kurtosis values occurs (fig.4). Student "t" tests reveal no significant differ- ence in mean kurtosis values at the 95-percent level. Settling-tube values broadly overlap those obtained by sieving, although the latter tend to be smaller. Kurtosis is one of those statistical measures for which the geologic significance has yet to be established. Folk and Ward (1957), Mason and Folk (1958), Shepard and Young (1961) and Friedman (1961) have had little or no success in using it to distinguish beach from dune sand. Folk and Ward (1957, p. 15) devised a normal- ized function: e TT With kurtosis values computed in this manner, Mason D122 and Folk (1958, fig. 4) could distinguish eolian-flat sediments from beach and dune deposits. In this study, though the ranges of K,. values were similar to those of Mason and Folk and overlapped in a similar way, a plot of K,, versus skewness (fig. 4) revealed no separation of eolian and beach sands. CONCLUSIONS Grain-size distribution appears to be reliable in distinguishing such deposits as glacial till from beach sands, but distinguishing beach and eolian deposits by this criterion is much more difficult. The present study indicates that none of the standard size param- eters or combinations of them can be used to separate Cape Cod beach sands from dune sands. These sands differ from many of those described elsewhere in that they are coarser grained and they are derived mainly from glacial debris Our results suggest that other factors such as source material may overshadow local sorting by the transporting medium and thus prevent distinguishing beach sands from eolian sands by statistical measures of the particle-size distribution. Grain-size parameters computed from sieve and settling-tube analyses are very similar, with the ex- ception of skewness. Sieve values for mean grain size tend to be slightly higher (finer grained) than set- tling-tube analyses of the same samples. Better sort- ing is indicated for sieved sands than for samples that were analyzed by settling velocity, though the difference is very slight. With a few exceptions, sieve analyses are negatively skewed and settling-tube val- ues are positively skewed. Kurtosis values from both methods are similar and broadly overlap the kurtosis shown by a normal curve. 'm SEDIMENTATION REFERENCES Andel, T. H. van, and Postma, Hendrik, 1954, Recent sedi- ments of the Gulf of Paria: Verh. Koninkl. Ned. Acad. Wetenschap., v. 20, no. 5. Doeglas, D. J., 1946, Interpretation of the results of mechani- cal analysis: Jour. Sed. Petrology, v. 16, p. 19-40. Folk, R. L., 1962, Of skewness and sands: Jour. Sed. Petrol- ogy, v. 32, p. 145-146. Folk, R. L., and Ward, W. C., 1957, Brazos River bar: a study in the significance of grain size parameters: Jour. Sed. Petrology, v. 27, p. 3-26. Friedman, G. M., 1961, Distinction between dune, beach, and river sands from their textural characteristics: Jour. Sed. Petrology, v. 31, p. 514-529. Harris, S. A., 1957, Mechanical constitution of certain pres- ent-day Egyptian dune sands: Jour. Sed. Petrology, v. 27, p. 421-434. 1959, The mechanical composition of some intertidal sands: Jour. Sed. Petrology, v. 29, p. 412-424. Hoel, P. G., 1954, Introduction to mathematical statistics (2d ed.): New York, John Wiley and Sons, 331 p. Inman, D. L., 1952, Measures for describing the size distribu- tion of sediments: Jour. Sed. Petrology, v. 22, p. 125-145. Mabesoone, J. M., 1963, Coastal sediments and coastal develop- ment near Cadiz (Spain): Geologic en Mijnbouw, no. 2, p. 29-44. Mason, C. C., and Folk, R. L., 1958, Differentiation of beach, dune and eolian flat environment by size analysis, Mus- tang Island, Texas: Jour. Sed. Petrology, v. 28, p. 211- 226. Shepard, F. P., and Young, Ruth, 1961, Distinguishing between beach and dune sands: Jour. Sed. Petrology, v. 31, p. 196- 214. Udden, J. A., 1914, Mechanical composition of clastic sedi- ments: Geol. Soc. America Bull., v. 25, p. 655-744. Zeigler, J. M., Whitney, G. G., Jr., and Hayes, C. R., 1960, Woods Hole rapid sediment analyzer: Jour. Sed. Petrol- ogy, v. 30, p. 490-495. GEOLOGICAL SURVEY RESEARCH 1964 AN INSTRUMENTAL TECHNIQUE FOR THE DETERMINATION OF SUBMICROGRAM CONCENTRATIONS OF MERCURY IN SOILS, ROCKS, AND GAS By W. W. VAUGHN and J. H. McCARTHY, JR., Denver, Colo. Abstract.-In the technique described and evaluated, detec- tion of mercury is based on the principle of atomic absorption. An analog signal, produced when mercury vapor absorbs ultra- violet light, is converted to digital form and calibrated to mercury concentration. Interferences are eliminated by selectively trapping the mercury on gold. The lower limit of sensitivity, using a 1-gram sample, is 5 parts per billion. A model of the instrument mounted in a station wagon has been tested successfully in the field. The high volatility of mercury and the association of small amounts of mercury with many sulfide de- posits suggest that extensive mercury halos may exist around sulfide deposits. Several investigations appear to substantiate this hypothesis (Saukov, 1946; Hawkes and Williston, 1962; Williston, 1964). More extensive application of the technique of locating sulfide deposits by detecting the associated mercury halo has been limited, largely because an analytical method of ade- quate sensitivity has not been available. The methods currently used for the determination of trace amounts of mercury have been reported by Williston. The instrumental technique described here provides a re- liable, rapid, and sensitive method for analyzing rocks, soils, and gases for mercury. The technique, with a sensitivity (5 parts per billion) well below the average abundance of mercury in rocks and soils, can be used to detect the small amounts of mercury that may indi- cate hidden ore deposits. There are many ways of using the large-volume atomic absorption technique for vapor analysis, as demonstrated by various types of commercially avail- able vapor detectors. These vapor detectors, however, are sensitive to several specific substances as well as to smoke and dust in general. When they are used it is therefore essential that the type of vapor be known if meaningful analyses are to be obtained. Our in- strument, the heart of which is a plug-in type of absorption chamber, was designed for specific applica- tion to mercury determination on a wide range of geologic materials. A gold-foil trap is used to sepa- rate mercury from contaminating vapors prior to its determination. INSTRUMENT DESIGN AND OPERATION The apparatus (fig. 1) used with this technique of mercury determination consists basically of an upright quartz tube with necessary accessories, and an absorp- tion chamber with associated electronic equipment. In operation, a sample holder is placed on an insulated rod and inserted by a revolving cam into the lower end of the tube. The holder and the sample are heated with 400-kilocycle radio-frequency energy for 2 min- utes, reaching a temperature of approximately 500°C. All of the mercury is vaporized and carried up the tube by an air stream created by a fan. Smoke re- sulting from burned organic matter is also carried by the air stream. The mercury is trapped by amalgama- tion with gold contained in a mercury trap at a con- striction higher in the tube, while smoke and gases pass on out the tube through the exhaust vent at the top. After the smoke and gases pass off, the air stream is diverted into an absorption chamber by changing a T-valve at the top of the tube. The mer- cury trapped on the gold is then volatilized by heating the gold with radio-frequency energy, and the result- ing mercury vapor is carried up the tube and into the absorption chamber. Two water-cooled copper coils control the temperature of the parts of the tube in which the sample and the gold are heated. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D123-D127 742-652 0O-64--9 D123 D124 > % ANALYTICAL TECHNIQUES Exhaust Mercury ABSORPTION CHAMBER -e- DIFFERENTIAL AMPLIFIER vOLTAGE- FREQUENCY CONVERTOR ELECTRONIC COUNTER (cs 1 WT—valve | Quartz -|- | tube $ {Tap water Mercury trap Glass wool TIMER Switch INDUCTION HEATER ge not oes cast tnt ae fae ster mat une ace foud impregnated with lead acetate Sample holder Insulated rod - Copper-bar conductors Fraur® 1.-Schematic diagram of mercury-vapor detector. As a result of passage of the mercury vapor through the absorption chamber the count rate increases to a maximum, then slowly returns to zero. The integrated count is recorded numerically and converted to mer- cury concentration by use of a calibration curve. The gold is allowed to cool to ambient temperature and the cycle repeated with another sample. Approxi- mately 8 minutes is required for the analysis of a sample; however, if it is known that the sample con- tains no organic matter the gold can be removed and the time for analysis cut in half. Two interchangeable absorption chambers, each hav- ing a single-spot ultraviolet-light source and two photosensing devices, were constructed for our study (fig. 2). The chambers have different optical geometry but are approximately equal with respect to sensitivity and selectivity. Chamber operation is based on the fact that mercury vapor in an unexcited state will absorb its resonant energy (2,537 angstroms). The single-cavity chamber (fig. 24) has an optical filter (f) between one photocell (@) and the ultraviolet lamp (4). This photocell responds to all changes in VAUGHN AND McCARTHY D125 =-1 -- Photocell | Photocell ~-[~- To @@ - '. (b, > als amplifier | _/ . I - t o oe a CF Ls amplifier Ultraviolet _- filter (£) - Ultraviolet lamp (d) __ __ To power source j- Schematic diagram -- of exhaust system ° shown on figure 1 R | Mercury _|] P< f-f trap energy (e) M) SINGLE- CAVITY Gasle CHAMBER saimr ; yPhétOfCeli | Photocell ~~ ) - @ _ | .' (b) : f a . ufs, ? 2 p ele |amplifier Cavity 1 Cavity 2 | Ultraviolet lamp (d. LA”! To power source Mercury | Mercury D| or-f trap trap |) energy (F) (e) DOUBLE - CAVITY CHAMBER B ¢ Gas sample Figur® 2.-Single-chamber (4) and double-chamber (B) absorption chambers for mereury-vapor detection. light intensity except those changes caused by absorp- tion of light in the effective range of the filter. The unfiltered photocell (%) responds to all changes in ultraviolet light intensity. The ratio of the electric current generated by the unfiltered photocell to the current generated by the filtered cell is proportional to the absorption of ultraviolet light by the filter and by mercury vapor, from the trap (e), passing through the chamber. The double-cavity chamber (fig. 22) has two mer- cury traps and two cavities, through each of which the air stream is drawn with equal velocity. One trap (f) removes all mereury from the air stream passing through cavity I. Consequently, this cavity has no resonant absorption and can be used as an optical blank or reference. The second trap (e) removes the mercury from the air stream entering cavity 2. After the two cavities have been nulled electronically the mercury in the second trap is released by heating and is drawn through cavity 2. The amount of mercury drawn through cavity 2 is then determined from the ratio of photocell currents in the two cavities. The ratio of photocell currents from either the single- or double-cavity chamber is converted to a D126 voltage, amplified by a differential amplifier, and fed into a 100-kilocycle voltage-to-frequency converter. The output from the converter is fed into an electronic counter capable of 1 billion counts total. The numeri- cal indication is read directly from the counter and by means of a calibration curve is translated into mer- cury concentration. Approximately 15 grams of gold squares 2 mm on a side and / mm thick were used for each mercury trap. The gold is supported by a plug of glass wool at the constriction of the quartz tube and is positioned in the center of the upper coil. Experiments conducted to determine the temperature at which the mercury is released from the gold showed that very little mercury is volatilized until a temperature of 400°C is attained, at which time a sharp evolution of mereury occurs. All the mercury is driven off when the temperature reaches 500°C. In practice the gold is heated for 2 minutes and attains a temperature of about 600°C. Platinum metal is also a good mercury trap, but mercury is not released from it as readily as from gold. At the maximum temperature attained by the platinum (615°C) less than half the mercury was volatilized. Apparently a more stable amalgam is formed between mercury and platinum than between mercury and gold. Two standard samples were used to determine the temperature at which mercury is volatilized. One standard sample was prepared by diluting cinnabar with quartz, and the other, mercuric oxide with quartz. The mercury began to volatilize at about 150°C, con- tinued at a regular rate and was completely released from the sample when the temperature had reached 300°C. No difference in the temperature or rate of evolution of mercury was detected using either stand- ard sample. A 1.0-g sample of rock was found to reach a temperature of 500°C in this time, allowing a comfortable margin for differences in heating. The rate of flow of air, hence of mercury, through the absorption chamber has a pronounced effect on the count obtained. In general, the faster the mercury vapor passes through the chamber, the lower the total count. However, reproducibility is poorer at very low flow rates, and sensitivity poorer at rapid rates. Air flow- ing at the rate of 60 milliliters per minute was found to provide the desired balance between good repro- ducibility and good sensitivity. The rapid flow of the mercury vapor past the gold of the mercury trap presented the possibility that some of the mercury might not be trapped. In a test to check this, sample aliquots containing as much as 40 micrograms of mercury were run through the ap- paratus, and all the mercury was found to be trapped. ANALYTICAL TECHNIQUES Gold thus proves to be a very efficient trap for mer- cury. This is particularly important in the analysis of air or soil gases, during which large volumes of gas must be rapidly passed around the gold. INTERFERENCES The principal interference encountered in this tech- nique is from smoke from organic matter in the sam- ples. Interference from this source has been largely overcome by selectively trapping the mercury on gold and allowing the smoke to pass by. Samples con- taining less than 10 percent organic matter can be analyzed reliably. With samples containing more or- ganic matter, interference is met, presumably because incompletely burned organic matter condenses on the gold and burns when the gold is heated, producing smoke which passes into the absorption chamber along with the mercury. It is also possible that tars, and other products from the organic material, condensing on the gold lessen its effect as an amalgam, thus allow- ing some mercury to escape detection. A second source of interference is sulfur dioxide gas which results when sulfide minerals are heated; the gas strongly absorbs ultraviolet light. Interference from this source is eliminated by covering with iron filings those samples that contain sulfides. It was found necessary to bake the iron filings in air at 600°C for several minutes to completely eliminate sulfur interference. A loose-fitting plug of glass wool impregnated with lead acetate is placed in the quartz tube between the upper and lower coils to absorb the small amounts of sulfur found in many rocks and soils. It is believed that most interfering gases entering the chamber well below saturation diffuse very rapidly and upon reaching a homogeneous condition are nulled by equal response in the photocells If on the other hand the interfering gases are concentrated and form striated patterns that screen only one photocell, the result prohibits valid mercury analysis. SENSITIVITY, ACCURACY, AND PRECISION A calibration curve was prepared by analyzing, in the manner described above, different weighed aliquots of a standard sample. Total counts versus nanograms of mercury were plotted on a rectilinear graph (fig. 3). The curve is linear and has a slope of one; thus a single standard sample analyzed at regular intervals serves to monitor variations in operating conditions, and the curve can be changed accordingly. A sample aliquot containing 10 nanograms of mer- cury gives about 1,200 counts, 100 nanograms about 12,000, and so forth. Approximately two minutes are VAUGHN AND McCARTHY 40,000 |- 30,000 20,000 T TOTAL COUNT 10,000 | 1 1 1 | 100 150 200 250 300 MERCURY, IN NANOGRAMS 0 50 Freur® 3.-Calibration curve for mercury determinations. required to obtain a total count of 12,000. Because of circuit nonlinearity, counting efficiency decreases in excess of 50,000 counts ; therefore, small aliquots should be taken. The lower limit of sensitivity can be ex- tended by volatilizing mercury from a large sample and collecting it on the gold. A 1.0-g sample of most rocks is sufficient to give a detectable count. This is not unexpected, because present data indicate that the abundance of mercury in igneous rocks and in lime- stone is 80 and 30 parts per billion, respectively (Green, 1953). The reproducibility of the method was determined by analyzing a standard sample 10 times (table 1). The standard sample used was that containing cinna- bar diluted with quartz. The variation in results is attributed to voltage fluctuations that influence the stability of the instrument, the distribution of mercury in the sample, and the variable concentration of mer- cury in the air. The accuracy of the method was assessed by com- paring the mercury content determined by the mercury detector with the mercury content determined by a spectrographic method (Sergeev, 1961). Data from the spectrographic analyses are shown in table 2. The samples listed in table 2 are jasperoid and silicious limestone. $ D127 1.-Replicate analyses of a standard sample Mercury Total (nanograms) counts 100 s s 2 o SAL s L t ale a hohe fe e en he se e a he l Bo oe he a me W e e a tn he e e e an as 11, 603 TOO L_ eL e ILl l eo eee e aio an hie ail aie aln aie a mie be 'e in a ie a a 11, 519 ivan lel (a" E TOO ; 2. 22. 2 ne at ee a ee oo o mole h l oa ne t o a at mn e ot an an n'a Ne Ne be n oe ie e s e In s ie 11, 839 100 >: (3 2222 aisle .. oll U Ll b i a arte p l ae le in a an ae e toe to a cline e t ae he if e a is 11, 826 100 # Lc LILLIE kena aaa k -n B as an tole a's 11, 715 look : fill" [_ IML ll n 12, 042 400 2 2 24 22 ee a o e ole o alel elle t wo hope m ul ha n e a e agli e nce e te t. ct te Wef a a 12, 421 100; X_ LLL Ce OP JO Hanan aan aige ain alike mie win's a 11, 568 1002 % » LE eee doe ena bk a aie aln aln a alle 6 mine Tole in ss 11,130 MCAN 42 1 2222 2 a+ -o - ml m mile ie inl bacs e he nd a ue as a o bn ania in toku n i 11, 709 Deviation from the mean, 11 percent 2.-Comparison of data obtained by mercury detector and spectrographic method on standard sample [Analyst, Paul Barnett] Mercury (ppm) Sample No. Detector Spectrographic method I Relese be aoe a ai nals mle 19. 5 18. 0 i ane ws ole a ee aE o n calne a wc ae oa tn arine n ie l t ase 2.1 2. 8 No ain an ae melanie a oul Palk mina al wie a alel a ini . 85 . 89 AEI LEITH wae o u eee 22 . 30 Mre cue nee helena oue a ae eca pene 07 12 FIELD TRIAL The instrument was installed in the back of a four- wheel-drive station wagon for field checking. Power for operation was supplied by a 110-v a-c generator of 4 kw capacity. The generator was mounted between the two front seats and operated by the power takeoff of the vehicle. Several hundred samples were analyzed in the field in 1963 to evaluate the usefulness and relia- bility of the instrument under field conditions. The instrument proved useful in the field to indicate the type of material to be sampled as well as the area to be sampled. Application of the instrument to geo- chemical exploration will be described at a later date. REFERENCES Green, Jack, 1953, Geochemical table of the elements for 1953: Geol. Soc. America Bull., v. 64, p. 1001-1012. Hawkes, H. E., and Williston, S. H., 1962, Mercury vapor as a guide to lead-zine-silver deposits: Mining Cong. Jour., v. 48, no. 12, p. 30-32. Saukov, A. A., 1946, Geokhimiya rtuti [Geochemistry of mer- cury]: Tr. AN SSSR, Min. Geokh,. ser., no. 17. Sergeev, E. A., 1961, Methods of mercurometric investigations : Internat. Geol. Rev., v. 3, no. 2, p. 93-99. Williston, S. H., 1964, The mercury halo method of explora- tion: Eng. Mining Jour., v. 165, no. 5, p. 98-101. GEOLOGICAL SURVEY RESEARCH 1964 DETERMINATION OF MERCURY IN VEGETATION WITH DITHIZONE-A SINGLE EXTRACTION PROCEDURE By F. N. WARD and JOHN B. McHUGH, Denver, Colo. Abstract.-A spectrophotometric method for determining small amounts of mercury in vegetation is based on the re- action of mercury with dithizone after sample dissolution by wet ignition under reflux. Treatment of the sample solution with sulfur dioxide provides a reducing environment during the formation and extraction of the mercury dithizonate into n-hexane. Thus, a single extraction suffices to obviate side reac- tions, and double extractions or reversion steps are unneces- sary. The method is useful for determining as little as 0.4 ppm of mercury in dry vegetation, and this range is enough to evaluate the usefulness of the mercury content of vegeta- tion in prospecting. The mercury content of vegetation may be a useful guide in biogeochemical prospecting, and in order to facilitate the evaluation of this parameter a sensitive method is needed to determine small amounts of mer- cury likely to be present in different vegetation sam- ples. The reaction between mercury and dithizone in an acidic medium to form an extractable orange mercuric dithizonate is the basis of a colorimetric procedure that appears to be suitable for vegetation. To date this reaction is the basis of several methods of deter- mining mercury in biological materials such as urine, blood, kidney tissue, and various other kinds of human tissue (Cholak and Hubbard, 1946; Kozelka, 1947; Barrett, 1956), but it has not been applied extensively to the determination of mercury in vegetation except where the mercury resulted from pesticide applications (Hordynska and others, 1961) and the concentration was relatively large. Sample dissolution of biological materials including vegetation is most often accomplished by a wet oxida- tion under reflux. A mixture of hot acids is used to oxidize the material, and the residual products of the decomposition often cause oxidation of the dithizone to another compound, diphenylthiocarbadiazone, which is yellow and also extractable into various immiscible solvents. This tendency is a serious drawback to dithizone procedures and often leads to difficulties, especially in the determination of mercury, because of the similarity in the color of mercuric dithizonate and diphenylthiocarbadiazone. The difficulty is most often overcome by the use of a double extraction technique-similar to double pre- cipitation-or to the reversion principle as suggested by Irving and others (1949) and modified by Simon- sen (1953). In the proposed procedure a single extraction of the acidic sample solution is made after bubbling sulfur dioxide gas through the solution prior to adjusting the pH to 4. This simple expedient nullifies the oxi- dative properties of the sample solution with respect to dithizone and no reduction of mercury (II) to mer- cury (I) occurs (Melles and De Bree, 1953), as shown by absorption measurements of mercury dithizonate formed in the presence and absence of sulfur dioxide. At the pH used to extract the mercury dithizonate, bismuth, copper, and silver form extractable dithi- zonates, but copper and bismuth are complexed with EDTA (ethylenediamine tetraacetic acid, disodium salt), and silver is removed with thiocyanate. The procedure as described has a useful range from 0.4 parts per million of mereury upward, depending on the aliquot size. The sample size may also be adjusted within limits to extend the range. The ratio of digesting mixture to sample has to be maintained, and the volumes of acids should be adjusted along with the sample size. We wish to acknowledge the assistance of E. H. Bailey of the U.S. Geological Survey and Professor H. V. Warren of the University of British Columbia, who furnished the samples of vegetation included in this paper. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D128-D130 D128 WARD AND McHUGH REAGENTS AND APPARATUS Ammonium hydroxide, concentrated, A.C.S. Ammonium hydroxide, 0.414, metal-free. Bubble ammonia into demineralized water. Ammonium thiocyanate, 5-percent. Dissolve 5 grams of am- monium thiocyanate (NH,SCN) in 100 milliliters of metal- free water. Buffer. Mix 1 liter of 2M acetic acid with 500 ml of 2M sodium acetate. Prepare 2M acetic acid by mixing 114 ml of glacial acetic acid with water and adding water to 1 liter. Prepare 2M sodium acetate by dissolving 164 g of the anhydrous salt or 272 g of the trihydrate in water and adding water to 1 liter. Adjust pH of mixture to 4.0+0.2 by adding 2M acetic acid or 2M sodium acetate solution. Bromophenol blue. Grind 0.1 g in a mortar with 15 ml of 0.01M sodium hydroxide and dilute to 250 ml with water, or dissolve the commercially available sodium salt in water. Store in small dropping bottle. Dithizone, O0.Ol-percent (w/v). Dissolve 0.01 g of purified reagent in 100 ml. of reagent grade chloroform (CHCls3). Remove trace metals from the chloroform by shaking once with 10 ml of-0.51 sulfuric acid, and removing acid by shaking successively 3 times with 50-ml portions of metal-free water. Dithizone, 0.0015-percent (w/v). Mix 15 ml of the 0.01-per- cent solution of dithizone in chloroform with 85 ml of n-hexane. Ethylenediamine tetraacetic acid, disodium salt (EDTA). n-Hexane, practical grade. Remove trace metals by the pro- cedure suggested above for chloroform. Hydrogen peroxide, 50-percent. Hydroxylamine sulfate solution, 20-percent. Dissolve 20 g of hydroxylamine sulfate (NH;OH -HSO,) in 100 ml of metal- free water. Mercury standard A. 1,000 micrograms per ml. Dissolve 0.1354 g of reagent grade mercuric chloride (HgC);) in 100 ml of 0.5AI sulfuric acid. Mercury standard B. 10 ug per ml. Dilute 1 ml of standard A to 100 ml with 0.5M sulfuric acid. This standard is stable for at least 3 months at ordinary temperatures. Nitric acid, concentrated, A.C.S. Perchloric acid, 70-percent. Sulfuric. acid, concentrated, A.C.S. Sulfur dioxide gas. Can be generated in situ or delivered from cylinder. Water, metal-free. Purify by passing tap water through any of the several types of resin demineralizers now commercially available. Condenser, 300-mm; with standard taper 24/40 male. Flask, round-bottom, 300-ml capacity ; with standard taper 24/40 female. Flask, volumetric, 100-ml capacity. Funnels, separatory, 125-ml. Heating mantles with variacs for control. Pipets. PROCEDURE FOR MERCURY IN VEGETATION Digestion of sample To a 1- or 2g sample of ground vegetation in a 300-ml round bottom flask add 2 ml of water and 5 ml each of perch- lorie acid, sulfuric acid, and nitric acid. D129 After addition of acids, connect flask to water-cooled con- denser through standard taper 24/40. Set heating mantle at low heat (60°-70°C) at first and at higher settings as the oxidation proceeds. As the oxidation nears completion-re- action subsides-increase heat until moderate refluxing occurs and temperature reaches 140°-145°C. Maintain moderate re- fluxing for 1 hour. Remove heating mantle and add 1 ml of 50-percent hydro- gen peroxide through condenser. Allow flask to cool to about 80°-90°C and add four 10-ml portions of metal-free water through condenser to digestion mixture. Disassemble the apparatus and transfer contents of digestion flask to 100-ml volumetric flask. Wash digestion flask twice with 10-ml por- tions of metal-free wash water. Add 5 ml of 20-percent hydroxylamine sulfate to flask and make up to 100 ml with water. Mix. Extraction Transfer a 5- to 50-ml aliquot to a 125-ml separatory funnel and bubble sulfur dioxide through aliquot for 1 minute. Ali- quots smaller than 50 ml should be made up to that volume with water prior to sulfur dioxide treatment. Add 3 drops of bromophenol blue, 0.5 g of disodium salt of ethylenediamine tetraacetic acid (EDTA) and concentrated ammonium hydrox- ide drop by drop until near color change. Cool contents of funnel to about 25°C and continue ammonia addition until the color change. Add 20 ml of acetate buffer, cool, and add 5 ml of 0.0015-percent dithizone in n-hexane and shake mix- ture for 2 minutes. Allow phases to separate and discard separated aqueous-lower-phase. Estimation To the hexane solution in the 125-ml separatory funnel add 10 ml of metal-free water and shake 5 seconds. Drain and discard separated aqueous phase. Repeat using 10 ml of ammonium thiocyanate reagent in place of water. After draining the separated aqueous phase, add 5 ml of 0.4 molar metal-free ammonium hydroxide and shake funnel for 10 seconds. Drain and discard the aqueous phase. Decant or- ganic phase into cuvette and measure transmittance at 490 millimicrons. Ascertain the mercury content of the extract by referring to a standard curve established as follows: To 5 round-bottom digestion flasks add incremental amounts of mercury from a 10 y/ml standard solution as follows: none to first flask, 2 y to second flask, 4 y to third flask, and so forth. The highest standard will seldom need to be greater than 16 7. Digest contents of flasks for usual time and treat digestates as described above. Take aliquots of 50 ml from each standard solution to obtain a standard series consisting of none, 1.0, 2.0, 4, and 8 y of mercury. As little as 0.4 y of mercury in 5 ml of n-hexane is easily detected and if one starts with a 2-g sample and takes a 50-ml aliquot-equivalent to 1 g of vegetation-he can measure as little as 0.4 ppm of mercury in the dry sample. RESULTS The repeatability of the proposed procedure was tested by making 5 separate determinations on 11 differ- ent plant samples ranging in mercury content from about 0.6 ppm to more than 90 ppm. The range of the repeat determinations, the relative standard devia- tion, and the confidence limits at the 95-percent level D130 are shown in table 1. As expected, the precision deteri- orates as the lower limit of the method is approached. Other differences in the relative standard deviation can in certain samples be correlated with differences in grinding techniques. Some of the air-dried samples were ground to pass a sieve with holes 1 mm in diam- eter, and others were pulverized in a Waring blender with no special precaution to insure a maximum parti- cle size or guarantee the fineness. All were hand mixed prior to analysis. TaBur 1.-Repeatability of mercury determinations [Five determination on each samp, except as noted. Confidence limits about mean at the 95-percent level] Mercury found (ppm) Relative stalad- Sample No. Name of vegetation Mean and dyvia- High | Low | confidence tion limit at 95- (per- percent level | cent) Na-4...._. Chamise (Adenos- 1. 0| 0. 4) 0. 6+0. 2| 1 28. 3 toma fascicula- tum). Na-5...__. PBaccharis....__...... T .4| 0.6+0.2] 20.0 1.3) 1.2] 1.2+0.1 5. 8 Na-1..... Chamise (Adenos- 2.2] 1.6| 1.8+0.3| 13.3 toma fascicula- tum). Shepherdia cana- 2. 4} 2.3| 2. 4+0.1 2. 9 densis. Na-3.-.... 2.7) 2.3| 2.540. 2 6. 8 65-142.... Luping............. 4.7) 3.8 4.3+0.5 9. 5 63-197 ___ Shgpherdia cana- 13. 5) 9.0] 11. 8+2.3| 14.4 ensts. 63-195.___| Populus trichocarpa-_|22. 0|19. 0| 21.0 +1. 2 4. 8 63-191-___| Betula papyrifera____|42.0|40.0| 40. 8+1.4| 2.7 63-0... Shepherdia cana- 97. 0/90. 0| 93. 0 +4. 1 3. 6 densts. 110 repeats. The presence of relatively large amounts of salts resulting from the neutralization of the excess acid after sample dissolution has a depressive effect on the extraction of mercury dithizonate into n-hexane. The results obtained by taking different sized aliquots are given in table 2. Aliquots of 25 ml or less but adjusted volumetrically for valid comparison showed higher values than aliquots of 50 ml. Although our data are not sufficiently detailed to permit more than a qualita- tive interpretation, the behavior is one of inhibition of extraction by the presence of salts and not of enhance- ment such as observed in cases of salting out of an organic solvent. The effect is readily produced by the R ANALYTICAL TECHNIQUES addition of a salt such as ammonium sulfate prior to the extraction. The danger of indiscriminate use of different aliquots is clear, especially when determining mercury contents of a few parts per million. Tapu 2.-Effect of aliquot size on determination of mercury in vegetation M found in ali {- Sample No. Name of vegetation fori found fu aligns o 5 ml 10 ml 25 ml 50 ml Na-2..... 1. 0 1. 6 1. 3 Na-1....:. Chamise (Adenos- _ |______ 1. 5 2. 4 1.9 toma fasciculatum). 63-201b...| Shepherdia canaden- |______ 2. 0 2. 4 2. 4 818. Na-3......! 3. 0 3. 0 2. 8 635-142a...! 6. 