A./ 
 
 5 
 
 
Digitized by the Internet Archive 
 
 in 2012 with funding from 
 iyersity of Illinois Urbana-Champaign 
 
 http://archive.org/details/waterlooareamonr1 950<aas 
 
STATE OF ILLINOIS 
 DEPARTMENT OF REGISTRATION AND EDUCATION 
 STATE GEOLOGICAL SURVEY DIVISION 
 Morris M, Leighton, Chief 
 
 WATERLOO AREA 
 Monroe County- 
 Waterloo Quadrangle 
 
 GUIDE LEAFLET 5 OF 
 
 by 
 
 Gilbert 0. Raasch 
 
 Urbana, Illinois 
 November 4, 1950 
 
 
ITINERARY 
 
 0,0 
 
 0,0 
 0.1 
 2.0 
 
 (0.0) Caravan assembles, headed south, in parking area in front of Water- 
 loo High School, 
 
 (0.0) Turn right (W) . 
 
 (0.1) Stop sign. Turn right (N) on Route 3. 
 
 (2.0) STOP No. 1. Upland Topography. 
 
 Although this area was glaciated by the Illinoian Glacier, the 
 topography is controlled largely by the bedrock formations which under- 
 lie the glacial deposits. This topography has been somewhat subdued 
 and modified by a thin covering of glacial till and a thicker covering 
 of wind-deposited loess. 
 
 The Mississippi River trench which can be seen in the distance 
 to the west was widened and deepened during and after the time of 
 Illinoian glaciation. Accordingly its local tributaries were also 
 able to deepen and extend their valleys; as a result, these streams 
 have carved deep ravines, cutting well below the old upland surface* 
 
 5.3 
 0.5 
 
 (7,3 
 (7.8 
 
 1.5 (9.3 
 
 1.8 (11.1 
 
 1.7 (12.8 
 
 0.1 (12.9 
 
 0.3 (13.2 
 
 Caution. Intersection with Route 158 in ravine. Go left (NW) on 
 Route 3. Ledges of Mississippian bedrock on left along stream. 
 
 Tenter COLUMBIA. Continue through on Route 3, Columbia Quarry, a 
 very large operation tunneling massive beds of St. Louis limestone, 
 lies 1 mile east; 
 
 Leave Columbia, on Route 3. 
 
 Intersection with Jefferson Barracks Bridge highway. Continue 
 ahead (N) on Route 3, 
 
 Caution. Railroad crossing. 
 
 Turn right (E) on blacktop road up Cement Hollow. 
 
 STOP No. 2. DUP0',)ANTICLINE and OIL FIELD. 
 
 Walk east one-half mile on Cement Hollow road* 
 
 Ledges of Mississippian (Ste. Genevieve) limestone exposed along 
 creek show steep westerly dip. 
 
 0.3 miles farther east pumping wells of the Dupo oil field may 
 be seen. 
 
 A short distance beyond, the ledges of Mississippi (Salem) 
 limestone along the creek are horizontal and a few hundred yards 
 still further they are inclined gently to the east. 
 
•:-"* 
 
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 . ' ") 
 
 i .?:.-• i 
 
ROCK STRUCTURE AND OIL ACCUMULATION. 
 
 These changes in the attitude of the limestone layers are the 
 result of a sharp upfold (anticline) in the bedrock strata. This 
 fold averages about a mile wide and runs from St. Louis south beyond 
 Waterloo, Its date of formation is not definitely known but took 
 place at some time during the long interval between the Coal Period 
 (Pennsylvanian) and the Ice Age (Pleistocene). Later the creek cut 
 its valley down into the bedrock and revealed this cross-section of 
 the anticline. 
 
 Oil is lighter than salt water. In porous rock layers under- 
 ground, the oil slowly separates from the water and then migrates 
 to the highest places in the porous stratum, just as cream seeks the 
 highest place in a bottle of milk. For this reason, the oil in 
 time rises into the crests of folds or domes to form "oil pools," 
 Such pools are not cavernous openings but merely high places in a 
 porous rock stratum. 
 
