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 geologic 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 discovered structures and the Paleozoic history of the area.

1 2 Ordovician Silurian Quat. System Mason, Maquoketa Gp. Alexandrian Ser. Nigaran Ser. Wedron Group or Series Atkinson

Scales Lemont,

Brainard Wilhelmi Joliet Equality

Elwood Kankakee Henry, Formation Fort Drummond Dolostone & Shale f. f. & Shale Schweizer Shale f. Romeo Shale f. f. Shale Birds Birds Elgin Elgin Dolostone f. Plaines Brandon Troutman Bridge Markgraf Member or facies Lithology Description Description Lithology

silty). Light greenish gray to green (occasionally pinkish purple), thinly laminated, very soft, SHALE (occasionally dolomitic and corrosive surface exists at the very top. of chertdecreases within from 50% toalmost 0% theSyncline. Aurora Occasionally orange an much whiteContains as as50% chertthroughout existingthick. nodules as4” asas much Amount moderately pure DOLOSTONE toLIMESTONE (occasionally silty), clay partings. withgreen lightVery graytoyellowishgray,to veryfine medium crystalline, thick to massive, bedded vesicular, Fossils beds ofyellowceous dolostones. exposures Surface dark a will ofteninorganic green have coating. part isa dark red blotched deep yellow, medium laminated, DOLOMITIC SHALE, with thinargilla- DOLOSTONE. Separated by green clay beds 0.5” to ARGILLACEOUS bedded, wavy crystalline, fine to micritic gray, greenish light to gray light Very vuggy, medium bedded DOLOSTONE. Whiteto verylight grayoccasionally mottled pink,to medium coarse crystalline, pure, vescular to Clays) Diamicton (Loams with Cobbles), Outwash (sand Fossils Gray to brown, medium laminated, softSHALE. exposedlong outcropfaces. bedded,SILTY DOLOSTONE, common vugs large within inches. upper 6 Will often form tuffa on smooth crystalline, fine to micritic from upwards graded gray, light very to gray yellowish light Very Fossils prominentvery 1”to2” yellow pale to whiteclay bedappears the upper in of1/2 the member. separatedwavy beds to bylight 4” 2” clay green partings, isolated with chert white lenses. A lightVery gray pinkish mottled orange, vesicular, crystalline, tomedium fine pureDOLOSTONE, in and breaksand easily. May contain some pyrite along bedding planes. Gray tobrown black, medium laminated DOLOMITIC SHALE. toCALCAREOUS Usuallyweak Fossils “granitic”the rocka appearance. contains base The thin of greenbrown beds and laminatedSHALE giving crystals large with often LIMESTONE, to DOLOSTONE pure, vuggy, to vesicular crystalline, coarse to medium beds, thick to medium smooth black, and pink, white, mottled gray Light Occasionally veryfossilifeous butfossilsnotbeen described have indetail. to coarsecrystalline DOLOSTONE TOLIMESTONE, withdark grayshale partings. oliveLight grayto brownish black withgray dark sp pitted surface at top often filled with white clay. clay. white with filled often top at surface pitted lightVery graytolight yellowish gray, medium to coarsecrystalline,DOLOSTONE,pure with a DOLOMITIC SHALE, with occasionalgreen clay partings throughout. SILTY DOLOSTONE and LIMESTONE, thin to thick bedded. Interbedded with thin to thick beds of laminated gray to crystalline, ARGILLACEOUS tomedium fine very speckling, black with occasional gray yellowish to gray Light SHALE. beds separatedPure thickly by laminatedbeds tothin thinly ofgreen laminated soft DOLOMITIC line, pure DOLOSTONE,with randomly orientedgreen clayfilled burrows several inches long. lightVery graytopale purplish gray, thin tothick very bedded,unevenly fine tomedium crystal- banded chert.This member is pure than usualfrom Batavia to Oswego. crystalline, pure DOLOSTONEtoLIMESTONE. Contains isolated1’ to2’ wide by 1”to2” thick lenses of color Verylight gray toyellowish gray, thickbedded tomassive withtight smooth bedding planes, fine to medium Stophomena, Glyptorthis Hyspipfycha and pieces, trilobite fragments Fossils Fossils bottom. Occasionally contains trace glauconite andsand grains the bottom in 1/2. massive,pure DOLOSTONE. prominent A green clay parting is occasionally present atthe to bedded thick crystalline, medium to fine vuggy, to vesicular pink, mottled gray light Very : None : None : Corals : Corals : Debris ispresent atthe base. : crinoid stems, trilobite and brachiopod fragments) : None Fossils : Tentaculites oswegoensis, crinoid st Fossils : None Fossils Fossils Figure 1: Figure : Dark gray worm burrows burrows worm gray Dark : : None : None Maycontain somepyritealong beddingplanes. and gravels),Lake Deposits (Sands,Silts, and Fossils eckling, thick, vesicular to vuggy, wavybeds, vuggy, to thick, fine vesicular eckling, 3”along bedding planes inhalf. upper Lower and OutcropExposures ems, fragments ofAmbonychia and/or : None Fossils Fossils Fossils : None : None : None