0 | 6.0 5. 6 3. 8 do... 6. 0 6. 0 5. 2 4. 2 63-195.-__| Populus trichocarpa-_| 22. 0 | 22. 0 | 22. 0 17. 6 63-191a.._| Betula papyrifera... 34. 0 | 40.0 | 38.0 |_____. Like most analytical methods for plant materials, the proposed procedure is at a disadvantage in the time required for sample dissolution. However among dithizone procedures, it possesses several advantages, such as freedom from oxidation of the dithizone, single, in place of double extraction, and direct meas- urement of the mercury dithizone complex. REFERENCES Barrett, F. R., 1956, Microdetermination of mercury in bio- logical materials: Analyst, v. 81, p. 204-208. Cholak, Jacob, and Hubbard, D. M., 1946, Microdetermination of mercury in biological material: Indust. and Eng. Chemistry, Anal. Ed., v. 18, p. 149-151. Hordynska, S., Legatowa, B., and Bernstein, I., 1961, Colori- metric determination of microgram quantities of mercury in grains and apples: Roczniki Panstwowege Zakladu Hig., v. 12, p. 105-108. Irving, H., Andrew, G., and Risdon, E. J., 1949, Studies with dithizone, pt. I. The determination of traces of mercury: Jour. Chem. Soc., p. 541-547. Kozelka, F. L., 1947, Determination of mercury in biological material: Indust. and Eng. Chemistry, Anal. Ed., v. 19, p. 494. Melles, J. L., and De Bree, W., 1953, The determination of microgram quantities of mercury: Recueil des Travaux Chimiques des Pays-Bas, v. 72, p. 576-80. Simonsen, D. J., 1953, Determination of mercury in biological materials: Am. Jour. Clinical Pathology, v. 23, p. 789-797. GEOLOGICAL SURVEY RESEARCH 1964 ION-EXCHANGE SEPARATION OF TIN FROM SILICATE ROCKS By CLAUDE HUFFMAN, JR., and ARDITH J. BARTEL, Denver, Colo. Abstract.-An ion-exchange, carbamate extraction method has been developed for the isolation of microgram amounts of tin in silicate rocks before fluorimetric determination with flavonol. The lower limit of detection is about 2 parts per million when a 2-gram sample is used. Because of the low concentration of tin in rocks and the insensitivity of analytical reagents, tin must be isolated from a large sample and concentrated in a small volume of solution before quantitative determi- nation. The familiar hydrobromic-hydrochloric acid distillation procedure, one modification of which is described by Onishi and Sandell (1956), is generally used to make the separation. Although this method provides a good separation of tin from most elements, it is time consuming, and a need exists for a more rapid separation having equal reliability. An ion- exchange, carbamate extraction method has been de- veloped for the isolation of microgram amounts of tin. This procedure reduces the separating time by a factor of about four. Few references are given in the literature as to the anion-exchange behavior of tin. Smith and Reynolds (1955) separated tracer quantities of Snt*, Sbt5, and Tet* from each other in 0.1 J/ oxalic acid on an oxalate-form, anion-exchange resin and eluted the Snt*, with 1 J/ H,SO,. This separation is not ap- plicable to solutions of rock samples, because in oxalic acid solution many elements are insoluble and tin can- not be separated from common elements, such as iron. A hydrochloric-oxalic acid influent is used to solve these difficulties. Tin is absorbed on an oxalate-form, anion-exchange resin from a hydrochloric-oxalic acid solution and is eluted with 1 MJ H,SO,. The tin in the eluted solution is then concentrated into a small volume by a carba- mate-chloroform extraction. To oxidize tin and to bring it into water solution, the chloroform extract is wet ashed with HNO;, H,SO,, and HCIO,. Tin, in the final solution, is determined fluorimetrically with flavo- nol, as described by Coyle and White (1957). If a 2.0-gram sample is used, the method has a lower limit of detection of about 2 parts per million. The dithiol procedure (Onishi and Sandell, 1956) may be used to estimate tin directly in an aliquot of the [eluant] solution when the sample contains more than 20 micrograms of tin. This alternative procedure may be useful, following ion-exchange separation of the tin, for scanning samples for their tin content. EXPERIMENTAL Apparatus.-The fluorimeter used is described by Parshall and Rader (1957). This fluorimeter was adapted to measure the fluorescence of solutions by rotating the search head 90° and attaching it to a 5-centimeter cell compartment (Beckman, D.V. part). Light filters found satisfactory are Corning 2-inch polished squares, primary filter No. 5970 (ultraviolet transmit- ting) and secondary filters No. 5543 (blue) and No. 3389 (sharp- cut). - Any fluorimeter may be used that has sufficient sensitivity to measure the blue fluorescence of the tin flavonol complex at about 470 my. Reagents.-The resin column is 25 cm long, with an inside diameter of 0.8 cm. Convert Dowex 1 (X-8, 50 to 100 mesh, chloride form) to the oxalate form by allowing the resin to stand in a 1.0 M oxalic acid solution for several days. Prepare the resin column by adding the oxalic acid solution-resin slurry until the slurry is 10 cm in depth. No attempt was made to regenerate the used resin; it was discarded after each run. Thioglycolic acid, 80 percent. Avoid use of old reagents. N, N'-Dimethylformamide, C.P. grade, no purification neces- sary. Flavonol (3-hydroxyflavone) solution, 0.05 percent (w/v) in redistilled 95-percent alcohol. Diethyldithiocarbamic acid, diethylammonium salt solution, 1 percent (w/v) in water. Sn+* stock solution (1 milliliter=1 milligram). - Dissolve 0.100 g of tin metal in 50 ml hot concentrated H,SO,. Heat to sulfuric acid fumes, cool, and make to 100-ml volume with water. Standard Sn+* solution (1 ml=100 ug). Transfer 10 ml of the tin stock solution to a 100-ml volumetric flask, add 3.3 ml HSO, and dilute to volume with water. Make appropriate U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D131-D133 D131 D132 dilutions from the 100 ug/ml solution, keeping the acid concentra- tion at 3 N H,SO,. Procedure.-Transfer 2.0 g of the rock powder to a platinum dish. Process a reagent blank with the samples. Add 10 ml demineralized water, 10 ml HNO, 10 ml HF, cover, and let stand overnight. Add 10 ml MCIO, and 5 ml H,SO,. Place dish on a steam bath and evaporate for about 1 hour, then place dish on a hot plate and fume off the acids until about 3 ml remain. Wash down the sides of the dish with water, add 5 ml HCIO, and repeat the fuming until all the acid is evaporated. Do not bake the salts Cool. Add 12 ml HCl and 25 ml water to the dish, cover and digest on the steam bath for 30 minutes. If an insoluble residue remains, filter the solution through a retentive filter paper into a 100-ml volumetric flask. Wash residue with water. Place filter paper in a zirconium crucible and ignite it at 500°C. in a muffle furnace. Cool. Fuse residue with 1.0 g NaOH and cool. Dis- solve the melt in 10 ml water, add sufficient HCl to neutralize the NaOH and combine the solution with the reserved filtrate. Add 10 ml 0.5 M oxalic acid to the flask and dilute to volume with water. Condition the resin column for use by passing 100 ml 0.1 M oxalic acid through it and leave about 1.0 ml above the resin. Quantitatively transfer the sample solution to the resin col- umn. Regulate the flow rate of the solution through the column to about 2 ml per minute. When the flow stops, dis- card the solution that has passed through, wash the column with 25 ml 0.1 Jf oxalic acid solution and discard the wash solution. Elute the tin by passing 100 ml of 1 M H,SO, through the resin column at a flow rate of 1 ml per minute and discard the first 25 ml. Catch the next 75 ml of 1M H,SO, in a 100-ml volumetric flask and dilute to volume with water. The carbanate separation described below must be carried out within 48 hours. Quantitatively transfer a 50-ml aliquot of the solution con- taining the tin to a 125-ml separatory funnel. Add 0.1 ml thioglycolic acid and mix. Immediately add and mix in 3 ml diethyldithiocarbamate solution. Add 10 ml redistilled chloro- form, stopper the funnel, and shake to extract the tin-carbamate complex. Drain the chloroform layer into a clean 150-ml beaker. Repeat this operation twice more, starting with addi- tion of diethyldithiocarbamate solution, and combine all the chloroform extracts in the 150-ml beaker. Discard the aqueous phase. Add 5 ml HNO,, 4 ml H,SO,, and 5 ml HCIO, to the beaker. Place the beaker on a steam bath and evaporate the solution to about 10 ml. Place beaker on a shaking hot plate and fume until about 0.5 ml H,SO, remains. Cool. Add 10 ml water to the beaker, transfer the solution to a 25-ml volumetric flask and dilute to volume with water. Transfer an appropriate aliquot (1 to 3 mi) of the solution, containing less than 4 ug of tin, to a 25-ml volumetric flask. Add 7.5 ml N,N'-dimethylformamide to the flask and mix. Add 2 ml flavonol solution, dilute the solution to 25-ml volume with water, and mix. Let stand 30 minutes and then measure the blue fluorescence of the solution in a 5-cm cell with a suitable fluorimeter. Use the 4-4g standard described below as the reference solution. Standardization.-Add 0, 0.25, 0.50, 0.75, and 1.0 ml standard ANALYTICAL TECHNIQUES Snt+* solution (1 ml=4 ug Snt') respectively to separate 25 ml volumetric flasks. Add sufficient 3 N H,SO, to each flask so that each will contain 1.0 ml of 3 N H,SO,. Process standards as directed in the preceding paragraph, starting with the addition of N, N'-dimethylformamide. RESULTS AND DISCUSSION Radioactive Sn 113 was used as a tracer to study the behavior of tin on the resin column. Tests with Sn 113 added to shale solutions and processed through the ion-exchange step of the procedure showed an average tin recovery of 97 percent. About 98 percent of the tin is absorbed on the resin and 96 percent or more of the total is eluted with 100 ml of 14 H,SO,. Experiments showed that the first 25 ml of 1 MM H,SO, passed through the column contains little or no tin; therefore, this portion is discarded because it contains the major portion of any iron absorbed on the column. The effect of other ions on the recovery of tin was studied, using the described procedure. Single test solutions containing 200 ug of tin and different amounts of diverse ions were processed, starting with ion-ex- change separation. Tin determinations in these tests show a range from 95 to 110 percent recovery (table 1). With the exceptions of copper and bismuth, all these determinations are within the coefficient of variation of 5 percent determined for standard tin solutions processed with no interfering ions. 1.-Recovery of tin in the presence of other elements Amount of | Amount of | Tin recovered Element. added element added] - tin added (micrograms) (micrograms) | (micrograms) Biel eect nant tuk ae anm 250 200 215 CUL: 500 200 220 Ni. . 22 eac aus 500 200 205 leela ees, ane 200 200 210 100 200 200 y ants ss onal 100 200 210 Od. L lee bence s 100 200 195 sens 100 200 210 ye sent 200 200 210 CF.... 500 200 190 200 200 205 P 90, 000 200 200 PN.. tnt 200 200 The effect of other ions in diabase (standard sample W-1) and granite (standard sample G-1) on recovery of tin, in the procedure described here, was investigated. Solutions were prepared from 1.0-g samples of these rocks, spiked with 100 ug of tin, and then analyzed for tin. These recovery experiments were run on three different days. The recovery of tin added to the solution of granite G-1 was 98, 100, and 99 ug, and the tin recovery from diabase W-1 was 92, 95, and 90 ug. The small amount of tin, 2 to 3 ppm, reported in these HUFFMAN samples (Fleischer and Stevens, 1962) is not significant in figuring percent recovery. Analysis of granite G-1 in this laboratory, with no tin added, showed an average value of 2.7 ppm tin. TaBur 2.-Comparison of tin content of seven samples from Seward Peninsula, Alaska, determined by the method described in this paper and by the bromide distillation method [Samples collected by C. L. Sainsbury. Tin determined chemically by the aut hors and Dorothy Ferguson '] Tin (percent) Method |Bromide e- distilla- scribed. tion in this |method ' paper Sample No. Sample description 284632_._./0. 0015) 0. 003) Stream sediment from Boulder Creek, Cape Mountain, containing prin- cipally grains of granite, dark dike rock, and limestone. Stream sediment from south contact area of granite of Car Mountain. Contains grains of granite, tactite, marble, and tourmalinized granite. Stream sediment from Tin Creek, west of granite in Lost River area. Stream sediment from east branch of Mint River that heads against west side of granite of Brooks Mountain. Contains grains of lime- stone, tactite, and granite. Fragment of mineralized rock from dump at Winfield shaft, Car Mountain. 284648-_-_| . 00483] . 005 284584. ._ 284612... . 0082 . 013 . 008 . 010 284701.__| . O18 | . O21 284576...| . 042 | . 040] o. 284668._..| . 12 . 11 | Slope wash below tin-uranium pros- pects southwest side of Brooks Mountain. * Method described by Onishi and Sandell (1956). AND BARTEL D133 The blue fluorescence produced by the tin-flavonol complex is very stable. Over a 3-month period, the tin standards have not deviated more than +1 scale division. This reproducibility is exceptionally good for a fluorimetric reagent. Optimum conditions for the flavonol determination, such as acid, N,N'-dimethyl- formamide, and flavonol concentrations, are described in detail by Coyle and White (1957). Seven selected rock samples from the Seward Peninsula, Alaska, previously analyzed for tin by the bromide distillation separation and estimation by dithiol as described by Onishi and Sandell (1956), were analyzed by the new method. Results obtained are compared in table 2. REFERENCES Coyle, C. F., and White, C. E., 1957, Fluorimetric determina- tion of tin with flavonol: Anal. Chemistry, v. 29, p. 1486- 1488. Fleischer, Michael, and Stevens, R. E., 1962, Summary of new data on rock samples G-1 and W-1: Geochim. et Cos- mochim. Acta, v. 26, p. 525-543. Onishi, Hiroshi, and Sandell, E. B., 1956, Colorimetric deter- mination of traces of tin with dithiol: Anal. Chim. Acta, v. 14, p. 153-161. Parshall, E. E., and Rader, L. F., Jr., 1957, Model '54 trans- mission and reflection fluorimeter for determination of uranium, with adaptation to field use: U.S. Geol. Survey Bull. 1036-M, p. 221-251. Smith, W. S., and Reynolds, S. A., 1955, Anion exchange sepa- ration of tin, antimony, and tellurium: Anal. Chim. Acta, v. 12, p. 151-153. € GEOLOGICAL SURVEY RESEARCH 1964 DETERMINATION OF CARBONATE, BICARBONATE, AND TOTAL CO, IN CARBONATE BRINES By S. L. RETTIG and B. F. JONES, Washington, D.C. Abstract.-Samples of carbonate brines having a CO, content in the range from 0.5 to approximately 9 percent have been analyzed by potentiometric titration and manometric measure- ment of total CO; evolved upon acid treatment. A plot of the potentiometric data shows inflection points that indicate that the carbonate and bicarbonate end points may differ significantly from the pH values of 8.2 and 4.5 used in routine water analysis. The direction, source, and range of error in the potentiometric method is evaluated by comparative use of the manometric technique. The following presents a preliminary study of a problem in the analysis of concentrated waters from lacustrine closed basins. The western Great Basin has several intermontane areas of interior drainage which constitute completely closed hydrologic systems. The end points of drain- age in most of these basins are saline lakes or playas containing brines high in carbonate content. These brines have been derived principally by evaporative concentration of waters draining igneous rocks. Such waters are dominantly of a sodium carbonate compo- sition, because of precipitation of alkaline-earth car- bonate, and lack of sources of appreciable sulfate or chloride; some waters contain, however, significant amounts of anions in addition to CO;" and HCO;s~. In most natural waters, carbonate and bicarbonate are assumed to account for nearly all the alkalinity determined by titration with a strong acid (for ex- ample, H,SO,) to end points at pH 8.2 and pH 4.5, respectively (Rainwater and Thatcher, 1960, p. 93). But in the particular samples studied by this method, other bases, such as those formed by silica, boron, and phosphorus, and certain soluble organic compounds are titrated also, as evidenced by the form of the titration curves, and are included erroneously in the values for carbonate and bicarbonate. The titration end points in such solutions may vary significantly from pH 8.2 and 4.5, at least partly because high con- centrations of carbonate and the other weak bases tend to form a natural buffering system. In the analysis of brines containing appreciable car- bonate in the western Great Basin an attempt was made to assess the sources of error in the titration method. The distribution of carbonate and bicarbonate was obtained from potentiometric titration curves, and the sum of the two, calculated as total CO;, was com- pared with total CO; values determined by an evolu- tion method from a duplicate sample. Samples of brine were obtained from the Abert and Alkali Lake basins of south-central Oregon and from the Deep Springs and Honey Lake basins of eastern California. Carbonate plus bicarbonate ranged from 15 to 81 percent of the total anion equivalent content. Samples were collected and stored in polyethylene bottles. Most analyses were made within 3 months of the date of sample collection. Abert Lake is a large body of saline water in south- central Oregon. It occupies an eastern arm of the composite graben that constitutes the Abert-Summer Lake basin (Donath, 1962, p. 1), and is a remnant of a large pluvial lake that at one time covered much of the combined basin. Although during historical time the water surface of Abert Lake has varied con- siderably, a total area of 45 square miles, a mean depth of 3 feet, and a maximum depth of about 6 feet are probably close to average dimensions (A. S8. Van Denburgh, oral communication, 1964). The retreat of higher lake stages is marked by efflorescent crusts on the north side of the lake. One sample was obtained in this area adjacent to a brine pool maintained perennially by inflow from a small spring. The Alkali Lake basin is about 19 miles north-north- east of Abert Lake. The intermittent Alkali Lake itself lies in the southern part of its basin and consists U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D134-D137 D134 RETTIG AND JONES of a broad very shallow pond adjacent to several large cireular depressions known as "potholes" (Van Winkle, 1914, p. 115). These "potholes" contain highly con- centrated carbonate brines, apparently as a result of the rate of ground water discharge being approxi- mately equal to the rate of evaporation in the area. Honey Lake, the lowest part of a large basin of interior drainage in southeast Lassen County, Calif., covers an area of approximately 12 by 15 miles. The lake frequently dries up completely in late summer and even at highest stage has a maximum depth of only 4 or 5 feet. Surface waters of Honey Lake usually are dilute, but substantial salinity character- izes interstitial solutions of the sediments immediately beneath the present lake-bed surface. Deep Springs Lake (Jones, 1961, 1963; Peterson and others, 1963) is a small intermittent saline lake at about 5,000 feet elevation in northern Inyo County, Calif., about 35 miles west of northern Death Valley. About a third of the lake area is covered with porous layered saline crusts containing perennial interstitial brine. Major normal faulting at the mountain base east of the lake has formed a distinct trough contain- ing two sag ponds, one of which has no outlet at low stage. Carbonate spring waters from the fault zone feed the ponds and are also the principal source of flow into the lake. Carbonate species remain high in the ponds, whereas during periods of surface flow through marshes to the lake, total carbonate per- centage of spring waters drops, owing to mixing of waters, precipitation of solids, and loss of CO;. Actu- ally, sulfate is the dominant anion in the intercrustal brines of the lake. Alkalinity of brines from the western Great Basin areas was determined by both field and laboratory titrations. In most samples the field and laboratory values differed significantly, primarily because of tem- perature change with resulting CO; loss between time of collection and analysis. For example, the field determination of sample 3HL4 showed 6,470 parts per million total CO; compared with 5,940 ppm for the laboratory determination. For sample 3AK3 the field value was 77,300 ppm CO; and the laboratory value was 71,020. Only the laboratory titrations gave CO; results directly comparable to the values deter- mined by the evolution method. In the laboratory, titrations for total alkalinity were performed potentiometrically using a laboratory pH meter. The tip of the burette was kept beneath the surface of the sample, and the sample was constantly stirred in order to avoid high concentrations of acid in some parts of the beaker where free carbon dioxide might be released. Effervescence before the carbonate D135 end point is reached indicates that carbonate is being converted to free carbon dioxide and lost. Therefore the calculated value of bicarbonate will be low, though the determination of total CO; species as CO;,~" would still be valid. The strength of the titrant used was approximately 0.1N; stronger acid proved too likely to cause effervescence. Complete titration curves were prepared by plotting pH against milliliters of acid, as shown by the solid lines on figure 1. The points of maximum inflection were selected as the end points of the titration. Con- centrations of carbonate and bicarbonate so obtained were converted to equivalent CO; for comparison with total CO;, determined by the manometric evolution method. Total carbon dioxide by evolution was determined manometrically using a modification of the apparatus described by Pro and others (1959). By this method, carbon dioxide is liberated with addition of an excess of 1N sulfuric acid to the sample, in an evacuated system. The resulting change in pressure on a mer- cury manometer can be substituted in the ideal gas law equation, PV=$RT, and the equation solved for g, the weight of carbon dioxide, in grams. A modification of the evolution method was used to verify approximately the carbonate and bicarbonate values obtained by potentiometric titration. Sulfuric acid (0.1N) was added to the reaction flask in incre- ments of 5.0 ml, and the resulting manometer readings, in millimeters of mercury, were plotted as functions of the amount of acid added. The results are shown by the dashed lines of figure 1. There is a close simi- larity in the amount of titrant required to reach the inflection points in each of the two methods. Lack of better agreement probably is the result of (1) the use of a more dilute acid (0.1NV instead of 1N), which in the manometric determination requires a larger vol- ume, thus changing the calibration of the system; (2) inability to read the inflection points accurately; and (3) local loss of CO, during the titration. The carbonate and bicarbonate values derived from potentiometric titrations were compared with the total carbon dioxide, in parts per million, determined by the evolution method. The results are listed in the accompanying table on page D137. As indicated in the table, the percentage difference between results of the two methtods ranges from less than 1 percent to nearly 6 percent. This is not much greater than the reproducibility range found for the manometric method alone. In 6 of the 9 samples, the carbon dioxide values from the evolution method are greater than those calculated from the potentiometric D136 pH pH ANALYTICAL TECHNIQUES Potentiometric 6)- -10 BL- - 15 -I 20 3 |- - 25 A- K. 4s SAMPLE DL2J cx \ 1 | | | | | 35 0 10 20 30 40 50 60 0.09938 N H,SO,, IN MILLILITERS F: I I I I I I I -o SAMPLE DL39H 1 4 | | 1 | Potentiometric ~10 ~15 - 20 16 24 32 40 48 56 0.09938 N H,SQ,, IN MILLILITERS PRESSURE, IN MILLIMETERS OF MERCURY PRESSURE, IN MILLIMETERS OF MERCURY 10 I I I I 9 P 8 -o > CC 2 el & 7 -5 s : : LL Potentiometric o] el 6 ~i10 & & > < > s- -|15 = 15.5 Z o 4 |-- -| 20 & l 0 [ [+a Q. 34 --|25 2L- 1 - 30 SAMPLE DL2P \\~< 0 10 20 30 40 50 60 0.09938 N H,SQ,, IN MILLILITERS Fraur® 1.-Titration curves for three samples (DL2J, DL39H, and DL2P) of carbonate brines from the Deep Springs Valley, Calif. Dashed lines, results obtained by the mano- metric (CO; evolution) method; solid lines, results obtained by potentiometric titration. titration values. This suggests that interfering ions in these samples, at least, were not present in sufficient amounts to consume a significant quantity of titrant. Several sources of error are recognized in the use of the manometric apparatus. For the most highly concentrated samples it was necessary to use a 2.0-ml sample in order to keep the manometer deflection within scale; to measure out a 2.0-ml sample accu- rately is very difficult, especially when the sample must be exposed to the atmosphere as little as possible. Duplicate determinations of sample 3AK2B (90,900 ppm CO;) differed by 3.7 percent. In brines with relatively low total CO; content, errors may result from the inaccurate reading of very small deflections on the manometer. Duplicate determinations of sam- ple 3HL4 (5,720 ppm CO;) varied by only 0.5 percent, but in preliminary analyses of brines below 3,000 ppm in total CO;, variation greater than 10 percent has been observed. The precision of the total CO; deter- mination probably could be improved significantly by calibration of the apparatus with an optimum-size reaction flask for each concentration range. RETTIG AND JONES D137 Comparison of potentiometric titration and manometric (CO; evolution) methods for the determination of total CO; in brines of the western Great Basin Potentiometric titration Manometric measurement Dissolved Percent Sample solids (ppm) deviation! CO;~* (ppm) HCO! CO;~+HC0;-! Evolution (ppm) (cale. as ppm (ppm total CO) CO)) Deep Springs Lake, Calif.: brine}.......:_.....l.l.ell.li._-.L.cll. 332, 000 20, 800 6, 580 20, 050 21, 000 -4. 5 DL2P (intercrustal 316, 000 22, 400 2, 000 17, 840 18, 700 -4. 6 DEHSONM (Gac 337, 000 66, 100 3, 630 51, 120 54, 300 -5. 9 Alkali Lake basin, Oregon: SAK2BApotholc) ...-... OLL den 270, 000 113, 400 15, 400 94, 200 90, 900 +8. 6 SAKO (Alkall Lake pond). 297, 000 94, 300 2, 520 71, 020 72, 000 -1. 4 Honey Lake, Calif.: SHLI (pit in lake bed).... 54, 300 8, 000 5, 470 9, 810 10, 400 -5. T 3HL4 (pit in lake bed near Amedee Springs) _________- _- 25, 100 5, 320 2, 830 5, 940 5, 720 +38. 8 Abert Lake, Oreg.: SABS (AIDert LARC) ss masa 38, 400 6, 880 3, 640 7, 660 7, 640 +0. 3 SABL1-2 (brine pit, north end) ___.. 98, 300 16, 100 9, 680 18, 780 19, 000 -1. 2 ' Percent deviation= W X 100. In the potentiometric titration, a major possibility REFERENCES for error lies in the selection of the proper inflection points. The inflection points of the samples in the table were all quite sharp and could be determined with reasonable certainty within +1 ml, which repre- sents a percentage error of about +2 percent. But in at least one sample (not reported here), the upper part of the titration curve was sufficiently flat that the choice of an inflection point involved considerable uncertainty. Presumably the bicarbonate+ carbonate end points are obscured by the titration of other weak bases. In such samples the manometric method prob- ably comes much closer to the determination of the true total carbon dioxide present. In the brines of the western Great Basin, the difference between total CO; values obtained by the two methods probably can be applied in large part to the correction of the car- bonate end point, where weak base interference is most pronounced. Donath, F. A., 1962, Analysis of basin-range structure, south- central Oregon: Geol. Soc. America Bull., v. 73, no. 1, p. 1-16. Jones, B. F., 1961, Zoning of saline minerals at Deep Spring Lake, California: Art. 88 in U.S. Geol. Survey Prof. Paper 424-B, p. B199-B202. 1963, The hydrology and mineralogy of Deep Springs Lake, Inyo County, California: Johns Hopkins Univ., unpub. PhD. dissert., 238 p. Peterson, M. N. A., Bien, G. S., and Berner, R. A., 1963, Radio- carbon studies of recent dolomite from Deep Spring Lake, Calif.: Jour. Geophys. Research, v. 68, no. 24, p. 6493- 6505. Pro, M. J., Etienne, Arthur, and Feeny, Frank, 1959, Determi- nation of carbon dioxide in wines using a vacuum system : Jour. Assoc. Official Agr. Chemists, v. 42, p. 679-683. Rainwater, F. H., and Thatcher, L. L., 1960, Methods for col- lection and analysis of water samples: U.S. Geol. Survey Water-Supply Paper 1454, 301 p. Van Winkle, Walton, 1914, Quality of the surface waters of Oregon: U.S. Geol. Survey Water-Supply Paper 363, 137 p. GEOLOGICAL SURVEY RESEARCH 1964 MAPMAKING APPLICATIONS OF ORTHOPHOTOGRAPHY By MARVIN B. SCHER, Washington, D.C. Abstract.-Orthophotographs, which present images in true planimetric position, are useful tools in planimetric and topo- graphic mapping. They can be used to evaluate the horizontal accuracy of maps, to provide new data for revising existing topographic maps, and to serve as a source of information for compiling planimetric maps. Additionally, a map product suitable for publication may be prepared by proper carto- graphic treatment of mosaicked orthophotographs at a lower cost than for planimetric compilation. Orthophotographs furnished to geologists, foresters, hydrologists, and engineers have proved to be of great value in alleviating field mapping problems caused by lack or inadequacy of map coverage. Orthophoto- graphs are uniform-scale photographs prepared from conventional perspective aerial photographs by means of an Orthophotoscope. All features in such photo- graphs are shown in their correct relative positions and at correct relative distances from one another. The Orthophotoscope may be described as photo- grammetric restituting enlarger that corrects distortion by magnifying the different images on a perspective photograph inversely as their scale differences (Scher, 1962). Orthophotographs retain detail, such as indi- vidual trees appearing on the conventional perspective photographs from which they are prepared, thereby simplifying the problem of recording scientific field observations in their correct orthographic positions. Methods for effectively applying orthophotography in a planimetric or topographic-mapping program are being investigated. Though incomplete, these studies disclosed several practical uses of this type of product in mapmaking operations and have indicated that, with proper cartographic treatment, a photographic type of map prepared directly from the orthophoto- graphs may be acceptable to the map-using public. EXPERIMENTAL APPLICATIONS Because the geometrically faithful stereoscopic model is already available to the mapmaker, the geo- metric qualities of orthophotographs do not present a unique advantage to him. However, other character- istics of orthophotographs are decidedly different from those of stereoscopic models formed in precise plotters. For example, an orthophotograph is a permanent rec- ord that can be reproduced on a variety of materials, and it is readily portable and easily stored. Certain mapping procedures and operations may benefit from these distinguishing characteristics of orthophoto- graphs. Orthophotographs have been applied in map-revi- sion experiments to evaluate maps of doubtful hori- zontal accuracy and to determine whether the existing map is sufficiently reliable to serve as a base for adding new map data. Orthophotographs have also served as a source of new map data and as a guide to posi- tioning of the data. The feasibility of compiling the planimetry (the plan details) of an urban area from a 1:24,000-scale orthophotomosaic was the objective of a recent research project. For this experiment, a continuous-tone diazo orthophotomosaic was printed on a white scribe- coated scale-stable plastic. This research project demonstrated that the direct scribing of the plani- metric information on this kind of base is entirely feasible. The accuracy and completeness of the plani- metry scribed on the orthophotomosaic compared favorably with the accuracy and completeness of that compiled by stereophotogrammetric procedures. The total time for the experimental compilation was about 10 percent greater than for standard compilation. However, the Orthophotoscope operating time was less than one fourth that of the stereoplotter operating time. It may be concluded, therefore, that orthopho- tography offers a significant advantage in compiling the planimetry for areas of dense cultural detail by permitting more efficient use of expensive instruments. In another experiment, the mapworthy planimetry on a similar diazo print of the same orthophotomosaic¢ U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D138-D140 D138 GEOLOGICAL SURVEY PROFESSIONAL PAPER 501-D PLATE 1 29°57 30" 55° 37°17'308 A part of the experimental orthophotomap of the Roanoke, Va., 7-minute quadrangle; seale 1:24,000. SCHER was compiled in the field. The objective of this study was to determine what advantages accrue when a source of accurately positioned planimetric data, for- merly available only in an accurate stereoplotter, is made portable and readily available to a fieldman. In domestic mapping operations, field inspection and sur- veying are usually needed to complete and correct planimetric information compiled in the office by stereophotogrammetric methods. In searching for the errors and omissions of a photogrammetric compila- tion, considerable time and effort must be spent in reviewing features that have already been plotted and portrayed correctly. To reduce the time spent in the field to a minimum, the planimetric detail that could be photoidentified with certainty was scribed in the office before the manuscript copy was sent to the field. Using the orthophotomosaic and working without an assistant, the field engineer combined the field review and the compilation of the more obscure planimetry into one efficient operation. The fruitless effort involved in checking complete and correct information was elimi- nated. THE ORTHOPHOTOMAP-A FINAL MAP PRODUCT Studies to ascertain the cartographic treatment of orthophotographs necessary to provide a map suitable for publication have led to the preparation of an ex- perimental orthophotomap. This orthophotomap is D139 an orthophotomosaic prepared in quadrangle-map format, with a limited amount of added cartographic symbolization and marginal information, and litho- graphed in several colors. The recent development of the photoline-phototone photographic printing tech- nique by the U.S. Army Map Service (Wickland, 1964) was most timely for this purpose. In this tech- nique, two negative transparencies are prepared from a continuous-tone negative of the orthophotomosaic. One of these, the photoline negative, is printed in a manner that enhances all image edges and suppresses the remaining detail (Clarke, 1962). A positive pre- pared from this negative approaches a line drawing in appearance (fig. 1, right). The other transparency, the phototone negative, retains the continuous-tone appearance but actually contains patterns of randomly spaced and irregularly shaped dots. These negatives are both suitable for preparing lithographic press- plates. The orthophotomap of the Roanoke, Va., T/,-minute quadrangle was the first to be prepared (pl. 1). The density of planimetric features and the considerable relief in the area were appropriate for the purposes of this research. Color-separation plates were pre- pared for the limited amount of cartographic symbol- ization to be included in the orthophotomap. From these plates and the photoline and phototone trans- parencies, 28 different 6-color lithographic renditions of the orthophotomap were printed. In the rendition 3 p toja ‘d "" mep ro bys... " Autry 31 My. fas is Fiaur® 1.