Gra^raE: E. EfcnvAv^ STATE OF ILLINOIS William G. Stratton, Governor DEPARTMENT OF REGISTRATION AND EDUCATION Vera M. Binks, Director 1958 Petrology and Sedimentation of the Pennsylvanian Sediments in Southern Illinois: A Vertical Profile Paul Edwin Potter Herbert D. Glass REPORT OF INVESTIGATIONS 204 ILLINOIS STATE GEOLOGICAL SURVEY JOHN C. FRYE, Chief URBANA, ILLINOIS Petrology and Sedimentation of the Pennsylvanian Sediments in Southern Illinois: A Vertical Profile Paul Edwin Potter Herbert D. Glass Ulinois State Geological Survey Report of Investigations 204 Urbana, Illinois 1958 PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS STATE OF ILLINOIS HON. WILLIAM G. STRATTON, Governor DEPARTMENT OF REGISTRATION AND EDUCATION HON. VERA M. BINKS, Director BOARD OF NATURAL RESOURCES AND CONSERVATION Hon. Vera M. Binks, Chairman W. H. Newhouse, Ph.D., Geology Roger Adams, Ph.D., D.Sc, Ll.D., Chemistry Robert H. Anderson, B.S., Engineering A. E. Emerson, Ph.D., Biology Lewis H. Tiffany, Ph.D., Pd.D., Forestry Dean W. L. Everitt, E.E., Ph.D., University of Illinois President Delyte W. Morris, Ph.D., Southern Illinois University GEOLOGICAL SURVEY DIVISION John C. Frye, Ph.D., D.Sc, Chief (64214—2800—9-57) STATE GEOLOGICAL SURVEY DIVISION -Urbana, Illinois. FULL TIME STAFF Enid Townley, M.S., Geologist and Assistant to the Chief JOHN C. FRYE, Ph.D., D.Sc, Chief M. M, Leighton, Ph.D., D.Sc, Chief Emeritus Helen E. McMorris, Secretary to the Chief Velda a. Millard, Junio Assistant to the Chief M. GEOLOGICAL GROUP L. Thompson, Ph.D., Principal Geologist Arthur Bevan, Ph.D., D.Sc, Principal Geologist, Emeritus Frances H. Alsterlund, A.B., Research Assistant COAL Jack A. Simon, M.S., Geologist and Head G. H. Cady, Ph.D., Senior Geologist and Head, Emeritus Robert M. Kosanke, Ph.D., Geologist John A. Harrison, M.S., Associate Geologist Paul Edwin Potter, Ph.D., Associate Geologist (on leave) William H. Smith, M.S., Associate Geologist Kenneth E. Clegg, M.S., Assistant Geologist Margaret A. Parker, M.S., Assistant Geologist David L. Reinertsen, A.M., Assistant Geologist Marcia R. Winslow, M.Sc, Assistant Geologist OIL AND GAS A. H. Bell, Ph.D., Geologist and Head Virginia Kline, Ph.D., Associate Geologist Lester L. Whiting, B.A., Associate Geologist Wayne F, Meents, Associate Geological Engineer Margaret O. Oros, B.A., Assistant Geologist Thomas W. Smoot, M.S., Assistant Geologist Jacob Van Den Berg, M.S., Assistant Geologist James H. Garrett, B.S., Research Assistant JuTTA L Anderson, Technical Assistant PETROLEUM ENGINEERING Carl W. Sherman, M.S., Petroleum Engineer and Head INDUSTRIAL MINERALS J. E. Lamar, B.S., Geologist and Head Donald L. Graf, Ph.D., Geologist James C. Bradbury, A.M., Associate Geologist James W. Baxter, M.S., Assistant Geologist Meredith E. Ostrom, M.S., Assistant Geologist PHYSICS R. J. Piersol, Ph.D., Physicist, Emeritus CLAY RESOURCES AND CLAY MINERAL TECHNOLOGY Ralph E. Grim, Ph.D., Consulting Clay Mineralogist W. Arthur White, Ph.D., Geologist Herbert D. Glass, Ph.D., Associate Geologist GROUNDWATER GEOLOGY AND GEOPHYSI- CAL EXPLORATION George B. Maxey, Ph.D., Geologist and Head Merlyn B. Buhle, M.S., Geologist Robert E. Bergstrom, Ph.D., Associate Geologist James E. Hackett, M.S., Associate Geologist John P. Kempton, M.A., Assistant Geologist Wayne A. Pryor, M.S., Assistant Geologist LiDiA Selkregg, D.Nat.Sci., Assistant Geologist Grover H. Emrich, M.S., Research Assistant Lowell A. Reed, B.S., Research Assistant Margaret J. Castle, Assistant Geologic Draftsman (on leave) ENGINEERING GEOLOGY AND TOPOGRAPHIC MAPPING George E. Ekblaw, Ph.D., Geologist and Head William C. Smith, M.A., Assistant Geologist STRATIGRAPHY AND AREAL GEOLOGY H. B. Willman, Ph.D., Geologist and Head Elwood Atherton, Ph.D., Geologist David H. Swann, Ph.D., Geologist Charles W. Collinson, Ph.D., Associate Geologist John A. Brophy, M.S., Assistant Geologist T. C. Buschbach, M.S., Assistant Geologist F. L. Doyle, M.S., Assistant Geologist Robert W. Frame, Supervisory Technical Assistant Romayne S. Ziroli, Technical Assistant Joseph F. Howard, Assistant COAL CHEMISTRY G. R. YoHE, Ph.D., Chemist and Head Thomas P. Maher, B.S., Special Associate Chemist Joseph M. Harris, B.A., Research Assistant PHYSICAL CHEMISTRY J. S. Machin, Ph.D., Chemist and Head Jose M. Serratosa, Dr.Sc, Special Associate Chemist Neil F. Shimp, Ph.D., Associate Chemist Daniel L. Deadmore, M.S., Assistant Chemist JuANiTA Witters, M.S., Assistant Physicist FLUORINE CHEMISTRY CHEMICAL GROUP Grace C. Finger, B.S., Research Assistant CHEMICAL ENGINEERING H. W. Jackman, M.S.E., Chemical Engineer and Head R. J. Helfinstine, M.S., Mechanical and Adminis- trative Engineer B. J. Greenwood, B.S., Mechanical Engineer Robert L. Eissler, M.S., Assistant Chemical Engineer James C. McCullough, Research Associate (on leave) Walter E. Cooper, Technical Assistant Cornel Marta, Technical Assistant Edward A. Schaede, Technical Assistant G. C. Finger, Ph.D., Chemist and Head Laurence D. Starr, Ph.D., Associate Chemist Donald R, Dickerson, B.S., Special Assistant Chemist Richard H. Shiley, B.S,, Special Research Assistant Raymond H. White, B.S., Special Research Assistant X-RAY W. F. Bradley, Ph.D. Chemist and Head ANALYTICAL CHEMISTRY O. W. Rees, Ph.D., Chemist and Head L. D. McVicker, B.S., Chemist Emile D. Pierron, M.S., Associate Chemist William J. Armon, M.S., Assistant Chemist Francis A. Coolican, B.S., Assistant Chemist Mary Ann Miller, B.S., Research Assistant Louise J. Porter, A.B., Research Assistant IsTVAN Pusztaszeri, Research Assistant JoAnne K. Wilken, B.A., Research Assistant George R. James, Technical Assistant Benjamin F. Manley, Technical Assistant MINERAL ECONOMICS GROUP W. H. VosKuiL, Ph.D., Principal Mineral Economist Hubert E. Risser, Ph.D., Mineral Economist W. L. BuscH, A.B., Associate Mineral Economist ADMINISTRATIVE GROUP EDUCATIONAL EXTENSION George M. Wilson, M.S., Geologist and Head Ira E. Odom, M.S., Research Assistant Shirley Trueblood, B.S., Research Assistant GENERAL SCIENTIFIC INFORMATION Arlene Green, Technical Assistant Del Marie Rogers, B.A., Technical Assistant Genevieve Van Heyningen, Technical Assistant PUBLICATIONS Dorothy E. Rose, B.S., Technical Editor Meredith M. Calkins, Geologic Draftsman Betty M. Lynch, B.Ed., Assistant Technical Editor Donna R, Wilson, Assistant Geologic Draftsman MINERAL RESOURCE RECORDS Vivian Gordon, Head Betty J. Hanagan, M. A., Research Assistant Hannah Fisher, Technical Assistant Rosalie Pritchard, Technical Assistant Helen Ross, B.A., Technical Assistant Yvonne M. Sather, Technical Assistant Barbara L. Scott, B.A., Technical Assistant Elizabeth Speer, Technical Assistant TECHNICAL RECORDS Berenice Reed, Supervisory Technical Assistant Judith Flach, Technical Assistant Miriam Hatch, Technical Assistant LIBRARY Olive B. Ruehe, B.S., Geological Librarian Beverly Ann Ohren, B.S., Technical Assistant FINANCIAL RECORDS Velda a. Millard, In Charge Eleanor A. Drabik, B.A., Clerk IV Virginia C. Sanderson, B.S., Clerk-Typist III Carolyn S. Toppe, Clerk-Typist II Patricia A. Northrup, Clerk-Typist I Topographic mapping in cooperation United States Geological Survey * Divided time October 22, 1957 with the SPECIAL TECHNICAL SERVICES William Dale Farris, Research Associate Beulah M. Unfer, Technical Assistant A. W. GoTSTEiN, Research Associate Glenn G. Poor, Research Associate* Gilbert L. Tinberg, Technical Assistant Wayne W. Nofftz, Supervisory Technical Assistant DoNovoN M. Watkins, Technical Assistant Mary Cecil, Supervisory Technical Assistant Ruby D. Prison, Technical Assistant CLERICAL SERVICES Mary M. Sullivan, Clerk-Stenographer III Rita J. Nortrup, Clerk-Stenographer II Lillian W. Powers, Clerk-Stenographer II Marilyn Bevill, Clerk-Stenographer I Barbara A. Carling, Clerk- Stenographer I Marilyn Scott, Clerk- Stenographer I Edna M. Yeargin, Clerk- Stenographer I Laurel F. Griffin, Clerk-Typist I Jean M. Ward, Clerk-Typist I William L. Mathis, Messenger-Clerk II Lorene G. Wilson, Messenger-Clerk I AUTOMOTIVE SERVICE Glenn G. Poor, In Charge* Robert O. Ellis, Automotive Shop Foreman David B. Cooley, Automotive Mechanic EvERETTE Edwards, Automotive Mechanic RESEARCH AFFILIATES J Harlen Bretz, Ph.D., University of Chicago Stanley E. Harris, Jr., Ph.D., Southern Illinois University M. M. Leighton, Ph.D., D.Sc, Research Pro- fessional Scientist, State Geological Survey A. Byron Leonard, Ph.D., University of Kansas Carl B. Rexroad, Ph.D., Texas Technological College Walter D. Rose, Ph.D., University of Illinois Paul R. Shaffer, Ph.D., University of Illinois Harold R. Wanless, Ph.D., University of Illinois Paul A. Witherspoon, Ph.D., University of Cali- fornia CONSULTANTS George W. White, Ph.D., University of Illinois Ralph E. Grim, Ph.D., University of Illinois CONTENTS Page Introduction 7 Acknowledgments 8 Regional geology 8 Paleozoic setting 8 Eastern Interior coal basin 9 Stratigraphy and lithology 9 Sedimentary structures 18 Major external structures 18 Cross-bedding 18 Ripple marks 18 Current fluting and drag grooves 19 Current lineation .19 Load casts 19 Cut-and-fill 20 Slump structures 20 Minor internal structures 21 Directional structures 22 Additional significance 23 Petrology 23 Sandstones 24 Caseyville sandstones 25 Transition sandstones 29 Sandstones above the New Burnside coal 30 Significant variation in petrographic properties. . 32 Sandstone classification 33 Limestones 34 Clay mineralogy 35 Post-depositional diagenesis 35 Provenance 43 Probable transport pattern 43 Composition of the source area 44 Sandstone maturity 45 Environment of deposition 48 Environment 48 Tectonics and climate 52 Summary 53 Appendix — Sample locations . 55 References 58 ILLUSTRATIONS Figure 1. Regional setting showing relation of study area and some major Pennsylvanian basins 8 2A. Generalized structure of Pennsylvanian sediments in the Eastern Interior coal basin 10 2B. Areas of differential subsidence in the Eastern Interior coal basin .... 11 3. Generalized stratigraphic column and vertical mineralogic variation . 12 4. Areal extent of younger Pennsylvanian sediments not present in study area . 15 5. Contrasting lithologic proportions above and below the New Burnside coals 16 6. Channel behavior of Pennsylvanian argillaceous sandstones above the New Burnside coals in Jefferson County, Illinois 17 7. Block diagram of a typical well cross-bedded Pennsylvanian sandstone in the Eastern Interior coal basin 18 8. Load casts in thin-bedded Caseyville sandstone exposed in road cut . . . 19 9. Overturned cross-bedding .20 Figure 10. Convoluted bedding in the Delwood sandstone 21 11. Diagrammatic representation of the origin of disturbed bedding 22 12. Cross-bedding and directional distribution of post-Casey ville sandstones and Caseyville outcrop and directional distribution 24 13. Contrasting abundances of sand-fraction muscovite, chlorite, and biotite in Pennsylvanian sandstones 28 14. Cumulative curves of counts of 100 tourmaline long axes and percentage of round tourmaline grains 30 15. Diagrammatic summary of vertical variation of sandstone properties. ... 31 16. X-ray spectrometer patterns (Cu radiation) of the clay fraction from a sub- graywacke sandstone and an associated shale 36 17. Post-Casey ville cross-bedding mean and 90 percent confidence wedge of study area superimposed on basal Pennsylvanian How pattern and mineral asso- ciations 44 18. Contrasting proportions of round tourmaline grains of the Pennsylvanian sub- graywackes and orthoquartzites and the Ordovician St. Peter sandstone . 48 19. Clay mineral composition of Trivoli cyclothem 51 Plates facing lA. Cross-bedding as exposed at the spillway of Crab Orchard Lake 26 IB. Asymmetrical current ripples in a Tradewater sandstone 26 2A. Symmetrical oscillation ripple marks in fine-grained DeKoven sandstone ex- posed in the Will Scarlet strip mine 27 2B. Interference ripple marks of a lower Tradewater sandstone 27 3A. Probable antidune bedding exposed in a small creek bed 28 3B. Current fluting and drag grooves shown on underside of thin-bedded and fine- grained McLeansboro (Trivoli?) sandstone 28 4A. Current lineation in thin-bedded and fine-grained Caseyville sandstone exposed in creek bed 29 4B. Underside of basal Caseyville orthoquartzitic sandstone showing unusual de- velopment of oriented load casts 29 5. Two views of a cut-and-fill structure, called a "ripple scour," in a Tradewater sandstone 32 6. Contrasting hand specimen and microscopic appearances of Pennsylvanian orthoquartzites and subgraywackes 33 7. Comparison of Pennsylvanian siltstone-shale interlaminations and modern tidal flat interlaminations from the Wadden Sea 34 8. Comparison of Pennsylvanian siltstone-shale interlaminations and modern Texas Gulf Coast interlaminations 35 TABLES Table 1. Vertical contrasts in Pennsylvanian sedimentation in the Williamson County area 14 2. Optimum occurrence of sedimentary structures and sandstone types .... 