Economic Geology of the Panamint Butte Quadrangle and Modoc District, Inyo County, California By WAYNE E. HALL and HAL G. STEPHENS, Geologists U.S. Geological Survey, Menlo Park, California SPECIAL REPORT 73 CALIFORNIA DIVISION OF MINES AND GEOLOGY Ferry Building, San Francisco, 1963 Prepared cooperatively with the U.S. Geological Survey STATE OF CALIFORNIA EDMUND G. BROWN, Governor THE RESOURCES AGENCY HUGO FISHER, Administrator DEPARTMENT OF CONSERVATION DeWITT NELSON, Director DIVISION OF MINES AND GEOLOGY IAN CAMPBELL, Sfafe Geologist SPECIAL REPORT 73 Price $2.00 Page 5 ABSTRACT 7 INTRODUCTION 7 Purpose and scope 7 Geography 7 Location and accessibility 8 Topography 9 Climate, vegetation, and water supply 9 Previous work and acknowledgments 10 GENERAL GEOLOGY 10 Gneissic sequence 10 Precambrian(?) rocks 10 Cambrian(?) rocks 10 Dolomite sequence 12 Cambrian system 12 Racetrack dolomite 12 Nopah formation 13 Ordovician system 13 Pogonip group 13 Eureka quartzite 13 Ely Springs dolomite 13 Silurian and Devonian systems 13 Hidden Valley dolomite 14 Marble sequence 14 Devonian system 14 Lost Burro formation 15 Mississippian system 15 Tin Mountain limestone 15 Perdido formation 16 Mississippian and Pennsylvanian(?) systems 16 Lee Flat limestone 16 Silty limestone sequence 16 Pennsylvanian and Permian systems 16 Keeler Canyon formation 17 Permian system 17 Owens Valley formation 17 Plutonic rocks of Mesozoic age 17 Biotite-hornblende quartz monzonite 17 Leucocratic quartz monzonite 17 Age 17 Andesite porphyry dikes CONTENTS Page 18 Cenozoic deposits 18 Older alluvium 19 Basalt 19 Rhyolitic tuff 19 Younger alluvial deposits 20 STRUCTURE 22 MINERAL DEPOSITS 22 Types of deposits 23 History and production 24 Lead-silver deposits 24 Distribution 24 Size and character of ore bodies 25 Ore controls 25 Mineralogy 25 Hypogene minerals 26 Supergene minerals 27 Wall-rock alteration 27 Mines and prospects in the Modoc district 27 Defense mine 29 Lead mine (Hughes group) 29 Little Jim prospect 29 Minnietta mine 32 Modoc mine 34 Paul Imlay prospect 34 Red Dog prospect 34 Surprise mine 35 Mines and prospects in the Panamint Range 35 Big Four mine 36 Kerdell prospect (Lone Ear prospect) 36 Lemoigne mine 37 Uranium deposits 37 Golden Nugget prospect 37 Gold deposits 37 Little Mack mine 37 Nonmetallic deposits 38 Limestone 38 Dolomite 38 Clay 38 REFERENCES CITED [3 CONTENTS-Continued ILLUSTRATIONS Page In Plate 1 pocket In Plate 2 pocket In Plate 3 pocket In Plate 4 pocket In Plate 5 pocket In Plate 6 pocket In Plate 7 pocket In Plate 8 pocket In Plate 9 pocket In Plate 10 pocket In Plate 11 pocket In Plate 12 pocket Economic map of the Panamint Butte quadrangle. Geologic map of the Modoc district. Geologic map and cross sections of the intermediate workings of the De- fense mine. Geologic map and cross section of the Defense mine. Geologic map and cross section, Min- nietta mine, Jack Gunn and Cow- shed workings. Geologic map of the Jack Gunn and Cowshed stopes. Geologic map and sections of the Modoc mine. Geologic map of underground work- ings, Surprise mine. Geologic map and cross sections of the Surprise mine. Geologic map and section of the Big Four mine area. Geologic map of the underground workings of the Big Four mine. Geologic map and section of the Le- moigne mine area. Page 8 Figure 1 30 Figure 2 12 Photo 1 14 Photo 2 15 Photo 3 18 19 22 23 31 33 Photo 4. Photo 5. 21 Photo 6. 22 Photo 7. Photo 8. Photo 9. Photo 10. Photo 11. Index map showing the location of the Panamint Butte quadrangle. Composite map of the underground workings of the Minnietta mine. View of the west face of the Panamint Range north of Dolomite Canyon. Aerial view of Lookout Mountain. Stratigraphic section of the Modoc dis- trict. View of concordant lenses of mono- lithologic breccias in Pliocene(?) fanglomerate. View of shattered Eureka quartzite and Ely Springs dolomite in a thrust plate 1.7 miles S. 20° E. of Towne Pass. View of the Lemoigne thrust on the west face of the Panamint Range. View of the west face of the Panamint Range showing the left-lateral dis- placement of the Lee Flat limestone. Nearly horizontal mullions on a north- east-striking fault in the Panamint Range. View of the Modock furnaces on Look- out Mountain. Aerial view of the Minnietta mine area. Aerial view of the Modoc mine area. TABLES Page 11 18 24 27 Table 1. Stratigraphic section of the Panamint Butte quadrangle. Table 1 A. Correlation of lithologic types com- bined in the four economic map units of Cenozoic deposits. Table 2. Production of gold, silver, copper, lead, and zinc from the Panamint Butte quadrangle and Modoc district. Table 3. Production from the Defense mine. Page 29 Table 4. 