,-r..;f'. ,•'... 1/ pi .V'r,^.-., m URBANA Digitized by tine Internet Archive in 2012 witin funding from University of Illinois Urbana-Champaign http://archive.org/details/physiographicdiv55719macc STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE STATE GEOLOGICAL SURVEY M. M. LEIGHTON, Chief REPORT OF INVESTIGATIONS— NO. 19 I— PHYSIOGRAPHIC DIVISIONS OF THE AREA COVERED BY THE ILLINOIAN DRIFT- SHEET IN SOUTHERN ILLINOIS II— RECENT DISCOVERIES OF PRE-ILLINOIAN DRIFT IN SOUTHERN ILLINOIS By PAUL MacCLINTOCK i?i«S«SSS^ PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA. ILLINOIS 1929 state of illinois departmp:nt of registration and education M. F. Wm,sh, Director BOARD OF NATURAL RESOURCES AND CONSERVATION M. F. Walsh, Chainnan Edson S. Bastin, Geology William A. Noyes, Chemistry John W. Alvord, Engineeriiuj William Trelease, Biology Henry C. Cowles, Botany Charles M. Thompson, Representing the President of the University of Illinois STATE GEOLOGICAL SURVEY DIVISION M. M. Leighton, Chief jErFERSONS Printing & Stationery Co. Springfield. Illinois 1929 Letter of Transmittal State Geological Survey Division, July 8, 1929. Hon. M. F. Walsh, Chairman, and Members of the Board of Natural Re- sources and Conservation, Gentlemen : I take pleasure in transmitting herewith for pulilication as Report of Investigations No. 19 the manuscripts for the papers entitled "Physiographic divisions of the area covered by the Illinoian drift-sheet in southern Illinois" and "Recent discoveries of pre-Illinoian drift in southern Illinois," both by Dr. Paul MacClintock, who is making a study of the Pleistocene and Recent history of the glaciated portion of southern Illinois. This study has progressed far enough that from the scientific and edu- cational standpoints it is believed that these papers will be of particular inter- est to teachers in our public schools, research workers in geology, and to water well engineers in their search for underground water supplies. Very res]3ectfully yours, j\I. M. Leighton, Chief. Contents Page I. PHYSIOGRAPHIC DIVISIONS OF THE AREA COVERED BY THE ILLINOIAN DRIFT-SHEET IN SOUTHERN ILLINOIS 7 II. RECENT DISCOVERIES OF PRE-ILLINOIAN DRIFT IN SOUTHERN ILLINOIS 27 I PHYSIOGRAPHIC DIVISIONS OF THE AREA COVERED BY THE ILLINOIAN DRIFT-SHEET IN SOUTHERN ILLINOIS OUTLINE Page 7 Introduction Physiographic subdivisions and the criteria for differentiatmg them lU Historical interpretation FIGURES „ Pagu Figure , • .• ■ • « 1 Index may showing distribution of the topographic divisions 2. Diagrammatic cross-sections showing relationships between bedrock and glacial ^ drift . , 3. Topography controlled by bedrock, Saline County 4. Topography controlled by bedrock, Hamilton County. 13 5. Topography controlled by bedrock and uneroded drift. Marion County 13 ranklin County . . Topography controlled by bedrock, modified by eroded drift, Jefferson County 1 6 Topography controlled by bedrock and drift, Jefferson County. 7. Topography controlled by bedrock, modified by eroded drift, Frankhn County. . 1^ 9. Lake basin in uneroded morainic topography, Fayette County ^ 10. Morainic topography in Fayette County ^^ n. Flat-divide topography in Cumberland County ^^ 12. Illinoian flat in Clark County ■ ^^ 13. Tabular-divide topography in Shelby County - ^ 14. Tabular-divide topography in Clark County -^ 15. Aggraded lowland topography in Gallatin County -__ 16. Diagrammatic cross-section showing two drift-sheets PHYSIOGRAPHIC DIVISIONS OF THE AREA COVERED BY THE ILLINOIAN DRIFT- SHEET IN SOUTHERN ILLINOIS By Paul MacClintock INTRODUCTION The topography of that part of southern IlHiiois^ covered l)y the IlHnoian till-sheet is of unsual interest to the student of land forms. Physiographic- ally, the area lies within the Till-plains section of the great Central Lowland Province.