23 3. Variance components for the post-Caseyville Pennsylvanian cross-bedding in and near Williamson County 25 4. Modal composition of Pennsylvanian sandstones 26 5. Heavy minerals, tourmaline roundness, and micas in Pennsylvanian sandstones 27 6. Average sandstone composition 28 7. Comparative sorting for Pennsylvanian subgraywackes and orthoquartzites and the St. Peter sandstone 29 8. Pennsylvanian clay mineral composition 37 9. Ranking of clay mineral composition in Pennsylvanian shales 40 10. Average composition of subgraywacke and orthoquartzite outcrop and core 41 samples 11. Average clay mineral contrasts between two lithologies and petrographic facies in outcrops and cores 42 12. Petrographic properties and composition of source area 46 13. Environmental aspects of clay mineralogy 52 PETROLOGY AND SEDIMENTATION OF THE PENNSYLVANIAN SEDIMENTS IN SOUTHERN ILLINOIS: A VERTICAL PROFILE Paul Edwin Potter and Herbert D. Glass ABSTRACT An integrated study of outcrop and subsurface stratigraphy, sedimentary structures, petrography, and clay minerals was made of the Pennsylvanian sediments along a portion of the Eastern Interior coal basin border in southern Illinois. The data obtained were used to reconstruct Pennsylvanian provenance and depositional environments. Data re- lating to provenance were obtained primarily from the petrology and directional sedi- mentary structures of the sandstones. Studies of local and regional patterns of lithologic variation, kinds of sedimentary structures, and fossil content were the basis for environ- mental reconstruction. This information indicates that the Pennsylvanian sediments in southern Illinois accumulated on a coupled coastal plain and shallow marginal marine shelf, both sloping to the southwest. Both coastal plain and shelf became progressively more negative and probably more gently dipping during Pennsylvanian time. Cross-bedding indicates that throughout the history of this coastal-plain — marginal-shelf, sediments were transported toward the southwest. Initially, the sediments in transport to and across this physio- graphic couple were derived from pre-existing sediments, but, as erosion progressively unroofed metamorphic and/or igneous rocks, immature elastics reached the basin. Although the rate of basin subsidence was the controlling factor for contrasts in lithologic proportions and clay content of sandstones, it had only a negligible effect on clay mineral composition and produced no major change in sand transport mechanism. INTRODUCTION The primary objective of this study was to provide a closely integrated re- construction of Pennsylvanian sedimenta- tion in a small portion of the Eastern Interior coal basin. The second objective, of more general interest, was to determine what inter-relationships exist between stratigraphy (gross lithology), sedimen- tary structures, sedimentary petrology, and clay mineralogy in the coal measures of an intracratonic basin. To achieve these objectives, a detailed field and laboratory study was made of some 1800 feet of the Pennsylvanian sys- tem exposed in and near Williamson County in southern Illinois. Emphasis was placed upon vertical variation over a limited area because 1) this minimized the area of field work, thus permitting more detailed observation, 2) it favored the laboratory study of a greater rather than a smaller number of variables, and 3) it maximized the likelihood of con- trasts between depositional environments and minimized the effect of regional variations. An abundance of subsurface diamond-drill hole samples and logs sup- plemented outcrop study. Because the area is very small in relation to the dis- tributive processes of Pennsylvanian sedi- mentation in either the north-central United States or even in the Eastern In- terior coal basin, this study may be con- sidered an essentially vertical "point" profile. In presenting the results we have tried to separate geologic description, be it stratigraphic or petrologic, from geo- logical interpretation. Thus, the sections on "Regional Setting," "Stratigraphy," "Sedimentary Structures," and "Petrol- ogy" are descriptive, as opposed to the interpretative sections on "Provenance," "Environment," and "Tectonics and Climate." A companion publication, "Geology and Coal Resources of the Pennsylvanian System in Williamson and Adjacent Parts of Johnson and Union Counties, Illinois" (in preparation), covers much the same area as this report and was part of the same research project. Its primary objec- tive is an evaluation of the area's coal resources. [7] 8 ILLINOIS STATE GEOLOGICAL SURVEY In contrast, the present study is a con- tribution to fundamental sedimentary rock research. As such it represents the behef of the IlHnois State Geological Sur- vey that research directed toward funda- mental objectives is basic to future prac- tical research. Acknowledgments The technical and geological assistance of other Survey members did much to make our study more comprehensive. Gordon Smale and Russell Lennon helped collect and process some of the samples. Dale Farris made the photo- graphs of outcrops and cores. The geo- logical criticisms by W. F. Bradley, R. M. Kosanke, W. H. Smith, J. A. Simon, and H. B. Willman, all of the Illinois State Geological Survey, were most helpful. The photographs of modern Gulf Coast sediment cores were supplied by Hugh Bernard, Shell Development Corp., Houston, Texas. L. M. J. U. Van Straa- ten, Geological Institute, Rijks Univer- sity, Groningen, Netherlands, supplied the pictures of the modern Wadden Sea sedi- ments. E. C. Dapples, Northwestern Uni- versity, Evanston, Illinois, F. J. Pettijohn, Johns Hopkins University, Baltimore, Maryland, Raymond Siever, Harvard University, Cambridge, Massachusetts, and Tj. H. Van Andel, Scripps Institution of Oceanography, Lajolla, California, read the manuscript and made helpful suggestions. Regional Geology paleozoic setting The major tectonic elements of the northeastern United States in relation to the area of study are shown in figure 1. These include the crystalline-metasedi- ment core of the Appalachians, the Cana- dian shield, and four major Paleozoic basins — the Appalachian, Michigan, East- ern Interior, and Mid-Continent coal basins — that have been isolated from one another by post-Paleozoic tectonics and erosion. Of the four basins, the Michigan and Eastern Interior basins and large portions of the Mid-Continent basin lie on the buried south-central flanks of the Canadian shield. Fig. 1. — Regional setting showing relation of study area and some major Pennsylvanian basins. PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE Throughout most of Paleozoic time, the buried flanks of the shield served, in the north-central states, as a slowly sub- siding platform for the accumulation of the typical products of cratonic sedimen- tation — dominant and widespread car- bonates, and elastics consisting essentially of shales and orthoquartzitic sandstones. Beginning in Chester (Upper Missis- sippian) time, sandstones became more abundant but continued to be ortho- quartzitic in character (Siever, 1953). In the Eastern Interior coal basin, a major unconformity separates the Mississippian from the Pennsylvanian (Weller and Bell, 1937, p. 777; Weller and Sutton, 1940, p. 847-850; Siever, 1951). Paleozoic sedimentation terminated in the Illinois area with the overwhelming dominantly clastic Pennsylvanian sedimentation that began with the deposition of orthoquartz- itic sandstones and ended with the depo- sition of subgraywacke sandstones. EASTERN INTERIOR COAL BASIN The Eastern Interior coal basin covers an area of approximately 53,000 square miles (Wanless, 1955, p. 1753) in portions of Illinois, Indiana, and Kentucky. The Pennsylvanian rocks rest unconformably on sediments that range from upper Chester (Kinkaid) along the basin's southern border to Ordovician along its northern border. Significant erosion oc- curred during the Mississippian-Pennsyl- vanian interval, which closed with epei- rogenic uplift that produced an inte- grated system of south - southwestward oriented channels (Siever, 1951; Wanless, 1955, p. 1764-1766). The channels have typical dendritic patterns and are en- trenched as much as 200 feet. In William- son County, subsurface data are insuffi- cient for detailed mapping of the channels but indicate as much as 100 feet of relief on the Kinkaid limestone. The regional structural elements of the basin include a series of anticlines and monoclines and two prominent post- Pennsylvanian fault systems, the Wabash Valley and the Cottage Grove - Rough Creek (fig. 2- A). The Eastern Interior coal basin can be further divided into a structurally deep portion and a surround- ing shallower basin margin (fig. 2-A). The elevation of coal No. 2 above sea level (fig. 2-A) rather generally defines the structural contrast. Figure 2-B shows the areas of differential subsidence in the basin and indicates that the rapidly sub- siding portion of the basin continued an undetermined distance south of the pres- ent southern outcrop limit (Wanless, 1955, p. 1780). To the west and north the rapidly subsiding portion was separated from a shelf area by a transition zone. With the exception of the basal Casey- ville and Mansfield sediments, largely re- stricted to the rapidly subsiding portion of the basin and the eastern transition zone, differences between shelf and basin sedimentation are best expressed in con- trasting interval thicknesses rather than in major contrasting facies of sedimenta- tion. Thicknesses of more than 2000 feet are typical for the rapidly subsiding por- tion of the basin. The area of study in and near Williamson County lies in the rapidly subsiding portion of the basin. STRATIGRAPHY AND LITHOLOGY The 1800 feet of Pennsylvanian sedi- ments in and near Williamson County range in age from Lower Pennsylvanian (Caseyville group) through Middle Penn- sylvanian (Tradewater, Carbondale, and the lower portion of the McLeansboro group) to Upper Pennsylvanian (upper portion of the McLeansboro).* The stratigraphic column (fig. 3) shows the boundaries of these groups, their relation to the Morrowan, Atokan, DesMoinesian, and Missourian series (Siever, 1956), and the more prominent lithologic units in each group. Figure 4 shows the areal ex- tent of the stratigraphically younger rocks not present in the area studied. Average thicknesses of the four strati- graphic groups in and near Williamson County are shown in figure 3. Thinning * See Wanless (1956) and Siever (1956) for a com- plete discussion of this classification. 10 ILLINOIS STATE GEOLOGICAL SURVEY K STUDY AREA Fig. 2A. — Generalized structure of Pennsylvanian sediments in the Eastern Interior coal basin showing the structurally deep part of the basin and some prominent anticlines and faults (modified and adapted from Wanless, 1955). PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 11 ^^^ ^'H / ^ ^f:': i St. Louis STUDY AREA Fig. 2B. — Areas of differential subsidence in the Eastern Interior coal basin. Large black circles show location of two areas of present maximum thickness. 12 ILLINOIS STATE GEOLOGICAL SURVEY from north to south appears to be neg- ligible, but there is more thinning from east to west across the area. The megascopic rock properties exhibit significant vertical variation (table 1). In general the sediments below New Burn- side coals have properties different from those above the New Burnside coals. Below the New Burnside coals, shales are approximately equal volumetrically to sandstones, there are no known limestones, and coal beds generally are less than 2 feet thick and not laterally persistent. Marine invertebrate fossils are present but very rare. In this zone of dominantly clastic rocks, it is difficult to trace with certainty many of the sand- stones. Below the New Burnside coals, how- ever, the top of the Caseyville marks a sharp break in sandstone type. The sand- stones of the Caseyville are clean quartz sands that commonly contain well rounded quartz pebbles. Beginning with the overlying Grindstaff sandstone (fig. 3), the Tradewater sandstones become mica- ceous and argillaceous. Coal, shale, and concretionary fragments replace the quartz pebbles as the prominent con- glomeratic elements. The lower Trade- water sandstones are transitional between those of the Caseyville and those above the New Burnside coals. The lithologic contrast between the sediments above and below the New Burnside coals is shown in figure 5. Above the New Burnside coals there is much less sandstone and much more shale (marine fossils common) than below. Abundantly fossiliferous limestones and black fissile shales become significant. Compared to their frequency in the older underlying sediments, coal beds are abundant. The limestones, black fissile shales, coal beds, and underclays com- monly can be traced over many counties. The sandstones above the New Burn- side coals are uniformly argillaceous and micaceous. Typically, they are the "salt and pepper" textured subgraywackes. iu> Q.