32 Table 5. 34 Table 6. 35 Table 7. 36 Table 8. Production from the Minnietta mine. Production of the Modoc mine. Production of lead-silver ore from the Surprise mine. Production of lead-silver-zinc ore from the Big Four mine. Production of lead-silver-zinc ore from the Lemoigne mine. ABSTRACT The Panamint Butte quadrangle is in central Inyo County, California, partly within Death Valley National Monument. The area includes the northern parts of the Argus Range, Panamint Valley, and Panamint Range. The northern half of the Modoc district is in the southwestern part of the quadrangle. In order to study the Modoc district as a unit, 10 square miles that includes the south half of the district was mapped in the northwest part of the Maturango Peak quadrangle. The Panamint Butte quadrangle is underlain by a sequence, about 15,000 feet thick, of metamorphic and sedimentary rocks of Precambrian(?) to Permian age that is intruded by quartz monzonite plutons of Jurassic(?) age and andesite porphyry dikes of Cretaceous(?) age. Late Cenozoic volcanic rocks and sedimentary deposits uncon- formably overlie the older rocks. Late Precambrian(?) metamorphic rocks, which include micaceous and limy quartzite, mica schist, biotite-hornblende gneiss, and dolomite, are limited to three small expo- sures in the Panamint Range and Panamint Valley. Paleozoic strata range in age from Middle(?) Cambrian to Permian in a conformable sequence approximately 14,000 feet thick. Silurian and older Paleozoic rocks are exposed only in the Panamint Range; they consist mainly of dolomite but include lesser quartzite, limestone, and shale. Devonian and younger Paleozoic rocks are exposed both in the Panamint and Argus Ranges. They consist predominantly of limestone, marble, and silty limestone. Quartz monzonite plutons of Jurassic(?) age intrude the Precambrian(?) and Paleozoic strata in both the Panamint and Argus Ranges. All mineral deposits with a known production are within 1 Vi miles of one of these intrusions. A swarm of altered andesite porphyry dikes of Cretaceous(?) age striking N. 70° W. intrude the Paleozoic rocks and locally the quartz monzonite in the Argus Range south and southwest of Panaminl Springs. Late Cenozoic deposits cover most of Panamint Valley and the Panamint Range south of State Highway 190. Three periods of deformation are recognized. The earliest orogeny, late Mesozoic, formed broad open folds that trend north to N. 20° W. in the Argus and Panamint Ranges. Thrust faulting accompanied folding in the Panamint Range. The second period of deformation was caused by forcible intrusion of quartz monzonite plutons of Jurassic(?) age, which deformed both the broad folds and the thrust faults. This was followed by a long period of erosion until the late Cenozoic when extensive regional warps and accompanying strike-slip and normal faults formed the present basin and range topography. Total value of the production of lead, silver, zinc, copper, and gold is about $3,900,000. Lead and silver from the Modoc district account for all but $160,000 of this amount. The first production of lead-silver ore came from the Modoc district in 1875, and $1,900,000 in silver, gold, and lead was produced by 1890. This was mostly from the Modoc mine. The Minnietta mine produced approximately $600,000 in silver, gold, and lead since 1895; no significant production was recorded after 1954. Most of the production from the Defense and Surprise mines came after 1947. Ore in the Modoc district is in marble of Devonian and Mississippian age whereas silty limestone of Pennsylvanian and Permian age is unfavorable. The ore bodies are small but high grade. Galena is the principal primary ore mineral; secondary ore in the Modoc district is manganese-rich and contains cerussite, relict galena, coronadite, jasper, cryptomelane, and pyrolusite. 