- The first impression is of monotonous flatness, holding no prob- lems for the physiographer, but closer study discloses subtle differences in the topography Avhose interpretation calls forth fundamental principles of geomorphology. The area consists partly of a plain and partly of gently rolling hills, 50 to 60 feet high, though a few are as much as 100 to 125 feet in height. As the whole area is mantled with drift, and much of it with loess as well, out- crops of bedrock are rare and, where found, are commonly so low in valley walls that they do not help much in deciphering the origin of the upland topog- raphy. Furthermore, where morainic topography formerly existed, Sanga- mon erosion so' far subdued it that its identification as such becomes very difficult. As a result of the present study, the Illinoian drift area south of Sanga- mon and Illinois rivers and the Shelbyville moraine has been found to embrace nine distinct ]5hysiographic subdivisions. Sand dune topography might be in- cluded as a tenth subdivision, but its extent in the area is too- limited to be important areally. Obviously there are all gradations between the subdivi- sions, rendering the boundaries indistinct ; but within the area or areas of each subdivision the topography has its characteristic features. The prin- ciple areas are shown in figure 1. The analysis is made on the basis of dcstnictioiial topograpJiy, that produced by running water erosion, and constructional lopographw that pro- duced by glacial deposition. The interpretation is made possible by the fact that post-Paleozoic pre-Pleistocene erosion of the nearly horizontally strati- fied Coal Measures progressed to the state of maturity, in parts late matur- ity, during the last Tertiary cycle. Deposition of the mantle of drift is con- 1 South of the Sangamon-Illinois Rivers and tho Shelbyville moraine. 2 Fenneman, N. M., Phy.«iographic divisions of the United States: Annals of the ■Association of American Geographers, vol. 6, pp. 19-98, 191G. Pi[vsio(,R.\i'iiic Divisions LEGEND Boundaries of Drift-sheels ^'~.._^ Wisconsin drift ■ — -~- Illinoian drift Types or Topography . I Primarily bedrock, I I eroded ^^^ Karst I ^ I Morainic, uneroded E^Soj Morainic, eroded V/A Flat drift-plain \:y-:A Aggraded lowland Fig. 1. Outline map showing distribution of the topographic subdivisions in the area covered by the Illinoian drift-sheet, in southern Illinois. INDKX TO COINTIES 1. 2. Cass Menard 3. Morgan 4. Sangamon n. Scott 6. Christian 7. Greene 8. Macoupin 9. Montgomery 10. Shelby 11 Cumberland 21. Clinton 31. Edwards ^^ Clark 22. Marion 32. Wabash IS Jersey 23. Clay 33. Perry 14 Madison 24. Richland 34. Franklin IS B Hamilton ifi Fayette 2fi. Monroe 3(!. White 17 Effingham 27. Randolph 37. Jackson is Jasper 2S. Washington 38. "\A^illiainson in Crawford "!<. Jefferson 39. Saline 20. St. Clair .■;n. Wayne 40. C.allatm Physiographic Divisions sidered the beginning of a new cycle in the topographic history of the region and post-Illinoian erosion has advanced only to youth in the present cycle. The contrast between the wide valleys with, gently sloping walls of the bed- 3ZE 3ZIK ^ JX 300 600 900 1200 Feet Vertical scale 2 MilRS Horizontal scale Fig. 2. Diagrammatic cross-sections showing the relationships between bedrock and glacial drift for the nine types of topography described. rock topography and the steep-sided post-Illinoian valleys is not hard to see, but the distinction between broad valleys controlled by bedrock and broad depressions in undulatory constructional topography may be easily overlooked. 10 Physiographic Division's PHYSIOGRAPHIC SUBDIVISIONS AND THE CRITERIA FOR DIFFERENTIATING THEM The following are the physiographic suljdivisions which are found and the criteria by which they are recognized. Diagrammatic cross-sections illus- trating the relationships between bedrock and glacial drift for each of the [)hysiographic types are shown in figure 2. I. Topography Coxtpolled Primarily by Bedrock; Drift TOO Thin to Affect It (Figures 3 and 4) Characteristic features : (a) Surface gently rolling (b) Surface all in slopes (c ) Dendritic type of valley development (d) Wide open valleys (e) Gently sloping valley-walls (f) Structural terraces (g) Rounded divides (h) Divides unequal in height Physiographic Divisions 11 Fig. 3. Topography controlled by bedrock, northwest part of Saline County. Type 1. Fig. 4. Topography controlled !)>■ bedrdck, two miles west of Macedonia, Hamilton County. Type I. 12 pHYsiO(;H.M'inc Divisions II. Topography Controlled by Bedrock Modified by SLiGiiXLV Eroded Drift (Figures 5 and 6) Characteristic features : (a) Surface gently rolling (b) Surface mostly in slope, but some flattish areas in lower parts (c) Dendritic type of valley development; here and there a rise or a depression does not fit into a perfect dendritic system (d) Wide open valleys predominate, but some are constricted (e) Gently sloping valley-walls (f) Rounded divides (g) Divides unequal in height • Physiographic Divisions 13 r"i'i!.Lii.iiiiiiiiw.iiiiij.iii.miiMM^i.i mmimi^tif.ii a. Fig. 5. Topography controlled by bedrock, considerably modified by slightly eroded drift, in eastern Marion County. The hiU in the background is of bedrock. Type II. * ' i* -^.