Stratigraphic Column : None : None Fossils : Outcrop #4 Mill Creek Core# AU-2102 AU-2102 Core# Island Hurd’s Outcrop and Exposed Section Section Exposed and Outcrop Outcrop #2 Quarry Flagstone Outcrop #3 1106 Woodland Outcrop #6 Section Quarry Aurora North

Quat. Missing Section Exposed Subsurface Chert Chert = Quaternary = Quaternary Outcrop #5 Street Grant Outcrop #7 Waubonsie Creek clay Shale or Limestone or Dolostone Uneven Limestone or Dolostone Unconformity Unconformity LEGEND LEGEND Outcrop #1 Quarry Park only Glauconite Fossil sand sand Silt and Gravel Sand and Diamicton Area Geology:

There are three geologic time spans present in the area. All of which are separated by unconformities. The Quaternary deposits are the youngest. Below them lay the much older Silurian rocks. Below the Silurian are the Ordovician deposits.

Quaternary: These deposits consist of glacial diamicton, outwash deposits, and lake deposits. They are represented by the Equality and Henry Formations of the Mason Group and the Lemont Formation of the Wedron Group. All of which have complicated inter-tonguing relationships. They have been well studied in the area and will not be the focus of this guidebook. The ISGS does have many great publications available on the glacial history of the area.

Silurian: The upper most Paleozoic rocks represented are the Silurian. There are two main series of rocks be- longing to this System in Northeastern Illinois, and both are present in the area. You have the bottom of the Niagaran Series, which consists mainly of dolostones of varying purities. None of the formations that contain the massive reefs are still present in the area. The Niagaran Series that are present represent the rocks deposited before the reefs. The reef producing Racine Formation has been entirely eroded in the area. The underlying Alexandrian Series also consists mostly of dolostones with a shaley base. These rocks tend to be impure overall. They were deposited on top of and erosional surface that formed at the end of the Ordovician.

Ordovician: The lower Paleozoic rocks exposed in the area are from the middle of the Upper Ordovician (or Ma- quoketa Group) rocks. They consist mostly of shales interbedded with dolostones and limestones. Unlike the overlying Silurian their internal relationships are complex with many facies changes. Also the youngest two formations, the Neda and the Brainard, are either been partially or totally eroded in the area due to an erosional unconformity at the top.

These rocks also tend to be the most fossil producing units in the area. One strange fossil unique to the Brainard Formation is present at Waubonsie Creek and is named for Oswego Illinois. It is Tentaculites oswegoensis or T. oswego for short.

Outcrop Locations:

There are seven outcrops that can be visited along the way. Some are either on or close to private property. Most are on public land and are relatively easy to access, if you don’t mind minor amounts of hiking thru the woods.

3 Quarry Park; Outcrop 1: Approximate GPS: N: 41.8428 W: 88.3101

Quarry Park is a public water park in an old quarry. It is also known as Fredrick Beach Park. It is located in the southern Part of Batavia on the west side of the river. The exit is on the east side of IL-31 at Union Avenue. Once you turn east onto Union, you follow it all the way around. You will see the water park on the right side. Behind the park you will see the steep cliffs. The bottom half of the cliffs are the Markgraf Member of the Joliet Formation. This rock is what was quarried. The best exposures are behind the visitor center on the southwest side of the park.

You will also notice the rock is covered with a spongy looking but hard substance. This is known as tufa. It is a calcareous deposit that precipitates out of the rock thru moving water. The Markgraf and the missing Sugar Run are the only two units that show extended covering of tufa. The Markgraf and the Sugar Run are both very similar units and can be difficult to differentiate without stratigraphic con- trol.

Above the solid bedrock lies the more recent glacial deposits. The Markgraf has a known thickness of 23 feet in the area which is about the thickness of the outcrop. It is possible that the Romeo exists just under the glacial deposits.

Figure 2: Quarry Park Visitor Center looking west

4 Flagstone Quarry; Outcrop 2: Approximate GPS: N: 41.8436 W: 88.3046

Flagstone Quarry is almost due east of Quarry Park, on the opposite side of the Fox River. It is along the eastside of State Route 25 behind a strip of industrial buildings and is visible from the road.