5l The lead-silver mines in the Panamint Range are small and account for only $70,000 of the total production of the Panamint Butte quadrangle. The Lemoigne mine on the east side of the Panamint Range produced some galena and siliceous silver ore between 1925 and 1927. The Big Four mine on the west side of the Panamint Range produced oxidized lead ore associated with hematite and jasper between 1944 and 1952. The host rock at the Lemoigne mine is dolomite of Cambrian(?) age, whereas at the Big Four mine the host rocks are marble and limestone of Pennsylvanian age that are thrust over marble and dolomite of Ordovician age. Gold production from the Panamint Butte quadrangle is small, slightly exceeding 2,500 ounces; most of the gold came from lead-silver ore. Uranium has been found in small pockets in Osborne Canyon in the Argus Range, but no production has been recorded. Nonmetallic commodities in the Panamint Butte quadrangle have not been exploited. They include limestone, dolomite, and limy clay. [6] Economic Geology of the Panamint Butte Quadrangle and Modoc District, Inyo County, California By Wayne E. Hall and Hal G. Stephens INTRODUCTION PURPOSE AND SCOPE This study of the Panamint Butte quadrangle is part of a long range program by the U. S. Geological Survey in cooperation with the California Division of Mines to study the Inyo County lead-silver-zinc deposits. The de- posits lie within a mineralized belt 120 miles long that extends from the Inyo Mountains southeast to the Resting Spring district in the Tecopa quadrangle. The Panamint Butte quadrangle includes the northern half of the Mo- doc district and several small mines in the Panamint Range (fig. 1). In order to study the Modoc district as a unit, 10 square miles in the northwest part of the Maturango Peak quadrangle, which contains the re- mainder of the district, was included in the area to be mapped. The project entailed mapping the Panamint Butte quadrangle on a scale of 1:40,000; mapping the Modoc district on a scale of 1:20,000; and detailed studies of individual deposits. This report presents the economic results of the study. Included are detailed descriptions and large-scale maps of all the lead-silver mines that have a recorded production and a geologic map of the Modoc district. An economic map of the Panamint Butte quad- rangle shows the location of all mines and prospects, their relative importance, and their relation to lithology and to major faults (pi. 1). A detailed geologic quadrangle map and a description of the general geology will be pub- lished in a later report. GEOGRAPHY Location and accessibility , The Panamint Butte quadrangle is in central Inyo County in southeastern California partly within Death Valley National Monument between longitude 11 7° 15' and 117°30'W. and latitude 36°15' and 36°30'N. (fig. 1). The area includes the northern Argus Range, Panamint Valley, and part of the Panamint Range. The only settle- ments within the area are a resort motel, restaurant, and State Highway Department office at Panamint Springs and small mining camps at the Minnietta and Defense mines. Very little evidence exists of the old town of Lookout, which was an active mining town on Lookout Mountain during the 1880's. Access to the quadrangle is provided by two improved roads. State Highway 190, which runs from U. S. High- way 6 in Owens Valley to Death Valley, crosses the central part of the quadrangle and an improved county road provides access from Trona (fig. 1). Trona and Lone Pine, 38 miles south and 46 miles west of the quad- rangle respectively, are the closest supply centers. Ore from the area is trucked south to the railroad at Trona or west to Keeler or Lone Pine. Gravel roads lead to all the producing mines. Some of the roads are steep and are best negotiated with a 4-wheel drive vehicle. Roads to mines that have been closed several years are usually in poor condition. A 4-wheel drive vehicle provides access to some parts of the quadrangle that are miles from any road. Although tedious, it is possible to drive to the foot of Mill Canyon at the head of Panamint Valley in the northwest part of the quadrangle, and without much difficulty to the head of Panamint Valley to sec. 6, T. 17 S., R. 42 E. skirting the east side of the sand dunes (pi. 1). Two canyons in the Panamint Range are accessible. One is Dolomite Can- yon 2 miles north of State Highway 190, which is ac- cessible to an altitude of about 3,800 feet by 4-wheel drive vehicle. The other is Lemoigne Canyon 1] miles north of the Lemoigne mine. A small jeep can be driven with difficulty to an altitude of 4,200 feet, and a trail goes to the top of the range and continues northward to Cot- tonwood Springs in the Marble Canyon quadrangle. The jeep trails are shown on the economic map (pi. 1). [7] California Division of Mines and Geology [Special Report 73 D "*D NEW YORK BUTTE UBEHEBE PEAK QUADRANGLE QUADRANGLE •Z- SPECIAL REPORT 42 J- o N 1 \ ° 1 *r vX o o \v\ a ■p areaI 5-*\ SHOWN Oil.