Paleozoic Geology of the Fox River from Batavia to Oswego, Illinois G-072007-2A 2007 Written By: Steven D.J. Baumann, Teresa Arrospide Paleozoic Geology of the Fox River from Batavia to Oswego, Illinois Written By: Steven D.J. Baumann, Teresa Arrospide Edited By: Rebecca Chambers Publication Number: G-072007-2A i Table of Contents: Section Page Introduction ………………………………………………….. 1 Stratigraphic Column and Outcrop Exposures ………………………………………………….. 2 Area Geology …………………………………………………. 2 Quaternary ………………………………………………….. 3 Silurian ………………………………………………….. 3 Ordovician ………………………………………………….. 3 Outcrop Locations ………………………………………………….. 3 Quarry Park: Outcrop 1 ………………………………………………….. 4 Flagstone Quarry: Outcrop 2 ………………………………………………….. 5 1106 Woodland: Outcrop 3 ………………………………………………….. 6 Mill Creek: Outcrop 4 ………………………………………………….. 7 Grant Street: Outcrop 5 ………………………………………………….. 8 North Aurora Quarry Section: Outcrop 6 ………………………………………………….. 9 Waubonsie Creek: Outcrop 7 ………………………………………………….. 10 Hydrology ………………………………………………….. 11 Structural Geology ………………………………………………….. 12 Regional Geology ………………………………………………….. 12 Aurora Syncline ………………………………………………….. 12 Batavia Syncline (new) ………………………………………………….. 12 Fox Valley Anticline (new) ………………………………………………….. 12 Gustafson Anticline (new) ………………………………………………….. 13 Nelson Syncline (new) ………………………………………………….. 13 Red Oaks Syncline (new) ………………………………………………….. 13 River Hills Monocline (new) ………………………………………………….. 13 ii Table of Contents: Section Page Schneider Monocline (new) ………………………………………………….. 13 Structural History of Batavia Synclinorium ………………………………………………….. 14 Late Precambrian Super-eon …………………………………………………. 14 Cambrian Period ………………………………………………….. 14 Early Ordovician Period ………………………………………………….. 14 Middle Ordovician Period ………………………………………………….. 14 Late Ordovician Period ………………………………………………….. 14 Early Silurian Period ………………………………………………….. 15 Late Silurian Period ………………………………………………….. 15 Devonian to Permian Periods ………………………………………………….. 15 Mesozoic Era ………………………………………………….. 15 Tertiary Period ………………………………………………….. 15 Quaternary Period ………………………………………………….. 15 Fossil Information ………………………………………………….. 16 Map Notes (Attachment A and B) ………………………………………………….. 17 Well Log Notes (Attachment C and D) ………………………………………………….. 17 Conclusions and Lessons ………………………………………………….. 17 Glossary ………………………………………………….. 18 References ………………………………………………….. 20 Credits ………………………………………………….. 20 iii Introduction: This guidebook takes you through the Paleozoic bedrock geology from the southern tip of Batavia down thru Oswego Illinois, along the Fox River. Glacial deposits are abundant at the surface but are not the focus of this guidebook. The bedrock exposed is all Silurian in age except at the last stop in Oswego where it is upper Ordovician in Age. There are a total of seven outcrops and one core that were looked at along the way. Most are easily accessible. However, a couple of the outcrops are difficult to get to. Almost all of the Silurian rocks are exposed along the river. Only the upper most Si- lurian formation (Racine) and most of the underlying formation (Sugar Run) are absent and they will not be described here. The Silurian formations that are present (youngest to oldest) are the Joliet, Kankakee, Elwood, and the Wilhelmi. All the individ- ual members are present except for the Offerman Member of the Kankakee Formation. It appears never to have been deposited or is inseparable from the above Troutman Member (which is unusually thick). The Ordovician-Silurian Contact is exposed in Oswego. The Ordovician rocks that are exposed are from the upper half of the Maquoketa Group. The youngest Ordovi- cian formation in northeastern Illinois is the Neda, which was eroded in the local re- gion before the Silurian was deposited. The other Upper Ordovician formations are present. From youngest to oldest they are the Brainard, Fort Atkinson, and the Scales. Upon the initial completion of the field work for this guidebook, a couple of new geo- logic structures were identified in the area north of the well documented Aurora Syn- cline (the major structure in the area). Several small folds were discovered along a minor unconformity that exists within the Silurian rocks. Well data seems to support their existence. A couple of these structures do appear in ISGS publications but were never named. First you will be presented with a stratigraphic column, in order to know what rocks to look for. Then You will be taken on a visit to each of the seven sites. After that a geological history of the area will be present with an explanation of the newly discov- ered structures and the Paleozoic history of the area. 1 2 Figure 1: Stratigraphic Column and Outcrop Exposures Outcrop and Exposed Section System System Group or Series Formation Member