Mn-0 s, 9> «v^- „ *« Caput STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION STATE GEOLOGICAL SURVEY DIVISION Morris Mr Leighton, Chief V/A.R3A../ AREA Hancock County OUIDF, LSAF&ET ^7 D Gilbert o. Raasch **V September 27, 1947 $$ ifi Urbana, Illinois . y- Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/warsawareahancoc1947raas -1- ITINERARY. 0.0 Warsaw Community High School, 0.0 Go Worth on city street. 0.2 Stop. Warsaw Highway; turn right (east) on Highway. From Warsaw to Hamilton route is chiefly over upland underlain by Illinoian till and post-Illinoian loess. Occasionally the road dips down as it crosses the heads of rocky glens where post-Illinoian streams have cut down to bed-rock* 3.2 Cross Crystal Glen (west Fork), famous geode collecting locality. 3.5 STOP NO. I. (At junction of Highway 96 with Warsaw Highway). Stop to examine Warsaw shaly limestone and collect geode s. Continue East on Highway 96. 4.0 STOP NO. II. Pre-glacial (tertiary?) gravel underneath glacial tills. Exposed in gravel pits to NW and SE of road corners. Descending section taken in the NW pit. Loess and soil 1 foot thick Illinoian Drift 3 to 4 feet thick Buff till, leached and weathered; containing numerous fragments of crystalline rocks, granite and gabbro. Upper 18 inches of this bed is maroon in color and has a some- what waxy matrix; this "gumbotil" is the result of decomposition of silicate minerals in the till and of deposition of colloidal clay material carried downward by descending surface water. Kansan Drift (?) average, 2 feet thick (Observed in the SE pit). Till, more highly weathered than over- tying* f rom which it is separated by a distinct break along a wavy line. Crystalline rocks are chiefly small pebbles. Color, inter- mottled pale ashy and terra cotta. Tertiary (?) Deposits. Over 13 feet thick Upper two thirds coarse gravel, locally cemented by limonite. Pebbles of local material, very highly polished; subangular chert most abundant, highly rounded quartz pebbles common; fragments of geodes present, also masses of indurated sandstone. Lower third chiefly sand, clean, coarse, poorly sorted, irregu- larly iron-stained, cross-bedded. Near base of exposure is a loca lense of fine sandstone over and underlain by very fine, ashy gray silt. This is lowest sediment exposed; there is a short concealed interval down to top bedrock (Warsaw) exposed in stream bed. Stream is Crystal Glen Creek (East fork); geodes abundant in creek bed. 5.7 Highway turns north; continue on highway. 7.4 Railroad crossing in valley of Railroad Crook, famous for geodes. 7.8 Enter Hamilton. Continue straight ahead. 8,2 Stop. Junction Highways 10 and 96; turn left (West) on 96-10. 8.5 STOP HO. III. LUNCH STOP. In Hamilton City park on left (South) side of Highway. 8 .6 Leave park and continue west on 96-10. 8.9 Turn right (North) on Highway 96, Note Keokuk Dam and hydroelectric plant on left. 13.3 Bridge over Waggoner Creek. -2- 111. 5 STOP NO. IV. Quarry in Mississippian formations on North bank of Creek. Lower 20 feet is Keokuk Limestone, overlain by about 30 feet of clayey limestone and limey shale. Mote gradation from Keokuk beds into Warsaw beds. Small geodes stud some Warsaw layers. 1S>.0 STOP NO. V. Park in Mt. Mariah picnic ground. Brief stop to observe Mississippian formations, Warsaw formation below grading upward into Salem beds, which are in turn overlain by sandy limestones of the St. Louis formation. 17.6 STOP NO. VI, Quarry in Mississippian Beds on right exposes 23 feet of very fossiliferous Keokuk limestone overlain by about 8 feet of shaly, weathered Warsaw limestone with abundant geodes. 20.6 Leave highway and turn left on first street of Old Nauvoo, the Mormon capital up to 181^6 < The Historic marker on the right side of the highway reads as follows: "In 1839 the Mormons, or Latter Day Saints, settled at Nauvoo and made it their chief city. During their residence its population reached 15,000. After long friction with non-Mormons, the Mormons were expelled in 18I;6. Three years later French communists, called Icarians, established a society here which lasted until 1857." 20.9 Turn right (North) at Joseph Smith homestead. 