-J Z5C/) GENERALIZED STRATIGRAPHIC SECTION MT CARMEL SS. -SHOAL CREEK LS. SHOAL CREEK COAL SHOAL CREEK SS. MACOUPIN LS. MACOUPIN COAL TRIVOLI LS. ^TRIVOLI COAL TRIVOLI SS -3RD CUTLER RIDER COAL -2ND CUTLER RIDER COAL 'LIBERTY" SS. ST CUTLER RIDER COAL ■CUTLER LS. ■CUTLER COAL ■BANKSTON LS. ANVIL ROCK SS. JAMESTOWN COAL HERRIN (NO. 6) COAL COAL NO. 5A ST DAVID LS. NO. 5 COAL -NO. 4 COAL ■PLEASANTVIEW SS. NO. 2 COAL ■PALZO SS. •DEKOVEN COAL DAVIS COAL •DAVIS SS. -STONEFORT LS. ^-CURLEW LS. J-CREAL SPRINGS SS. NEW BURNSIDE COALS -MURRAY BLUFF SS. DELWOOD "SS. •WILLIS COAL GRINDSTAFF SS. REYNOLDSBURG COAL SANDY ZONES OF CASEYVILLE -KINKAID LS. Series ond stage token from Moore and Thompson (1949) Fig. 3. — Generalized stratigraphic PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 13 MODAL SAND COMPOSITION HEAVY MINERALS 20 40 60 80 100 PERCENT TOURMALINE ROUNDNESS CLAY MINERALOGY OF SHALES 20 40 60 80 100 25 50 75 100 PERCENT PERCENT 2 4 6 8 10 PARTS IN TEN column and vertical mineralogic variation. 14 ILLINOIS STATE GEOLOGICAL SURVEY u u B 1 6c c5 Locally derived pebbles and cobbles of coal, concretionary fragments, shale and limestone — > Dominantly well rounded far traveled quartz pebbles la It C/0 ■^ s c Vh 3 C ^?2> C t/3 rt-ct ^ c/5 c c 8 o • Si > J.J g c ^ ^-S 4-1 3 c .2 "si "1 — CX c o B 3 ci.'H c > a; t3 C c/3 11 ^ ^ s C B B^ >'t3 rt So II u ^ — ^ s s 2 ^ § > c/) c/5 0/3 C OJ ii CO rt (U c/3 > c „ § S 1I h:z;w 8 c32gn ^ > c/) a, 2 c/3 C lU C u H u PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 15 J ^- \ • 1 Maximum thickness of "",/ /^ • •'.'.. • • * . ■ . ■ ^Vl ^^^ higher sediments {' ' ^^y^^ ' ' ' \ ' ' ^ <^ • s V^ /y' ' ->"''" ■ ^- ■ '1\"'"" ■■ ' T \\ /•'..•/"■ ■ 'NOT' ■ ^' ■■Vx '' \ S- .■ .). . .PRESENT . . vj ■M v-A.;]." : : in- : '•,oo''\:'yA Cj) ■ ' ■A\ : STUDY : .• :;a- '■■■■% St. Louis? /' . • "3 • • • • • •--■'''■ ■ • '^ /Qr-,<:^ ■ '^'^^'^ ■ •/•■• ••.'i ^ • ^^H ■ y • ■ . • . :^- ■ T ( Fig. 4. Areal extent (open stipple) of younger Pennsylvanian sediments not present in study area (modified and adapted after Wanless, 1955, p. 1778-1779, fig. 7). The clean quartz sandstones o£ the Casey- ville group and the micaceous-argillaceous sandstones above the New Burnside coals are in hand specimen quite distinct from each other (pi. 6). Within either facies, however, individual sandstones generally cannot be distinguished in hand speci- men. The conglomeratic elements of the subgraywacke sandstones consist of such locally derived materials as fragments of reworked concretions, coal, limestone, and shale. Well rounded quartz pebbles like those of the Caseyville never have been observed. In contrast to the above vertical varia- tions, the abundance of tree-trunk casts in the sandstones and leaf compressions in the shales is much the same throughout the section. Nor is there a major change in the color of the interbedded shales. 16 ILLINOIS STATE GEOLOGICAL SURVEY SAND AND SILT INTERLAMINATED WITH SHALE UNDERCLAY LIMESTONE BLACK FISSILE SHALE (3759 ft.) ALL OTHERS (2820 ft.) Fig. 5. — Contrasting lithologic proportions above the New Burnside coals (A) and below the New Burnside coals (B). Numbers in parentheses represent the total footage of diamond drill core upon which estimate is based. Although greenish gray shales are more common above the New Burnside coals, dominant shale colors throughout the section are medium to dark gray. Hence the striking contrast between hand speci- mens of the basal clean quartz sandstones and upper subgraywacke sandstones does not extend to their associated shales. Two significant megascopic features of sediments deserve special comment — sand-body shape and small-scale vertical lithologic variation. Because of the pres- ence of interbedded marker beds (coals and limestones), sand-body shape is most readily ascertained in the sediments above the New Burnside coals. The develop- ment of sandstone channels is the most prominent morphologic feature of the sandstones. In nearby Jefferson County, Illinois, Mueller and Wanless (1957) made a study of this channel behavior (fig. 6). Qualitatively, the channel fill is coarser-grained, more cross-bedded, and more commonly conglomeratic than its non-channel equivalents. In non-channel areas, the sands are finer-grained and generally conformable with the under- lying rocks. The presence of channel sandstones that have eroded stratigraphic marker beds and changed stratigraphic intervals through differential compaction locally complicates correlation. The ab- sence of well defined and traceable marker beds below the New Burnside coals makes it difficult to obtain data on the shape of sand-bodies in the Lower Tradewater and Caseyville. Small-scale vertical lithologic variation is restricted below the New Burnside coals because the sediments consist essen- tially of two components — shale and sand. There is little lithologic contrast above and below the thin coal beds of this sequence. The advent of more defi- nitely marine sedimentation above the New Burnside coals produced pro- nounced vertical lithologic contrast above and below coal beds. Fossiliferous (ma- rine invertebrates) shales, limestones, and black fissile shales are found above coals; underclays, nodular limestones, and gen- erally nonfossiliferous shales and sand- stones are below coals. Such a sequence of lithologic units, ideally consisting of 10 PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 17 KEY Trivol i ^ Gimlet Anvil Rock Cuba St. David /Afe' k- V:: •:•;•■ ;••':••■ • Pleasantview :^^^^k y^' \s^ Paizo ^■•••k:-''^?! »i^i\:v-; R.IE. R.2E. R.3E. SCALE 2 4 6 Miles D R.4E. Fig. 6. — Channel behavior of Pennsylvanian argillaceous sandstones above the New Burnside coals in nearby Jefferson County, Illinois (from Mueller and Wanless, 1957). units (several different types of lime- stones and shales are recognized) has been termed a cyclothem (Wanless and Weller, 1932). Ideally this ordered litho- logic sequence can be represented, from its basal sand (A), through the coal (E), to the final shale (J), by the single permutation: ABCDEFGHIJ wherein A = sandstone; B=^gray sandy shale; C = "freshwater" limestone; D = underclay; E = coal; F = gray shale (some marine fossils); G = limestone (marine fossils); H = black shale (marine fossils); I = limestone (marine fossils); J = gray shale (marine fossils). Although any sin- gle section rarely contains all the units, the order is commonly (but not always) preserved so that the actual cyclothem may consist of only the units ABDEGHJ or or even only ABDHG DEJ The tendency for the development of ordered lithologic sequences, complete or incomplete, is the most prominent charac- 18 ILLINOIS STATE GEOLOGICAL SURVEY 38 ft. Fig. 7. — Block diagram of a typical well cross-bedded Pennsylvanian sandstone in the Eastern In- terior coal basin. teristic of the Pennsylvanian sediments above the New Burnside coals. SEDIMENTARY STRUCTURES The sedimentary structures of Pennsyl- vanian clastic sediments that are most prominent are associated with the silty and sandy sediments. It is convenient to consider these features in terms of major external structures (shown in outcrops) and minor internal structures (shown in cores). Major External Structures The arenaceous Pennsylvanian sedi- ments of this area contain almost every type of major external sedimentary struc- ture. These include cross-bedding, ripple marks, current fluting and drag grooves, current lineation, cut-and-fill, load casts, and slump structures. Cross-bedding Cross-bedding is the most prominent sedimentary structure. It is probable that no Pennsylvanian sandstone of any ap- preciable thickness and areal extent is without cross-bedding. It is especially abundant in the coarser grained sand- stones. The shapes of the cross-bedded units are best described in terms of length-to- width-to-thickness ratios. With large (greater than 10?) length-to-width ratios, the bottom surface of the crossbed is notably concave and is called "festoon" by some authors (pi. 1-A), With smaller length-to-width ratios (near unity?) the basal surface becomes sensibly flat and the term planar or torrential has been applied. A complete gradation appears to exist between planar and festoon cross- bedding. In terms of size, cross-bedded units vary as much as 100 times (mostly in length and width) from micro-cross-bedding (the "rib and furrow" of some authors), which may be only a few inches wide and less than two feet long, to cross-bedded units that may be 20 to 40 feet wide and 80 to 120 feet long. Maximum thickness of cross-bedded sedimentation units is gen- erally 1 to 4 feet, although some units are as much as 12 feet thick. Regardless of scale, the foreset beds of these units are commonly convex in the up-current direction. They are noticeably so in those cross-bedded units with high length-to-width ratios (pi. 1-A). Figure 7 shows diagrammatically a series of cross-bedded sedimentation units in a typical well cross-bedded Pennsyl- vanian sandstone. Ripple marks Although not as prominent as cross- bedding, ripple marks are probably even PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 19 Fig. 8. — Load casts (drawn from a photograph) in thin-bedded Casey ville sand- stone exposed in road cut along the east side of U. S. highway 45, ap- proximately 5 miles north of Vienna in NE14 SWi/4 NWV4 sec. 14, T. 12 S., R. 3 E., Johnson County, Illinois. more abundant. They generally are best seen in the thinner bedded, slabby, and finer grained sandstones or siltstones and are nearly always best exposed in creek beds. Although gradations are probable, it is convenient to classify the ripple marks into three types: asymmetrical (current), symmetrical (oscillation), and interfer- ence (pis. 1-B, 2-A, and 2-B). Asymmetri- cal and interference ripples are the most common. A fourth type of ripple mark, probably antidune bedding (Gilbert, 1914, p. 11- 31) or regressive sand waves (Bucher, 1919, p. 165), was observed at only one locality in the Tradewater sandstone (pi. 3-A). Antidune bedding, the migration of sand waves in the up-current direction, is the response to a higher current velocity than that which produces ordinary rip- ples (Gilbert, 1914, p. 30-32). Although antidune bedding often can be found in glacial outwash sands near the ice front (rapid velocity changes), its preservation in most sands is rare because decrease of velocity is generally sufficiently slow so that down-current transport produces ordinary ripples rather than regressive sand waves. Current fluting and drag grooves Current fluting and drag grooves (pi. 3-B) also are present in this area but are not common. They are most likely to be found in the finer grained and thin- bedded sandstones. Current fluting results from the erosion produced by subparallel currents at the sediment interface. Drag grooves develop when currents drag debris across the sediment interface. Current lineation Current lineation also is a response to flow at the sediment interface. As shown in plate 4-A, the lineated structure can persist through a number of laminae. Current lineation, like current fluting, is best seen in the finer grained sandstones but is very rare. Load casts Figure 8 shows an unusually well de- veloped series of load casts. Load casts generally are best seen in the thinner bedded, fine-grained sandstones that are 20 ILLINOIS STATE GEOLOGICAL SURVEY not cross-bedded. They are commonly developed along specific horizons. They can occur either at the interface of sand- stone beds or along sandstone-shale con- tacts. Load casts are an example of soft sediment deformation and result from the mechanical protrusion of the over- lying into the underlying bed prior to consolidation. They may be oriented or unoriented. Oriented or directional load casts, such as those in plate 4-B, were formed in similar manner except that the slope of the interface was sufficiently inclined so that fiowage had a preferred direction. Directional load casts are very rare. The best examples have so far been found in the Caseyville sandstones. Depending on the local slope of the sedimentation surface at or shortly after deposition, a complete gradation between directional and nondirectional load casts seems probable. The dominance of non- directional rather than directional load casts throughout this entire 1800-foot Pennsylvanian section indicates that the depositional slope was never steep as in some geosynclinal flysch sequences.