-A portion of an orthophotomosaic, left, of Roanoke, Va., and a photoline positive, right, of the same area, prepared from the same orthophoto negative. T42-652 0O-64--10 The scale of both is about 1: 12,000. D140 considered most effective, the photoline images were printed in dark gray, the phototone images in gray green, the principal roads and their numbers in red, the major hydrographic features in blue, the wooded areas in green, and the names data and marginal in- formation in black. This form of map presentation is particularly ad- vantageous in densely settled areas and, conversely, in areas of very sparse cultural detail. In urban areas the orthophotomap minimizes the need to delineate and scribe the congested planimetric detail, there- by offering savings in cost as compared with the standard planimetric compilation. In areas where little planimetric information would be shown on the standard line map, such features as lone trees or bushes and cattle trails, generally ignored as map- worthy features, are readily identifiable on the ortho- photomap and are usable as landmarks. An experi- mental orthophotomap of such an area in Arizona is now being prepared. CARTOGRAPHY Public acceptance of the orthophotomap will be influenced by the map user's willingness to assume the task and responsibility of photointerpretation required in using this product. It is quite possible that map users have become too accustomed to the simplicity of line drawings and the clarity of cartographic symbols. The amount of cartographic symbolization that should be added to an orthophotomap to satisfy public needs has not been finally determined. It is expected, how- ever, that the cost of this additional cartographic work will not significantly reduce the advantages of orthophotomaps. REFERENCES Clarke, A. B., 1962, Edge isolation in photogrammetry and geologic photography : Art. 166 in U.S. Geol. Survey Prof. Paper 450-D, p. D160-D163. Scher, M. B., 1962, Research activity with the U-60 ortho- photoscope: Art. 57 in U.S. Geol. Survey Prof. Paper 450-B, p. B135-B137. Wickland, L. R., 1964, Map substitute products: Am. Cong. on Surveying and Mapping Mtg., Washington, D.C., March 16-19. GEOLOGICAL SURVEY RESEARCH 1964 GROUND-WATER CONDUITS IN THE ASHLAND MICA SCHIST, NORTHERN GEORGIA By CHARLES W. SEVER, Quitman, Ga. Work done in cooperation with the U.S. Atomic Energy Commission Abstract.-Although joints in the rocks govern the course of streams that drain outcrops of the Ashland Mica Schist, they are not the principal conduits through which ground water moves toward the streams. Instead, ground water moves mainly through planar openings parallel to the bedding, schistosity, and axial-plane cleavage of the schist. The Ashland Mica Schist of Precambrian age crops out within the Georgia Nuclear Laboratory (GNL) site in Dawson County, Ga., about 50 miles north of Atlanta. This formation, a thick sequence of biotite schist interbedded with biotite gneiss, is complexly folded into tight overturned isoclinal folds in which the bedding, schistosity, and axial-plane cleavage are parallel, or nearly so. These structural features can- not be distinguished one from another except locally on the nose of folds. They strike about N. 60°E. and dip about 60° SE. except where bedding and schis- tosity are wrapped around the nose of folds. Two conspicuous sets of high-angle joints trend N. 30° W. and N. 54° W. and intersect the strike of the schist at angles of about 90° and 66°. The crystalline rocks are deeply weathered and are mantled by a thick saprolite zone. On hills the sapro- lite generally is about 50 feet thick, although in one well it exceeded 137 feet in thickness. Fresh rock crops out in valleys, drains, and deep road cuts, and a few small streams are steeply incised in the bedrock. Bedding, schistosity, jointing, and at many places cleavage, are preserved in the saprolite beneath the soil zone. The land surface is deeply dissected; ridge crests are sharp, and slopes are steep. Slopes on the southeast sides of valleys generally are steeper than slopes on the northwest sides. During a hydrologic investigation at the GNL site Stewart and others (1964) found the average porosity of saprolite to be much greater than the average porosity of fresh crystalline rock and indicated that the transition zone between saprolite and fresh rock was the most permeable zone. Inasmuch as all the water percolating downward through the saprolite cannot flow into the few openings available in the fresh rock, most of it accumulates in the transition zone. Accumulation of the water steepens the hydrau- lic gradient, causing the water to be shunted laterally toward discharge points along surface drainage courses. Laboratory tests show that the permeability due to interstitial voids is too small to account for the amount of water transmitted by the Ashland Mica Schist; thus the principal conduits for ground-water move- ment must be of either the tubular or planar type. Tubular openings, such as are common in some lime- stone, generally are the result of solution activity and are unlikely in schist; furthermore, none were ob- served to intersect exposed rock surfaces in the area. On the other hand, the Ashland Mica Schist has abundant planar openings that have resulted from the development of jointing, schistosity, and axial-plane cleavage during metamorphism and orogenic deforma- tion of the original sedimentary rocks. Moreover, un- loading and weathering have widened these openings to a probable depth of several hundred feet. In the hydrologic investigation of the GNL site, R. F. Carter (Stewart and others, 1964) observed that the base flow of streams varied considerably with their orientation (fig. 1). As the pattern of surface drain- age reflects the systems of high-angle joints in the U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D141-D143 D141 D142 84° EXPLANATION | aa|_ 24) | Ashland Mica Schist 024 Streamflow measuring point Circle equals 0.5 cubic feet per second per square mile; flow at points shown on map is proportional to area of circle; number indicates number of measuring | ha (.. 3 Contact & & C_. | Area of figure 2 0 2000 4000 6000 FEET fern thorne FiaurE 1.-Map of the Georgia Nuclear Laboratory site, showing amount of base flow per square mile of drainage grea for streams draining outcrops of the Ashland Mica chist. Ashland Mica Schist, Carter postulated that joints in the rocks are the principal conduits through which ground water moves. A cone of depression that develops around a pumped well tapping steeply dipping planar openings should be elliptical with the long axis parallel to the strike of the planar openings. It should have a steeper gradient along the dip of these openings. On the updip side of the cone the hydraulic gradient would be more nearly parallel to the planar openings and water could move along the planar openings toward the pumped well. But on the downdip side of the cone the hydraulic gradient would be nearly normal to the planar openings and the water would have to move by an indirect path to reach the pumped well. A steeper hydraulic gradient would be required to move the water normal to the planar openings than would be required to move water along (through) the planar openings. If the high-angle joints were the principal conduits for ground-water movement, the cone of depression around a pumped well that taps the Ashland Mica Schist necessarily would be elliptical in plan view GROUND WATER and the longer axis of the ellipse would trend N. 30° W. to N. 54° W. in line with the strike of the joints. However, as observed when a well was pumped during aquifer tests at the GNL site, the water-level draw- down in the more than 40 observation wells indicated that the longer axis of the elliptical cone of depres- sion was in line with the strike of the schist, roughly normal to the strike of the principal joint sets (fig. 2). The cone of depression had a steeper gradient south- east of the pumped well than northwest, indicating that the well was draining water from rocks northwest of the well faster than from rocks southeast of the well. A hydraulic barrier located immediately south- east of the pumped well could cause this effect, but a geologic investigation disclosed no such barrier. When infiltration tests were made on the GNL site (Stewart and others, 1964) the resulting ground-water mound, or cone of impression, also was found to be elliptical in plan view and to have its longer axis in line with the strike of the schist. The shape and orientation of the cones of depression and impression indicate that openings along schistosity, cleavage, and bedding planes and not joints are the principal conduits through which ground water moves toward discharge points. se EXPLANATION \ 1096 --- Water-table contour Dashed where poorly controlled. Contour interval 2 feet; datum, mean sea leve! Pumped well Modified from Stewart and others (1964, 50 100 150 200 FEET 0 At Fraur® 2.-Water-table contour map at end of 30-hour pump- ing test, June 19, 1958, Georgia Nuclear Laboratory, Dawson County, Ga. SEVER stream an planar open Direction of stream Fraur® 3.-Relation between direction of streamflow and the percentage of planar openings transected per unit length of stream. If the planar openings are assumed to be parallel, or nearly so, and are distributed uniformly through- out the schist, the amount of ground water discharged into a given reach of a stream would be related directly to the angle between the direction of streamflow and the strike of the planar openings. As shown on figure 3, the greater the angle between them, the greater the percentage of openings transected per unit length of stream. The relation of ground-water discharge to the strike and dip of the schist and the strike of the principal joints is illustrated on figure 4. Ground-water dis- charge is greatest to streams flowing normal to the strike of the schist and least to streams flowing normal to the strike of the joints. This is precisely the rela- D143 Average base- / flow discharge Z o w o ol & Q < 5 « oH o > & o 1.0 ¢ yeasuring-point No. i & 11.0 2 |" 24 o & 1.1 +1.2 Length of line indicates amount of ground water discharged into stream, in cubic feet per second per square mile of drainage area Modified from Stewart and others (1964) 4.-Relation between base-flow discharge to streams and direction of the major axis of stream basins at the Georgia Nuclear Laboratory, Dawson County, Ga. tion that should be expected if the principal ground- water conduits are planar openings oriented parallel to schistosity and cleavage in the schist. Further studies will be needed to determine which type of planar opening-schistosity, axial-plane cleavage, or bedding plane-forms the principal conduit. REFERENCE Stewart, J. W., Callahan, J. T., Carter, R. F., and others, 1964, Geologic and hydrologic investigation at the site of the Georgia Nuclear Laboratory, Dawson County, Ga.: U.S. Geol. Survey Bull. 1133-F. [In press] GEOLOGICAL SURVEY RESEARCH 1964 TEMPERATURE AND CHEMICAL QUALITY OF WATER FROM A WELL DRILLED THROUGH PERMAFROST NEAR BETHEL, ALASKA By ALVIN J. FEULNER and ROBERT G. SCHUPP, Anchorage, Alaska, Palmer, Alaska Work done in cooperation with the U.S. Air Force, Alaskan Air Command Abstract.-A water well drilled on the Kuskokwim delta near Bethel, Alaska, obtained potable water beneath 603 feet of permafrost. Temperature of the subpermafrost water was 33.2°F. Chemical similarity of well water to water from the Kuskokwim and Yukon Rivers suggests recharge from either of these rivers through unfrozen zones in the delta deposits. A water well, 622 feet deep, drilled in delta deposits of the Kuskokwim River at a military installation near Bethel (fig. 1) produced water from beneath permafrost 603 feet thick. Located on the older part of the delta, which has been trenched by modern streams, the well site (well 2) is about 175 feet above mean sea level (fig. 2). According to Waller (1957, p. 4) the area is underlain by clay, silt, sand, and some gravel, and the deposits generally are coarser with depth. Waller (1957) also reports that the deposits of coarse sand and fine gravel penetrated in the drill- ing of wells in and near Bethel are lenticular and cannot be correlated from one well to another. WELL DRILLING AND TESTING The materials penetrated in drilling well 2, as re- ported by the U.S. Army Engineers, Alaska District, consist of interbedded sandy silt, silty fine sand, fine sand, and pebbly sand (fig. 3). All these materials are believed to be of deltaic origin. The depth to which the deltaic deposits extend at the well site is not known, but in the general vicinity of the well the total thickness of the deltaic deposits ranges from 450 to nearly 1,000 feet (T. L. Péwé, oral communication, 1963). Permafrost at well 2 extends to a depth of 603 A4RCPHQ Barrow _ OCR A N CEUKCRT isso cet BAP 162+ «~ 16° SEa e WV¥W Cave ( ise» $1 \ JN\ '8bur | N Mm“ 68.3“) M R‘A NS fl es \¢”’° fa [£91 (Riis. _ T as; [ ue PA C (f f 100 200 MILES Fiaur® 1.-Map of Alaska, showing areas referred to in text. feet. When the drill reached the base of permafrost, a slurry of water, sand, and wood fragments surged up the hole, filling it to within about 350 feet of the surface. One fragment of wood, believed to have come from just below the base of permafrost, has been dated by the carbon-14 method as older than 34,000 years (Ives and others, 1964, sample W-1287). After well 2 had been drilled to a depth of 662 feet, the interval between 626 and 651 was screened, the hole was plugged back to the bottom of the screen, U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D144-D148 D144 FEULNER AND SCHUPP D145 EXPLANATION Flood plain Delta surface Airport well a 200)- 100 SEA LEVEL -100 -200 = 300 -400 -500 Unfrozen zone Ya 1 MILE Kuskokwim River - A' Assumed unfrozen zone FicurE 2.-Map showing location of wells near Bethel, and cross section showing thickness of permafrost (diagonal lines) in the area. f and the well was developed by surging and bailing. Following the development of the well, the static water level stood 136 feet below land surface. Because the water level stood so high in the permafrost (more than 450 feet), it was necessary to introduce about 1%, gallons per minute of warmed water into the well to prevent freezing. In early January a pump having a capacity of 12 gpm was installed, and by continuous pumping the water in the well was kept from freezing. Although the capacity of the pump was small, the pump was used in making a preliminary test. After the well had been pumped continuously for 64 hours at a rate of 12 gpm, the water level stood at 146.7 feet below land surface, or 10.7 feet below static level, indicating a specific capacity of about 1 gpm per foot of drawdown. At intervals of 12, 24, and 36 hours after completion of the preliminary test, the temperature of the water in the well was measured at increments of depth from the water surface to the base of the screen. A Whit- ney underwater thermometer, rated accurate to within 0.1°F, was used to make the measurements. The three sets of water temperatures were averaged and are pre- sented on figure 3. The greatest deviation from the average of the three temperature determinations at any given depth was 0.1°F. The average temperature of water opposite the permafrost zone was 31.8°F, but the average of the three readings at the different depths within this zone ranged from 31.8° to 31.9°F. All temperatures below a depth of 605 feet were the same on all three readings. The maximum water tem- perature recorded was 33.2°F at a depth of 620 feet. The presence of a solid casing rather than a screen at this depth is not believed to have had any significant effect in the temperature determinations. The temperature at which water in the well would freeze inward opposite the permafrost zone was not determined. However, during construction of the well, the water froze inward from the casing during the night when drilling was not in progress. Collars of ice, more than an inch thick, formed in the casing at a depth of about 300 feet during the period between midnight and 8 o'clock in the morning. After com- pletion of drilling and development of the well, con- vection currents between warmer water at the base D146 TEMPERATURE, IN Well I; DEGREES FAHRENHEIT 31.5 32.0 $2.5 33.0 33.50 - - 100 Static | water- level a w |-200 8 < Pa c > w o 4 \\ Fine sand - -300 3 $ m i Sand and a { pebbles a -] Fine sand i- ' m) - |- - -400 it £ 3 i- » a. Silty fine 3 * - - sand - -500 I | Base of - | hal perma~~~~+----1 Sand and 3 - 600 frost - pebbles T Fine sand and ples pebbles N :- Silty fine sand 662 Fraur® 3.-Generalized lithologic log and water-temperature log of deep well near Bethel, Alaska. Temperature measure- ments made on January 21 and 22, 1963. Each circle on the water-temperature log indicates a separate temperature measurement. of permafrost and the cold water above may have kept the water from freezing inward during the period in which the temperature measurements were made. After the last set of temperature measurements were made, warm water from storage was again introduced into the well to prevent freezing. About a week after the conclusion of the prelimi- nary pumping test a larger pump was installed and a second pumping test made. This test lasted only 10 hours because the electric water-level tape, used tp measure depth to water, became entangled in the pump column. A third and final test was begun 2 days later, and pumping continued for 33. hours. During this test the average rate of pumping was about 45 gpm and the drawdown was about 40 feet, again indicating a specific capacity of about 1 gpm per foot of drawdown. GROUND WATER PERMAFROST In the immediate vicinity of Bethel the base of permafrost is about 350 below sea level (Waller, 1957, fig. 3). The greater thickness of the permafrost in the vicinity of well 2 is probably due to the fact that the ground surface at the site is about 150 feet higher than at Bethel. Beneath rivers and old meanders, and in areas where tributaries have flowed in com- paratively recent times, the permafrost has partly thawed from the surface downward, or has been re- moved entirely by downward thawing. At the site of well 1, about 1,500 feet south of well 2, permafrost was reported at depths of from 22 to 42 feet and from 280 to at least 378 feet, where drilling was stopped. The well was backfilled to 202 feet, and the zone be- tween 192 and 202 feet was screened and developed. According to Waller (1957, p. 5), the report of perma- frost from 22 to 42 feet is questionable. Well 1 is in a depression that is believed to have been the channel of a fairly sizable stream which fed the Kuskokwim River within comparatively recent times. This thawed zone is shown on figure 1 between well 2 and the air- port well. Elsewhere in the vicinity, permafrost ex- tends from near ground surface to 350 to 425 feet below sea level (fig. 2). WATER QUALITY Three water samples were collected from well 2 for chemical analysis (see accompanying table). The first of these samples was a bailer sample taken when water and sand first entered the hole from a depth of 603 feet. The second was a bailer sample collected about 8 hours after the conclusion of the preliminary pumping test. The third sample was collected about 1 hour before the conclusion of the final pumping test. The analyses show that the well yields a bicarbonate water in which calcium and magnesium are the pre- dominant cations. The dissolved-solids content ranges from 123 to 172 ppm. Also included in the table are analyses of water from well 1, from a 436-foot well at the Bethel airport (fig. 2), from the Kuskokwim River upstream from Bethel, and from the Yukon River. The analysis re- ported for the Kuskokwim River represents an average of 11 samples taken during 1962 at Crooked Creek, about 145 miles northeast of Bethel, and the analysis for the Yukon River represents an average of 12 sam- ples taken during 1962 at Rampart, about 480 miles northeast of Bethel. FEULNER AND SsCHUPP Chemical analyses of water from wells near Bethel and from the Yukon and Kuskokwim Rivers [Mineral constituents in parts per million. . Analyses by the Quality of Water Branch, U.S. Geological Survey, Palmer, Alaska] D147 z fig Hardness | p E 6 1:8 as CaCO; 5 e 3 l § 3&8 €8 Date of ?t Lats] 1 s |R [ ~ | 2) 1 3% 4 | 4g Source of water sample collection | @ 3 | S | § 21 3 112 1 $ 12g zang | 82 2 | a | £ § lo 1 F131 C igs? 14 3 | ff ehagagagassszfigagéa [| ELE&lilfPlili:{ ili / |; f Targ | 34 f els )f 3 [&C )R) $ Well 2, 651 feet deep: Bailer sample from depth of 603 feet, before completion of -¥. 0|0. ___| 2815. 0|12. 0| 5.3 157) 7. O11. O| 0. 0| 0. 172) 118)... 279) 8.0 ...s Bailer sample 8 hours after end of first pumping test. 1/21/63 9. 8| . 050. 33] 23) 8.3) 4.0] 2. 2) 128] 3. 0| 4. 0 128] 105)... 206) 7.8| 10 Pump sample near end of third pump- me 1/31/63|24. 0| . 05|____| 19/18. 0| 3.7) 2. 2) 123) 1. 0| 4. 0 127] 100}. ... 18918. 0... Well 1, 202 feet deep, 1,500 feet south of well 2..-........._. tk 12/29/60|34. 0| . 87) . 35) 35) 4.8| 8.8] 1. 1| 138] 4. 0| 4. 0 155 108). .... 216) 7. 1| 20 Airport well, 436 feet deep, 2.8 miles west of 6/ 9/58|25. 0| . 31| . 02] 25] 7.4) 4.4] 1. 2) 116) 3. 5) 3.5 127! 98|.... 204] 6. 0|_ __. Yukon River at Rampart, average of 12 analyses.. 1962) 6. 7] .Os|____| 32) 8.6) 2. 6) 1.7 10528. 0) 1.3 1. 192] 111} 251 210 8.0 25 Kuskokwim River at Crooked Creek, aver- age of 11 analyses____. 1902) 8. 25) 5.2] 1.8 1.1; 8917.0 .6 103] 85) 12; 181} 7.8) 15 D148 0.5 GROUND WATER 98 10 15 20 25 Na +K T T I I T CI HCO; SO; CO; e 0 o p Bailer sample from depth of 603 feet, well 2, November 27, 1962 Bailer sample 8 hours after pre- liminary pumping test, well 2, January 23, 1963 Pump sample near end of third pumping test, well 2, January 31, 1963 Sample from well 1, December 29, 1960 Sample from well at Bethel Airport, June 9, 1958 Average of 11 samples from Kuskokwim River, 1962 Average of 12 samples from Yukon River, 1962 T L 1 1 1 I 2.5. ' 2.0 1.5 : 1.0.0.6 CATIONS, IN EQUIVALENTS PER MILLION Figur® 4.-Chemical quality of Kuskokwim River water at C water at Rampart. 1 1 1 1 08 1.0 15 20 . 2.5 ANIONS, IN EQUIVALENTS PER MILLION ground water in the Bethel area, rooked Creek, and Yukon River X Diagramatic representations of the water analyses (fig. 4) show that 8 hours after comflletion of the preliminary pumping test, water from well 2 was generally similar to that from other wells in the area and to average water from the Kuskokwim and Yukon Rivers. The possibility of recharge from either river through unfrozen zones upstream from the Bethel area has been postulated by Waller (1957, p. 7). Analyses of water from well 2 suggest that the sample taken immediately after drilling may be water concentrated by freezing. Similar, more pronounced, changes have been noted elsewhere in Alaska (Feulner and Schupp, 1963). The water from well. 2 is of good quality and generally is suitable for domestic or in- dustrial use. REFERENCES Feulner, A. J., and Schupp, R. G., 1963, Seasonal changes in the chemical quality of shallow ground water in north- western Alaska: Art. 52 in U.S. Geol. Survey Prof. Paper 475-B, p. B189-B191. Ives, P. C., Levin, Betsy, Robinson, R. D., and Rubin, Meyer, 1964, U.S. Geological Survey radiocarbon dates VII: Am. Jour. Sci., Radiocarbon Supp., v. 6. [In press] U.S. Geological Survey, 1963, Quantity and quality of surface waters of Alaska, 1962: U.S. Geol. Survey, Water Ré- sources Div., Basic Data Release, 138 p. Waller, R. M., 1957, Ground water and permafrost at Bethel, Alaska: Alaska Dept. Health, Section of Sanitation and Engineering, Water Hydrological Data Rept. 2, 11 p. GEOLOGICAL SURVEY RESEARCH 1964 HYDROGEOLOGIC RECONNAISSANCE OF THE REPUBLIC OF KOREA By W. W. DOYEL and R. J. DINGMAN, Washington, D.C., Lawrence, Kans. Work done under the auspices of the Agency for International Development, U.S. Department of State Abstract.-The Republic of Korea is underlain largely by metamorphic and intrusive igneous rocks which generally yield only small amounts of water from the weathered zone. Present ground-water supplies, mostly from unconsolidated deposits in the river valleys and coastal flatlands, can be ex- panded considerably. The Republic of Korea} (fig. 1) is a country in which approximately 25,000,000 persons are subsisting on a land area (96,929 square kilometers) about the same size as that of the State of Indiana. Their major occupation is the cultivation of rice with which to feed the rapidly increasing population. Rice is grown in small plots, or paddies, which are flooded during the growing season principally with water diverted from streams. A severe drought during the spring of 1962 resulted in poor crops and stimulated interest in the possibility of developing ground water for supplemental irrigation. At that time no organi- zation in South Korea was carrying on systematic ground-water investigations nor were there personnel, either local or foreign, qualified to undertake the work. As a result, the Agency for International Develop- ment, U.S. Department of State, requested the U.S. Geological Survey to make a ground-water recon- naissance and evaluate current water-supply problems. The work was done during January-March 1963. The study revealed that ground water is used for domestic, municipal, and industrial supplies and, to a lesser extent, for irrigation but that development of this resource has proceeded with very little scientific 1 The official designation, Republic of Korea, is used interchange- ably with ROK, South Korea, and Korea in accordance with common usage. All refer to that part of the Korean Peninsula south of the demilitarized zone separating the Republic of Korea from the northern, communist-controlled Peoples Republic of Korea or North Korea. guidance or direction. Recognizing the importance of ground-water resources and the need for their proper management, the Japanese initiated in the late 1930's a comprehensive investigation of the ground- water resources, but the program was halted abruptly by World War II and was not resumed after the war. Since World War II, water wells have been drilled by the U.S. Army, U.S. Operations Mission to Korea, drilling contractors, and Republic of Korea agencies, but largely for exploitation rather than for investiga- tion. Although many satisfactory supplies have been developed, very little information has been obtained regarding the overall availability and the quantitative limits of the ground-water resources. The Republic of Korea is mountainous and is cut by steep-walled river valleys and some wider rift-type structural valleys. Most of the country has an average annual rainfall of more than 1,000 millimeters; the annual precipitation at Seoul and Pusan averages 1,254 and 1,403 mm, respectively. Rainfall is heaviest dur- ing the summer months. Igneous and metamorphic rocks are exposed throughout most of the country (fig. 2). Metamor- phism has largely destroyed the primary porosity in the sedimentary rocks and, in general, no important secondary porosity has developed. The thick layer of weathered material that mantles these rocks through much of the country has sufficient permeability to sustain dug wells for domestic and rural farm use. Jointing and faulting, although present, have not resulted in any effective porosity. Small springs are found in the higher areas but usually flow only dur- ing, and for a short time following, the rainy season. Most of the springs occur at the contact of the weath- ered and unweathered rock. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D149-D152 D149 D150 45° 120° 125° 130° GROUND WATER 135° 145° 1 I J Vladivostok, 140° & U.S.S.R. YELLOW SEA fifg />shanghai 30° Mercator Projection Ficur® 1.-Map showing location of the Republic of Korea (diagonal lines). Mesozoic rocks consisting of shale, sandstone, and siltstone are present in the southeastern part of the country. They have a reported maximum thickness of 20,500 meters in the Taegu area (Kobayashi, 1953, p. 233) and are gently folded. The axes of the folds are oriented in a general northwest direction, and the rocks are cut by faults trending in the same direction. The nature of the rocks and the structural features in the Taegu area suggest that the rocks contain ground water under artesian conditions (fig. 2). However, exploratory drilling would be required to determine the availability of artesian water supplies. Unconsolidated Pleistocene and Recent alluvial de- posits resting on bedrock underlie the floors of the steep-walled flat-bottomed valleys. The broad flat- lands along the west coast of the country also are underlain by unconsolidated sediments that rest on bedrock. Hills of intrusive and metamorphic rocks projecting upward through the coastal unconsolidated sediments indicate that the bedrock surface is irregular and probably was produced by erosion. The alluvial and coastal deposits are not only the current source of most of the large ground-water supplies but also the best potential source; their areal distribution is shown on figure 2. Present-day deposits in stream valleys consist mostly of sand and silt. Gravel is being deposited by streams Middle and late Pleistocene and Paleozoic and Mesozoic Recent early Mesozoic C. (% EXPLANATION Unconsolidated alluvial and coastal-plain deposits Moderately to highly permeable; yield water freely to wells. Small areas omitted Consolidated marine and non- marine sedimentary rocks Low to moderate permeability. Might yield artesian water in Taegu area Igneous and metamorphic rocks Yield sufficient water for domestic and stock supplies from weathered mantle. Includes small areas of Tertiary rocks Contact FiraurE 2.-Explanation. DOYEL AND DINGMAN D151 129° 130° 126° 127° . YELLOW SEA | | Base from U.S. Army Map Service Japan Geology from Geological Survey of Korea Road Map, scale 1:1,000,000, sheet 4, geologic map (1956), scale 1:1,000,000 Series L302 20 0 | 80 MILES cla Lr Ld L 1 | 210 (I) f | 8|0 KILOMETERS L. L_4 1 2.