•^'?* ^I»K^-.-ss;=».^ Fig. 6. Topography controlled by bedrock, slightly modified by drift, seven miles west of Mount Vernon, Jefferson County. Type II. 14 PiivsioGKAriiic Divisions III. Topography Controlled by Bedrock Modified by- Eroded Drift (Figures 7 and 8) Characteristic features: (a) Surface gently rolling (1)) Surface mostly in slopes (c) Type of valley development in general dendritic (d) Wide open valleys, with steeper valleys within them in middle or against one side (e) Upper part of valley-walls gently sloping, inner or lower part steeper (f) Divides unequal in height I\^. Karst Top(;raphv ^Modified by Drift and Loess (Special Phase of Bedrock Control) Characteristic features : (a) Lakes (b) Undrained depressions, relatively small and deep (c) Depressions haphazard in topographic position (d) Major drainage development of dendritic type Phvsiographic Divisions 15 fig. 7. Topograph}- controlled by bedrock, nioditied by eroded drift, one mile south of Akin, Franklin County. Type III. Fig. 8. Topography controlled by bedrock, modified by eroded drift, seven miles west of Mount Vernon, Jefferson County. Type III. 16 Physiographu: Divisions V. Topography Controlled by Moraixic Drift, Uxf.roded (Constructional Topography; Figure 9) Characteristic features : (a) Surface, rolling to hilly (b) Non-dendritic type of drainage (c) Undrained depressions (d) Bottoms of depressions unequal in altitude (e) Steepness of slope independent of drainage or of topographic position VI. Topography Controlled by ]\Iorainic Drift, Eroded (Figure 10) Characteristic features : (a) Surface, rolling to hilly (b) Major features, depressions and hills, haphazard in topo- graphic position (c) Minor drainage features, as gullies, dendritic (d) No undrained depressions (e) Bottoms of depressions unequal in altitude (f ) Depressions largely graded to external drainage (g) Steepness of slope somewhat independent of drainage and of topographic position PHYsiociRAiMiic I)i\isroxs 17 Fig 9. Lake basin (recently drained arliticiall\ ) in uncrodcd morainic topography, five and a half miles southwest of Vandalia, Fayette County. Type V. Fig. 10. Morainic topography, but little eroded, three miles west of Vandalia, Fayette County. Type VI. 18 Physiographic Divisions VII. Topography Controlled by Drift, Non-Morainic, Flat, Un eroded (Figures 11 and 12) Characteristic features : (a) Flat (b) Above grade of nearest stream Physiographic Divisions 19 Fig. 11. Flat-divide topography in western Cumberland County. Type VII. Fig. 12. Illinoian flat, south from the Shelbyville moraine, Clark County. T3'pe VII. 20 Physiographic Divistoxs \'III. Topography Controlled by Drift. Non-Morainic, Eroded (Tahular-divide Topography; Figures 13 and 14) Characteristic features : (a) Flat divides (h) Divides practically equal in altitude . (c) Dendritic drainage pattern (d) Steep-sided valleys IX. Aggraded-Lowlaxd TopofiRAPiiY ; Hills Either Bedrock or Drift (Figure 15) Characteristic features : (a) Isolated liills rising above lowlands (b) Very broad, flat lowlands (c) Lowlands all at grade (d) Sharp angle at base of hills Phvsio(;i-. 3j. It seems entirely possible that the position of this interglacial horizon is now the same as it was during the interval between the deposition of the first drift and that of the Illinoian till. This seems clear from the fact that even the turf of the old soil is preserved, doubtless due tO' the fact that it was on the lee side 10 20 30 4-0 50 Fee t Scale LEGEND P.'!L-".0: Iron Concentrate Till Gunnbotil Soil Fig. 3. Diagram of the Big Creek exposure showing calcareous, unoxidized. Xebraskan (?) till (1), overlain by interglacial deposits — iron concentrate, gumbotil, soils "B" and "A" — and by Illinoian till : calcareous, unoxidized (2) ; and calcareous, oxidized (3). of a pre-Illinoian hill \\here there was no scouring by the Illinoian ice-sheet. The presence of perfect though fragile gastropod .shells in the lower 6 or 8 feet of the Illinoian till suggests that the ground was frozen ahead of the oncoming ice and that the frozen fossil-bearing silt was moved and incor- porated into the base of the Illinoian till. A thick deposit of this character is described below. Prc-Illinoian drift in seventy-foot bluff along Big Creek. — A mile farther north along Big Creek ffig. 2, location 2) a 70-foot blufif under- cut by the stream, making a .steep, fresh