I "3 ^» State of Illinois Department of Registration and Education STATE GEOLOGICAL SURVEY DIVISION John C. Frye, Chief 4JW &i )« H H GEOLOGICAL SCIENCE FIELD TRIP Sponsored by ILLIWOIS STATE GEOLOGICAL SURViSY, URBANA W>$ *¥ ll'ICN AREA Rock Island County Port Byron, Cordova, and Erie Quadrangles \ ) \ S ~J Leaders George M. Wilson and George E. Ekblaw Urbana, Illinois September 17, 1955 ILLINOIS GEOLOGICAL SURVEY LIBRARY OCT 22 1963 GUIDE LEAFLET 1955D Port 3yron Geological Science Field Trip ITT-: l .a 0.0 0.0 Port Byron 1 : gh Schc Assemble r'a Parking Area behin. 1 . the school. Approach th. road sign and stop h^rore entering Route 80. Turn left (south; . 0.5 0,5 Note the abandoned quarries in Silurian rocks on right and left. 0.6 1.1 Slow. 0.1 1.2 Turn left (east) on T-road. Note that the top of bedrock is at about 600 feet above sea- level. Keep this elevation in mind. 0.2 1.4 Bear left. 0.9 2.3 Note the dissected loess surface on the upland. 0.2 2.5 STOP 1 . Soil profile in ravine. The glacial history of the Port Byron area is complicated. We find glacial drift, loess, glacial silts, sand dunes, gravel, and gumbo- til. At least three times glacial lakes occupied the area during the last stage of glaciation, the Wisconsinan. Many factors in- fluenced the development of the topography and the drainage system. In preglacial times, the ancestral Mississippi followed the present Mississippi channel to the vicinity of Cordova where it turned south- east and flowed to the Big Bend near Hennepin on the present Illinois River. The bedrock hills and valleys, developed by flowing streams, formed the topography at the beginning of the Ice Age. The glaciers that covered Illinois and the northern part of the North America spread out from various centers in Canada, chiefly east- central and eastern Canada, at different times during the periods of glaciation. Glaciers accumulate when the mean average temperature is so low that the winter snows do not all melt during the following summer, and the accumulation goes on for hundreds, perhaps thousands, of years. The weight of the ice mass finally makes it flow outward. We have evi- dence that glaciers advanced as far south as the Missouri and Ohio rivers and south of Carbondale and Harrisburg in Illinois. The principal stages of glaciation are named Nebraskan, Kansan, Illi- noian, and Wisconsinan. Between the glacial stages were warmer inter - glacial stages at which times soils and profiles of weathering devel- oped on the deposits of earth materials left by the glacier . When, for some reason, mean annual temperatures rose, the glacial ice began to melt and thus halted the advance of the glacier. The earth material that had been picked up and frozen into the advancing ice was then dropped. Where it is an unsorted mixture of clay (rock flour), pebbles, or boulders, it is called till . The melt water pouring out from the ice carried with it much of the finer material such as sr.nd, silt, and pebbles. The water-sorted material is called outwash. The coarser outwash material was depo- sited near the ice front, the finer materials further away. Where the outwash material was dropped widely as a sort of apron in front of the ice it is called an outwash plain: where it was dropped in valleys which drained away from the melting ice it is called a valley - train . Geologists think that during the winters the melt waters subsided so that the outwash plains and valley-trains were exposed to the wind. The wind picked up silt and fine sand, blew it across the country, and drop- ped it to form deposits of loess . A covering of loess is found almost everywhere in Illinois, much thicker near the large valleys. In some places near the old stream valleys the loess is as much as 20 feet thick. The Port Byron area has glacial deposits from the Kansan, Illinoian, and Wisconsinan glacial stages. The Kansan till is found only in isolated areas and we will not see it on this trip, but we will see both Illi- noian and Wisconsinan deposits. During the Illinoian and Wisconsinan stages of glaciation, the ancestral Mississippi River, flowing southeast across northwestern Illinois, was blocked by ice and the diverted river was forced to cut other channels. Stop 1 is on the dissected loess-covered upland. In this valley the out* let was blocked and silt was