-^'f'. \ tn s>> INDEX MA^, « N z V ^\_— 1 £ *^==^ ' z o -OV J> v CERH GORDO E MARBLE CANYON 30' QUADRANGLE ^Weler keeler ^\ quadrangle OWENS \\ DARWIN QUADRANGLE SPECIAL REPORT 51 &. BUTTE lemoigne/ $ Quadrangle mine v ^ i4/f£" J ^? BIG FOUR^ '#' // MINE Jy ^ It '/ PANAMINT ^ /< LZ SPRINGS _^-^= : =!^ == = =! ^ / z * V ^ i \* y / //»W/////////\'S/////////. (DRY) / ;/ \ ZINC H 15' O X. DARWIN X. MINE MINE O COSO PEAK QUADRANGLE C DISTRICT *■*" iP \-\ A O MATURANGO PEAK ^V/ » QUADRANGLE if f> Q » * 1 r - w z r 1 o rn \\ -< \\ ■00' STOVEPIPE WELLS TRONA 18 Ml E3 MILES Figure 1. Index map showing the location of the Panamint Butte quadrangle. Topogra The quadrangle is in the western part of the Basin and Range province. Panamint Valley, a large enclosed basin trending N. 25° W. diagonally across the quadrangle, oc- cupies about a third of it. The floor of the valley is at an altitude of 1,542 feet. The valley is bounded on the east by the Panamint Range and on the west by the Argus Range (fig. 1). The flanks of both ranges are steep, and the difficulty of access is a deterrent to mining or even prospecting. The maximum relief is 5,745 feet in phy the Panamint Range from peak VABM 7287 westward 4'/ 2 miles to the playa in Panamint Valley, and local relief on this peak is 4,800 feet in 2 % miles. The crests of both ranges are broad mature surfaces. In the Panamint Range northeast of Panamint Butte is an extensive area of sub- dued topography about 5,000 feet in altitude (pi. 1). The altitude increases toward the southeast to a maximum of 7,287 feet. The crest of the Argus Range is a rolling surface 4,000 to 5,800 feet in altitude. 1963] Panamint Butte Quadrangle and Modoc District Drainage is into two enclosed basins. The northeast 17 percent drains eastward into Death Valley. The remain- ing part of the quadrangle drains into Panamint Valley. Panamint Valley itself consists of two basins separated by a divide with an altitude of 1,720 feet. The playa in the northern basin is at an altitude of 1,542 feet; the playa in the southern basin is at 1,021 to 1,043 feet. Only the southeastern corner of the quadrangle drains into the southern basin. Climate, vegetation, and water supply The climate is typically arid— characterized by slight rainfall, large range in temperature, and by frequent strong winds. No weather station is within the area; the nearest station is at Trona, 38 miles south of the quad- rangle. The altitude at Trona is 1,656 feet, about the same as the northern Panamint Valley basin, and the climate is probably slightly cooler. The following data for Trona are from Climatological data for the year 1946, (Anonymous, 1946): Trona (elevation 1,656 feet) Annual mean temperature 66. 6°F Highest temperature 115°F Lowest temperature ___ 20°F Annual rainfall 4.86 inches Snowfall The summer temperatures in or near the floor of Pana- mint Valley are uncomfortably hot, but are generally very pleasant during the other seasons. Above 5,000 or 6,000 feet the summer temperatures are quite pleasant except for short hot spells, but the winter days are com- monly cold and snow may be encountered. Rainfall at all altitudes is scant. The average number of days with precipitation at Trona is 20. Vegetation is sparse on both the Panamint and Argus Ranges. Steep slopes are essentially bare, but scattered sagebrush grows in the valleys and on moderate slopes and creosote bush grows in some gullies. A few scattered junipers and pinvon pines grow above 5,000 feet in the Panamint Range, and a large stand of Joshua trees grows in the basin at an altitude of 5,200 to 5,400 feet on the northeast side of Panamint Butte. The water supply is limited to several springs in the Argus Range. No water is available in the Panamint Range within the Panamint Butte quadrangle, and water must be hauled to the mines by truck. A heavy growth of creosote bush in a few gullies indicates occasional seeps, but no flow of water was seen at any place. Two canyons at the north end of Panamint Valley have springs, but both are outside the quadrangle. Mill Canyon has two springs with a strong flow of water in the Ubehebe Peak quadrangle, and the canyon 2.08 miles east of the northwest corner of the quadrangle has water within the Marble Canyon quadrangle. Cottonwood trees grow in