or facies Lithology Description Henry, Diamicton (Loams with Cobbles), Outwash (sand and gravels), Lake Deposits (Sands, Silts, and Lemont, Clays) Equality Quat. Mason, Wedron White to very light gray occasionally mottled pink, medium to coarse crystalline, pure, vescular to Romeo vuggy, medium bedded DOLOSTONE. Fossils: Dark gray worm burrows Mill Creek Outcrop #4 Quarry Park Outcrop #1 Flagstone Quarry Very light yellowish gray to very light gray, graded upwards from micritic to fine crystalline, smooth Outcrop #2 bedded, SILTY DOLOSTONE, large vugs common within upper 6 inches. Will often form tuffa on long exposed outcrop faces. Fossils: None Joliet Joliet Markgraf Markgraf 1106 Woodland Outcrop #3 Nigaran Ser.Nigaran Very light gray to light greenish gray, micritic to fine crystalline, wavy bedded, ARGILLACEOUS DOLOSTONE. Separated by green clay beds 0.5” to 3” along bedding planes in upper half. Lower part is a dark red blotched deep yellow, medium laminated, DOLOMITIC SHALE, with thin argilla- ceous beds of yellow dolostones. Surface exposures will often have a dark green inorganic coating. Bridge Bridge Fossils: None Brandon Brandon Grant Street Outcrop #5 Plaines Very light gray to light yellowish gray, medium to coarse crystalline, pure DOLOSTONE, with a pitted surface at top often filled with white clay. Fossils: None Very light pinkish gray mottled orange, vesicular, fine to medium crystalline, pure DOLOSTONE, in 2” to 4” wavy beds separated by light green clay partings, with isolated white chert lenses. A Hurd’s Island prominent 1” to 2” very pale yellow to white clay bed appears in the upper 1/2 of the member. Core# AU-2102 Silurian Troutman Troutman Fossils: Corals Kankakee North Aurora Quarry Section Outcrop #6 Very light gray mottled pink, vesicular to vuggy, fine to medium crystalline, thick bedded to Drummond massive, pure DOLOSTONE. A prominent green clay parting is occasionally present at the bottom. Occasionally contains trace glauconite and sand grains in the bottom 1/2. Fossils: None Very light gray to yellowish gray, very fine to medium crystalline, thick bedded to massive, vesicular, moderately pure DOLOSTONE to LIMESTONE (occasionally silty), with green clay partings. Alexandrian Ser. Elwood Contains as much as 50% white chert throughout existing as nodules as much as 4” thick. Amount of chert decreases from 50% to almost 0% within the Aurora Syncline. Occasionally an orange Waubonsie Creek corrosive surface exists at the very top. Fossils: None Outcrop #7 Very light gray to yellowish gray, thick bedded to massive with tight smooth bedding planes, fine to medium crystalline, pure DOLOSTONE to LIMESTONE. Contains isolated 1’ to 2’ wide by 1” to 2” thick lenses of color Birds banded chert. This member is pure than usual from Batavia to Oswego. Fossils: None Light gray to yellowish gray with occasional black speckling, very fine to medium crystalline, ARGILLACEOUS to Schweizer SILTY DOLOSTONE and LIMESTONE, thin to thick bedded. Interbedded with thin to thick beds of laminated gray Wilhelmi DOLOMITIC SHALE, with occasional green clay partings throughout. Fossils: None Shale f. Light greenish gray to green (occasionally pinkish purple), thinly laminated, very soft, SHALE (occasionally dolomitic and silty). Fossils: crinoid stems, trilobite and brachiopod fragments) Dolostone Very light gray to pale purplish gray, thin to thick very unevenly bedded, fine to medium crystal- line, pure DOLOSTONE, with randomly oriented green clay filled burrows several inches long. Brainard & Shale f. Pure beds separated by thickly laminated to thin beds of green thinly laminated soft DOLOMITIC SHALE. Fossils: Tentaculites oswegoensis, crinoid stems, fragments of Ambonychia and/or Stophomena, Glyptorthis and Hyspipfycha pieces, trilobite fragments Light gray mottled white, pink, and black, smooth medium to thick beds, medium to coarse Fort crystalline, vesicular to vuggy, pure, DOLOSTONE to LIMESTONE, often with large crystals giving LEGEND Atkinson the rock a “granitic” appearance. The base contains thin beds of green and brown laminated SHALE Fossils: Debris is present at the base. Unconformity Exposed Subsurface Gray to brown to black, medium laminated DOLOMITIC to CALCAREOUS SHALE. Usually weak only and breaks easily. May contain some pyrite along bedding planes. Fossils: None Ordovician Ordovician Section Missing Maquoketa Gp. Elgin = Quaternary Quat. Fossil Scales Chert Glauconite Dolostone or Sand and Light olive gray to brownish black with dark gray speckling, thick, vesicular to vuggy, wavy beds, fine Limestone Gravel to coarse crystalline DOLOSTONE TO LIMESTONE, with dark gray shale partings. Fossils: Occasionally very fossilifeous but fossils have not been described in detail. Uneven Silt and Dolostone