deposited. Later a rich mucky soil develop- ed on the silt. Still later the valley was blocked again so that an- other layer of silt was deposited on top of the soil. At the same time wind-blown loess was being deposited on the hills along the edge of the valley. The section you see here is as follows: Thickness Upper Profile in the edge of the valley: Ft. In. Soil, gray, loessial 8 Loess, clayey, weathered, non-calcareous, brown- tan 2 Covered interval Lower Profile Silt, fine grained, laminated, with inclusions of peat and carbonized twigs 3 Soil, black, carbonaceous, mucky 2 Silt, dark gray, carbonaceous, clayey, fairly micaceous \o Silt, finely micaceous, gray with brown iron- stains 3 Continue east on upland. Descending a tributary of Zuma Creek. STOP 2 . Road cut. Section along road cut. Thickness Ft. In. Peoria Loess, largely grass-covered 15 Soil, carbonaceous, dark gray, very clayey ... 2 6 Thickness Illinoian Ft. In. Till, brown, weathered, leached, non-calcareous . . 6 Till, reddish-brown, pebbly, slightly calcareous . 1 Bottom of ditch. 0.2 5.7 Note pebbly till along the road ditches. The cut on the right side of the road is capped by 25 feet of buff loess. Here you have a view across a valley tributary to the ancestral Mis- sissippi River. It flowed northeast and emptied into the ancestral river just east of the middle of the wide valley. 0.2 5.9 STOP , Turn right (southwest) on Route 2. You are now driving along the north edge of the old valley; the south edge of the island upland is on your right. 0.7 6.6 Caution! Intersection with Route 92. Turn left (south) on gravel road. 0.8 7.4 Turn left into quarry yard and turn around so that cars are headed out and along roadway. STOP 3 . Soil Profile and Midway Quarry. CAUTION - DO NOT CLIMB ON THE WALLS OF THE QUARRY. We are now in the preglacial valley which drained the south side of the Cordova rock "island" and the area as far south as Andalusia. The water flowed northeastward and emptied into the ancestral Mississippi just to the northeast. At a later time the Mississippi flowed southwest into this valley. The soil profile in this valley is not clearly understood because the valley has had such a varied history. The section is as follows: Thickness Recent Ft. In. Soil, surficial, black, mucky, friable, with igneous and met amorphic pebbles 1 3 (?) Till, black, carbonaceous, clayey and pebbly ... 10 Till, as above, also containing many dolomite pebbles 8 Till, reddish-brown, clayey, gravelly, probably occurs only in pockets in the top of the bedrock. 6 Silurian-Port Byron formation Dolomite, ranging from dense and fine to coarsely crystalline, contains numerous fossil casts and molds. Beds inclined from 5 to 35 degrees, owing to effect of being draped over the surface of a coral reef. There are interbedded shales at various zones. The core of the reef has been quarried away. Such coral reefs as this, buried deep in the earth, have been found to contain petroleum in the western portion of the Illinois oil fields. The Tilden oil pool near Sparta, Illinois, is an example of an oil pool in such an old coral reef. As a matter of fact, even in the Chicago area the Silurian rock is oil-stained and contains residual asphalt. Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/guideleafletgeol1955wils 4 In the dolomite you will find such fossils as corals, crinoids (sea lilies), gastropods (snails), pelecypods (clams), cephalopods, and brachiopods. Fossils are abundant, but STAY OFF THE QUARRY WALLS. 0.8 8.2 Return to Highways 2 and 92. STOP ? Turn left (west). 0.6 8.8 Turn right (northwest) on gravel road. 4.1 12.9 Turn right (north) on Route 80. 1.3 14.2 Turn right (west) at corner opposite the Standard Oil station. 0.2 14.4 Enter Dorrance Park. STOP 4 - LUNCH . After lunch, assemble for discussion of the glacial history of the region. 0.2 14.6 Proceed to Stop Sign on north edge of Dorrance Park. Turn left (west) on pavement. 1.2 15.9 We are passing through the Narrows or the Cordova Gorge along this road. During the Sangamonian interglacial stage and the Iowan substage, small streams drained the Cordova rock "island." During Woodfordian(Shelbyville) time, glacial Lake Cordova occupied the area; its outlet waters breached the small divide at an elevation of about 640 feet and then cut the gorge or "narrows" that we see. 1.9 17.8 Continue on Route 80 following the "narrows." 