Since it is due east of Quarry Park we should observe the same rock types that are present at Quarry Park and we do. The Markgraf Member is presently being quarried at intermediate intervals. Here you will see the tufa and the typical lithology of the Markgraf. However, this quarry is slightly lower in elevation than Quarry Park. The floor of the quarry is actually in the much less pure Brandon Bridge Mem- ber of the Joliet Formation. The Brandon Bridge has so many impurities that it isn’t economically worth much. It is the most varied of all the Silurian units in the area. It is also the most distinctive unit. Since it is located on private property it is advised that you don’t just walk up to the outcrop. There are no fences to close it off.

Figure 3: Flagstone Quarry Both images are looking east

5 1106 Woodland; Outcrop 3: Approximate GPS: N: 41.8342 W: 88.3143

This outcrop is named for the address just northwest of the small drainage-way where it is located. It is located in the very southern part of Batavia. To get to it you turn east on Oak Street then right at the T- intersection onto Woodland. It is located about 900 feet south just south of 1106, which is on the eastside of Woodland. You can park along the street and head east into the drainage-way. This is not private property. However, in the summer it is extremely overgrown and difficult to access.

Here we should expect to see the base of the Markgraf according to our elevation. We don’t (the reason will be addressed later). We see the underlying Brandon Bridge Member of the Joliet Formation. As you head down the drainage-way and look at the continuous exposure you will notice a deep red shaley unit. This is near the base of the Brandon Bridge. If you walk further, you will see an outcrop on the northside of the ditch near the back of the yard of 1106. Exposed in this outcrop is the contact with the underlying Alexandrian Series. At this location a small unconformity called a diastem exists. This diastem is present throughout all of Northeastern Illinois. Below the diastem is the entire Planes Member and the upper part of the Troutman Member of the Kankakee Formation.

Figure 5: 1106 Woodland looking northwest at the diastem unconformity

Interbeded yellow argillaceous, micritic, dolostone Nigran Series Joliet Formation Brandon Bridge Member

Red dolomitic shale

Diastem Unconformity

Interbeded yellow argillaceous, Ale xandr micritic, dolostone Kan ian Se kakee ries Form Pla ation nes Me mbe Al r exand Ka rian S nkake eries T e For routm matio an Me n mber Red dolomitic shale

Figure 4: 1106 Woodland looking west at the red shale beds in the Brandon Bridge Member

6 Mill Creek; Outcrop 4: Approximate GPS: N: 41.8222 W: 88.3254

The Mill Creek outcrop is located on the south side of Mill Creek extending under and west of State Route 31 for about 300 feet. The only way to really get to this outcrop is to either descend the overpass or to park at Les Arends Forest Preserve on the east side of Route 31. Once you enter the forest preserve you follow the curve and head south. Park as far south as you can. Just to the east is a bike path. Take that south to you see a bridge with a steel frame. The bridge is over Mill Creek. Once you get to the bridge you descend down to the creek and turn right. You will see the outcrop on the opposite side of the river.

If we assumed a regional dip of east-northeast we should expect the Brandon Bridge to be at this elevation. We don’t. Instead the Markgraf is exposed from the creek up the cliff and is capped by about 3 feet of the base of the Romeo Member. Now in order to really observe this outcrop you are going to have to ford the creek. When you look at it you will notice the cavern formations in the base of the outcrop to the west. Mill Creek served as a catastrophic outwash river emptying into the Fox when the glaciers melted. The process was very similar to what happened at Rock Creek in Kankakee River State Park (KRSP). In fact many of the same rock units and surface features present in the Fox River area are present at KRSP.

Figure 7: Mill Creek Looking west from State Route 31

ion at r Figure 6: Mill Creek rm be Fo em iet M Looking southwest from State Route 31 Jol raf rkg Ma

Mill Creek

Joliet Formation Markgraf Member

Caverns

Joliet Formation Markgraf Member

Mill Creek

Figure 8: Mill Creek Looking west from under State Route 31

7 Grant Street; Outcrop 5: Approximate GPS: N: 41.804357 W: 88.3216

This outcrop is a small, tiny exposure only 2 to 5 feet thick. This is a tricky one to get to. Come at it from the north. Take State Route 25 south to State Route 56. Follow the curve. IL-56 banks right (west). Don’t follow the curve over the river. At the curve there is a side street that continues south. It doesn’t look like you can go straight but you can. This is Grant Street. Eastbound IL-56 traffic does not stop so be careful.