exposure, reveals pre-lllinoian drift below Illinoian till in the following sequence : Exposures ok Pee-Illixoiax Drift 33 Pleistocene deposits along Big Creek Thickness (South Center \E. '4 see. 34. T. 12 X.. R. 12 IV.) Feet Post-Illiiioian ■ 7. Loess, weathered 4—6 Ilhnoian (). Sand and gravel, weathered l^A 5. Till, oxidized, leached 5^ 4. Till, oxidized, calcareous 3 3. Till, blue-gray, calcareous 12 Pre-Illinoian 2. Till, drab-buff to gray-green, oxidized, calcareous, very hard 12 1. Till, blue-gray, calcareous 30 The line of demarkatioii between the base of the l)lue-gray IlHnoian till and the underlying oxidized till is very sharp and conspicuous. Evidently the soil and the leached part of the older drift were stripped away by the over- riding' IlHnoian ice. '?}■■/ K'^ :^P' i^:- - -v#if'. -;-:->-^-'^ >*'j». .'■•-/■v-^, .J,2^.■»-V- Fig. 4. Illinoian till (2) overlying pre-Illinoian till (1), half a mile north of Dennison, Clark County. Prc-JUinoian drift along z^'csf branch of Big Crcclc. — Two miles still farther northwest, along the south side of the west branch of Big Creek (fig. 2, location 3) an exposure shows a great thickness of pre-Illinoian drift. The section measures : 34 Exposures oi' Pre-Ili.inoian Dkiit Pleistocene deposits along zvest branch of Dig Creek (South Center NE. K sec. 29, T. 12 N., R. 12 IV.) Thickness feef Illinoian 6. Till, oxidized and leached 8 5. Till, oxidized, calcareous 16 Pre-Illinoiaii 4. Till, oxidized, leached, gummy 2 3. Till, oxidized, calcareous, hard 15 2. Till, blue-gray, calcareous 33 1. Bedrock 10 In this place the Illinoian ice did not erode away the weathered part of the lower till. Prc-Illinoiaii drift near Pciinisoii. — In tlie northeast corner of the county, half a mile north of Dennison (fig. 2, location -J-) an exposure has been made by Clear Creek in undercuttinc; its west bank just south of the road bridge. The ])luft' was very steep and the cut so fresh that there was no doubt that the relations were seen undisturl)ed (fig. 4). The following section \vas meastired : Pleistocene deposits along Clear Creek north of Dennison (SW. % NE. li sec. 23, T. 12 N.. R. 11 W.) Thickness Feet Post-Illinoian 8. Loess 4 Illinoian 7. Till, oxidized and leached 4 6. Sand and grave! lenses 3 5. Till, oxidized, calcareous 4 4. Till, gravelly and sandy, calcareous, much indurated 3 3. Till, blue-gray, calcareous 8 Pre-Illinoian 2. Till, red-brown, oxidized, leached J'j-l/^ 1. Till, greenish-gray, drab, calcareous, very hard 11 The lower till is so compact that the sharp pick, when driven with full strength, penetrated it only about an inch. Among other features common to pre-Illinoian till of the region it contains many small purple quartzitc pebbles. Prc-Illiiioian drift iwrtlicast of Marsliail. — Another exposure is found five and a half miles east-northeast of Marshall, half a mile east of Weaver (fig. 2, location 5) on the west bluff of the valley just south of the high- way bridge. Here the section shows : ExposuKEs OF Pre-Illinoian Drift 35 Pleistocene deposits northeast of Marshall (SW. % SIV. J4 sec. 1, T. 11 N., R. 11 W.) Post-Illiiioian 5. Loess, weathered Illinoian 4. Till, leached and oxidized 3. Till, blue-gray, soft, calcareous. Thickness Feet 40 Pre-Illinoiaii 2. Sand and silt, oxidized, calcareous 1-3 1. Till, gray-green drab, darker along tlie joints, dense, hard, calcareous 15 The presence of the hard, oxidized till below soft and unoxidized drift shows that the lower one is pre-Illinoian in age and was oxidized before the Illinoian was deposited. The absence of the leached part of the lower till is accounted for by its having been stripped away by the Illinoian ice-sheet during its advance over this area. Exposures of prc-Ill'uialan drift along Mill Creek soutlnvest of Mar- shall. — The road-grade up the south valley-wall of Mill Creek, four and a half miles south-soutiivvest of Marshall (fig. 2, location 6) has made an exposure about 65 feet high : Pleistocene deposits along Mill Creek four and a half miles soutlnvest of Marshall (NW. Y^ NE. % sec 16, T. 10 N., R. 12 IV.) Thickness Feet Illinoian 4. Silt, weathered, loesslike 5-8 3. Till, silty, pebbly, blue-gray, fossiliferous ; leached 10 to 12 feet.... 40 Pre-Illinoian 2. Till, sand, and silt, leached, oxidized ; disturbed 10 1. Gravel, calcareous 3 The thick silt resembles loess in texture but contains many glacial stones scattered entirely through it. It is predominantly blue-gray in color but has Ijeen oxidized to brown along numerous intersecting joints, outward from which diffusion has banded the mass concentric with the joint-blocks. The material is highly fossiliferous. The following species were identified by Mr. F. C. Baker : Fossils fi om Illinoian deposit along Mill Creek 1. Polygyra sp. Crushed 2. Polygyra monodon (Rackett) 3. Polygyra hirsuta (Say) 4. Hendersonia occulta (Say) 36 Exposures of Prf.