Illinois State Geological Survey am i ffll!illliiife E£EEEw?fflRf8S8Sj&£8. m ILLINOIS STATE GEOLOGICAL SURVEY 3 3051 00000 2166 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE STATE GEOLOGICAL SURVEY M. M. LEIGHTON, Chief BULLETIN NO. 48 GEOLOGY AND MINERAL RESOURCES OF THE CARBONDALE QUADRANGLE BY J. E. LAMAR S^KSsSffSS* 1 PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 1925 ILLINOIS GEOLOGICAL SURVEY LIBRARY STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE STATE GEOLOGICAL SURVEY M. M. LEIGHTON, Chief Committee of the Board of Natural Resources and Conservation A. M. S helton, Chairman Director of Registration and Education Kendkic C. Babcock Representing the President of the Uni- versity of Illinois Edson S. Bastin Geologist Schnepp & Barnes, Printers Springfield,, III. 1925 37018— 3M s537 X.' e LETTER OF TRANSMITTAL State Geological Survey Division, October 19, 1925. A. M. Shelton, Chairman, and Members of the Board of Natural Resources and Conservation, Gentlemen : I am pleased to transmit herewith a report on the Geol- ogy and Mineral Resources of the Carbondale quadrangle, and recommend that it be published as Bulletin No, 48. The field work upon which the report has been based was initiated by my predecessor, Mr. F. W. DeYVolf, and completed under my administra- tion. The report is presented with a view to acquainting the residents of the area with its general geology, and to directing intelligent prospecting of the. mineral resources of the region. It will be of particular interest and value also to professional geologists and students because of the geologically unique location of the Carbondale quadrangle, crossing the southern border of the Illinois Coal Basin, and the southern limit of the Illinoian drift sheet, and including a part of the Illinois Ozarks. This report is the first published Survey bulletin giving complete detailed descriptions of the entire Chester series in southwestern Illinois. Respectfully yours, M. M. Leighton, Chief. Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/geologymineralre48lama OUTLINE TAGE Chapter I. — Introduction 15 Location 15 Acknowledgments 15 General geologic relations 15 Topography 16 Relief 19 Drainage 19 Culture 20 Chapter II. — Descriptive geology 23 Introduction 23 Mississippian system 24 Lower Mississippian sub-system 24 Ste. Genevieve formation 24 Name and distribution 24 Lithologic character 25 Thickness 25 Stratigraphic relations 25 Paleontology 25 Correlation 26 Upper Mississippian sub-system (Chester series) 26 Introduction 26 Name 26 General lithologic character 26 Extent and sources of the Chester sediments in Illinois 26 Renault formation 27 Name and distribution 27 Lithologic character 28 Thickness 28 Stratigraphic relations 28 Paleontology 29 Correlation 29 Bethel sandstone 29 Name and distribution 29 Lithologic character 29 Thickness 30 Stratigraphic relations 30 Paleontology 30 Correlation 30 Paint Creek formation 30 Name and distribution 30 Lithologic character 30 Thickness 31 (5) 6 OUTLINE Chapter II. — Descriptive geology — Continued page Stratigraphic relations 31 Paleontology 31 Correlation 31 Cypress sandstone 31 Name and distribution 31 Lithologic character 31 Thickness 32 Stratigraphic relations 32 Paleontology 33 Correlation 33 Golconda limestone and shale 33 Name and distribution 33 Lithologic character 33 Thickness 35 Stratigraphic relations 35 Paleontology 35 Correlation 35 Hardinsburg sandstone 36 Name and distribution 36 Lithologic character 36 Thickness 37 Stratigraphic relations 37 Paleontology 37 Correlation 37 Glen Dean limestone 37 Name and distribution 37 Lithologic character 38 Thickness 39 Stratigraphic relations 39 Paleontology 40 Correlation 40 Tar Springs sandstone 40 Name and distribution 40 Lithologic character 41 Thickness 43 Stratigraphic relations 43 Paleontology 44 Correlation 45 Vienna limestone and shale 45 Name and distribution 45 Lithologic character 46 Thickness 48 Stratigraphic relations 48 Paleontology 48 Correlation 48 Waltersburg sandstone and shale 48 Name and distribution 48 Lithologic character 49 OUTLINE 7 Chapter II. — Descriptive geology — Continued page Thickness 50 Stratigraphic relations 50 Paleontology 50 Correlation 50 Menard limestone 50 Name and distribution 50 Lithologic character 51 Thickness 57 Stratigraphic relations 57 Paleontology 57 Correlation 58 Palestine sandstone 58 Name and distribution 58 Lithologic character 59 Thickness 60 Stratigraphic relations 60 Paleontology 60 Correlation 60 Clore formation 60 Name and distribution 60 Lithologic character 61 Thickness 66 Stratigraphic relations 67 Paleontology 67 Correlation 68 Degonia sandstone 68 Name and distribution 68 Lithologic character 69 Thickness 72 Stratigraphic relations 73 Paleontology 73 Correlation 74 Kinkaid limestone 74 Name and distribution 74 Lithologic character 75 Composite section 76 Thickness 77 Stratigraphic relations 77 Paleontology 77 Correlation 77 Pennsylvanian system 78 Introduction 78 The sub-Pennsylvanian unconformity 78 Pottsville formation 82 Name 82 Topographic expression 82 Lithologic character 83 Thickness 83 Chapter II. — Descriptive geology — Continued page Subdivision of the Pottsville formation 83 Wayside sandstone and shale member 84 Name and distribution 84 Lithologic character 84 Thickness 85 Stratigraphic relations 85 Paleontology 85 Lick Creek sandstone member 85 Name and distribution 85 Lithologic character 86 Conglomerate pebbles 87 Other minor lithologic features 89 Thickness 90 Stratigraphic relations 90 Paleontology 91 Correlation , 91 Drury shale and sandstone member 91 Name and distribution 91 Lithologic character 91 Thickness 95 Stratigraphic relations 95 Paleontology 95 Correlation 95 Makanda sandstone member 95 Name and distribution 95 Lithologic character 96 Thickness 99 Stratigraphic relations 99 Paleontology 100 Correlation 100 Carbondale formation 100 Name and distribution 100 Lithologic character 101 Vergennes sandstone member 101 Name and distribution 101 Lithologic character 101 Thickness 102 Limestones of the Carbondale formation 102 The coals of the Carbondale formation 103 Summary of the Carbondale formation 108 Thickness 109 Stratigraphic relations 109 Correlation 110 Paleontology 110 Post-Pennsylvanian, pre-Pleistocene systems 110 Pleistocene system Ill Pre-Illinoian loess HI Illinoian glacial drift 112 OUTLINE 9 Chapter II. — Descriptive geology — Concluded page Thickness 112 Distribution and topographic effect 114 Boulder erratics 115 Composition of the Illinois drift and its significance 116 In the area of thin drift 116 In the area of thick drift 118 Relations of the thick and thin drift 124 Weathering of the drift 124 Gumbotil 124 Outwash 125 Earlier valley fill 125 Post-Illinoian loess 126 Thickness 127 Origin 128 Source 128 Later valley fill 128 Recent system 130 Alluvium 130 Rainwash 130 Chapter III. — Structural geology 132 Introduction 132 Method of making structure map 132 The structure shown by the contour map 133 Warping 133 Faulting 135 Minor structural features 139 Jointing 139 Slumping 140 Chapter IV. — Geologic history 141 Introduction 141 Paleozoic era 142 Cambrian period 142 Ordovician period 142 Silurian period 142 Devonian period 143 Mississippian period 143 Lower Mississippian sub-period 143 Upper Mississippian (Chester) sub-period 143 Pennsylvanian period 146 Pottsville stage 146 Carbondale stage 147 McLeansboro stage 148 Post-Pennsylvanian folding 148 Permian period 148 Mesozoic era 148 Triassic, Jurassic, and Comanchean periods 148 Cretaceous period 149 10 OUTLINE Chapter IV. — Geologic history— Concluded page Cenozoic era 149 Pleistocene period 149 Illinoian time 149 Post-Illinoian time 152 Early valley filling 152 Loess deposition 152 Later valley filling 152 Recent period 152 Physiographic history 152 Chapter V. — Economic geology 155 Mineral resources 155 Coal 155 Pottsville coals 155 Carbondale coals 156 Character of the Murphysboro (No. 2) coal 158 Oil and gas possibilities 159 Structure 159 Possible sources 159 Potential gathering sands 159 Well records 160 Areas for testing 160 Road material and concrete aggregate 160 Agricultural limestone 161 Building stone 161 Shales and clays 162 Water 162 Sand and gravel 164 Soils 165 ILLUSTRATIONS PLATE PAGE I. Geologic map of the Carbondale quadrangle Pocket II. Topographic map of the Carbondale quadrangle Pocket III. East-west cross section of the northern part of the Carbondale quadrangle 104 IV. Structural geology of the Carbondale quadrangle Pocket V. Cross section of the Carbondale quadrangle showing the lack of accord- ance between the physiographic levels and the underlying forma- tions 152 FIGURE 1. Index map of southern Illinois showing the location of the Carbondale quadrangle 14 2. Characteristic Pottsville topography along the Egyptian trail in sec. 32, T. 10 S., R. 1 W 17 3. The Pottsville scarp, the Kinkaid flat and the Degonia terrace in sec. 28, T. 11 S., R. 1 W 17 4. Gap in the Pottsville scarp in Cedar Bluff, sec. 31, T. 11 S., R. 2 E 18 5. Looking south from Tiptop Knob near Cobden over the southern topo- graphic unit underlain by the formations of the Chester series.... 18 6. West end of Cedar Bluff as seen from Chimney Rock in sec. 25, T. 11 S., R. 1 E 20 7. Sandstone concretions in Tar Springs shale in center south line, sec. 35, T. 11 S., R. 1 W. showing ripple mark surfaces 42 8. Small fault in shaly beds of Tar Springs sandstone, center S. y 2 sec. 34, T. 11 S., R. 1 W 42 9. Contact of Tar Springs sandstone and Vienna limestone, sec. 34, T. 11 S., R. 1 W 44 10. "Hour glass" weathering of Clore limestone 62 11. Contact of Degonia shale and sandstone and Kinkaid limestone on Drury Creek in sec. 16, T. 11 S., R. 1 W 73 12. Contact of Pottsville and Kinkaid formations in sec. 9, T. 11 S., R. 1 W. 78 13. Pottsville conglomerate, showing typical unsorted material 86 14. Pebbles from the Pottsville conglomerate 88 15. Pottsville conglomerate showing smaller material than in figure 13, and much better sorted 88 16. "Honeycomb weathering" of Lick Creek sandstone 90 17. Thin and irregularly bedded Drury sandstone 92 18. Section showing the relations and character of the Murphysboro (No. 2) coal zone as observed at outcrops and mines 106 19. Sketch map showing areas of thick and of thin glacial drift in the northern half of the Carbondale quadrangle 113 20. Pebbly clay till underlain by stratified silt in sec. 15, T. 10 S., R. IE... 117 21. Graphic representation of the pebble count made of the drift exposure shown in figure 20 118 (ID 12 ILLUSTRATIONS FIGURE PAGE 22. Sandstone boulders imbedded in pebbly clay till as exposed on Syca- more Creek in sec. 24, T. 10 S., R. 1 W 120 23. Exposure of thick drift on Wolf Creek in sec. 25, T. 10 S., R. 1 E 121 24. Graphic representation of the pebble count made of the drift exposure shown in figure 23 122 25. Contact of calcareous till with recent stream gravels on Wolf Creek. . . . 123 26. The north wall of Stonefort Hollow north of Makanda 131 27. General north-south structure section extending from sec. 13, T. 11 S., R. 1 W., to sec. 2, T. 12 S., R. 1 W 134 28. West-east structure section from sec. 22, T. 11 S., R. 1 W., to sec. 33, T. 11 S., R. 1 E 134 TABLES PAGE 1. Geologic column for the Carbondale quadrangle 23 2. Results of washing tests on loess and modern alluvium 127 3. Average analyses of Murphysboro coal 158 13) GEOLOGY AND MINERAL RESOURCES OF THE GARBONDALE QUADRANGLE By J. E. Lamar CHAPTER I.— INTRODUCTION LOCATION The Carbondale quadrangle is located in the southern part of Illinois and includes portions of Jackson, Union, and Williamson counties (fig. 1). It is named from its largest town, Carbondale, located in the northwest corner of the area. The quadrangle has a length of 15 minutes of latitude and a width of 15 minutes of longitude and lies between the meridians 88° 00' and 88° 15' west longitude and the parallels 37° 30' and 3T° 45' north latitude. Its total area is about 236 square miles. ACKNOWLEDGMENTS The field work in the Carbondale quadrangle was carried on during a portion of the summer of 1922 and the summer of 1923. During these seasons respectively, the writer was ably assisted by Mr. A. W. Thurston and Mr. A. Pabst. The investigation was initiated under the direction of Mr. F. W. DeWolf, former Chief of the Geological Survey, whose guidance and encouragement are much appreciated. Acknowledgment is also made of the constructive criticism, personal assistance, and cooperation which Dr. M. M. Leighton, the present Chief of the Survey. Mr. Frank Krey and other members of the Survey staff, have willingly extended at all times. Lastly, to residents of the region hearty thanks are extended for their cor- dial hospitality, interest, and assistance. GENERAL GEOLOGIC RELATIONS Of the broader geologic relations of the Carbondale area, the following are outstanding: The southern boundary of the Illinois coal basin and of the Pennsylvan- ian formations crosses the quadrangle (see Plate I). Portions of two physiographic provinces of the United States, namely till plains and dissected plateaus, are included within the quadrangle. The extreme southern border of the great Illinoian glacier (see Plate I and figure 19) crossed the Carbondale quadrangle and the deposits left by the ice are of unusual interest. (15) 16 CARBONDALE QUADRANGLE At a later date, but still during Pleistocene time, valley filling which affected the Mississippi and its tributary Big Muddy River also affected the streams of this area (see Plate I). TOPOGRAPHY The configuration of the surface is shown by means of contours on the topographic map included with the geologic map, Plate I, in the pocket. According to Fenneman, 1 the quadrangle is a part of the "Interior Plains division" of the United States. The northern portion of the quad- rangle is classified as belonging to the "Till Plains section of the Central Lowland province," and the southern portion to the "western section of the Interior Low Plateau province." The characteristics of these two sections respectively are summarized 2 as "young till plains ; morainic topography rare ; no lakes" and as a "low, maturely dissected plateau with silt-filled val- leys." Fenneman's boundary was necessarily generalized because of the small scale of his map. With the more detailed data now at hand it has been possible to delineate the boundary more exactly. The "Till Plains section" should probably include that portion of the quadrangle underlain by the Carbondale formation (see fig. 1), except the hill country southeast of the city of Carbondale. The remainder of the area would belong to the "western section of the Interior Low Plateau province." In the Murphysboro-Herrin folio 3 a different nomenclature for the physiographic provinces of the quadrangle is given. Fenneman's "Till Plains section" Shaw calls the "Glaciated Plains province ;" and Fenneman's "western section of the Interior Low Plateau" Shaw names the "Ozark province." Although the relief of the rough belt of country which crosses south- ern Illinois in an approximately east-west direction through Union, Johnson, Pope, and Hardin counties, is not as great as that of the Ozark Highlands in Missouri, it seems reasonable to consider this rough belt as a continua- tion or spur of these highlands. The rugged country of the southern three- fourths of the Carbondale quadrangle is a part of this spur, to which the name "Illinois Ozarks" has been given. The topography of the Carbondale quadrangle is dominated largely by the bed rock, except possibly in the region immediate to Craborchard Creek where drift, loess, and valley filling partly obscure the contour of the bed rock surface. Elsewhere the loess and drift modify the angularity of the 1 Fenneman, N. M., Physiographic Divisions of the United States: Annals Assn. Am. Geographers, vol. VI, PI. I, 1917. 2 Op. cit., p. 33. 3 Shaw, E. W., and Savage, T. E., U. S. Geol. Survey Geol. Atlas: Murphysboro- Herrin folio (No. 185), 1912. INTRODUCTION 17 rock topography, but for the most part lack characteristic topographic ex- pression. The quadrangle is divisible, therefore, into three topographic units (fig. 1) roughly according to the underlying bed rock formations. The northern unit, underlain by the Carbondale formation, has a gently rolling surface for the most part, broken here and there by prominent hills capped with resistant Vergennes sandstone. Fig. 2. Characteristic Pottsville topography along the Egyptian trail in sec. 32, T. 10 S., R. 1 W. The Makanda sandstone caps the hills, the Drury shale makes up the slopes and in the bottom of the valley the Lick Creek sandstone outcrops. Fig. 3. The Pottsville scarp (Lick Creek sandstone), about 120 feet high, the Kinkaid flat and the Degonia terrace, in sec. 28, T. 11 S., R. 1 W. The central unit is underlain by the shales and massive sandstone mem- bers of the Pottsville formation (fig. 2). These latter are from 40 to 170 feet thick and give rise to a very rough and rugged topography with numer- ous bluffs and cliffs (fig. 3). The lower member of the Pottsville forma- tion, namely, the massive Lick Creek sandstone, forms a very bold scarp, 18 CARBONDALE QUADRANGLE particularly in the southeastern portion of the quadrangle. This scarp is commonly termed the Pottsville scarp (figs. 3 and 4). The southern unit is underlain by the Chester series (fig. 5). Its topography generally resembles that of the rugged central unit, but wher- Fig. 4. Gap in the Pottsville scarp (Lick Creek sandstone) in Cedar Bluff (sec. 31, T. 11 S., R. 2 E.) as seen from the 800-foot hill in sec. 13, T. 11 S., R. 1 E. Fig. 5. Looking south from Tiptop Knob near Cobden over the southern topo- graphic unit underlain by the formations of the Chester series. ever the less resistant formations of the Chester series outcrop, the surface is rolling or gently rolling. Erosion of the alternating resistant sandstones and less resistant limestones and shales of the Chester series has resulted in numerous terraces and flats. In particular, the Degonia and Tar Springs INTRODUCTION 19 sandstones form some very striking terraces, with the Kinkaid and Vienna limestones respectively forming the upper flats. Where outliers of Potts- ville sandstone are present in this unit, their protection of the underlying beds from erosion has resulted in the formation of striking isolated hills or knobs, such as Buck Knob in sec. 34, T. 11 S., R. 1 E. Besides these terraces and knobs there are also four groups of roughly accordant levels, distant from the present major drainage lines, which do not seem to be related to the character of the underlying formations (see Plate V). The flats at these levels, which are commonly on hill tops, are in some places underlain by shale or limestone and in others by sandstone. Such levels, because they are not due to rock structure, are thought to have been formed by the erosion of running water at a time when these now dissected flats were essentially at the level of the major drainage of the region. The flats were probably formed in part by the widening of the flood plains of the streams and in part by the gradual lowering of the divides. RELIEF The difference in elevation between the highest and lowest points on the quadrangle is about 510 feet. The lowest point is in the valley of Crab- orchard Creek where it leaves the quadrangle and has an elevation of 355 feet. The highest point is between 860 and 880 feet above sea level and is probably the top of the large hill in sec. 22, T. 11 S., R. 1 W. although several other hills, namely Tiptop Knob in sec. 29, the hill in the SW. cor. sec. 27, and the hill in the SE. % sec. 11, all in T. 11 S., R. 1 W., are also over 860 feet above sea level. The maximum local relief is to be found in the southeast corner of the quadrangle in sec. 36, T. 11 S., R. 1 E., where a ridge, locally known as Cedar Bluff (fig. 6), rises 360 feet above the level of the valley of Cache Creek. DRAINAGE Approximately the northern three- fourths of the Carbondale quad- rangle drains northward into Craborchard Creek, the largest stream in the area. A few miles north of the quadrangle it empties into Big Muddy River which flows into the Mississippi. The principal tributaries of Crab- orchard Creek are Drury, Indian, Little and Big Grassy, and Wolf creeks. The southern fourth of the quadrangle drains eventually into Ohio River. The three largest streams are Cache, Bradshaw, and Lick creeks, all of which are about the same size in this quadrangle. To the southeast, how- ever, the latter two creeks flow into Cache Creek. The volume of water carried by the streams of the quadrangle varies greatly with the season. In the summer during a dry period, the water in I'd CAKBONDALE QUADRANGLE Craborchard Creek is so very low that the stream may be easily crossed in many places. The water in the tributary valleys is correspondingly low. After a period of rainy weather, however, Craborchard and Cache creeks and their tributaries become very swollen, and backwater covers a great portion of their flood plains. The town of Makanda has several times been partly flooded by high waters of Drury Creek, and in years gone by and to some extent at present, the same stream during high water has been a source of nuisance and trouble to the Illinois Central Railroad in the vicinity of Makanda. Much splendid bottom land along Craborchard Creek is at present growing a luxuriant crop of weeds because it is flooded so often that culti- Fig. 6. West end of Cedar Bluff (about 240 feet high) as seen from Chimney Rock in sec. 25, T. 11 S., R. 1 E. vation is impracticable. A little well-directed ditching and straightening of the stream's tortuous channel would doubtless reclaim a great deal of this land for cultivation. CULTURE As far as is known the earliest inhabitants of the Carbondale region were the Indians. Arrow-heads, axes, and artifacts of various sorts are found in many places. Locally the ground is literally covered with flint chips which seem to record the sites of camps where arrow-heads were made. In the southern part of the quadrangle great numbers of flint chips beneath an overhanging bluff of Lick Creek sandstone, suggest that these cliffs may have served as camp sites in bad weather. The flint used very INTRODUCTION 21 commonly resembles that of some of the Mississippian formations in the vicinity. The valley in the N. y 2 of sec. 27, T. 10 S., R. 1 W„ just north of the town of Makanda, is known as Stonefort Hollow (see fig. 26). It is named from an old stone fort which was built on a shelf of the Makanda sand- stone which makes up the steep sides of the valley. Vandals have torn down the masonry of the old fort, and its builders and architecture are now a matter of conjecture. The southern counties of the State were settled early in its history. The bottom lands along the Ohio and Mississippi rivers were settled first, and from them the population gradually moved inland. A very interesting picture of the country at that time is given by Worthen 1 in his description of Union County, in the first comprehensive reconnaissance study of the geology of Illinois. He writes : "In the spring of 1852 I undertook to make a reconnaissance of this [Ozark] ridge from the Big Muddy to the Ohio, through what was then an almost unbroken wilderness, and on foot and alone, with hammer in hand, I traversed this wild and picturesque region, reaching the Ohio in eight days after leaving Big Muddy. The only sign of civilization to be met with then, in this region, was a log cabin now and then, occupied by some squatter's family from East Tennessee or North Carolina, who imagined themselves entirely secure in this wilderness from the encroachments of a higher civilization. But the squatter planted a few peaches about his cabin, and when the Illinois Central Railroad was built, and the settlers began to flock into this long neglected region, they observed that when the peach failed everywhere else north of Ohio River, the orchards on this sandstone ridge always produced an abundant crop. Hence, the attention of fruit-growers was naturally drawn to this region, now brought within a day's travel of the Chicago market; and the result has been that these lands which, in 1852 were not con- sidered worth the government price of a dollar and a quarter an acre, are now readily sold at from $150 to $200 per acre, and are owned and occupied by the most intelligent and refined rural population that can be found in the west. This is undoubtedly the finest fruit region in the State, and more fruit is annually shipped from Cobden than from any other station on the road, and the annual products of the orchards and vineyards of this county must steadily and rapidly increase for years to come." At the present time the fruit-raising industry within the quadrangle is confined largely to the high lands in the western portion. Some fruit is raised in the eastern half, but the lack of a near by railroad and of good roads tends to discourage the growing of such crops as necessitate the in- tensive use of transportation for a comparatively brief period of time. Con- sequently corn, wheat, and stable garden truck are the more common prod- ucts in this area. The southwestern part of the quadrangle also grows a large amount of garden truck as well as corn. The northern part of the 1 Worthen, A. H., Geology of Illinois, Geological Survey of Illinois, vol. Ill, pp. 56 and 57, 1868. 22 CARBONDALE QUADRANGLE area, particularly the lower land in the vicinity of Craborchard Creek, is given over primarily to corn and to grazing. Stock in small numbers are common everywhere in the quadrangle, but the most intensive dairying is carried on in the northern fourth of the area. A deplorable condition exists in the area underlain by the Pottsville formation in certain of the eastern parts of the quadrangle. The move- ment of the population citywards has left a great deal of land untended, with the result that gullies are rapidly eating back into the flat area on the hills and ridges, converting them into miniature badlands. Consequently the land is practically untillable, and cannot be restored to its former rolling surface without a great amount of labor. The population of the Carbondale quadrangle is about equally divided between the towns and the rural districts. A rough count of the number of houses shown on the topographic map, and calculations allowing five people to each house, give a rural population of about 7800. The 1920 census gives the population of Carbondale as 6267 ; Cobden, 688 ; Makanda, 310 ; and Boskydell, 30. The greatest rural population is found in the northern and western parts of the area. This distribution is doubtless due to the railroad in the western portion and the proximity of the northern portion to Carbondale, Marion, Carterville, and Herrin. There are two state concrete highways in the Carbondale quadrangle, the one connecting Cobden with Carbondale and also extending south of Cobden, and the other connecting Carbondale with Carterville and Marion (see the topographic map in the pocket with Plate I). Another con- crete road has been laid along the west line of sees. 14 and 23, T. 9 S., R. 1 E., as far south as Craborchard Creek, and extension of this road is planned. In general elsewhere the roads are dirt roads. In the northern and southern topographic units of the quadrangle (see figure 1), some effort is made to keep the roads dragged. Elsewhere, particularly in the rougher parts of the Pottsville area, the roads are poor and often impassable in rainy weather. The roughness of the topography, the extreme activity of slope wash and gullying, and the torrential character of the streams dur- ing wet weather make the mere preservation of roads and bridges a matter of considerable labor in itself. The gullying and wash also expose the bed rock in many places in the roads and necessitate constant changing of the right of way in order to have enough loess over the bed rock to make the road passable. The Illinois Central is the only railroad within the confines of the quad- rangle. The main line south from Chicago passes through Carbondale, Boskydell, Makanda, and Cobden, and has doubtless furthered the develop- ment of that area. The Herrin branch of the Illinois Central crosses the northeast corner of the quadrangle. CHAPTER II.