21.7 Crossroad; road to right goes to Nauvoo and Highway 96; continue straight ahead. 21.9 Quarry entrance. Continue on road to left and park at north end of quarry. 22.1 STOP VII. Quarry in Burlington Formation of Mississippian Age. The Burlington formation lies just below the Keokuk formation, into which it grades. The limestone of Burlington Age has fewer fossils than the Keokuk and tends to be thicker bedded. BON VOYAGE J -3- GEOLOO-IC HISTORY OF THE WARSAW AREA The oldest rock which crops out in the Warsaw Area is the Burlington Limestone of Mississippi an Age, A glance at the geologic column will show you that the Mississippian Period is lato Paleozoic in age, and just precedes the abundantly coal-bearing Pennsylvanian in geologic time. All of the bed-rock outcrops visited on the present trip represent some part of the Mississippian System* DEEPLY-BURIED STRATA However, deep wells drilled in the area for oil or water, reveal older formations of Devonian and Ordovician age buried beneath the present Surface* Evidence from even deeper wells in adjoining areas shows that below the Ordovicic strata are Cambrian sandstones and dolomites* The Devonian, Ordovician, and Cambrian beds originated as sediments, deposited for the most part in ancient seas that flooded the interior of the continent. These sediments, in spite of their great age, have undergone little change except that involved in hardening into sandstone, shale, and limestone. They lie in nearly horizontal layers from the surface down woll over a thousand feot. Finally, below the Cambrian sand- stones is a twisted complex of crystalline igneous and metamorphic rocks of Proterozoic and Archaeozoic age. These are sometimes referred to as the basement complex, are deeply buried in Illinois, but come to the surface in northern Wis- consin and the region surrounding Lake Superior* DISTURBANCE OF THE BED ROCK Although the bedrock layers cropping out on tho surface have the appeal ance of being horizontal, they have in fact been broadly and gently warped by movement of the earth* s crust. For example a broad dome exists between Warsaw and Hamilton, whereas a broad trough is present north of Hamilton. This is why the geode-bearing strata in some places crop out high up in the glens, while at other pla ces they lie close to Mississippi River level. MISSISSIPPIAN FORMATIONS The outcropping Mississippian strata fall into three natural groups, oi which the lowest is the Burlington-Keokuk, the next the Warsaw-Salem, and the highest the St. Louis Formation. The Burlington-Keokuk consists of limestone strata, gray to white in color, crystalline, and crinoidal. Chert is abundant in some layers and vugs of calcito are common. The Burlington Limestone lies for the most part below river level, but may be seen near Nauvoo (Stop No. VII ). The Keokuk Limestone, which is 70 feet thick, is more highly fossiliferous than the underlying Burlington an<" tend to be grayer,monDogranular, and more thinly bedded. Both formations were deposited in marine waters, as is clearly shown by tho fossil remains. The two formations are well known for their crinoids, but many other types of organisms occur, including cup-corals, bryozoa ("moss animals"), brachiopod, pelecypod, anc gastropod shells, tho heads and tails of triobites, and the bones of primitive fish. Most conspicuous among the many types of brachipods is the giant Derbya , which sometimes exceeds 4 inches in width (present at Stop No. V). -4- WARSAW-SALEM FORMATIONS Like the Burlington-Kookuk, tho Warsaw and Salem formations arc groupec together because the former grades upward into tho latter. The two formations combined have a thickness of 75 to 90 foot. The lower unit, the Warsaw, is made up of dull gray layers of limey shalo and clayey limestone Fossils arc not common, but this lack' is: compensated by the abundance of goodos which wash or weather out of the soft rock and stud water courses and hillsides. Tho Salem formation is a porous, granular, highly fossiliforous limestone lying above the Warsaw and intor fingering with it. WARSAW GEODES The Warsaw Formation is world renowned for tho abundance and variety of its goodos. Those crystal-lined, or crystal-filled bouldory masses, have a rough shell of chalcedony