-Illixoiax Drift 5. Succinia ovalis (Say) 6. Ilelicodiscus paralellus (Sa_v) 7. Strobilops virgo (P.lsbry) 8. Galba parva (Lea) 9. Carychium exiguum (Say) 10. Pomatiopsis lapidaria (Say) 11. Pisidium sp. Mr. Baker makes the following comments: "Numl)ers 1 to 7 are land shells. Numbers 8 to 10 inhal)it fresh water but are mostly amphibious, spending much time on wet mud flats. Numljer 1 1 is a true fresh water shell, a small clam, requiring water for existence; possibly washed into the deposit from a near-by stream or pond" — or moved there by the Illinf>ian ice. The entire lack of stratification of the deposit and the presence of the glacial stones makes it evident that the fossils must have been picked up by the advancing Illinoian ice. Their age consequently must l^e either very early Illinoian or pre-Illinoian, probably the latter. Four miles southwest of [Marshall (fig. 2, kxration 7) the vallev bluff for 100 yards reveals pre-lllinoian drift below Illinoian till and loess in the following section : Pleistocene deposits along Mill Creek jonr miles southwest of Marshall (NE. 14 NIV. Vi sec. 9, T. 10 X., R. 12 \V.) Thickness Feet Post-Illinoian 8. Loess and silt 15-18 Illinoian 7. Weathered till 2-3 6. Till, with incorporated silt and sand layer 20 Pre-Illinoian 5. Gumbotil, brownish 3 4. Till, brown^ hard, leached 3 3. Till, brown-gray-drab, hard, dense, calcareous 10 2. Sand and gravel, stratified, calcareous 20 L Bedrock, Pennsylvanian 10 The sand and gravel appears to he outwash material deposited in front of the advancing edge of the pre-Illinoian glacier and then over-ridden and buried by the till of this same advance. A mile farther north along the same valley-wall ('fig. 2, location 8) the section also shows pre-Illinoian outwash and till, though here the soil laver of the lower till has been eroded awav. Exposures of Pre-Illixoian Drift ^1 Pleistocene deposits along Mill Creek three miles soutlnvest of Marshall (West Center NE. V* sec. 4, T. 10 N., R. 12 IV.) Thickness Feet Post-Illinoiaii 7. Loess^ weathered 6-8 lUinoian 6. Soil zone, highly weathered 2% 5. Till, oxidized 3/, 4. Till, bluish-gray 10 Pre-Illinoian 3. Till, brownish-buff, very dense 1 2. Sand, coarse 8 1. Gravel, fine 10 It is possible that here waters circulating through the underlying sand and gravel formation altered the lower part of the blue-gray Illinoian till to make it look like an older drift-sheet, althqugh no banding was seen in the altered till. However, the proximity and similarity of this exposure to the unmistakable pre-Illinoian drift described above gives confidence to its in- terpretation as pre-Illinoian drift. Prc-Illinoian drift along zvcst branch of Mill Creek- — On the west branch of JNIill Creek, live and a half miles west-southwest of Marshall (fig. 2, location 9) the stream has undercut a liank 250 feet long and 35 to 40 feet high. The exposure shows typical pre-Illinoian drift below Illinoian in the following order : Pleistocene deposits along zvest branch of Mill Creek (SE. % SE. J4 sec. 36, T. 11 .v., R. 13 W.) Thickness Feet Post-Illinoian 9. Silt, loessial, and soil 6-10 8. Loess, gray, mottled brown 3 Illinoian 7. Gumbotil 3 6. Till, weathered and leached 3 5. Till, brown, leached 1-1 % 4. Till, brown, calcareous 5-8 3. Till, blue-gray, calcareous 5-10 Pre-Illinoian 2. Till, brown, weathered, leached 1-2 1. Till, brown with greenish tinge: very dense and hard: calcareous.... 10 The line of contact betw^een the two tills, though undulatory, is sharp and easily seen (fig. 5). Pebble counts from the two tills show considerable differences : 38 Exposures of Prk-Ili.i.\oia.