-Geologic map showing areas of ground-water availability in the Republic of Korea south of the 38th parallel. D152 at higher elevations only, mostly in and adjacent to the high chain of mountains that extends southeasterly across South Korea. The streams carry heavy loads of sediment during floods, and the major streams are gradually aggrading their lower reaches. Deltas are being built by streams discharging into the Pacific Ocean along the south coast and into the shallow Yellow Sea along the west coast. Some information regarding the nature and thick- ness of the unconsolidated deposits and the occurrence of ground water in them has been obtained as a result of the various development programs. In the drilling of wells, bedrock commonly is reached at depths of less than 35 m, although one well drilled by the U.S. Operations Mission to Korea near Changhang was bottomed in valley-fill deposits at a depth of approxi- mately 75 m (M. K. Fletcher, oral communication, 1963), and several wells have been drilled 45 to 60 m into unconsolidated sediments along the west coast. Owing to the irregularity of the bedrock surface, bed- rock may be reached at depths of 3 to 5 m even in places far from any bedrock exposures. Apparently during or following Pleistocene time the Korean Peninsula was tilted southwestward as a block and the old erosion surface was partly buried by pre- dominantly fine sediments carried by streams from the highlands to the east. Widespread tidal mudflats are present along the western coast. Streams crossing the coastal plain carry heavy loads of suspended sedi- ment and meander sluggishly to the sea. The larger rivers, at flood stage, transport rock fragments as large as pebbles and deposit them on their flood plains and in their channels. The water table is near the land surface in most of the coastal flatlands and in the steep-walled valleys. Some of the deeper wells in the flatlands tap both the water-table aquifer and an underlying artesian aquifer. The artesian aquifer is confined above by a clay layer that separates it from the water-table aquifer and be- low by the bedrock on which it rests. GROUND WATER The yields of wells tapping the unconsolidated de- posits range from 1 to 25 liters per second. However, the permeability, extent, and thickness of these de- posits indicate that with proper construction and care- ful development, wells yielding 50 to 100 1 per second could be drilled in many places. Most of the nonmountainous parts of the country are covered by rice paddies. Constructed so that seepage losses are minimal, the paddies have a floor of impermeable clay. Therefore, even though they are kept flooded much of the year, the paddies are not considered to be a significant source of recharge to underlying aquifers Most of the recharge probably results from influent seepage through river beds and from infiltration of flood waters and precipitation on uncultivated flood plains. Because artificial with- drawal of ground water is on such a small scale, fluctuations of the water table are due largely to natural causes. Extensive development of the ground water in unconsolidated deposits along stream courses would probably induce recharge by influent seepage from the streams and thereby lessen the amount of fresh water discharged into the sea. The effect would be more pronounced during the times of low flow. Population increase and industrial growth in the Republic of Korea will require fuller utilization of the country's water resources. Moderate to large quanti- ties of ground water can be developed from the un- consolidated deposits and possibly from sedimentary bedrock aquifers. Any such development should be preceded by, and based on, the results of detailed hydrogeologic studies. REFERENCES Geological Survey of Korea, 1956, Geologic map of Korea: Prepared jointly with the Geol. Soc. Korea, scale 1: 1,000,- 000. Kobayashi, Teuchi, 1953, Geology of South Korea: Tokyo Univ. pub., 293 p. GEOLOGICAL SURVEY RESEARCH 1964 SOURCE OF HEAT IN A DEEP ARTESIAN AQUIFER, BAHIA BLANCA, ARGENTINA By STUART L. SCHOFF; JORGE H. SALSO, and JOSE GARCIA, Recife, Brazil; Buenos Aires, Argentina Work done in cooperation with the Direccién Nacional de Geologia y Mineria of Argentina under the auspices of the Agency for International Development, U.S. Department of State Abstract.-Artesian water from wells more than 500 meters deep in the Bahia Blanca area discharges at temperatures 12° to 26°C above expectable normal. The extra heat may be related to a fault through which deep-seated waters could rise or by which intrusive rocks could have been introduced at depth. Part of the public water supply of the city of Bahia Blanca, southern Buenos Aires province, Argentina, is obtained by artesian flow from an aquifer 500 meters or more below the land surface. The tempera- ture of the water discharged from 9 wells in and north of the city ranges from 55° to 59°C and average 56.6°C. This average is about 17°C higher than the expectable temperature calculated from the normal geothermal gradient for the region, 1°C per 28 m. Yet volcanic activity or other obvious sources of heat are unknown for hundreds of kilometers in any direction. The authors present the principal know facts re- garding the artesian water supply and postulate that the extra heat is related to a fault. This paper is based chiefly on the records of 19 wells drilled by the Direccion Nacional de Geologia y Mineria and its predecessor agencies, as reported by Salso and Garcia (1958), and also on observations made in 1959 by the senior author, and Dr. Garcia and Sefior Amilcar F. Galvin, of the Direccion Nacional de Geologia y Mineria of Argentina. The city of Bahia Blanca is near the head of the bay of the same name on the Atlantic coast, about 560 kilometers southwest of Buenos Aires. It is near the seaward edge of a vast gently sloping plain where rocks are poorly exposed. The outcrop of the principal artesian aquifer has not been identified, but rocks probably equivalent to those of the under- lying basement crop out in the Sierra de la Ventana, 50 km northeast of Bahia Blanca. These rocks are intricately folded quartzite and schist of Paleozoic age (Harrington, 1947). The basement rocks have been penetrated at depths of 291 to 812 in wells at Pelicuré, Algarrobo, Anzoategui, and at a well 21 km south of General San Martin (fig. 1). The aquifer that yields thermal water at Bahia Blanca has not been identified in these wells, however. Still farther northwest the basement rocks probably are within 50 to 200 of the land surface (fig. 1). Although several aquifers underlie the coastal plain, only the principal aquifer, described in this paper, yields large supplies of water. The discovery well, drilled at Argerich in 1913 by the Direccion de Mineria, was 711 m deep and initially flowed 348 cubic meters per hour. This well was damaged and was replaced in 1915 by a second well, 705 m deep, which initially flowed 500 cu m per hour and in 1959 was still flowing about 20 cu m per hour. More than 30 wells tap the highly productive aquifer in an area extending about 60 km west and 25 km southeast of Bahia Blanca. Northwest of Argerich, the aquifer terminates against a fault, which has been mapped on the basis of physio- graphic relations, seismic evidence, and test drilling: The proved and probable extent of the principal aquifer is shown on figure 1. The wells considered in this paper are at Bahia Blanca, near Griimbein, at Puerto Belgrano, at Argerich, and near Lake Chasic6 (well Chasico 1). U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D153-D157 D153 D154 GROUND WATER 64° 63° §2° 61° 50 VT General San Martin o SHHIY HONIAOUI 0 Algarrobo | | o Anzoategui ! % EXPLANATION I i> ‘ x sl Proven Extent of principal aquifer Exposed quartzite and schist of Paleozoic age Well Chasicé 1 (8. | Less than 50 to 50 m 200 m Area where depth to base- ment rocks is shallow D Inferred fault U, upthrown side; D, downthrown side ‘ 50 KILOMETERS | ; i 0 50 MILES I ( Pelicura ahia Blanca (6.1) rto Belgrano (5.1) id (s. -on. oce Base from Direccion Nacional de Geologia y Mineria, June 1958 1.-Map of the Bahia Blanca area, Argentina, showing geothermal gradient in degrees centigrade per 100 m depth (in parentheses), extent of thermal artesian aquifer, and distribution of basement rocks. SCHOFF, SALSO, AND GARCIA The principal aquifer consists of fine- to medium- grained sand, gravel, and conglomerate derived from quartzitic rocks, together with lenticular beds of red clay. It probably is of Miocene age. Known only in wells more than about 500 m deep, it has been pene- trated completely in only two wells, where it is 283 and 382.5 m thick. Most other wells considered in this paper penetrate not more than 40 m of the aquifer. The top of the aquifer descends southeastward (seaward) about 0.8 m per km, and the deepest producing wells are at Puerto Belgrano. Initial yields of wells that tap the principal aquifer range from 50 to 1,000 cu m per hour. The yields generally have declined progressively, in part, no doubt, because discharge causes reduction of head, but also because of encrustation of the well casing; most wells have not been cleaned out. Yields also decline as a result of competing discharge. The yield of one of the wells in Bahia Blanca declined when another 1.2 kilometers away, began to flow, and increased when the flow of the other was stopped. CHEMICAL CHARACTER OF THERMAL WATER At best, the chemical quality of the water is accept- able for drinking, but the quality is not uniform from well to well. The dissolved-solids content (residue at 180°C) in 17 samples ranged from about 300 to about 1,760 milligrams per liter. Large differences in the dissolved-solids content and in some individual con- stituents have been recorded in waters of adjacent wells and also in wells of almost equal depth (Salso and Garcia, 1958, p. 23). The water from wells in the Bahia Blanca-Griimbein area on the whole contains less dissolved solids than the water at Argerich, to the west, or at Puerto Belgrano, to the southeast. Water from 3 of 13 wells sampled in the Bahia Blanca, Griimbein area contained more than 1,000 mg per 1 of dissolved solids. No analysis is available for the water from the westernmost well 1). Thirteen analyses are complete enough to permit chemical classification of the waters. All are sodium waters containing substantial proportions of chloride and bicarbonate. Two waters can be classed as sodium bicarbonate, 2 as sodium chloride, and 9 as sodium chloride-bicarbonate waters. Sodium ranges from 56 to 98 percent of the total cations (in equivalents per million), as illustrated for the Bahia Blanca-Puerto Belgrano area on figure 24. The "knot" in the upper part of the figure is due to abnormally low sodium content (offset by abnormally high calcium content) at one well. The distribution of chloride, in percent of total anions, is illustrated on figure 2B. The propor- tions of both sodium and chloride increase eastward 742-652 O-64--11 D155 and northward away from the sea. This suggests an independent source of sodium chloride inland; however, the water from most of the wells is not highly mineralized. WATER TEMPERATURE AND GEOTHERMAL GRADIENT The water temperatures generally were measured upon completion of each well and occasionally there- after; they probably are comparable although spread over a period of years, for the temperature of water coming from depths greater than 500 m is not likely to vary greatly. The warmest water (68°C) comes from a well at Puerto Belgrano, the deepest of those for which records are available. The shallowest well, however, yields the highest temperature water in rela- tion to depth (well Chasic6 1, fig. 1). The water temperatures have been studied in terms of excess temperature above expectable normal tem- perature, and also in terms of geothermal gradient. The estimated excesses of temperature serve chiefly to show that the water is unusually warm, but they can- not be precise because they involve (a) an assumed "normal"" geothermal gradient for the locality, and (b) an assumed mean annual air temperature of 15.5°C over the entire area. The same assumption as to mean annual air temperature is used in estimating the geothermal gradients, but no assumption as to "normal" geothermal gradient enters into this calculation. The calculations of geothermal gradient ignore the fact that the temperature of the rocks at moderate depth is likely to be a degree or two above mean annual air temperature (Van Orstrand, 1935, p. 88) and the fact that the lowest temperature in a well generally is not at the land surface but at a depth of about 30 m (McCutchin, 1930, p. 20). - The observed water temperatures probably represent somewhat different intervals within the aquifer, but in the absence of information as to permeability or other differences within the aquifer, all temperatures are assumed to represent that of water from the top of the aquifer. No obvious relation of water tem- perature to depth of aquifer, to thickness of aquifer penetrated, or to depth of well was noted; nor is there a simple relation between excess temperatures or geo- thermal gradients and these factors. When either excess temperatures or geothermal gradients are plotted on a map, they differ sufficiently within small areas to make the drawing of contours both difficult and dubious. Yet, for the area as a whole, certain major distinctions are apparent, as indicated by average gradients com- puted for Bahia Blanca, Griimbein, and Puerto Belgrano (fig. 1). GROUND WATER 5 KILOMETERS 4 5 MILES {oce net lie e, 0 ca 0, A200 5 KILOMETERS 4 5 MILES Loe,. des cet. 0, . 1.0 Lete Base from Consejo Federal de Inversiones 1962, vol. 1, p. 139 A. Sodium B. Chloride Ficur® 2.-Map of the Bahia Blanca-Puerto Belgrano area, Argentina, showing relative concentration of sodium and chloride in water from deep wells. A, lines of equal sodium concentration, as percent of total cations; B, lines of equal chloride concen- tration, as percent of total anions; computed from equivalents per million. A computation of excess temperature at well Chasic6 1 follows. An assumed normal geothermal gradient of 1°C per 28 m of depth was computed on the basis of ob- servations of temperature in different strata in the region. Dividing the depth to the aquifer, 507 m, by 28 gives 18°C, the expected temperature increment due to depth. Adding the mean annual air temperature for the locality, 15°C, gives 33.5°C, the temperature expected at a depth of 507 meters; and subtracting this from the observed water temperature, 60° gives 27°C, the excess at well Chasic6 1. Similar computations indicate that the excess at Argerich is about 21.7°C ; at Bahia Blanca, 15.8° to 19.5°C ; at Griimbein, 15.6 ° to 20.6°C ; and at Puerto Belgrano, 12.1° to 15.1°C. The computation of the temperature gradient for well Chasic6 1 starts with the observed discharge tem- perature, 60°C. From this is subtracted the mean annual air temperature, 15°C, to get the temperature increment due to depth, 45°C. This divided by depth to top of aquifer, 507 m, gives the geothermal gradient, 0.089 °C per meter, or 8.9°C per 100 m depth. Arranged in order from northwest to southeast, the average computed gradients are as follows: Geothermal gradient (degrees Centigrade Location per 100 m depth) Chasico Well 1.. 8.9 Argorich (2 6. 6 Bahia Blanca (9 wells). 6. 1 Grumbein (3 wells)... . _c. 6. 3 Puerto Belgrano (8 wells)......___....._. b.1 Averaging the geothermal gradients does not conceal overlap of gradient ranges. None of the wells at Bahia Blanca has a gradient as high as those at Argerich or Chasic6 1, or as low as those at Puerto Belgrano. However, at Griimbein, the group nearest to Bahia Blanca, some of the wells have geothermal gradients in SCHOFF, SALSO, AND GARCTA the upper range of those at Bahia Blanca, but none of them exceed this range. The highest geothermal gradient is nearest a fault that marks the boundary of the principal aquifer northwest of Argerich (fig. 1). Admittedly, this may not be the only fault in the region, but it is the only one now recognized with reasonable certainty. The fault may be a conduit through which deep-seated thermal waters rise into the aquifer, or through which intrusives have invaded either the basement rocks or the lower part of the sedimentary section. Whether deep-seated waters or an intrusive body provide the heat in the Bahia Blanca area is a matter for speculation. The following points, however, are pertinent. (1) A fault at great depth is more likely to be closed than open and more likely to allow the passage of a trickle than a flood of water. The passage of enough thermal water to raise the temperature in the aquifer substantially at Bahia Blanca therefore may be questioned. (2) Thermal water from great depth is more likely to be mineralized than fresh. If entering the aquifer in quantities sufficient to raise the temperature as much as indicated, such water conceivably could make the water in the aquifer too mineralized for use. (3) An intrusive could introduce a large amount of D157 heat, perhaps accompanied by only a relatively small amount of fluid. It could heat the aquifer and the water in it without greatly contaminating the water. (4) Volcanic glass found in strata of Miocene age above the principal aquifer in well Chasicé 1 (Salso and Garcia, 1958, p. 18) suggests that intrusion could have occurred somewhere in the region, but it is hardly proof that it occurred near Bahia Blanca. Volcanic ash in rocks of Tertiary and Quaternary age in the region generally has been attributed to volcanism in the Andes Mountains to the west. Volcanic ash from an eruption that occurred only a few years ago in the Andes was identified at Buenos Aires. REFERENCES Harrington, H. J., 1947, Explicacion de las hojas 33 m y 34 m, Sierras de Curamalal y de la Ventaria, prov. de Buenos Aires: Argentina, Direc. Minas y Geol. Bull. 61, 43 p., 2 pis. McCutchin, J. A., 1930, Determination of geothermal gradients in oil fields located in anticlinal structures in Oklahoma: Am. Petroleum Inst., Production Bull. 205, pt. 3, p. 19-61. Salso, J. H., and Garcia, José, 1958, Estado actual del conocim- inento hidrogeolégico de la cuenca artesiana de Bahfa Blanca: Direc. Nac. Geol. y Min. Bol. Inf. afio 2, no. 9 p. 15-26. Van Orstrand, C. E., 1935, Normal geothermal gradients in the United States: Am. Assoc. Petroleum Geologists Bull., v. 19, p. 78-115. w GEOLOGICAL SURVEY RESEARCH 1964 THE CARRIZO SAND, A POTENTIAL AQUIFER IN SOUTH-CENTRAL ARKANSAS By R. L. HOSMAN, Little Rock, Ark. Abstract.-Electric-log interpretations made as part of a water-resources study of the Mississippi embayment indicate that the Carrizo Sand of Eocene age is a potential aquifer in an area of about 5,000 square miles in south-central Arkansas. The dissolved-solids content of water from a recently drilled 2,050-foot test hole was less than 1,000 parts per million, con- firming these interpretations. The Carrizo Sand is the basal formation of the Claiborne Group of Eocene age throughout most of the Coastal Plain area in Arkansas, Louisiana, and Texas. According to electric-log interpretations made for the water-resources study of the Mississippi em- bayment, water in the Carrizo contains less than 1,000 parts per million of dissolved solids in an area of about 5,000 square miles in south-central Arkansas. However, substantiating water-quality data were not available until late in 1963, when a deep exploratory test hole near Pine Bluff was drilled into this forma- tion. In south-central Arkansas the Carrizo Sand is tapped by very few wells. It crops out in a narrow northeast-trending belt that in places is concealed by a thin cover of Quaternary deposits, and it dips to the southeast (fig. 1). The Carrizo consists generally of clean subangular to subrounded fine to medium sand, and in the subsurface it ranges in thickness from less than 25 feet to slightly more than 300 feet (fig. 2). It overlies the Wilcox Group and is overlain by the Cane River Formation of the Claiborne Group. In the subsurface south of lat 35° N., the Cane River is pre- dominantly a marine clay, but north of there it grades into sand, which together with the underlying Carrizo and the overlying Sparta Sand, forms a massive sand hundreds of feet thick. The area in which the Carrizo contains fresh water (dissolved-solids content less than 1,000 ppm) ranges in width from 8 to 55 miles, and within this area the depth to the formation ranges from 0 to a little more than 2,000 feet. In almost all of this area the Carrizo has not been developed as an aquifer because sufficient water could be obtained from the highly productive Sparta Sand and other shallower aquifers. The only withdrawals from the Carrizo are from a few shallow wells at and near the outcrop of this sand. In the vicinity of Pine Bluff, because the water level in the Sparta Sand has declined and because the water from the shallower aquifers generally requires treatment for industrial use, supplemental supplies are being sought for industries. Consulting engineers visiting the U.S. Geological Survey office in Little Rock were informed that the Carrizo Sand in the Pine Bluff vicinity probably contains fresh water, and on the engineers' recommendation, an industry drilled a test hole to the base of the Carrizo. The test hole penetrated the top of the formation at a depth of 1,900 feet and the base at 2,050 feet. The hole was cased and a short screen was set in the Carrizo section, but the well was not developed, as the primary interest was in the quality of the water rather than in the quantity available. Analysis of a sample of the water from the test hole showed the water to have a dis- solved-solids content of 650 ppm. However, the chloride content was 280 ppm, which is marginal for many uses without treatment or dilution of the water (dissolved-solids content and chloride content should decrease updip). The hardness of the water was 11 ppm, and pH was 7.4. The static water level was less than 15 feet below land surface and the bottom-hole temperature, recorded at the time the electric log of the well was made, was 103°F. The sand as observed in the drill cuttings was somewhat coarser than that in the Sparta. This fact coupled with the shallow U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D158-D160 D158 HOSMAN EXPLANATION -500 Structure contour of the top of the Carrizo Sand Interval 500 feet. Datum is mean sea level Area in which water in the Carrizo Sand probably contains less than 1000 ppm dissolved solids Approximate area of outcrop of the Carrizo Sand i p— CPine/Bluff eras {j _. | ~ i 2 _ yikes --A] Sif " —*[ '\\ é) (\K f s* 7 | & | | yo acne MISSISSIPPI 33° 10 10 LOUISIANA 91° 20 30 MILES Fiaur® 1.-Configuration of the top of the Carrizo Sand. static water level, suggests that large yields probably would be available at low lifts from the Carrizo and that the sand probably will be an important source of water in the future. The test hole, located near the estimated downdip limit of fresh water in the Carrizo, proved a sizable area in which the Carrizo Sand is a potential aquifer containing a large reserve of ground water. Delinea- tion of the area, which is virtually that shown on figures 1 and 2, is based entirely on interpretation of electric logs of oil tests. More exact limits of the aquifer capabilities of the Carrizo can be determined as supplies are developed from this sand and as water- quality and pumpage data become available. As ground-water supplies are developed from the Carrizo Sand, it would be advisable to monitor the quality of the water pumped from wells near the downdip limit of fresh water, in order to detect changes that might occur as a result of large with- drawals. Prolonged pumping in this area might cause updip encroachment of saline water. Changes in salinity should be detected as soon as possible so that remedial measures can be taken if the changes should be detrimental to the quality of the water. Systematic sampling and analyzing of water from observation wells located downdip from production wells would be the best method for the early detection of changes in water quality. D160 EXPLANATION 200 Isopach Showing thickness of the Carrizo Sand. Interval 100 feet Area in which water in the Carrizo Sand probably contains less than 1000 ppm dissolved solids Approximate area of outcrop of the Carrizo Sand ¢ o A0 GROUND WATER Little Rock MISSISSIPPI 93° LOUISIANA 92° 10 0 10 20 30 MILES 110000. Fiaur® 2.-Thickness of the Carrizo Sand. R 38° 91° GEOLOGICAL SURVEY RESEARCH 1964 GEOHYDROLOGY OF THE SPIRITWOOD AQUIFER, STUTSMAN AND BARNES COUNTIES, NORTH DAKOTA By T. E. KELLY, Grand Forks, N. Dak. Work done in cooperation with the North Dakota State Water Conservation Commission and the North Dakota Geological Survey Abstract.-The Spiritwood artesian aquifer is a buried bed- rock channel deposit composed of sand and gravel averaging 50 feet in thickness and exceeding 320 square miles in areal extent. Aquifer tests indicate a coefficient of transmissibility of 92,000 gallons per day per foot and a coefficient of storage of 0.0016. The water is of the sodium bicarbonate type. A large buried bedrock valley, which is occupied by the Spiritwood aquifer, was discovered in 1958 during reconnaissance test drilling in eastern Stutsman County, N. Dak. Subsequent test drilling in conjunc- tion with a ground-water study of Barnes County has further delineated the aquifer (fig. 1). Although pre- liminary study (Huxel, 1961) indicated that the bed- rock valley was part of a preglacial drainage system occupied by a northward-flowing stream, subsequent test drilling has shown that the valley has functioned also as a southward-draining outwash channel. This is indicated by the valley gradient, which is toward the south, and by the presence of thick deposits of glacial outwash in the channel. The Spiritwood valley has a relatively uniform width of 5 miles, except in Townships 142 and 143 N., where the apparent width increases abruptly to more than 12 miles (fig. 1). The valley was eroded more than 250 feet into the Pierre Shale of Late Cretaceous age. On the basis of test-drilling information, Huxel (1961, fig. 350.3) and Winters (1963, p. 35) reported the depth of the bedrock valley to be substantially greater. However, according to W. A. Cobban (oral communication, 1963) and (Gill and Cobban (1961, p. D185), a reevaluation of the test-drilling information indicates that the samples previously classified as lacustrine silt and clay of Pleistocene age actually are calcareous shale and marlstone from near the base of the Pierre Shale. The Spiritwood channel is bordered on the east by an elongate ridge that separates the main channel from a northeast-trending depression in Tps. 141 and 142 N. Test drilling indicates that the depression locally is deeper than the main channel but contains no deposits of sand and gravel. The depth of the depression, its lack of water-deposited coarse clastic material, and its parallelism with the main channel seem to preclude its being a tributary valley. The depression does not seem to be related genetically to the Spiritwood channel; because it is parallel to the direction of major ice advances across the area, it may be a feature caused by glacial scour. At least two ice sheets have overridden the Spirit- wood valley and deposited thick accumulations of till and associated glaciofluvial sediments (Lemke and Colton, 1958, fig. 3). These deposits range in thick- ness from 75 feet to more than 200 feet and completely obscure the bedrock valley at the surface. The Spiritwood aquifer occupies the lower part of the bedrock valley. Its thickness differs appreciably from place to place but in general decreases from north to south (fig. 2). The average thickness of the aquifer is about 50 feet; however, 162 feet of sand and gravel was penetrated in the drilling of a test hole in see. 31, T. 140 N., R. 61 W. The aquifer under- lies an area of at least 320 square miles in Stutsman and Barnes Counties, and recent test drilling indicates that it extends at least 10 miles farther north. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D161-D165 D161 D162 GROUND WATER R. 63 W. . f . § R. 60 W. \_\360/ .1341 EXPLANATION 145 .1491 Spiritwood aquifer 142 1292 1224 m e 16 mae 1200 w._. 1252 Contour on bedrock surface Interval 50 feet; datum is LU mean sea level 1478 e 1224 Well or test hole Number is altitude of bedrock surface in feet above mean sea level 141 » _¢_ Flowing well 1402 1404 1420 @ ® e 1406 67° e 1125.1413. 1305 367 1492® 1405 14472 1424® 1443 1428 o 14434, o NORTH DAKOTA Area of A report 1325 1329 1346 1419 ® ® 03 e 1245 z bas / 1429 i416 [ / §: | e -e 137 6 N is f | ¥" s e 1348 m. 1328 isas J S s I BARNES CoUnNnTYy 1333 a vant x _ eft " rem - mitel o 5 10 MILES pood rare t ue N ti e s 2 Figaur® 1.-Bedrock contour map of the Spiritwood channel in Stutsman and Barnes Counties, N. Dak. KELLY D163 R. 63 W. R. 62 W. - o ® e eo Z} 3 [HZ EXPLANATION 7: | XZ 143 5 !~ N. [3 5 $ ty" T i e. Su 142 at N. X § § Thickness of aquifer, #, in feet U o e 20 T. ® e s Well or test hole ¥ Number is thickness of aquifer, in feet ® ® e o o -o o o ® o e o e e _o o NORTH DAKOTA Area of/l report ® % 2 | T. ® 137 A I o o C I e O * _ 's _STUTSMAN CoUNTY L BARNES COUNTY 0 10 MILES (o 1 1 1 | 1 i 1 seid Figure 2.-Isopach map of the Spiritwood aquifer, Stutsman and Barnes Counties, N. Dak. A, B, sites of aquifer tests. D164 143 GROUND WATER 1427 142 141 140 139 138 137 7 1444 12 (“H STUTSMAN BARNES CcoUNTY 10 MILES I EXPLANATION I 4 BU Contour on piezometric surface Interval 10 feet; datum is mean sea level ©1427 Observation well Number is altitude of piezometric surface, in feet above mean sea level e1419 Domestic or stock well y 1350 Altitude of James River, in feet above mean sea level + Flowing well NORTH DAKOTA Area of A report Fiaurs 3.-Contour map of the piezometric surface of the Spiritwood aquifer, Stutsman and Barnes Counties, N. Dak. KELLY The gravel in the aquifer consists primarily of sub- angular to subrounded fragments of shale and lime- stone, although fragments of igneous and metamorphic rocks constitute as much as 20 percent of the total. The shale fragments were derived locally; however, the other rock fragments are typical of those in the Canadian Shield or lower Paleozoic sequence which borders the shield on the southwest. The sand grains range in size from very fine to very coarse and are angular to subangular. In areas of detailed test drill- ing, such as at sites A and B (fig. 2), the aquifer was found to differ lithologically both vertically and hori- zontally. In general, the lithologic characteristics of the sand and gravel indicate that these deposits were transported relatively short distances by large volumes of water. Silt and clay are only minor constituents of the aquifer and occur in thin, discontinuous beds. In Tps. 138 and 139 N., R. 63 W., the Spiritwood aquifer underlies the James River valley, the floor of which is 150 feet below the bordering plains (Paulson, 1962, p. 2; Winters, 1963, p. 74). Here the river flows on glacial outwash that partly fills the valley. The slope of the piezometric surface in the vicinity of the river (fig. 3) indicates that a natural discharge area exists where the outwash deposits in the James River valley are hydraulically continuous with the Spirit- wood aquifer. However, data are insufficient to esti- mate the rate at which ground water is discharged to the river. T'wo flowing wells tap the aquifer, one of which is reported to flow 150 gallons per minute. These wells were drilled through relatively thin sequences of con- fining drift in Tps. 138 and 189 N., R. 62 W. (figs. 1, 8). Aquifer tests at sites A and B (fig. 2) indicate that the Spiritwood aquifer will yield large quantities of water. The well pumped for the test at site A taps fine to medium gravel and coarse sand. Before the test the static water level was 127 feet above the top of the aquifer and 25 feet below the land surface. The coefficients of transmissibility and storage were com- puted, from the Theis nonequilibrium formula (Theis, 1935), to be 92,000 gallons per day per foot and 0.0016, respectively. In addition to indicating the impermea- ble barrier on the east (known also from test-hole data) this test indicated the presence of several in- distinct boundaries which may be due to differences in permeability within the aquifer. The test at site B D165 gave slightly lower coefficients of transmissibility and storage and did not indicate any aquifer boundaries. If the porosity is assumed to be 30 percent, the amount of water in transient storage is computed to be about 3 million acre-feet. Chemical analyses of water samples collected during aquifer tests and from test holes drilled elsewhere in the Spiritwood aquifer indicate that the water is of the sodium bicarbonate type. The total dissolved- solids content ranges from 680 to 1,370 parts per mil- lion and averages about 900 ppm. Differences in water quality from place to place in the aquifer are prob- ably due to inflow of water from the underlying Pierre Shale and overlying glacial till. The total dissolved- solids content of water from the shale averages ap- proximately 6,000 ppm and is as high as 8,110 ppm, whereas the total dissolved-solids content of water from the till ranges from 300 ppm to more than 4,000 ppm and averages about 2,500 ppm. As of early 1964, relatively few wells tapped the aquifer, and all of these were used for stock and domestic purposes. However, several irrigation opera- tions are planned and large-scale development of the aquifer is anticipated in the near future. Because of its broad areal extent, large storage volume, high permeability, and high hydrostatic pressure, the Spirit- wood aquifer is expected to become one of the more important confined aquifers in North Dakota. REFERENCES Gill, J. R., and Cobban, W. A., 1961, Stratigraphy of lower and middle parts of the Pierre Shale, northern Great Plains: U.S. Geol. Survey Prof. Paper 424-D, p. D185- D191 Huxel, C. J., Jr., 1961, Artesian water in the Spiritwood buried valley complex, North Dakota: U.S. Geol. Survey Prof. Paper 424-D, p. D179-D181. Lemke, R. W., and Colton, R. B., 1958, Summary of the Pleistocene geology of North Dakota: North Dakota Geol. Survey, Midwestern Friends of the Pleistocene 9th Ann. Field Conf. Guidebook, p. 41-57. Paulson, Q. F., 1962, Report on results of test drilling and pumping test in wildlife research project area, James River valley, Stutsman County, North Dakota: U.S. Geol. Survey open-file report, 18 p., 2 figs. Theis, C. V., 1985, The relation between the lowering of the piezometric surface and the rate and duration of dis- charge of a well using ground-water storage: Am. Geophys. Union Trans., v. 16, pt. 2, p. 519-524. Winters, H. A., 1963, Geology and ground-water resources of Stutsman County, North Dakota, pt. I, Geology: North Dakota Geol. Survey Bull. 41, 84 p. GEOLOGICAL SURVEY RESEARCH 1964 VARIATION OF PERMEABILITY IN THE TENSLEEP SANDSTONE IN THE BIGHORN BASIN, WYOMING, AS INTERPRETED FROM CORE ANALYSES AND GEOPHYSICAL LOGS By JOHN D. BREDEHOEFT, Washington, D.C. Abstract.