 The oil in the Dupo Field comes from a porous zone in 
 Ordovician, Kimmswi ck (or "Trenton") limestone, which here lies 
 about 600 feet below the surface. The pool was discovered in 
 1928 by studying the inclination of the strata, such as you see 
 here. 
 
 Besides the wells here in Cement Hollow, others are located 
 on top of the bluff to the north, and others lie on the Mississippi 
 flats to north west. Thus, the present topography of hills, and 
 valleys has no relation to the location of oil pools, which depend 
 entirely on high and low places in the bed rock (bedrock, structure), 
 
 (See diagram in appendix.) 
 
 MISSISSIPPI^ BED ROCK. 
 
 The lowest (oldest) rock shown in Cement Hollow belongs to the 
 Keokuk Formation, It is granular limestone made up largely of 
 ground-up shells, crinoidal remains, and corals. Fossils are 
 abundant and include many types of brachiopods, bryozoa (moss 
 animals), cup corals, and trilobite heads and tails. Most abundant 
 is the brachiopod Spirif er washingtonensis Weller. These ledges 
 are present in the creek bed at the east end of the outcrop. 
 
 Just above them in the creek are some layers of dull gray 
 shaly limestone, fine grained and unf ossiliferous. These belong 
 to the Warsaw formation, here thin, which is elsewhere famous 
 for its crystal-lined geodes. 
 
- 3 
 
 The Warsaw Formation grades upward into a yellowish porous, 
 granular limestone, the Salem formation, here somewhat resembling 
 the famous building stone, the Indiana Limestone. It is this same 
 Salem formation which in Indiana supplies this valuable building 
 stone. 
 
 Farther up the hollow at a higher elevation, the road passes 
 outcrops of gray, massive, dense St. Louis Limestone, which lies 
 above the Warsaw. Highest Mississippian formation in the region 
 is the St. Genevieve Limestone which lies above the St. Louis. 
 It is present at the west end of the belt of outcrops as a result 
 of folding which has dropped it to a low elevation along the west 
 odge •of ■ tho' Dupo (or Waterloo) Anticline. 
 
 All of these formations were deposited on the floors of ancient 
 seas which invaded the interior of the continent in Mississippian 
 Timo. 
 
 0,0 (13.2) Continue ahead along main blacktop road which winds northeastward 
 out of Oement Hollow. 
 
 2,2 (15.4) STOP No, 3. Among sink holes at top of grade. 
 
 For the next mile & a half,- tho route lies between a network of 
 small sink holes. Wherever the St. Louis and Ste. Genevieve lime- 
 stones come close to the surface, this sink hold topography develops. 
 The pure limestones are readily dissolved by surface waters which 
 sink underground and flow along joints (fracture systems) in the 
 rock. The dissolving action of the water widens those joints so 
 that in time the overlying earth falls into the crevices, leaving 
 sink holes at the surface. Some sink holes also are caused by the 
 collapse of the roofs of caverns that have been dissolved out of 
 the limestone. 
 
 In time, the network of enlarged crevices and sink holes becomes 
 so extensive that streams sink below the surface and flow underground, 
 Note that few surface streams cross the sinkhole belts shown on tho 
 topographic map, 
 
 1,6 (17,0) Stop sign. Turn left (N), 
 
 1,0 (18,0) Standard School (check point). 
 
 1.4 (19,0 Y-intersection, go left, (N), 
 
 0,2 (19.2) Stop sign. Go left (W). Road has descended to flood plain of 
 Mississippi River, here five miles wide. This is an alluvial 
 plain built of Mississippi river., sands and gravels washed 
 down the great river in Pleistocene and recent times. Except for 
 the man-made levees, such as that on tho right, tho -flood plain has a 
 very flat topography. It is here five miles wide with the river 
 at present flowing along the Missouri side. 
 