— DESCRIPTIVE GEOLOGY INTRODUCTION Exposed at the surface in the Carbondale quadrangle are rocks ranging in age from Lower Mississippian to Recent time. Wells drilled in the quadrangle have not penetrated strata older than Lower Mississippian, but deeper wells drilled in near by areas have found rocks of Devonian, Silurian, Ordovician and Cambrian age. Plate I, the geologic map, shows the area of outcrop of formations known from exposures and Table 1 gives the sequence of formations outcropping in the Carbondale quadrangle or in adjoining parts of Illinois and Missouri. The exposed strata are described in this chapter in order of their age, the oldest, known as the Ste. Genevieve formation, first. Table 1 — Geologic column for the Carbondale quadrangle Cenozoic group Recent system Wash Alluvium Pleistocene system Loess Late valley fill Loess Early valley fill Illinoian drift Pre-Illinoian loess or silt Pliocene, Miocene, Oligocene, or Eocene system Bronze cherts (?) Paleozoic group Pennsylvanian system McLeansboro formation 1 Carbondale formation Pottsville formation Makanda sandstone and shale Drury shale and sandstone Lick Creek sandstone Wayside sandstone and shale Mississippian system Upper Mississippian sub-system Upper Chester series Kinkaid limestone Degonia sandstone Clore limestone and shale 1 McLeansboro formation absent in the Carbondale quadrangle but present in the Herrin quadrangle to the north. 23 24 CARBONDALE QUADRANGLE Palestine sandstone and shale Menard limestone Waltersburg sandstone and shale Vienna limestone and shale Tar Springs sandstone Middle Chester series Glen Dean limestone and shale Hardinsburg sandstone and shale Golconda limestone and shale Cypress sandstone Lower Chester series Paint Creek limestone and shale Bethel sandstone and shale Renault limestone and shale Lower Mississippian sub-system Meramec series Ste. Genevieve formation St. Louis limestone Warsaw-Spergen limestone Osage series Primarily limestone Kinderhook series Limestone and shale Devonian system Primarily limestone and shale Silurian system Limestone, sandstone and shale Ordovician system Limestone, sandstone and shale Cambrian system Primarily sandstone MISSISSIPPIAN SYSTEM Lower Mississippian Sub-system ste. genevieve formation NAME AND DISTRIBUTION The Ste. Genevieve formation is the only member of the Lower Missis- sippian sub-system exposed in the Carbondale quadrangle. The formation is named from excellent exposures at and in the vicinity of Ste. Genevieve, Missouri. The outcrops in the quadrangle are confined to a triangular tract about a mile long and a quarter of a mile wide in the very southwest corner of the area (PL I). The east side and hypotenuse of the triangle is a fault which probably brings Cypress, Paint Creek, Bethel, and Renault sediments in contact with the upper Ste. Genevieve, although the fault and contact of the respective formations are not actually observable. STE. GENEVIEVE FORMATION 25. LITHOLOGIC CHARACTER In the Dongola quadrangle the Ste Genevieve consists of a lower oolitic member (Fredonia) about 175 feet thick, overlain by interbedded sandstones, shales and oolitic limestones totaling about 100 feet in thickness. In the Carbondale quadrangle the few outcrops of Ste. Genevieve belong to the upper part of the formation and consist of thin-bedded, brown sand- stone, best exposed in the north-south gully near the west line of sec. 5, T. 12 S., R. 1 W. ; and of limestone, best observed in the creek at the center of the west line of the same section where the following succession of beds was measured : Section of upper Ste. Genevieve strata, including the red oolite, measured in a gully near the west line of sec. 5, T. 12 S., R. 1 W. Thickness Feet 4. Sandstone, light buff, firmly cemented; in beds 1 to 6 inches thick. Grains angular. Weathers brown with brown-black bands and specks of iron hydroxide 3. Clay, very sandy, red; may be much-weathered, sandy limestone. Grains rounded to subangular 1± 2. Sandstone, brown, thin-bedded, much weathered %± 1. Limestone, red and gray, oolitic and sandy, medium-grained; in beds 6 to 12 inches thick. Weathers to a porous, brown, sandy mass 2± These beds are part of the upper Ste. Genevieve, and the red oolite is the equivalent of the similar bed described as occurring near the top of the formation in the Dongola quadrangle 1 . THICKNESS The thickness of that portion of the Ste. Genevieve which is exposed in the Carbondale quadrangle is estimated as about 30 feet or about one- tenth of the entire formation. STRATIGRAPHIC RELATIONS Neither the top nor the bottom of the upper Ste. Genevieve is exposed in the area of outcrop in the quadrangle. The formation is probably con- formable with the St. Louis below it. The upper contact with the Renault as exposed in the Dongola quadrangle is unconformable, though perhaps only locally so. PALEONTOLOGY The most distinctive fossils of the upper Ste. Genevieve are the brachi- opod Pugnoides ottumwa and the oval-shaped, cog-like, basal plates of Platycrinns pcnicillus. No fossils of importance other than the preceding 1 Krey, Frank, The Geology and mineral resources of the Dongola quadrangle, unpublished manuscript. 26 CARBONDALE QUADRANGLE were observed at the one very small outcrop of limestone previously described. CORRELATION The beds below the Renault in the Carbondale quadrangle are corre- lated as upper Ste. Genevieve because of their continuity with beds in the Dongola quadrangle which have been identified as upper Ste. Genevieve on the basis of their stratigraphic position and faunal content. Upper Missippian Sub-system, Chester Series x introduction NAME The name Chester was originally applied to the formation now known as the Palestine sandstone by Swallow 2 in 1858, and comes from the town of Chester in Randolph County, Illinois, where the Palestine was formerly extensively quarried for dimension stone. Since that time the application of the name has gradually been extended until at present it includes all the beds below the Pennsylvanian and above the Ste. Genevieve. GENERAL LITHOLOGIC CHARACTER The Chester series is an alternation of limestone and sandstone for- mations, with shale associated with both. At some places lenses of sand- stone are found within the limestone formations, but no distinct limestone beds were noted within the sandstone formations. Locally, however, the latter are calcareous. EXTENT AND SOURCES OF THE CHESTER SEDIMENTS IN ILLINOIS The maximum extent of the Chester sea can only be approximated. Following the deposition of the highest known Chester sediments, a period of extensive erosion was inaugurated during which many feet of deposits were removed. As far as is known at present, our record of Chester deposition ends with the Kinkaid limestone. Unfortunately the Chester sediments north of the Carbondale quadrangle are concealed by Penn- sylvanian rocks and information concerning the former is therefore ob- tainable only from the records of wells. For a time it was thought that the Chester or Upper Mississippian sediments in Illinois were restricted largely to the southern part of the State, but a well recently drilled at Trilla, in Coles County, records about 700 feet of sediments which are prob- ably Upper Mississippian, and likewise a well at Decatur, in Macon County, shows about 200 feet of sediments of approximately the same age. It 1 For a detailed history of the Chester group see Weller, Stuart, The geology of Hardin County: 111. State Geol. Survey Bull. 41, pp. 121-132, 1920. 2 Proc. Am. Ass. Adv. Sci. vol. 11, pt. 2, p. 5, 1858. BENAULT FORMATION 27 appears, therefore, that the Chester group is more extensive than was for- merly thought. Up to the present time no satisfactory correlation has been effected between the members of the Chester sequence in central Illinois and those exposed in outcrop in southern Illinois. With the accumulation of more data, however, it may be possible to trace at least certain units of the south- ern Illinois section into central Illinois. The source of the Chester sediments as a whole can not in all probabil- ity be definitely related to any specific area, as sediments of one sort or an- other were doubtless being contributed to the sea by all the land immediate to the shore line. There were, however, the Ozark uplift, the Cincinnati arch, and the Nashville dome, high areas which may have been specifically responsible for certain formations or parts of them. It is also probable that land to the north, perhaps the Canadian shield, constituted another source of sediments. In this connection it is of interest that in general the ripple marks in the Chester sandstones in this and the Dongola quadrangle 1 indicate currents coming rather consistently from the north, northwest, or northeast. This possibly, but not necessarily, indicates the derivation of the sediments from land to the north. In places in the quadrangle a limestone conglomerate lies at the base of the Pottsville, suggesting that erosion was relatively active on some land surface which, judging from the angularity of some of the pebbles, was not exceedingly far distant. In Hardin County, Illinois, the Pennsylvanian rocks rest in places on formations below the Kinkaid, in Randolph County on the Menard, and in Monroe County on the Yankeetown. It is evident that there was an extensive period of erosion in post-Chester pre-Pennsyl- vanian time. It is also possible that some of this erosion may have occurred during late Chester time, while the Degonia and Kinkaid were being de- posited in the deeper parts of the Chester basin, and that older Chester deposits may have furnished some of the Degonia and Kinkaid sediments. RENAULT FORMATION NAME AND DISTRIBUTION The Renault formation is named from outcrops in Renault Township in Monroe County, Illinois. Its exposures in the Carbondale quadrangle are but three in number and of very slight extent. They occur as follows : a little west of the center of the NW. Y A sec. 5, T. 12 S., R. 1 W., in the creek bed ; in the valley at the center of the south line of the NW. Y\ sec. 5 ; and almost at the extreme edge of the quadrangle in the valley at the 1 Krey, Frank, Personal communication. 28 CARBONDALE QUADRANGLE center of the SE. % sec. 5. Plate I, the geologic map, shows the area of outcrop. LITHOLOGIC CHARACTER The Renault exposures are beds of the upper portion of the formation, and consist of limestone and shale. The limestone is commonly granular, oolitic, fragmental, light gray, gray or blue-gray, with numerous small or medium-sized Pentremites. Dense shaly limestones are uncommon. The shales are gray, green-gray, and hematite-red in color, and many are siliceous or sandy. The best exposure observed occurs in the creek at the west edge of the NW. j4 se c 5, T. 12 S., R. 1 W., where the beds outcrop as follows : Section of Renault strata in the NW. y± sec. 5, T. 12 8., R. 1 W. Thickness Feet Concealed 4. Limestone, gray, granular; composed largely of fragmental material. Pentremites common 2 + 3. Shale, hematite-red and green-gray, locally sandy 7 2. Limestone, like bed No. 4 1± 1. Shale, gray-green, siliceous 3 + Concealed To the south, in the Dongola quadrangle, the Renault is much more extensively exposed and consists largely of limestone with thin interbedded shale layers. The limestone has the general characteristics described above and in addition medium-grained beds occur locally. The shales are also similar to those previously described except that locally they are distinctly calcareous. THICKNESS In all probability the thickness of the upper part of the Renault, as exposed in the Carbondale quadrangle, is about 20 feet, or about one-fourth the estimated thickness of the entire formation in the Dongola quadrangle. 1 STRATIGRAPHIC RELATIONS The basal contact of the Renault was not observed but, as previously stated, is probably an unconformable one. The contact with the overlying Bethel was also not observed, but the following section of the Renault lime- stone very close to the top of the formation suggests unconformable rela- tions. 1 Krey, Frank, The geology and mineral resources of the Dongola quadrangle, unpublished manuscript. BETHEL SANDSTONE 29 Generalized section of part of the Renault formation exposed along the creek oottom near the center of the BE. y± sec. 5, T, 12 8., R. 1 W. Thickness Ft. In. 3. Conglomerate, consisting of rounded fragments of coarse grained, greenish limestone and yellow shale. Upper part of the Renault . . 6+ 2. Limestone, dense, compact, very oolitic, interbedded with dark gray shaly beds containing Talarocrinus and Pentremites 3 1. Limestone, coarse grained, granular, containing many oolite grains and crinoid fragments 3 + The Renault-Bethel contact in the Dongola quadrangle 1 is also reported as unconformable. PALEONTOLOGY Fossils are common in most limestone beds of the Renault. Bryozoa and brachipods are numerous. The following association of forms is, however, characteristic of the formation : numerous Pentremites, particu- larly princctonensis, godoni, pinguis, and buttsi; the presence of Talaro- crinus bases and Lyropora, and the paucity of Archimedes. CORRELATION The beds called Renault are so correlated, on the basis of the similarity of their fauna and stratigraphic position, to that of the type Renault. BETHEL SANDSTONE NAME AND DISTRIBUTION The name Bethel was originally given to this sandstone from exposures in Crittenden County, Kentucky, and later extended to Hardin County, Illi- nois. At this place the Bethel is prominent, bluff-forming sandstone over 100 feet thick. In the Carbondale quadrangle, however, the formation is very inconspicuous and probably is not over 10 feet thick. For this reason it has been mapped with the Paint Creek (see Plate I). Two small exposures of Bethel were noted, one in the creek near the center of the SE. % sec. 5, T. 12 S., R. 1 W., and the other in the creek bank in the SE. corner NW. y 4 NW. % sec. 5, T. 12 S., R. 1 W. LITHOLOGIC CHARACTER As observed, the Bethel is a dense, medium-grained, gray-green or gray sandstone. Locally it resembles quartzite and is calcareous. In places it contains relatively large sand grains or small pebbles. It weathers brown or reddish-brown with a hummocky surface. The slumped condition of one outcrop suggests a shale below the sandstone, though shale was not observed. 1 Krey, Frank, The geology and mineral resources of the Dongola quadrangle, unpublished manuscript. 30 CARBONDALE QUADRANGLE THICKNESS As previously stated, the thickness of the Bethel is probably between 5 and 10 feet. STRATIGRAPHIC RELATIONS No contacts of the Bethel with over- or underlying formations were observed. The formation is probably unconformable with the beds below it, and conformable with the Paint Creek above it. PALEONTOLOGY No fossils were found in the Bethel sandstone except a few imperfect brachiopod casts in some of the more calcareous layers. CORRELATION The Bethel sandstone is so correlated because of its stratigraphic posi- tion above the Renault and below the Paint Creek formations. PAINT CREEK FORMATION NAME AND DISTRIBUTION The original description of the Paint Creek was made from exposures in Monroe and Randolph counties, Illinois, where the formation has a char- acteristic hematite-red shale member which reflects itself in the color of the water in the streams and of the soil which it underlies. The exposures in the Carbondale quadrangle, however, do not exhibit such red shale beds, but as would be expected, follow more the character of the formation in southeastern Illinois. Only a few exposures of Paint Creek were noted. The formation out- crops over a small area in the W. y 2 sec. 5, T. 12 S., R. 1 W., and is brought abruptly in contact with the upper Ste. Genevieve by a fault which limits the western extent of the formation on the quadrangle (see Plate I). The best exposure of Paint Creek occurs in the creek bed in the center of the N. y 2 NW. y A sec. 5, T. 12 S., R. 1 W., and in the lower end of a gully joining the- same creek near the center of the S. y 2 of the same section. Another small outcrop may be found in the NE. 34 SW. 34 SE. 34 sec. 5, T. 12 S., R. 1 W. LITHOLOGIC CHARACTER From its exposures in the Carbondale quadrangle, the Paint Creek may be briefly described as a coarse-grained, granular, blue-gray, fragmental limestone, commonly in heavy beds. Fossils are abundant. Locally the limestone contains clay pellets 1/16 to 34 inch in diameter and is conglom- eratic. No shale in place was observed, but rather copious talus consisting of thin laminae of dark gray shale in a gully side in the Paint Creek interval suggests the presence of shale in the formation. CYPRESS SANDSTONE 31 In the Dongola quadrangle 1 to the south, the Paint Creek consists of a variable succession of shale and limestone with local sandstone beds. Non- calcareous gray and dark gray, thin bedded limy shale forms the major portion of the formation. The limestones occur as thin platy beds, though locally heavy beds are present, and share the general characteristics enumer- ated above. The sandstone occurs in the shale as thin beds or lenses which vary from J4 to 12 inches in thickness. THICKNESS Little opportunity is afforded by the outcrops of the Paint Creek for determining its thickness. An estimate would be between 20 and 30 feet. STBATIGRAPHIC RELATIONS No contacts of the Paint Creek with other formations were observed, but it is probably conformable with the underlying Bethel and unconform- able with the overlying Cypress. PALEONTOLOGY Fossils are numerous in the Paint Creek. The flattened, clove-shaped plates of Pterotocrinus serratus, abundant Archimedes, and Chonetes ches- terensis are most characteristic of the formation. CORRELATION The Paint Creek of the Carbondale quadrangle is so called because of its fauna and its stratigraphic position above the Bethel and below the Cypress sandstone. CYPRESS SANDSTONE NAME AND DISTRIBUTION The exposures of the Cypress sandstone along Cypress Creek, Union County, Illinois, constitute the type section, and the one from which the formation receives its name. Outcrops of the Cypress in the Carbondale quadrangle are limited to a triangular tract with a total area of about a square mile, bounded on two sides by faults and on the third by the south margin of the quadrangle (see Plate I). Exposures of the sandstone are common in most of the gullies in this tract, but the best are those to be found in the bluffs along the main creek in the NW. % sec. 5, T. 12 S., R. 1 W., and in the gully in the NW. Y^ SE. % of the same section. LITHOLOGIC CHARACTER The lower portion of the Cypress sandstone very commonly forms bluffs and its presence is therefore topographically conspicuous. The beds 1 Krey, Frank, The geology and mineral resources of the Dongola quadrangle, unpublished manuscript. 32 CARBONDALE QUADRANGLE of this portion of the formation are massive, varying from 2 to 6 feet in thickness, and are composed of medium-sized, rounded to sub-angular grains which are commonly gray or light buff when fresh. Weathering causes them to become brown if iron is present or gray if it is absent. The thinner-bedded strata which overlie the massive portion have probably about the same total thickness as the latter. The beds vary from 8 to 24 inches in thickness and average about 11 inches. Such data as were collected indicate a gradual decrease in the thickness of the individual beds from the massive portion of the Cypress towards the upper part of the for- mation. The beds above the massive portion are cross-bedded and conspicu- ously ripple-marked. The ripple marks vary from 2 to 5 inches from crest to crest and from ^ to ^ inches in depth. Sandy shale and shale are also present in the Cypress but are not com- monly exposed. In general the shale occurs in the upper and lower por- tions of the formation and is commonly associated with thin-bedded sand- stones. Minor amounts of mica and pyrite occur locally in the thin-bedded sandstones and sandy shales. The following section is made from the best exposure of the upper part of the Cypress. Section of the upper part of the Cypress formation measured in the center of sec. 5, T. 12 S., R. 1 W. Thickness Feet 3. Sandstone, thin-bedded, shaly 8± 2. Shale, gray, brown, and buff; in beds 1/16 to ^4 inch thick. Some layers have numerous gray sandstone concretions which weather buff and constitute a rather distinct layer in themselves 5± 1. Sandstone, brown, cross-bedded, ripple-marked, in beds 8 to 20 inches thick 25± THICKNESS No opportunity was afforded to measure the entire thickness of the Cypress since part of the formation is faulted out. It is estimated, how- ever, that 70 to 80 feet of the formation outcrop in the Carbondale quad- rangle. In the Dongola quadrangle the total thickness is placed at between 100 and 120 feet. 1 STRATIGRAPHIC RELATIONS The contact of the Cypress with the underlying Paint Creek was not observed, and that with the Golconda is concealed by the fault constituting the northeast boundary of the outcrop area of the formation. The sand- stone is, however, probably unconformable with the Paint Creek below, and conformable with the Golconda above as suggested by a transition from 1 Krey, Frank, The geology and mineral resources of the Dongola quadrangle, unpublished manuscript. GOLCONDA FORMATION 33 sandstone to limestone between the two formations in the Dongola quad- rangle. PALEONTOLOGY A few fragments of Lepidodendron trunks were the only fossil remains observed. CORRELATION The Cypress has been so correlated because of almost continuous out- crops from the type locality to the Carbondale quadrangle and because of its stratigraphic position. GOLCONDA LIMESTONE AND SHALE NAME AND DISTRIBUTION The name Golconda for the limestone lying above the Cypress sand- stone comes from exposures in the region north of the town of Golconda in Pope County, Illinois. Like the rest of the Lower Chester formations in the Carbondale quad- rangle, the Golconda does not outcrop extensively (see Plate I). Its ex- posures are confined to a narrow strip about a quarter of a mile wide in the lower slopes of the northwest-southeast ridge through sec. 32, T. 11 S., R. 1 W. and sec. 4, T. 12 S., R. 1 W. The southwestern margin of the band of outcrop is terminated abruptly by a fault extending almost due northwest- southeast which brings the limestone of the Golconda formation against the Cypress sandstone. The best exposures are to be found in the lower portions of the gullies in the southwest side of the ridge in sec. 32, T. 11 S., R. 1 W., in the main creek at the center of the SW. )/\ of the same sec- tion, and in the gully west of the road in the SW. Y\ NW. % sec. -1, T. 12 S., R. 1 W. LITHOLOGIC CHARACTER The exposures of the Golconda in the Carbondale quadrangle show neither a complete section nor contacts with the over- or underlying for- mations, and afford little basis, therefore, for subdivision of the formation. It is probable, however, that the formation as a whole will fit into the three- fold division found in the Dongola quadrangle 1 , where the Golconda is sepa- rated into an uppermost member, dominantly limestone ; a middle member, dominantly shale, and a lower dominantly limestone, but having more shale than the upper member. The limestones of the Golconda as observed are largely coarsely or medium granular, gray or dark gray, occurring in beds 8 to 36 inches thick, and commonly contain the ear-shaped wing plates of Ptcrotocrinus capitalis. 1 Krey, Frank, The geology and mineral resources ..of the Dongola quadrangle, unpublished manuscript. 34 CARBONDALE QUADRANGLE The limestone varies greatly locally, however, some beds being crinoidal or oolitic, and others medium- or fine-grained. The shale of the Golconda, presumably the middle portion, varies from fossiliferous calcareous shale to thinly laminated siliceous shale. Along the creek flowing southeast through the SW. ]/^ sec. .32, T. 11 S., R. 1 W., especially at the road angle and southeast to where the road crosses the creek, the following succession of beds, probably middle Gol- conda, is exposed. Section of the middle part of the Golconda formation measured in the SW. X A sec. 32, T. 11 S., R. 1 W. Thickness Feet Sandstone, calcareous, medium grained, gray, fossiliferous. Weathers brown. Beds average about 10 inches 4± Limestone, medium grained, dark gray, locally red and granular 3± Shale, gray black, siliceous 3± Concealed. The exposure in the creek is not continuous, due to interruptions by small faults which bring sandstone and limestone, sandstone and shale, and shale and limestone, respectively, in contact with each other. The following sections, though fragmentary, give a somewhat more definite idea of the Golconda at specific outcrops. Section of part of the Golconda formation exposed in the SE. y± NW. y± SW. % sec. 32, T. 11 S., R. 1 W., in the road cut near the oase of the hill Thickness Feet Shale, soft, gray 11± Limestone, granular, coarse-grained, fossiliferous. (Pterotocrinus capi- talis wing plates, Pentremites ooesus? and Archimedes, compact type) 2± Shale, soft, gray 3± Section of part of the Golconda formation in the NW. y± SW. *4 NW. x /± sec. 4« T. 12 S., R. 1 W., in the gully west of the road Thickness Feet Concealed; sandstone float Limestone, oolitic, gray, granular 6± Limestone, granular, thick bedded (1 foot) crinoidal; weathers with a rough surface; Pentremites of pyriformis type common, also Ptero- tocrinus sp.f wing plates and bryozoa 6± Limestone like bed above, but with interbedded shale. Shale occurs commonly in beds about 2 feet thick, and is abundantly fossiliferous 7± Limestone, gray, fossiliferous, in beds 8 to 12 inches 4± Shale, gray and buff, non-fossiliferous, siliceous 4± Concealed. GOLCONDA FORMATION 35 Section of part of the Golconda formation exposed at the center NW. % SW. X A sec. 32, T. 11 8., R. 1 W., in the north bank of the creek Thickness Feet Limestone, red and gray, granular in beds 1 to 2 feet thick. Locally contains gray shale blebs. Contains especially Pterotocrinus capitalis wing plates, Pentremites of pyriformis type, and Archimedes of com- pact variety 3 -f- Shale, gray black, thinly laminated, siliceous 6 THICKNESS The probable thickness of the beds of the Golconda exposed in the Car- bondale quadrangle is about SO feet. This constitutes approximately two thirds of the entire thickness of the formation which is reported 1 from better exposures in the Dongola quadrangle to be from 120 to 130 feet. STRATIGRAPHIC RELATIONS As previously stated, the fault which truncates the middle member of the Golconda also conceals the contact with the Cypress. In the Dongola quadrangle, however, good exposures indicate conformable relations by a gradual transition from sandstone to limestone at the Golconda-Cypress contact. The contact of the Golconda with the overlying Hardinsburg likewise was not observed. In the Dongola quadrangle, however, the con- tact was noted at two places, at each of which the sandstone of the Hardins- burg rested directly upon the limestone of the Golconda without interme- diate beds. Such evidence suggests unconformable relations between the two formations. PALEONTOLOGY The most distinctive fossils of the Golconda are Pentremites platybasis and Pentremites obesus, and the ear-shaped wing plates of Pterotocrinus capitalis. The first and third forms were commonly found, and one de- formed specimen of the second. All the observed limestone beds and many of the shale layers are highly fossiliferous, and afford a variety of brachiopods, bryozoa (especially Archimedes), and Pentremites. CORRELATION The similar fauna, lithologic character, stratigraphic position, and al- most continuous outcrop from the type locality to the Carbondale quad- rangle, seem sufficient to establish the age of the Golconda. 