-An empirical relation of porosity versus permea- bility was developed for the Tensleep Sandstone within the Bighorn Basin, Wyo., from laboratory core-analysis data. Co- efficients of permeability were estimated using this empirical relation and porosity values interpreted from sonic and neu- tron logs. ~A wide but systematic variation in permeability from very high values in the outcrop area to low values in the center of the basin, which is consistent with geologic knowledge, was observed. In the analysis of large aquifer systems, hydrolo- gists must rely on data already available from petro- leum exploration for information on the deep parts of sedimentary basins. Commonly the only applicable data are porosity and permeability determinations from laboratory analyses of drill cores and from geo- physical logs made in the course of exploratory drill- ing for petroleum. In an effort to determine the areal distribution of permeability in the Tensleep Sandstone of Pennsylvanian age in the Bighorn Basin, Wyo., the relation between porosity and permeability of the Tensleep Sandstone was determined and used in inter- preting the permeability from the porosity of the for- mation throughout the basin. At the time of this study, approximately 750 labora- tory core analyses were available from 17 wells from which porosity and permeability of the Tensleep Sandstone in the Bighorn Basin had been determined from small plugs. Although the plugs represent a good sampling of vertical sections of the formation, they provided only limited knowledge about areal variations in permeability. Several of the 17 wells from which information was available were closely spaced; on a regional scale, data were available for 9 localities in the basin. The laboratory porosity and permeability data pro- vide a basis for determining an empirical relation between permeability and porosity, making possible the extrapolation of permeability data on the basis of porosity values interpreted from standard geophysical borehole logs. Fortunately, many problems of fluid movement require only that estimates of transmissi- bility be within the proper order of magnitude. Other investigators have made similar studies of porosity versus permeability, as for example, Law (1944) and Archie (1950), who published semilog plots of this relation for several formations in the Gulf Coastal Plain. EMPIRICAL RELATION OF POROSITY TO PERMEABILITY Porosity values from laboratory analyses of drill cores of the Tensleep Sandstone were plotted against the logarithm of permeability (fig. 1). A best-fit trend line then was drawn by eye through the Ten- sleep data (fig. 1), and a digital computer was used in an attempt to derive the best least-squares poly- nomial fit for the data. Polynomials up to and includ- ing degree five were calculated; however, the best fit appears to be the line drawn by eye (fig. 1). At lower values this curve agrees rather well with the slope that Archie (1950) found for Gulf Coast sediments (one log-cycle change in permeability per 3-percent change in porosity). Except for differences in thickness and degree of cementation, the Tensleep Sandstone is lithologically similar throughout the Bighorn Basin; presumably it was deposited as a uniform sand across the entire basin. The size and sorting of the sand grains making up the sandstone are reasonably uniform over the basin, and differences in porosity as well as in permea- bility appear to be primarily the result of secondary cementation and recrystallization of the sand grains. This results in an increasingly interlocking fabric of U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D166-D170 D166 BREDEHOEFT D167 10 - POROSITY, IN PERCENT 20 +- 25 | | 0.01 0.1 1 10 100 1000 PERMEABILITY, IN MILLIDARCYS Fiqur® 1.-Semilog plot of porosity versus permeability, based on data from the analyses of cores of the Tensleep Sandstone in the Bighorn Basin, Wyo. sand grains with increased depth of burial. Because both porosity and permeability differences are mainly the result of secondary cementation, it is reasonable to conclude that permeability relates directly to poros- ity, as figure 1 indicates. COMPUTATION OF POROSITY AND PERMEABILITY Both the sonic log and the neutron log can be used to determine formation porosity, in place. Procedures using these logs are in general use in the petroleum industry. A theoretical method is used to determine formation porosity from the sonic log (Wyllie, 1963, p. 130-133) ; an empirical method is used to determine porosity from the neutron log (Wyllie, 1963, p. 118- 119). Figure 24 shows a comparison of porosity de- termined from cores with porosity determined from a sonic log in one well, and figure 22, a comparison of porosity determined from cores with porosity deter- mined from a neutron log in a second well. Core analyses were not available for a well with both a sonic log and a neutron log, and hence no direct com- parison of the use of both methods together for esti- mating permeability is possible. It is not expected that the coefficient of permeability based upon laboratory determination from a small plug would compare in detail with the coefficient of permeability based upon calculations from a continu- ous log of rocks in place. The sample analysed in the laboratory represents only a small fraction of even the total sample taken in a single foot of core. In the geophysical log the logging device is continuously recording a signal that represents an integration of a particular physical property of the rock and of bore- hole fluid within the radius of influence of the device. Hence, although both the laboratory and log data are plotted as foot-by-foot determinations on figure 2, it is not to be expected that each pair of plots would agree in detail. Nevertheless, overall there is a clear general correspondence. There is some question as to whether laboratory core analysis of permeability is applicable to field condi- tions. However, Johnson and Greenkorn (1960) found that permeabilities derived from laboratory determina- tions from cores showed good agreement with permea- bilities determined by conventional aquifer tests in the field. For the purposes of this paper it is assumed that the laboratory data are representative of field conditions. Thirty-three neutron logs and 15 sonic logs, which included all the logs of these types available from wildcat holes in the Bighorn Basin, were used to estimate the permeability to the Tensleep Sandstone. D168 GROUND WATER FARMERS UNION 16 GOV'T. SHAD Porosity (percent) Porosity (percent) from core analysis from sonic log 0 10 20 0 10 20 4300 4320 4340 4360 4380 4400 DEPTH, IN FEET 4420 4440 4460 4480 A SsOHIO 15 SAGE CREEK Porosity (percent) Porosity (percent) from core analysis from neutron log 0 10 20 0 10 20 3280 3300 No data 3320 No data 3340 DEPTH, IN FEET 3360 3380 3400 F1aur® 2.-Comparison of porosity of the Tensleep Sandstone as determined by three methods. A, comparison of porosity determined from core samples with porosity computed from a sonic log. B, comparison of porosity determined from core samples with poros- ity computed from a neutron log. The interval of formation logged was divided into categories on the basis of the computed porosity, as follows: less than 8 percent porosity, 8 to 11 percent porosity, 11 to 16 percent porosity, and greater than 16 percent porosity. These categories were selected from the curve of porosity versus permeability (fig. 1) to correspond to successive log cycles of permeability on the porosity-permeability curve. The transmissibility of an aquifer may be defined as: T'= EKtmg, where i=1;2, 8 . ... 1, T=transmissibility, K,=permeability of the ¢ layer, m,;=thickness of the < layer, and n=number of layers of differing permeability. In estimating the transmissibility from the logs the following relation was applied to the data 1: T'= 272177141 -+ 2K2m2+ 2K3M3+ 222477114, where mi=footage logged of <8 percent porosity, m=footage logged of 8-11 percent porosity, ms=footage logged of 11-16 percent porosity, m,=footage logged of >16 percent porosity, K,=mean permeability of <8 percent porosity interval, BREDEHOEFT K,=mean permeability of 8-11 percent porosity interval, K,=mean permeability of 11-16 percent porosity interval, and K,-=mean permeability of >16 percent porosity interval. f Because of the great spread in permeability values the intervals with high porosity and permeability determine the effective transmissibility of the forma- tion. From calculations based on figure 1 it can be seen that 1 foot of Tensleep Sandstone with 13 percent porosity has the equivalent transmissibility of approx- imately 8 feet with 10 percent porosity. Most intervals of less than 11 percent porosity contribute only a small fraction of the ability of the Tensleep Formation to transmit fluids. Transmissibilities computed from the logs by the procedure described represent standard laboratory conditions, not field conditions. Accordingly, the ef- fects of changes of temperature under field conditions on viscosity were corrected for in translating the computed coefficient of transmissibility to field condi- tions at depth. Many wells penetrate only part of the Tensleep Sandstone, and the data were extrapolated on the assumption that the interval logged was repre- sentative of the entire formation. Because of the wide variation in the coefficients of transmissibility in the Bighorn Basin (in excess of three orders of magnitude) it is most convenient for statistical manipulation to express coefficients of trans- missibility in terms of their logarithms. Table 1 lists the logarithms of the values for the coefficient of transmissibility (expressed in millidarcy- feet) determined from laboratory measurement and as computed from the sonic and neutron logs of the same well. Values computed from two or more closely spaced wells, generally less than 2 miles apart, are compared in table 2. Statistical analysis of these re- sults from limited areas was made to evaluate the reliability of the data. The geometric mean of all the transmissibility values for a limited area was assumed to represent the most probable value for the area (table 2). The geometric mean was used because it is less affected by the extreme variability of the trans- missibility data than is the arithmetic mean. A nor- mal distribution plot of the deviations from this mean value was made to obtain a measure of the scatter of the data. The standard deviation of the data was approximately 0.2 log cycle. Results of various meth- ods were grouped and analyzed statistically; the analysis shows reasonable agreement between the dif- ferent methods (fig. 3). D169 transmissibility of the asin computed from dif- 1.-Comparison of coefficient 0 Tensleep Sandstone in the Bighorn ferent source data from single wells. Location ! Core Neu- Sonic analy- tron log Well sig log (log _. Town- | Range (log (log md-ft) 2 ship (west) | Section md-ft) 2 | md-ft) 2 (north) 48 91 6| Farmers Union € 1291... -.. 4. 024 16 Gov't. Shad. 44 95 24) Continental 38 _ |_____. 3. 577) 3. 995 Gebo. 45 92 23) California Co. 11 | 2. 788) 8. 416|_.__._. Unit. 46 98 19] Ohio 6 Pre-Ten- |__---- 3. 602) 3. 562 sleep. 51 93 12] Kirk Oil 10 Lamb.] 4. 395) 3. 810|-___-. 57 97 18] Sohio 15 Sage 4. 27901 4. 106]...... Creek. 1 Referred to 6th principal meridian and base line. 2 1 millidarcy-foot=0.01824 gallons per day per foot (see Wenzel, 1942). TABLE 2.-Comparison of coefficient of transmissibility of the Ten- sleep Sandstone in the Bighorn Basin computed from different source data in closely spaced wells Location ! ® Core Neutron Sonic log Geometric analysis log (log md-ft) | mean value Township | Range | Section | (log md-ft) | (log md-ft) (log md-ft) (north) (west) 48 91 6 4 128 .z uv... 4. 024 4. 039 43 92 1 L108 |_ .. 43 92 1 B/JBA0: |x -LEL i. c 44 95 J 12 G 0B |..:..._~. 3. 852 44 95 P4 3. 577 5.005 |_... 44 98 12 |.... 3. 662 3. 972 44 98 $3 4 151 l. clin l 44 98 15 3. 668 4405 45 92 23 2. 788 G. A410 |.: :_....- 3. 102 46 98 19 3. 602 5: §02 :...... 3. 582 48 102 11 4. 394 0. 880 |.:-...-.- 4. 026 48 102 14 >.. 4. 114 48 103 20 3. 686 O AOT 3. 529 48 103 29 {-s 9: 4094 |: 51 93 12 4. 395 |........ 4. 102 55 95 19 B. 008 (F-. 3. 411 55 55 29 3. 308 [...... 55 95 32 3. B17 {s... 56 97 14 4. 142 56 97 14 [._ en duane 56 101 16 2. 902 B 125 2. 565 57 97 18 4. 279 1: ...... 4. 345 57 97 18 4.050 |.. Referred to 6th principal meridian and base line. CcoNnCcLUSsIONnS Use of an empirical porosity-permeability relation proved applicable in mapping differences in trans- missibility of the Tensleep Sandstone within the con- fines of the Bighorn Basin. Data interpreted from the sonic and neutron logs were combined with data from core analyses and from drill-stem tests and were plotted on a map (not shown) showing the regional transmissibility of the Tensleep Sandstone. Although the plots indicate considerable variation in any small D170 +0.4 +08 + o bo L 0 s (log transmissibility) I o - o DEVIATION FROM GEOMETRIC MEAN I o ho I 0 to I d p / ll/L/Yl\lllilllllillL 0.1 0.2 0.5 1 2 5 10 20 30 40 506070 80 90 95 98 9999.5 99.9 PERCENT OF TOTAL NUMBER OF OBSERVATIONS / Figur® 3.-Probability graph of deviation of the coefficient of transmissibility (log millidarcy-feet) from the "most proba- ble" value-geometric mean of observations in a limited area-versus cumulative percent of the total number of observations. area, areal plotting indicates a systematic regional decrease in transmissibility from the outcrop toward the structural center of the basin. The average per- meability ranges from approximately 1 millidarey in #. GROUND WATER the structurally deeper parts of the Bighorn Basin to more than 800 millidarcies near the outcrop. This variation is reflected in a range in coefficient of trans- missibility from several hundred millidarey-feet in the deeper parts of the basin to values greater than 100,000 millidarey-feet near the outcrop. This systematic re- gional pattern of transmissibility change, which agrees well with the known geology, lends support to the usefulness of the empirical method in this area. REFERENCES Archie, G. E., 1950, Introduction to the petrophysics of reser- voir rocks: Am. Assoc. Petroleum Geologists Bull., v. 34, no. 5, p. 943-961. Johnson, C. R., and Greenkorn, R. A., 1960, Comparison of core analysis and drawdown test results from a water- bearing upper Pennsylvanian sandstone of central Okla- homa [abs.]: Geol. Soc. America Bull., v. 71, no. 12, pt. 2, p. 1898. Law, Jan, 1944, A statistical approach to the interstitial heterogeneity of sand reservoirs: Am. Inst. Mining Metall. Engineers Trans., Petroleum Div., v. 155, p. 202-222. Wenzel, L. K., 1942, Methods for determing permeability of water-bearing materials with special reference to dis- charging-well methods: U.S. Geol. Survey Water-Supply Paper 887. Wyllie, M. R. J., 1963, The fundamentals of well log inter- pretation: New York, Academic Press, 238 p. GEOLOGICAL SURVEY RESEARCH 1964 UNIFORMITY OF DISCHARGE OF MUDDY RIVER SPRINGS, SOUTHEASTERN NEVADA, AND RELATION TO INTERBASIN MOVEMENT OF GROUND WATER By THOMAS E. EAKIN and DONALD O. MOORE, Carson City, Nev. Work done in cooperation with the Nevada Department of Conservation and Natural Resources Abstract.-Flow measurements show that Muddy River Springs had uniform discharge during a period from Septem- ber 1963 to April 1964; adjustments of the discharge record of Muddy River for local runoff and evapotranspiration show a long-term uniformity of springflow. Preliminary analysis of minor long-term variations suggests a 15- to 20-year lag in response to recharge from precipitation. The Muddy River in southeastern Nevada is sup- plied principally by springs in the northwestern part of upper Moapa Valley. The ground water supplying the springs is inferred to be part of a regional ground- water system in Paleozoic carbonate rocks lying up- gradient, or northward, from the Muddy River Springs. The area of the regional system provision- ally is estimated to be roughly 7,700 square miles and includes 13 valleys in eastern and southeastern Nevada. Reconnaissance ground-water investigations for the specific valleys have been reported previously (Eakin 1961, 1962, 1963a, b, c, and 1964; Maxey and Eakin, 1949). The inference that the Muddy River Springs are supplied from a large and complex regional ground- water system suggests that the discharge of the springs should tend to have a relatively uniform flow. The flow of the Muddy River is gaged a short dis- tance below the spring area. To utilize this record as a measure of the actual discharge of the springs, the record must be corrected for overland runoff re- sulting from local precipitation and losses of spring flow by evapotranspiration or diversion upstream from the gaging station. DESCRIPTION AND RECORDS OF THE SPRINGS The Muddy River Springs are at the head of the Muddy River, in upper Moapa Valley in southeastern Nevada (fig. 1). The springs issue from several groups of orifices and seep areas within the area shown on figure 2. Groups of orifices from which localized discharge occurs, such as the Iverson and Pederson groups, generally are along the margin of the flood plain. Others, such as Warm Spring and the group east of Warm Spring near U.S. Highway 98, however, issue from gravel ridges that extend into the general area of the flood plain. The seep areas are in the flood plain, downstream from the spring groups and along the natural and artificial channels. Along the main channel, flow derived from the spring area increases from zero near point 7 (fig. 2) to about 47 cubic feet per second at the gaging station, in a straight-line distance of 2 miles. Between the spring orifices and seep areas and the gaging station, evaporation and transpiration dissipate some of the spring discharge. Thus the flow of the river at the gaging station is less than the actual spring discharge. Evaporation and transpiration result from both natural effects and irrigation activities. The overall area in which evapo- transpiration may have an effect on the flow at the gaging station probably is on the order of 750 acres. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D171-D176 742-652 O-64--12 D171 D172 118° 116° 114° 112° Ely 39° |- - °Adaven Muddy River Springs area 100 MILES Figur® 1.-Index map of southeastern Nevada, showing the Muddy River Springs area. Although the springs issue from Recent alluvium in the flood plain and from conglomerate of the Muddy Creek (?) Formation in slopes bordering the flood plain, most of the water probably is transmitted to the spring area through Paleozoic carbonate rocks, which crop out close to some of the springs along the southwest side of the flood plain and which comprise most of the adjacent Arrow Canyon Range. The records used in this analysis are for the flow of the Muddy River at U.S. Geological Survey gaging station 9-4160, Muddy River near Moapa, Nev., in the SEV, see. 15, T. 14 S., R. 65 E., Mt. Diablo base line and meridian. Long-term records have been pub- lished in Geological Survey water-supply papers. As a part of a reconnaissance ground-water study of the area in September 1963 (Eakin, 1964), meas- urements or estimates of flow were made at 40 sites upstream from the gaging station to provide data on the relation of springflow to the gaging record. These sites included several springs and seep areas, main diversions, tributary confluences, and points along the main channel. Subsequently, measurements were made at the same sites in January 1964. Of these sites, 14 were selected and were measured again in March, April, and May 1964. Several sites of the 40 original sites, some the same as the present 14 sites, were meas- ured in October and December 1963 and February 1964 for interim control. The present sites are suffi- cient to demonstrate the relative uniformity of spring GROUND-WATER-SURFACE-WATER RELATIONS discharge as compared to the seasonal fluctuations recorded at the gaging station. RELATION OF SPRINGFLOW TO DISCHARGE OF THE MUDDY RIVER The relation of the spring discharge to the flow of the Muddy River at the gaging station is illustrated for part of 1 year on figure 3, which shows a graph of measured discharge for 6 intervals of time between September 1963 and April 1964. The upper graph is a plot of the flow measured at the gaging station; the lower is a plot of the sum of the discharge at 6 points of measurement (points 1 to 6 on fig. 2) for the 6 intervals. The sum of spring-discharge measure- ments shows very little variation; the minimum is about 97 percent of the maximum. Measuring points 1 to 4 are close to spring orifices and are little affected by intermediate evapotranspiration. Measurements at points 5 and 6 show localized spring discharge and seepage gain along channel sections and may vary to a minor extent because of seasonal evapotranspiration. Together the discharge measured at the 6 points repre- sents about 60 percent of the total spring discharge of the area and is considered to be reliable index of the uniformity of the total spring discharge. This is supported by the data obtained for the 2 series of measurements at the 40 sites upstream from the gaging station. To reconstruct the spring discharge from the records of flow of the Muddy River at the gaging station, adjustments have been made for (1) streamflow at the gage resulting from local precipitation and runoff, (2) evapotranspiration between the springs and gag- ing station, (3) the effects of diversions that tempo- rarily may bypass the gaging station and, (4) within- area changes of diversions which result in temporary modifications of the flow pattern. - Ground-water underflow past the cross section of alluvium normal to the river at the gaging site is believed to be uniform and does not represent a significant accretion to stream- flow downstream from the gaging station. In large part the analysis concerns mean monthly and annual flow. Accordingly, item 4 above tends to be averaged out for present purposes, and item 3 prob- ably was a minor factor during most of the period of record. Although past data are not available, the present diversion includes perhaps 1 efs now carried in a pipeline to the town of Overton from one of the springs. Also, an irrigation well in the spring area north of the gaging station, which pumps about 3 cfs, is used for irrigation north and southeast of the gaging station. Although quantitative data are not available, the pattern of pumping of the well and the area D173 EAKIN AND MOORE To Ey Gaging, station, ~; 0 Ya 1 MILE Figur® 2.-Sketch map of the Muddy River Springs area, showing location of principal springs, stream channels (solid lines), and principal irrigation ditches (dashed lines). Numbers refer to selected measuring points. irrigated suggest that, in effect, most of the water is evaporated or transpired from the area; however, a small amount may reach the main channel upstream from the gage from adjacent fields after periodic watering during the year. Evapotranspiration, both natural and from irrigation, between the springs and the gaging station is the principal factor resulting in differences between the total spring discharge and the flow of the river as measured at the gaging station. Although streamflow generated from local runoff occasionally results in a very high peak discharge, the long-term effect on the flow of the Muddy River is small. A simple correction for the effects of local precipita- tion on most of the streamflow was made for the 18- year period 1945-62. The adjustment was made by reducing the high flow shown for short intervals of storm runoff to values consistent with the immediately preceding and succeeding daily streamflow. The num- ber of adjustments in mean monthly discharge is given in the accompanying table, together with the mean and median discharge. The distribution, by month, of the 24 adjustments shows 6 adjustments each for July and August, the principal months in which sum- mer thundershowers occur. As shown, the adjustment of streamflow to account for local precipitation has a minor effect on the record of annual flow of the Muddy River. However, the adjustment results in a month-to-month change in the record for the Muddy River at the gaging station that is more consistent with the expected pattern of the month-to-month change resulting from seasonal effects of temperature and evapotranspiration. T T T T T T T > 50 |- .__'. ae e Muddy River 0 o w) U . e - a / \. L a. E o u u 40 |- A o c 2 el Z - al ul ol % 3 30 —./.\./._\°/. 8 Springs ay o | | | | | | Sept.I OctI Nov. I Dec. Jan. I Feb. I Mar. I Apr. 1963 1964 Fiaur® 3.-Measured discharge at the gaging station, Muddy River near Moapa, and the sum of measurements of springs at 6 sites, numbers 1 to 6 inclusive on figure 2, for 6 time intervals during the period September 1963 to April 1964. D174 Long-term mean, median, and adjusted monthly discharge of Muddy River near Moapa for the period of water years 1945-62 18-year 18-year 18-year Number mean median adjusted of adjust- Months discharge | discharge mean ments, by (cfs) (cfs) discharge ! month cfs) October._....:.....c.. 46. 5 46. 5 46. 4 1 November......._..._ 49. 5 48. 2 48. 8 3 50. 2 50. 1 50. 1 2 Jantiary -. 50. 2 49. 5 50. 2 0 February. ...._..._IL. 49. 4 49. 6 49. 1 o 48. 3 47.8 48. 2 1 ApHil. ._ 46. 6 46. 6 46. 6 0 May. ..::. .C.... 45. 3 45. 6 45. 2 1 43. 4 49. 7 43. 3 2 -:- cs 43. 4 43. 6 42. 9 6 Amonst.. 44.7 |! 43:3 43. 7 6 eptember..._...._:._ 44, 4 44. 4 44, 4 0 46. 8 46. 9 46. 6 24 1 Adjusted to eliminate the amount of runoff derived from local precipitation from the gage record. Adjustment for evapotranspiration Diurnal and seasonal fluctuations in streamflow occur in response to evapotranspiration, which in turn is related mainly to the seasonal variations in tempera- ture. Figure 4 shows daily fluctuations in the water-stage record for August 12 and 13, 1963, resulting from the diurnal variation in the rate of evapotranspiration. The graph for January 29 and 30, 1964, shows no such fluctuation. The two periods shown by the graphs are during maximum (June-August) and minimum (De- cember-January) periods of evapotranspiration. The range in fluctuation of the August graph represents about 2 cfs, and is considered to be due primarily to the diurnal effect of evapotranspiration along the main and the principal tributary channels of the stream. Seasonal variations in evapotranspiration in the area between the gaging station and the springs also 1.10 1.05 Jan. 29, 1964 Jan. 30, 1964 1.00 1.00 GAGE HEIGHT, IN FEET 0.95 Aug. 12, 1963 0.90 - Aug. 13, 1963 1 1 I 1 1 l 1 f 12 6am. 12 6pm. 12 Gam. 12 6pm. 12 Figur® 4.-Stage of the Muddy River for the 2-day periods January 29 and 30, 1964, and August 12 and 13, 1963, illustrating diurnal effect of evapo- transpiration during the summer. GROUND-WATER-SURFACE-WATER RELATIONS affect the flow of the river. The adjusted mean monthly discharge (from the table), plotted on figure 5, shows that the minimum mean discharge occurs in July and the maximum in January, with moderately large changes in the intervening months. The mean monthly temperature at Overton is plotted for com- parison. -It, too, shows a change from month to month, but as might be expected, in an inverse pattern-the months of highest temperature correspond to the time of greatest stream loss through evapotranspiration. Figure 6 shows an excellent correlation of discharge of the Muddy River at the gage with air temperature. The high degree of correlation, even though the ad- justed mean monthly discharge of the river ranged from 42.9 to 50.2 cfs, clearly indicates that the input, or spring discharge, supplying the river is highly uni- form from month to month. Thus, because the spring discharge is uniform, it is represented closely by the gaging record of the river during January, the month of minimum evapotranspiration. The adjusted mean January discharge is 50.2 efs. Furthermore, if this is representative of the mean annual discharge of the springs, then the amount of spring discharge dissi- pated by evapotranspiration can be estimated by sub- tracting the adjusted mean annual discharge (46.6 cfs) of the Muddy River. Thus 3.6 efs represents the part of the mean annual springflow that discharges at the land surface and is consumed by evapotranspiration between the springs and gaging station.. § Long-term uniformity of discharge Some variation in annual mean discharge of Muddy River Springs is evident from the published records of Muddy River streamflow. As noted in the table, 50 P. helt L 90 . ® L u o \ * JA / & Pe4glk. 0 Temperature 4 2+ 73 / * & so 2 E f nan- oa [ fne" ale Joa y:" ? Cole is ; o ah. Cik cass county is ys" jel sf a 30° # > i eRe % 22 r Mad De® Plo } 1 Me a 9,0 j . y PHZ} Mois s ZZ Mol e o|< > C+ 52 H NORTH 7 tig e 21g . Pek & file % DAKOTA ghd p M \ AreaoV/- (yg \ B * 01...".'.. - ; t ..|...’o w o.. '..o : | s - a. 9 a a an . 0 5 10 MILES EXPLANATION Lake Agassiz plain Underlain mainly by clay and silt Sheyenne delta Underlain mainly by sand Drift prairie Underlain mainly by till chv‘ Partial-record station w-» ~~ Gaging station ve e o 6 o e e e Ground-water divide Approximate position 1.-Map showing generalized geomorphic subdivisions of southeastern North Dakota and observation stations along the Sheyenne River. Table 1 gives the mean monthly discharge in cubic feet per second at discharge stations on the Sheyenne River at Valley City, Lisbon, Kindred, and West Fargo during the period October through February, 1957-62. The months of October through February were chosen for comparative purposes because, gen- erally, little or no overland runoff occurs during this period. Although the discharge at Valley City in- cludes releases from Lake Ashtabula, the changes in discharge recorded at stations below Valley City mainly reflect changes in ground-water inflow and evapotranspiration rates. It may be seen from the table that the mean monthly discharge of the Sheyenne River from October through February for the period 1957-62 increased by 15.1 cfs between Lisbon and Kindred. As late fall and early winter is a time of little or no runoff, the increase is attributed mainly to ground-water inflow. In addition, PAULSON an estimated 1.7 cfs probably was held in storage as ice during this period (H. M. Erskine, 1963, written communication). Comparison of the data given in table 1 shows that the increase in discharge per mile length of channel between Lisbon and Kindred was about 20 times greater than between Valley City and Lisbon and about 6 times greater than between Kin- dred and West Fargo. 1.