 Quarries in river bluffs to left are largely in the St. Louis 
 
 Limestone. 
 
•*•:,' "*• . 
 
 " -i . V ' 
 
- 4 - 
 
 0*4 (19.6) Turn left (E) into road to East St. Louis Stone Company Quarry. 
 
 0.2 (19.8) STOP No, 4. At base of road ascending bluff. Walk up road to top 
 of qiiarry. 
 
 Above the bedrock forming the quarry rime, stripping operations 
 to remove the earthy overburden are in progress. 
 
 The vertical cliff of earth consists of loess, with patches of 
 glacial till present in the floor of the excavation. Beneath the 
 till, in crevices going into the bedrock are patches of fine, 
 crumbly rod clay. 
 
 Tho red clay dates from before the Ice Age and is the insoluble 
 residue left behind by the weathering of the limestone. This clay 
 once covered all of the bedrock surface, but was largely scraped 
 away by the Illinoian ice sheet* 
 
 When the ice sheet melted away, any earth or stones that had 
 become incorporated in the glacial ice during its long journey from 
 northeast Canada was left behind. This residue from the melted ice, 
 forming a thin blanket of earth over the surface of the region, is 
 called glacial till. It is an unsorted mass of clay, sand, and 
 pebbles. 
 
 During the long interval of time after the melting of the 
 Illinoian ice sheet, rain waters, scoping downward through the till 
 blanket, dissolved out the lime and oxidized the iron content to a 
 buff or a red color. Many types of pebbles such as granite, gneiss, 
 and gabbro were weathered away, and only very rcsistent rocks such 
 as quartz, chert, quartzite, basalt, and greenstone still remain. 
 Deeply wcathcre . facial till such as this is called gumbo-till. 
 
 Tho".7if«K3is4in Glaciorwhich followed the Illinoian after a period 
 of some 150,000 years die not roach this part of Illinois, But the 
 waters from its melting, choked with sediment, poured down the 
 Mississippi river, whore great sand and mud flats developed. The 
 westerly winds, blowing across the flats, picked up the clay and 
 silt and dropped most of it over the bluffs and upland to the 
 cast. Such upland deposits of dust arc called "locssj 1 which can 
 stand in massive, vertical banks because of the tight packing of the 
 very angular particles. 
 
 As in the till, the descending rain waters dissolved the lime 
 from the upper part of this thick loess deposit. The downward 
 movement of the waters was largely stopped when the impervious 
 gumbo till under the loess was reached. Hence, the lime dissolved 
 above was again deposited in the lower part of the loess, as 
 rounded aggregations of an ashy color. Some of these assume 
 fanciful shapes called "loess kindchen," i.e. "little children." 
 
 Descend bluff and go south past quarry. 
 
- 5 - 
 
 1.0 (20. 8) STOP No. 5. FALLING SPRINGS PARK. 
 
 Yfalk east to Falling Springs. Here, where a large stream of 
 water gushes from the mouth of a cavern, we see the opposite end 
 of the underground drainage system the beginnings of which we 
 saw in the sinkhole network at STOP No. 3. There a orvern and 
 crevice system oarry&ag waters from the upland region to the 
 east has been cut open by the development of the Mississippi River 
 trough. Thus the underground stream- is forced to cascade down 
 the bluff into the open. 
 
 Walk north, past numerous cavern openings to old quarry in 
 St. Louis and Ste. Genevieve limestones. 
 
 Approximately the lower 50 feet of limestone in this quarry 
 belongs to the St, Louis Formation. The layers are thicker and the 
 rock denser below, with one thick buff layer conspicuous among the 
 light gray strata. The higher St, Louis strata are thinner and 
 more distinct, and separated by shale laminae. The surfaces of 
 some of these upper layers are covered with fronds of bryozoa, others 
 have crinoid heads and the spines of sea urchins. 
 