inside which a variety of minerals may occur. Most common is quartz (rock crystal), but chalcodony, calcito, dolomite, ankerite, and kaolin aro common, while sphalerite, marcasitc, aragonite, millerite, chalcopyrit and petroleum arc' sometimes present, as well as such secondary minerals as limo- nite, smithsonite, malachito, and gypsum. According to Van Tuyl»s thoory, geodes originated from tho dissolving away of previously existing concretions in tho shales, which has left cavities on the walls of which the minerals crystallized and continued to grow until in some cases they completely filled the cavity. ST. LOUIS FORMATION The St. Louis Formation is not well exposed in tho area covered on tho trip. It is peculiar in having many layers made of limestone pebbles cemented to form breccia and conglomerate. At least at tho beginning of St. Louis lime- stone deposition, waters appear to have been shallow, allowing wave action to rip up and redeposit previously formed limestone layers. In places, sand washed into the sea to form sandstone and sandy limestone But in other places, waters wore sufficiently clear to allow large coral reefs to develop, made up principally of tho coral Lithostr otion canadenso . LATE MISSISSIPPIAN Ht STORY Tho St. Louis Limostono is tho youngest Mississippian formation found in tho -/or saw Area. It seems probable, from a study of other regions, that many hundreds of foot of strata wore deposited in Mississippian time above the St. Loua bods. At tho close of tho Mississippian, and before inundation by the Ponnsylvani Sea, the region vms a land aroa, subject to tho wearing down process of erosion. PENNSYLVANIA^ HT STORY i n ^f^ rcmmnts of Ponnsylvanian sediments lying high in the hills show clearly that when the sea returned to this region in Ponnsylvanian time, tho Mississippian strata down to tho St. Louis Formation had been stripped away. How great a thickness of Ponnsylvanian sediment once overlay the region is not known; it is logical to suppose, from evidence farther east in Illinois, that the thicknc was considerable -5- MESOZOIC AND CENOZOIC HISTORY Since the withdrawal of tho Ponnsylvanian Sea, tho region has not boon inundated by marine waters. In the millions of years which have intorvoned be- tween the Pennsylvanian and the present, tho region has boon a land area under- going erosion* By the timo of the coming of the Pleistoceno glaciers, this erosion had removed nearly all of the Pennsylvanian strata with their rich coal bods, and had cut dooply into the Mississippian, as already mentioned. This loft a fairly rugged topography like that presont today in tho unglaciatod portions of northwest Illinois and southwest Wisconsin. Those irregulurietios wero largol filled up by glacial dobris to tho prosont level of tho flat upland, Sinco the . withdrawal of tho last ice shoot from the region, erosion in placos has once again cut down through tho mantle of glacial material to carvo tho ravinos and glons along the rivor* PRE-GIACIAL GRAVELS It is raro in the glaciated portion of Illinois to find any ovidenco of events which took place during the long interval between Pennsylvanian and Pleistocene time* Gcnorr.lly the glacial deposits of our geological yestorday lie directly on the vory old Mississippian and Pennsylvanian strata* Occasionally, however, deposits let or than Pennsylvanian and earlier than Pleistoconc intorvenc Such deposits are in the nature of gravel and sand left behind by the streams of pro-glacial timo. That they anto-dato the glaciors is proven, not only by the fact that they lie below tho olxlost glacial deposits, but also by the fact that all of the pebbles aro of local matorial, whore glacial doposits contain a groat mixture of rocks, some of which may havo travclod a thousand miles from thoir place of origin* One of the best of theso pro-glacial gravel deposits occurs in tho Warsaw area (Stop No. II). Horo many of tho pebbles are highly polished, suggest ing action by wind and sand blast in an arid rogion. Similar pebbles are typical of lato tortiary gravols of western United States. In the absonco of bones or othor fossils to date the Warsaw gravel, wo can only guess at its approximate age Although much of