-Mean monthly discharge of Sheyenne River, October through February, 1957-62, in cubic feet per second [Numbers in parenthesis indicate river miles above mouth] Valley Lisbon Kindred West City (162) (68) Fargo (253) (24) 28. 0 81. 7 50. 7 52. 6 November..........._L 41. 5 42. 9 62. 0 61. 0 December:..........__L 43. 5 41. 9 56. 5 59. 3 Januaty....:......_.-.L 41. 6 38. 8 52. T 54. 4 40. 1 42. 5 51. 5 52. 6 Average for 5-month period. _I 38. 9 39. 6 54. 7T 55. 9 Average gain between 0. 7 15. 1 1. 2 Average gain per mile of . 008 l . 160 . 027 In order to determine more precisely the nature and magnitude of the increase in discharge, a series of 13 partial-record stations (4 through J, fig. 1) were established between Lisbon and Kindred. Five series of current-meter measurements were made at approxi- mate 2-week intervals during the period from Sep- D179 tember 13 to November 19, 1963 (table 2). Each series of measurements was obtained in as short a period as possible (generally less than 24 hours) to minimize the effects of changing stage. However, a changing stage caused by releases from Lake Ashtabula affected the November 19 measurements made at Valley City, Lisbon, and West Fargo and at stations A and B. The averages of the discharge measurements, except those affected by releases from Lake Ashtabula, made at each of the partial-record stations, as well as at the stations at Valley City, Lisbon, near Kindred, and at West Fargo are plotted on the hydrograph shown on figure 2. The data in table 2 and on figure 2 show an average increase of 28.8 cfs in the discharge between the sta- tions at Lisbon and Kindred. This is substantially more than the average increase of 15.1 cfs for the October through February, 1957-62, period (table 1). Precipitation and ground-water records indicate that the recharge received annually by the delta deposits was considerably larger in 1962 and 1963 than during the 3 years prior to 1962. The increased recharge resulted in a higher water table, steeper gradients to- ward the Sheyenne River, and increased rate of ground-water movement toward the river. RELATION OF RIVER DISCHARGE TO GEOLOGY The data in tables 1 and 2 and the graph on figure 2 indicate very little ground-water inflow between Val- ley City and Lisbon, a river distance of 91 miles. The surface and near-surface deposits draining into this stretch of the river consist mainly of till underlain Tapur 2.-Measurements of discharge of Sheyenne River between Valley City and West Fargo, N. Dak., 1968 Discharge (cubic feet per second) Average of discharge Gaging station River mile measurements Sept. 13 Oct. 1 Oct. 15 Oct. 20 Nov. 19 made Sept. 13- Nov. 19 Valley City (discharge computed from gage- fRelght 253. 0 11. 0 7.9 6. 9 5. 7 ' 33. 0 7. 87 P dn. .o o 162. 0 6. 98 6. 22 11. 4 13. 7 1 25. 0 9. 57 Stations: eee nere dite edi w ecb ene naa aad o 147. 5 8. 60 8. 02 11. 0 17. 0 1 21. 4 11. 1 Mev sL a Lad bev aos cn arkien s anns aB amana 141. 6 10. 3 8. 96 13. 2 19. 3 ' 18. 6 12. 9 (EEF re nes 134. 9 11.1 9. 31 11. 4 21. 3 10: 2 13. 9 (rans re Hedin naren een an new aeons a 191. 5 11. 7 9. 20 13. 9 21. 8 19. 2 15.2 | flea ep ag Prao ca in 125. 9 11. 6 8. 56 15. 0 21. 1 18.2 14. 9 l ce P nline bres ae nea n ae s a rea 114. 0 16. 6 12. 5 18. 6 27.9 24. 5 20. 0 (elie n etre iad ent uas as Uma nana 104. 0 21. 9 18. 8 24. 1 28. T 30. 8 24. 9 (Ne ene eee n TI. . ele mans ae 97. 4 24. 1 21. 1 28. 3 38. 1 27..6 26. 9 Peeler ren psd. lloc di na} 91. 8 29. 8 26. 2 32. 9 35. 0 33. 0 31. 4 Ie ire ener ak nene ee augue -=» area ar. 87. 6 31. 5 25. 8 34. 9 39. 5 38. 3 34. 0 seer rere r eee re ine na e nae ee ale we aun 81. 1 34. 2 29. 5 37. 8 46. 2 39. 1 37. 4 (es Yee en ce A ad an n de Ble » eu. 77.3 36. 6 26. 6 35. 9 43. 4 39. 4 36. 4 M > 4 2 o on ran aaa n un ain diigo an a eee ae da a o. 73. 6 34. 5 28. 8 37. 2 41. 4 42. 0 36. 8 Near 68. 1 38. 5 31. 0 37. 8 46. 1 43. 8 38. 4 West Fargo (discharge computed from gage- ___ 24. 5 36 26 33 45 1 54 35. 0 ' Discharge affected by releases from Lake Ashtabula. Not used in computing averages. D180 GROUND-WATER-SURFACE-WATER RELATIONS 3 on I Downstream -> DISCHARGE, IN CUBIC FEET PER SECOND I I meck s T T t 131 I Drift | 35 )- Drift prairie prairie _| Shgyenne Lake Agassiz plain a: Mainly till ~ and & j elta Mainly clay and silt Sheyenne Mainly sand delta 25- ta 0 - 10 20 30 _ 40 RIVER MILES | | Valley City l _4 1 A Aa B COE F Kindred West Fargo 3 f OL _L L4 G HIJ KLM Fraur® 2.-Average discharge of the Sheyenne River, Valley City to West Fargo, September 13-November 19, 1963. Letters refer to partial-record stations shown on figure 1 and referred to in text. by shale. Regionally these deposits have a low per- meability and generally yield small quantities of ground water. However, the valley of the Sheyenne River is a half to three quarters of a mile wide in this reach and has been thought to be underlain by per- meable deposits of outwash and alluvium that would yield substantial amounts of ground water. The lack of substantial increases in streamflow between Valley City and Lisbon during periods of low flow suggests either the absence of permeable deposits in the chan- nel or, if such deposits are present, a lack of hydraulic connection between them and the river channel. Between Lisbon and station A, 14.5 miles down- stream, the flow in the Sheyenne River increased an average of 1.53 cfs. Here the valley is bordered on both sides by till, but the valley floor may be under- lain by somewhat coarser and more permeable ma- terials that discharge ground water into the river. Between stations A and E, a river distance of 21.6 miles, the river flows along the west edge of the Shey- enne delta. The average increase in the discharge measurements in this reach was 3.8 cfs. Here the river is bordered on the west by till and on the east by delta(?) deposits consisting of coarse sand and gravel. Except where modified by sand dunes, the surface of the deltaic deposits slopes generally east- ward. Probably the ground-water drainage divide (fig. 1), as well as the surface-water divide, is rela- tively near the Sheyenne River in the region between stations A and E. Consequently, although the river is deeply incised along the west margin of the delta, only a relatively small amount of ground water drains westward to the river. From station E the river flows east-northeast across the Sheyenne delta and separates it into two segments, a smaller northern segment and a much larger south- ern one. The river flows in a meandering channel, in contrast to the relatively straight channel between stations A and E. The valley floor, which is commonly less than half a mile wide, is from 50 to 100 feet below the main level of the upland on either side, and the river channel is incised from 15 to 25 feet below the valley floor. Test drilling indicates that the deposits on either side of the river valley in the region between stations E and K consist of sand grading eastward from coarse to fine. The deposits are generally more than 50 feet thick. Although a thorough discussion of the origin and stratigraphy of these deposits is beyond the scope of this paper, current geologic studies support Up- ham's theory of deltaic origin. The deltaic deposits form a productive aquifer ex- tending over several hundred square miles south of the Sheyenne River and, to a much lesser extent, north of the river. From station E to station K, a river length of 44.8 miles, the average increase in the dis- charge measurement was 22.5 cfs, which represents a gain of nearly 0.5 cfs per mile of river channel. This increase in flow, which is the largest known for any stream segment of comparable length along the entire course of the river, is produced by ground-water dis- charge from the deltaic deposits adjacent to both sides of the valley. A significant part of the increase in the discharge measurements between stations E and K is due to inflow from short tributaries which head on the Shey- enne delta and whose base flow consists wholly of ground-water discharge from the deltaic deposits. Examination of U.S. Geological Survey 7%4-minute topographic quadrangle maps reveals several tribu- taries extending back into the deltaic deposits from both sides of the Sheyenne River valley between sta- PAULSON tions E and K and, also, east of station K. The largest of these enters the valley from the south, a short distance east of the west boundary of Richland County (fig. 1). Five measurements of the discharge at the mouth of this tributary during the period September 13 to November 20, 1963, averaged 2.2 cfs. Between stations K and M, 7.5 river miles apart, the average of the five discharge measurements de- creased 0.6 cfs. Station M is a short distance east of the scarp that marks the northeastern edge of the delta. Test drilling and surface reconnaissance indi- cate that the deltaic deposits bordering this stretch are composed mainly of silt and very fine sand that yield only small amounts of ground water. Sandpoint wells, which are common throughout much of the delta, are not a successful means for obtaining water in this part of the area. Also, considerable ground water is di- verted eastward or northeastward toward the edges of the scarp rather than into the Sheyenne River valley. Between station M and Kindred, 5.5 miles apart, the average of the discharge measurements increased 1.6 cfs. It is not known whether ground-water inflow is distributed evenly along this segment or is restricted largely to one main locality. Probably most of the inflow occurs a relatively short distance below station M. Earlier workers apparently considered the scarp as the northeastern edge of the delta. However, de- tailed surface mapping indicates a body of sand ex- tending about a mile beyond the scarp and grading eastward or northeastward into silt and clay. Test drilling in the vicinity of Kindred (Dennis and others, 1950, p. 75) indicates that the sand is at least 12 feet thick in places. It is reasonable to assume that most of the inflow is derived from this sand and from springs issuing from the delta scarp. From Kindred to West Fargo the Sheyenne River meanders across the nearly flat surface of the Lake Agassiz plain. The river length between the two sta- tions is 43.6 miles, but the average of the 5 measure- ments made between September 13 and November 19 showed a loss of 3.4 cfs. The lack of ground-water inflow is not surprising inasmuch as the surface de- posits in this region consist of clay and silt having a low permeability. D181 CONcLUsION The substantial increase in discharge of the Shey- enne River along its course across the Sheyenne delta has considerable significance in the appraisal of the hydrologic regimen of this region. The increase in mean monthly discharge for the months of October- February, 1957-62, of 15.1 cfs between the stations at Lisbon and Kindred and the average increase in dis- charge of 28.8 cfs for the five daily measurements made from September 13 to November 19, 1963, is due almost wholly to ground-water discharges from the delta deposits. However, this amount is only part of the total natural discharge of ground water, as sub- stantial quantities are discharged during the warmer months of the year by evapotranspiration in areas where the water table is shallow. Also, ground water is discharged at springs along the scarp of the delta and, probably, as underflow to adjacent permeable bodies. Full utilization of the ground water in the delta deposits depends, of course, both on physical and economic factors Large ground-water yields over sustained periods can be developed only where the physical characteristics of the water-bearing deposits are favorable, such as in the western and central parts of the delta. Although large withdrawals of ground water in areas near the river would reduce inflow to the river and thus cause a decrease in streamflow at downstream points, the problem could likely be allevi- ated by appropriate releases from Lake Ashtabula. REFERENCES Dennis, P. E., Akin, P. D., and Jones, S. L., 1950, Ground water in the Kindred area, Cass and Richland Counties, North Dakota: North Dakota Ground-Water Studies, No. 14. U.S. Geological Survey, 1957-60, Surface-water supply of the United States, pt. 5, Hudson Bay and Upper Mississippi River Basins, U.S. Geol. Survey Water-Supply Papers 1508, 1558, 1628, 1708. U.S. Geological Survey, 1961, 1962, Surface-water records of North Dakota and South Dakota: Open-file reports. Upham, Warren, 1895, The glacial Lake Agassiz: U.S. Geol. Survey Mon. 25, [1896]. GEOLOGICAL SURVEY RESEARCH 1964 MAGNITUDE AND FREQUENCY OF STORM RUNOFF IN SOUTHEASTERN LOUISIANA AND SOUTHWESTERN MISSISSIPPI By V. B. SAUER, Baton Rouge, La. Work done in cooperation with the Louisiana Department of Public Works Abstract.-The relation between magnitude and frequency of individual storm runoff has been determined for streams in southeastern Louisiana and southwestern Mississippi. Graphi- cal correlations indicate that the mean annual, or 2.33-year, storm runoff for any site in the area is 64 second-foot-days per square mile, which is equivalent to a uniform depth of 2.38 inches. It was also demonstrated that the recurrence interval of an individual storm runoff will, in many instances, be significantly different from the recurrence interval of the peak discharge resulting from the same storm. The relation between individual storm runoff and frequency of occurrence has been established for streams in southeastern Louisiana and southwestern Mississippi. Storm runoff is defined, for this report, as the rainfall excess resulting from individual storms and is analyzed as an independent event. Coincident with the problem of relating storm runoff to fre- quency of occurrence, a study was also made to deter- mine whether the recurrence interval of a given storm runoff is the same, or nearly the same, as the recur- rence interval of the peak discharge resulting from the same storm. The study area (fig. 1) includes what is known as the "Florida Parishes" in southeastern Louisiana and about eight counties to the north of the Florida Parishes in southwestern Mississippi. It is bounded on the east by the Pearl River and on the west by the Mississippi River. Topography of the 7,500-square- mile area is varied, ranging from rolling hills to flat, swampy lands. Average annual rainfall ranges from about 56 inches in southwestern Mississippi to 66 inches in southeastern Louisiana. The total runoff, or volume, was computed for every storm that had a peak above a base so selected as to give an average of 3 to 5 floods a year at each of 17 gaging stations in the area. These stations, with drainage areas ranging from 0.73 to 1,330 square miles, were selected for this frequency study on the basis of length of record ; all have 8 or more years of record. The base period for the study was 1940-61. Although the total runoff for several storms was computed for each year, only the maximum storm runoff for each year was used. Correlations with nearby stations were used to extend the records of maximum annual storm runoff of some stations so that it was possible to com- pute all records for the same base period. 93° 91° 89° 35° [- I I < 3 | g Gs I ———————|§ MISSISSIPPI |- $ I feets \ LOUISIANA y \ A f \ ff" | $1: / y ae C 33° 5 29° GULF or MEXICO i 0 100 MILES hen FraurE 1.-Index map showing area of study. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D182-D184 D182 SAUER Storm runoff is direct runoff only, and this is com- puted as the total runoff minus base flow. Recession curves were developed for each station and were used to separate the overlapping runoff from two or more storms. Before separation of runofifs that apparently overlapped, the hydrograph and rainfall records were carefully inspected to ensure that double peaks were not the effect of tributary timing. This procedure evaluates the runoff from each storm independently. An annual-series frequency analysis was prepared for each station according to the procedures described by Dalrymple (1960). The mean annual storm run- off, in second-foot-days, was determined from each frequency curve at the 2.33-year recurrence interval. These values were then related to drainage area as shown on figure 2. The ratio of storm runoff (at other recurrence intervals up to 25 years) to mean annual storm rumoff was computed for each station. The median of these ratios, for selected recurrence inter- vals, was plotted to obtain the regionalized frequency curve shown on figure 3. The comparable curve for annual peak discharges (Sauer, 1964) is also shown on figure 3. The mean annual storm runoff, as determined from figure 2, is equal to 64 second-foot-days per square mile for any basin in the study area. Converted to a uniform depth over the area, this is equal to 2.38 inches. This value multiplied by the values from the frequency curve on figure 3 results in the curve shown on figure 4. $09,900 74 For- mert ror T-T T TTH T 10,000 T IIIIHi L lllll|| T 1 1000 T IIIIIII 1 IIIIIII 1 100 MEAN ANNUAL STORM RUNOFF, IN SECOND-FOOT-DAYS 1 lllllll {09 t ail - sta a Ltn] 1 I 1 10 100 DRAINAGE AREA, IN SQUARE MILES | lllllll 1000 20 Fraurs 2.-Relation of drainage area to mean annual storm runoff. to - Comparable curve for e. annual peak discharge\// -o RATIO OF INDIVIDUAL STORM RUNOFF TO MEAN ANNUAL STORM RUNOFF 0 $- .3. 54 | | ps a | | 1.1 1.5 2 5 10 20 RECURRENCE INTERVAL , IN YEARS Fiaur® 3.-Regional frequency curve of annual storm runoff. Based on the data and analysis of this study, the standard deviation of the mean annual storm runoff is 13 percent, and the standard deviation of the 25- year frequency storm runoff is 17 percent. Further investigations were made to determine whether the recurrence interval of the runoff of a given storm was the same, or nearly the same, as the recurrence interval of the instantaneous peak dis- charge resulting from the same storm. The recur- rence intervals of storm runofis were determined from the frequency curves presented in this report; those of instantaneous peak discharge were determined from flood reports by Sauer (1964) and by Wilson and Trotter (1961). Eight stations, selected randomly from the 17 sta- tions used in the analysis, were used to compare the recurrence intervals of storm runoff and peak dis- charge for each of 87 storms having runoff recurrence intervals greater than 1.7 years. It is evident from this comparison, shown graphically on figure 5, that STORM RUNOFF, IN INCHES o pu OEI | | $. 1 | | 1.1 1.5 2 5 10 20 RECURRENCE INTERVAL, IN YEARS FraurE 4.-Relation of individual storm runoff, in inches, to recurrence interval. C> fants Co > G 0 10 sea 1 | RECURRENCE INTERVAL OF STORM RUNOFF, IN YEARS &n I 1 | {2a - LEL _L 1 i 5 10 30 RECURRENCE INTERVAL OF PEAK DISCHARGE, IN YEARS Fraur® 5.-Variation between the recurrence intervals of peak discharge and the corresponding storm runoff. V's above and to the right of points at the top of the graph indicate that these points have a recurrence interval of greater than 25 years in the direction of the V. a wide variation exists between the' recurrence inter- vals computed for storm runoff and corresponding peak discharge. This variation can be explained by several factors that affect the relation between storm runoff and peak discharge. Two storms having iden- tical total runoff at a station may have considerably different peaks because of different storm durations or SURFACE WATER different distribution of rainfall over the basin. Di- rection of storm travel will cause variations in the relation between peak and runoff. Another significant factor is the rate of flow in the channel at the time of storm runoff, which may include only base flow or base flow plus flow from the recession of a previous storm. There are probably other factors of lesser significance that also affect this relation. It follows, therefore, that recurrence intervals of peak discharge cannot be determined with any reliability from re- currence intervals of storm runoff. Although no direct proof resulted from this study, it is evident that rain- fall-frequency relations cannot be used to determine the recurrence intervals of peak discharge. In conclusion, this report shows that the recurrence intervals for a storm runoff of a particular magnitude (within the limits defined) can be determined reliably for any site in the study area by using curves pre- sented in this report. It is also demonstrated that the recurrence interval of a storm runoff will, in many in- stances, be greatly different from the recurrence in- terval of the peak discharge resulting from the same storm. REFERENCES Dalrymple, Tate, 1960, Flood-frequency analysis: Survey Water-Supply Paper 1543-A, 80 p. Sauer, V. B., 1964, Floods in Louisiana, magnitude and fre- quency, 2d ed.: Louisiana Dept. Highways, 402 p. [In press] Wilson, K. V., and. Trotter, I. L., Jr., 1961, Floods in Missis- sippi, magnitude and frequency: Mississippi State High- way Dept., Traffic and Planning Div., 326 p. U.S. Geol. GEOLOGICAL SURVEY RESEARCH 1964 CORRELATION AND ANALYSIS OF WATER-TEMPERATURE DATA FOR OREGON STREAMS By ALBERT M. MOORE, Portland, Oreg. Work done in cooperation with the Oregon State Water Resources Board, U.S. Public Health Service, U.S. Bureau of Reclamation, U.S. Soil Conservation Service, and Corps of Engineers, Department of the Army Abstract.-For most Oregon streams, spot observations of water temperature can be correlated with continuous thermo- graph records of water temperature in another stream to obtain reasonably accurate figures of monthly maximum, mini- mum, and mean water temperature at the spot-observation site. Many of these correlations vary seasonally, and some of the variations apparently are caused by differences in the orientation of the stream courses. The correlations can be a useful tool in assessing the effect of reservoir operations on downstream water temperature. In a study of the temperature of water in Oregon streams, spot observations of water temperature were correlated with continuous thermograph records. The spot observations, obtained as part of the regular stream-gaging program, have been made at more than 200 sites during periods ranging from 4 to 16 years, and at the rate of one measurement every 5 or 6 weeks at each site. The thermograph records used in the correlations are 8 to 12 years in length and may be on another stream or on the same stream as the spot- observation records. INTERSTREAM TEMPERATURE CORRELATIONS The correlations are developed by plotting observed temperatures at a spot-observation site against the temperature recorded for the same date and hour at a site where a continuous thermograph recorder is op- erated. This procedure allows for the diurnal fluctua- tions of stream temperatures. This type of correlation results in a curve or curves of relation between water temperature at the two sites. These curves are utilized to estimate for the spot-observation site monthly water temperatures corresponding to the known monthly water temperatures for the thermograph site. Another type of correlation developed for this study relates monthly records of water temperature for the thermograph site to those for another thermograph site; the resulting curve or curves are used to fill gaps in the record at one or both sites. The standard error for both types of correlation generally ranged from 1° to 2°F. These correlations, although in themselves accomplishing significant pur- poses, are described largely to provide background material for findings that resulted from their use. EFFECT OF STREAM ORIENTATION ON WATER TEMPERATURE The second type of correlation, that of water tem- perature of two thermograph sites, when used to fill a gap in the short thermograph record for Five Rivers near Fisher, drew attention to the fact that orientation of the stream can affect water temperatures. Correla- tion was made with the equally short record for Fall Creek near Alsea, and the curve of relation was found to change seasonally, as shown by figure 1. During the winter the two streams are at about the same temperature, but in the summer Five Rivers is sub- stantially warmer than Fall Creek. The two streams drain areas that are culturally and geologically simi- lar, and neither has significantly large spring-flow contributions. When possible reasons for this diver- gence were sought, it was found that Fall Creek has heavily wooded banks and runs nearly north-south, while Five Rivers flows generally east to west and is not so heavily wooded along the banks. Furthermore, even in those reaches of Five Rivers where the general direction is north-south, there are wide sweeping curves that result in most of the stream having an U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D185-D189 D185 D186 T T T T [ T 70 |- FIVE RIVERS NEAR FISHER (EAST-WEST) July and August E 60 |- May, June, September, and October f u U ma e o I § November to April a P e (2 points) c S 40| s o = 70 |- = ul c a é 60 |- i u DRIFT CREEK NEAR SALADO fou s (NORTH-SOUTH) ~ * % (3 points) 40 | 1 | I 1 40 50 60 TEMPERATURE OF FALL CREEK NEAR ALSEA, IN DEGREES FAHRENHEIT FigurE 1.-Correlation of monthly extremes of water temperature of Fall Creek near Alsea (a north-south stream) with corresponding water temperatures of Drift Creek near Salado (north-south) and Five Rivers near Fisher (east-west). east-west orientation. As a further check on the effect of shading provided by north-south orientation, an- other north-south stream (Drift Creek near Salado) was selected for correlation with Fall Creek near Alsea. Excellent correlation, with no seasonal varia- tion, was found for these two north-south streams (hg.:1). Another example of the effect of stream orientation was observed during the summer of 1963 when the U.S. Geological Survey obtained water-temperature records on both North and South Forks of the Trask River. At the time the records were begun, a local resident pointed out that North Fork was preferred over South Fork as a "swimming hole" because it was warmer. The first records-in July showed that North Fork was indeed 4° to 8°F warmer than South Fork. The latter was tested with a hand thermometer for several miles upstream to see if there was evidence of any cool spring-flow contributions, and none was found. Evidently the difference was due to the north- south orientation of South Fork and the east-west orientation of North Fork This conclusion was fur- ther supported when cloudy days resulted in closer agreement between the temperatures of the two streams. In fact, when cloudy weather continued for 2 or 3 consecutive days, the temperatures of the two SURFACE WATER streams became practically identical. Furthermore, a comparison of monthly mean temperatures for the two streams showed that North Fork was 4° to 5°F warmer than South Fork during the sunny months of July and August, but that this difference decreased to 3° and 2°F, respectively, for September and October, when more cloudy weather prevailed. Other examples of the effect of stream orientation were found when the temperature of Oregon streams was compared with air temperature for the summer months. Mangan (1946 p. 9, 10) in discussing water temperature in Pennsylvania streams states, ". . . the mean monthly temperature of the water from May through November, will slightly exceed the monthly air temperature of the region." This general statement does not hold for Oregon streams, however. Generally, those streams that are much exposed to direct sunlight do tend to have monthly mean temperatures that exceed monthly mean air temperature during the summer months. Streams with large spring-flow contributions have monthly mean temperature lower than monthly mean air tem- perature in the summer, as have those streams with a north-south orientation and steep canyon walls or wooded banks such that exposure to direct sunlight is minimized. Figures 2 and 3 compare monthly water temperatures for selected years at nine thermograph sites with corresponding air temperature at nearby U.S. Weather Bureau stations. The same year could not be used for all nine thermograph records shown on figures 2 and 3 because there was no single year when all were in operation. At four sites (fig. 2) the monthly mean water temperature during the summer is higher than the monthly mean air temperature; each of these four streams has a general east-west orientation upstream from the thermograph station. The other five sites (fig. 3) have summer temperatures that are lower than air temperature. Breitenbush River near Detroit, although having an east-west orientation, is colder than air temperature during the spring and summer because of large spring-flow con- tributions. A similar relation between water and air is found for North Umpqua River at Winchester, not only because of large amounts of spring flow but also because of snowmelt contributions extending into the summer months. South Fork John Day River near Dayville, Clatskanie River near Clatskanie, and Grande Ronde River at La Grande do not have large amounts of spring flow but are colder than air tem- perature during the summer, largely because of shad- ing provided by north-south orientation and wooded banks. MOORE T T T T T 7 T T T 60 50 40 30 20 80 70 60 50 40 30 70 60 50 40 80 70 60 50 40 |- Air temperature at Roseburg _| 30 1 1 i 1 1 1 1 1 1 1. j | Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. TEMPERATURE, IN DEGREES FAHRENHEIT 2.-Comparison of air temperature with monthly mean water temperature of east-west streams. EFFECT OF RESERVOIRS ON DOWNSTREAM WATER TEMPERATURES Correlation of spot observations of water tempera- ture with a thermograph record provides a useful tool for assessing the effect of a reservoir on downstream water temperatures . A good example of the use of such a correlation is the study made of the effect of the Detroit Reservoir. This reservoir, on the North Santiam River, is used for flood control, power gen- eration, and recreation; it was first used for storage in 1953. Its maximum depth is 290 feet, and its oper- ating range is 144 feet. Water from well below the surface is released during summer, but in the autumn, when the reservoir is drawn down for flood control, warmer water from nearer the surface is released. From July to September there is little increase in flow in the reach of the river 50 miles or more below De- troit Dam, because tributary inflow is small and, below Mahama, diversions tend to offset inflow. Inflow and outflow thermograph records are avail- able for the reservoir, but farther downstream, at Mehama (North Santiam River) and at Jefferson (Santiam River), only spot-observation records are available for 1947 to 1962. These sites are, respec- tively, about 22 and 51 miles below Detroit Dam (fig. 4). The correlation procedures followed for Mehama were also used for Jefferson, but only those for Mehama are discussed here. The thermograph record for Breitenbush River, one of the streams flow- ing into Detroit Reservoir, extends from 1951 to 1962. Separate correlations with the Breitenbush thermo- 742-652 O-64--13 --- I 60 |- 1954 T I i T T T Clatskanie R\iver near Clatskanie 40 |- = Air temperature at Clatskanie 79 |- 1956 Air temperature at La Grande be TEMPERATURE, IN DEGREES FAHRENHKHEIT 40 ' | - -** Bre 30 1 1 I I | I 1 Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. itentlyush Ifiverlnear {Detrolit‘ FraurE 3.-Comparison of air temperature with monthly mean water temperature in spring-fed or in north-south streams. graph record were made for spot observations of water temperature at Mehama prior to and subsequent to the filling of Detroit Reservoir. That is, the 1951-52 spot observations at Mehama were correlated with the 1951- 52 thermograph record for Breitenbush River. By entering this correlation with known period-of-record (1951-62) mean monthly temperatures for Breiten- bush River, the corresponding mean monthly water temperatures at Mehama for the same period (1951- 62) were estimated. These are the mean monthly tem- peratures that would have occurred at Mehama if Detroit Reservoir had not been built. A similar cor- relation for the period 1953-62, when entered with the same 1951-62 mean monthly temperatures for Breiten- bush River, yielded the mean monthly temperatures that would have existed at Mehama for 1951-62 if Detroit Reservoir had been in operation for the en- tire period. In other words, the 2-year and the 10-year correla- tions both resulted in estimates of mean monthly tem- perature at Mehama for the 12-year period 1951-62, but the first excluded and the second included the effect of Detroit Reservoir. Subtraction of one set of mean monthly temperatures from the other shows the effect of Detroit Reservoir at Mehama. The accom- panying table lists only the effect of the reservoir, not the water temperatures themselves. D188 SURFACE WATER 45" 30' 122'15' I map 44°45" 1 Area of sketch Jefferson I I I Stayton O Santiam Mehama Niagara 0 Big cLIrF pam Mill City DETROIT DAM 15 MILES [L242 03-1 1 "3 I | | FiGur®E 4.