\ Diukt Pebble counts from lUinokin and prc-lUino'um tills Illixoiax Till Pre-Illixoiax Till Percent Percent Chert 33 20.8 Limestone 21 52.8 Sandstone 10 10.4 Shale 5 Granite S .8 Basalt 10 5.6 Felsite 1 8 Diorite 5 8 Greenstone .8 Quartzite (brownish) 9 Quartzite (purple) 14.8 Quartz 1 1.6 The greatest difference is in the larger number of Hmestone and quartz- ite pebbles in the lower till and of chert in the upper. This is the same dif- ference which was noted in the Big Creek exposure (p. 31) where the pre-Illinoian drift contained 54 per cent of limestone and only 7 per cent of chert pebbles. Another river-bluff section showing two tills is seen three and a half miles northwest of Marshall (fig. 2, location 10). The relationship of ma- terial shows below a slumped and wooded upper slope. Pleistocene deposits three and a half miles northwest of Marshall (SE. Vi NE. 14 sec. 17. T. 11 N., R. 12 W.) Thickness Feet Illinoian 4. Till, blue-gray, calcareous 15 3. Clay, fatty, leached; fragments have "slickensided" collodial surfaces J^ Pre-Illinoian 2. Sand, gravel and silt, oxidized, calcareous 10 1. Till, blue-gray, calcareous 3j/2 The presence of leached and weathered clay on the oxidized sands and gravels shows that the pre-Illinoian drift was weathered before the till was deposited. Edgar County Prc-IUUwian drift along Clear Creek. — In Edgar County two miles north of the eastern part of Clark County (fig. 2, location 11), on the west bluff of Clear Creek, pre-Illinoian drift and weathered zone is shown in the following section : Exposures of Prf.-Ii.lixoian Drift 39 1:M:^^S^^'^^-''' r. -■.:.^^-y:-.:y. ■'■r\ ■i: Fig. S. lUinoian till (2) overlying pre-Illinoiaii till (1) along west branch of Mill Creek, Clark County. 40 ExrosiRES ok Prk-Illixoian Drift Glacial and interglacial deposits along Clear Creek ( Jiast Center NE. 14 sec. 9, T. 12 X., R. 11 W.j Thickness Feet Pdst-Illinoian 7. Loess and silt 8-10 IHinoian 6. Old soil zone 3 5. Till 25 T'l-c'-Illinoian 4. Silt, gummy, pebljly in places, leached and weathered 3 3. Till, leached 3 2. Sand and gravel, calcareous 2 1. Till, calcareous 8 In this exposure the over-riding ice must have eroded very little. Coles County Prc-IUiuoiaii drift alo)ig Hurricane Creek. — In Coles County, three jiiiles west of the northwestern part of Clark Cotinty (fig. 2, location 12) the west blufif of Hurricane Creek drops almost vertically from the flat, tabu- lar upland. Along this fresh exposure, which is 45 feet high and 500 feet long, the following sections were measured : Pleistocene deposits along Hurricane Creek fXU'. J4 -^E. ^ sec. 22, T. n .v., A'. W E.) A — SECTION AT NORTH END OF EXPOSURE Thickness Feet Post-Illinoian 5. Loess-like silt 5-7 IHinoian 4. Till, leached 3-5 3. Till, calcareous 8-10 Pre-Illinoian 2. Till and silt, leached and weathered ; containing much preserved vege- tation 1-3 1. Till, calcareous 15 P> — SECTION IN SOUTH FART OF EXPOSURE 3. Loess-like silt, leached 9 2. Till, leached 8 1. Till, calcareous: wood incorporated in zone through the middle 30 In the south part of the cut the IHinoian ice evidently eroded away the interglacial material, but the abundance of woody matter above a certain Exposures of Pre-Illixoiax Drift 41 zone suggests that this zone and all till above is Illinoian and that the wood is from interglacial vegetation. Cumberland County Prc-IUinoian drift northeast of Toledo. — Cumberland County adjoins Clark County on the west (fig. 1). Its topography consists of tabular di- vides left by fhe erosion of a remarkably flat till-plain. An exposure along one of the valleys in the northeast part of the county six miles northeast of Toledo (fig. 1, location 13) reveals pre-Illinoian till below Illinoian in the following measured section : Pleistocene deposits northeast of Toledo (Center NE. % see. 10, T. 10 A"., R. 9 E.) Thickness Feet IIliiKiian 6. Top concealed 5. Till, blue-gra\' at base, calcareous 13-18 Pre-Illinoian 4. Clay, leached, oxidized, gummy, yellow % 3. Till, leached and oxidized Vz 2. Till, oxidized, calcareous 6 1. Till, unoxidized, calcareous 15 How much deeper the pre-Illinoian till extends is unknown for no well records were availaljle. Effingham County Prc-IUinoian drift near Effingliaiii. — Effingham County in turn bor- ders Cumberland on the west and lies just east of the center of the State. It likewise shows remarkably flat tabular-divide topography trenched by steep-sided valleys. A small valley three miles northeast of Effingham ('n.g. 1, location 14) shows pre-Illinoian till in a well exposed section: F'leistoccnc deposits northea.