1 Krey, Frank, The geology and mineral resources of the Dongola quadrangle, unpublished manuscript. 36 CARBONDALE QUADRANGLE HARDINSBURG SANDSTONE NAME AND DISTRIBUTION The Hardinsburg sandstone receives its name from exposures in Breck- inridge County, Kentucky. The formation is well developed in Hardin and Pope counties, Illinois, but thins out to the west till in the Carbondale quadrangle it becomes relatively thin and inconspicuous. No definite corre- lation of the Hardinsburg of southeastern Illinois with the sandy phases of the Okaw of southwestern Illinois has been made, but it is quite possible that it does extend into that region and is represented there by the sandy beds of the middle Okaw. But two exposures of the Hardinsburg were noted, and both were of small extent. They are of importance mostly as indicating the presence of the Hardinsburg, rather than its exact position. The formation as mapped represents the interval between the Golconda and Glen Dean lime- stones which it should occupy, rather than the interval in which it was found outcropping (see Plate I). The area supposedly underlain by the Hardins- burg parallels the main Glen Dean outcrop in the southwest corner of the quadrangle. LITHOLOGIC CHARACTER The two outcrops of the Hardinsburg observed are as follows : Section of Hardinsburg strata exposed in the creek bottom in the SW. *4 SW. V± NW. y± sec. 32, T. 11 S., R. 1 W. Sandstone, 3± feet, thin-bedded, with some shaly partings; beds V 8 to 3 inches, average y± inch in thickness. Section of Hardinsburg strata exposed in the gully east of the road in the center SW. y± sec. 32, T. 11 S., R. 1 W. Sandstone, 12 ± inches, fine-grained, buff, calcareous; with green and gray dis- coidal clay inclusions. In beds about 6 inches thick. Weathers buff and porous; probably blue-gray when fresh. The Hardinsburg in the Dongola quadrangle 1 is quite variable litholog- ically. In places it is a massive cliff-forming sandstone, but in proximity to the Carbondale quadrangle, the exposures are largely thin-bedded, cal- careous sandstone. It is thought that in the latter quadrangle the formation is largely thin-bedded sandstone, calcareous in places and locally contain- ing 6- to 12-inch beds, which are responsible for the local topographic "flats" in evidence at intervals along the southwest side of the ridge in which the formation occurs. 1 Krey, Frank, The Geology and mineral resources of the D'ongola Quadrangle, unpublished manuscript. GLEN DEAN LIMESTONE 37 THICKNESS The thickness of the Hardinsburg sandstone is estimated at from 20 to 30 feet, on the average probably closer to the former than the latter figure. STRATIGRAPHIC RELATIONS The probable unconformity of the Hardinsburg sandstone with the Golconda limestone below has already been mentioned. The contact of the sandstone with the Glen Dean limestone above it was not exposed in the Carbondale quadrangle. In the Dongola quadrangle to the south, how- ever, the contact shows a gradual transition from sandstone to limestone, without indications of a break in sedimentation 1 . PALEONTOLOGY No fossils were observed in the Hardinsburg sandstone, though Lepi- dodendron and other plant remains have been reported from the formation elsewhere. CORRELATION The practical continuity of the Hardinsburg sandstone from Hardin County, Illinois, to the Carbondale quadrangle, and its stratigraphic posi- tion, are the basis for the assigned correlation. GLEN DEAN LIMESTONE NAME AND DISTRIBUTION The Hardinsburg sandstone is overlain by the Glen Dean limestone, the probable equivalent of the upper part of the Okaw limestone of south- western Illinois. The formation has been named from exposures in Breck- inridge County, Kentucky, and traced across Ohio River into Illinois. The outcrops of the Glen Dean in the Carbondale quadrangle are few and fragmentary and are for the most part limestone, with some shale as suggested by the talus and the character of the topography. Outcrops are most numerous in the middle slopes of the southwest side of the ridge ex- tending in a northwest-southeast direction through sec. 32, T. 11 S., R. 1 W. and sec. 4, T. 12 S., R. 1 W. (see Plate I). Other small areas of out- crop occur in the banks of the streams at the following places all in T. 12 S., R. 1 W. ; the SE. % sec. 4 and SW. ]/ A sec. 3 ; the SW. ]/ A sec. 2, the northeast bank; the SW. %. sec. 1, the southwest bank; and the NE. ^4 sec. 2, in both banks and continuing in the southwest bank for about a fifth of a mile in sec. 1. The best exposures are to be found in the vicinity of the NE. J4 sec - 2, in the creek banks in the SW. Y^ NW. ]/ A SW. >4 sec. 3, and in the gully in the NW. ]/ A NE. ]/ A SW. V A sec. 4, T. 12 S., R. 1 W. ; and in the upper 1 Krey, Frank, The geology and mineral resources of the D'ongola quadrangle, unpublished manuscript. 38 CARBONDALE QUADRANGLE part of the gully at the center of the S. y 2 sec. 32, T. 11 S., R. 1 W., and other gullies in the vicinity. LITHOLOGIC CHARACTER So few are the outcrops and so poor, that very little can be said about the lithologic character of the Glen Dean in the Carbondale quadrangle with certainty. The best section of the upper part of the formation was observed in the gullies in the southwest valley slope of Cache Creek in the NE. l /\. sec. 2 and the W. y 2 sec. 1, T. 12 S., R. 1 W. Practically all the gullies in this slope show sections of varying degrees of completeness. All agree as to the general sequence of beds although minor differences are in evidence from gully to gully. A composite section made from measured sections in four different gullies is given below. Composite section including parts of the Tar Springs and Glen Dean formations, based on exposures in gullies in the southivest slope of Cache Creek in the NE. 14 sec. 2 and the W. V 2 sec. 1, T. 12 8., R. 1 W. Thickness Middle Tar Springs — Ft. In. 15. Sandstone, medium-grained, buff; in heavy beds (8 to 36 inches) 25 Lower Tar Springs — 14. Sandstone and sandy shale. Shale is gray and buff. Sand- stone is fine-grained, gray and brown, in irregular beds V 8 to y 2 inch thick. Locally it resembles quartzite and contains thin shale inclusions 13 Transition or Lower Tar Springs — 13. Shale, gray black, thinly laminated; contains a few yellow sandstone concretions. Siliceous 9 Transition or upper Glen Dean — 12. Limestone, coarse-grained, granular, red; composed largely of fossil debris 1 4 11. Limestone, medium-grained, granular, gray 10 10. Sandstone, dense, gray, calcareous, resembling quartzite. Weathers brown. Grains rounded to sub-angular 1 8 9. Concealed 2 1 8. Sandstone, moderately fine-grained, irregularly bedded, gray- buff 7 2 7. Sandstone, fine-grained, gray-white, fossiliferous. Grains angu- lar. Many porous spots due to leaching out of calcareous material replacing the fossils 1 Glen Dean — 6. Limestone, medium-grained, granular, gray 1 8 5. Like No. 6, but very oolitic 3 10 4. Concealed 3 4 3. Limestone, coarse-grained, granular gray, fossiliferous 9 2. Limestone, coarse-grained, coarsely granular, light gray and gray-brown; in beds 1 to Sy 2 feet thick 7 11 1. Limestone, dense, fine-grained, light gray 1 11 Concealed. GLEN DEAN LIMESTONE 39. The partial exposures of the remainder of the formation as seen in the quadrangle may be summarily described as medium or coarse-grained, gray, fossiliferous and crinoidal limestone which breaks and weathers with a rough surface. No shale was observed in place but fragments in the creek bank in the NW. l /± SW. % sec. 3, T. 12 S., R. 1 W., suggest its presence at that locality. Just across the south line of the quadrangle at the center of the south line of the SW. y A SW. ]/ A sec. 3, T. 12 S., R. 1 W., in the gully at the fork of the road, the following section of what is probably the upper or middle part of the Glen Dean is exposed. Section of Tar Springs and Glen Dean strata exposed in sec. 3, T. 12 S., R. 1 W. Thickness Tar Springs sandstone — Ft. In. 7. Sandstone, medium-grained, loosely cemented .* 6. Concealed 23 7 Glen Dean limestone — 5. Limestone, granular, fossiliferous, with a buff tinge. Beds average about 12 inches thick 2 1 4. Limestone, like No. 5, but gray; weathers slabby 1 3. Limestone, like No. 4 1 9 2. Concealed 5 1 1. Limestone, medium- and coarse-grained, dark gray, fossilifer- ous; in beds 8 to 15 inches thick 5 7 Krey 1 , writing of the Glen Dean in the Dongola quadrangle, considers the upper half of the formation as mainly limestone with some interbedded shale, and the lower part as largely shale with some interbedded limestone, and it is probable that this division of the formation applies roughly in the Carbondale quadrangle. THICKNESS No opportunity was afforded to measure the entire section of the Glen Dean because of unfavorable topographic conditions. An estimate, how- ever, is between 30 and 50 feet. STRATTGRAPHIC RELATIONS The probable conformity of the Hardinsburg sandstone and the Glen Dean limestone has already been mentioned. A description of the forma- tions at the only observed contact of the Glen Dean and Tar Springs sand- stone is given under the discussion of the lithologic character of the Glen Dean. From this section it would seem that, locally at least, toward the close of Glen Dean time and previous to definitely Tar Springs time, the sea changed from one depositing dominantly calcareous sediments to one 1 Krey, Frank, The geology and mineral resources of the Dongola quadrangle, unpublished manuscript. 40 CARBONDALE QUADRANGLE depositing a mixture of calcareous, arenaceous and argillaceous sediments. These latter calcareous deposits consisted of oolitic grains, debris from shells and other calcareous tests. The fragmental condition of a great part of the material composing the calcareous deposits suggests erosion and transpor- tation of the constituents and this, together with the fact that such deposits were interbedded with sands, silts, and muds, suggests that at the close of Glen Dean time conditions of deposition were unstable, probably reflecting like conditions in the relations of land and sea areas. It is therefore prob- able that during the transition between Glen Dean and Tar Springs time, deposition was interrupted in certain areas, once or several times, while in certain other favorable areas deposition was practically continuous. As a result of these relations the formations may be unconformable in some places and conformable in others. PALEONTOLOGY The observed exposures of Glen Dean limestone are all rich in fossils, most of them forms common to the middle or upper Chester lime- stones. A few specimens of Pentremites spicatus are present, but Pris- mopora scrratitla, which occurs prolifically in parts of the Glen Dean in Har- din County, 1 was observed at but two outcrops and there only as a few scat- tered specimens. These last two mentioned forms are typical of the Glen Dean in Hardin County and elsewhere. CORRELATION The Glen Dean of the Carbondale quadrangle is correlated with that of Hardin County, Illinois, because of the practical continuity of outcrop between the two places, its similar fauna, and because of its stratigraphic position above the Hardinsburg sandstone and below the Tar Springs sand- stone. TAR SPRINGS SANDSTONE NAME AND DISTRIBUTION The Tar Springs sandstone is named from exposures of a bituminous sandstone at the type locality in Breckinridge County, Kentucky, whence it has been traced into Illinois. The major portion of the Tar Springs is a heavy-bedded sandstone, much in evidence in the topography as bluffs and ridges. The ridge extending northwest-southeast through sec. 32, T. 11 S., R. 1 W., and sec. 4, T. 12 S., R. 1 W., is due to the protection from erosion which the Tar Springs affords the less resistant underlying for- mations. The outcrops of Tar Springs are confined to the southwest corner of the quadrangle (see Plate I). The formation underlies the surficial ma- 1 Weller, Stuart, The geology of Hardin County, Illinois: 111. State Geol. Sur. Bull. 41, p. 197, 1920. TAR SPRINGS SANDSTONE 41 terial in practically all of sees. 2 and 3, T. 12 S., R. 1 W., and partially underlies sec. 1, T. 12 S., R. 1 W., and sec. 35, T. 11 S., R. 1 W. ; from this region the outcrop band extends northwest, narrowing from a width of about Y\ of a mile, to about ^ of a mile where it leaves the west margin of the quadrangle in the NW. cor. sec. 32, T. 11 S., R. 1 W. Exposures of the sandstone may be found at intervals in the bed of Cache Creek and in most of the larger tributary valleys and gullies. The best exposures, however, are to be found in the valleys in the E. y 2 sec. 4, the W. y 2 sec. 3, and the E. y 2 sec. 2, T. 12 S„ R. 1 W., and in the SE. y A sec. 35, T. 11 S.. R. 1 W. LITHOLOGIC CHARACTER The Tar Springs varies noticeably from place to place. In a general way, however, a three-fold division into upper, middle, and lower portions is possible. The upper two divisions are exhibited with sufficient frequency to reasonably establish them ; the lower, however, was observed at one locality only, at intervals for about half a mile in the southwest bank of Cache Creek and the gullies associated therewith in the XE. T /\ sec. 2, T. 12 S., R. 1 W. Whether or not this lowest member is present throughout the quadrangle cannot be definitely stated as it is commonly concealed by talus from the middle member. The upper portion of the Tar Springs consists of sandstone, sandy shale, and shale. The sandstone is thin-bedded, fine-grained, and locally micaceous. The shale is irregularly bedded, brown, gray, or black ; some portions of it are distinctly sandy and others are composed of very fine particles of siliceous material. In the creek near the center of the S. line sec. 35, T. 11 S.j R. 1 W'., an exposure of sandy shale contains large concre- tions of sandstone. These concretions break along bedding planes which have ripple-marked surfaces (fig. 7). Ripple marks are prevalent in the sandstones of this part of the for- mation. They are commonly of the irregular current type. From crest to crest they vary from 3 to 5 inches and have an average depth of about Y% inches. The best exposures of the upper -part of the Tar Springs occur at the following places : in the creek in the NW. y± XE. y NW. y<\ sec. 34 ; a little farther south along the same creek at the center of the north line of the NW. 34 SW. y± sec. 34. just north of the road crossing; in the tributary to Cache Creek in the SW. Y A XW. V A SE. y A sec. 33 ; and in the creek along the road near the center of the S. y 2 sec. 34. all in T. 11 S., R. 1 W. (fig. 8). The middle part of the Tar Springs may be described as the bluff- forming member. It consists of medium-grained sandstone in beds 8 to 36 42 CARBONDALE QUADRANGLE Fig. 7. Sandstone concretions in Tar Springs shale, cen. S. line sec. 35, T. 11 S., R. 1 W. When the concretions are broken open, the surfaces of the sandstone layers show ripple marks. The slabs of sandstone on the right side of the picture are such layers. Pig. 8. Small fault in shaly beds of the Tar Springs sandstone, center S. hk sec. 34, T. 11 S., R. 1 W. TAR SPRINGS SANDSTONE 43 inches thick. Eight- to twelve-inch beds are very common, but in many instances are quite possibly the result of weathering and erosion of beds which appear much thicker when unweathered. This has been observed to be the case in several places where weathered portions of the. sandstone have been artificially removed in road excavating or grading. Considering the middle portion of the Tar Springs as a whole, however, the thinner- bedded sandstone occurs in its upper part with increasing thickness of beds towards its base. Cross-bedding is not marked, but occurs most commonly in the more massive beds. Ripple marks are common, especially in the upper thinner beds. They are mostly current ripple marks and in general measure from 2^2 to 3^ inches from crest to crest and are from 3/16 to 6/16 of an inch deep. The lowest member of the Tar Springs, consisting as it does of thin- bedded sandstone and shale, is very commonly concealed by talus from the middle heavy-bedded part of the formation. As previously stated, at but one locality were these lower Tar Springs beds and their contact with the Glen Dean observed in good exposure, namely in the NE. J4 sec - 2> an d the W. y 2 sec. 1, T. 12 S., R. 1 W. The section at this locality, described in the discussion of the lithologic character of the Glen Dean limestone, indicates the thickness and character of the lower part of the Tar Springs so far as it is known in the quadrangle. THICKNESS The thickness of the Tar Springs as a whole may be inferred from the following : Feet Upper Tar Springs 10 to 20 Middle Tar Springs 40 to 60 Lower Tar Springs to 20 Total thickness 50 to 100 The most common thickness of the Tar Springs is between 70 and 90 feet. The minimum thickness of about 70 feet probably occurs in sec. 32, T. 11 S., R. 1 W., and the vicinity, and the maximum in sec. 2, T. 12 S., R. 1 W., and the vicinity. In general, the formation probably thins to the northwest, such thinning being accommodated, largely in the middle member. STRATIGRAPHIC RELATIONS Under the discussion of the Glen Dean limestone the relations of the Tar Springs and that formation have already been mentioned as probably conformable in places and unconformable in others. 44 CARBONDALE QUADRANGLE The actual contact of the Tar Springs sandstone and the overlying Vienna limestone was observed at but one place (fig. 9), where the follow- ing section was measured. Section including the transition from the Tar Storings to the Vienna formation, observed at the center of the 8. V 2 sec. 3J f , T. 11 S., R. 1 W. Vienna — Limestone, coarse-grained, gray, granular, fossiliferous; in irregular beds. Transition bed — Calcareous sandstone, locally containing pyritic sandstone nodules. The sandstone is underlain by a few inches of gray clay, possibly residual. Total thickness, 4 to 6 inches. Tar Springs — Shale, irregularly bedded, brown, gray, and black; sandy. Pig. 9. Contact of Tar Springs sandstone and Vienna limestone, cen. S. y 2 sec. 34, T. 11 S., R. 1 W. The hammer rests on a transitional layer of calcare- ous sandstone. The above section suggests conformable relations between the Vienna and Tar Springs, and it is probable that such relations are general through- out the areal extent of the Tar Springs in the quadrangle. PALEONTOLOGY No fossils were observed in the Tar Springs except a few scattered fragments of Lcpidodcndron trunks. In Hardin County, however, fossil shales are reported from which Cardioptcris polymorpha, Sphenopteris, and VIENNA FORMATION 45 Lepidodendron have been identified and have been used as evidence in corre- lating the Illinois Tar Springs with that of the type locality in Kentucky. 1 CORRELATION The Tar Springs sandstone in the Carbondale quadrangle has been correlated with that of the type locality on the basis of the practically con- tinuous outcrop from the one place to the other, and on the basis of its stratigraphic position below the Vienna limestone and above the Glen Dean limestone. VIENNA LIMESTONE AND SHALE NAME AND DISTRIBUTION The Vienna formation has been named from good exposures in the vicinity of the town of Vienna in Johnson County, Illinois. The formation is a succession of alternating limestones and shales and as a consequence does not produce bold topographic features. Exposures of the Vienna are not numerous or extensive, except under very favorable topographic conditions. The band of outcrop of the Vienna begins with a width of about 1/10 of a mile at the south margin of sec. 6, T. 12 S., R. 1 E. (see Plate I), and extends northwest, with a few interruptions where it is covered with alluv- ium, to the NE. y^ sec. 35, T. 11 S., R. 1 W., at which place it has a width of about a quarter of a mile. From this last place it turns to the west and continues in that direction to the center of the W. Yi sec. 35, then north to the SW. Y\ sec. 26, T. 11 S., R. 1 W., and finally southwest to the center of the N. y 2 sec. 3, T. 12 S., R. 1 W. From here to the west margin of the quadrangle only one outcrop of limestone which may be Vienna was observed. This was in the east-west road at the center of sec. 32, T. 11 S., R. 1 W., where a few feet of shale and some weathered chert resembling Vienna chert were exposed. Aside from the possible differentiation of the Vienna and Menard on the basis of the more or less characteristic appearance of the weathered Vienna chert and siliceous limestone, these two formations are generally indistinguishable either by their fossil content or lithologic characteristics except where separated by the Waltersburg sandstone. Under the discus- sion of the Waltersburg sandstone, the probable local disappearence of this formation as a recognizable lithologic unit is indicated. It is also very pos- sible that the Vienna thins greatly and possibly pinches out. In the Dongola quadrangle 2 , the Vienna has an estimated thickness of 30 to 40 feet. In 1 Weller, Stuart, The geology of Hardin County: 111. State Geol. Surv. Bull. 41, p. 201, 1920. 2 Krey, Frank, The geology and mineral resources of the Dongola quadrangle, unpublished manuscript. 46 CARBONDALE QUADRANGLE the Carbondale quadrangle the best sections indicate a thickness of 20 to 25 feet. This suggests a regional thinning to the west, especially in view of the fact that the Vienna is conformable with the overlying and under- lying formations, and the difference in thickness cannot therefore be attrib- uted to an erosional unconformity. Inasmuch as in this quadrangle it has been impossible to separate the Vienna and Menard where the Waltersburg is absent or not exposed, and the Tar Springs and Waltersburg where the Vienna is not exposed, the three first mentioned formations have been mapped together in such places as Menard-Waltersburg- Vienna undifferentiated. It is thought that most of the beds so mapped are Menard. The best exposures of the Vienna may be found at the following places: —at the SE. cor. NE. y A sec. 1, T. 12 S., R. 1 W. ; in the north-south valley near the east line of the SE. ]/ A NE. ]/ A sec. 35, T. 11 S., R. 1 W., and also in the W. ]/ 2 NE. y A NW. % of the same section; in the SE. ]/ A SW. }i SW. ]/ A sec. 26, T. 11 S., R. 1 W., and also in the SW. % SE. y A SW. y A of the same section; and in the SE. y A NE. % SW. y A sec. 34, T. 11 S., R. 1 W., as well as along the road in the center of the S. y> S. y of the same section. LITHOLOGIC CHARACTER In the Dongola quadrangle to the south the Vienna consists almost exclusively of limestone, and such outcrops as were visited resembled closely those of the middle Menard. In the Carbondale quadrangle, however, the upper and middle portions of the Vienna contain considerable shale inter- bedded with limestone. The limestones of the Vienna are varied. Some are fine-grained, dense, gray or dark gray, siliceous and locally cherty ; others are similar except that they are argillaceous instead of siliceous, and weather brown and scaly ; and still others are medium-grained, medium or coarsely granular, gray, blue- gray, or dark gray, and also locally cherty. The bedding planes between the various layers are commonly uneven or hummocky. The medium-grained beds commonly weather lighter than the unaltered rock if the weathering is not extreme, and the granular ones similarly with a rough, uneven surface. In protected slopes where the siliceous limestones' or calcareous cherts weather without the continual removal of the detritus formed thereby, the product is a porous, ocherous material in which are preserved with great fidelity prints of the bryozoa which were in the original stone. This weathered chert is commonly characteristic of parts of the Vienna and is often the only observable evidence of the presence of the formation. VIENNA FORMATION 47 The following sections are among the best observed in the quadrangle : Section of the middle (?) part of the Vienna formation, measured in the west bluff of the creek in the SE. *4 SW. y± SW. 14 sec. 26, T. 11 8., R. 1 W. Thickness Ft. In. 8. Shale and limestone, dark gray, thin-bedded, calcareous, fossilifer- ous; with interbedded, medium-grained, granular, dark gray, fossiliferous limestone which weathers brown and scaly 4 7. Shale, dark gray, thin-bedded, calcareous, fossiliferous 1 2 6. Shale, thinly laminated, gray-black, non-calcareous 5 7 5. Shale, lenticular bed, like No. 7, with sandstone lenses; maximum exposed thickness 3 10 4. Concealed 10 3. Limestone, gray, very coarse-grained, crinoidal (poorly exposed).. .. 