both canyons near the springs. These springs are the watering holes for the burros that are generally pres- ent at the north end of Panamint Valley. Cottonwood Spring in the Panamint Range about 1 mile north of the quadrangle has a strong flow of water that is fenced off from the burros, and is a reliable source of good water. Water is obtained for the motel at Panamint Springs from an ample supply at Darwin Falls 3 miles to the west in the Darwin quadrangle. Two springs supply the water for the Defense and Minnietta mines. Other mines bring their water in by truck. The Defense mine obtains its water supply from Jack Gunn Spring, which normally flows approximately 900 gallons per day, and sometimes from French Madam Spring (see pi. 2). The Minnietta mine has a pipeline to Thompson Spring in Thompson Canyon, but the supply is not large. Snow Canyon 2 miles south of Thompson Canyon also has water. The only other spring in the mapped area is near Panamint Springs and supplies the Highway Department; the flow from this spring is small. PREVIOUS WORK AND ACKNOWLEDGMENTS Very little information was available previously on the geology of the Panamint Butte area, except for several papers dealing with specific mines or small areas within it. Fragmentary sketches of the early mining activity in the Modoc district can be obtained from Ravmond (1877, p. 32), Burchard (1882, p. 39; 1884, p. 164; 1885, p. 104), DeGroot (1890, p. 210), and Crawford (1894, p. 24; 1896, p. 32). Later mining activity is described in California Division of Mines reports on Inyo County by Waring and Huguenin (1919), Tucker and Sampson (1938), and Norman and Stewart (1951). The earliest geologic map that covers the Panamint Butte quadrangle is a reconnaissance map of southern Nevada and southeastern California by Spurr (1903, pi. 1), who makes a threefold subdivision into fine-grained igneous rocks, coarse porphyritic igneous rocks, and Cambrian rocks. The area covered by the reconnaissance map of southwestern Nevada and eastern California by- Ball (1907, pi. 1) borders the quadrangle on the north. The first major contribution on the geology of the Pana- mint Butte area was by Hopper (1947, pi. 1), whose strip map from the Sierra Nevada to Death Valley covers the southern part of the Panamint Butte quadrangle and the Modoc district. Geologic Guidebook Number 1, Western Mojave desert and Death Valley region, by Wright and Troxell (1954), and the geologic map of California (Jennings, 1958, Death Valley sheet) are useful guides for the geology of the general region. Other papers that deal with the geology of nearby areas in the Panamint Range or Panamint Valley include Gale (1915), who studied Panamint Basin, Murphy (1930, 1932), who mapped the area around the Panamint silver district, Maxson (1950), who made a physiographic study of the Panamint Range, Sears (1955), who mapped in the vicinity of Tucki Mountain, and Johnson (1957), who mapped part of the Manly Peak quadrangle. Several papers resulting from the cooperative study of the Inyo County lead-silver-zinc deposits by the U. S. 10 California Division of Mines and Geology Special Report 73 Geological Survey and the California Division of Mines have been published of nearby districts. McAllister mapped the Ubehebe Peak quadrangle and adjacent Quartz Spring area (1952, 1955, 1956); MacKevett (1953) described the Santa Rosa mine; Merriam and Hall (1957) described the late Paleozoic stratigraphy of the southern Inyo Mountains; and Hall and MacKevett (1958, in press) mapped the Darwin quadrangle. The writers wish to express their appreciation to the mine owners and operators for their cooperation in this study, especially to Robert Foreman, A. L. Foss, C. R. King, Mrs. Agnes Reid, Louis Rohr, and Tom Vignich. Matt Ryan of the National Park Service at Emigrant Station in the Death Valley National Monument and Mrs. Ryan extended many courtesies to the writers that are gratefully acknowledged. J. F. McAllister of the U. S. Geological Survey spent four days in the field with the writers and was of invaluable assistance with strati- graphic problems. All fossils were identified by paleon- tologists of the U. S. Geological Survey. Identifications were made by Jean M. Berdan, R. C. Douglass, Helen Duncan, J. Thomas Dutro, Jr., W. H. Haas, Kenneth E. Lohman, W. A. Oliver, Jr., Reuben J. Ross, Jr., W. J. Sando, and Ellis L. Yochelson. GENERAL GEOLOGY The Panamint Butte quadrangle is underlain