* Cut-and-fiU Cut-and-fill structures are common throughout the entire section. Locally de- rived conglomerates often are associated with the largest of these structures. Plate 5 shows an unusually fine ex- ample of a special type of cut-and-fill structure, here termed a "ripple scour." Such scours are ellipsoidal in outline, commonly gently concave upward, range in length from 2 to 6 feet, and often have ripple marks oriented at right angles to the long axes of the scour trough. Ripple scours have been observed only in the sandy sediments. They are present throughout the section. Commonly they * Kuenen (1957) recently has described in detail morphologically similar features from the gray- wacke sandstones. He presented evidence for a primary erosional origin in addition to the "flowage" origin described above. Kuenen (1953b, p. 23-25) and Sanders (1957, p. 200) have presented helpful criteria to distinguish bet-ween these two different origins. Because these cri- teria are not always applicable, the term "ori- ented sole marking" has much to commend it. Sanders (1957, p. 199-200) also briefly reviews the rather confusing terminology on the subject. Fig. 9. — Overturned cross-bedding (drawn from a photograph) as exposed at the crest of the hill along the west side of Illinois highway 37, approximately one mile south of Goreville in NEi/4 SE14 SEi/4 sec. 27, T. 11 S., R. 2 E., John- son County, Illinois. are associated with the well cross-bedded, coarser, and generally ripple-marked sandstones. At individual outcrops, their long axes tend to be subparallel. Quali- tative observation indicates that the long axes of ripple scours are commonly subparallel to the local cross-bedding direction. Plate 5 shows the salient features of their origin. Deposition of the underlying bed was followed by a subsequent thread of turbulence that eroded the elongate scour. The transverse ripples originated in the final stages of this erosion. Deposi- tion of the overlying bed subsequently filled the ripple-scour trough. Ripple scours can be found at many outcrops, and at a few outcrops are the most abundant sedimentary structure. Slump structures Slump structures include overturned cross-bedding, convolute bedding, and small, free-gravity slides. Only overturned cross-bedding is relatively common, and a typical example is shown in figure 9. Overturning in the down-current direc- tion prior to deposition of the overlying bed is inferred. At some places half a dozen or so sedimentation units exhibit more or less continuous overturned fore- set beds over areas of a few hundred feet. Comparable structures in other cross- bedded rocks have been described by PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 21 Fig. 10. — Convoluted bedding (drawn from a photograph) in the Del wood sandstone as exposed in the north side of an eastward-flowing tributary of Katy Ridge Hollow in SWi/4 SE14 SWi/4 sec. 18, T. 11 S., R. 5 E., Pope County, Illinois. Knight (1929, p. 74-78), Kiersch (1950, p. 939-941), Kuenen (1953a, p. 1051), Fuller (1955, p. 164) and others. Convoluted bedding is present (fig. 10). It appears to be identical to that described by Rich (1950, p. 729-730) and Kuenen (1952, p. 32-33; 1953a, p. 1056-1058). Slumped and folded beds of outcrop dimensions occur at two outcrops: one at the spillway of Crab Orchard dam in the SEi/4 NWi/4 NWi/4 sec. 30, T. 9 S., R. 1 E., and one just south of the bridge over Crab Orchard Creek in the SE14 NW14 NEi^ sec. 2, T. 9 S., R. 1 W., Jack- son County, in the vicinity of the DuQuoin monocline. Because the mono- cline marks the boundary between a rapidly subsiding basin and a more stable shelf, slide structures might be most abundant along this tectonic structure. Soft-sediment slump structures of more extreme types such as sandstone balls, pull-aparts, and ptygmatic folding (Kue- nen, 1949; Kuenen and Carozzi, 1953, p. 364) have not been observed. Their ab- sence, along with the rarity of directional load casts, indicates that the slope of the sedimentation surface was very low. Minor Internal Structures Minor internal structures are best seen in diamond drill cores. They include dis- turbed bedding, animal burrows, and graded bedding. Disturbed bedding (fig. 11) is best devel- oped in siltstone-shale interlaminations, and generally occurs in zones less than one foot thick. Disturbed zones probably have several origins. They could have re- sulted from minor slumping, from depo- sition of the laminations on subsequently compacted plant debris, from animal bur- rows, or from mechanical distortion in- duced by the weight of an overlying sand body. It is not always possible to deter- mine a specific origin. For example, neither animal burrows nor unusual amounts of carbonized plant compression are always present. Animal burrows are present but not conspicuous in cores. Graded bedding in shale and siltstone is exceedingly rare in outcrops and cores. Silt-shale interlaminations with sharp con- tacts (fig. 11; pis. 7 and 8) rather than graded bedding, are typical. Such inter- laminations are well developed through- out the section and in many instances can be considered as evidence of proximity to a zone of high current velocity and turbu- lence; that is, they are proximal to sand bodies. Observation of outcrops indicates that the silty portion of these interlaminations are small, often isolated ripples of silt or 22 ILLINOIS STATE GEOLOGICAL SURVEY + Slumping and /or Compaction and/or Animal Borings Fig. 11, — Diagrammatic representation of the origin of disturbed bedding. fine sand that were migrating (commonly with markedly preferred transport direc- tions) across a clayey bottom. As such, these ripples provide a qualitative proof o£ Hjulstrom's law (Hjulstrom, 1939), which states that higher velocity is re- quired to erode clay-sized particles than to transport silt and fine sand. Directional Structures Another way of considering the sedi- mentary structures is based on their use- fulness for determining direction of current flow. In various sedimentary associations, cross-bedding, ripple marks, current lineation, current fluting, load casts, drag grooves, and slump structures all have been used successfully, either in combination or singly, for determining the local and /or regional direction of sediment transport. Depending broadly on the depositional environment, one or two of the directional structures will be dominant, and even though the others are present, the requirements of wide- spread occurrence, ease of measurement, and simplicity of interpretation will nearly always necessitate prime emphasis upon the dominant structures. This is precisely the condition prevailing in the Pennsylvanian sediments. Table 2 shows the abundance of the directional struc- tures of these sediments. Slump structures are not only less di- rectionally definitive, but in these rocks are far too rare to be useful. Although current fluting, drag grooves, directional load casts, and current lineation struc- tures are definitive, they are not suffi- ciently well developed to be useful. Problems of measurement and an appar- ent large local variability make the use of ripple marks undesirable although they are abundant. In contrast, cross-bedding, also abundant, is amenable to easy sam- pling. It has been studied previously in the Pennsylvanian rocks of the Eastern Interior coal basin (Olson and Potter, 1954; Potter and Siever, 1956, part I), and has significance for regional source- area determination. One of the primary objectives of our field work was to estimate the direction of transport of the post-Caseyville sedi- ments. This was done by measuring the dip direction of one foreset bed in two sedimentation units at each of 86 out- crops. For the method of sampling, its practical compromise with strictly ran- dom sampling, and the statistical treat- ment of the data, see Olson and Potter (1954) and Potter and Siever (1956, part I)- The measured cross-bedded outcrops of the area for the sediments above the Caseyville group are shown on figure 12 along with two directional distribution diagrams, one for the Caseyville group in southern Illinois, and the other for the post-Caseyville sandstones of the William- son County area. Table 3 gives the sta- tistical computations. The grand mean of two levels of sampling for the post- Caseyville sandstones of this vertical profile is 201° and 90 percent confidence limits are ±12 degrees. PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 23 Table 2. — Optimum Occurrence of Sedimentary Structures and Sandstone Types Sedimentary structure Optimum occurrence Sandstone type Orthoquartzites Subgraywackes Cross-bedding Ripple marks Thicker, coarse-grained "channel" sandstones Thin-bedded, slabby sandstones Abundant Abundant Abundant Abundant 3 Ripple scour Thicker, coarse-grained sandstones Common Common w Current lineation Thin-bedded, fine-grained sandstones Rare Rare a o 1 Q Current fluting and drag grooves Load casts Thin-bedded, fine-grained sandstones Thin-bedded sandstones or inter- bedded shales and sandstones Rare Very rare Rare Very rare Overturned cross-bedding Thicker, coarse-grained sandstones Common Common Cut-and-fill Thicker, "channel" sandstones Common Common Load casts Thin-bedded sandstones or inter- bedded shales and sandstones Common Common 3 o H Convoluted bedding Observed in outcrop and rare in cores. Soft sediment deformation not tied to any specific occurrence Rare Rare § o Disturbed bedding Best seen in siltstone-shale interlami- nations and caused by animal bor- ings, compaction and slumping Rare Rare 1 Graded bedding In some of the foresets of cross-beds and very rarely in some shales and fine siltstones Very rare Very rare Desiccation marks, sand- stone balls, puU-aparts, and ptygmatic folding Not observed Not observed Additional Significance That the silty and sandy sediments of this Pennsylvanian sequence were de- posited in shallow and turbulent waters is made clear by the data in table 2. The sedimentary structures of these rocks cor- respond roughly to those of fluvial, lit- toral, and shallow marine shelf deposits. The sedimentary structures of both beaches and sand dunes appear to be ab- sent, however. It is also evident from table 2 that turbidity currents played no significant role in the deposition of these sediments. Another conclusion to be drawn from our field study of the sedimentary struc- tures is that both the clean quartz sand- stones of the Caseyville (orthoquartzites) and the micaceous and argillaceous sand- stones above the New Burnside coals (subgraywackes) have essentially identical types and abundances of sedimentary structures. The lesser degree of sorting of the subgraywackes was not sufficient to produce major contrasts in sedimentary structures. PETROLOGY The ultimate objective of our petro- logic study was to isolate and assess, in terms of both mineralogy and texture, the effects of provenance and environ- ment. To attain this goal, however, it was necessary to take three preliminary steps. First, we wished to determine the 24 ILLINOIS STATE GEOLOGICAL SURVEY Post-Coseyville Sandstone Caseyville Sondstone Outcrop Average Fig. 12. — Cross-bedding and directional distribution of post-Caseyville sandstones (172 measurements in 86 outcrops) and Caseyville outcrop and directional distribution (204 measurements in 68 out- crops in southern Illinois). stratigraphic positions of the major min- eral associations. Second, we wished to characterize, both qualitatively and quan- titatively, the composition of these min- eral associations. Finally, we wished to assess the role that post-depositional diagenesis has played in producing pres- ent mineralogy and texture. Because of the dominance of elastics in the area studied, primary emphasis was placed on the sandstones and shales, with the less prevalent limestones receiving compara- tively little attention. The greatest number of samples was obtained from a 2140-foot diamond drill core in the NEi/4 NE14 NWI/4 sec. 12, T. 8 S., R. 3 E., Williamson County. This complete core, in the possession of the Survey since 1923, was partially sampled for sandstones by Raymond Siever in 1949 and subsequently by us for both sand- stones and shales. Outcrop samples of sandstones and shales supplemented those obtained from the core. The appendix gives the stratigraphic position and loca- tion of the samples. Sandstones Petrographic study included examina- tion of both thin sections and heavy PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 25 Table 3. — Variance Components for the Post- Caseyville Pennsylvanian Cross-bedding in and Near Williamson County, Illinois (Caseyville Group excluded) A. Summary computations 86 2 86 2 86 2 S S x« S ^x^n S i^x,y 34,678 7,843,132 7,779,961 86 outcrops, each with two observations B. Analysis of variance Degrees Sums of of Mean Expected squares freedom square value Outcrops (i) 778,292 85 9156.4 ai' + kaf Foresets(j) 63,171 86 734.5 af C. Components of variance Mean squares Differ- Com- Higher Lower ence Sample ponent Outcrops (i) 9156.4 734.5 8421.9 2 4210.9 Foresets(j) — 734.5 1 734.5 minerals as well as determination of the clay mineralogy of the sandstones' detrital matrix. Less