10 2. Shale, gray-black, fossiliferous, especially bryozoa 6 I. Concealed Section of strata exposed in the small gully in the center NE. 14 NW. y± sec. 35, T. 11 8., R. 1 W. Thickness Ft. In. 15. Sandstone, thin-bedded (1 to 3 inch), buff, porous. Probably cal- careous where unweathered 4 14. Concealed 3 8 13. Limestone, dense, fine-grained, dark gray 4 12. Concealed 3 8 II. Limestone, like No. 13, but slightly lighter gray and siliceous; weathers buff and earthy 1 5 10. Concealed 1 5 9. Limestone, medium-grained, dark gray 8 8. Concealed 1 9 7. Limestone, dense, fine-grained, argillaceous, dark gray 1 5 6. Concealed 1 7 5. Limestone, gray, fine-grained, highly fossiliferous; upper 5± inches very granular and crinoidal. One bed 3 2 4. Concealed; section offset 300 feet to the south, in the east bank of the main creek. Vertical concealed interval probably not over 5 feet 3. Shale, gray and brown, sandy, with sandstone lenses 9 6± 2. Shale, tough, gray-black, without marked bedding. Contains thin seam of coal and carbonaceous plant markings. Occurs as lenses between beds No. 3 and No. 1 6± 1. Sandstone, medium-grained, gray-white sandstone, speckled brown. Beds 1 to 6 inches thick 1 In the preceding section, bed No. 15 is probably Waltersburg sandstone, beds No. 13 to No. 5, inclusive, Vienna limestone, and beds No. 3 to No. 1, inclusive, Tar Springs. It is of interest to note that from a crevice in bed 48 CARBONDALE QUADRANGLE No. 5 a spring issues, suggesting shale immediately beneath it. The shale is not exposed, however, and whether it is Vienna shale or the upper part of bed No. 3 is a matter of conjecture. THICKNESS As previously stated the one section which includes the formations overlying and underlying the Vienna, shows its thickness to be about 20 feet. To the west the thickness of the formation is probably less and to the southeast probably more, perhaps about 30 feet. STRATIGRAPHIC RELATIONS The probably conformable relations of the Vienna limestone and the Tar Springs sandstone have been discussed under the Tar Springs and the section which is the basis for this conclusion was given therewith. No con- tacts of the Vienna with the Waltersburg w r ere observed in this quadrangle. In the Dongola quadrangle to the south, however, exposures show a gradual transition from the fossiliferous shales of the Vienna to the siliceous shale of the Waltersburg. This evidence would lead to the conclusion that de- position was uninterrupted between Vienna and Waltersburg times and that the formations are conformable. PALEONTOLOGY The major portion of the fauna of the Vienna is similar to that of the Menard. Such forms as Sulcatopinna niissouricnsis, Allorisma clavata Spirifer increbescens, Diaphragmus elegans, and Composite, subquadrata, all typical Menard forms, occur in the Vienna and the last three in particular commonly. CORRELATION The Vienna limestone and shale of the Carbondale quadrangle is correl- ated with the same formation at its type locality because of the practical continuity of the outcrop and its similar stratigraphic position below the Waltersburg and above the Tar Springs. WALTERSBURG SANDSTONE AND SHALE NAME AND DISTRIBUTION The Waltersburg formation is named from good exposures near the town of Waltersburg in Pope County, Illinois. Exposures of the forma- tion, even poor ones, are rare in the Carbondale quadrangle and its pres- ence is most commonly indicated by sandstone fragments or talus resting on or above the Vienna limestone. The outcrop of the Waltersburg (see Plate I) roughly parallels that of the overlying Menard, and begins along the south line of sec. 6, T. 12 S., R. 1 E., as a strip about half a mile wide and extends northwest as a narrow WALTERSBURG FORMATION 49 band about an eighth of a mile wide to the northwest corner of sec. 36, T. 11 S., R. 1 W. The band of outcrop then turns west and a little south into the center of the N. y 2 of sec. 35, T. 11 S., R. 1 W., and then almost due north. The best exposures in this outcrop area may be found in the creek running along the side of the road in the center W. J4 sec. 6, T. 12 S., R. 1 E., in the gully in the SW. cor. sec. 25, T. 11 S., R. 1 W. ; along the road in the SE. ]/ 4 NW. y A sec. 1, T. 12 S., R. 1 W. ; along the road in the NE. y NW. y<\ of the same section ; and in the heads of the gullies in the SE. y A NW. y 4 sec. 35, T. 11 S., R. 1 W. These last mentioned exposures are the westernmost outcrops of the Waltersburg observed in the quadrangle, except those in the creek bottom in the NW. y 4 , sec. 32, T. 11 S., R. 1 W., which are probably, but not cer- tainly, outcrops of this formation. A few accumulations of loose blocks of sandstone somewhat resembling the Waltersburg in lithologic character were noted between these two last mentioned exposures, but their mode of occurrence and topographic position do not suggest a derivation from an underlying sandstone, but rather float from an overlying sandstone or per- haps rip-rap thrown in a creek to prevent erosion. It is quite probable that in the western part of the quadrangle the formation pinches out for a few miles or thins to an insignificant bed, perhaps turning to shale which would be difficult to distinguish from the lower part of the Menard or upper part of the Vienna. In the area where the Waltersburg is thin or its presence questionable it has been mapped with the Vienna- Waltersburg-Menard undifferentiated. LITHOLOGIC CHARACTER The fragmentary exposures of the Waltersburg permit only general- izations as to its lithologic character. The outcrops consist of thin-bedded or thinly laminated gray-black or black, siliceous shale, and thin-bedded sandstone. The sandstone is commonly firmly cemented and resembles quartzite. Locally it is pyritic and in places calcareous. Where fresh it is gray, but weathers to a buff, brown, or mottled brown. The following de- scription of the outcrop gives the characteristics of the sandstone and shale at a typical outcrop. Section of part of the Waltersburg formation exposed in the SW. Vi NW. Vi sec. 6, T. 12 S., R. 1 E. Thickness Ft. In. Sandstone, fine-grained, compact, almost quartzitic. Weathers to thin irregular slabs, which are very yellow along the bedding planes. Bedding planes irregular 2 6 Shale, black, soft, splits into thin laminae, interbedded with yellow rust-colored sandstone and sandy shale in thin beds (Vs to y 2 inch) . . 2-\ 50 CARBONDALE QUADRANGLE THICKNESS Near the south margin of the quadrangle, the Waltersburg is probably about 30 feet thick, but it thins to the northwest until it pinches out entirely or is only a few feet thick, and not distinguishable as a lithologic unit. STRATIGRAPHIC RELATIONS As mentioned under the description of the Vienna limestone, the con- tact of the Waltersburg and the Vienna is probably conformable. The ex- posures of the Waltersburg-Menard contact are so few that their contact relations are not determinable. These formations are, however, probably conformable. PALEONTOLOGY Some of the beds of the Waltersburg contain the imprints of organic remains, the calcium carbonate of which has been largely dissolved and the resulting voids only partially refilled with silica. In the NW. *4 SE. % NW. J4 sec - 6, T. 12 S., R. 1 E., there is an exposure of about five inches of sandstone which is fossiliferous, containing numerous brachiopods, especially Spirifer increbescens. CORRELATION The outcrops of the Waltersburg are traceable practically without in- terruption to its type locality in Pope County. This together with its strati- graphic position below the Menard is the basis for its correlation. MENARD LIMESTONE NAME AND DISTRIBUTION The name Menard was given to this limestone from the exposures in the Mississippi River blufTs near Menard in Randolph County, Illinois. In the Carbondale quadrangle the outcrop of the Menard limestone (see Plate I) begins in sec. 5, T. 12 S., R. 1 E., as a band about a mile wide. The limestone outcrops on both sides of Bradshaw Creek, but by far the best exposures are found in the tributary valleys in the west valley slope. Especially in the S. y 2 sec. 5, are limestone sinks common and well devel- oped. Small exposures may be observed in these sinks as well as in the aforementioned gullies. From the south line of sec. 5, the band of outcrop extends northwest through sec. 36 and into sec. 25 T. 11 S., R. 1 W., varying in width from l /[ to 24 of a mile. Good exposures may be seen in the east- west creek near the north lines of sees. 5 and 6, T 12 S., R. 1 E., and in the gully along the east side of the road in the SW. cor. sec. 31, T. 11 S., R. 1 E. Of par- ticular note are the splendid exposures in the north-south valley and its tributary gullies in the E. l / 2 sec. 36, T. 11 S., R. 1 W. and the almost con- MENARD LIMESTONE 51 tinuous outcrop for about a mile in the valley extending southeast from the NW. cor. sec. 25, T. 11 S., R. 1 W., and in its tributaries. From sec. 25 the outcrop area continues west and a little south to the west line of sec. 26 with excellent exposures in the main valley and its tributaries in the W. y 2 sec. 26. Thence, the outcrop band narrows to a width of from x /% to J4 mne an d turns southwest into the SW. cor. sec. 34, T. 11 S., R. 1 W., and then west and north beyond the edge of the quad- rangle through the town of Cobden, following along the lower and gentle slopes of the Kinkaid-Degonia scarp. Good exposures in this area may be found in the upper portion of the north-south valley in the center of the NE. J4 sec. 34, T. 11 S., R. 1 W. ; in the two southeast-flowing creeks in the NW. Y\ of the same section; in the valleys in the S. y 2 SW. J4 sec - 28 and the N. y 2 NW. *4 sec. 33, T. 11 S., R. 1 W. ; and in an abandoned quarry at the northward turn in the road near the center of the SW. J4 sec. 29, T. 11 S., R. 1 W. One small isolated outcrop occurs in the center of the W. y 2 sec. 31, T. 11 S., R. 1 E., in the bed of the northeast-flowing creek. In sees. 28, 29, 32, 33, and 34, T. 11 S., R. 1 E. the Menard, Walters- burg and Vienna have been mapped together as an undifferentiated unit because of the impracticability of separating these three beds. The greater part of the area so mapped is, however, Menard limestone. LITHOLOGIC CHARACTER Lithologically the Menard limestone resembles the Kinkaid limestone more than any other Chester formation. In fact, certain portions of the two, if superimposed, would be difficult to distinguish from each other. Both formations represent periods of extensive limestone deposition, and in the vicinity of the Carbondale quadrangle, at least, the Menard sea was more purely limestone-depositing than was the Kinkaid sea. The Menard limestone is capable of an arbitrary threefold subdivision, the lower, middle, and upper members. The upper member consists of gray and gray-black siliceous shales, and gray and dark gray calcareous shale interbedded with thin-bedded, platy, highly fossiliferous, dark gray lime- stone. In general the beds become more calcareous as the middle member of the formation is approached. The calcareous shales are usually highly fossiliferous and in places are composed of a mixture of bryozoa fragments with numerous well preserved brachiopods, pentremites, and crinoid plates, especially Pterotocrinus menardensis. As a rule the fossiliferous shale beds average about 1 foot in thickness and are rarely over 3 feet. The limestone beds also are thin, generally between 6 inches and a foot in thickness. The two detailed sections following present the upper member of the Menard at two of the best exposures observed. 52 CARBONDALE QUADRANGLE Section of the upper Menard strata exposed in the SE. y± SE. y± SW. y± sec. 28, T. 11 S., R. 1 W. Thickness Ft. In. 20. Concealed 19. Limestone, dark gray, thin-bedded (3 to 6 inches) argillaceous, with some interbedded shale; weathers slabby 1 18. Shale, thin-bedded, gray-black, siliceous 5 17. Limestone, blue-gray, shaly, highly fossiliferous 2 16. Shale, dark gray, thin-bedded, fossiliferous 1 1 15. Limestone, dark gray, shaly, fossiliferous 2 14. Shale, gray, thin-bedded, fossiliferous 4 13. Limestone, fine-grained, dark gray, partly granular, fossiliferous. .. 5 12. Limestone, gray, shaly, fossiliferous 4 11. Limestone and shale; lenses of dark gray, fossiliferous limestone interbedded with dark gray shale 8 10. Shale, gray-black, thinly laminated, fossiliferous, with thin lenses of limestone 1 8 9. Limestone, blue-gray, shaly, fossiliferous 1 1 8. Shale, dark gray, very thinly laminated, highly fossiliferous. Abundant Pentremites fohsi and some crinoids 2 7. Limestone, like No. 9 with wing plates of Pterotocrinus menar den- sis 5 6. Shale, green-gray, fossiliferous, thinly laminated 3± . . 5. Concealed 9± 4. Limestone, dense, siliceous, blue-gray, containing chert as irregu- lar nodules and numerous bryozoa; weathers brown 1 1 3. Concealed, horizontally 2. Limestone, dense, fine-grained, gray-black; with crinoidal mater- ial. Beds heavy, 8 to 20 inches thick 6 6 1. Concealed In the above section beds No. 19 to No. 6 inclusive are probably the upper portion of the Menard. The beds below are probably the middle member of the formation. Section of strata including the upper part of the Menard formation, exposed in the SE. 14 NE. 14 sec. 36, T. 11 S., R. 1 W. Thickness Ft. In. 12. Shale, buff, thin-bedded, siliceous 7 8 11. Limestone, dense, dark gray, argillaceous; weathers gray and scaly ; lenticular bed 1± 10. Shale, like No. 12 7 7 9. Limestone, dense, fine-grained, dark gray, argillaceous, with crinoidal debris common. Weathers brown 10 8. Shale and limestone; dark gray and buff -gray shale, and granular, highly fossiliferous limestone, occurring as loose blocks, but originally probably a lens or thin-bedded (partly concealed.).... 2 10 7. Concealed (a portion, at least, probably shale) 13 8 MENARD LIMESTONE 53 Section of strata including the upper part of the Menard formation, exposed in the 8E. y± NE. 14 sec. 36, T. 11 8., R. 1 W— Concluded Thickness Ft. In. 6. Limestone, fine-grained, blue-gray, in beds averaging about 7 inches thick; weathers gray (partly concealed) 2 3 5. Concealed 1 10 4. Limestone, dark gray, medium-grained 1 4 3. Limestone and shale; highly argillaceous limestone and calcareous shale 3 5 2. Limestone, medium-grained, blue-gray, fossiliferous, especially bry- ozoa , 5 1. Concealed Sandstone talus above bed No. 12 suggests the close proximity of the Palestine. However, bed No. 6 is typical Menard limestone and the beds above it are also considered as belonging probably to the upper member of the Menard rather than to the lower part of the Palestine. Because of the concealed intervals it is not possible to state which bed constitutes the prob- able top of the middle member of the Menard. Bed No. 2, however, is distinctly of the middle Menard type and this portion of the formation very probably begins with bed No. 2, if not bed No. 6. The middle member of the Menard comprises the main body of the for- mation and is essentially limestone with a few interbedded shale layers. The limestone commonly occurs in beds from 6 to 15 inches thick as observed in natural exposures. However, where the limestone has been quarried some of the beds are thicker, ranging from 3 to 5 feet, and others, particularly the more argillaceous limestones, occur in beds 1 to 4 inches thick and in some cases may be described as shelly or slabby. The bedding planes of the typical Menard limestone are usually irregular or "hummocky" and the several layers are commonly separated by a thin parting of shaly ma- terial or clay. The greater portion of the middle member is a medium- to fine-grained, locally crystalline, blue-gray or dark gray limestone. There are local rel- atively thin granular beds, but so far as was observed they maintain no persistent horizontal or vertical position. The same may be said for the chert in the Menard which occurs in small irregular nodules or lenses and is commonly gray or dark gray in color. The limestone of the middle member commonly weathers lighter than the unaltered rock. In some cases "whitewash" weathering is developed, particularly in the finer-grained, denser beds. Another rather distinctive phase of weathering which is exhibited by the Menard and also by the heavier beds of the Core, is the so-called "hour-glass" weathering (fig. 10), produced by a more rapid weathering of the central portion of a bed than 54 CARBONDALE QUADRANGLE the upper and lower parts. This phase of weathering seems to be particu- larly active on isolated masses or prominences of limestone which are sub- jected to continual or periodic stream erosion as well as weathering. As might be expected from a relatively thick limestone formation such as the Menard, limestone sinks are a common phenomenon. Locally, areas of karst topography are markedly developed, the sinks therein ranging from those 20 feet in diameter to relatively large ones 75 to 100 feet across and 20 to 30 feet deep. Sink-hole topography in the Menard limestone is well developed in the SW. J4 sec - 5, T. 12 S., R. 1 E., and in the central portion of sec. 36, the SE. ]/ A sec. 33, and the SW. y A sec. 34, all in T. 11 S., R. 1 W. The following section gives an idea of the common lithologic composi- tion of the middle member of the Menard. Section of the middle portion of the Menard formation exposed in the valley in the 8E. 14 NW. 14 sec. 34, T. 11 S., R. 1 W. Thickness Ft. In. 28. Limestone, fine-grained, blue gray, with small amounts of fossil debris replaced by crystalline calcite, giving a necked appear- ance. Weathers gray 6 27. Concealed 3 6 26. Limestone, like No. 28 but slightly lighter. Fracture irregular 8 25. Concealed 5 1 24. Limestone, medium-grained, gray-brown. Weathers gray-white.. 1 23. Limestone, fine-grained, dark gray, containing fossil fragments. Weathers gray-white 5 22. Concealed 4 5 21. Limestone, medium-grained, dark gray. Weathers brownish-gray . . 3 20. Concealed 2 11 19. Limestone, fine-grained, gray 6 18. Limestone, like No. 19, but denser 1 17. Limestone, medium-grained, crinoidal, light gray, in beds 12 to 14 inches thick. Contains irregular chert nodules 2 4 16. Limestone, dense, fine-grained, dark gray, with small masses of crystalline calcite. Weathers gray. Beds about 6 inches thick. Vertical incipient joints prominent 1 6 15. Limestone, like No. 16, but gray and argillaceous. Weathers into thin plates 6 14. Limestone, like No. 16 1 13. Concealed 7 10 12. Shale, irregularly bedded, slightly calcareous, gray-green 2 2 11. Limestone, dense, gray, very fine-grained, highly siliceous. Weath- ers brown. Has chert-like banding and fracture 1 1 10. Shale, gray, with buff-gray limestone lenses and nodules like No. 11 1 3 9. Limestone, like No. 11 3 8. Shale, thin-bedded, brownish gray, with calcareous bands 8 7. Concealed; section offset 275± feet to the south 9± MENARD LIMESTONE 55 Section of the middle portion of the Menard formation exposed in the valley in the SE. y± 2TW. !/4 sec. 34, T. 11 S., R. 1 W.— 1 Concluded Thickness Ft. In. 6. Limestone, dense, fine-grained, dark gray, locally fossiliferous. Weathers gray and brownish gray 3 7 5. Concealed 6 4. Limestone, dense, fine-grained, blue-gray, with calcite flecks. Beds 8 to 10 inches thick 3 3. Concealed ; section offset to south 17 ± 2. Limestone, medium-grained, gray or dark gray, locally granular; in heavy beds. Weathers blue-gray 5± 1. Concealed The beds described in the above section probably belong to the middle member of the Menard. The overlying Palestine is concealed but is prob- ably not more than 20 feet above the highest limestone bed. The thickness of the concealed beds where the section has been offset has been estimated on the basis of a 5° dip with a strike of about N. 70° E. measured on shale bed No. 8. The lower member of the Menard is a shale which has been observed locally below the main limestone member. Exposures of the shale are not common, as it is subject to covering by talus from the overlying limestone and rests on a relatively non-resistant formation, the Waltersburg formation. The shale has been classed as Menard because it resembles the overlying strata more than the underlying. The shale is commonly fossiliferous and calcareous, locally containing nodules or platy beds of limestone, thereby resembling the overlying beds. The underlying Waltersburg, however, so far as was observed, is free from limestone beds and is dominantly a sili- ceous formation. The two following sections give an idea of the lithologic character of the lower or shale member of the Menard and its occurrence. Section of strata including the lower shale member of the Menard formation mea- sured in the side and bottom of the valley in the NW. % SE. y± NW. ^4 sec. 6, T. 12 S., R. 1 E. Thickness Ft. In. 14. Limestone, medium-grained, gray; in beds averaging about 14 inches in thickness. Much fractured by incipient joints; weath- ers into small "peaks" with a gray-white exterior. Fossils not abundant 3 5 13. Limestone, medium-grained, blue-gray, crinoidal; in beds about 8 inches thick; weathers with a gray-brown interior and dirty gray exterior . . . 1 3 Ft. In. 3 3 1 1 7 1 4 8 4 1 3 6 56 CARBONDALE QUADRANGLE Section of strata including the lower shale member of the Menard formation mea- sured in the side and bottom of the valley in the NW. y± SE. y± NW. y^ sec. 6, T. 12 S., R. 1 #.— Concluded 12. Concealed 11. Shale, thinly laminated, buff -gray, fossiliferous 10. Limestone, medium-grained, dark gray, with specks of dark cal- cite and of crinoidal material 9. Limestone, like No. 10 but finer grained 8. Concealed 7. Limestone, dense, fine-grained, dark gray, with specks of crystal- line calcite. Beds average about 9 inches in thickness and weather gray 6. Concealed 5. Limestone, like No. 7 but lighter gray 1 4. Concealed 3 1 3. Limestone, granular, medium-grained, blue-gray; locally dense, fine-grained. Fossils common, especially bryozoa 2 8 2. Shale, soft, dark gray, fossiliferous 11 1. Sandstone, dense, gray, pyritic, resembling gray quartzite. Cal- careous and fossiliferous; brachiopods especially common 5 In the above section beds No. 14 to No. 3 inclusive are probably the middle member of the Menard, bed No. 2 a diminutive equivalent of the lower or shale member, and bed No. 1 the upper bed of the Waltersburg sandstone. Section including lower Menard strata, measured in the gully in the NW. y± NW. x /4 sec. 36, T. 11 S., R. 1 W. Thickness Feet 5. Concealed ; limestone fragments common 4. Limestone, dense, medium-grained, gray-black, in regular beds 6 to 24 inches thick, averaging about 20 inches. Weathers with a rough, "whitewashed" surface. Fossil fragments, particularly crinoid stems, common; also pentremites, bryozoa and coiled gastropods 8 3. Limestone, like No. 4 but argillaceous and in somewhat irregular beds, 6 to 10 inches in thickness. Weathers brown into slabs.... 13^ 2. Shale, laminated, calcareous, fossiliferous, with thin (3± inches) layers of interbedded limestone 5 1. Concealed; tumbling blocks of sandstone and some thin shale laminae In the above section beds No. 4 and No. 3 belong to the middle, and bed No. 2 to the lower member of the Menard. The sandstone of the covered interval, bed No. 1, is probably the Waltersburg. MENARD LIMESTONE 57 THICKNESS The thickness of the Menard may be inferred from the following: Feet. Upper member to 25 Middle member 50 to 80 Lower member to 15 Entire Menard 50 to 120 At no single exposure was it possible to measure an entire section of the Menard. Since it is doubtful if all three divisions of the formation have either their maximum or their minimum thickness at any one place, the thickness of the formation as a whole is estimated to be 80 to 110 feet. The maximum thickness is probably attained in the central portion of the quadrangle, and the minimum in the west. STRATIGRAPHIC RELATIONS As previously stated, the lithologic character of the basal Menard and upper Waltersburg is strongly suggestive of conformable relations. The contact of the Menard limestone and the Palestine sandstone is commonly concealed. The upper part of the Menard in most places con- sists of siliceous shales, calcareous shales, and thin-bedded shaly limestone in descending sequence, commonly with an increase in the calcareous con- tent of the beds as the main limestone body of the Menard is approached. Wherever the Palestine is consistently shale at its base and the Menard exhibits the above indicated sequence, the suggestion is a gradual transition in the character of the sea from sandstone to limestone depositing. It is doubtful, however, if the Menard does have a shale and limestone sequence in its upper portion everywhere in the quadrangle ; in fact, it is quite prob- able that in places the upper shaly portion is missing, or at least thin and inconspicuous. From the evidence of the exposures in the Carbondale quadrangle, the Menard and Palestine locally seem to be conformable, while in other places the rather abrupt change from arenaceous to calcareous sediments suggests a disconformity or erosional unconformity. PALEONTOLOGY The fauna of the Menard limestone is an extensive one, as practically all of the limestone beds and some of the shales are fossiliferous. In the case of the medium- or fine-grained limestones of the middle member, the bond between the embedded fossils and the matrix is so strong that com- plete specimens are obtainable only with difficulty. The thin shaly beds, however, particularly those of the upper member, yield numerous excellent specimens. 