 Some of the St. Louis limestone layers have been shattered 
 and recemented, probably while the layers still lay beneath the 
 waters of the Mississippian sea. Another conspicuous feature of 
 the rock is the occurrence of stylolites-vertical flutings in the 
 rock. These probably developed as a result of solution under pres- 
 sure, possibly at a time when the sediment was not yet completely 
 solidified. 
 
 The upper 30 feet of limestone belongs to the Ste. Genevieve 
 formation, characterized by coarser grain and oolitic texture. 
 (Oolites are tiny spherical aggregations of lime carbonate with 
 a concentric structure, like the layers of an onion). The Ste. 
 Genevieve beds are commonly cross-bedded and probably originated 
 as a lime sand. 
 
 Near the base of the St. Genevieve are shaly layers full of 
 pebble-like masses of fossil algae. Immediately below these is a 
 very coarsely granular limestone with cross-sections of gastropods 
 (snails) . 
 
 Above the Ste. Genevieve is a thick overburden of Pleistocene 
 loess. 
 
 0.0 (20.8) LUNCH STOP in FALLING SPRINGS PARK. 
 
 0,0 (20,8) Reverse route and go northwest on Mc Bride road. 
 
 1.2 (22.0) Stop sign. Turn left (SW) . 
 
 0.1 (22.1) DANGER . Railroad crossing. 
 
 0,2 (22.3) Turn left, then half-right on streets in PRAIRIE DU PONT. 
 STOP SIGN. Turn left (SE ) on Route 3. 
 
6 - 
 
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 4) 
 
 (35. 
 
 7) 
 
 (36, 
 
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 (36. 
 
 5) 
 
 (37. 
 
 9) 
 
 (38. 
 
 5) 
 
 Caution. Railroad crossing. DUPO. 
 
 Leave DUPO. 
 
 Note derricks of Dupo Field on flat to east; steep southwest dip 
 of Dupo Anticline shows in Sugar Loaf Bluff to southeast. 
 
 Turn left (E) on Cement Hollow Road and repass outcrops of Stop 
 No. 2. 
 
 Forks, Continue ahead (E) in Cement Hollow. 
 
 Stop sign. Turn right (S). 
 
 BLIFFSIDE. Continue ahead (E). 
 
 Turn right (S) with blacktop. 
 
 Stop sign. Turn left (E) on Route 158. 
 
 Caution. Railroad crossing. 
 
 Enter MILLSTADT, 
 
 Stop sign in Mills tadt. Turn left (N). 
 
 Turn right (E) into Midvtfest Coal Company mine. 
 
 Office of Midwest Coal Company. 
 
 STOP No. 6. Strip mine in Coal No. 6 (Herrin Coal), Officials of 
 Midwest Coal Company will guide trip to strip mines. 
 
 The pit shows a typical succession of Illinois coal strata with 
 underclay present in the pit floor, upon which rests about 5 feet 
 of coal, generally overlain by 'V oof slate." This black slaty shale 
 contains conodents, small circular brachiopods ( Qrbiculoidea ) and 
 fish scales. (Conodonts are microscopic, sawlike teeth of unknown 
 origin). Above the roof slate is a zone of rock which varies from 
 place to place along the pit face. In places it is nearly all 
 limestone, in others gray or yellow shale. Marine fossils are 
 present, most commonly brachiopods and orinoid joints. 
 
 The different kinds of rock layers associated with the coal 
 reflect the changing environments of the time and region. Some- 
 times the area was a great delta region of rivers and sloughs, 
 sometimes it was occupied by vast coastal swamps, and sometimes it 
 lay under the salt water of the sea. The underclay is thought by 
 many to be the soil in which the coal swamp forests grew— the coal 
 to be the result of accumulations of decaying vegetation in the 
 great swamps— the roof slate to have been deposited in stagnant 
 

- 7 - 
 
 0.0 
 
 (38.5) 
 
 2.3 
 
 (40.8) 
 
 0.9 
 
 (41.7) 
 