emphasis was given to study of texture. Modal estimates of 36 thin sections were made by point counter using 200 counts per slide (table 4). A correspond- ing number of heavy mineral separations were made (table 5). The size fraction 0.062 to 0.500 millimeters was used for study of heavy minerals. On each slide 100 transparent, nonmicaceous grains were counted. The proportions of mica- ceous minerals and round tourmaline grains also were estimated from counts of 100 grains. Round tourmaline was de- fined as that whose roundness was greater than or equal to six-tenths on the Krum- bein (1941, p. 68) chart. Some samples were boiled in concentrated HCl for 30 to 60 seconds to remove iron oxides. Only apatite, discovered after about half the separations were made, was affected by the acid treatment. Figure 3 shows graphically plots of mineralogical compo- sition and tourmaline roundness versus stratigraphic position. Variation in min- eralogy between samples, especially for the heavy minerals, is largely the result of granular variation. Vertical variation in petrographic prop- erties closely coincides with the vertical variation in megascopic properties sum- marized in table 1. Megascopically and microscopically, the contrast between the Caseyville and the transition group is much more distinct than the contrast above and below the New Burnside coals. Undoubtedly the upper boundary of the transition zone is very gradational. We selected the New Burnside coals as the top of the transition zone because their stratigraphic position coincided with the position of greatest over-all lithologic contrast. If abundance of matrix clay and feld- spar are considered as the most geneti- cally significant classifying criteria, there are three petrographic groups: a lower group coinciding with the Caseyville, a transition group ranging from the Casey- ville to the New Burnside coals, and the argillaceous, micaceous sandstones above the New Burnside coals. CASEYVILLE SANDSTONES The average modal, detrital, and source-area components of the Caseyville sandstones in Williamson County are given in table 6. The average detrital composition of the 7 samples from Wil- liamson County is almost identical to that of the 40 samples (nearly all from outcrops) of the Caseyville and Mansfield sandstones from the Eastern Interior coal basin studied by Siever and Potter (1956). Plate 6 shows both the hand specimen and microscopic appearance of the Casey- ville sandstones. Mineralogically, these rocks consist mainly of quartz and secondary carbon- ate. Feldspar, matrix clay, and micaceous minerals are rare. In the absence of car- bonate, the quartz grains form a tightly welded interlocking mosaic. Authigenic 26 ILLINOIS STATE GEOLOGICAL SURVEY Table 4. — Modal Composition of Pennsylvanian Sandstones Sample Rock no. Quartz Clay Carbonate Feldspar Mica Chert fragments Misc. Subgraywacke group 330 ... . 64.0 23.0 0.0 5.5 2.0 0.0 4.0 1.5 301 . 57.0 26.0 0.0 8.0 3.5 0.5 2.0 3.0 300 . 36.0 12.0 35.0 3.0 2.5 1.0 9.0 1.5 10 . 56.5 25.5 2.0 3.0 6.5 0.0 2.0 4.5 290 . 64.5 19.0 4.5 2.5 4.0 0.0 2.0 3.5 11 . 63.5 18.5 5.5 5.0 2.5 0.5 2.5 2.0 12 . 39.0 4.5 50.0 3.0 1.5 0.5 0.5 1.0 328 . 59.0 22.5 0.0 8.5 4.5 1.5 1.0 3.5 329 . 63.5 17.5 11.0 3.0 2.0 1.0 0.0 2.0 13 . 55.0 4.0 30.0 4.5 2.5 0.5 2.0 1.5 291 . 55.0 21.0 0.0 5.0 10.5 0.0 4.5 4.0 14 . 47.0 22.0 23.0 1.0 4.0 0.0 2.0 1.0 379 . 74.5 16.0 0.0 5.0 1.5 0.0 2.5 0.5 292 . 66.0 24.5 0.0 4.0 2.0 0.5 2.5 0.5 293 - 56.0 4.5 29.0 3.0 1.5 0.0 4.5 1.5 16 . 54.0 13.0 21.0 1.5 6.5 0.0 1.0 3.0 294 . 67.0 25.5 0.0 1.5 2.0 1.0 2.5 0.5 303 . 64.0 21.0 0.5 3.0 5.0 0.5 2.0 4.0 299 . 56.0 21.5 5.0 6.0 3.0 0.0 7.0 1.5 Transitional group 17 ... . 65.0 15.5 1.5 8.0 2.5 2.0 5.5 0.0 18 73.5 17.0 0.0 3.0 0.5 0.0 4.0 2.0 39 57.5 0.5 35.5 2.0 1.0 0.0 0.0 3.5 20 88.5 5.0 0.0 4.5 1.0 0.5 0.5 0.0 21 81.0 10.5 2.0 2.0 1.0 0.0 2.5 1.0 38 66.5 10.5 18.0 1.5 0.0 0.5 2.0 1.0 22 76.5 9.5 9.5 1.0 2.5 0.0 1.0 0.0 23 89.0 7.5 1.0 0.0 1.0 0.0 1.0 0.5 24 89.0 9.0 0.5 0.0 0.0 1.0 0.0 0.5 25 47.5 0.0 49.5 0.0 0.0 1.5 0.0 1.5 Orthoquartzitic group 295 ... . 88.0 2.5 4.5 4.0 0.0 1.0 0.0 0.0 40 73.5 0.0 26.0 0.5 0.0 0.0 0.0 0.0 26 71.5 1.0 27.0 0.0 0.0 0.0 0.0 0.5 41 88.0 8.0 0.0 1.0 0.0 1.5 1.5 0.0 42 66.5 1.0 29.0 0.5 0.0 0.0 3.0 0.0 27 73.5 1.0 24.0 0.0 0.0 0.5 1.0 0.0 28 95.0 3.5 1.5 0.0 0.0 0.0 0.0 0.0 quartz overgrowths are common and in some slides may be the dominant cement. The secondary carbonate consists of both clear anhedral single crystals that may encompass portions of as many as three or four detrital quartz grains, and brown iron carbonate (siderite). The siderite is disseminated as small (20 to 40 microns), globular, anhedral crystals be- tween the larger detrital grains. In the less than 2-micron fraction obtained from these sandstones, siderite is much more abundant than calcite. In core samples, carbonate was found to form as much as EXPLANATION OF PLATE 1 A, — Cross-bedding exposed at the spillway of Crab Orchard Lake in the SE14 NW14 NW14 sec. 30, T. 9 S., R. 1 W., Jackson County, Illinois. B. — Asymmetrical current ripples in Tradewater sandstone obtained from a roadside ditch in NEi/4 NEi/4 SEi/4 sec. 30, T. 10 S., R. 3 E., Williamson County. Illinois State Geological Survey R. I. 204, Plate 1 ji..^«.».i H^ B Potter and Glass, Pennsylvanian Sedimentation Illinois State Geological Survey R. I. 204, Plate 2 Potter and Glass, Pennsylvanian Sedimentation PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 27 Table 5. — Heavy Minerals, Tourmaline Roundness, and Micas in Pennsylvanian Sandstones (0.062 to 0.5 mm.) Sample no. Heavy minerals Tourmaline Micas (percent) roundness ^number ) (percent) .S S u 3 (U < (U ri < PQ T3 C C .2 w 'V, U 8 39 58 3 100 100 15 57 3 13 6 6 p* 100 1 3 45 55 22 2 19 1 1 99 4 6 30 25 75 p 8 92 11 41 48 33 67 p 100 5 38 57 61 35 4 p 100 5 13 82 55 35 1 9 1 99 6 24 70 52 46 2 p 100 1 99 2 81 4 13 p 1 99 21 3 24 70 1 2 2 p 100 23 77 6 92 1 p 2 98 1 24 75 63 34 3 p 1 99 37 64 40 55 1 4 1 99 16 5 93 2 p p 2 98 4 1 41 92 8 3 97 3 49 47 63 31 4 2 p 100 6 46 48 3 96 1 p 100 2 52 48 49 3 p 2 98 1 1 98 64 36 p 100 10 64 26 51 43 6 29 71 7 93 71 26 1 1 1 p 100 24 76 53 43 3 1 2 98 9 91 52 42 4 2 3 97 14 86 73 26 1 p 17 83 11 62 27 85 8 3 4 19 81 5 38 58 77 21 2 p p 40 60 1 34 93 4 2 1 19 81 16 71 19 4 6 19 81 4 96 10 62 3 24 1 p 33 67 . — 63 35 2 44 56 1 17 54 44 2 31 69 2 69 23 2 6 48 52 2 18 87 10 3 27 73 1 7 51 45 4 33 67 — — — 68 29 2 1 31 69 1 31 330 301 300 10 290 11 12 328 329 13 291 14 379 292 293 16 294 303 299 18 39 20 21 38 22 23 24 25 295 40 26 41 42 27 28 * P indicates mineral is present. 30 percent o£ the sample. Where carbon- ate is present in abundance, replacement of quartz generally is extensive. Barite is a minor cementing agent. Aggregates of small (2 to 10 microns) pseudo-hexagonal kaolinite crystals are present. Detrital micas are present but are not abundant in either hand speci- men, thin section, or heavy-mineral slide. Counts in heavy-mineral slides show mus- covite to be much more abundant than either chlorite or biotite (fig. 13). The transparent heavy minerals are domi- nantly zircon and tourmaline, with rutile, anatase (both detrital and authigenic), and collophane as minor components. As shown by the almost complete dominance of quartz, zircon, tourmaline, and musco- EXPLANATION OF PLATE 2 A. — Symmetrical oscillation ripple marks in fine-grained DeKoven sandstone, exposed in the Will Scarlet strip mine approximately 3 miles northwest of Stonefort, Saline County, Illinois. B. — Interference ripple marks exposed in lower Tradewater sandstone in a creek bed in northwestern Johnson County, Illinois. 28 ILLINOIS STATE GEOLOGICAL SURVEY Table 6. — Average Sandstone Composition Rock type Quartz Detrital matrix Carbonate Feldspar Mica Chert Rock fragments Misc. No. of samples A. Modal analyses Subgraywackes Transition group Orthoquartzites 57.8 73.4 79.4 17.8 8.5 2.4 11.4 4.0 3.6 11.7 2.2 1.0 16.0 0.9 0.0 B. Detrital components 0.3 0.4 0.6 2.9 1.9 0.7 2.2 1.0 0.1 19 10 7 Subgraywackes Transition group Orthoquartzites 65.3 83.0 94.5 20.1 9.7 2.9 — 4.5 4.1 — 2.5 1.1 — 1.0 0.0 C. Source area components 0.3 0.4 0.8 3.2 2.1 0.8 2.5 1.1 0.1 19 10 7 Subgraywackes Transition group Orthoquartzites 81.6 92.0 97.3 — — 5.7 5.1 — 2.8 1.2 — 1.1 0.0 0.4 0.3 0.7 4.1 2.4 0.9 3.1 1.3 0.1 19 10 7 vite among the detrital minerals, the Caseyville rocks are mineralogically very mature. Caseyville sandstones have a number of interesting textural features (Biggs and Lamar, 1955, table 4). The conglomeratic quartz granules and pebbles, although conspicuous to the eye, affect the size dis- tribution very little. Not only were quartz granules and pebbles present in only ap- proximately one - fourth of Biggs and Lamar's (1955, table 4) samples, but where present they generally constituted less than one percent of the entire sedi- ment. Although median sizes range from 0.096 mm. (very rare) to as large as 0.690 mm. (very rare), values between 0.150 mm. and 0.350 mm. are typical. The typical Caseyville sandstones are thus medium- to fine-grained. We used the data of Biggs and Lamar (1955, table 4) to compute phi sorting coefficients (Inman, 1952) for 17 samples with median sizes between 0.19 to 0.38 mm. (table 7). For these samples, phi sorting coefficients range from 0.944 to 0.329 and average 0.583, indicating that the average Caseyville sandstone is well sorted. Because of authigenesis and the effects of pressure welding, roundness estimates based on either loose or thin-sectioned quartz grains are not satisfactory. Round- ness of tourmaline determined from heavy-mineral slides provides such an es- timate. The proportion of round tourma- line (0.6 or greater on the Krumbein Fig. 13. — Contrasting abundances of sand-fraction muscovite (ruled), chlorite (stippled), and bio- tite (black) in Pennsylvanian sandstones. Num- ber of particles counted shown in parentheses. EXPLANATION OF PLATE 3 A. — Probable antidune bedding exposed in a small creek bed in NW14 NE14 NEi/^ sec. 6, T. 10 S., R. 1 W., Jackson County, Illinois. B. — Current fluting and drag grooves shown on underside of thin-bedded and fine-grained McLeans- boro (Trivoli?) sandstone from northeastern Williamson County, Illinois. Illinois State Geological Survey R. I. 204, Plate 3 Potter and Glass, Pennsylvanian Sedimentation Illinois State Geological Survey R. I. 204, Plate 4 ^^^. -t ■ f _^-«'. B Potter and Glass, Pennsylvanian Sedimentation PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 29 chart, 1941, p. 68) was determined for the size range 0.062 to 0.5 mm. because 1) an abrasion index for the entire sediment rather than a restricted size range was desired, and 2) good hydraulic sorting made choice of a single size grade difficult. Siever and Potter (1956) showed that in the basal Pennsylvanian sandstones of the north-central states there was no as- sociation between tourmaline size and roundness in the size range 0.062 to 0.5 mm. That is, increase in size was not ac- companied by increase in roundness com- parable to that expected if all the grains had had the same abrasion history. This conclusion is confirmed in a different manner by the three cumulative curves of figure 14, which show that roundness does not depend on size. The coarser grained Pennsylvanian subgray- wacke from above the New Burnside coal contains only 2 percent round grains, but the finer grained (Pennsylvanian) ortho- quartzite and the St. Peter (Ordovician) sandstones have 42 to 97 percent round grains respectively. In these sediments, therefore, tourmaline roundness is almost entirely a function of previous abrasion history rather than an expression of the universal dependence of roundness on size. Approximately 35 percent of the tourmaline grains of Caseyville sandstone are round. TRANSITION SANDSTONES The sandstones of the transition group average, on a carbonate-free basis (table 6), 83 percent quartz and 9.7 percent clay matrix. Less roundness and increased clay matrix, feldspar, micas, and rock fragments (mostly locally derived) show these sandstones to be appreciably less mature than those of the Caseyville. Throughout much of this zone the Table 7. — Comparative Sorting (0) for Pennsyl- vanian SUBGRAYWACKES AND OrTHOQUARTZITES and THE St. Peter (Ordovician) Sanl stone (1 phi unit, 0.38 to 0.19 mm) Penns ylvanian St san Peter Subgraywackes Orthoq uartzites^ dstone^ .822 .641 .514 .930 .527 .628 .660 .421 .758 .509 .916 .629 .687 .699 .522 .842 .526 .801 .894 .329 .680 .973 .944 .405 .819 .379 .636 .763 .475 .502 .963 .934 .598 .851 .692 .383 .575 .424 .475 .588 .655 .408 .493 .463 .427 .531 .662 .545 .783 .649 .487 .631 .679 .429 Average Ti = .769 X2 = .583 X3 = .581 1 Data from Biggs and Lamar (1955, table 4). 