58 CARBONDALE QUADRANGLE Of the diversity of forms in the Menard, Pentremites fohsi, and Ptero- tocrinns menardcnsis are the most diagnostic. These when found with Sulcato pinna missonriensis, Allorisma clavata, Spirifer increbescens and Composita sub quadrat a are sufficient to establish the Menard. In addition the formation commonly contains numerous bryozoa (especially Fenestella and Archimedes), Spiriferina transversa, and 6\ spinosa, Orthotetes kaskas- kiensis, Cliothyridina siiblamcllosa, Diaphragmus elegans, Eumetria costata and Productus ovatus. CORRELATION The Menard limestone was originally described in Randolph County as the formation occupying the interval between the top of the Okaw lime- stone and the base of the Palestine sandstone. This interval when traced across to southeastern Illinois included one limestone and two sandstone formations, which were not represented in the western Illinois section. It therefore seemed feasible to distinguish these three new members in the southeastern Illinois Glen Dean- Palestine interval and they accordingly have been given the names Waltersburg sandstone, Vienna limestone, and Tar Springs sandstone in descending order. This fourfold subdivision of the Okaw-Palestine interval is recognized in the Carbondale quadrangle and the geologic mapping has therefore been done on that basis. The Menard in this area has been correlated with that of the type locality because of its similar fauna and its position immediately below the Palestine sandstone. PALESTINE SANDSTONE NAME AND DISTRIBUTION The Palestine sandstone has been named from exposures in Palestine Township, Randolph County, Illinois. Its outcrop roughly parallels that of the underlying Menard limestone and the overlying Clore formation (see Plate I). The major outcrop begins in sec. 4, T. 12 S., R. 1 E., with a width of about an eighth of a mile and extends northwest to the large hill in sec. 32, T. 11 S., R. 1 E., with exposures at intervals in the gullies along the east valley-slope of Bradshaw Creek. Following southwest along the base of the hill in sees. 31 and 32, the outcrop band narrows a little but widens abruptly to about % mile where it turns northwest around the west end of the hill. Good exposures are rare along the base of the hill due to the concealing talus, but do occur in the gullies just west of the road in the NW. ]/ A sec. 31, T. 11 S., R. 1 E., and in the E. y 2 SE. % sec. 25, T. 11 S., R. 1 W. Northwest from this last place the band of outcrop is di- vided by a hill whose upper slopes are Clore limestone and shale, but re- unites in the SE. *4 sec - 24, T. 11 S., R. 1 W., with good exposures in the PALESTINE SANDSTONE 59 east-west creek in the N. y 2 SE. yi of the section. From sec. 24 the out- crop turns west and a little south for about V/2 miles, then turns south- west to sec. 34, T. 11 S., R. 1 W., and finally northwest, off the edge of the quadrangle, following along the middle slope of the Pottsville-Degonia cuesta with incomplete exposures in the gullies intersecting it, and a band of outcrop which widens or narrows with the decrease or increase of the topographic slope. LITHOLOGIC CHARACTER The Palestine formation is for the most part a thin- or medium-bedded sandstone, with local beds of shale, highly siliceous limestone and calcareous sandstone. Where the formation is best exposed there seems possible a rough two- fold division into the upper and lower Palestine. The upper part consists of a thin-bedded, micaceous sandstone with very uneven bedding planes whose surfaces exhibit the irregular ripple marks similar to those to be described for the Degonia sandstone. This portion also contains cal- careous sandstone and locally considerable dark gray or gray-black shale composed of very fine particles of silica, and in places including small amounts of carbonaceous material as indistinct plant tracings or thin part- ings, or as irregular small masses of coaly material. Sections to be given in the description of the Clore limestone illustrate the general lithologic character of this upper portion. The lower part of the formation consists largely of sandstone, gray or buff when fresh, but red-brown or yellow-brown when weathered. It occurs in beds 1 to 12 inches thick, with the thinner beds toward the top portion and the thicker beds toward the bottom, and between the two extremes a gradual, though by no means constant progression from the thin to the thicker beds. The sandstone of this lower portion of the Palestine is com- monly micaceous and fine- to medium-grained, with the coarser sand in the heavier beds. Ripple marks are common along the bedding planes and are fairly well marked. The following section indicates the general character of the lower part of the Palestine. Section including the lower part of the Palestine from exposure at the lower end of the gully in the NE. 14 SW. % 8E. 14 sec. 31, T. 11 8., R. 1 E. Thickness Ft. In. 4. Concealed 3. Sandstone and sandy shale, thin-bedded (1 to 2 inches), fine- grained; gray micaceous sandstone interbedded with very mi- caceous platy shale composed of very fine sand particles. Beds 1/16 to y 2 inch thick. Carbonaceous material common along bedding planes 10 1 2. Concealed, lower portion probably shale 6 4 1. Limestone, dense, fine grained, dark gray, argillaceous, with a dull luster. Weathers gray and scaly 1 3 60 CARBONDALE QUADRANGLE In this section, bed No. 1 is Menard and bed No. 3 and possibly bed No. 2, the lower portion of the Palestine. In a few localities where the beds below the heavier sandstones of the Palestine were observable, there are in some instances a few feet of mica- ceous, sandy shale. THICKNESS No opportunity was afforded to measure the entire thickness of the Palestine sandstone at ony one place. It is probable, however, that the for- mation varies between 35 to 50 feet in thickness and averages about 40 feet. STRATIGRAPHIC RELATIONS The relations between the Palestine and the overlying Clore formation are, where observable, conformable. The transition is a gradual one from sandstone to sandy shale, to shale, followed above by the diverse sequence of Clore beds. As discussed under the Menard limestone, the contact of the Palestine with the underlying Menard is probably conformable in some places and unconformable or disconformable in others. PALEONTOLOGY The Palestine sandstone is practically barren of organic remains ex- cept for occasional fragments of Lcpidodcndron trunks. The black carbon- aceous partings and markings along the bedding planes of some of the thin- bedded, micaceous sandstones, in some cases resemble plant markings, but they are so indistinct as to be unidentifiable. CORRELATION The correlation of the Palestine sandstone of the Carbondale quad- rangle with that originally described in Randolph County is based upon its corresponding stratigraphic position and similar lithologic characteristics. CLORE FORMATION NAME AND DISTRIBUTION The Clore formation is named after Clore School, at the type locality in Randolph County, Illinois. The formation was originally considered the highest Chester formation exposed in this State, and wherever the Degonia and Kinkaid formations were present they were included with it. Later work has demonstrated the feasibility of separating the Degonia and Kin- kaid as distinct formations from the Clore, and this subdivision has been adhered to in the mapping of the Carbondale quadrangle. The main outcrop of the Clore formation begins in sec. 4, T. 12 S., R. 1 E., near the center of the south line of the quadrangle, and extends northwest into sec. 32, T. 11 S., R. 1 E., where the outcrop turns northeast CLORE FORMATION 61 for about a mile and then approximately northwest again, with a departure from the general trend by a band of outcrop which follows around a large hill in sees. 32 and 33, T. 11 S., R. 1 E. This hill and its vicinity show some very good exposures of the Clore and also the maximum thickness exhibited in the quadrangle. The outcrop of the formation reaches its northernmost extent in sec. 24, T. 11 S., R. 1 W., and from this place trends southwest to sec. 34 as a narrow band ; thence west and north again, through the town of Cobden to Drury Creek ; north along the creek to sec. 20 ; and then up a tributary valley to the west and beyond the margin of the quad- rangle. Other small outcrops of Clore outside the main band occur as follows: In the northeast-flowing creek in the N. ]/ 2 sec. 28, T. 11 S., R. I W., there is a small but good outcrop of Clore along the creek for about half a mile. In sec. 3, T. 12 S., R. 1 E., the Clore is exposed in the slopes and ravines of the valley extending northwest from the southeast corner of the section. Still other exposures of the Clore occur at intervals in the west valley-slope of Lick Creek in sec. 1, T. 12 S., R. 1 E., and sec. 36, T. II S., R. 1 E., and in the tributary valleys from the west in sees. 1 and 2, T. 12 S„ R. 1 E., and sec. 35, T. 11 S., R. 1 E. In general the outcrop band of the Clore formation is narrow, on the average perhaps less than a tenth of a mile. The maximum width main- tained for any distance is reached in sees. 30, 31, and 32, T. 11 S., R. 1 E., where the Clore outcrop area is from an eighth to a sixth of a mile wide. The narrowness of the outcrop band of the formation is due to two things. The first is the relative thinness of the formation. It varies from 20 to 80 or more feet but is commonly nearer the former than the latter thickness. The second consideration has to do with the topographic effect of the overlying Degonia. The Clore itself is not a resistant forma- tion, but the overlying Degonia sandstone which is resistant acts as a pro- tective cap over the Clore, and as a result, cuesta-bordered flats and table lands are formed. Thus, the outcrop of the relatively thin Clore formation on the comparatively steep cuesta-slopes is of necessity a narrow one. LITHOLOGIC CHARACTER The Clore formation is a variable succession of shale, shale with thin limestone beds, argillaceous limestones, and locally some sandstone. No bed or horizon was found which holds a consistent position, but the thicker limestone beds and the bulk of the limestone commonly occur in the upper portion of the formation. Those limestones of the Clore which occur in beds over a foot thick are commonly fine- or medium-grained, dense, gray, blue-gray, or gray- black, argillaceous limestones flecked with small masses of crystalline calcite. "Hour glass" weathering is common (fig. 10). Fossils, except bryozoa, are 62 CARBONDALE QUADRANGLE relatively rare in these beds although specimen of Salcatopinna missouri- ensis and Allorisma clavata are often found in this dense limestone. The abundantly fossiliferous portion of the Clore formation is that comprising the thin-bedded limestones and the commonly associated interbedded shales. This succession which shows sediments ranging from a true coarse-grained or granular limestone to shaly limestone, calcareous shale, and true shale, is replete with fossils of many kinds. Of special note is the presence of great numbers of Batostomella nitidula in these beds. Pig. 10. "Hour glass" weathering of Clore limestone. SW. % NW. % sec. 34, T. 11 S., R. 1 W. The maximum and best exposure of a single limestone unit observed in the Clore formation was that in a sink hole just north of the road in the SW. y A SE. ]/ A SE. y A sec. 29, T. 11 S., R. 1 W., where about 7 feet of limestone is exposed in beds 6 to 14 inches thick without shale partings. Another, but less continuous section is observable in the center of the N. y 2 sec. 28, T. 11 S., R. 1 W. (See the section given under the discussion of the stratigraphic relations of the Clore formation.) The following section shows a typical Clore succession of limestones and shales : CLORE FORMATION 63 Section of Begonia, Clore, and Palestine strata exposed in the gully along the ivest line of the NW. y± sec. 3^, T. 11 S., R. 1 W. Thickness Ft. In. 30. Sandstone, fine-grained, gray-white; in beds V 2 to 3 inches thick.. 2 + 29. Concealed 2 8 28. Shale, gray-black, thin-bedded, siliceous 6 27. Concealed 4 7 26. Shale, buff, sandy, with beds of very fine-grained, shaly sandstone 2 25. Concealed 3 24. Limestone, medium-grained, gray and dark gray, fossiliferous; in beds about 9 inches thick. Weathers brown and with hour-glass effect 2 9 23. Concealed 5 22. Shale, thin-bedded, plastic, gray. Weathers to a gray-green clay 1 7 21. Limestone, dense, fine-grained, finely crystalline, dark gray. Weathers buff and with hour-glass effect 1 10 20. Limestone, thin-bedded, dark gray, shaly, grading into calcareous shale below. Weathers brown. Partly concealed 2 2 19. Shale, soft, slightly plastic, dark gray, siliceous 12 9 18. Limestone, like No. 11, but slightly lighter colored 2 2 17. Shale, thin-bedded, calcareous, buff -gray, fossiliferous 1 8 16. Limestone, dense, very fine-grained, gray-black, fossiliferous.... 1 4 15. Limestone, thin-bedded, gray-black, shaly, grading into shale at base. Highly fossiliferous 1 3 14. Shale, gray-black, thinly laminated, siliceous 8 2 13. Limestone, badly rotted, argillaceous, brown, in thin beds. Batos- tomella nitidula abundant 8 12. Limestone and shale; thin-bedded, gray-black, highly fossilifer- ous limestone, interbedded with fossiliferous gray shale 1 4 11. Limestone, fine-grained, dark gray, in beds about 3 inches thick. Weathers brown. Locally the bed contains much fossil debris and many fossils which make it granular in appearance. 8 10. Limestone and shale; buff shale with lenticular beds of limestone like No. 11, and nodules of very dense, dark gray limestone. Shale is irregularly bedded and calcareous. All beds fossilifer- ous except nodules 3 5 9. Limestone like No. 11 7 8. Shale, buff, thin-bedded 9 7. Concealed 1 8 6. Shale, gray, thin-bedded, micaceous, sandy, with sandstone layers % to x k inch thick 4 5 5. Concealed 1 11 4. Sandstone, thin, irregularly bedded, buff, micaceous 5 5 3. Shale, fine-grained, micaceous, gritty, gray -black 3 5 2. Concealed 5 4 1. Sandstone, medium-grained, buff; in beds 6 to 12 inches thick. Grains rounded to sub-angular 9 10 64 CARBONDALE QUADRANGLE In the above section beds No. 26 to No. 30 are Degonia, No. 24 to No. 8 Clore, and No. 6 to No. 1 Palestine. The shales of the Clore, like the rest of the formation, show a wide variation. Some are composed of very fine particles of silt, others are sandy shales, and still others are calcareous. Of particular note are the plastic or "fat" shales, which are commonly quite free from grit. The plasticity of these shales seems in some cases to be due to an inherent prop- erty of plasticity. In the case of the calcareous shales, however, weathering and leaching are doubtelss effective in developing this property. In places it is common to observe as the only evidence of the presence of the Clore in the vicinity, a plastic, buff-gray clay streaked with limonite stains and within it rounded fragments of limestone which a brown weathered crust about half an inch thick. The Clore shales, especially the coarser silt and sandy shales, not uncommonly contain flakes of mica and also thin carbon- aceous markings or laminae. The shaly character of the Clore is well shown in the following section : Section of the Begonia and Clore strata exposed in the gully crossing the road in the NW. V± 8E. *4 SW. V± sec. 20, T. 11 S., R. 1 W. Thickness Ft. In. 11. Sandstone, fine-grained, thin-bedded (2 to 6 inches), buff-gray.... 20± 10. Shale, green-gray, brown, and gray, with ferruginous bands and large nodules of dense, gray limestone and porous brown and black clayey material, probably "rotted" carbonaceous limestone. 2 9 9. Shale, black, siliceous; breaks into irregular fragments with con- cave faces 2 6 8. Limestone, dense, semi-lithographic drab-gray, with a dull lustre. Small cavities lined with calcite and pyrite. Weathers buff. ... 1 10 7. Shale, dark gray, thinly laminated, slightly plastic 2 1 6. Concealed 5 1 5. Shale; greenish-gray, plastic, clay-shale, with lenses of medium- crystalline, blue-gray, fossiliferous limestone which weathers brown 5 6 4. Concealed 2± 3. Shale, gray, siliceous; and interbedded buff-gray, micaceous sand- stone with carbonaceous markings 2 4 2. Concealed 1 3 1. Shale, drab-gray, soft, plastic clay-shale. Bedding distorted. Con- tains a few fossils and sand grains 2 3 Bed No. 11 is Degonia, beds No. 1 to No. 8 Clore, and beds No. 9 and No. 10 probably Clore or transition sediments. Sandy shales are not uncommon in the Clore formation of the Carbon- dale quadrangle but distinct sandstone beds are unusual and occur only where the Clore is the thickest. They are well exposed in the northeast side Thickness Ft. 7w. 4 + 7 6 6 2 9 4 2 9 2 2 14 6 CLORE FORMATION 65 of the valley of Bradshaw Creek in sees. 30 and 31, T. 11 S., R. 1 E., and also less perfectly in the valleys on the sides of the large hill in sees. 31 and 32 of the same township. The exposure in sec. 30 is as follows : Section of Clore strata measured in the gully just southeast of the road down the northeast side of the valley of Bradshaw Creek in the 28. Sandstone, fine-grained, dense, earthy in appearance, irregularly bedded 27. Concealed 26. Limestone, dense, fine-grained, dark gray; with crystals of dark calcite 25. Concealed 24. Limestone, like No. 26 23. Concealed 22. Limestone like No. 26, but somewhat lighter gray with more crys- talline calcite. Fossil debris and small fossils, especially bry- ozoans, common 21. Concealed ; probably partly gray shale 14 20. Limestone, dense, fine-grained, light gray, with a sharp, rough fracture. Weathers gray and brown, with a pitted rounded ex- terior. Fossils common, especially bryozoans and brachiopods, locally replaced by calcite 4 6 19. Concealed ; probably shale 2 11 18. Limestone, medium-grained, gray-black 8 17. Sandstone, fine-grained, buff, in beds 14 to 3 inches thick. Beds fairly regular. Ripple marks common 2 9 16. Shale, irregularly bedded, locally plastic, gray-black, with inter- bedded gray sandstone lenses at top, grading into siliceous, gray- black, thinly laminated shale below 15. Concealed ; probably shale 14. Limestone, dense, fine-grained, dark gray, shelly 13. Concealed ; probably gray shale 12. Limestone, dense, medium-grained, gray-black, locally crinoidal. . 11. Concealed 10. Shale, green-gray, and buff; locally calcareous in regular beds Vs to % inches thick 9. Concealed 8. Sandstone, fine-grained, mottled buff, in beds 6 to 10 inches thick. Sand grains rounded to subangular. Sigillaria common 5 7 7. Sandstone, fine-grained, micaceous, dense, buff-gray, in beds 6 to 8 inches thick; interbedded with thin irregular beds of micaceous sandstone. The heavier beds weather to slabs 1 to 2 inches thick and are conspicuously ripple-marked 3 1 6. Concealed 14 1 5. Limestone, dense, very fine-grained, very finely crystalline, dark gray. Fossils, especially brachiopods, common. Weathers to thin 4 8 2 6 3 2 1 7 6 1 11 10 4 66 CARBONDALE QUADRANGLE Section of Clore strata measured in the gully just southeast of the road down the northeast side of the valley of Bradshaw Creek in the SW. ^ sec. 30, T. 11 8., R. 1 #.— Concluded Thickness Ft. In. plates, and locally develops the "hour-glass" effect 5 4. Shale, compact, thinly laminated, gray-black, siliceous 1 3 3. Concealed 7 2. Shale, compact, thin-bedded, dark gray, fossiliferous. Brachiopods and pelecypods (Leda sp.) about *4 inch in length numerous... 3 1 1. Concealed In the above section bed No. 28 is Degonia and the remainder of the section Clore. THICKNESS The thickness of the Clore formation varies from about 20 to about 95 feet but is most commonly approximately 30 feet. The minimum thickness occurs in the west valley-slope of Lick Creek and the valleys tributary there- to in sec. 35, T. 11 S., R. 1 E., and sees. 1 and 2, T. 12 S., R. 1 E. The maximum is reached in sees. 30, 31 and 32, T. 11 S., R. 1 E., with a decrease toward the average thickness to the northwest and southeast. The greatest exposure of the Clore is found in the gully in the SE. l /\. SW. ^4 sec - 30, T. 11 S., R. 1 E., previously described, where 88 feet of Clore is present and possibly more as the section does not reach the top of the Palestine sandstone. The formation as a unit, omitting the exceptions noted, probably has a fairly constant thickness of about 30 feet, especially in the western half of the quadrangle. The following section gives an idea of the lithologic composition of the Clore formation at an exposure of about average thick- ness: Section of Begonia, Clore and Palestine strata measured in the gully in the SW. y± NE. % SE. y± sec. 4, T. 12 S., R. 1 E. Thickness Ft. In. 14. Sandstone, thin-bedded (y 2 to 3 inches), buff and gray, micaceous, grading into shaly sandstone at base 6+ 13. Concealed 5± 12. Limestone, dense, argillaceous, gray-black, in beds about 1 foot thick. Weathers gray and blue-gray. A few large fossils 2 1 11. Shale; soft, gray, plastic, calcareous clay-shale. Partly concealed .. 11 10. Limestone, like No. 12 1 10 9. Concealed; probably limestone and shale 5 6 8. Shale, dark gray, siliceous. Outcrop much weathered and slumped. Partly concealed 7 7 7. Concealed 7 6. Shale and limestone; thinly laminated, dark gray shale with ir- regular nodular beds of dense, gray limestone, like No. 12 8 9 CLORE FORMATION 67 Section of Begonia, Clore, and Palestine strata measured in the gully in the SW. % NE. 14 SE. % sec. 4, T. 12 S., R. 1 E— Concluded Thickness Ft. In. 5. Sandstone, dense, fine-grained, blue-gray, calcareous, in beds y 2 to 2 inches thick 1 5 4. Sandstone, thin-bedded (% to y 2 inch), gray, micaceous, and sandy shale 2 6 3. Concealed 4 9 2. Limestone, dense, gray-black, highly siliceous, locally granular.. .. 4 1. Concealed ; probably shale Bed No. 14 is Degonia, beds No. 12 to No. 6 inclusive Clore, and No. 5 to No. 1 Palestine. Bed No. 5 may, however, be considered as transitional from the Clore to the Palestine. STRATIGRAPHIC RELATIONS The Clore formation is conformable with the Degonia sandstone above and the Palestine sandstone below. The upper contact is a transitional one, commonly from limestone to shale, to sandy shale, and finally to sandstone, although the intermediate shale and sandy shale is not everywhere present. The following section as well as foregoing sections of the Clore gives the details of the transitional relations : Section including the contact of the Clore and Degonia formations, measured in the gully in the center of the N. y 2 sec. 28, T. 11 S., R. 1 W. Thickness Feet 4. Sandstone, medium-grained, buff, in beds 3 to 8 inches thick 15 + 3. Sandstone and shale, interbedded. Sandstone like No. 4 and shale like No. 2 y 2 2. Shale, largely black and gray-black, thinly laminated. Contains nodules of dense, calcareous black shale or highly argillaceous limestone. Basal portion of exposure, buff 8± 1. Limestone, fine-grained, dense, gray and gray-black, in beds 8 inches to 2y 2 feet thick. Fossils not prominent. Weathers gray-white and brown 20±: In the above section bed No. 4 is Degonia, No. 1 is Clore, and Nos. 2 and 3 transition beds, although No. 2 may well be classed as upper Clore. PALEONTOLOGY The shaly beds of the Clore furnish an abundance of fossils, most of which are common to the upper Chester as a whole. The outstanding forms are Composita sub quadrat a, Spirifer increbescens, Productus (probably arkansanus) , Orthotetes kaskaskiensis, Cliothyridina sublamellosa, numer- our bryozoa and a few of the more typical Menard fossils, Sulcatopinna missouriensis, and Allorisma clavata. The association of the first three 68 CARBONDALE QUADRANGLE mentioned forms with numerous Batostomclla nitidula is characteristic of the Clore in southern Illinois. Scattered specimens of the last-mentioned bryozoan may possibly be present in the Menard limestone, but its presence in numbers thickly distributed over the surfaces of the limestone layers and intermixed with the fossils and fossil debris forming the calcareous shales, is a phenomenon of distinctly Clore aspect. CORRELATION The Clore formation is traceable with a few interruptions across south- ern Illinois, and its stratigraphic position is thereby fairly well established. In addition the fauna and general lithologic character of the Clore in the Carbondale quadrangle are similar to those of the formation at its type locality in Randolph County. DEGONIA SANDSTONE NAME AND DISTRIBUTION The Degonia sandstone receives its name from Degonia Township in Jackson County, Illinois, where it is well exposed in the Mississippi River bluffs and the valleys incident thereto. In the Carbondale quadrangle, the Degonia sandstone outcrops over a greater area than any of the other Chester formations. This is due to the fact that the sandstone caps two rather large flats and also to the thickness and general resistance of the formation to erosion. Like the other thick Chester sandstones, the Degonia forms marked bluffs or terraces (fig. 3) under the proper conditions and stands in almost sheer faces 30 to 50 feet high. Especially is this so where the Kinkaid limestone is thin and the scarp-forming effect of the Lick Creek member of the Pottsville is partly shared by the Kinkaid. Such conditions and scarps occur in sees. 23, 26 r and 27, T. 11 S., R. 1 W. The outcrop of the Degonia sandstone (see Plate I) begins at the south edge of the quadrangle as an irregular band about 3 miles wide and extends northwest, gradually narrowing until in sec. 19, T. 11 S., R. 1 E., its area of outcrop is but little over half a mile in width. From here the band of exposure widens and turns sharply to the southwest, beginning with the width of about \y 2 miles and gradually narrowing to a scant J /$ mile in sees. 26 and 27, T. 11 S., R. 1 W., where the sandstone forms steep bluffs. From sec. 27 the area of outcrop widens abruptly to 2 and 2 l / 2 miles and so continues beyond the west edge of the quadrangle. The irregularity of the band of outcrop of the Degonia sandstone is due to the fact that it caps the higher land into which valleys have been cut through the sandstone and have exposed narrow tongues of older for- mations extending into the Degonia outcrop area. Other interruptions are DEGONIA SANDSTONE 69 produced by isolated hills of Kinkaid and of Kinkaid and Pottsville which stand above the general Degonia level. LITHOLOGIC CHARACTER The Degonia sandstone, particularly as exposed in the western part of the Carbondale quadrangle, resembles the Tar Springs sandstone more than any other Chester formation exposed in the area. It is also very like portions of the Pottsville which are not conglomeratic, and where the two formations are in juxtaposition they are difficult to distinguish. The De- gonia, particularly that of the western part of the quadrangle, seems to lend itself in a general way to a threefold division, namely an upper thin-bedded member, a middle massive member, and a lower thin-bedded shaly member. The upper thin-bedded member is the most variable of the three. In places it is apparently absent, but is sufficiently common to warrant separate consideration. It is well exposed in the gullies in the S. ^2 sec. 29, T. 11 S., R. 1 E., and in the SW. cor. and also the SE. % sec. 27, T. 11 S., R. 1 W., along the roads and in the higher portions of the gullies. A specific section in the latter vicinity is as follows : Section of Kinkaid and Begonia strata exposed at the center SW. y± SW. y± sec. 27, T. 11 S., R. 1 W. Thickness Feet Kinkaid — 4. Limestone, dense, gray-black, with interbedded buff and yellow shale. Solution of limestone has produced small sinks in which copious Pottsville sandstone talus has accumulated . . ? 3. Concealed ? Degonia (Upper thin-bedded member) — 2. Sandstone, buff-gray and white, irregularly bedded, fine-grained, grains angular to subangular, in beds % to 6 inches thick. White mica common, particularly along bedding planes. Some beds weather to thin sheets from *4 to % inches thick, and show copious mica, as well as red iron-staining in con- junction. Particularly in the upper portion of the exposure, the sandstone contains thin discoidal clay inclusions, which give the brown weathered surface a pitted or pock-marked appearance 17 Degonia (Middle massive member) — 1. Sandstone, fine-grained, white to buff, heavy-bedded (3 to 24 inches, average 10 inches), beds irregular, but not cross- bedded. Grains angular to subangular. Weathers brown.... 17 + 70 CARBONDALE QUADRANGLE A gully in sec. 22, T. 11 S., R. 1 W., with a direction south and south- east, gives another splendid exposure of the Degonia as follows : Section of Degonia strata exposed in a gully in the SW. y± 8E. y± sec. 22, T. 11 &., R. 1 W. Thickness Feet Degonia (Upper member) 5. Sandstone, white, fine-grained, with angular grains; weathers gray-buff. Bedding very irregular; weathers to thin irreg- ular slabs y 2 to 8 inches thick. Cementation firm. Ripple marks, generally small, about 2y 2 inches from crest to crest 29 4. Sandstone, fine-grained, white, grains angular. Weathers buff and into thin regular slabs 1 to 3 inches thick 12 (Middle bluff-forming member.) 3. Sandstone, medium-grained, buff-gray or gray, in massive beds 1 to 2 feet thick. Grains are rounded to subangular. Weathers buff color with beds 3 to 8 inches thick. Cross-bedding com- mon, ripple marks small and not marked 40 2. Concealed 14 Clore— 1. Limestone, dense, fine-grained, gray-black. Contains small masses of gray or brown crystalline calcite. Fossils rare, beds about 10 inches thick 1% It is to be noticed that the thin-bedded, micaceous sandstone is not well developed in this section. In its place, however, is a 41-foot sandstone stratum which weathers to thin beds and may be considered a rough equiv- alent of the micaceous sandstone. As a rule, where the micaceous upper sandstone of the Degonia is well developed its thickness is 20 to 30 feet. The middle massive member of the Degonia, because of its bluff- forming characteristic, is the most commonly exposed portion of the sand- stone and also topographically the most expressive. Its general character and position are shown in the preceding sections. Additional good exposures may be seen along the bluff already mentioned in sees. 23, 26, and 27, T. 11 S., R. 1 W., and in the valleys in sees. 17, 20, 21 (especially in the east-west creek in the S. J4), 28, and 29 of the same township. This massive middle member of the Degonia, where prominent, is from 35 to 50 feet thick. An- other section which shows the general relations of the bed to the rest of the formation is as follows : DEGONIA SANDSTONE 71 Section of the Begonia formation exposed in the NE. % SE. y± SW. y± sec. 21 y T. 11 8., R. 1 W. Thickness Degonia— Ft. In. 5. Sandstone, fine-grained, light buff, in thin slabby beds, y 2 to 4 inches thick. Grains rounded to subangular. Weathers brown 5± 4. Sandstone, medium-grained, light buff, in beds 3 to 12 inches thick, averaging about 9 inches. Bedding irregular with lo- cal cross-bedding. Weathered surface badly pitted and iron- stained. Fossil plant remains fairly common 22 3. Sandstone, medium-grained, light buff, in massive beds 2 to 8 feet thick with a few thinner beds 3 to 8 inches thick. Grains rounded to subangular. Weathers brown and is iron-stained, especially along bedding planes. Cross-bedding not promi- nent. Cementation loose 60 2. Sandstone, thin-bedded, buff, platy 1 Clore — 1. Shale and limestone; much-weathered, yellow and gray shale, with loose blocks of shaly limestone. Exposed at intervals.. 