 1.0 
 
 (42.7) 
 
 4.7 
 
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 1.4 
 
 (48.8) 
 
 3.0 
 
 (51.8) 
 
 2.1 
 
 (53.9) 
 
 0.8 
 
 (54.7) 
 
 lagoons connected with sea — the limestone and shale to have been 
 deposited in the waters of the-opensea — sandstones as well as shales 
 containing land plants (not seen in the pit outcrop) record 
 river, delta, and flood plain environments that stood for a time, 
 a little above sea level. Then the land would sink again and the 
 great coastal swamps, and finally the sea, return. In this way 
 the thousands of feet of coal-bearing strata in Illinois were laid 
 downi Here riiost of this thickness of Strata has been removed by 
 later erosiohi Farther west, as seen earlier .-on the trip, this 
 erosion has cut entirely through the Coal-bearing strata into 
 the Mississippian limestones which underlie them everywhere. 
 
 Reverse route to Millstadt, 
 
 Stop sign in MILLSTADT. Cross Route 158 and continue ahead (S). 
 
 Forks. Go left on Floraville Road. 
 
 Strip mine on right. 
 
 FLORAVILLE (on right). 
 
 PADERBORN. 
 
 Stop sign. Go right ( S) on Route 159, 
 
 Highway intersection. Turn left (E) on Route 156. 
 
 Park opposite entrance to quarry, and walk north to quarry. 
 STOP NO. 7. CHESTER LIMESTONE. 
 
 After the deposition of the thick St. Louis-Ste. Genevieve 
 limestone, conditions of the crust in southern Illinois became 
 more unstable so that only at times was the sea present, while 
 alternately land conditions prevailed. Thus marine limestone and 
 shale formations alternate with sandstone and shale formations 
 of non-marine origin. This succession of limestone, sandstone 
 and shale accumulated to a thickness of many hundreds of feet 
 and is called the Chester Group. 
 
 The Okaw limestone seen in the quarry belongs to this 
 group. Like many Chester limestones, it teams with fossils, including 
 many lacy bryozoa and the cork-screw Archimedes , as well as brachio- 
 pod shells crinoidal fragments, pentramites , and cup corals. It 
 is underlain by shale. 
 
 In the Waterloo area, the Chester beds are thin because most 
 of the strata were worn away by erosion before the deposition of the 
 Pennsylvanian coal-bearing formations. These latter also have since 
 been worn away from this spot. 
 
 END OF CONFERENCE. 
 
ERAS 
 
 GENERALIZED GEOLOGIC COLUMN 
 
 FOR THE WATERLOO AREA 
 
 Prepared by the Illinois State Geological Survey 
 
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 - —v.- — 
 
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 PERIODS 
 
 EPOCHS 
 
 FORMATIONS 
 
 Quaternary 
 
 Pleistoceno 
 
 
 
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 Tertiary 
 
 Cretaceous 
 
 Jurassic 
 Triassic 
 
 Pliocene 
 Miocene 
 Oligoccno 
 Eocene 
 
 ♦Recent post-glacial stoge 
 S *Wisconsin glacial stage 
 i ♦Sangamon interglacial 
 
 stage 
 I *Illinoian glacial stage 
 
 "Yarmouth interglacial 
 i stage 
 | Kansan glacial stage 
 
 Aftonian interglacial st. 
 .L._llabr-askan. glaciaX..s.tage~_ 
 
 j Not present in Waterloo 
 Area. 
 
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 j Present in extreme 
 southern, Illinois only 
 
 Not present in Illinois 
 
 Not present in Illinois 
 
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 Permian 
 
 Pcnnsylvanian 
 
 Mississippian 
 
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 Lower 
 
 oterozoic 
 cheozoic 
 
 Devonian 
 
 Silurian 
 
 Ordovician 
 
 Niagaran 
 Alexandrian 
 
 Cambrian 
 
 Not present in Illinois 
 
 ♦Including Herrin (No. 6) 
 Coal and associated beds 
 
 ._ at- Midwast Mine . 
 