2 Data from Lamar C1927, table 10) and Giles (1930. table 5). quartz grains appear to be less well rounded than those of the Caseyville. The feldspars consist of both fresh and weathered microcline, orthoclase, and plagioclase. Unlike the sandstones of the Caseyville group, feldspar was positively identified in the less than 2-micron frac- tion of all but one of the sandstones. Al- though there is little increase in biotite, chlorite appears to be somewhat more abundant (fig. 13). A companion in- crease in immature heavy minerals does not occur. Zircon and tourmaline remain the dominant species and garnet, anatase. EXPLANATION OF PLATE 4 A. — Current lineation in thin-bedded and fine-grained Caseyville sandstone exposed in creek bed in NEV4 NWi/4 NW14 sec. 32, T. 11 S., R. 5 E., Pope County, Illinois. Current lineation persists through a series of laminations. B. — Underside of basal Caseyville orthoquartzitic sandstone showing unusual development of oriented load casts. Specimen obtained above the Kinkaid limestone from along the north-south road in NEi/4 NW14 sec. 31, T. 11 S., R. 2 E., Johnson County, Illinois, about s/g of a mile north of the Cedar Grove church. 30 ILLINOIS STATE GEOLOGICAL SURVEY .062 .088 .125 .177 .250 MILLIMETERS .354 .500 .707 Fig. 14. — Cumulative curves of counts of 100 tourmaline long axes and per- centage of round tourmaline grains. Note that the finer-grained sandstones have more round grains. and collophane are all in minor abun- dance. Apatite is present, however, and its typical form is that of subrounded, broken, and fractured grains. Because apatite is rather brittle, disaggregation may have produced the fractured grains. The opaque heavy minerals include py- rite (generally the most abundant), mag- netite, and ilmenite. The sandstones of the transition group have both precipitated and detrital ma- trix cements. Thin sections show calcite and siderite to be the dominant mineral cements, with siderite probably more abundant than calcite. In the less than 2- micron fraction, siderite is also the more abundant. Siderite is especially promi- nent in the sandstones of the lower Trade- water group — the Grindstaff, Delwood, and Murray Bluff. It typically forms small (30 to 40 microns) anhedral crys- tals that partially fill the space between the framework fraction. The siderite ce- ment can be so abundant that some core specimens have a dull, brownish-red cast. In outcrop, leaching and oxidation of the siderite impart a prominent reddish, fer- ruginous appearance to these sandstones. The detrital matrix cement of the transition group sandstones differs in abundance, but not in kind, from that of the higher sandstones. Its properties are essentially those described in detail for the higher sandstones. The sandstones of the transition group are texturally somewhat less well sorted than those of the Caseyville. Median sizes are broadly similar to those of the non- conglomeratic Caseyville sandstones. In terms of tourmaline abrasion, the grains are more angular (fig. 3); only some 15 percent of the tourmalines are well rounded. Under the microscope as well as in hand specimen, the sandstones of the transition zone are more akin to those above the New Burnside coals than to the Caseyville sandstones. SANDSTONES ABOVE THE NEW BURNSIDE COAL Sandstones above the New Burnside coals form a very homogeneous group. Greater clay matrix and more feldspar, mica, and rock fragments indicate that these sands are the most immature of the PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 31 STRATIGRAPHIC SECTION FELDSPAR PRECIPITATED CEMENTS FEET c c to o o < 2 2 i E 2 O ll_ C ^ 3 V ■/: O 3 OJ C (U o _9 t^ s ^ ^ (U (L) rt ^ O CJ iH Jq ''^ 5 (-1 o bX)"Jj c/2 bC.bi O 'a V-^ ^ fcfi O 3 OJ ^ t3 3 S t^ (U S -S3 PH C/2 C^ OS a Co: ~3 ilj O oCn -y r- y '-I rrt *^ £ J:J C OiS' S c en U *-> " (U lU O C • t- > C O g .2 J^ .3 (U CO OJ .3 Dh CO £ "bb .£-£^ o 'n; OJ OJ " '^ £ S 3 <^ fc o OJ bc C^ •- 3 3J2 a- (N -^ (U<-^ U o 3 >> ?n fe O-pj r-!\ bfl -^J rt ^ pTS •n "* c 55 -C o o,^ o.S-n O '^ (J bC • _3_>s CLh Ph 3 '53 ^ > y £ ^ . 3 N N JZT '^ (U £ i2 >s (U "^ £ c^ .3! 0-5 1^ c/l -5 rt £ S ^ H3 ,^^ ^ £ rT c«.t: 3 C +j S !^ c/5 3 3 >;- S ^ 3 'S 3 ^ ■^ ^ 2 3 CU.B CO -o _ > ^§ ? CO (U (J ^ ^-t 00 .-H W re 3 .5P 2 "bb o OJ rt O 3 I-, OJ (u ::3 On 1 ^ ^ 3 r3 4-' .-3S t:-^ 3 t: • - 3 O IJ 3 O 3 d, OJ (U bO Oh o O 2 rt rt . 4-p c JJ_Q 3_ ^ OS *3 bb bC •^ J3 bC Ti c/5 "3 ti 3 o £ - C *:i -Q O 00 r-( i; -t-i si -^ C rt c ^-5 t P 3 ^- C Q o a > u 53 o ti >— I C-3 OJ C o . O ■^^ c--^ „,^ C/3 ji: 5.i^ o 1 13 *-! C C/5 OJ (U oj 5 > a.S fe: — O _ -^ rt t? c oj c; >. c c rt i-i .rt '-:? o i - '- 7' ' < _x- M I o 1 3 O 60 Q Z 3 O ~ V > ' < T _^ \ O - 1 '- -T- / N T !■ H 1 to cr LU 1 q: 40 ~ e-ii:> ■ I £ 20 - ^0 , - M O - - ■ Q. ■ 1 '-:":: °-:: 1 In TTtI Fig. 18. — Black shows percentage of round tourmaline grains (0.062 to 0.5 mm.) of the Pennsylvanian subgraywackes and orthoquartz- ites and the Ordovician St. Peter sandstone. Number of grains counted shown in parentheses. indicate that at least some of the matrix clay of the subgraywacke sandstones is unrelated to original deposition. More generally, a well sorted, and even a well rounded, sand fraction can be associated with appreciable clay matrix. Hence, de- pending on local sorting, there can be oc- casional textural "regressions" in the over-all maturity sequence. ENVIRONMENT OF DEPOSITION By depositional environment we mean a site of deposition such as an offshore bar, an alluvial fan, a tidal flat, or similar feature where the physical, chemical, and geologic processes associated with deposi- tion have produced distinctive sedimen- tary attributes prior to final burial of the sediments. A modern depositional en- vironment is thus simply a geographic place where physical processes presum- ably produce distinctive sedimentary at- tributes. The recognition of these modern environments in ancient sediments seems to involve two distinct steps. The first step is an integration of the sedimentary attributes in the ancient sediments to obtain a qualitative (and less commonly quantitative) picture of the major physical, chemical, and biologi- cal processes that affected the sediments at the site of deposition. The second step is the identification of an equivalent modern place (tidal flat, shallow marine shelf, or similar feature) where compar- able attributes exist today. Success appears to depend on the kind and size of geographic place. That is, the attributes of the modern sediments of a large delta or a shallow marine shelf are likely to be more easily recognized in an- cient sediments than are the attributes of the geographic subdivisions within them. The second step is the difficult one be- cause, depending upon the kind and size of the geographic unit, these physical, chemical, and biological processes are not always uniquely tied to a single modern geographic place. This is largely because the sedimentary processes in many mod- ern geographic environments differ more in degree than in kind. Thus, in many in- stances, the worker in ancient sediments may be able to make only a qualitative reconstruction of the physical processes and to associate these processes with large equivalents such as shelves, basins, and troughs, rather than with small-scale modern equivalents. Environment The major environmental contrasts in the Pennsylvanian sediments of the Wil- liamson County area are those above and below the New Burnside coals (table 1). Below the New Burnside coals, sand- stones are dominant, marine fossils are rare, limestones have not been found, and coal beds are thin and of limited lateral persistence. Rapid sedimentation rates as well as rapidly shifting loci of sand depo- sition are inferred. As demonstrated by cross-bedding, transport direction of the sandstones was to the southwest. Initially orthoquartzites in the Casey ville, the sands became more argillaceous and f eld- spathic, so that in the Lower Tradewater the sands have properties intermediate to those of the orthoquartzites below and the subgraywackes above. The section above the New Burnside coals is characterized by a much greater proportion of sediments of known marine origin (limestones and shales), by thin lithologic units traceable over wide areas PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 49 (often several states), by the notable dominance of shale compared to sand- stone, by cyclical sedimentation, and by better developed coal beds. Both in out- crop and subsurface many of the asso- ciated sandstones fill prominent erosional channels. Changes in relative base level were the immediate cause of these chan- nels as well as the probable cause of cyclical sedimentation. The sandstones of this facies average some 16 percent (subsurface only) detri- tal matrix. Because the subgraywacke sandstones are basin wide, local deposi- tional factors, such as proximity to a large delta, do not appear to be a satis- factory explanation for the proportion of clay matrix. Because of both basin-wide extent and association with change in kind as well as proportion of lithologies, the upward increase in clay matrix of the sandstones appears to have a direct tec- tonic explanation — an accelerating sub- sidence of the basin of deposition. A more negative basin is the probable cause of the wider lateral continuity of many of the lithologic units and the greater pro- portion of marine sediments. The sedi- mentary structures of these subgraywacke sandstones, however, differ little if at all from those of the sandstones below the New Burnside coals. Graded bedding and flow marks are very rare. Hence, even though the subgraywacke proportion of detrital matrix reflects poorer sorting at the site of deposition, these sandstones were deposited in shallow water. As in the underlying sandstones, the dominance of the nondirectional over directional load casts indicates that the regional de- positional slope was small. That there was, however, a definitely preferred di- rection of sediment transport is shown by cross-bedding direction. Throughout the 1800 feet of Pennsylvanian sediments of this area, the modal transport direction was to the southwest. A coupled low-lying coastal plain and marginal shallow shelf appears to provide the best large-scale model of the environ- ment of deposition. Siever (1953, p. 215) suggested the existence of a somewhat similar physiographic couple during upper Chester sedimentation. On such a physio- graphic couple, oscillations of strand line would be far reaching, near-shore marine, littoral, tidal flat, and nonmarine sedi- ments all could occur, opportunities for coal bed formation would be plentiful, and the development of erosional chan- nels preceding sandstone deposition would be commonplace. This physio- graphic couple appears to have persisted throughout the entire period of Pennsyl- vanian deposition. The lithologic contrasts above and be- low the New Burnside coals are the probable result of differential rates of subsidence upon such a physiographic couple. For example, available evidence (as quoted in Potter and Siever, 1956, part I) indicates that the sediments of the Caseyville group are a transgressive facies (sediment transport from northeast to southwest) in which by-passing played a significant role. The uniformity of the Caseyville-Mansfield flow pattern of the Eastern Interior coal basin (fig. 17) indi- cates that the sediments of this pro- grading physiographic couple had uni- form depositional strike over wide areas. An initial slow rate of subsidence pro- duced the well sorted sands of the Caseyville group. As time passed, the transport direction in the Williamson County area continued to be from north- east to southwest, but the Eastern Interior coal basin became more negative (sub- graywacke sandstones) so that more sedi- ments were entrapped and shale, marine sediments, and coal swamps became more significant. The decreasing competence of the sediment transport across this more negative physiographic couple is doubt- less the reason for the dominance of shale over sandstone above the New Burnside coals. Sediment transport across a low lying coastal-plain — marginal-shelf that subsided at an accelerating rate with con- sequent change in lithologic proportions and sandstone type thus appears to have been the major feature of the environ- ment of deposition. 