5± In this section beds No. 4 and No. 5 are the upper member, bed No. 3 the middle massive member, and bed No. 2 a poorly developed equivalent of the lower thin-bedded member of the Degonia. The lower portion of the Degonia consists largely of sandstone in beds 3 to 8 inches thick, underlain by thin-bedded, micaceous sandstone or sandy shale, or by black siliceous shale. The last two phases are commonly ob- served close to the Clore-Degonia contact, and at the five observed contacts the Clore limestone was overlain by shale, followed above by sandstone. Where it is well developed, the lower member of the Degonia probably has a thickness of 15 to 35 feet. The relations of the lower Degonia and the underlying Clore are illustrated by the following section. Section including the transition oeds oetween the Degonia and the Clore, measured in the gully in the NW. corner SW. y* sec. 33, T. 11 S., R. 1 E. Thickness Degonia — Feet 20. Sandstone, fine-grained, buff; in regular beds 1 to 4 inches thick. Slightly micaceous. Contains a few fossil forms such as Spirifer increoescens and Archimedes 3 + Transition beds — 19. Limestone, medium-grained, granular, very sandy, fossilifer- ous, with small masses of carbonaceous material 1 3 18. Sandstone, thin-bedded, fine-grained 3 17. Limestone, dense, medium-grained, blue-gray, with inclusions of carbonaceous material. Weathers brown 6 16. Sandstone, fine-grained, buff, mottled brown, in thin slabby beds 5 72 CARBONDALE QUADRANGLE Section including the transition beds between the Begonia and the Clove, measured in the gully in the NW. corner SW. y± sec, 33, T. 11 S., R. 1 E. — Concluded Thickness Ft. In. 15. Limestone, medium-grained, blue-gray; weathers brown. Small inclusions of carbonaceous material 1 3 14. Sandstone, medium-grained, gray, slabby 4 13. Limestone, like No. 15 5 12. Sandstone, fine-grained, brown 1 11. Limestone, medium-grained, gray, granular, very sandy, lo- cally fossiliferous and cross-bedded. Weathers brown with a rugose surface. Carbonaceous material replaces indistinct- ly some of the fossils 3 4 10. Concealed 10 9. Sandstone, fine-grained, buff, micaceous, in beds 2 to 6 inches 2 3 8. Sandstone, fine-grained, gray, micaceous, with indistinct car- bonaceous plant markings. Splits to sheets about x /± inch thick 2 8 7. Sandstone and shale; gray-black, thinly laminated, siliceous shale with bands of pyrite nodules, grading upward into sandy shale and finally thin-bedded shaly sandstone 11 6. Concealed 3 Clore — 5. Limestone, dense, fine-grained, gray-black, with small dark calcite crystals. Beds 6 to 12 inches thick. Weathers gray to thin scaly plates 1 6 4. Concealed ; probably shale 1 3. Limestone, dense, fine-grained, gray-black, argillaceous. Beds 6 to 10 inches thick, but weather to slabs V^ to 1 inch thick 4 6 2. Shale, thinly laminated, gray-black 1 6 1. Concealed Ripple marks are common throughout the Degonia sandstone, par- ticularly the anastomosing type. This type of current ripple marks is most common in the thinner-bedded members. Non-branching current ripple marks are also common, particularly in the beds of the formation more than 2 inches thick. The largest ripple marks of this sort noted were 9 inches from crest to crest and l}i inches in height. Considering the formation as a whole, cross-bedding is not prominent. It is most commonly developed in the middle coarser-grained thicker-bedded portion of the Degonia, indicating presumably that the sand forming this part of the formation was dropped by relatively strong currents while the finer sediments of the upper and lower portions were, in general, deposited from relatively quieter water. THICKNESS The Degonia sandstone exhibits a maximum thickness of about 125 feet in the Carbondale quadrangle. From this maximum, reached in the DEGONIA SANDSTONE 7:^ western portion of its belt of outcrop, it thins gradually to the east and probably reaches a minimum thickness of about 60 feet in the vicinity of Lick Creek. The decrease in the thickness of the formation is probably largely due to a decrease in the thickness of the middle massive and the lower thin-bedded members. STRATIGRAPHIC RELATIONS As shown in the preceding sections the relations of the Degonia to the Kinkaid limestone above and the Clore limestone below are generally con- formable. The contact of the Kinkaid and Degonia was rarely observed, Fig. 11. Contact of Degonia shale and sandstone and Kinkaid limestone on Drury Creek in NW. 14 NW. }i sec. 16, T. 11 S., R. 1 W. Note the ground water channels in the limestone. but from the data available it is thought to be conformable in places and disconformable in others. Figure 11 is a photograph of the contact of the Degonia and Kinkaid as exposed in sec. 16, T. 11 S., R. 1 W. PALEONTOLOGY The Degonia sandstone is not commonly fossiliferous, but locally it con- tains a few fragmentary Lcpidodendron trunks and plant stems. The most numerous specimens were noted near the center of the S. ^2 sec. 27, T. 11 S., R. 1 W., in the bed about 60 feet above the Clore limestone. 74 CARBONDALE QUADRANGLE CORRELATION The Degonia sandstone is correlated with that of the type locality in Jackson County, on the basis of its stratigraphic position. KINKAID LIMESTONE NAME AND DISTRIBUTION The Kinkaid limestone is the highest Chester formation exposed in the Carbondale quadrangle, and receives its name from exposures along Kinkaid Creek in Jackson County, where it was originally described. The outcrop of this limestone is practically continuous across the en- tire southern portion of the quadrangle (see Plate I). In the southeast corner of the quadrangle the outcrop appears as a band from one-eighth to a quarter of a mile wide and extends northwestward toward Lick Creek, following below the outcrop of the Pottsville sandstone and with the gen- eral trend of the topography. The Kinkaid is commonly found exposed in steep hillsides abundantly scattered over with Pottsville talus, though in places where the Pottsville and Degonia are both exposed in the same slope it forms flats (fig. 3). In the vicinity of Lick Creek and thence northwest to sec. 19, T. 11 S., R. 1 E., the Kinkaid has a larger band of outcrop which varies from 1 to % l / 2 miles in width. This broader band is due to less pronounced stream erosion against the Pottsville scarp and to the fact that the underlying De- gonia sandstone caps a plateau-like stretch of country over which the Kin- kaid partially extends as a series of ridges with prominent knobs, some of which are capped with Pottsville sandstone. Continuing northwestward the band of outcrop narrows. In sec. 12, T. 11 S., R. 1 W., a fault interrupts and offsets it to the north, and produces thereby a triangular area of outcrop. From there the formation thins to the southwest and continues as an irregular but gradually narrowing band to the SE. ]/ A sec. 28, T. 11 S., R. 1 W., and then north to the SE. y A sec. 21, where, for a distance of about half a mile, it pinches out entirely or is a very thin bed not exposed at the surface. The limestone continues exposed northwest of sec. 21 as a narrow band extending along Drury Creek into the middle of the W. y 2 sec. 5, T. 11 S., R. 1 W., and from there almost due west to the edge of the quadrangle. It is probably absent from the ridge in the NW. y A sec. 20, T. 11 S., R. 1 W. East and northeast of Cobden, the limestone is also exposed in four large isolated hills, composed in their upper part of Kinkaid limestone with a capping of Pottsville sandstone. These hills are outliers of the main Pottsville-Kinkaid scarp. KINKAID LIMESTONE 75 LITHOLOGIC CHARACTER The Kinkaid limestone of the Carbondale quadrangle resembles the same formation as originally described from exposures along Kinkaid Creek in Jackson County. The greater portion of the formation consists of fine- or medium-grained, gray, blue-gray, or dark gray limestone. Locally, how- ever, the fine-grained beds are very highly siliceous, and resemble chert in fracture and appearance, some even showing the banding common in cherts. They commonly weather to a porous spongy mass, and are generally in thin beds, seldom more than two inches thick. Fossils are rare. The color of these beds when fresh is most commonly a gray, dark gray, or black, but relatively slight weathering changes them so that they closely resemble wet yeast in color and texture. These highly siliceous beds ap- parently do not hold any consistent horizon, but occur at various places in any of the fine-grained limestone beds of the Kinkaid. Their presence seems to be one of the few characteristics distinguishing the Kinkaid from the Menard limestone below, which, as a general rule, has but few gray- black, or black, highly siliceous limestones. The Kinkaid otherwise close- ly resembles the Menard, especially in the medium-grained, blue-gray por- tions. The siliceous Kinkaid is well exhibited at various places in the gully to the east of the road and roughly parallel to it in SE. y 4 NW. y 4 sec. 31, T. 11 S., R. 2 E. ; and in the gullies in SE. y 4 SE. y 4 NW. % sec. 33, the S. y 2 SE. y 4 SW. y 4 sec. 22, the SE. y 4 NW. y 4 sec. 20, and the SW. cor. SW. y 4 NE. y 4 sec. 36, all in T. 11 S., R. 1 E. Shale beds occur locally in the Kinkaid, but the extent of any one given bed is usually limited. Fifteen feet of shale are exposed at the lower end of the gully in the SE. % NW. y 4 sec. 20, T. 11 S., R. 1 E., and about 9 feet in the lower end of the gully in the SE. y 4 NW. J 4 sec. 31, T. 11 S., R. 2 E. This last shale is a gray, locally fossiliferous, and thin-bedded silt shale. An- other shale bed worthy of note outcrops as a hematite-red clay. In the upper portion of the valley, forming the northeast side of the saddle in the hill in the cen. NE. y 4 NW. % NE. y 4 sec. 28, T. 11 S., R. 1 E., this shale has given the hillside a dull red color ; it also appears as red clay in the sides of the gully in the S. y 2 SE. y 4 SW. y 4 sec. 22, T. 11 S., R. 1 E. Its position in the section is probably about 90 feet above the base of the Kinkaid. Still another shale bed is exposed at various places in sec. 5, T. 12 S., R. 2 E. The best outcrop occurs in the side of the hill in the cen. SE. y 4 NE. y 4 of that section where 11 feet of dark gray shale is exposed in beds about one- quarter of an inch thick, and contains locally, brown concretions. Some of the shale has greenish and chocolate brown streaks in the upper 5^4 feet. The other thinner shale beds in the Kinkaid are commonly gray or dark gray silt shales, in a few instances showing reddish or brown bands. 76 CARBONDALE QUADRANGLE No such marked chert beds as observed in Hardin County 1 were noted in the Kinkaid limestone in the Carbondale quadrangle. The chert occurs rather as nodules or as small, thin, irregular sheets, and commonly in asso- ciation with the fine-grained dense limestones, especially the siliceous type, though small amounts of chert are not uncommon in the medium-grained blue-gray beds. The chert is mostly dark gray or black, and weathers gray or brown. COMPOSITE SECTION The composite section has been compiled from ten measured sections taken at various locations in the quadrangle. The sections chosen were those recording contacts with the overlying or underlying formations where possible, or containing some distinctive beds. It is not expected that this composite section will hold, except in a very general way, its principal func- tion being to present a view of the general constitution of the formation as a whole. In all probability there is considerably more shale present than is indicated. The shale horizons are, however, probably of local extent only, and are more likely to occur in the upper portion of the formation than in the lower. Composite section of the Kinkaid formation Thickness Pottsville — Feet Concealed 40 Kinkaid — Limestone, medium- to fine-grained, gray to light gray. Locally medium-granular, and fossiliferous 12 Limestone, medium- and coarsely granular, white and gray, with local fine-grained streaks 12 Limestone, dense, fine-grained, gray 5 Concealed 3 Limestone, very fine-grained, gray and light gray; varying to semi- lithographic, highly siliceous or argillaceous limestone; occa- sional thin shale bands. Salcatopinna common in upper portion 54 Limestone, medium-grained, granular; gray, blue-gray, or dark gray. Upper part locally cherty; shale up to 15 feet thick locally in basal portion 22 Limestone, gray, granular, and oolitic 1-11 Limestone, medium-grained, granular, gray, light gray, blue-gray, or dark gray 19 Limestone, fine-grained, gray, or blue-gray 10 Concealed 7 Degonia sandstone 1 Weller, Stuart, The geology of Hardin County: Illinois State Geol. Surv. Bull. 41, p. 219, 1920. KINKAID LIMESTONE THICKNESS The Kinkaid limestone is so markedly unconformable with the overly- ing Pottsville sandstone that its thickness is exceedingly variable. The greatest exposed thicknesses of the formation were observed in the eastern half of the quadrangle, and a section measured on the northeast side of Buck- Knob shows an interval of over 140 feet which is probably Kinkaid. This is the maximum thickness of the limestone noted. A more nearly complete, though somewhat thinner section, is exposed in the northeast-southwest gully in the SE. % NW. l / A sec. 20, T. 11 S., R. 1 E. One hundred and ten feet of the section are undoubtedly Kinkaid limestone and shale. The underlying Degonia is not reached. Still another long section, though less nearly complete than the pre- ceding, is to be found in a small gully heading northeastward in the SW. cor. SW. y A NE. y A sec. 36, T. 11 S., R. 1 E., where 113 feet of Kinkaid limestone underlies the Pottsville. Between the highest and lowest limestone beds of this 113 feet, the concealed intervals comprise 87 feet 4 inches. In the western third of the quadrangle the Kinkaid is generally thinner than elsewhere. In the SE. *4 sec - 21, T. 11 S., R. 1 W., the limestone is probably not much over 15 feet in thickness and is probably entirely absent- on the west end of Tip Top Knob near Cobden and on the ridge in the NW. y A sec. 20, T. 11 S., R. 1 W. STRATIGRAPHIC RELATIONS The Kinkaid probably is conformable with the Degonia below it in some places and disconformable in others. The Pottsville overlies the Kinkaid unconformably. Details concerning this unconformity and its character are given in the discussion of the Sub-Pennsylvanian unconformity under the Pottsville formation. PALEONTOLOGY The fauna of the Kinkaid, so far as is known, contains no forms which are distinctive of this limestone. The most common fossils are : Com- posita trinuclca, Cliothyridina sitblamellosa, Orthotetcs kaskaskicnsis, Pro- ductus ovatus and others, Bcllerophon sp. (very common), Sulcatopinna missouricnses, Allorisma clavata (?), and Archimedes sp. Less common are small Pentremites, trilobites (Phillipsia), and Myalina. CORRELATION The Kinkaid limestone of the Carbondale area is correlated with that in the type region, Jackson County, Illinois, by its similar lithologic char- acter, its position above the Degonia sandstone, and its almost continuous outcrop from the one region to the other. 7S CARBONDALE QUADRANGLE PENNSYLVANIAN SYSTEM Introduction The name Pennsylvanian has been given to the rocks succeeding the Mississippian in the State of Pennsylvania, where the former beds are particularly well developed. They are the coal-bearing rocks of the eastern part of the United States as well as of Illinois. Three major divisions of the Pennsylvanian system are recognized in Illinois : the Pottsville or basal member, composed of sandstone, shale, and shaly sandstone, with a few lenticular beds of coal and limestone; the Carbondale or middle member composed of shale, shaly sandstone, sandstone, limestone in minor amounts, and several workable coal beds ; and, the McLeansboro or upper member, Fig. 12. Contact of Pottsville and Kinkaid in W. % sec. 9, T. 11 S., R. 1 W. similar to the Carbondale. These three divisions of the Pennsylvanian system underlie about two-thirds of the State of Illinois. In the Carbondale quadrangle only the two lower members, the Potts- ville and the Carbondale, are present. The McLeansboro outcrops a few miles north of the quadrangle. The Sub-Pennsylvanian Unconformity The Pennsylvanian and Mississippian systems are unconformable in Illinois, a relation which is evinced in the Carbondale quadrangle by a conglomerate at the base of the Pennsylvanian and a variation of about 120 feet in the thickness of the Kinkaid limestone. In order to make available SUB-PENNSYLVANIAN UNCONFORMITY 79 detailed information concerning the unconformity as found in this area, the descriptions of all the best exposures are included. In the western part of the quadrangle the best exposure of the Potts- ville-Kinkaid contact is found in a cut along the Illinois Central Railroad about five miles north of Cobden (fig. 12). The section is as follows: Section including the Pottsville-Kinkaid contact, exposed in the railroad cut in the center of the W. % sec. 9, T. 11 S., R. 1 W. Thickness Pottsville — Feet 4. Sandstone, fine-grained, irregularly bedded, brown 9 3. Shale, gray shale matrix containing angular white chert frag- ments, rounded black grains, and transparent green, pink and brown rounded grains. Plant fossils abundant, es- pecially Sigillaria and Calamites 4 2. Conglomerate, composed of rounded pebbles of sandstone, brown and gray limestone, and dark and light colored chert 3^4 Kinkaid — 1. Limestone, fine,- medium,- and coarse-grained, locally fossilifer- ous and oolitic. Beds medium, locally thick 25% Covered No good exposures of the Pottsville-Kinkaid contact were noted in the central part of the quadrangle. In the eastern part, however, the three good exposures were seen from which the following sections have been described : Section of the oasal part of the Pottsville formation as exposed in the SW. cor. NE. y± sec. 25, T. 11 S., R. 1 E. Thickness Feet Pottsville — Covered, conglomeratic quartz sandstone talus Shale and sand; upper and lower portions calcareous, blue-gray, gray and buff shale with lenses and thin beds of calcareous sand- stone which weathers buff. The middle 4 feet is loosely cemented sand 13% Covered 3 Conglomerate, pebbles of shale embedded in a matrix of calcareous sandstone and sandy shale 2 Conglomerate; rounded and subangular fragments of limestone from % to 4 inches in diameter, in a granular matrix of sand grains, fragments of crinoid stems and other calcareous material. The limestone pebbles are largely dense, and fine-grained; when fresh they are gray, dark gray, blue-gray, and pink, and when weathered, gray, pink, and white 5 Covered (Kinkaid float lower in valley) An almost complete lithologic record of the change from conglomerate to sandstone is shown by the above section. 80 CARBONDALE QUADRANGLE Section including the Pottsville-Kinkaid contact, as exposed in the valley west of the road up the Muff from Cedar Grove Church in the NE. Vi NW. 14 sec. SI, T. 11 8., R. 1 E. Thickness Ft. In. Pottsville (Wayside member) — 19. Sandstone, fine- to medium-grained, irregularly bedded. Rip- ple marks common. Local iron concretions and staining.... 5 2 18. Shale, black, locally brown, siliceous, laminated and locally nodular. Weathers to small thin flakes 19 2 17. Sandstone, very fine grained, thin-bedded, weathers to sheets ^4 to y 2 inch thick 4 8 Kinkaid — 16. Shale, gray and dark gray, calcareous, plastic, fossiliferous 2 9 15. Shale, gray and dark gray, sandy, calcareous and fossiliferous 2 8 14. Shale, gray and dark gray, plastic 1 4 13. Limestone and shale. Argillaceous, fossiliferous limestone which weathers brown, interbedded with gray and buff shale 3 6 12. Shale, dark gray and blue-gray clay shale, probably with some thin limestone lenses. Partly covered 5 10 11. Limestone, gray, locally granular or nodular, in 9- to 18-inch beds. Highly fossiliferous; crinoid stems, large Archimedes, and horned and colonial corals especially common. No brachiopods observed 16 10. Shale, dark gray and blue-gray, plastic, with dark gray, gran- ular limestone nodules 2 7 9. Limestone, gray, locally granular, fossiliferous 18 4 8. Shale, dark gray, partly concealed 1 10 7. Limestone, thin-bedded, slabby, gray. Profusion of Myalina sp. Also numerous brachiopods 1 7 6. Shale, greenish gray, soft. Partly concealed 4 1 5. Shale, nodular, hematite-red color 4 3 4. Shale, green-gray clay shale, the lower part of which contains angular nodules of dense, gray semi-lithographic limestone, and grades downward into the bed below 4 3. Limestone, nodular, dense, gray. Lower portion contains lay- ers of shale and dark gray siliceous limestone 10 2. Shale, with nodules of dense gray limestone. Partly concealed 10 6 1. Limestone, siliceous, dark gray, with irregular cherty band- ing 2 120 A somewhat different relation between the Kinkaid and the overlying beds is illustrated by the following - section which appears in the same bluff east of the road and about 600 feet east of the section previously described. SUB-PENNSYLVANIAN UNCONFORMITY 81 Section including the Pottsville-Kinkaid contact, measured at the cen. E. y 2 E. y% NW. V± sec. 31, T. 11 8., R. 2 E. Thickness Pottsville-- Ft. In. Covered; sandstone talus 13. Conglomerate, rounded and sub-angular limestone pebbles in a calcareous matrix. Pebbles range from % to 2 inches in size. A great many are very oolitic and granular; some medium crystalline, dark gray; and others dense, light gray, gray and dark gray. Also some pinkish sandy limestone. Matrix weathers buff 2 9 12. Conglomerate, like above, but with fewer and generally larger limestone pebbles. Matrix is dense, gray limestone and pebbles are largely dense, fine- or medium-grained, gray and a few oolitic 1 11. Covered 11 3 Kinkaid — 10. Limestone, dense, semi-lithographic, with small masses of crystalline calcite. Color buff and bluish gray. Structure brecciated. Weathers gray and gray-white, to beds 4 inches thick 10 4 9. Covered 17 8. Limestone, dense, fine-grained, with masses of crystalline cal- cite. Color gray-black; weathers gray 2 6 7. Covered 2 6 6. Limestone, very siliceous, gray; weathers to a porous buff mass 7 5. Limestone, highly siliceous, thin-bedded, slabby. Color gray- black, weathers light gray. Beds and nodules of black chert 1 2 4. Limestone, very dense, fine-grained, almost lithographic. Color dark gray. Beds 6 to 12 inches thick 7 6 3. Limestone, dull earthy, dark gray, weathers light gray, and to thin slabs 14 2. Limestone, granular, gray 1 2 1. Shale, gray and dark gray, regularly bedded, siliceous 9 80 9 The base of the above section and that of the preceding section are at about the same elevation and the individual beds having the same vertical position in the section are therefore roughly comparable. The Pottsville sea is thought to have encroached upon a land surface into which well-developed valleys had been cut, as suggested by a variation of 120 feet in the thickness of the Kinkaid. The surface of the Kinkaid was probably generally irregular, and locally small valleys are suggested by field observations such as the difference between the thickness of the Kin- kaid in the exposures in the two valleys in sec. 31, T. 11 S., R. 2 E. The valley on the west side of the road is thought to have cut into the upper 82 CARBONDALE QUADRANGLE surface of the Kinkaid higher on the slope of that surface than the valley east of the road. The deposits exposed in the cut along the Illinois Central Railroad also probably represent sediments deposited in a valley of con- siderable width and smooth slopes. Within the valleys of the dissected Kinkaid land, locally at least, gravels derived from older sediments probably accumulated. The lithologic char- acter of the limestone pebbles forming the bulk of these gravels suggests that they were probably derived from the Chester formations and some also possibly from the Ste. Genevieve oolite. Field evidence suggests that on the steeper walls of the Pre-Pennsylvanian valleys and on the divides there was either little or no residual or transported gravel present to later form conglomerate, or that, as these areas were submerged, the encroaching sea scoured off these places and concentrated the loose material in the valleys, then part of the sea bottom. As a result the conglomerate is not found universally and its occurrence is probably rare rather than common. The difference between the basal Pottsville sediments in the previously mentioned valleys in sec. 31, T. 11 S., R. 2 E., — sandstone in the one and conglomerate in the other, — is doubtless an example of the effect differences in topographic position had on the type and character of the basal Pottsville sediments. Pottsville Formation name The Pottsville sandstone is named from the town of Pottsville in Penn- sylvania where the formation is well developed. In the Carbondale quad- rangle it consists primarily of alternating sandstone and shales, with very minor amounts of coal and limestone. Question has been raised as to whether some of the beds composing the so-called Pottsville of Illinois do not more properly belong with the Carbondale formation. This is a matter which can be decided only from the results of studies of much wider scope than that of a single quadrangle. The Pottsville of the Carbondale quad- rangle will therefore be defined, as heretofore, as the formation between the top of the Mississippian and the base of the Murphysboro (No. 2) coal. TOPOGRAPHIC EXPRESSION Because it consists of alternating beds of comparatively thick sandstone and shale, the topographic expression of the Pottsville formation is very pronounced (see figures 2, 3, 4, 6, and 26). The sandstones, a hundred feet or more in thickness, form cuestas, bluffs, and sheer, bare cliffs, and the shales produce terraces and gentle slopes quite in contrast with the sandstone topography. In the eastern half of the quadrangle the rocks are POTTSVILLE SANDSTONE 83 but little disturbed by faulting or folding, and this, combined with the gen- eral dip of the formations to the northeast and with erosion, has produced the series of sandstone cliffs and bluffs, interrupted, but easily traceable. These have been called the Pottsville scarp. LITHOLOGIC CHARACTER The most striking thing about the Pottsville formation is its variety — variety in the kinds of clastic sediments, variety in the size of the particles of these clastic materials, and variety in their relative proportions in dif- ferent places. The Pottsville includes practically all types of clastic sedi- mentary rocks from coarse-grained sandstone to plastic clay. Limestone is essentially lacking except for a few impure thin beds which occur in the upper and lower parts of the formation. In describing the size of grain of the Pottsville sandstones, the size terms suggested by Wentworth 1 have been adhered to. With the possible exception of the fine-grained sandstones, the sandstones of the Pottsville commonly show such a wide range in the size and proportion of the grains of the different sizes in the same bed or even the same specimen, that in general it has been impracticable for the purposes of the present investiga- tion to attempt to describe the sandstones in more detail than to indicate the range in size of grain or perhaps to specify the dominant size. THICKNESS The Pottsville formation is thickest in the eastern part of the Carbon- dale quadrangle. The Allen well located just beyond the east edge of the area in sec. 4, T. 10 S., R. 2 E., encountered about 700 feet of sandstone and shale which is probably largely Pottsville. The log of the well of the Southern Illinois Normal University at Carbondale in the northwest corner of the area, shows 525 feet of Pottsville sediments without reaching recog- nizable Chester beds. From the stratigraphic sequence and thickness of its units, the thickness of the Pottsville formation as determined from its outcrops is about 500 feet in the western and 625 feet in the eastern portion of the quadrangle. SUBDIVISION OF THE POTTSVILLE FORMATION Reconnaissance work in the Carbondale quadrangle suggested that the Pottsville formation might be subdivided into lithologic units of sufficient size and constancy to be mappable with reasonable accuracy. The detailed field work bore out this idea and the Pottsville has been mapped as four members, in ascending order, the Wayside sandstone and shale, the Lick 1 Wentworth, C. K., A scale of grade and class terms for clastic sediments: Jour. Oeol. vol. XXX, No. 5, pp. 377-392, July-August, 1922. 