by a se- quence of metamorphic and sedimentary rocks of Pre- cambrian(?) to Permian age that is intruded by quartz monzonite plutons of Jurassic(r) age and andesite por- phyry dikes of Cretaceous (r ) age. Late Cenozoic vol- canic rocks and sedimentary deposits unconformably overlie this sequence (pi. 1). Late Precambrian(P) meta- morphic rocks are limited to three small outcrops— two in the Panamint Range and one in Panamint Valley. Coarse-grained quartz-mica schist, quartzite, and biotite- hornblende gneiss are the predominant lithologic types. Paleozoic strata range in age from Middle(?) Cambrian to Permian in a conformable sequence approximately 14,000 feet thick. Silurian and older Paleozoic rocks, which are exposed only in the Panamint Range, consist mainly of dolomite and lesser quartzite, limestone, and shale. Devonian and younger Paleozoic rocks are mainly limestone, marble, and silty limestone, and they are abundantly exposed in both the Panamint and Argus Ranges. The stratigraphy is described under 10 major lithologic sequences shown on the economic map (pi. 1). Table shows the formations that have been grouped in each major map unit. Formations have been shown only on the Modoc district map (pi. 2) and on detailed mine maps. The formation names used herein are the same as used by McAllister (1952) for the Lower Mississippian and older Paleozoic formations in the Quartz Spring area. The Lee Flat limestone was introduced by Hall and Mac- Kevett (1958, p. 8) in the Darwin quadrangle. Nomen- clature introduced by Merriam and Hall (1957) is used for the Pennsylvanian and Permian strata. Of the 10 major map units, the marble sequence, which consists predominantly of clean marble, is the most favorable for lead-silver deposits. GNEISSIC SEQUENCE The gneissic sequence includes all rocks that are meta- morphosed to gneiss, schist, or coarse-grained quartzite. The sequence is sparsely exposed in the Panamint Range and in Panamint Valley at the souhtern border of the quadrangle where it extends southwest into the Matu- rango Peak quadrangle. The ages of rocks assigned to this sequence are not known, but they are probably both Precambrian and Cambrian. Precambrian(?) rocks Rocks of probable Precambrian age are limited to two small exposures in the Panamint Range and an isolated outcrop in Panamint Valley at the southern border of the quadrangle (pi. 1). Both of the exposures in the Panamint Range are beneath thrust faults. The southerly exposure in the Panamint Range 2 miles south of Nova Canyon consists of interbedded white, red, and reddish- brown quartzite, micaceous and limy quartzite, and minor dolomite in a section 700 feet thick. The northerly ex- posure 3 miles N. 57° W. of the Lemoigne mine consists of coarse-grained quartz-mica schist and light reddish- brown quartzite. Biotite-hornblende gneiss and mica schist crop out in the isolated hill in Panamint Valley at the south end of the quadrangle. The assignment of a Precambrian age to these rocks is on the basis of similarity in lithology and degree of meta- morphism to other Precambrian rocks in the Death Val- ley area. It is possible, though, that the northerly outcrop is contact metamorphosed clastic rocks of Early Cam- brian age. Cambrian(?) rocks A gneissic sequence approximately 700 feet thick is ex- posed 1 14 miles west of the Lemoigne mine in a band 2 miles long; the base is not exposed. The sequence con- formably underlies marble, dolomitic marble, and dark- gray limestone of probable Middle Cambrian age. The sequence is a former shaly zone that has been contact metamorphosed to quartz-mica schist, gneiss, and quartzite. The gneiss and schist contain reddish garnets as much as one-fourth inch in diameter in a fine-grained groundmass of biotite, hornblende, muscovite, plagio- clase, quartz, and calcite. The age of the gneiss is probably Middle Cambrian. It conformably underlies dolomite that lithologically re- sembles the Racetrack dolomite of Middle and Late Cam- brian age. It is believed to be about the same stratigraphic horizon as the Cadiz formation of Middle Cambrian age in the Nopah Range (Hazzard, 1937, p. 314). DOLOMITE SEQUENCE The dolomite sequence is present only in the Panamint Range in the Panamint Butte quadrangle. It consists pre- 1963] Panamint Butte Quadrangle Table 1 . Stratigraphic section of the and Modoc District Panamint B'jffe quadrangle. 11 Age Map units shown on Plate 1 Lithologic units Thickness >• c 5