0.3 18.1 Turn left (west) on gravel road. Caution - R.R. crossing. Turn around and park. STOP 5 . Discussion of the development of the Cordova Gorge and visit to the Collinson quarry. The quarry is in the Racine formation of Silurian age. The rock is poorly stratified here because it is in a series of small reefs or bioherms. Like the Port Byron formation which we saw this morning, the Racine is quite fossiliferous. 0.3 18.4 Return to Route 80. Stop. Proceed across the road, pull well off the highway. 0.1 18.5 STOP 6 . Here we see a section as follows: Thickness Ft. In. Soil, gray, sandy 1 Silt, hard, clayey 4 Sand, gray, fine 0-6 Silt, reddish-brown, in irregular lenses, with inclusions of tan silt 2 Sand Since the sediments here occur below the elevation of 640 feet, it is obvious they were deposited after the Cordova Gorge was cut, because they would have been washed away during the cutting of the gorge if they had been deposited previously. The sediments are cross-bedded and are f •( : I . inclined in a northwesterly direction. Pull onto road cautiously. Continue north on Highway 80 1.4 19.9 We are now at the north edge of the "island upland," as well as at the north end of the Cordova Gorge. The terrain here has an average eleva- tion of 600 feet. In the broad valley to the north the ancestral Mis- sissippi River was joined by the ancestor of Wapsipinicon River which flowed from the west. (See diagram). 0.2 20.1 Turn right (east) on blacktop road at the Standard Oil filling station. Note on the right the abandoned kilns where Silurian dolomite was once burned to make lime. Eastward the limestone crops out at an elevation of slightly more than 600 feet. This rock ledge forms the south valley wall of the ancestral Mississippi River which at some time in the past was cut as much as 300 feet below the present surface but was later filled with glacial materials. 1.9 22.0 Road turns right (south). 0.4 22.4 Note the sand dune area on the left; it covers about three-fourths of a square mile. 0.2 22.6 Road turns left (east). 0.6 23.2 On right, note the isolated outcrop of limestone at the boundary of the island upland. 2.6 25.8 Along this road we descend to a lower level terrace which has an average elevation of 580 feet, an elevation only a little above the level of the river near Cordova. Turn around at T-road north. 0.2 26.0 Road bends left. View ahead shows the edge of the 600-foot terrace. 0.8 26.8 Turn left (south) at T-road. 0.4 27.2 We are climbing the north boundary of the island upland. The rock terrace merges with the lower part of the island upland. STOP 7 . The general upland surface is at an elevation of approximately 650 feet and is characterized by hills alligned northwest-southeast, indicating that glacial melt waters of Shelbyville age passed over the area. Sand dunes cap some of the higher hills in the area. The section at the north end of the cut is as follows: Thickness Ft. In. Soil, weathered, gray, noncalcareous 10 Loess, oxidized, leached, brown, grades down to 12 Loess, noncalcareous 2 Silt, tan to brown, noncalcareous 1 Loess, pinkish 5 Loess, tan to brown, with plant stems (?) 1 6 """■" ■." ,is >>: ■■•' ■*•,.:■. 6 At the south end of the cut, two gray soils are developed at or near the surface. 0.3 27.5 Note on the left the elongate ridge which trends northwest-southeast. The upper portion of the ridge is sand. 0.7 28.2 Fine sand is exposed in banks of cut. In the last 0.3 mile we have crossed from an area covered with Wisconsinan glacial deposits onto an area covered with Illinoian glacial deposits, each having characteristic topographic expression and different mean elevations. STOP 8 . The cut, here entirely in loess, is as follows: Thickness Ft. In. Soil, gray, loessial 8 Loess, brown, weathered 2 Loess, brown, with nodules 6 Loess, gray, leached, oxidized 18 The loess mantle seems thicker here than at the last cut. The loess was laid down over an irregular surface, and headward erosion of the streams further dissected the surface. 1.5 29.9 Turn right (west) on gravel road. 1.4 31.3 Turn left (south). 