^t of Effiiu/ham (SE. ]4 sec. 11, T. S .v., R. 6 E.) Thickness Feet Illinoian 4. Till, calcareous, bhic-gray in lower 6 feet 18-20 Pre-Illinoian 3. Till, • oxidized, leached 1 2. Till, oxidized, calcareous 9 1. Till, unoxidized, calcareous 5-8 42 Exposures of Puk-Illixoiax Drift From the contact between the two tills and extending downward into the lower drift for a foot or more there are pockets of gray gunibotil-like material, leached and sticky. This strongly suggests that guml)Otil had formed on the pre-Illinoian drift with these stringers penetrating the underlying drift, and that the main body of gumbotil was removed by the lUinoian glacier. Prc-IlliiiGian drift near AUnnwnt. — A second exposure of pre-lllinoian drift in Effingham County is seen in the valley two miles south of Altamont (fig. 1, location 15). The south wall of the valley is here a perpendicular blufif of drift more than 250 feet in length. The section as measured shows: Pleistocene deposits south of /Utaiiiout (SW. H sec. 22 T. 7 N., R. 4 II.) Thickness Feet Illinoian 4. Till, calcareous : lower 20 feet iinoxidized 35 Pre-IIlinoian 3. Silt, leached, oxidized 0-1 2. Gumbo, leached, yellow 0-3 1. Till, calcareous, dense, hard 0-12 The contact between the two tills dips gently westward and below stream-level, which accounts for the variation in thickness of the lower drift. There are some masses of the weathered lower drift in the basal part of the overlying Illinoian till. A buried soil zone near Effiiigliaiii. — A third exposure of the older drift where the buried soil is well preserved is seen one mile northeast of Effingham (fig. 17, location 16) : Pleistocene deposits near Effinf/hani (NE. yi sec. 21, T. 8 N., R. 6 E.) Thickness Feet Illinoian 2. Till, calcareous ; lower 10 feet unoxidized ; conta;ning gravel lenses and much wood in the lower part 30 Pre-Illinoian 1. Soil, leached A. Light fluffy silt 1^^ B. Heavy, dense, gray -brown silt containing scattered erratic pebbles , '. . 3 Exposures of Pue-Illixoian Drift 43 Fayette County Fayette County lies west of Effingham County and in the mid-line of the State. It is traversed from northeast to southwest by Kaskaskia River, to the east of which tabular-divide topography predominates, rising here and there to a low hill of constructional topography, whereas to the west of the Kaskaskia subdued and eroded hills of morainic origin prevail. Within the county six exposures of pre-IUinoian till have been found ; two in the east- ern part, one in the center, and three in the northwestern part. Prc-Illinoiaii drift near Louden. — On Sugar Creek one mile southwest of Louden (fig. 1, location 17) the road-side bank exposes the material of the hill through a thickness of over 80 feet: Pleistocene deposits near Louden (South Center see. 1. T. 7 N ., R 2 E.) Thickness Feet Illinoian 2. Till, blue-gray ; slightl}' oxidized along cracks ; normal hardness ; calcareous 60 Pre-Illinoian 1. Till, buff-brown to gray, yellow-orange; hard, dense; calcareous.... 20 The line of contact between the two tills dips about 20° to the east so that at the west end of the cut the lower drift is much thicker than at the east end. The leached and weathered part of the lower till was eroded away by the Illinoian ice, leaving only the oxidized portion toi reveal the presence of the two drift-sheets. Pre-Illinoiaii drift along Hickory Creek. — Halfway between Browns- town and Confidence on the south side of Hickory Creek (fig. 1, location 18) ditches on both sides of the road show: Glacial and interglacial deposits near Hickory Creek (South Center sec. 24, T. 6 N., R. 2 E.) Thickness Feet Illinoian 3. Gumbotil 3 2. Till, calcareous, bufif 4 Pre-Illinoian 1. Silt, leached, hard, dense; scattered siliceous pebbles and wad pellets, black material 4-5 Base concealed The lower material is doubtless a pre-Illinoian soil. It may be either on bedrock or pre-Illinoian drift, but from its texture, appearance, and pebble content it is probably the latter. 44 Exposures ok Prf.-Ii.lixoiax Driit Prc-Hliiioiaii drift al J'aiidalia. — At the highway liridg-e-head on the eastern outskirts of Vandaha, Kaskaskia River has so undercut its west bank as to expose a bkiff of drift aljout 70 feet high and 300 feet long (fig. 1, location 19; fig. 6). The succession of materials is: Pleistocene deposits at briilt/e in Hast I'andalia Thickness Pect Post-Illinoian 6. Loess, weathered 10 Ilhnoian S. Sand and gravel, weathered to reddish-brown 10 4. Till, leached 3 3. Till, calcareous Zs Pre-Illinoian 2. Till, leached, oxidized 1 J/2 — 1. Till, calcareous, mostly oxidized 8 The leached upper part of the pre-Illinoian till is somewhat irregular along the cut due to the disturbing action of the over-riding Illinoian ice. Along the irregular joints of the lower till there has been some deoxidation, leaving them drab in color, although