Once you cross and head south you will notice small discontinuous outcrops to your left (east side of the road). This is the upper part Troutman Member of the Kankakee Formation. We are near the top of the Troutman here and it is possible that the base of the overlying Planes Member is here but the rock is so weathered it can’t be differentiated from the Troutman. Once again the section appears out of place. At this elevation the Brandon Bridge is what we should expect to find.

If you want to get a close look, you need to park in the empty lot at the south end of Grant Street and walk north to the outcrops along the east side of the road.

Figure 9: Grant Street Outcrop Looking East

Kankakee Formation Troutman Member

8 North Aurora Quarry Section; Outcrop 6: Approximate GPS: N: 41.7981 W: 88.3166

This is an active quarry and visitors are no longer allowed inside. However, you can get a look into the quarry from the right-of-way on the eastside of State Route 25 about 600 feet north of the I-88 overpass. There is plenty of room to park on the shoulder.

This section was described in detail by Willman in the 1973 Illinois State Geological Survey (ISGS) Cir- cular 479, which is still in print. However, when he described it the quarry was only dug out 3/4 of its present depth. If you look north from the berm you see the bottom of the Kankakee Formation, the Drummond Member at the top of the cliff. Below that is almost entirely the cherty Elwood Formation. The Quarry floor is actually on top of the Ordovician. They have tunneled thru the upper Ordovician down to the rocks of the middle Ordovician and are mining the stone about 100 feet underground.

The rocks exposed here are about at the elevations that we would expect if they were dipping strictly east. Just south of here is the five mile wide Aurora Syncline, the dominant structure in the area. Un- fortunately there are no outcrops exposed in the syncline. The Aurora Syncline is described in detail in the 1991 ISGS publication Circular 547.

Figure 10: North Aurora Quarry

Quarry

Figure 11: North Aurora Quarry with topographic Relief

rry Qua

9 Waubonsie Creek; Outcrop 7: Approximate GPS: N: 41.6854 W: 88.3515

Waubonsie Creek is the next surface outcrop. It is about six miles south of Outcrop 6. Take State Route 25 south thru Aurora into Oswego. Just north of the junction of State Route 25 and U.S. Route 34 there is a street to your right (west) called North Street. Make a right and follow the curve left (south) until you see the outcrop to your left about 500 feet passed the curve. You will notice parking spaces to your left. Parking is free. The outcrop will be on the east side of Adams after you cross the railroad tracks. Be careful, the tracks are in use.

This outcrop extends along the south side of the creek for about a distance of 450 feet. It ends east at an old surface quarry that hasn’t been mined in decades. It is now part of the park district. Here the Or- dovician-Silurian contact is well exposed. The rocks at creek level are from the basal dolostone and shale facies of the Brainard Formation. This unit is loaded with fossils including the strictly local Ten- taculites oswegoensis, which is an animal of uncertain origin. The Ordovician-Silurian Contact here is an erosional unconformity. As you head from west to east the top of the Ordovician strata decreases in elevation indicating that the outcrop was once a paleo-hill. In one gully approximately at the halfway point of the outcrop the very top of the shale at the contact has weathered yellow, indicating exposure to the surface. The eastern most part of the outcrop is an old quarry. The bottom is at the top of the Ordovician. Above that is about 3 feet of the Birds Member of the Wilhelmi Formation (the Schweizer Member was never deposited). Above the Birds is about fifteen feet of the Elwood Formation. Chert is present but is in medium beds that pinch in and out. It only constitutes about 5% of the total rock. It is common for the Elwood to lack its characteristic chert in the area of the Aurora Syncline.

Figure 12: Halfway outcrop looking south

Erosional Unconformities Quaternary Silurian

Figure 13: Waubonsie Creek looking east

Ordovician

10 Hydrology:

The Quaternary deposits hold water and are a potential economical source, especially the sands and gravels of the Henry Formation. It is not advised to set wells in the shallow unconsolidated Quater- nary due to the high potential for contamination. Mainly from sewage and gas stations. The Quater- nary units form the Prairie Aquigroup.

Wells should also not be set within any Silurian unit that is younger than the Markgraf Member of the Joliet Formation. The reason being is that the Markgraf being fine grained, dense and containing a lot of free carbonates, tends only to hold water in joints and cracks. The water is generally drinkable but low quality. It forms a confining unit or aquitard. Wells put into the Markgraf will produce for only a short time. However, since it does form a confining unit, it acts as a barrier to surface contaminants. Wells set in other Silurian strata tend to produce and are good for small private wells in area from Batavia to Oswego. The Niagaran and Alexandrian Series are part of the Silurian Dolomite Aquifer of the Upper Bedrock Aquifer.