5 31.8 STOP 9 . On the upland surface the section is as follows: Thickness Ft. In. Soil, gray, loessial 1 6 Loess, weathered, brown, non-calcareous 1 6 Loess, brown, weathered, with "ferreto" zone 2 Loess, plastic, with iron stain 2 Sand, brown, medium to fine-grained 4 0.5 32.3 Stop for paved road. Turn right to return to Port Byron or Turn left to go to Hillsdale and Route 2 Reprinted— 1962 f^o^Goose Lake fc-Xfc y! • r-v-. ;.:•. ... - • i ^/.Elvira - ^7a ?»£«£.- Cattail r/ Channel s " Morrison Sterling' "\ ■mceton j ^LeCl\ir>^ ^il^fefe^ tel rj i^y Glacial and Recent Allu- vium Tazewell drift) \ Iowan drift )Wisconsi«an Illinoian drift / ¥77} Kansan drift \ ©Shelbyville over Kansan gum- * Garden Plain / botil. eskerine tract. / RTver Green Geneseo 3 10 miles Glacial geology of the Port Byron area, from Illinois Geol. Survey Rept. Inv. No. 174, by Paul Shaffer. The entire area was covered first by the Kansan and then the Illinoian glaciers, After each glaciation the Mississippi River and its principal tributaries, Wap- sipinicon and Pleasant rivers, regained their courses. When the Shelbyville glacier of the Tazewell substage of Wisconsinan age ad- vanced from the east, it blocked the streams and created Lake Milan, which had its outlet westward and southward from Andalusia. When the Shelbyville glacier reached Hillsdale, it raised the lake level in the Mississippii and Wapsipin- icon valleys until the water escaped over a col in what is now the Cordova Gorge, cutting the valley deeper and deeper. When the Shelbyville glacier reached its maximum advance, the lake in the upper Mississippi valley was raised still higher, and its waters escaped in a round-about route westward through Maquoketa valley, south through Goose Lake Channel, and east along the ice front to the Cordova Gorge. When the Shelbyville glacier melted, the Mississippi River followed a new course through the Cordova Gorge and Andalusia outlet. - 8 GLACIAL STAGES IN THE PORT BYRON AREA NORTH AMERICA Wlsconsinan Stage Valderan Sub stage Two Creekan Substage Woodfordian Substage Farmdalian Substage Altonian Substage Illinoian Stage Kansan Stage Nebraskan Stage DIRECTION OF APPROACH Period of Retreat From East & Northeast Period of Retreat From Northeast From East From Northwest From Northwest PORT BYRON AREA Closest - Central Wisconsin Crossed Mississippi River near Cordova Mt. Carroll - Sterling area Reached Mississippi River at Albany and crossed above Cordova Passed over entire area Unknown Even the glaciers which halted a long distance from the Port Byron area in- fluenced its geology considerably. When glaciers melt away, they liberate great amounts of water loaded with mud, sand, gravel, and boulders. The earth materials wash down the streams and into the great rivers that flow away from the ice. Such streams as the Mississippi River became choked with sediment which built up the valley floor until the river flowed hundreds of feet above its former level. Winds blowing across the sand and mud flats picked up the dust and sand, deposited the sand as dunes along the sides of the valleys, and deposited the dust as loess over the uplands adjacent to the valleys. GENERALIZED GEOLOGIC COLUMN FOR PORT BYRON AREA ERAS t-l -H O f-l N O 4-> c c Q> 4) O O a) a O 0} N «-• O "O 09 T3 0) '-I ~7" o -i so £ PERIODS Quaternary Tertiary EPOCHS [Pleistocene { .- Pliocene ! Miocene ;01igocene 'Eocene iPaleocene REMARKS Till, loess, and dune sand on uplands; outwash, lake silts and alluvium in river valleys Not present in Port Byron area CO O -< •H m c$ CO 4J co c d n) CO i-H •H O., •H ►»; Ji *-* § ca . co CD CO •l-l in Cretaceous Jurassic Triassic Permian Pennsylvanian Mississippian Devonian i Cayugan Present only in extreme southern Illinois Not present in Illinois Not present in ^Illinois Not present in Illinois Present in small areas Not present in Port Byron _ jax&a.. ... _ . Present in Moline area Not present in Port Byron ...JUCfiA. ■u Silurian 0) c cO «-l d) S-i CO i-l Xi Ph u 0) 1 4J | cu > c M i O ; Ordovician Plate COMMON TYPES of ILLINOIS FOSSILS Cup coral GRAPTOLITE Lithostrotion CORALS Honeycomb coral Archimedes Fenestella Branching BRYOZOA PENTREMITE Lingula Orbiculoidea Spiriferoid Productoid Pentameroid BRACHIOPODS Plate 2 Common Types of Illinois fossils "Clam" sir- "Scallop" PELECYPODS Curved cone Coiled cone (Nautilus) Straight cone CEPHALOPODS High- spired Bumastus Low - spired Flat - spired GASTROPODS Calymene (coiled ) Calymene (flat) OSTRACODS (greatly enlarged) TRILOBITES M MC. "•""•wAVMItt 1/3