the remainder of the till is bufif to brownish. This lower till is visible only at time of low water in Kaskaskia River. Prc-lUinoian guiiibofil south of Ramsey. — Two miles south of Ramsey in a deep valley tributary to Boaz Creek (fig. 1, location 20; east center sec. 30, T. 8 N., R. 1 E.) the road-cut shows 60 feet of Illinoian till contain- ing several lenses and pockets of sand and gravel, resting on four feet of graj^-blue, plastic, sticky gumbotil of jire-Illinoian age. This gumbotil is com- pletely "gumboized," making it a homogeneous mass in color and texture. Exposures of buried soil-profile near Ramsey. — One and a half miles northeast of Ramsey (fig. 1, location 21) the highway -cut on the north side of a small valley trenching a wide flat, shows the following section : Glacial and intcrglacial deposits one and a half miles northeast of Ramsey (Center sec. 4, T. 8 N., R. 1 E.) Thickness Feet Illinoian 6. Soil zones 6% 5. Gumbotil and Ferretto zone 4 4. Till, leached, heavily stained with iron 1 3. Till, calcareous, oxidized 15 Pre-Illinoian 2. Silt, pebbly, dark (sumbotil A) 2-3 1. Gumbotil, dark bluish-gray, very sticky (gumbotil E) 4 From road-level to bottom of valley 18 Exposures of Pre-Illixoiax Drift 45 Fig. 6. The west bluff of Kaskaskia River valley at Vandalia, Fayette County, showing Illinoian till (2) overlying pre-Illinnian till (\). 46 Exposures of Pre-Illinoian Drii-t Half a mile cast down the small valley (lig. 1, location 22) the stream has nndcrcut its south valley-wall to make a bluff which shows: Glacial and interglacial deposits near Ramsey (SE. Yj, sec. 4, r. 8 N., R. 1 E.) Thickness Feet Illinoian 7. Soil and Ferretto zones 6-7 6. Till, oxidized, calcareous 10 5. Till, unoxidizcd, cnlcarcnus 15 Prc-IUinoian 4. Silt, blue-gray, leached (gumbotil A) 1-2V^ 3. Gumbotil, blue-gray, buff-brown at the bottom (gumbotil B) Z\'2 2. Till, leached, oxidized 3^ 1. Till, calcareous, oxidized, hard; some silt and sand pockets 6 Stream-level These two exposures are remarkable in that the Illinoian ice failed to erode away the upper, or A horizon, of the pre-Illinoian gumbotil soil-profile. And furthermore, it is interesting to find the humus still present in the upper part of this buried soil-profile. Shelby County Prc-Illinoiaii till and gumbotil along Opossum Creek. — A deep high- way-cut on the west side of Opossum Creek (fig. 1, location 23) where the river has cut a deep valley below the general upland till-plain, shows tlie following succession of pre-Illinoian and Illinoian drifts (fig. 7) : Plcisloccnc deposits alonf/ Gpossinn Creel; (Xorfli Center see. 21, T. 10 A'., R. 1 E.) Thickness Feet Illinoian 5. Soil zones and leached till 14 4. Till, calcareous, oxidized 12-14 Pre-Illinoian 3. Gumbotil, dark blue-gray, plastic and sticky, typical in every respect — top slightly undulatory due to over-riding by the Illinoian ice 3 2. Till, leached, oxidized 1 1. Till,, calcareous, oxidized (contains lensc-like mass of fossiliferous silt— 2 feet) 8 Road level — but tiU is seen to bottoiu of the valley 20 Exposures of Pre-Illixoian Drift 47 LEGEND 4. Silts, soil and loess 3. Illinoian till, leached, oxidized 2. Illinoian till, calcareous, oxidized 1. Pre-Illinoian guinbotil Fig. 7. Exposure of Pleistocene deposits two miles northeast of Oconee, Sliclb\- County, west bluff of Opossum Creek. 48 Exposures of Prk-Illi.voiax Drift Montgomery County Pre-IIlinoiaii drift near Hillsboro. — One of the most S])ectaciilar ex- posures of prc-Illinoian drift in the State is one and a half miles northwest of Hillsboro (fig". 1, location 24, south center sec. 34, T. 9 N., R. 4 \V.). Here the state highway rises about 100 feet from the broad flat to the west to the crest of a cons])icnous group of hills trending north and south. From the crest a fine view is obtained across the flat to Litchfield seven miles away. Through the crest of this hill a high\\a\-cut 30 feet deep exposes an interesting Pleistocene succession (fig. 8). Till, having a normal soil-profile down to calcareous drift, is .seen on either flank of the hill. At the crest of the n.il! and dipping 30° eastward across the face of the cut is a layer of pebbly sand. This layer is 6±: feet thick, made of coarse sand stained yellow to orange and to lirownish near its Ijasc. At the top the sand layer grades imperceptibly into a layer of ver\' dark gray, sticky, slick, heavy clay, 6 to 7 feet thick, containing a few sili- ceous pebbles. It is evidently a gumbosand pro