 ♦including Okaw Limestono 
 
 ♦St. Genevieve Is. 
 *St» Louis Is. 
 ♦Sal em-Warsaw Is. 
 ♦Keokuk Is. 
 
 Not present in Waterloo 
 
 ! Area* 
 
 Dolomite in deep vrclls 
 Over 1,500' of strata. 
 
 No data 
 
 V Referred to as "Pre-Cambrian" time. No data 
 / ♦Deposits exposed in Waterloo Area 
 
; \*> 
 
- 8 - 
 
 GEOLOGICAL HISTORY OF THE WATERLOO AREA 
 
 BEDROCK FORMATIONS. 
 
 The bedrock v\rhich crops out in the western and southern parts of the 
 Waterloo area is largely of Mississippian age, but in the northeast, these rock 
 layers are covered by younger strata belonging to the Pennsylvanian, or Coal 
 Period. Deep wells drilled for oil or water encountered still older strata 
 of Silurian and Ordovician age, deposited for the most part, like the 
 Mississippian strata in ancient seas that invaded the interior of the continent. 
 
 Deeper wells at St. Louis and in Jersey County encounter still older rocks 
 below the Ordovician strata. These are marine limestone and sandstone of 
 Cambrian age, bearing the oldest clearly diff erentiablo fossils. Evidence 
 from the St. Francis mountains of Missouri, where the older strata have been 
 uplifted, as well as from the wells mentioned shov/s that the Canbrian formations 
 lie upon still, older rock masses. These oldest of rocks are largely granite and 
 related crystalline rocks which once cooled from a molten state as the roots of 
 mountain systems. Long before the coming of the Cambrian sea, these mountains 
 were beveled away by erosion to expose the granite "basement" upon which the 
 bedded rock layers of Illinois now rest. 
 
 MISSISSIPPIAN HISTORY. 
 
 The ancient lime-depositing seas persisted into Mississippian time and laid 
 down Lower Mississippian limestone strata hundreds of feet thick. Later in 
 Mississippian time the earth's crust in this region became somewhat unstable 
 so that gentle rises and recessions of sea level caused an alternation of salt 
 and freshwater conditions. When the seas advanced, limestones and marine 
 shales full of the fossils of sea life v;ere laid down. When the sea retreated, 
 streams, lakes, and lagoons received deposits of fresh water shales and 
 sandstones, sometimes entombing fragments of land plants. 
 
 Finally the land rose a sufficient height above the sea to suffer the 
 attack of erosive forces, which cut away hundreds of feet of the recently 
 deposited strata. 
 
 PENNSYLVANIAN HISTORY. 
 
 In the Pennsylvanian or Coal Period which followed, the land again began 
 to sink gently, but seas only occasionally reached this region. Most of the 
 shale and sandstone which makes up the bulk of the more than 2,000 feet of 
 Pennsylvanian strata which accumulated in Illinois, thus was formed on land or 
 in shallow fresh water. 
 
 At that time, in the vicinity of the present Atlantic Coast, high mountains 
 were rising, that might be comparable to the present Andes. Between the 
 mountains and the inland seas that lay off to the west from Nebraska down through 
 Texas, there extended a hot and humid swampy plain crossed by rivers moving 
 westward from the mountains to the sea. The region may be likened to the Amazon 
 Basin which today stretches eastward from the foot of the Andes. 
 

- 9 - 
 
 At times the sinking of the lowland permitted the sea to extend far to the 
 east and deposit fossiliferous limestone and shale over Illinois. At other times 
 vast jungle swamps accumulated dense vegetation, which, falling in the poisonous 
 waters, was preserved from complete decay to form our valuable coal beds. But 
 for the most part, the low land was occupied by rivers, shallow lakes, and bayous 
 in which mud and sand, washed out from the mountains, came to rest to form shale 
 and sandstone. The piling up of thousands of feet of this sediments helped to 
 compress the peaty layers of vegetation into coal, 
 
 THE LOST INTERVAL. 
 