the material in the gravel suggests the effect of wind action, it came to its final rosting placo in the bed of a fairly largo stream which flowed in some unknown age at a level about 160 foot abovo tho prosent Mississipp GLACIAL HTSTORY during the Pleistocene Period (or "Great Ice Ago"), North America oxporiencod four succossivo glacial invasions, each separated by long intervals of mild climate* Of these four invasions, tho earliest, the Nobraskan, probably reachod the Warsaw aroa, but dofinito evidence is Hacking* The second, or Kansa invasion, moving down from tho region west of Hudson Bay, extended across our aroa and southeast beyond Pitt sfi old* When tho Kansan ico sheet melted away, it loft beyond its "glacial drif rock and debris xvhich mantled tho surface and concealed tho bod-rock. There followed a long interglacial intorval (the Yarmouth Stago), which loft its record in tho form of old soils and wo at ho rod zones on and in the Kansan glacial drift* 1 . % 5 - 6 - From the amount of weathering and leaching that affected the Kansas drift, the length of the Yarmouth Interglacial Stage is estimated at from 200,000 to 300,000 years. The Yarmouth Xntcrglacial Stago was terminated hy tho advanco of a new glacier, this time coming from tho northeast, from a center of accumulation oast of Hudson Bay. This Illinoian Ico Shoot is woll named, for not only did it covor nearly all of Illinois, but its western termination coincides closely with the western boundary of the State. At Warsaw, we are within four or five miles of the western limit of Illinoian glaciation, which here extended a few miles into Iowa. In the gravel pit (Stop No. II), we see two glacial tills lying upon pre-glacial gravel. Here, we cannot be sure that the lower till is truly Kansan, because the soil of the Yarmouth Interglacial Stage, if once present, was removed by or before the advance of the Illinoian Glacier. After several scores of thousands of years, climatic conditions caused the melting away of the Illinoian Ice Sheet. During this warm stage, the upper part of the Illinoian till was weathered and soil developed, just as in the case of the preceding Yarmouth Interval, However, this action did not take place to the degree it did during the Yarmouth, so that the post- Illinoian (Sangamon) interval is estimated to have lasted only about 150,000 years. The Sangamon Interval was brought to a close by the fourth and final readvance of the glaciers. This Wisconsin Ice Sheet never reached the Warsaw Area, although it threatened it, first from the northwest, later from the north- east. It left its mark on the region, nevertheless* The Mississippi and other streams were choked with sediment washed out from the ice fronts that stood to north^ west, and east, The frigid blasts that whipped across these broad sand and mud flats caused violent dust storms. The dust accumulated on the uplands and covered the Illinoian drift and Sangamon soils with a thick layer of loess. This ashy loess, over most of the Warsaw upland, grades into the soil of the present day. GLACIAL HISTORY OF THE MISSISSIPPI RIVER At the beginning of, or early in the history of the Great Ice Age, ther was no great master stream flowing along the course of the present Mississippi River in the Warsaw Area. Tho great river left its channel above Rock Island and swung eastward as far as Hennepin, below which its course approximated that of the present Illinois River. But when the Illinoian Glacier moved down from tho northeast it blocked the Mississippi between Savanna and Fulton and forced it to turn westward around the ice lobe. The river then had to cut a now course west even of its present on this old course can be traced today through Iowa a score of miles, more or less, west of the present river. Thon when the great ice dam melted away, the river found a short cut and abandoned that portion of its old channel which lies between Cordova in the north and Keokuk in the south. GENERALIZED GEOLOGIC COLUMN FOR THE WARSAW AREA ££g-^d ^X-tLh£Jllj g£i s State Geological Survey ERAS <2 o ►J N o -P a « © © O O © ' « o •H O N o w © o •H O o © O rH ID e <{ oS S PERIODS Quaternary TO t3 ►J -p © •H S < E Proterozoic Archeozoic m > r 5 0)