84 CARBONDALE QUADRANGLE Creek sandstone, the Drury sandstone and shale, and the Makanda sand- stone and shale. Since as yet the data at hand are insufficient to permit the correlation of the above-mentioned members with other units of the Pottsville formation already named elsewhere, the preceding field names are here used for explicitness and convenience in describing the lithologic units. WAYSIDE SANDSTONE AND SHALE MEMBER NAME AND DISTRIBUTION The Wayside member of the Pottsville in the Carbondale quadrangle is defined as the strata lying above the limestone beds of the Kinkaid and below the massive conglomeratic sandstone beds of the Lick Creek member. Outcrops of the beds are confined to the southeast quarter of the quadrangle (see Plate I) and the name Wayside is given to these beds from the village of Wayside situated a few miles northwest of the best exposures. The shaly beds outcropping in the west part of the quadrangle in sees. 21 and 22, T. 11 S., R. 1 W., in the vicinity of the Sifford School, occupy about the same stratigraphic position as the Wayside. They are of such slight extent, however, that it was not feasible to map them separately and they were therefore included with the Lick Creek. Elsewhere there are prob- ably shales or thin-bedded sandstones between the limestones of the Kin- kaid and the massive Lick Creek, but they are either thin or else not ex- posed and are therefore not separately mapped. LITHOLOGIC CHARACTER Of the four members of the Pottsville formation in the quadrangle, the Wayside is the most variable. Most of the beds seem to be lenticular in character, some of them comparatively thick, but thickening and thinning with confusing abruptness. The sandstones of the Wayside vary from thin- bedded to massive, from fine- to locally coarse-grained, and from rel- atively pure to very argillaceous sandstone. In places thin bands of quartz- pebble conglomerate occur, but they are relatively rare. The shales also show wide textural and compositional range. There are a few small thin lenses of coal. Argillaceous, dark colored limestone, probably belonging to this formation, is also found in places. The Wayside contains a rather striking gray-black shale member which is best exposed in the valleys in the NE. Y\ sec. 30, T. 11 S., R. 1 E. In the valley in the NW. 54 NE. Y\ of the same section about 45 feet of this shale are exposed. It is gray-black, not plastic, and locally nodular. It weathers blue-gray and commonly breaks into blocks approximately one foot by one foot by six inches. The shale grades upward, into a much- fractured bed of sandstone, dominantly medium-grained but locally coarse- and very coarse-grained. LICK CREEK SANDSTONE 85 Another noteworthy feature of the Wayside is the occurrence of a massive sandstone bed with a maximum thickness of about 45 feet. This bed forms waterfalls and cliffs along the stream in the NE. cor. SE. ^4 SE. Yx sec. 19, T. 11 S., R. 2 E., and in other valleys in the vicinity. As commonly exposed, it is of medium, coarse, or very coarse grain, cross- bedded and ripple-marked, but not conglomeratic. This sandstone seems to be one of the most persistent of the Wayside beds and farther east may assume a prominent place in the section. A good example of intra formational adjustment was noted in the valley in the center of the S. Yi sec. 29, T. 11 S., R. 2 E., where there are exposed several thin lenses of coal, none over two inches thick, interbedded with soft shales. The coal lenses, instead of being approximately horizontal, vary a foot or two in vertical position in a dozen or more feet laterally. In one instance a coal lens is inclined at an angle of thirty-five degrees. The inter- bedded shales share, in a measure, this variability of position together with the coal. THICKNESS It is difficult to state with certainty an average thickness for the Way- side because of the irregularities in the surface of the Kinkaid limestone. However, where the Wayside is well developed its average thickness is probably about 70 feet. In some places it is thicker, and in others con- siderably thinner, especially in the western part of the quadrangle where the beds thin out to a relatively unimportant unit. STRATIGRAPHIC RELATIONS The Wayside lies unconformably on the Kinkaid beneath it. The con- tact of the Wayside and Lick Creek is seldom exposed. At the two places where the contact was observed, however, the relations were massive sand- stone resting on micaceous, thin-bedded, shaly sandstone without transition beds and of massive sandstone resting on about a foot of transition sedi- ments underlain by shale. PALEONTOLOGY No fossil plants were observed in the Wayside, though fragments of Lepidodcndron and Sigillaria trunks are comparatively common. A few imperfectly preserved brachipods and a worm, probably a myriopod, were found in thin-bedded sandstone in the NE. corner sec. 26, T. 11 S., R. 1 E LICK CREEK SANDSTONE MEMBER NAME AND DISTRIBUTION To the first persistent massive conglomeratic sandstone lying above the Wayside the name Lick Creek has been given from the village bearing that name in the eastern part of the quadrangle, where this sandstone is promi- 86 CAKBONDALE QUADRANGLE nent in that part of the Pottsville scarp known as Cedar Bluff (figures 4 and 6), and is well and extensively exposed. The area over which this member of the Pottsville outcrops is very irregular and most commonly is a narrow band (see Plate I) because of the cliff-forming habit (see fig- ure 3) of the sandstone. There are a number of outliers which cap hills composed of Chester formations. The sandstone is responsible for the abrupt upper slopes of these hills to which the term knobs is popularly applied. LITHOLOGIC CHARACTER In general it may be said that the Lick Creek is a massive, medium- to coarse-grained, brown or buff sandstone. Locally where it is conglom- Fig. 13. Pottsville conglomerate. Typical unsorted material. 4/5 natural size. eratic it contains pebbles of vein quartz (figs. 13, 14 and 15). In the ex- treme western part of the area, where the Pottsville section was first worked out, this sandstone is dominantly a medium- to coarse-grained rock, with the grains for the most part rounded to subangular. Small amounts of white mica are present in the sandstones but are generally relatively incon- spicuous. Locally the sand is very loosely cemented and the rock is saccha- roidal, but in general the cementation is moderately firm. The con- glomeratic pebbles are for the most part vein quartz, but several exposures, LICK CREEK SANDSTONE 87 particularly one in the SE. y^ sec. 33, T. 10 S., R. 1 W., show zones or beds containing quantities of silicified fossil debris and small cherts, along with quartz pebbles. For the most part the conglomeratic materials occur in zones or beds from y 2 to 10 feet in thickness, averaging about 3 feet. Some of these beds are continuous for short distances but most of them thin out very rapidly and are seldom traceable even from gully to gully. The exposures of the Lick Creek in the western portion of the quad- rangle give a better understanding of the lateral variation of the sandstone than those elsewhere in the area. Of particular note are the pronounced lenses of shale and shaly sandstone. Good examples of these may be seen in the SE. ]/ A sec. 4, and in sees. 21 and 22, T. 11 S., R. 1 W. At the first- mentioned locality 15 to 20 feet of gray and black fossiliferous shale, rest- ing on medium-bedded sandstone with intercalated sandy shale, and over- lain by sandstone, is exposed in a cut along the Illinois Central Railroad. The fossiliferous shale, particularly, seems to be a lens in the basal portion of the massive Lick Creek. In sees. 21 and 22, the Lick Creek loses its essentially massive character in places, and instead exhibits a section roughly as follows : Thickness Feet Sandstone, dominantly massive, with interspersed, thin shale beds 25-35 Shale and sandstone; thin-bedded slabby sandstone, shaly sandstone, gray and dark gray shale, and sandy shale 30-40 Sandstone, massive 23-35 There is probably considerable variation in the relative thicknesses of these various units from place to place. The middle shaly group of beds is thought to be a local lenticular phenomenon, since it is known to be con- spicuous only in sec. 22, and the W. y> sec. 21. This threefold division of the Lick Creek may be best seen in the valleys in the cen. W. y> W. J/£, and N. / 2 N. / 2 sec. 22, T. 11 S., R. 1 W. In the central and eastern part of the quadrangle the Lick Creek shows a general similarity of character. It is for the most part a medium- to coarse-grained brown sandstone, though in places where the unweather'ed rock may be seen it is gray or slightly buff. It generally occurs in massive beds, and is moderately-firmly cemented, though locally it is quite saccha- roidal. Weathered portions of the sandstone have a speckled appearance, which is possibly due to the presence of decayed mineral grains between iron-stained quartz grains. In the very coarse-grained sandstone and gran- ule conglomerates, interstitial material is also present, but it seems to be distinctly of secondary origin. Conglomerate Pebbles. — -The quartz pebbles (figs. 13 and 14) which lend the conglomeratic character to some of the Lick Creek beds occur both 88 CARBONDALE QUADRANGLE scattered throughout the formation generally, and also concentrated along certain cross-bedded zones and along cross-bedding planes in association Pig. 14. Pebbles from the Pottsville conglomerate. 4/5 natural size. Fig. 15. Pottsville conglomerate. Smaller material than in figure 13 and much better sorted. 4/5 natural size. with coarse sands and granule gravels (fig. 15). Locally where the sur- face of a foreset bed is exposed, it is seen to be literally studded with quartz LICK CREEK SANDSTONE 89 pebbles, and this phenomenon is commonly repeated by many of the foreset beds of the same cross-bedded layer. Quite in contrast to this is the ex- posure in cross section of a single attenuated line of pebbles occurring along a single foreset bed in a horizontal exposure of 50 feet of cross-bedded sandstone. The quartz pebbles (fig. 14) vary in size from that of a sand grain to 2^4 inches in maximum diameter, though a more nearly average size for the larger pebbles is about l J / 2 inches. The small pebbles are well rounded and not uncommonly discoidal in shape. The larger pebbles are generally ovoid and, although the corners are rounded, numerous reentrant angles are present, particularly in some specimens. Incipient fractures are also common. This difference in character between the large and small pebbles suggests the possibility that many of the smaller pebbles in the Lick Creek conglomerates may be due to the breaking up of larger pebbles or boulders of quartz, and subsequent rounding of the smaller fragments by the waves and shore currents of the Pottsville sea. The most common colors of the quartz pebbles are white, pink, and yellow. Dull red and gray pebbles are moderately abundant but transparent quartz pebbles are rare. As a rule the colors are somewhat mottled, but some specimens show a very even color. None of the conglomerate horizons observed was traceable over any considerable horizontal distance. In general, however, the lower 20 feet of the Lick Creek contains the majority of the pebbles, their number grad- ually diminishing upwards, though in places beds of conglomerate 6 inches to 2 feet thick occur well up in the sandstone. Other minor lithologic features. — As has been previously stated, the Lick Creek sandstone forms cliffs. They are very commonly overhanging, and in places so under-cut as to form caves of a sort. The faces of the cliffs are rough and in some instances weathering of the less firmly cemented sandstone has produced rounded depressions and left odd-shaped knobs and ridges. Many of these owe their resistance to weathering to a cement of iron hydroxide. This type of weathering is commonly known as "honey- comb" weathering (see fig. 16). Cross-bedding is pronounced throughout the Lick Creek. It is most commonly of the delta type. The thickness of the foreset beds varies from *4 inch to 5 feet. The vertical distance between the topset and bottomset beds varies from a few inches to 14 feet, which is the maximum noted. Bedding surfaces, when exposed, often show ripple marks, generally of the current type and of medium size. Locally, small oscillation ripples in lenses of finer-grained or somewhat shaly sandstone suggest that these sediments were accumulated in small shallow pools. 90 CARBONDALE QUADRANGLE Another phenomenon worthy of mention is the development of small basins in the creek beds. Some of these are true pot-holes and have been left after the recession of a falls or rapids. Others of the depressions, however, seem to have been due in the beginning to the erosion of small areas of less firmly cemented sandstone, resulting in the production of small, shallow, bowl-shaped depressions. In them pebbles collected and were rolled around by the currents of the stream until the depressions were en- larged and deepened so as to resemble the true pot-holes. Fig. 16. "Honeycomb" weathering of Lick Creek sandstone. THICKNESS The Lick Creek sandstone varies in thickness both locally and region- ally. In the western part of the quadrangle the thickness varies from 80 to 140 feet with the thinner sandstone on the southeast-facing slopes of the ridge in sees. 27, 22, and 14, T. 11 S., R. 1 W. In the central and eastern parts of the quadrangle the thickness ranges from 125 to 170 feet, and averages about 140 feet. The greatest thickness of sandstone was observed in the N. y 2 sec. 19, T. 11 S., R. 1 E. STRATIGRAPHIC RELATIONS The stratigraphic relations of the Lick Creek with the Wayside beneath it have been stated in the discussion of the latter member. The Lick Creek DRURY SHALE AND SAXDSTOXE 91 and the Drury members seem to be conformable. In places the contact is quite distinct but more commonly there is a gradual transition from dom- inantly arenaceous to dominantly argillaceous sediments. PALEONTOLOGY Shale and sandstone beds containing fossil plants were found at the following locations : Center W. y 2 E. y 2 sec. 4, T. 11 S., R. 1 W., along the Illinois Central Railroad, SE. y A sec. 21, T. 11 S., R. 1 W. CORRELATION The position of the Lick Creek sandstone in the Pottsville section sug- gests its equivalence with a portion of the Caseyville conglomerate of Hard- in County as described by Butts. 1 Insufficiency of data on intervening areas makes further detailed correlation questionable. However, the Lick Creek seems to occupy the same position in the sequence of lithologic units in the Carbondale quadrangle as does the second conglomeratic sandstone men- tioned by Butts. 2 DRURY SHALE AND SANDSTONE MEMBER NAME AND DISTRIBUTION The Drury shale and sandstone, quite unlike the Lick Creek which underlies it, is a variable unit. Its most distinguishing feature is the gen- eral thin-bedded character of the strata. It resembles the Wayside sand- stone and shale in general composition, though the beds are generally thinner and less persistent horizontally than those of the Wayside. The Drury is named from its excellent exposures along Drury Creek in the western part of the quadrangle, particularly in the bluffs south of Makanda. It is de- fined as the unit of interbedded shale and sandstone lying above the Lick Creek and below the next persistent thick massive sandstone above, the Makanda (see figure 2). The area over which the Drury outcrops is very irregular (see Plate I). In general it is found exposed within a roughly east-west band across the quadrangle about four miles wide ; this band also contains outcrops of other members of the Pottsville formation. On the north slopes of the water- shed in the central and eastern part of the quadrangle, the Drury forms prominent inliers within the Makanda due to the fact that the heads of the valleys have steeper gradients than the dip of the rock formations. LITHOLOGIC CHARACTER The Drury is composed of shale, sandy shale, shaly sandstone and sandstone, with the first three predominant. The most characteristic litho- 1 Butts, Charles, in the Geology of Hardin County: 111. State Geol. Survey Bull 41, pp. 223-229, 1920. 2 Op. cit., p. 226. 92 CARBONDALE QUADRANGLE logic features are the sandy shales and shaly sandstones which weather to a plastic buff, cream or gray, sandy clay. Another typical feature of the Drury is the fine- and very fine-grained, thin, irregularly bedded sand- stone (fig. 17) which weathers white, with pink blotches commonly mottling the white surface. This phenomenon is commonly well shown in creek bed exposures. The sandstone is commonly very firmly cemented and is locally somewhat quartzitic. Clay inclusions, irregular current ripple marks, and mica are common in the non-quartzitic variety. The quartzitic type may be ripple-marked or contain small disc-shaped clay inclusions, but as a rule is not micaceous. The shales of the Drury are distinctly varied but nowhere were any calcareous shales observed ; calcareous material seems to be entirely absent from the member. The sandy and siliceous shales are probably the most Fig. 17. Thin and irregularly bedded Drury sandstone. common but there are numerous beds of clay-shale and gritty clay-shale. These clay-shale beds are the horizons in which the best fossil plant re- mains are found. Bright colors are lacking in the Drury shales, which are most commonly gray, buff, dark gray, or black. Mica is very generally present, particularly in the siliceous and sandy shales. The thin-bedded sandstones of the Drury have been described above. There are, however, numerous other beds of sandstone ranging from 2 to 12 inches in thickness as well as some rather massive strata. The former are usually brown, fine-grained, and in comparatively regular beds with irregularly ripple-marked surfaces. Locally they contain thin discoidal clay masses. The massive beds are dominantly medium- to fine-grained and if they contain shale at all, it commonly occurs as thin beds or bands. DRURY SHALE AND SANDSTONE 93 Carbonaceous material is found throughout the Drury as thin partings or laminae or disseminated through the sediments. In the western part of the quadrangle there are small lenses of coal, most of them very local in extent. None over two feet in thickness was observed with the exception of the uncommonly extensive lens exposed along Clay Lick Creek in the S. Yi sec. 32, T. 10 S., R. 1 W. Several drift mines have apparently been operated on a small scale in this coal at various times. A section measured at the one drift now being worked is as follows: Section including a Drury coal bed, measured at a drift mine on the north valley- slope of Clay Lick Creek, in the S. V 2 sec. 32, T. 10 S., R. 1 W. Thickness Feet Sandstone, fine-grained, thin-bedded (1 to 3 inches), irregularly bedded 6 Coal, sharp shining fracture, in beds 1 to 3 inches thick; coal generally clean, with but little pyrite 2 Shale, gray, soft 1V 2 Coal, like above, but softer and less brittle \y 2 Shale, gray-black, thin-bedded, hard and brittle y 2 The above described general lithologic characteristics hold to a greater or less degree for the Drury generally. In the western part of the quadrangle the Drury is largely free from massive sandstone. Locally it contains a bed of clay-shale about 20 feet thick which is light buff in color and very plastic. This bed is best exposed in the bluff on the west side of the railroad in the S. ^4 sec. 33, T. 10 S., R. 1 W. Another interesting feature of the Drury is the occurrence in places of sandstone conglomerates. The best example of such a conglomerate may be seen at the crossing of the road and the main creek in the SW. 34 sec. 28, T. 10 S., R. 1 W. The following section described from the north- south valley in the NW. Y\ sec. 32, T. 10 S., R. 1 W., is given to illustrate a typical section of the Drury in that part of the quadrangle. Section including Drury st?~ata exposed in the NW. % sec. 32, T. 10 S., R. 1 W. Thickness Feet Makanda — 14. Sandstone, massive, coarse-grained, locally conglomeratic; heavy beds 13. Sandstone, 3- to 6-inch beds, fine-grained; bedding fairly regular 10± Drury — 12. Shale, gray and light gray 2 11. Shale; gray, dark gray, and gray-black, interbedded. Slightly gritty, not fat. Carbonaceous markings along bedding planes. Thin-bedded, but not distinctly laminated 3 Covered 15 94 CAKBONDALE QUADRANGLE Section including Drury strata exposed in the NW. y± sec. 32, T. 10 8., R. 1 W. — Concluded Thickness Feet 10. Sandstone, irregularly bedded, medium-grained 1 9. Shale, gray and gray-black, thinly laminated, sandy. Bedding much contorted. Grades into sandstone above 5 8. Shale, gray, and shaly sandstone 4 7. Sandstone, fine-grained, in regular beds 3 to 10 inches thick.. 4 6. Sandstone, shaly, white, with intercalated clay layers. Grades almost imperceptibly into sandstone below it 2 5. Sandstone, fine-grained, in irregular beds y 2 to 6 inches thick.. 25 4. Shale and shaly sandstone; dark gray shale and brown sand- stone 2 Covered 16 3. Shale, gray, and shaly sandstone 1 + Covered 5 2. Sandstone, shaly, thin-bedded, with carbonaceous partings and mica with them. Bedding irregular 10 1. Shale, gray and gray-black, with about 6 inches of coal exposed 5 Covered. 110 Particularly in the central and eastern parts of the quadrangle, the Drury contains local massive sandstone beds which become somewhat pro- gressively more prominent eastward from the western part of the quad- rangle, and reach their maximum development in the center of the eastern part. Thence eastward rather fragmentary evidence suggests that the sand- stones gradually disappear. A general idea of the Drury section may be obtained from the following description of an exposure of about 65 feet of typical Drury in the SW. ]/\. sec. 7, T. 11 S., R. 2 E. The upper part of the exposure consists of gray-white shale with an interbedded massive sandstone layer 8 to 10 feet thick. The middle portion is largely shale with about an equal amount of shaly sandstone. The lower 20 feet are dom- inantly shale and shaly sandstone with a basal layer of black shale locally containing coal. This bed is common at the base of the formation in this region. Locally it has been observed with about 2 feet of green shale be- low it resting on the Lick Creek. The shales and sandstones of the Drury furnish a wide variety of geo- logic curios. There are different sorts of concretions, some so shaped as to resemble petrified organic remains. The slabs of thin-bedded sandstone often have odd markings, some of which may be worm tracks and casts, and others rill marks or scratches left in the sand by vegetation moved back and forth by waves or currents, and still others the casts of mud cracks. MAKANDA SANDSTONE 95 Another phenomenon which is well illustrated by the shales of the Drury is intraformational adjustment. In places shale beds appear to have been squeezed up through cracks in younger shales. Small faults which are distinctly local and of slight vertical extent, commonly with a throw of a few inches or possibly a foot, and small folds, some of them overturned, were also noted in places. THICKNESS The thickness of the Drury varies from about 90 to 120 feet in the western part of the quadrangle to about 50 to 70 feet in the eastern part. In the central portion of the quadrangle it is about 80 to 100 feet thick. STEATIGRAPHIC RELATIONS As has been previously stated the Drury is conformable with the Lick Creek below. In general it also bears the same relation to the Makanda above. In some cases the contact with the Makanda is sharp, but more often there is a gradual change without any sharp break. PALEONTOLOGY Shale deposits containing fossil plant remains were observed at the fol- lowing locations : NW. % NW. 14 sec. 14, T. 11 S., R. 1 W., at an elevation of about 700 in the main gully extending almost due west from the road. NE. % NW. ^4 sec. 16, T. 11 S., R. 1 E., in the east fork of the creek and about 100 feet upstream from the crossing of the road and creek. NE. Vi sec. 17, T. 11 S., R. 2 E., at an elevation of about 615 along the main creek. CORRELATION The Drury should probably be considered the equivalent of a portion of the Caseyville conglomerate. Comparing it with the section for Hardin County 1 it seems to occupy about the same position as does the shaly inter- val containing the Battery Rock coal. MAKANDA SANDSTONE MEMBER NAME AND DISTRIBUTION The Makanda sandstone is named from the town of Makanda in the western part of the quadrangle, near which it forms prominent bluffs (fig. 26). The outcrops of this sandstone are the most extensive of any of the members of the Pottsville in the area. It underlies a belt about six miles wide across the width of the quadrangle (see Plate I) and is responsible for a great part of the rugged topography of the area (figs. 2 and 26). The lower part of the Makanda is massive sandstone and forms conspicuous bluffs. The upper portion, however, while dominantly sandstone, is of the 1 Butts, Charles, in the Geology of Hardin County: 111. State Geol. Survey Bull. 41, pp. 223-229, 1920. 