-Sketch of in computing the Detroit Dam. North Santiam River, showing location of various thermographs (T) and spot-observation sites (S) used effect of Detroit Reservoir on downstream water temperatures. Figures indicate river mileage below Effect of Detroit Reservoir on monthly mean water temperature downstream Distance Change in monthly mean water temperature, in degrees Fahrenheit, caused by operation of Detroit Reservoir Drainage below ; Site area Detroit (sq mi) Dam Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. (miles) NMingarac............. 453 3. 6 +4 +5 +3 +1 0 -1 -1 -1 -4 -8 -T -4 MceBama............. 665 22. 2 -1 +1 +2 +1 +1 +1 0 -1 -4 -6 -8 -T Jefferson... 1,790 51. 3 -3 -3 a 0 0 -1 0 0 -1 -2 -3 -5 Release of reservoir water of relatively constant temperature should result in poor correlation between spot observations of water temperature immediately below the reservoir and a thermograph record on an unregulated stream. However, if the spot observations are made at a site several miles below the reservoir, good correlation with a thermograph record is usually found because in those few miles the water is subjected to the same natural conditions of solar radiation, air temperature, and so forth, that are affecting water temperature at the thermograph site. The correlations between the thermograph record for Breitenbush River and spot obsrvations both at Mehama and at Jefferson are reasonably good. The following conclusions can be drawn from the data shown in the accompanying table: 1. Maintaining a nearly full reservoir during the sum- mer and drawing the reservoir down in the au- tumn results in cooler than natural water tem- peratures at Niagara during the summer, and warmer than natural in the fall. 2. The cooling during the summer continues undimin- ished at Mehama, more than 20 miles downstream, and to a lesser extent at Jefferson, more than 50 miles downstream. 3. The cooling effect of the reservoir extends later into the summer and fall at the downstream sites. The effect noted in item 3 above is believed to be accounted for by the changed water-temperature gradient between Niagara and the downstream sites, resulting from reservoir regulation that not only has lowered the water temperature but has changed the flow pattern. For example, the natural temperature difference between Niagara and Mehama for July is +5°F (56° to 61°F), but with Detroit Reservoir in operation the difference is +7°F (48° to 55°F). The regulated July flow is about the same as the natural flow, but, with water temperature at Niagara 8°F MOORE cooler than under natural conditions, evaporation is reduced and the heat that would have been required for evaporation is available for warming the water. This same effect is present in August and September, also, but is more than offset by the fact that regulated flows are well in excess of natural flows. With more water to be warmed, the natural gradients between D189 Niagara and Mehama of +5°F and +4°F for August and September are cut to +4°F and -|+-1°F, respec- tively. REFERENCE Mangan, J. W., 1946, Temperatures of natural waters in Penn- sylvania: Pennsylvania Dept. of Forests and Waters. GEOLOGICAL SURVEY RESEARCH 1964 ELIMINATION OF THERMAL STRATIFICATION BY AN AIR-BUBBLING TECHNIQUE IN LAKE WOHLFORD, CALIFORNIA By GORDON E. KOBERG, Denver, Colo. Work done in cooperation with the Escondido Mutual Water Co. Abstract.-Use of an experimental air-bubbling system at Lake Wohlford, Calif., resulted in the elimination of thermal stratification, definite improvement in taste and odor of the water, and a net reduction in evaporation of 35 acre-feet (5 percent) in 1962. A study was made in 1962, in collaboration with the Escondido Mutual Water Co., of the effect of an air-bubbling system on the artificial mixing of ther- mally stratified water in Lake Wohlford, Calif. The air-bubbling system caused a marked improvement in the quality of water and a reduction in seasonal evaporation rates. Lake Wohlford is a canyon-type reservoir formed by an earth-fill dam on Escondido Creek, 7 miles northeast of Escondido, Calif., and about 30 miles north of San Diego. The lake has a capacity of 7,000 acre-feet at full pool with a corresponding surface area of 222 acres. During the period of study the contents of the reservoir averaged 2,500 acre-feet with a surface area of 130 acres. The climate at Lake Wohlford is such that the temperature of the water always exceeds 4°C, the temperature of maximum density of water. The lake is used for storage of water for irrigation and domestic supply and as a recreational facility. The seasonal changes in climate at Lake Wohlford are accompanied by a change in the distribution of temperature in the lake. During the spring and sum- mer, the distribution of temperature is such that the hypolimnion or lower stratum of water is heated at a much slower rate than the epilimnion or upper stratum. Consequently, the hypolimnion is almost stagnant because cold water, being denser, remains on the bottom. During the period of stagnation, the processes tending to produce a uniform distribution of dissolved substances are very slow, and certain undesirable substances such as hydrogen sulfide in- crease in concentration until they reach an undesirable level, while other substances such as oxygen are de- pleted. Changes in the distribution of lake temperature have an effect on the life cycle of the various organ- isms in the water, such as plankton and algae. These organisms tend to proliferate at certain levels in the lake, depending on the temperature peculiar to each genus, and then to die and fall to the bottom. As the organic matter accumulates on the bottom, the decay- ing process increases the demand for oxygen in the hypolimnion until oxygen is almost or completely depleted. £ In the summer of 1959, most varieties of fish in Lake Wohlford died, probably because of the lack of dissolved oxygen in the water. In the summer of 1960, measurements indicated that the concentration of dis- solved oxygen in the hypolimnion was reduced to 1 part per million, and in the epilimnion, to 6 ppm. During these two periods, the water delivered to the city of Escondido had an unpleasant taste and odor. Because of the problems of water quality, experi- ments were undertaken in 1961 to determine the feasibility af bubbling air from the bottom of the reservoir to mix the lower and upper strata of water. The results of these experiments indicated a definite improvement in the dissolved-oxygen concentration, and a permanent air-bubbling system was installed. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D190-D192 D190 KOBERG This system consists of a 210-cubic-foot-per-minute (free air) compressor powered by a 50-horsepower electric motor. Air is conducted from the compressor through a 2-inch galvanized pipe which extends into the lake a sufficient distance to cool the air. Attached to the end of the pipe is 1i4-inch polyvyinyl-chloride plastic tubing that conducts the air to the area where it is forced into the bottom water, approximately 40 feet below the surface. The last 60 feet of the plastic tubing is perforated with 90 holes, %4, inches in diam- eter, spirally located to equalize the thrust of the es- caping air. The permanent-air-bubbling system was placed in operation on April 18, 1962. At first the system was operated only during approximately 9 daylight hours each day. The operational plan was based on the hypothesis that as the bottom water was brought to the surface by the bubbles, it would be heated by solar radiation and then remain at the surface. Experi- mental tests late in the summer of 1962 indicated that the water did not remain at the surface but sank almost immediately and that the rate of maximum mixing of the water in the lake was not achieved until after approximately 24 hours of continuous operation. Therefore, the plan of operation was changed so that the system is operated continuously until the lake is thoroughly mixed or isothermal. The time required for complete mixing ranges from 24 to 48 hours. Ap- proximately 3 days after the air-bubbling operation, thermal stratification begins to form in the lake and the cycle is repeated. In 1962, the air-bubbling system was operated in- termittently from April 18 to September 5. During this period, the concentration of dissolved oxygen was maintained above 5 ppm throughout the lake with the exception of a 1-week period in August when it dropped to 4 ppm. The dissolved-oxygen concentra- tion of 5 ppm is considered the safe limit for trout production. During the remainder of the year, the natural mixing motion of the wind maintained the concentration of oxygen above 5 ppm. Water delivered to the city of Escondido for do- mestic purposes in 1960 required a maximum dosage rate of chlorine of 12 ppm. During 1962, while the bubbler system was in operation, the maximum dosage rate was reduced to 7 ppm. The decrease in dosage rate is attributed to the removal of hydrogen sulfide in the hypolimnion by the air-bubbling system. The removal of the hydrogen sulfide would result in a lower chlorine requirement to meet health standards because less chlorine would be needed to oxidize H8, and free available residual chlorine would be obtained at a lower dosage rate (Laubush, 1958). The reduc- D191 tion in the rate of chlorine dosage for 1962 resulted in monetary saving that was enough to pay for the power required for the operation of the compressor. The improvement in taste and odor of the water de- livered to the city of Escondido during 1962 is difficult to evaluate quantitatively. However, the citizens of Escondido must have noted a definite change in taste and odor of the water, because in 1963, complaints were received by the water company only when ther- mal stratification began to develop in the lake and the dissolved oxygen concentration in the hypolimnion was reduced. During the spring and summer of 1962, the mixing of the cold water in the hypolimnion with the warm water in the epilimnion reduced the temperature of the water surface, which in turn reduced the evapo- ration rate. Measurements of evaporation were made by the energy-budget and mass-transfer methods (Har- beck and others, 1958). Before changes in the evaporation rates could be determined, a comparison of the temperatures of the water surface was made between the monthly means determined for the period 1959-61 and the monthly means for 1962. The comparison indicated that the air-bubbling system reduced the temperature of the water surface 0.5°C, 2.2°C, and 1.3°C in May, June, and July, respectively, and increased the temperature 0.9°C, 1.4°C, and 0.3°C in October, November, and December, respectively. During the period when the temperature of the water surface was lower in 1962, more energy than normal was stored in the lake by the decrease in the evaporation rate and by net gains in radiation and conduction because of the lower tem- peratures of the water surface. In August and Sep- tember, the temperature of the water surface was nearly normal, and during the fall was higher than normal because of the time required to dissipate the additional energy by increasing evaporation, radia- tion, and conduction. The changes in the evaporation rates attributed to the air-bubbling system were computed by the mass- transfer method. A comparison of the monthly evapo- ration rates between 1962 and the period 1959-61 for the months of May, June, and July indicated that evaporation was reduced a total of 3.3 inches and for the months of October, November, and December evaporation was increased 1.3 inches. Because of the limited data available, it is difficult to explain why the increase in evaporation during the fall months did not equal the decrease in the summer months. The regulation of stage for Lake Wohlford is such that the volume of water saved by the changes in evaporation rates is greater than that which would D192 result from a constant stage throughout the year. During the winter and spring, inflow is stored in the lake and is maintained at the spring level for recrea- tional purposes throughout the summer. In the fall, the stage is lowered in anticipation of winter and spring runoff. With this type of operation of net decrease in evaporation of 35 acre-feet or 5 percent was attributed to the air-bubbling system in 1962. The mixing of thermally stratified water in lakes and reservoirs by the use of an air-bubbling system has been successfully tried by other investigators such as Reddick (1957) and Heath (1961). Although their systems are different in design, the purpose of each system is the same. The efficiency of each design in mixing the water is unknown, mainly because the cold R ENGINEERING HYDROLOGY water brought to the surface immediately sinks to the bottom. Criteria for design of systems for other reservoirs and lakes is not available because the artifi- cial mixing of thermally stratified water is not thor- oughly understood. REFERENCES Harbeck, G. E., Kohler, M. A., Koberg, G. E., and others, 1958, Water-loss investigations-Lake Mead studies: U.S. Geol. Survey Prof. Paper 298, 100 p. Heath, W. A., 1961, Compressed air revives polluted Swedish lakes: Water and Sewage Works, v. 108, p. 200. Laubush, E. J., 1958, Chlorination of water: Water and Sewage Works, v. 105, p. 411. Reddick, R. M., 1957, Forced circulation yields multiple benefits at Ossining, Sewage Works, v. 104, no. 6, p. 231-237. of reservoir water N.Y.: Water and GEOLOGICAL SURVEY RESEARCH 1964 FIELD METHODS FOR DETERMINING VERTICAL PERMEABILITY AND AQUIFER ANISOTROPY By EDWIN P. WEEKS, Madison, Wis. Work done in cooperation with the University of Wisconsin Geological and Natural History Survey and the Wisconsin Conservation Department Abstract.-The ratio of horizontal to vertical permeability in stratified sediments can be found by either a finite-difference solution of the differential equation for flow near a pumped well or a type-curve solution of a modified form of the analyti- cal equation for drawdowns near a partially penetrating well. Applied to data from an aquifer test of glacial outwash in central Wisconsin, the type-curve solution provided more re- liable values for coefficients of transmissibility (T) and storage (8) than those obtained from the nonequilibrium formula. A knowledge of vertical permeability and aquifer anisotropy is necessary for solving various problems concerning three-dimensional ground-water flow. For example, vertical permeability must be known if the maximum infiltration rate in a recharge area is to be determined, and the ratio of horizontal to vertical permeability is needed for computation of seepage under dams and for analysis of the drawdown effects of partially penetrating wells. The permeability across beds of clastic sedimentary rocks generally is much less than the permeability parallel to the bedding planes. For the methods of analysis described in this paper, it is assumed that the beds are horizontal and that the horizontal and verti- cal permeabilities are measured parallel and normal, respectively, to the bedding planes. Anistotropic permeability in clastic sediments is due in part to the orientation of the constituent grains. Plate-shaped grains within the sediments tend to be oriented with their flat surfaces approximately parallel to the bedding plane. Such orientation minimizes the vertical cross-sectional area and, by increasing the tortuousity of the vertically interconnected pores, re- duces the vertical permeability. Anisotropic permeability in sediments is due in part also to intercalation of coarser and finer materials. The horizontal movement of water under a given head loss is affected only slightly by the presence of thin beds of fine-grained material of relatively low permea- bility within sediments of higher permeability, because most of the water is transmitted through the beds of coarser material. On the other hand, vertical move- ment of water under a given head loss is much less in interlayered coarser and finer materials than in an isotropic aquifer, because the water must pass through each fine-grained bed with a relatively sharp decline in head. Thus the head decline with depth accom- panying vertical movement of water in stratified sedi- ments is quite nonuniform. For many problems in- volving vertical flow of ground water in relatively thick aquifers, the nonuniform head declines may be averaged by considering the aquifer to be a homo- geneous bed with low vertical permeability. This report is one of several resulting from an in- vestigation of the interrelationship of ground water and surface water in the Little Plover River basin, Portage County, Wis. It describes two field methods for determining the rates of horizontal to vertical permeability from data on changes in head due to pumping a nearby well. One method is based on a finite-difference technique, the other on a type-curve solution. Both methods may be used with data on water-level drawdown in piezometers (observation wells open only at the bottom) near partially pene- trating wells that tap either artesian or water-table aquifers. Only the finite-difference method may be used with drawdown data from piezometers near a U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D193-D198 D193 D194 THEORETICAL fully penetrating well in a water-table aquifer. For both methods, the data used must be obtained from a relatively large sample of the aquifer. The values for the permeability ratio computed by either of these methods include factors for anisotropy due both to grain orientation and to intercalation of fine- and coarse-grained materials within the aquifer. THE FINITE-DIFFERENCE METHOD The finite-difference method of determining aquifer anisotropy was suggested to the author by R. W. Stallman of the U.S. Geological Survey. This method is based on a finite-difference solution of the modified basic differential equation for radial flow with vertical flow components (Stallman, 1963, p. 208): 1 os [673+ r or where P,=horizontal permeability radially from the pumped well, P,=vertical permeability, s=drawdown, or change in head due to pumping, r=radial distance from pumped well to point at which s is observed, z=vertical distance from base of aquifer to point at which s is observed, +P =0 622 (1) Letting £=log r, equation 1 may be written in finite- difference form for any point (p,») corresponding to (€, 2) (Stallman, 1963, p. 210) as: AE \" TNs ) S2) ~0, - (2) F; #nx-1 ~ 28n+8n+1+Fr< where AE—logr’l+1 —Iog » and (3) I' r~1 Az=vertical spacing of piezometers. As these equations were derived for artesian flow, they are not strictly applicable to flow in unconfined aquifers. However, for water-table aquifers in which the drawdowns due to pumping are small in comparison to the initial saturated thickness of the aquifer, the equations should yield results that are approximately correct. Data for solving equation 2 were obtained by in- stalling an array of piezometers in a vertical plane through the pumped well (Pt-279 or Pt-340) (fig. 1). Two piezometer arrays were installed for this study, one near well Pt-279, with r, at this site equal to 150 feet, and the other near well Pt-340, with r, equal to 80 feet. Drawdowns in the piezometers were measured HYDROLOGY periodically while the well was being pumped, and graphs of s versus time were plotted. From the data plots, values for 85-1, 8», #p41, 82-1, 81, and $141 were de- termined for a given time, and the resulting values were used in equation 2 to determine the P,/P, ratio. The computed ratio of horizontal to vertical permea- bility at well Pt-279 was about 20:1 and at well Pt-340 was about 25:1. However, if the accuracy of head measurement is assumed to have been +0.005 foot, the ratio could range from 10:1 to 40:1 at well Pt-279 and from 13:1 to 50:1 at well Pt-340. Further- more, an error in the measured value of s,,, of +0.01 foot would cause the ratio to range from 5:1 to co:l at well Pt-279 and from 7:1 to co:1 at well Pt-340. These figures indicate that a high degree of accuracy is required of the data and, hence, that the finite- difference method is of limited usefulness in determin- ing anisotropic permeability. Furthermore, minor variations in the piezometric head due to local non- homogeneities of the aquifer would make the computed ratios meaningless. The method might prove much more precise if r, were smaller, for if the piesometer array is located near the pumped well, vertical flow components are more pronounced and the head sum- mation is more accurate than if the piezometer array is located far from the pumped well. Also, the method might be more applicable to data from other aquifers. AE AE Land surface gan- *~ - & W_ater fable M( 0: [[De Co p+1l In n-1 n, p n+1 AZ { -Pumped well p-i Glacial outwash Crystalline rock FiaurE 1.-Sketch showing the array of piezometers used to determine the ratio of horizontal to vertical permeability by the finite-difference method. Sketch is orthogonal, and the A's, which are logarithmic functions of r (see text), conse- quently are unequal. WEEKS TYPE-CURVE METHOD The type-curve method of determining aquifer anisotropy is based on a modification of an analytical equation derived by Hantush (1961a, p. 90, eq. 8a) for the drawdown distribution indicated by piezometers located near a partially penetrating well that discharges at a constant rate. The equation derived for isotropic aquifers is: 1 14.6 I 'd pi wen term w m} where s=drawdown, in feet; Q=discharge, in gallons per minute; T=coefficient of transmissibility, in gallons per day per foot; {1878 CTH (4) U in which r=distance, in feet, from pumped well to piezometer ; S=coefficient of storage; and t=time, in days, since pumping began; W(u)=exponential integral (Ferris and others, 1962, p. 96-97); Fit d sy. 4m nar (fi’a’a’a ";:d=# 3 2 K 7,7) mrl ._ nid nz sin ---sin -- ) cos m m &" (5) in which m=aquifer thickness, in feet; I=depth from top of aquifer (or water table) to bottom of screen in pumped well; d=depth from top of aquifer (or water table) to top of screen in pumped well; z=depth from top of aquifer (or water table) to bottom of piezometer; K,-=modified Bessel function of the second kind and zero order (Ferris and others, 1962, p. 115). Equation 4 may be modified to account for aniso- tropic permeability conditions by multiplying the term r/m by (P,/P,)"#. A similar modification was used by Muskat (1937, p. 279) to determine the steady- state drawdown in a partially penetrating well tapping D195 an anisotropic aquifer. Equation 4 thus modified becomes: llMGQW "#g & ] (in%r_5_7fl ”If, (6) Equation 6 is valid for isotropic artesian aquifers if t>g§ (Hantush, 1961a, p. 90), where P is the per- meability of the aquifer. For anisotropic artesian aquifers, t would be limited by the vertical perme- ability and the equation would be valid when t>gl7§' Although equation 6 was derived specifically for artesian flow, it is applicable to the response of water-table aquifers after vertical flow components resulting from changes in the position of the water table become (Boulton 1954, p. 565). The type-curve solution is a convenient method for using equation 6 to analyze aquifer-test data. If as- sumed values of P,/P, are used, values of #i 1 (P, ”(l d) 23 nK”[( X > ] ( nal nid nrz sin -- )cos --- m m m may be computed for each observation well from the appropriate values of m, r, I, d, and z. - Values of | may be obtained by computing IE) and looking up the corresponding K,(x) value from a table of the modified Bessel function of the second kind and zero order (Ferris and others, 1962, p. 115). Values of the term na Z nal nid sin -- -sin -- )cos m d may be computed quickly to 1 percent accuracy. Individual terms of the summation approach zero as » becomes large; for values of r (P* #B -» D196 the value of the summation may be determined to the necessary degree of accuracy from about 20 terms, and for values of £ (if- 5 m \P,]) _- or greater, the value may be computed from 3 or 4 terms. In order to use the type-curve solution, the computed values of ¢. [LGZY Af. £ 'Lm\P,;]/' 'm mim should be added to the various values of W(w), and plots of v versus h $ ¢ m m m for each piezometer should be prepared on logarithmic paper. - The type curves computed for each piezometer for a given value of P,/P, should be plotted on the same graph to form a family of curves. Several families of type curves should be prepared, one for each of several assumed values of P,/P,. Type curves prepared by this method were used to analyze data obtained from an aquifer test on well Pt-279 tapping glacial outwash in the Little Plover River basin, Portage County, Wis. The well was pumped at a rate of 1,060 gallons per minute for 74 hours, and measurements were made of the drawdown in 21 piezometers installed along 4 lines radiating from the pumped well (fig. 2). Each piesometer consisted of a 1%4-inch ID pipe fitted with an 18-inch well point. The drawdown data obtained during the test were prepared for analysis by plotting, on logarithmic paper, values of s versus for each piezometer. As the data for all the piesometers along one line were plotted as a single graph, four families of curves resulted. Each family of data curves was compared to the type-curve families of v versus fa: 1 ~d z W(u)+f.[ (P) wal Then the data-curve family was superimposed on the best fitting type-curve family, and a match point for the two curve families was determined as shown on figure 3. Values for the terms u, W(u)+f,|: (P Vl d 2 i _} . m s, and r°/t were determined at the match point and these values, along with the measured discharge from the well, were used to solve for T and S in the equations THEORETICAL HYDROLOGY rec ca) m m m S=1ar (@) The ratio P,/P, was determined from the value for the best fitting type-curve family, and the vertical permeability was computed from the identity TP: ""n F. The results of the analysis indicated that the ratio P,/P, of the sediments in the vicinity of the test well ranges from 15:1 to 25:1 and averages about 20:1. Variations in the permeability ratio are probably due to discontinuous beds of low permeability erratically distributed through the aquifer. and N O4 03 91 3 's' P i 5 4 5 w *C 0 O0#@0 0 o O Oo /C O Pt-279 1 O2 O3 O4 8 A Al Land AA surface N _4 $ .s {s . o T -- '\Water 20 lu table z O 0 & 40 in: Glacial cutwash d 3 60 58 M W Z i-Screen so *% 100 Crystalline rock 0 200 400 FEET L. A c_ coal. 1 Figur® 2.-Sketch showing locations of observation wells for aquifer test on well Pt-279. WEEKS D197 2 7, IN SQUARE FEET PER DAY 103 2 $ . .¢. 6.6. 5s. i104 2 § 4 56 !s 16° 2 s: 4 5-6 . & 108 t aT --r -T i m - mr IIT II_ LTI IX "1 EXL 3 T 10.0 (98 spin ri oan" 3-1 a tir Hg C I ( # om r | wa 6\\ ”7:6_25, z) is a 5 '\1:\\\\ #I =a; i l ‘1 § [rs _ | |__ =4 Ss * I & * s t Tax., ~ No | | a L R *> o - *)s :/ Bs g "45s w Si o | 1 i ~ig ¥ w, Tal. 5 235A } | £ T -- a S - 2 > i il wig/[18 | o wat 12g e L | a] z - ~ I g A\ 38 \%\ | 3 d'la Q | % 3 \Q\A Sx | 8 Flip ~G. x al ~ "Fry 4 | s C s§ "e Ge 3 | <|-s x" ' 6 fy _]} aft § i 5.0 5 & oder or per rm nle mice ane aise fon man - -S- _ SL ___.__-._-- I 6 |- Match point ~ | Ss a x P ®T\ \_\ - 9. *: 'get: "u | a "47g | 0 \\A a C9 0.5 |- [3 s =0.9 | @ | 0 X A A1| -] 0.5 y L sex 104 I I > i> | -| 04 0.4 |- Data plot ss ae L al ba | Lox gl ol | pitas 1~.-i~ "igs 0.3 |- - Type-curve plot pz 1 [ss fat o 1 $f "1 | JS 3: - i0 * 2 2 "a' 5 6 -s io" 2 § [1 5 '6 "s 10~' 2 s [ 4 -$ %. .s 197° U Figur® 3.-Graph showing the match of data from observation wells 18, 28, 38, and 48 to the type curves computed from equation 6. The type-curve solution should be useful for de- termining ratios of horizontal to vertical permeability for many tests on partially penetrating wells. The method could be used with almost any variety of pie- zometer spacings and penetration depths if at least one of the piezometers is somewhat nearer than p=1.om (giyé to the pumped well. Vertical flow components due to partial penetration of the pumped well are negligible beyond that distance. This method also would be useful for obtaining values for the aquifer coefficients 7 and 8 trom tests on partially penetrating wells. The nonequilibrium equation developed by Theis (1935), which frequently is used to analyze data from partially penetrating wells, is strictly applicable only to fully penetrating wells. A comparison of values obtained by analysis of the data from the test on well Pt-279 by the two methods indicates that values for 7 check fairly closely. The nonequilibrium formula gave values of T ranging from 125,000 to 130,000 gallons per day per foot for piezometers near the pumped well to 140,000 gpd per foot for the more distant piezometers. These values are consistent with the value of 140,000 gpd per foot determined by the method described above. However, values of S determined by the nonequi- librium formula were completely unreliable, ranging from 0.2 to 2.56, whereas those determined by equa- tion 6 range from 0.12 to 0.16 and are well within the range that might be expected for the glacial outwash. As the permeability of most stratified sediments is anisotropic, the modification made in this report of the equation for drawdowns near a partially penetrat- ing well also should be more useful than the original equation for analyzing aquifer tests in stratified sedi- ments. In the case of the test on well Pt-279, the use of the original equation developed by Hantush gave values for 7 and 8 about equal to those deter- mined by the nonequilibrium formula developed by Theis. REFERENCES Boulton, N. S., 1954, The drawdown of the water table under nonsteady conditions near a pumped well in an unconfined formation: London, Inst. Civil Engineers Proc., pt. III, p. 564-579. Ferris, J. G., Knowles, D. B., Brown, R. H., and Stallman, R. W., 1962, Theory of aquifer tests: U.S. Geol. Survey Water-Supply Paper 1536-E. D198 Hantush, M. S., 1961a, Drawdowns around a partially pene- trating well: Am. Soc. Civil Engineers Proc., v. 87, no. HY4, p. 83-98. 1961b, Aquifer tests on partially penetrating wells: Am. Soc. Civil Engineers Proc., v. 87, no. HY5, p. 171-195. Muskat, Morris, 1937, The flow of homogeneous fluids through porous media: New York, McGraw-Hill Book Co. THEORETICAL HYDROLOGY Stallman, R. W., 1963, Electric analog of three-dimensional flow to wells and its application to unconfined aquifers: U.S. Geol. Survey Water-Supply Paper 1536-H. Theis, C. V., 1935, The relation between the lowering of the piezometric surface and the rate and duration of discharge of a well using ground-water storage: Am. Geophys. Union Trans., 16th Ann. Mtg., pt. 2, p. 519-524. GEOLOGICAL SURVEY RESEARCH 1964 TWO-VARIABLE LINEAR CORRELATION ANALYSES OF WATER-LEVEL FLUCTUATIONS IN ARTESIAN WELLS IN FLORIDA By HENRY G. HEALY, Tallahassee, Fla. Abstract.-The statistical method of linear regression and correlation analysis is applied to the problem of estimating ground-water stages in one or more wells from the stages in another well. The method provides acteptable results in wells as far as 17.2 miles apart and may be used to evaluate indi- vidual water-level measurements, to estimate water-level post- tions during periods of missing record, and to identify wells in which the water-level fluctuations are representative of areal trends. This paper describes the application and results of the statistical method of linear regression and cor- relation analysis to the problems of (1) estimating the ground-water stage in one artesian well from the ground-water stage in another artesian well and (2) determining the accuracy of individual estimates. The method is applied to water-level fluctuations in two artesian wells in the Floridan aquifer in Madison County in northern Florida and to 15 artesian wells in the Floridan aquifer in the heavy pumped Jackson- ville area, about 100 miles to the east. The Floridan aquifer, which consists of porous lime- stone formations having an aggregate thickness of several hundred feet, is the most widely tapped arte- sian aquifer in the State. The top of this aquifer is at or near the land surface in the central and northwest- ern part of the Florida peninsula and dips to more than 1,000 feet below the surface in the extreme south- ern part. In Madison County, where the Floridan aquifer is overlain by 30 to 100 feet of clay and clayey sand that is perforated by many sand-filled sinkholes, the water level in wells fluctuates primarily in re- sponse to seasonal and long-term trends in precipita- tion. In the Jacksonville area, where the aquifer is overlain by 450 to 500 feet of clay, marl, and clayey sand, the water level in wells responds primarily to seasonal changes in withdrawal rates. In both areas, earth tides and changes in barometric pressure cause minor water-level fluctuations. One of the wells in Madison County, well Madison 18, was equipped with a water-level recording gage, and each time the chart on the gage was changed the water level in the other well, well Madison 17, was measured also. Water-level measurements made on the same date in both wells were used in constructing the hydrographs on figure 1. Shown in the same figure is a plot of the water-level measurement in well Madison 17 against the same-date measurements in well Madison 18; the line of "best fit" through the plot of paired measurements was determined mathe- matically by the method of least squares. A diagram- matic geologic log of both wells also is shown on figure 1. The relation between fluctuations of artesian ground- water levels in wells Madison 17 and 18 may be ex- pressed mathematically by the two-variable linear regression * equation Y,=a-+bX, in which Y, is the estimated water level in well Madison 17 and X is the measured water level in Madison 18. The constants a and b are determined mathematically by the method of least squares. Although the data were not tested statistically for linearity, it is doubtful that a curvi- linear regression line could be fitted that would pro- duce a smaller sum of squares over most of the range of values. There is, however, some indication of in- crease in slope in the region of 17 to 20 feet on the abscissa, but only 6 points are involved. The number of paired measurements that fell within one standard error of estimate (+48,.,) was 87.0 per- 1 The term "regression" refers to the tendency to revert to a com- mon type or average as originally used by Dalton in studying biologi- cal regression. Because correlation analysis is applied to many types of problems, the term "estimating equation" is more appropriate. U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D199-D202 D199 D200 16 T T T T T T T T & 20 |- 7 () w & o & ml- & Z g Well Madison 18 5 i - o < 28 4 os o ate x3 0 32 E a $ m Well Madison 17 o 36 |- | | | | | | | | | 1953 | 1954 | 1955 | 1956 | 1957 | 1958 | 1950 | 1960 | 1961 | 1962 - 38 - d i us § i Q 36+ ~ 9 o=: Clayey ZU-E gal sand £ s & C 23 32) - o x & 30}- No record r; f - available Limestone S A 3 281 (Floridan z 4 26 Limestone aquifer) 8 6 24 |- (Floridan ® g aquifer) F 2 f 22F /_ 300 a. -/. - , 0; s m 20 Well Madison 18 Well Madison 17 o 18r, g Depth 322 ft; Depth 320 ft; 16 rim -L l36 cased 307 ft cased 300 ft 16° ' 20. 