50 ILLINOIS STATE GEOLOGICAL SURVEY If this interpretation is right, the sedi- mentary structures o£ the elastics should be similar to those of modern coastal- plain — shallow-shelf environments. Cer- tainly cross-bedding, washouts with abun- dant locally derived conglomerates, ripple marks, and abundant drifted plant re- mains (in humid climates) are character- istic of modern coastal-plain — shallow- shelf elastics and are essentially identical to those of the Pennsylvanian elastics. The similarity extends to some of the small-scale, minor, internal sedimentary structures. Plates 7 and 8 permit a com- parison of the fine sand-silt-shale inter- laminations of Pennsylvanian sediments with those of the modern tidal flats of the Wadden Sea in the Netherlands, and with those of the near-shore elastics of the Texas Gulf Coast. The similarity points to an identity of small-scale processes of clastic deposition between this ancient coal basin and the modern Wadden Sea and Gulf Coast sediments. Assuming the coastal-plain — marginal- shelf interpretation is correct, we might also expect to find some evidence of beach deposits, strand-line dunes, and offshore bars such as those found along the Texas Gulf Coast. In none of the sandstones has aeolian cross-bedding been observed. Des- sication marks are very rare. This evi- dence, combined with an abundance of drifted plant remains and coal swamps implies a climate with abundant vegeta- tion closely rimming the strand line. Lit- toral conditions probably were compar- able to those of many of the modern coastal mangrove swamps of tropical regions. Although their occasional marine fos- sils and close association with marine sediments indicate that significant pro- portions of the sandstones above the New Burnside coals may be of marine origin, neither subsurface (lithologic patterns) nor outcrop (textures and structures) evi- dence suggests that beach deposits or off- shore bars were prominent. The poor sorting and roundness of the sandstones contrast sharply with those of many mod- ern beach deposits. Although the Casey- ville sands are well sorted, the structures of the Caseyville sandstone are clearly not those of modern beaches. The apparent absence of prominent beach deposits and offshore bars thus suggests that strand- line abrasion and transport were not ex- tensive. This conclusion implies that the typical Pennsylvanian marine submer- gence of this low-lying coastal-plain — shallow-marine-shelf was not accompa- nied by strong shoreline current processes. What contributions to environmental knowledge can be made by the clay min- erals in these sediments? Murray (1953) investigated the clay mineralogy of some of the Tradewater, Carbondale, and McLeansboro sediments of the Eastern Interior coal basin and concluded that the presumed marine vs. nonmarine (Weller, 1931) portions of the cyclothem had contrasting clay mineral compositions. Recognizing that the clay mineral com- position of Pennsylvanian sandstones in both core and outcrop has been appre- ciably altered by post-depositional dia- genesis, and that even shale can differ in composition from outcrop to subsurface, we investigated the clay mineralogy of the Trivoli cyclothem (all core samples) in detail. Figure 19 show^s its variation in clay mineralogy. Segregation of the sand- stone samples markedly decreases kaolin- ite abundance below the coal bed. The average clay mineral abundance (under- clays excluded) above and below the Trivoli coal is shown in table 13 (A). Al- though mixed-lattice and chloritic mate- rials are closely comparable for the two groups, there is variation in kaolinite and mica. In comparison to the clay mineral contrasts induced by post-depositional diagenesis in the sandstones, however, the kaolinite-mica variation is minor. How- ever, Murray (1953, p. 59) also found more kaolinite and chlorite and less mica below rather than above the coal (table 13 (B)). More recently. Glass (1958) has also observed different clay mineral com- positions in the shales above and below coal beds. Thus when inheritance and permeability effects are segregated, there appear to be some consistent differences PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 51 SAMPLE PARTS IN TEN 4 5 200 Kaolinite TRIVOLI SANDSTONES Nos. 10, 1 1, and 290 ^ llite Mixed lattice Chlorite Fig. 19. — Clay mineral composition (subsurface samples only) of Trivoli cyclothem. Sample numbers identified in Appendix. in clay composition above and below the coal beds of Pennsylvanian cyclothems. Factors other than the possible differ- ence between marine and nonmarine sedimentation, however, could be respon- sible for these contrasts. For example, even though we have eliminated the more permeable sandstones from the compari- son, the shales below coals tend to be more silty and sandy than those above. The possibility that contrasts in clay- mineral permeability extend even to silty and sandy shales should be recognized. The effect of the acid environment of coal swamps on the underlying sediments (especially underclays) is another possible reason for contrasts in clay mineral com- position above and below coal beds. Another way to evaluate the environ- ment of deposition is to contrast the clay mineral composition of the limestones with that of their associated subgraywacke shales. This would evaluate the effect of deposition and/or post-depositional dia- genesis on clay mineral composition in a more alkaline environment. The lime- stones as a group can be quite variable in mixed-lattice and kaolinite content (as shown by table 8 (C) ). These data show that some of the limestones are similar in clay mineralogy to the typical subgray- wacke shales and that others differ markedly. This suggests that future studies of limestones might be rewarding for evaluating the role of clay-mineral diagenesis in alkaline environments. Although the underclays may be a notable exception, the above interpreta- tions emphasize the difficulties of inter- preting the relationship between deposi- tional environment and clay minerals. That there is some difference in sub- surface clay-mineral composition between the subgraywacke and orthoquartzite shale facies, however, is shown in table 13 (C). Although mica is the dominant clay mineral of both, the subgraywacke shales average 2.4 and the orthoquartzite 52 ILLINOIS STATE GEOLOGICAL SURVEY Tabi 13. — Environmental Aspects of Clay Mineralogy Kao- linite Mixed No. of Mica lattice Chlorite samples A. Trivoli cyclothem Above coal 1.1 5.1 1.4 2.4 5 Eelowcoal 2.0 4.0 1.6 2.4 7 E. Composite contrast in subgraywacke facies (Murray, 1953) Above coal 1.4 7.4 — * Eelowcoal 2.1 6.3 — * 1.2 1.6 C. Orthoquartzitic versus subgraywacke facies shales Ortho- quartzitic facies 1.1 6.1 1.4 1.4 17 Subgray- wacke facies 1.5 4.6 1.5 2.4 38 * Included with mica. shales 1.4 parts chlorite. Conversely, mica is more abundant in the orthoquartzitic shales than in those of the subgraywacke. Because of the subgraywackes' greater proportion of marine sediments, this con- trast could be due to environmental dif- ferences. However, even though chlorite is somewhat more abundant in the sub- graywackes, mica is less so and thus not all the differences are in the direction of the formation of illite by marine dia- genesis. Inheritance differences between the shales of orthoquartzitic and the sub- graywacke facies could be capable of accounting for these contrasts. Obviously, the environmental inter- pretation of clay mineral composition in these sediments is not an easy task. What conclusions can be drawn from the diffi- culty of deducing the environment of deposition from the clay mineralogy of these sediments? The close integration of clay mineral study with stratigraphy and sedimentary petrology maximized the likelihood of separating the effects of post-depositional diagenesis, depositional environment, and source-area contribution (inheritance) on clay mineral composition. This integra- tion was very successful in evaluating the effect of post-depositional diagenesis on both shales and sandstones. It was not very successful, however, in separating the effects of inheritance from those of depositional environment. Others (Mil- lot, 1953, p. 84; Grim and Bradley, 1955, p. 473) have suggested that the length of time the clay mineral remains at the depositional environment is an important factor. Probably because of rapid sedi- mentation, deposition in the near-shore marine, littoral, and nonmarine environ- ments had minor effect on clay mineral composition. Although not conclusive, the available evidence suggests that in these sediments clay mineral composition is more dependent on source-area contri- bution than on depositional environment (with underclays as a notable exception). A presumed rapid rate of sedimentation is believed to be responsible for the greater source-area role. With slower sedi- mentation rates, the role of depositional environment might be more significant. Thus one of the major conclusions of this study is to establish more firmly the view that because clay minerals are sub- ject to quasireversible processes, they are a hybrid of stable source-area detritals on one hand and true chemical precipitates on the other. The evidence presented by this report thus suggests that in ancient sedimentation systems clay minerals are both allogenic and authigenic. They are predominantly allogenic where inherit- ance is dominant over either depositional environment or post-depositional dia- genesis. Conversely, clay minerals are predominantly authigenic where deposi- tional environment and/or post-deposi- tional diagenesis are dominant. TECTONICS AND CLIMATE Provenance reconstruction indicates that as Pennsylvanian sedimentation in the Eastern Interior coal basin proceeded, progressively more and more crystalline rocks of either igneous or metamorphic origin contributed detritus. Progressive PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 53 uplift and erosion of a crystalline core is inferred. That such progressive uplift of the source area was coupled with more rapid subsidence in the area of deposition is demonstrated by the correlation (in the transition and subgraywacke sand- stones) between increasing clay matrix and more immature detrital (feldspar, chlorite, biotite, garnet, apatite, and poorly rounded tourmaline) components. Thus, throughout much of the eastern United States and Canada, Middle and Late Pennsylvanian time was marked by progressive differentiation between nega- tive basins and positive source areas. This tectonic differentiation was no doubt accompanied by progressive in- crease in orographic relief. Increase in continental orographic relief has been considered an essential factor in the pro- gressive late Tertiary cooling that led to Pleistocene glaciation (Flint, 1947, p. 514-516; Emiliani, 1954). It seems prob- able that an increase in Middle and Late Pennsylvanian orographic relief would have induced a similar climatic change. Extending this viewpoint, the subgray- wacke sandstones above the New Burn- side coals may have been the early fore- runners of progressively more intense Pennsylvanian tectonic and orographic contrasts that culminated in world-wide Permian climatic contrasts comparable to those of the present day. SUMMARY In the Eastern Interior coal basin a long period of erosion followed the termi- nation of Mississippian sedimentation, producing widespread regional trunca- tion. Rejuvenation at the close of the interval caused entrenchment of a domi- nantly southwestward-oriented system of stream channels that flowed toward the area of greatest subsidence. Companion rejuvenation of the source area made available mineralogically mature sedi- ments that contained abundant quartz conglomerates. Approximately one-third of these source sediments had had long histories of abrasion. Sediment transport was dominantly from the northeast to the southwest, with progressive up-dip depo- sition. The Caseyville facies was deposited on a low lying coastal-plain — marginal- shelf. Well sorted, shallow-water ortho- quartzitic sandstones accumulated on this physiographic couple. Although both ma- rine and nonmarine sediments occurred, the dominance of sandstones (greater transport competence on a steeper re- gional slope?) minimized the likelihood of fossiliferous marine sediments. In southern Illinois the Grindstaff sandstone marks the beginning of a greater rate of subsidence of the physio- graphic couple as well as the appearance of some feldspathic rocks in the source area. The source of the well rounded quartz pebbles was almost completely eliminated by this time. As feldspar, bio- tite, and chlorite increased gradually the proportion of well rounded source sedi- ments decreased sharply. Although the site of deposition was becoming more negative throughout the Grindstaff — New Burnside coal interval, both lithologic pro- portions and general lateral persistence of major lithologies remained broadly simi- lar to those of the Caseyville sediments. Clastic sedimentation of mixed marine and nonmarine origin was dominant. The first significant lithologic expression of the accelerating subsidence of the physiographic couple is found above the New Burnside coals. Above the New Burnside coals this greater negative character resulted in a much greater proportion of rocks of known marine origin, well developed cyclical sedimentation, a much smaller proportion of sandstone (a lower regional slope?), and a greater lateral continuity in nearly all the lithologic units. By this time source-area erosion had exposed significant metamorphic and /or igneous rocks, so that feldspar, biotite, chlorite, garnet, and apatite, and possibly other heavy minerals, were in transport to and across the physiographic couple. By now the proportion of source rocks with long histories of transportation had become negligible. Cross-bedding direc- 54 ILLINOIS STATE GEOLOGICAL SURVEY tion shows that in southern Illinois the regional slope of the coal basin persisted to the southwest from as early as the re- juvenation and entrenchment of the stream channels of the Mississippian- Pennsylvanian unconformity through the Upper Pennsylvanian at least to the time of deposition of the Mt. Carmel sandstone. Thus the Pennsylvanian sediments along this southern portion of the East- ern Interior coal basin accumulated on a southwestward-dipping, low lying coastal- plain — shallow -marginal -shelf that be- came progressively more negative and probably more gently dipping with pas- sage of time. This physiographic couple received more immature detritus as source-area erosion progressively unroofed metamorphic and/or igneous rocks and earlier sediment sources were overlapped. Increased tectonic differentiation between negative basins and positive source areas doubtlessly heightened orographic con- trasts over significant portions of the con- tinent and may have induced climatic changes in the Upper Pennsylvanian. The above interpretations confirm the importance of petrology and sedimentary structures in obtaining source-area infor- mation, and also point out the limitations of both sand- or clay-fraction mineralogy in making environmental inferences. The present study reaffirms the importance of local and regional patterns of lithologic variation, fossil content, and sedimentary structures for obtaining knowledge of the environment of deposition. What does the above summary contrib- ute to our secondary objective — the examination of the interrelationships be- tween gross lithologic variation, sedi- mentary structures, petrology, and clay mineralogy in an intracratonic coal basin? The data of this study emphasize the interdependence of both lithologic types and proportions to sandstone petrology. A greater proportion of shale and marine sediments is associated with the sub- graywacke sandstones. An accelerating rate of basin subsidence provides a com- mon explanation. In contrast, this in- ferred accelerating subsidence was accom- panied by only a comparatively minor change in clay mineralogy and no signifi- cant change in mechanism of sand transport. PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 55 APPENDIX LOCATION OF SAMPLES A. Shales Sample Depth number Location ft. in. 500 Madison Coal Company Hole No. 25 NEM NEM NWM sec. 12, T. 8 S., R. 3 E., Williamson County, Illinois .... 54 6 501 Shale in sandstone (300) from Old Ben Hole No. 51, SW3^ SE^ SWM sec. 29, T. 7 S., R. 4 E., Franklin County, Illinois 502 Madison Coal Company Hole No. 25 503 Madison Coal Company Hole No. 25 504 Madison Coal Company Hole No. 25 505 Madison Coal Company Hole No. 25 506 Madison Coal Company Hole No. 25 507 Madison Coal Company Hole No. 25 508 Madison Coal Company Hole No. 25 509 Madison Coal Company Hole No. 25 510 Madison Coal Company Hole No. 25 511 Madison Coal Company Hole No. 25 512 Madison Coal Company Hole No. 25 513 Madison Coal Company Hole No. 25 514 Madison Coal Company Hole No. 25 515 Madison Coal Company Hole No. 25 ... 516 Madison Coal Company Hole No. 25 517 Madison Coal Company Hole No. 25 ....... 518 Madison Coal Company Hole No. 25 519 Madison Coal Company Hole No. 25 520 Madison Coal Company Hole No. 25 521 Madison Coal Company Hole No. 25 522 Madison Coal Company Hole No. 25 523 Madison Coal Company Hole No. 25 524 Madison Coal Company Hole No. 25 . 525 Shale from sandstone exposed in road cut in NE3^ NE3^ NE3^ sec. 4, T. 9 S., R. 5 E., Saline County, Illinois 526 Madison Coal Company Hole No. 25 527 Madison Coal Company Hole No. 25 528 Madison Coal Company Hole No. 25 529 Madison Coal Company Hole No. 25 530 Madison Coal Company Hole No. 25 531 Madison Coal Company Hole No. 25 532 Madison Coal Company Hole No. 25 534 Madison Coal Company Hole No. 25 535 Madison Coal Company Hole No. 25 536 Madison Coal Company Hole No. 25 537 Madison Coal Company Hole No. 25 539 Madison Coal Company Hole No. 25 540 Madison Coal Company Hole No. 25 541 Madison Coal Company Hole No. 25 542 Madison Coal Company Hole No. 25 . 543 Madison Coal Company Hole No. 25 545 Madison Coal Company Hole No. 25 546 Madison Coal Company Hole No. 25 547 Madison Coal Company Hole No. 25 548 Clay lens in Palzo sandstone exposed in strip mine in SWj^ NE34 NE^^ sec. 20, T. 10 S., R. 5 E., Saline County, Illinois 549 Clay lens in Davis sandstone exposed in New York Central Railroad cut in NEj^ NW34 NE3^ sec. 30, T. 10 S., R. 5 E., Saline County, Illinois 550 Gray shale 6 inches above Stonefort limestone in New York Central Railroad cut in NEM NWM NEi^ sec. 30, T. 10 S., R. 5 E., Saline County, Illinois 551 Shale 13^ feet above Stonefort coal in New York Central Railroad cut in NE3^ NWj^ NEK sec. 30, T. 10 S., R. 5 E., Saline County, Illinois 552 Shale below 2-foot sandstone (lowest exposed shale in New York Central Railroad cut in NEK NWM NEM sec. 30, T. 10 S., R. 5 E., Saline County, Illinois 553 Madison Coal Company Hole No. 25 953 554 Madison Coal Company Hole No. 25 996 84 114 120 138 3 141 143 9 153 2 153 6 154 168 10 178 190 9 199 2 211 219 6 235 2 243 6 262 275 6 287 297 306 352 7 357 366 371 373 436 521 9 558 576 593 2 602 637 651 10 652 6 662 663 703 722 738 56 ILLINOIS STATE GEOLOGICAL SURVEY Sample Depth number Location ft. in. 555 Madison Coal Company Hole No. 25 1039 6 556 Madison Coal Company Hole No. 25 1089 5 557 Madison Coal Company Hole No. 25 1167 5 558 Madison Coal Company Hole No. 25 1220 7 559 Madison Coal Company Hole No. 25 1226 3 560 Madison Coal Company Hole No. 25 1233 561 Madison Coal Company Hole No. 25 1253 562 Madison Coal Company Hole No. 25 1298 8 563 Madison Coal Company Hole No. 25 1321 8 564 Madison Coal Company Hole No. 25 1455 565 Madison Coal Company Hole No. 25 1480 566 Madison Coal Company Hole No. 25 1557 2 567 Madison Coal Company Hole No. 25 1562 568 Madison Coal Company Hole No. 25 1572 569 Madison Coal Company Hole No. 25 1581 570 Madison Coal Company Hole No. 25 1587 571 Madison Coal Company Hole No. 25 1593 572 Madison Coal Company Hole No. 25 1600 573 Madison Coal Company Hole No. 25 1604 2 574 Madison Coal Company Hole No. 25 . . 1664 575 Madison Coal Company Hole No. 25 1667 576 Madison Coal Company Hole No. 25 1669 577 Madison Coal Company Hole No. 25 1673 578 Madison Coal Company Hole No. 25 . . . .- 1420 579 Madison Coal Company Hole No. 25 1438 580 Madison Coal Company Hole No. 25 1462 581 Madison Coal Company Hole No. 25 1490 582 Old Ben Coal Hole No. 24, SEM SE^ NEM sec. 8, T. 5 S., R. 2 E., Franklin County, Illinois 176 583 Old Ben Coal Hole No. 24, SE^ SEi< NE^ sec. 8, T. 5 S., R. 2 E., Franklin County, Illinois 227 7 584 Old Ben Coal Company Hole No. 31, SWj^ SEi^ sec. 35, T. 5 S., R. 2 E., Franklin 208 to County, Illinois 192 585 Shale under Shoal Creek limestone in NE3^ NEj^ SW^ sec. 33, T. 7 S., R. 6 E., Saline County, Illinois 586 Shale below DeKoven coal and above DeKoven sandstone from strip mine in SW3^ NEM NEM sec. 20, T. 10 S., R. 5 E., Saline County, Illinois 587 Shale above Davis Coal and below DeKoven sandstone at SW3^ NE3^ NE^ sec. 20, T. 10 S., R. 5 E., Saline County, Illinois 588 Approximately 5 feet above Curlew coal from abandoned quarry in SE3^ SE^ SE3^ sec. 25, T. 10 S., R. 3 E., Williamson County, Illinois 589 Clay lens in Shoal Creek sandstone in NW^ NW^ SWi^ sec. 3, T. 7 S., R. 5 E., Saline County, Illinois 590 Shale over coal exposed on east side of Illinois Central Railroad cut in NW3^ SEJ^ SEi^ sec. 2, T. 11 S., R. 5 E., Pope County, Illinois 591 Underclay of coal exposed on east side of Illinois Central Railroad cut in NW3^ SE3^ SEM sec. 2, T. 11 S., R. 5 E., Pope County, Illinois 592 Shale over New Burnside coal and below Creal Springs sandstone in NWJ^ NE3<^ SW34 sec. 4, T. 11 S., R. 4 E., Johnson County, Illinois 593 Shale below Curlew coal exposed in abandoned quarry at SEJ^ SE3^ SE3^ sec. 25, T. 10 S., R. 3 E., Williamson County, Illinois 594 Shale 2 feet above Curlew limestone from abandoned quarry in SE34 SE3^ SE^ sec. 25, T. 10 S., R. 3 E., Williamson County, Illinois 595 Silty shale below Stonefort coal and above 2-foot sandstone in New York Central Railroad cut in NEM NWi^ NE3^ sec. 30, T. 10 S., R. 4 E., Saline County, Illinois 596 Madison Coal Company No. 25 1620 597 Drury shale from road cut in NE^ NE^ NW^ sec. 34, T. 11 S., R. 2 E., Johnson County, Illinois 598 Shale exposed in drainage diversion ditch on west side of Illinois Central Railroad cut in NWi< SW34 NE3^ sec. 31, T. 11 S., R. 5 E., Pope County, Illinois 599 Shale as in 598 600 Shale from road cut on Illinois highway 145 in SWJ^ SW3^ sec. 14, T. 12 S., R. 5 E., Pope County, Illinois 601 Shale as in 600 602 Shale as in 600 PENNSYLVANIAN SEDIMENTS: VERTICAL PROFILE 57 Sample number B. Sandstones Location 10 Trivoli sandstone from Madison Coal Company Hole No. 25 11 Trivoli sandstone from Madison Coal Company Hole No. 25 12 Trivoli sandstone from Madison Coal Company Hole No. 25 13 Anvil Rock, sandstone from Madison Coal Company Hole No. 25 14 Pleasantview sandstone Madison Coal Company Hole No. 25 16 Davis sandstone Madison Coal Company Hole No, 25 . . . 17 Tradewater sandstone from Madison Coal Company Hole No. 25 18 Tradewater sandstone from Madison Coal Company Hole No. 25 20 Tradewater sandstone from Madison Coal Company Hole No. 25 21 Tradewater sandstone from Madison Coal Company Hole No. 25 22 Tradewater sandstone from Madison Coal Company Hole No. 25 23 Tradewater sandstone from Madison Coal Company Hole No. 25 24 Tradewater sandstone from Madison Coal Company Hole No. 25 25 Tradewater sandstone from Madison Coal Company Hole No. 25 26 Caseyville sandstone from Madison Coal Company Hole No. 25 27 Caseyville sandstone from Madison Coal Company Hole No. 25 28 Caseyville sandstone from Madison Coal Company Hole No. 25 40 Caseyville sandstone from Madison Coal Company Hole No. 25 41 Caseyville sandstone from Madison Coal Company Hole No. 25 42 Caseyville sandstone from Madison Coal Company Hole No. 25 290 Trivoli sandstone from Madison Coal Company Hole No. 25 291 Sandstone 10 feet above coal No. 5a in Delta strip mine in SE3^ SW34 SE3^ sec. 28, T. 9 S., R. 4 E., Williamson County, Illinois 292 Palzo sandstone in SW^ NEi^ NE^ sec. 20, T. 10 S., R. 5 E., Saline County, Illinois 293 DeKoven sandstone from Will Scarlet mine of Stonefort Coal Company in sec. 14, T. 10 S., R. 4 E., Williamson County, Illinois 294 Two-foot sandstone approximately 15 feet below Stonefort limestone in New York Central Railroad cut in NE^ NW)^ NEK sec. 30, T. 10 S., R. 5 E., Saline County, Illinois 299 Tradewater sandstone from Madison Coal Company Hole No. 25 . . . 300 Old Ben Coal Company Hole No. 51, SW3^ SEJi SE^ sec. 29, T. 9 S., R. 4 E., Franklin County, Illinois 301 Shoal Creek (?) sandstone in SW34 SW^ SE3^ sec. 1, T. 8 S., R. 5 E., Saline County, Illinois 303 Creal Springs sandstone from abandoned quarry in SE34 SE^ SE3^ sec. 25, T. 10 S., R. 3 E., Williamson County, Illinois 328 Sandstone from road cut in NW^ NEi^ NE3^ sec. 4, T. 9 S., R. 5 E., Saline County, Illinois 330 Mt. Carmel sandstone in road cut in SW34 NE^ SE34 sec. 25, T. 7 S., R. 3 E., Franklin County, Illinois Depth 169' 6" to 170' . 218' to 218' S" 239' to 239' 10" 405' 8" to 406' 620' to 620' 6" 801' 8" to 802' 4" 902' 7" to 903' 950' to 950' 9" 1065' to 1065' 6" 118' 8" to 119' 2" 1369' to 1369' 6" 1393' 6" to 1394' 1426' 3" to 1426' 8" 1517' 11" to 1518' 9 1608' to 1608' 10" 1653' 10" to 1654' 6 1484' 6" to 1485' 1541' 4" to 1542' 1556' to 1556' 6" 179' 8" to 180' 901' 197' 8" to 198' Sample number 298 312 314 315 316 318 381 604 605 C. Limestones Location Depth Old Ben Coal Company Hole No. 51, SWM SEi^ SEJ^ sec. 29, T. 7 S., R. 4 E., Franklin County, Illinois 93' to 100' Curlew limestone from Creal Springs quarry in SE3^ SE34 SE34 sec. 25, T. 10 S., R. 3 E., Williamson County, Illinois Madison Coal Company Hole No. 25 ... 281' to 283' 10" Bankston Fork limestone from Madison Coal Company Hole No. 25 . . 388' Trivoli limestone from Madison Coal Company Hole No. 25 .... 148' 10" to 149' 3' Cutler limestone from Madison Coal Company Hole No. 25 362' 1 " Herrin limestone from Madison Coal Company Hole No. 25 .... 447' St. David limestone Madison Coal Company Hole No. 25 535' 10" Stonefort limestone from Wise Ridge NE3^ NE34 SE^ sec. 4, T. 11 S., R. 4 E., Johnson County, Illinois 58 ILLINOIS STATE GEOLOGICAL SURVEY REFERENCES Biggs, D. L., and Lamar, J. E., 1955, Sandstone re- sources of extreme southern Illinois, a prelimi- nary report: Illinois Geol. Survey Rept. Inv. 188. 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