 Following Pennsylvanian time, the land rose to a moderate elevation above 
 the sea and apparently was never again covered by marine waters. Under these 
 conditions, erosion by streams and the weather slowly cut down the land, and in 
 the Waterloo area in places cut away all of the Pennsylvanian formations down to 
 the Waterloo rock. The disintegrated rock was carried away as sand, gravel, and 
 mud by streams and rivers, to be deposited in areas remote from this region. 
 Thus it is that we have no direct evidence of the life and environment here 
 during the Age of Reptiles and the Age of Mammals that followed. 
 
 ICE AGE HISTORY. 
 
 The glaciers which relatively recently moved down into Illinois from the far 
 north wrote the last chapter of the geologic history of the region. During tho 
 Pleistocene period (or Ice Age), glaciers invaded Illinois, not merely once, but 
 four times, and each ice invasion was separated from the next by a long mild 
 interval of 100 to 300 thousand years. During these mild intervals plant and 
 animal life returned, soils formed, and conditions were not greatly different 
 from what they are today. In fact, there is no way of knowing but what we are 
 living today in just such an interval that will be terminated a few hundred 
 thousand years hence by a fifth ice advance. 
 
 Only one of the glaciations, the third or Illinoian, reached the Waterloo 
 region, but glacial conditions farther north effected the climate, geology, and 
 topography in tho Chester area, especially through the agency of the Mississippi, 
 The great river carried tho melt waters and the sediments from the wasting 
 glaciers farther north, and was the source of the loess, blown from the river 
 flats onto the uplands to the east. 
 
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DEEP WELL RECORD 
 Based largely on Tarlton-Dyroff test well, Dupo Oil Field, St. Clair County 
 
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 Sil, 
 
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 Oil 
 
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 Burlington Limestone 
 Choteau-Fern Glen shaly limestones 
 _Si i.ur ! J? J$&E22£1 ian li meston e 
 
 Maquoketa shale (with thin limestones) 
 Kimmswick-Plat tin- Joachim limestones 
 
 St. Peter sandstone 
 
 Ever ton sandstone and dolomite 
 
 Powell-Jefferson City-Cotter cherty magnesian limestones 
 
 Roubidoux sandstone 
 
 Gasconade cherty magnesian limestone 
 
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 Shale, gray, sandy at top ; contains marine fossils and ironstone 
 concretions especially in lower part. 
 
 Limestone ; contains marine fossils. 
 
 Shale, black, hard, laminated ; contains large spheroidal concre- 
 tions ("Niggerheads") and marine fossils. 
 Limestone ; contains marine fossils. 
 
 Shale, gray ; pyritic nodules and ironstone concretions common at 
 base ; plant fossils locally common at base ; marine fossils rare. 
 
 Coal ; locally contains clay or shale partings. 
 
 Underclay, mostly medium to light gray except dark gray at top ; 
 upper part noncalcareous, lower part calcareous. 
 
 Limestone, argillaceous ; occurs in nodules or discontinuous beds ; 
 usually nonfossiliferous. 
 
 Shale, gray, sandy. 
 
 Sandstone, fine-grained, micaceous, and siltstone, argillaceous; 
 variable from massive to thin-bedded ; usually with an uneven 
 lower surface. 
 
 AN IDEALLY COMPLETE CYCLOTHEM 
 
 (Reprinted from Fig. 42, Bulletin No. 66, Geology and Mineral Resources of the Marseilles, 
 Ottawa, and Streator Quadrangles, by H, B. Willman and J. Norman Payne) 
 
CD 
 
 (A 
 
 H 
 
 o 
 
 o I 
 
 7\ m 
 
 7 > 
 
 5 < 
 
 -e 
 
 m5 
 
 3J 
 
 ^ 
 
 0)