24 -25 - 32 DEPTH TO WATER IN WELL MADISON 18, x, IN FEET BELOW LAND SURFACE Figur 1.-Hydrographs of measured water levels, graph of paired water-level measurements, and diagrammatic logs of wells Madison 17 and 18. cent of the total number of measurements for the sample size N =69. Two groups of samples of water-level measurements were analyzed. One, sample size N=69, consisted of the water-level measurements made during the 9-year period March 1953 through December 1961. This period of record includes the maximum known range of fluctuations, which was 21.58 feet in well Madison 17 and 18.44 feet in well Madison 18. The observed extreme and estimated values of water levels in well Madison 17 indicated that the maximum deviations from the regression occurred during periods of high stage for the group having sample size N=69. This difference between observed and estimated water levels during times of high stage may be attributed to dif- ferences in the rate of recharge through the sinkholes in the vicinities of these two wells during times of heavy rainfall. The second group analyzed, sample size N=10, in- cluded water-level measurements made from October 1960 through December 1961 in the same two wells. The results of the analyses of sample sizes 69 and 10 and the estimating equations for computing water level (Y,) in well Madison 17 from observed water levels (X) in well Madison 18 are shown in table 1. THEORETICAL HYDROLOGY TaBu® 1.-Statistical data for wells Madison 17 and 18 [Standard error of estimate (Sy.z) and correlation coefficient (r) are adjusted for the tniverse} Extimating equation for com- Sample size N Sv.. (feet) r puting water-level records for well Madison 17 ! B0... 0. 88 0. 986 | Y,=1.542+1.068X 10 :.. . 21 . 994 | Y,=7.981+0.858X ' Y,=Computed water level in well Madison 17, in feet. X=Observed water level in well Madison 18, in feet. The estimating equations computed from the two sample sizes (V=69, V=10) were used in constructing estimated hydrographs for well Madison 17 (fig. 2). Although both estimated hydrographs correspond rather closely to the actual hydrograph, the one con- structed by use of the equation computed from sample size N=69 matches significantly better at times of high stage. It is concluded, therefore, that the validity of an estimating equation increases with greater range of values in the sample from which the equation is computed. This conclusion is supported by the data in table 2. I I T T I T Estimated water levels computed from Y, =1.542+1.068 X (N=69) 18 |- 20 |- 221- 24 |- Estimated 4 26 |- 28 |- Measured 7 30 |- 32 | 34 |- 36 |- 38} 40 |- | A | | 1953 | 1954 | 1955 | 1956 | DEPTH TO WATER, IN FEET BELOW LAND SURFACE | | | | | 1957 | 1958 | 1959 | 1960 | 1961 | 1962 I I T I I T T T T Estimated water levels a 20|- computed from Y,, =7.981 +0.858 x Estimated 22- (N=10) a 24t- i Measured 26)- 28|- 30|- 32|- 34|- DEPTH TO WATER, IN FEET BELOW LAND SURFACE 36 [- 38 |- | | | | 1953 | 1954 | 1955s | 1956 | 1957 | 1958 | 1959 i 1960 | 1961 111962 | | | FiaurrE 2.-Hydrographs of measured and estimated water levels in well Madison 17. HEALY TaBur 2.-Comparison of measured and estimated highest, lowest, and average water levels in well Madison 17 Water level (feet) Period of record and sample size Highest Lowest Average March 1953 through December 1961: Determined by actual measure- ment (Y)-..................s 17.22 38. 80 30. 94 Estimated by equation com- puted from sample size N=69 M p) Perce ci clerk eos 19. 95 39. 65 31. 24 Deviation (Y- ¥Fiw)........... -2. 78 -. 85 -. 80 Estimated by equation com- puted from sample size N=10 (Y 210) « rere lie =- ~s me 22. 76 38. 58 31. 84 Deviation (Y- -5, 54 +,. 22 -. 90 October11960 through December 1961: Determined by actual measure- ment (Y).._..:.. l_... ~.] 27.74 34. 70 31. 05 Estimated by equation com- puted from sample size N=10 C AOL:: cs - ananassae 28. 26 34. 11 30. 86 Deviation (Y- Y aug) -. 52 +. 59 +. 19 D201 The method of analysis was tested by applying it to 15 artesian wells in the Jacksonville area. Observation wells were arranged into three groups on the basis of the similarity of their patterns of fluctuations of water levels in individual wells. Water- level measurements for one well (the control well) in each group were paired with the same-date measure- ments for each of the other wells in the same group. Estimating equations were then computed from paired water-level measurements made over a 5-year period in each pair of wells except control well Duval 122 and well Nassau 51. The estimating equation for well Nassau 51 was determined from 21 years of paired water-level measurements in wells Duval 122 and Nassau 51. The results of the application of the method are summarized in table 3. The estimated water levels (¥,), together with the measured water levels (¥) in the same well are listed. The maximum difference TaBu® 3.-Comparison of measured and estimated water levels on July 11, 1961, in 15 wells in and near Jacksonville, Fla. [Standard error of estimate (Sy.z) and correlation coefficient (7) are adjusted for the universe] Water level (feet above land Distance from Estimating equation surface) Well control well Sy .t (feet) r (¥r=a+bX) Y- Y. (feet) (miles) Measured Y | Estimated Y. Control well Duval 115 [Measured water level (X)=20.3 ft.] nol. oul 4. 3 1. 50 0. 881 -2.461+ 1.185 X 22. 9 21. 6 +1. 8 0 . 3. 8 1. 14 . 931 3.3984 1.236 X 30. 1 28. 5 +1. 6 cc cl . 4 . 76 . 960 4.293 + 1.100 X 26. 6 26. 6 0 Control well Duval 122 [Measured water level (X)=29.3 ft.] 4. 8 0. 74 0. 907 | -14.639+1.215X 21. 0 20. 9 +1. 0 5. 5 . 54 . 874 | -13.722+ .T80X 8. 8 9. 1 -. 8 cs.. 2. 9 . 66 . 892 | -18.861+1.076X 18. 1 12, 7 +. 4 Duval 1541; .... ans 8. 8 1. 08 . 806 | -16.634+1.126X 16. 4 16. 4 0 17:2 . 81 . 985 742+ .929 X 28. 2 27.9 +. 8 Control well Duval 262 [Measured water level (X)=26.8 ft.] 11. 3 0. 97 0. 854 | -12.944+1.167X 19. 2 18. 3 +0. 9 4. 1 . 84 . 867 7.058 +-1.076 X 36. 0 35. 9 +. 1 Duvald52..............l. s 3. 0 1.13 . 763 -1.010+ .895X 22. 9 22. 9 0 10. 5 . 83 . 840 4.709 + .961X 30. 5 30. 5 0 16. 3 i B7 -. 848 31.659 + .667X 1 14. 4 113. 8 +. 6 2 19. 0 . 25 . 983 960+ .9I84X 27. 5 27. 5 0 2 39. 0 "D7. . 956 3.3631 .869X 26. 7 26. 7 0 1 Feet below land surface. 2 Feet. D202 (¥-¥.) between an estimated and corresponding measured water level was 1.6 feet, and the average difference was between 0.4 and 0.5 feet. The distances between the 3 control wells and the wells for which the water level was estimated range from 19 feet to 17.2 miles. The method of analysis has practical application in evaluating trends and fluctuations of artesian water levels. In addition to the evaluation of control wells in areas where observation wells are numerous, the method of analysis has the following uses: (1) Recognition of those measurements that may be considered to be inaccurate either because of instru- mental or observational error. In general, such errors may be identified by comparison of the deviation be- THEORETICAL HYDROLOGY tween the observed water level (¥) and the computed water level (¥,) with the standard error of estimate for the particular well. (2) Estimation, with a known degree of accuracy, of missing record. If an individual measurement or series of measurements are to be estimated, the stand- ard error of estimate for the particular pair of wells would determine the range of the estimated levels. (3) Identification of changes in the pattern of fluctuations caused by physical factors affecting either, or both, the geologic or hydrologic environment. Fac- tors such as change in pumping rate in a nearby well or in a well which has become plugged would result in a departure from the established relation between observed and estimated water levels. GEOLOGICAL SURVEY RESEARCH 1964 A PERISCOPE FOR THE STUDY OF BOREHOLE WALLS, AND ITS USE IN GROUND-WATER STUDIES IN NIAGARA COUNTY, NEW YORK By FRANK W. TRAINER and JAMES E. EDDY, Washington, D.C. Abstract.-A periscope made of aluminum tubing with a mirror and light at one end and a telescope at the other was used to study fractures in dolomite in shallow drill holes in western New York. Correlation of fractures observed with the periscope with inflections in temperature profiles in a well where downward flow occurs during periods of no pumping confirmed that the inflections coincide with water-bearing frac- tures in the rock. The periscope has also been used for ex- amining well casings, well screens, and pump columns, and, in some places, for determining the texture and composition of the wallrock. Study of the subsurface geology of rocks penetrated by wells has in the past generally been limited to indirect methods, such as geophysical logging and examination of well cuttings. Exceptions to this are the lowering of a geologist down a large-diameter drill hole for firsthand inspection of the zone above the water table, or the observing of wallrock with expensive and generally heavy photographic or tele- vision cameras lowered into a drill hole. This paper describes a lightweight portable peri- scope assembly that has proved very useful in exam- ing the casing and wallrock in wells up to 42 feet deep and which should be useful in examining crevices and shafts as well. The periscope was tested in con- junction with a field study of movement of ground water through fractures in the Lockport Dolomite in Niagara County, N.Y. Use of the periscope confirmed the presence of open-fracture conduits suggested by temperature logs in uncased wells. Most of the observations made with the periscope, and all those described in this paper, pertain to frac- tures in the rock. However, other tests have shown that the periscope is well suited for the examination of well casings, well screens, and pump columns, and, in some places, for the determination of the texture and composition of wallrock. In general, a feature expressed by a difference in color or by sufficient re- lief to cast a shadow can be seen. For example, fila- mentous deposits of iron on pump columns, and white spots on the wall which probably represent masses of gypsum in the dolomite, were seen clearly because of their color. PERISCOPE The periscope column consists of aluminum tubing, in 5-foot segments with threaded ends, with a maxi- mum outside diameter of 2 inches (fig. 1). At the lower end of the column a threaded clear plastic hous- ing contains a mirror set 45° to the vertical, and two lamp bulbs. At the upper end, a telescope from a surveying alidade is set in a threaded fitting. This optical system is adequate for the purpose of the in- strument and is much simpler than one in which a series of lenses is spaced along the length of the column. Two 74-volt lantern batteries at the land surface provide current for the lamps, to which they are connected by plastic-covered cable fastened along the outside of the column. A clamp which rests on the top of the well casing supports the instrument in the well. Because the lower end of the column is closed, the periscope is rather buoyant and easy to manipulate when submerged. We have used this periscope as much as 42 feet below the land surface. At that depth the wall of the well was seen clearly, and presumably the optical sys- tem is adequate for work to somewhat greater depths. The chief difficulty in the operation of the periscope is in controlling the position of the lower end of the column with respect to the wall of the well, to give a U.S. GEOL. SURVEY PROF. PAPER 501-D, PAGES D203-D207 742-652 O-64--14 D203 HYDROLOGIC INSTRUMENTATION Figur® 1.-Well periscope. Mirror-lamp unit (bottom), plastic mirror housing (center), and telescope (top). Scale is in tenths of feet. clear and brightly lighted image. We plan to con- struct a larger mirror unit, which will permit study of a larger field, and to add a tripod, which should steady the instrument sufficiently to permit taking photographs of the walls of wells. GROUND WATER IN THE LOCKPORT DOLOMITE NEAR SANBORN, NEW YORK Occurrence The Lockport Dolomite at Sanborn, Niagara County, is about 120 feet thick and dips gently (less than 1°) south. The occurrence of ground water is believed to be similar to that in the Niagara Falls area, about 10 miles to the west. There, Johnston (1962, 1964) found that openings in the Lockport Dolomite consist of bedding joints, vertical joints, and irregular cavities left by the solution of gypsum, all of which occur in the upper 10 to 15 feet of the rock. The ground water in them is either confined or unconfined, depending on local conditions. The remainder of the formation contains permeable zones of bedding joints, separated by relatively impermeable rock; each permeable zone acts as a confined aquifer. During an earlier study of ground-water conditions at Sanborn, water was found running down the walls of several wells, above the static water level but below the casing; in a few wells water spurted from what evidently were fractures in the rock. During the present study, water was seen running into one of the wells studied with the periscope. Part of it was trickling from a single fracture, and part was inferred to come from several closely spaced fractures because the quantity of water flowing down the wall increased with depth over a distance of about 4 feet. TRAINER AND EDDY Distribution of fractures Counts made with the periscope in 5 wells in the Sanborn area suggest that fractures are more abun- dant in the upper 25 feet of the dolomite than at greater depth. On the average, about 1 fracture per foot in the upper 15 feet was observed, but less than half as many were found between 25 .and 35 feet. Most of the fractures were horizontal or nearly so, but a few were vertical or appeared to curve, and therefore to dip at intermediate angles. One fracture about an inch wide was found, but the widths of the other openings could not be estimated accurately; probably most of the fractures were less than an eighth of an inch wide except where a chip of rock had broken out during the drilling. Some openings had rounded edges which may have been produced by solution. The apparent length of the fractures ranged from 1 inch to several inches, as represented by the parts of the fractures wide enough to cast shadows. Considerable differences in the abundance of these fractures in wells successively farther downdip are thought to reflect local structural differences. Addi- tional data are needed to define better the depth-fre- quency relations of fractures in the Lockport Dolomite. Temperature logs as indicators of water-bearing fractures Temperature profiles of a well in the Sanborn area were measured in the spring and fall, and theoretical profiles were computed for the same days. A log of the fractures in the well was also made, by means of the periscope. (See fig. 2). The measured profiles reflect undisturbed conditions because the well had not been pumped for periods of 1 month to several months before the temperature sur- veys. The theoretical profiles for the same days were computed according to a method given by Ingersoll and others (1948, p. 47, equation q), and are based on the assumption that the transfer of heat through the rocks is entirely by conduction. However, where water is moving through the rocks, as it is known to do in the Sanborn area, the water warms or cools a given part of the rock at a rate greater than would occur by conduction alone, and measured profiles deviate from computed profiles. The form of measured profiles in the Sanborn area departs markedly from that of the theoretical curves, with localization of the departures above certain levels in the wells. On figure 2, for example, note the inflec- tion at 32 to 33 feet in the April profile. Other con- spicuous departures are associated with the inflections at 23 to 24 feet in the April profile and 28 to 29 feet in the November profile. _- EXPLANATION / ___ Theoretical profile a April 3, 1963 7 casing -- -- Nov. 14, 1963 7 ' E. _ __| Measured profile Fracture 10 [- _ a--e&--e April 3, 1963 |---| Probable fracture |- ' Nov. 14,1963 == T T T 6 156 3 3 Lu Lu z L. _._| 5 g 20} al - LL CC > / w o - & csf | # - ad ~ & | [ef M i 3 i - x 30 | m E L bo maces 2 | 3s | 4 & 40|-' I 7 ~" 45 1 T I I1 1 1 1 1 1 T 45 50 55 _ grapHIc TEMPERATURE, IN DEGREES FAHRENKHEIT FRASJTéJRE FraurE 2.-Water-temperature profiles, and fracture log based on periscope observations. Comparison of the measured temperature profiles and the log of fractures shows that each conspicuous temperature inflection is at the level of a fracture or group of fractures. The inflections evidently indicate the levels at which water flows out from the well bore into fractures. According to this interpretation the inflection at 32 to 33 feet in the April profile reflects the flow of relatively cold water down the well, during the winter and spring, and out into the fracture at about 32 feet. The wall of the well above 32 feet lost heat to the downward-flowing water much more rap- idly than it could have done by conduction of heat through the rock. On the other hand, the sharp in- flection in the November profile is believed to reflect the flow of relatively warm water down the well and out into fractures at about 29 feet. Temperature pro- files for deeper wells near Sanborn show that the temperature of ground water below the zone of sea- sonal fluctuation is 50° to 51°F. Because temperatures below the level of the deepest inflections in the ob- D206 served profiles are about 50° to 51°F, and because the lower parts of the observed and computed profiles are of similar form, heat transfer below the inflections is believed to be largely by conduction. The positions of the inflections on the two measured profiles are different because the head associated with each fracture or group of fractures changes with the seasons. (These changes are particularly significant where shallow fractures are completely drained in late summer.) As a result of these changes in relation of head among the fracture zones, the chief outward flow occurs at different levels at different times of the year. It appears that with downward flow such as occurs under nonpumping conditions in many wells in the HYDROLOGIC INSTRUMENTATION Sanborn area, temperature profiles may be used to locate water-bearing fractures in wells where the peri- scope cannot be used. REFERENCES Ingersoll, L. R., Zobel, O. J., and Ingersoll, A. C., 1948, Heat conduction with engineering and geological applications: New York, McGraw-Hill Book Co., Inc., 278 p. Johnston, R. H., 1962, Water-bearing characteristics of the Lockport Dolomite near Niagara Falls, New York: Art. 110 in U.S. Geol. Survey Prof. Paper 450-C, p. C123-C125. 1964, Ground water in the Niagara Falls area, New York, with emphasis on the water-bearing characteristics of the bedrock: New York Water Res. Comm. Bull. [In press] SUBJECT INDEX [For major headings such as "Economic geology," "Geophysics," "Structural geology," see under State names or refer to table of contents] A Aeromagnetic anomalies, relation to copper deposits, Arizongal...-............ Air-bubbling, in lakes, use in improving water Ge eva Alaska, ground water, Bethel area...... paleontology, northern part..........._... Anisotropy, aquifers, field determination Antarctica, petrology, Eights Coast area...... Aquifers, artesian, thermal water..____.______. determination of permeability and anisot- TOBY Icl cellules 3 Argentina, ground water, coastal area... Arizona, copper, Globe-Miami area......_.... geophysics, Globe-Miami area_~~....._... Arkansas, ground water, south-central part... Artesian aquifers, thermal water, Argentina. . Artesian wells, analysis of water-level fluctua- MORELZL :- - Pene rhens e Ashland Mica Schist, Georgia, ground water.. Barrandeina? aroostookensis, Devonian, Maine. Basins, closed, carbonate content of water. ... Biotite, radiometric age, Antarctica_........_~ Black Hills, South Dakota, structural geology.. Boreholes, periscope for examination of...... Bottom sediments, radioactivity and density, new measuring device. ......_.... Boulder batholith, Montana, petrology....... Brine, carbonate content, determination * Bull Lake Glaciation, Wyoming.... hue Burroughs Mountain Stade, Washington, nec uue C Calamophyton forbesii, Devonian, Maine...... California, phosphate, Statewide survey quality of water, southern part....__..._._ Cambrian, Maine, geochemistry.......__..... Carbonate, in brine, problems of analysis...... Carrizo Sand, Arkansas, ground water........ Cartography, new use of orthophotography . .. Chinle Formation, Colorado-Utah, stratig- Clay, montmorillonitic, Washington...._.... Clay mineralogy, wallrock alteration . ...__._. Closed basins, carbonate content of water. . .. Coal, Colorado-New Mexico, Btu values...... Colorado, coal, southwestern part. ..____._.._. oil shale, western part..___._..___________ stratigraphy, northwestern part . ___._.... Copper deposits, aeromagnetic interpretation, L. .es cee ne nes Cretaceous, California, phosphate......._.... Colorado-New Mexico, coal....__. South Dakota, structural geology....__... Wyoming, structural geology............. Page D70 190 144 40 193 50 153 193 153 70 70 158 153 199 141 43 134 50 28 203 65 134 104 110 D Density, of bottom sediments, measuring , 10. Devonian, Maine, paleobotany.......__._.__. Discharge, river, relation to geology . .._...... river, relation to springflow and evapo- Dissolved solids, in surface water, relation to occ carne enas Dithizone, use in determination of mercury in cn. Eocene, Arkansas, ground water..._________-- Utah-Colorado, oil shale....._._.......... Epigenetic deposits, uranium, in sandstone. .. Evaporation, in lakes, method of reducing... Evapotranspiration, effect on streams. .. . ._.. F Fall River Formation, South Dakota, struc- tural Floods, Louisiana-Mississippi area.........__. Florida, ground water, northern part. ....._.. Fractures, study with borehole periscope...... Fruitland Formation, Colorado-New Mexico, COAL .. ach enemee G Garda Stade, Washington, definition........ Gartra Member, Chinle Formation, Colorado- Utah, stratigraphy. ...... Geochemical anomalies, lead-zine, Maine. Georgia, ground water, Dawson County...... Glaciers, post-hypsithermal, Washington.... Glen Canyon Sandstone, Colorado-Utah, @trstigraphy...-......._...__._ll..s Globe-Miami copper district, Arizona, aero- magnelicstudy......_............ Green River Formation, Utah-Colorado, oil Rell. 22 LACE ILC. Gros Ventre Mountains, Wyoming, structural geology -.. 2.2.0.2 ALL Neuss H Hawaii, geomorphology, offshore.. .._....._.- volcanism, island of Hawaiian Ridge, submarine landslides.. ..... Hydraulics, ground-water, determination of permeability and aquifer anisot- TODY :S S Instrumentation, for mercury determination .. Ton-exchange separation, of tin from silicate TOOK. Page D65 43 177 171 115 128 28 182 199 203 110 30 61 141 110 30 70 95 95 193 123 131 J Jurassic, Colorado-Utah, stratigraphy. . ...... Kilauea Volcano, Hawaii, temperature SHIGION: . . Korea, ground water, reconnaissance study... L Lakes, improvement of water quality .......~- Lakota Formation, South Dakota, structural Jo. Landslides, submarine, Hawaii Lava lake, temperature studies, Hawaii. ...-- Lead, geochemical anomaly, Maine..........- Lead-zine deposits, wallrock alteration ...... Louisiana, surface water, southeastern part. .. M Maine, lead-zine anomalies, west-central part. paleobotany, northern part..............- Mapleton Sandstone, Maine, paleobotany .... Mapmaking, new use of orthophotography. .. Massachusetts, sedimentation, Cape Cod.... Mercury determination, in rocks, new method . in vegetation, new method....._.....__.-- Mesozoic, Korea, ground water.............-- United States, uranium..............---- See also Triassic, Jurassic, Cretaceous. Miocene, Argentina, ground water.....__...-. Mississippi, surface water, southwestern part. Mississippi embayment, Arkansas, ground LL CAREP IAL LAAs Montana, petrology, western part ._._.._-... Montmorillonite, in glacial deposits, Wash- INBLON.L-. ci o cee Mount Rainier, Washington, glacial geology.. N Nevada, paleontology, southern part . ...___.. petrology, southern part._..__._.....-...- surface water, southeastern part . Nevada Test Site, geologic studies..._...-..-- New Mexico, coal, northwestern part........ New York, ground water, Niagara County... North Dakota, ground water, southeastern PAIL. 1.0. LOL Avis no bence surface water, southeastern 0 Oceanography, radioactivity and density of bottom sediments, new measuring OVICO LSL cc submarine landslides, Hawai Oil shale, Green River Formation, Utah- Colorado. uous D207 Page D30 61 43 138 118 128 149 76 153 182 158 99 110 161 177 65 95 86 D208 Ordovician, Maine, lead-zinc anomalies.... ... Wisconsin, zinc and lead___.___..______.. Oregon, surface water, temperature studies... Orthophotography, use in ... Ostracodes, Triassic, Alaska and Nevada..... P Paleozoic, Korea, ground water...._...___.... United States, uranium ._. See also Cambrian, Ordovician, Devonian, Pennsylvanian. Pennsylvanian, Wyoming, ground-water hy- faulios 212020. . at Leur et Periscope, borehole, for fracture study..._.__. Permafrost, effect on temperature of ground MHOC Ude aba uds Permeability, relation to porosity, Tensleep vertical, field determination . . Phosphate rock, occurrence, California. Pleistocene, Korea, ground water... North Dakota, ground water...._..__.__. North Dakota, surface water ..._________ Washington, engineering geology . e Wyoming, glacial geology... Pliocene, Nevada, petrology.....________..__. Precambrian, Georgia, ground water...... Q Quaternary, Washington, glacial geology . ___. See also Pleistocene. Radioactivity, of bottom sediments, meas- uring. Radiometric age determination, Antarctica... Reservoirs, effect on stream temperature.... water quality, effect of air-bubbling...__. Runoff, effect on quantity of dissolved solids in surface water...... storm, Louisiana-Mississippi...._...____. Page Dél 54 185 138 40 149 76 166 203 144 166 193 79 149 161 177 104 14 141 110 65 50 185 190 115 182 SUBJECT INDEX S Page Sand, beach and colian, size studies... yaz) DHS Sheyenne River, North Dakota, relation of discharge to geology. ......_....... 177 Size studies, beach and colian sand........... 118 South Dakota, structural geology, Black Hills. _ 28 Spectrophotometry, use in determination of mercury in vegetation............ 128 Spiritwood aquifer, North Dakota_......._... 161 Springflow, determination from streamflow... 171 Statistical studies, sand-grain size.... 118 water-level fluctuations...........__..._._ 199 Stream orientation, effect on water tempera- MIFGL on i ne nar nial 185 Streamflow, relation to geology.... tere al relation to springflow and evapotranspira- ROHL . L Eure cable H4 Se eb 171 temperature, effect of reservoirs.__..___.. 185 Submarine landslides, offshore Hawaii.... .... 95 T Temperature, effect on streamflow-springflow (tor 171 Temperature studies, ground water, Argen- MHS. L CT rect aut canis 153 Kilauea Volcano, Hawaii 1 surface water, Oregon.._..._.. 185 Tensleep Sandstone, Wyoming, hydrology.... 166 Tertiary, California, phosphate. 79 Montana, petrology. 8 United States, uranium....._.........._. 76 Wyoming, structural geology............. 22 See also Eocene, Miocene, Pliocene. Thermal ground water, Argentina............ 153 Thermal stratification, in lakes, elimination.. - 190 Till, glacial, newly named unit..............- 104 Timber Mountain caldera, Nevada, petrology . 14 Tin, separation from silicate rocks............ 131 Triassic, Alaska, paleontology... a 40 Colorado-Utah, stratigraphy . s 30 Nevada, paleontology.................... 40 Page Titration, problems in carbonate analysis of DrIMG. Io neu rab be ree panes D134 U Uinta Basin, Utah-Colorado, oil shale........ 86 Upper Mississippi Valley zinc-lead district, enrichment in wallrock alteration.. 54 Uranium deposits, in sandstone, distribution.. 76 Utah, oll shale, Uinta Basin....__.__._..._._. 86 stratigraphy, northeastern part.....__... 30 V Vegetation, determination of mercury in...... 128 Volcanism, Nevada, southern __.. 14 Volcanoes, Hawaii, temperature studies.... .. 1 W Wallrock alteration, zinc-lead deposits........ 54 Washakie Point Till, Pleistocene, definition. 104 Washington, engineering geology, Seattle...... 99 glacial geology, Mt. Rainier....__.______._. 110 Sealtle .. . :: oo oo crenate abends 99 Water-level fluctuations, statistical study.... 199 Wind River Mountains, Wyoming, glacial BOOIOGYL ALL L.. 104 Wisconsin, ground water, central part._______ _ 193 zinc-lead, southwestern part...___._...... 54 Wyoming, glacial geology, Wind River MOUNEMINEL LIU. - 104 hydrology, Bighorn Basin-..._.______.... 166 structural geology, Gros Ventre Moun- o 51+. Weenie ees in' pri 22 ¥ 4 Zinc, geochemical anomaly, Maine........_.. 61 Zinc-lead deposits, wallrock alteration... ._... 54 Zircon, radiometric age, Antarctica.. .._..___. 50 B Page ATIS IET u L. seve erences Di31 Bredehoeft, J. D - 166 CURE /CO.M.......c.cl..c e 65 C CSRNOY ) BFC. 220. .2 /L Ilu. cance db nene burials 61 (Cashion;y AV. L000 L 86 D. 110 D cheese 115 s 149 .% ... . ...le inh 149 AUIAL IE.... cock 50 E 171 203 p AY ALT... olo 2000 once renee Aiiss 144 Pinch AV e. 76 G (GATCIA, .L. el reduce 153 Gott, G. B... so os AAD E21... nlc once eee ccr 79 H cll cl 199 MeL ANE Lene nol. coed e es 54 nds IO IIC La sans 90 MoSMaRpAR LO 20000 e 158 AUTHOR INDEX Page Hosterman, J. .W . .eude linea enne r des D54 Huflman, Claude, Jt. 131 J JOSDOTSON; ANNA. Lc O ee rca nene con 70 Folly, 4. L.... a 54 JORSS, B. $...... sono eo be re cece 134 K NV, H ..-. o LII IITA LET. 22 Kelly, T. R: . .. L cecves 161 Koberg, G. E. 190 Rojithn, CBOTGO. _.. co ce cl reena ece oben 1 L LANGbOM, W. B.. . L.. ceue 115 Liift/B. JA... uc L rebel she be pes 14 M McCarthy; 4: H., JT. nu Ln deel olo nere es 123 McHugh, J. B........ - 128 Madson, B; M.. , .... 79 Milter /B. (D.. ..o. Lcol. de ede ilove a 110 MOOFe, A. M... .. 2. on oun 185 Moore, D. O:... LI III ILI AEV vc ener. deve. ATI Moore, J. G...... shes 1,05 Mullificati®, D. R.. IIL 99 N Nichols, .c n nue ails 99 P TauIlson; Q. F. ..o. 177 PeCKy D, once cbr be car ne no 1 Page Poole PA.. D30 PpoSh, BLV... : AXL s isu in ire dences 61 R H: LJ .. Lean ree dr ne een 134 Richuiond, (4; une 104 5 Splso, UTI.. . .co nn ress one 153 Sauer, V. B.. 182 SChOr, M. B.. 00s ei 138 Beblcss POTN 2220.00. anor EI Oc. 118 Schofly ©. L.. [ELX ITCC ease res 153 SebopLF, M 20.0.2 -e ben be bos 43 SChHupp, .B. (1220010202000. ver- sours 144 Sever, O. WY 12. Gere dnes enepenes ened 141 Sohn, (T. MQ Pree LLL Reker recs ece sews 40 SDHOTOn R. A 2s. en cube 99 SEEM, 'T; W 2 22-20 Fev onan can ous ne s 50 Stewart; J, H). .L LL. 30 T THONLAE, HL: H .. .. .o L LCC uwe. 50 Tilling, R. L.... 8 TTrAINOT: FW AL U. oue oven rece reveunk ees 203 Tromba J.:V; A.; .. 31 AETV ACL 118 U UChHDI BIAIA.. L 22. os lenee 118 V VIERA, W, W .. Gece 123 128 B. P...... SUL. cs 193 D209 U.S. GOVERNMENT PRINTING OFFICE : 1964 - O-742-652