96 CARBONDALE QUADRANGLE medium- and thin-bedded type. The topography produced by the erosion of these beds is very rough, but lacks the more imposing prominence of the massive sandstone. LITHOLOGIC CHARACTER In general the Makanda may be divided into a basal massive sandstone 80 to 120 feet thick and an upper portion of about the same thickness, com- posed of medium- and thin-bedded sandstones interbedded with shale. These two subdivisions of the Makanda were mapped as one unit because in the eastern part of the quadrangle the basal sandstone loses its massive char- acter and becomes inseparable from the overlying beds, and also because over a large part of the quadrangle the contact of the massive sandstone and the overlying beds is concealed by glacial drift. The lower sandstone maintains roughly the same characteristics across the quadrangle except in T. 11 S., R. 2 E., where it loses its massive char- acter and becomes medium-bedded, and locally thin-bedded. Elsewhere it is a dominantly medium-grained, massive sandstone. It is brown when weathered, but fresh exposures are white or gray. As is the case with the Lick Creek, the sandstone in places is speckled brown or dark red and white. Cross-bedding, ripple marks, and the other phenomena described as characteristic of the Lick Creek are very common. The lower part of the Makanda differs from this last-mentioned formation, however, in that it is but rarely conglomeratic with quartz pebbles, and that what conglomerate is present occurs largely in the western part of the quadrangle and in very minor amounts. The massive sandstone is generally free from shale but does contain local lenses and thin beds. Of note is the peculiar "honey- comb" weathering (see figure 16) occurring commonly on cliffs of this sandstone. It consists of intricately convoluted ridges of iron-cemented sandstone ^ to 3 inches high, with a resulting surface much like an en- larged "brain-coral." This phenomenon is particularly well developed in the upper part of the valley of Panther Den Creek in T. 11 S., R. 1 E., and seems to be quite characteristic of the Makanda. It was also observed in the Lick Creek sandstone but to a very minor degree. The thin- and medium-bedded sandstones and shales of the Makanda are for the most part essentially similar to those of the Drury except that in the upper portion of the formation they are more micaceous. There is possibly, however, a somewhat more marked segregation of the sand and shale into separate beds. The Makanda contains locally in its upper por- tion beds of massive sandstone and also two horizons of black shale, one in the eastern and the other in the western part of the quadrangle, which may or may not be at the same horizon. As far as was observed, the beds in the upper Makanda are distinctly local and are not persistent over wide areas. MAKANDA SANDSTONE 97 But one outcrop of limestone was noted. It was seen in the creek in the cen. S. ]/ 2 NE. *4 sec - 8 > T. 10 S., R. 1 W., and is an impure sandy limestone about 9 inches thick. The logs of wells Renfro No. 2 and No. 3 (see PL III) in sees. 17 and 21, T. 9 S., R. 1 E., record 23 feet of limestone, and 17 feet limestone and 7 feet calcareous shale, respectively. There is some question whether the rock called limestone really is such, but if so the thickness of the bed is uncommon and rather remarkable for the Ma- kanda as known in this area. Lenses of coal occur at many horizons in the Makanda. Most of them are from a few inches to a foot in thickness and of very slight horizontal extent. An attempt has been made to work some of the thicker lenses. The most important of such are as follows : In the valley in the W. y 2 SW. *4 sec. 33, T. 10 S., R. 1 W., at an elevation of about 630 feet, about three feet of coal are exposed in the creek bank and in an old mine drift at this place. The bed is overlain by heavy-bedded sandstone and underlain by plastic gray and dark gray clay, locally sandy. The coal does not appear highly metamorphosed and has a woody structure. It pinches out almost completely at one place along the creek in a horizontal distance of about 30 feet. In the SW. % SW. % sec. 28, T. 10 S., R. 1 W., a small lens of coal with a maximum thickness of .2 feet is exposed along the north side of the road at an elevation of about 585 feet. It is overlain by about 18 inches of shale which grades into massive sandstone above. The base of the coal is covered. The coal is bright, comparatively hard, and brittle. Very little iron sulphide is present. In Stonefort Hollow in the E. y 2 SE. 14 sec. 27, T. 10 S., R. 1 W., several abandoned drift mines may be seen on the west side of the valley. About three feet of coal was worked and was probably rather soft and contained considerable pyrite. The coal is underlain by interbedded shale and sandstone. The roof is probably shale. In the SE. 14 SW. y 4 sec. 3, T. 10 S., R. 1 W., a test drift shows about 2 feet 6 inches of slaty coal. It is overlain by gray siliceous shale containing plant fossils in a fair state of preservation. The base of the coal is concealed. This coal bed is probably a lens in the shale. At the center N. line SE. % SE. % sec. 8, T. 10 S., R. 1 W., there is an abandoned drift mine. Conditions are such that thickness of coal cannot be de- termined but its occurrence suggests conditions similar to those mentioned above in sec. 3, T. 10 S., R. 1 W. Coal is reported to have been mined in the SW. cor. sec. 11, T. 10 S., R. 1 E. A test pit was sunk near the center of the south line of the same section to a depth of 12 feet but encountered no coal. There is a bed of black shale about 20 or more feet thick in this region and though no coal was observed in it, it is quite possible that locally it may contain some coal. In the western half of the quadrangle the beds composing Makanda, while variable, show the following general relations. 98 CARBONDALE QUADRANGLE Generalized section of the Makanda member in the western half of the Garbondale quadrangle Thickness Feet 3. Sandstone and shale, interbedded. Locally persistent massive sand- stone beds. Sandstones commonly medium- or thin-bedded. Shales often sandy, locally containing lenses of coal 90 to 130 2. Shale, gray-black, gray, or brown. Commonly siliceous. In places contains lenses of coal. Commonly contains plant fossils 30 ± 1. Sandstone, massive. Thin shale bands and coal lenses 100 to 120 The basal massive member is well exposed in the bluffs along the rail- road north of Makanda. The gray-black shale may best be seen in the east-west valley in the center of the E. J / 2 sec. 8, T. 10 S., R. 1 W. In the lower part of the same valley the massive Makanda sandstone may be seen and in the upper part of the valley the shale and sandstone of the upper part. In the eastern half of the quadrangle it is difficult to draw up a gen- eralized section which will apply to that region as a whole. In T. 11 S., R. 2 E., the Makanda seems to have lost its more or less characteristic basal massive sandstone and is primarily a succession of medium- and thin- bedded sandstones and interbedded shales. However, in the vicinity of the southeast corner of T. 10 S., R. 1 E., the following general section is found and is probably representative of the formation as a whole in this part of the quadrangle. Generalized section of the Makanda member in the eastern half of the Garbondale quadrangle Thickness Feet 5. Sandstone and shale, interbedded, micaceous, locally coal-bearing. Sandstone commonly medium- to thin-bedded; shales sandy, siliceous, and clay-shales 80 to 100 ( ?) 4. Shale, gray-black, siliceous. No coal observed 30± 3. Sandstone, generally massive. Some medium-bedded sandstone and local thin coal and shale lenses 60 to 80 2. Shale and shaly sandstone. Local beds of massive sandstone to 50 Av. 40 1. Sandstone, massive, locally containing sparsely scattered quartz pebbles 70 to 90 Av. 80 Sandstone No. 5 may best be seen in the valleys in sec. 9 ; shale No. 4, in the valley in the NE. cor. sec. 22, just east of the church in the SW. cor. sec. 14, and also in the NE. Y\ sec. 26 ; sandstone No. 3, shale No. 2, and sandstone No. 1, in the valley cutting diagonally across the SE. ^ SE. 34 sec. 33 and in the east-west valley in the E. y 2 sec. 34 ; all in T. 10 S., R. 1 E. Sandstone No. 3 forms a cliff along Grassy Creek in sec. 26, T. MAKAiNDA SANDSTONE 99 10 S., R. 1 E., and sandstone No. 1 does likewise along Panther Den Creek in sec. 3, T. 11 S., R. 1 E., and in sec. 34, T. 10 S., R. 1 E. The Makanda exhibits more or less the same details of sedimentary structure as does the rest of the Pottsville formation. Ripple marks, cross- bedding, and differential weathering are all well developed. An additional phenomenon, which is not peculiar to the Makanda but which is very well shown in the upper thin-bedded portion, is the brown dull polish occurring on the surfaces of the fine-grained sandstones which have been in deposit- ional contact with shales. It probably has been produced by the addition of cements, largely iron hydroxide, to the sandstone. The phenomenon is so characteristic of the contacts of the Pottsville shales and sandstones that an outcrop of brown, smooth-surfaced sandstone may be considered very good evidence of shale in the vicinity. In places the sandstones and shales of the Makanda have an astringent taste. The phenomenon is particularly well developed in what is known as Alum Cave, a series of overhanging cliffs along Wolf Creek in the SE. J4 sec. 17, T. 10 S., R. 2 E., where the sandstone exposed has a partial coating or surface impregnation of one or more of the alums. The alums do not penetrate far into the sandstone, and are probably the result of dep- osition by the evaporation of water which has trickled down over the faces of the cliffs from overlying beds of shale containing pyrite or mar- casite. Oxidation of these last two minerals produces acid solutions which in turn react with the aluminous substances contained in shales to produce certain of the alums. Of much the same type as the intraformational readjustments men- tioned in the description of the Drury, is the sandstone dike observed in the lower portion of the valley due east of the 712-foot road corner, in the center of the E. / 2 E. ^ sec. 1, T. 11 S., R. 1 E. The dike is composed of very fine-grained micaceous sandstone and has penetrated a fine- and medium-grained sandstone. It is exposed in cross section and consists of a single vertical portion about 6 inches across deploying upwards into a series of sandstone sills which pinch out within 3 or 4 feet horizontally. THICKNESS The Makanda is thicker in the eastern part of the quadrangle than in the western. The maximum thickness for the eastern half is about 300 feet and for the western about 250 feet. STRATIGRAPHIC RELATIONS The Makanda is probably conformable with the Drury below and the Carbondale above it. The base of the Murphysboro (No. 2) coal is used as the top of the Makanda. 100 CARBONDALE QUADRANGLE PALEONTOLOGY Most of the fossil plant remains found in the Makanda occur in the shale above the basal massive sandstone. The fossils are not as a rule particularly well preserved. The best exposures of fossiliferous shales in the Makanda occur at the following locations : At the junction of the two creeks in the center of the E. y 2 sec. 8, T. 10 S , R. 1 W. On the shale dump of the coal test drift in the valley in the center SE. Vi SW. !/i sec. 3, T. 10 S., R. 1 W. CORRELATION In the western part of the quadrangle the lower massive sandstone of the Makanda occupies about the same position with reference to the rest of the Pottsville formation as the upper conglomeratic sandstone of the Caseyville in Hardin County. 1 The remainder of the Makanda is prob- ably stratigraphically the same as the Tradewater of Hardin County. In the eastern part of the quadrangle the possible line of separation between the Caseyville and Tradewater is not clear. It should probably be placed at the top of one of the massive sandstones, preferably the basal sandstone. Carbondale Formation name and distribution The Carbondale formation is named from the town of Carbondale in the northwest corner of the quadrangle, near which it is well exposed, par- ticularly a few miles southeast of the town. The first use of the term Car- bondale in the literature is by Shaw and Savage in the Murphysboro-Herrin folio 2 and by Lines in Portland Cement Resources of Illinois, 3 both published in 1912. The formation is defined as the strata between the base of the Murphysboro (No. 2) coal and the top of the Herrin (No. 6) coal. There has been some difference in opinion in the past as to what should be consid- ered the base of the Murphysboro (No. 2) coal. The present policy of the Survey, however, is to consider the base of the actual coal as the lower boun- dary of the Carbondale formation, rather than to include the underclay with the coal. Approximately the north quarter of the Carbondale quadrangle is under- lain by the Carbondale formation (see Plate I). The area of outcrop is 1 Weller, Stuart, Butts, Charles, Currier, L. W., and Salisbury, R. D., Geology of Hardin County: 111. State Geol. Survey Bull. 41, pp. 223-229, 1920. 2 Shaw, E. W., and Savage, T. E., U. S. Geol. Survey Atlas, Murphysboro-Herrin folio, (No. 185), 1912. 3 Lines, E. F., Portland cement resources of Illinois, 111. Geol. Survey, Bull. 17,, p. 59, 1912. CARBOXDALE FORMATION 101 roughly triangular, about 5 miles wide on the eastern margin of the quad- rangle and about l l /> miles on the western edge. Except for a few practically isolated hills in the vicinity of Carbondale resulting from the protective effect of a sandstone bed which caps them, the area underlain by the Carbondale has but slight relief and exposures are few and small, and commonly confined to the banks" of the larger creeks. LITHOLOGIC CHARACTER In general the strata of the Carbondale formation were formed from an assortment of sediments such as are deposited in shallow water. Prob- ably the most prominent quantitatively is shale, followed in order by sand- stone, coal, and limestone. Most of the beds are more or less lenticular in character and those which are most persistent show considerable variation in thickness from place to place. The shales of the Carbondale are usually observable in outcrop only at artificial exposures such as coal mines. In such places the shales are com- monly gray or dark gray and relatively free from sand, and when exposed to the weather for a time either soften into a clayey mass, or split into thin laminae, particularly if they are micaceous. Most of the natural exposures of shale are sandy and are commonly micaceous. The dominant sandstones in the Carbondale formation are of the medium- and thin-bedded types, generally micaceous and brown. One bed, however, the Yergennes sandstone, is locally heavy-bedded and deserves separate consideration because of its usability as a key stratum. VERGEXXES SAXDSTOXE MEMBER Name and distribution. — The name Vergennes has been suggested by Savage 1 for the sandstone member of the Carbondale formation which occurs 20 to 40 feet above the Murphysboro (Xo. 2) coal. The name is taken from outcrops of this sandstone near the town of Yergennes in the Murphysboro quadrangle. In the western half of the Carbondale quadrangle a sandstone occupying about the same stratigraphic position and tentatively correlated with the Yergennes of the type area is prominent and outcrops are relatively common. It caps the hills in sec. 27, sec. 35, and the NW. Y\ sec. 36, T. 9 S.. R. 1 W., and also is well exposed in sec. 30 and the W. y 2 sec. 29, T. 9 S., R. 1 E., particularly in the valley in the SW. Y\ sec. 29. Lithologic character. — In general the Yergennes is a medium-grained, friable sandstone, occurring when unweathered in heavy beds, but commonly weathering into beds averaging about 10 inches in thickness. It is gray- 1 Shaw, E. W., and Savage, T. E., U. S. Geol. Survey Atlas, Murphysboro-Herrin folio (Xo. 185), p. 7, 1912. 102 CARBONDALE QUADRANGLE brown or reddish brown with locally a purplish cast and exhibits in places the speckled effect similar to that common in the Pottsville sandstones. Another phase of the Vergennes which is not commonly exposed, and may, indeed, be of uncommon occurrence, is the thin-bedded sandstone and very sandy shale which in places lies above or below a diminished thickness of heavy-bedded sandstone. This phase is suggested in the wells in the northern part of the quadrangle. No good exposures of the beds above the Vergennes sandstone were observed. Well logs, however, suggest that it is generally overlain by gray shale. The following section describing an exposure at Rocky Point in the NE. y A SE. y A sec. 23, T. 9 S., R. 1 W., illustrates specifically the relation of the Vergennes to the underlying beds. Beds No. 6, No. 5, and No. 4 are Vergennes sandstone. The coal in the section is thought to be only local. Section of Carbonclale strata including the Vergennes sandstone, exposed at Rocky Point in the NE. *4 SE. 14 sec. 23, T. 9 S., R. 1 W. Thickness Ft. In. 7. Concealed 6. Sandstone, gray, micaceous, fine-grained; in regular beds, probably originally heavy, but weathered to 1- to 3-inch slabs which further split into V±- to ^-inch sheets 17+ 5. Sandstone, carbonaceous 6 4. Sandstone, gray, with irregular coaly streaks 1 6 3. Coal 1 3 2. Shale, gray, grading into darker shale below 1 2 1. Shale, gray-black, micaceous, and slaty, locally highly carbonaceous and black. Contains local beds of shaly sandstone about 1 inch thick 26 1 Concealed. Thickness. — The thickness of the Vergennes sandstone varies from about 15 to 35 feet. Despite this variation, the sandstone, where heavy bedded, makes a fairly satisfactory key bed because of its easily recognizable topographic expression and relatively common exposures. LIMESTONES' OF THE CARBONDALE FORMATION Well logs record a number of limestone beds in the Carbondale forma- tion, but they do not seem to be extensive and are rarely over four feet in thickness. But two outcrops of Carbondale limestone were observed, the first in the center of the NW. y A SE. y A sec. 27, T. 9 S., R. 1 E., where about 3 feet of dense, gray limestone containing small clay masses is ex- posed in the valley slope about eight feet above the creek flood plain. The other exposure is in the NE. y A sec. 36, T. 9 S., R. 1 W„ where about 3 feet of dense, gray, siliceous limestone outcrops. CARBONDALE FORMATION 103 THE COALS OF THE CARBONDALE FORMATION Most of the important coals mined in Illinois are members of the Car- bondale formation. Herrin (No. 6) coal at the top of the Carbondale for- mation is the most extensively worked coal in Illinois. It is mined over a large area in southern and western Illinois. It bears various names, such as the Herrin, Franklin or Williamson County, or Blue-band coal. The next important coal below the Herrin (No. 6) is the No. 5 coal, mined in the vicinity of Harrisburg, Springfield, and Peoria, and known by names corresponding to the regions in which it is worked. Below the No. 5 coal, two beds, in places called No. 4 and No. 3, are known in parts of the State. The lowest coal of the Carbondale formation is the No. 2, variously called the Murphysboro or LaSalle coal from the regions in which it is mined. This coal is also reported to be worked in Rock Is- land and Mercer counties. In the Carbondale quadrangle but one of the above-mentioned beds can be recognized with any degree of certainty, namely, the Murphysboro (No. 2) coal. In the Murphysboro-Herrin folio 1 which deals with the type areas for both the Murphysboro (No. 2) and the Herrin (No. 6) coals, a generalized section is given. Certain units of this section can be recognized in the Carbondale quadrangle, especially in the western part where the ex- posures of the Carbondale formation are good, but in general there is a lack of similiarity between the succession of strata in the two areas. In the region around Murphysboro the No. 2 coal is locally divided into two beds by a shale parting which in places reaches a thickness of 30 feet or more. The actual beginning of this parting within the coal may be seen in some of the mines, so that the upper coal can be definitely proven to be a portion of the No. 2 coal, even though its position be above the lower bed. The equivalent of the Murphysboro (No. 2) coal as it is exposed in the Carbondale quadrangle should probably be considered as a zone of coals rather than a single bed. The number of beds of coal occurring above the upper Makanda shale and the Vergennes sandstone varies from one to three. Since the No. 2 coal is considered the basal limit of the Carbondale formation, the lower bed of the two or three coals which occur in places might arbitrarily be considered the No. 2 coal and the other coals above merely "riders" or lenticular beds. Actually, however, as stated above, it is probably more nearly correct to consider the two or three beds as rep- resenting a Murphysboro (No. 2) coal zone, which may possibly be due to a division of the major bed into two or three parts due to partings of other sediments, similar to the phenomena at Murphysboro or may, as suggested above, be due to "riders" or lenses of coal occurring above or below the equivalent of the Murphysboro (No. 2) seam. 1 Op. cit. 104 CARBONDALE QUADRANGLE The exposures of the Murphysboro (No. 2) coal in the Carbondale quadrangle are largely confined to the hills in sees. 30 and 31, T. 9 S., R. 1 E., and in sees. 23, 27, 35, and in the NW. l / A sec. 36, T. 9 S., R. 1 W. Tracing the coal eastward from the west margin of the quadrangle, it is first noted in a well drilled at an elevation of about 110 feet above sea level, near the center of the east line of sec. 20, T. 9 S., R. 1 W. The coal is re- ported to be about 4 feet thick. In the well at the Southern Illinois Nor- mal University (see Plate III) at the center of the south line of sec. 21, T. 9 S., R. 1 W., about 3 feet of coal was encountered immediately below the surficial material at a depth of 32 feet. From this last well the coal becomes deeper to the north and in a well drilled in Carbondale by the Central Illinois Public Service Company, about %y 2 feet of coal was found at a depth of 97 feet (see Plate III). The elevation of the coal is about 330 feet. Farther north, at the tie plant in the NW. cor. sec. 15, T. 9 S., R. 1 W., no coal was encountered in a well sunk to a depth of 1-11 feet. The well is located in the valley of Craborchard Creek at an elevation of about 390 feet, and the 90 feet of clay in the upper part of the well is probably valley filling. If the dip of the coal suggested by the Southern Illinois Normal University and the Central Illinois Public Service Company wells is decreased a little, the absence of coal in the tie plant well is explainable by the supposition that all the Carbondale rocks have been eroded from this area and that the first bed rock met in the well is of Pottsville age. The same may be said for the well drilled on the farm of Geo. Serrell in the SE. y A NE. y 4 sec. 22, T. 9 S., R. 1 W., where no coal was en- countered. This well also is located on the fill of the valley of Craborchard Creek and it is very probable that all the Carbondale rocks have been eroded from this area likewise. The relations of the coals of the No. 2 zone in the hill in sec. 27, T. 9 S., R. 1 W., are shown in figure 18, Nos. 7 to 10. A generalized section of the strata composing the hill is as follows : Generalized section of strata including the MurDhysboro (No. 2) coal zone from exposures in sec. 27, T. 9 8., R. 1 W. Thickness Carbondale — Feet Sandstone, medium-grained, friable, brown; in 3- to 9-inch beds (Vergennes sandstone) 15 + Shale; upper portion gray and soft, lower part gray -black with local brown streaks 30± Coal, locally absent to 2y 3 Shale, gray-black, with local brownish streaks 14± Coal 3V 2 to 4 105 >al zone from Thickness Feet 4± 8± 6 + 22, T. 9 S., al struck in uggests that the Forsyth h is further idale record 13 and seem The inter- rig about 25 the north. sd from ex- follows : -«■■§ ' zone in sec. Thickness Feet ds. nd 17 + 35± 2V 2 ± 4± 25± 4 to 6 2 + . 30 and 31, ling in that ing the No. )f the coals tion is that v_iiniii^u me u-iuui coal is the lowest at the mine and if such is the case it should probably be correlated 104 The exp quadrangle a 1 E., and in Tracing the first noted in near the cent ported to be mal Universit S., R. 1 W., surficial mate From th drilled in Cai %y 2 feet of ( elevation of Farther W., no coal well is locatd 390 feet, and valley filling. Normal Uni\ decreased a 1 the suppositi' area and tha The sam in the SE. } countered. 1 Creek and it from this are The rela S., R. 1 W., of the strata Generalized st 00* »i«rta Carbondale — ■ Sandstone (Vergen Shale; uj local br Coal, loca Shale, gr£ Coal CARBONDALE FORMATION 105 Generalized section of strata including the Murphysooro (No. 2) coal zone from exposures in sec. 21, T. 9 8., R. 1 W. — Concluded Thickness Pottsville( Makanda member)— Feet Clay, locally replaced by shale or argillaceous sandstone 4± Shale, gray 8± Sandstone, fine- to medium-grained, buff, micaceous 6 + Concealed. At the Hall and Blake mine in the SE. y 4 SW. y 4 sec. 22, T. 9 S., R. 1 W., the air shaft is 30 feet deep. The only bed of coal struck in digging this shaft is the one which is being mined. This suggests that the bed which occurs about 15 feet above the lower bed at the Forsyth mine in the NW. }i sec. 27 has pinched out, a suggestion which is further borne out by the fact that the wells around the city of Carbondale record but one bed of coal. The two coal beds of sec. 27 continue northeast into sec. 23 and seem to be persistent in that direction (see figure 18, Nos. 11 to 13). The inter- val between the coals is somewhat greater in sec. 23, averaging about 25 feet. There is a suggestion that the lower bed thickens to the north. The upper bed retains about the same thickness. A generalized section for sec. 23, T. 9 S., R. 1 W., compiled from ex- posures at Rocky Point, and from mines and well records is as follows : Generalized section of strata including the Murphysooro (No. 2) coal zone in sec. 23, T. 9 8., R. 1 W. Thickness Concealed. Feet Sandstone, gray, micaceous, medium- to fine-grained; in regular beds. Locally carbonaceous. (Vergennes sandstone) 17 + Shale, gray-black, micaceous, slaty, locally highly carbonaceous and black, and also sandy. Thin coal lenses in places 35± Coal 2%± Fire clay 4± Shale, gray and gray-black, locally sandy 25± Coal 4 to 6 Shale 2 + Concealed. The hills in sees. 25, 35, and 36, T. 9 S., R. 1 W., and sees. 30 and 31, T. 9 S., R. 1 E., present a different section from the preceding in that there are three distinct and well developed coal beds representing the No. 2 zone. Figure 18, Nos. 1 to 6 shows the relative positions of the coals and their probable correlation. The most problematical correlation is that of the Wilson mine. As far as could be determined the 6-foot coal is the lowest at the mine and if such is the case it should probably be correlated 106 CARBONDALE QUADRANGLE with the lower coals at the other mines. In view of the presence of a coal at an elevation of 445 feet about one-quarter of a mile east in the same B " S o t ^ o <3 - s O n y TO tu o § 6M s ii a l >-H