The formations in the Maquoketa Group of the Ordovician should be avoided for the purpose of water extraction. They form a regional, thick confining unit throughout the state. Wells set in the Maquoketa historically do not produce. Although the Fort Atkinson Formation has been known to yield small quan- tities of water. However, once that water is removed, it is not replenished. The Maquoketa forms the Maquoketa Confining Unit of the Midwest Bedrock Aquigroup.

The underlying Galena and Platteville Groups are a reliable source of well water. However, in the area, they tend to be at least a few hundred feet below the surface and historically only yield slightly more water than the Silurian. The Galena Platteville forms the Galena-Platteville Unit (serves as both an aquifer and aquitard) of the Midwest Bedrock Aquigroup.

A complete publication on the water units in northern Illinois is the ISGS publication is the “Cooperative Groundwater Report #10”. It is available in print, or free for download on the ISGS website.

11 Structural Geology:

Regional Dip: Overall, the rocks have a regional dip of almost due east, slightly northeast along the north area of the map and northeast in Oswego all dipping towards the Michigan Basin. Regional dip is so subtle (10 to 15 feet per mile or 0.1o to 0.2o) that it isn’t really reflected in local structures such as the Aurora Syn- cline.

Aurora Syncline: The Aurora Syncline is the dominant structure in the area and trends east-wet and is in between Stops 6 and 7. It is approximately 2 to 6 miles wide and is about 12 to 15 miles long with about 100 feet of maximum relief. The Aurora Syncline is not a structure visible at the surface. It exists only within the bedrock. The surficial glacial material is unaffected by it. There are no outcrops along the Fox River in the Aurora Syncline. Some of the formations within the syncline tend to be different then typically de- fined. The Elwood Formation has far less chert and in some places no chert. Limestone dominates over dolostones (especially in the Galena Group), the Fort Atkinson thins, but the rest of the Maquoketa Group thickens slightly. Details on the Aurora Syncline are available in the ISGS publication, Circular 547.

Batavia Synclinorium (new): However, while compiling the data for this trip along the Fox River, several interesting structures began to come to light. Originally a bedrock geology map was going to be created. While beginning to create one it was noticed that some members and formations were “higher or lower” than they should have been. There are no major faults in the area so we consulted some well logs. They confirmed our suspicions. There must be subtle structures along the Fox River related to the Aurora Syncline (See Structural Map for details). These subtle structures are reflected at least down to the Galena. However, due to erosional unconformities on top of the Galena, Maquoketa, and Silurian, we decided to use the diastem unconformity within the Silurian to generate our structure map since it was probably deposited on a flat surface. The newly documented structures are generally more subtle than the Aurora Syncline and are located north of it. It was decided to refer to all the structures that are associated with the Aurora Syncline should be collectively referred to as the “Batavia Synclinorium”, since synclines dominate and would be named after the town of Batavia Illinois. The structures consist of several synclines, anticlines, and significant monoclines in between the synclines and anticlines.

Since the Aurora Syncline has been described in detail in other publications it will not be described here. The focus here will be the lesser folds along the Aurora Syncline’s northern flank.

Fox Valley Anticline (new): The Fox Valley Anticline is a flat structure with relatively deep descending flanks. It’s axis is not in the map area but is close to the south edge of the structure and is off center. The northern flank descends into the Red Oak Syncline and the southern flank descends into the Aurora Syncline. It has a total relief of 10 to 15 feet and trends roughly south-southeast possibly for most of the length of the Aurora Syncline. The Fox Valley Anticline shows up in the 1991 cross section of ISGS publication Circular 547 p.20. it is named for the Fox Valley Country Club in T39N, R08E, section 34, NW quarter.

12 Gustafson Anticline (new): The Gustafson Anticline is a “squeeze” structure sandwiched between the Red Oaks Syncline to the south and the Nelson Syncline to the north. It trends southeast and as about 15 feet of relief. It actually disappears in T39N R08E section 35 near where the above mentioned synclines merge. Its exact axial length is not known but it is probably only 1 mile or 2 in length. Along its northwestern side it seems to level out and follow regional dip (visible on the structural map). It is named after Gustafson School located in T39N, R08E, section 27, NE quarter in Batavia.

Nelson Syncline (new): The Nelson Syncline is the northern most observed structure. It has a maximum relief of about 20 feet. It begins in section 22 of T39N, R08E and trends south east. It merges with the Red Oak Syncline near the border of T39N, R08E and T39N R09E where the Red Oak Syncline dominates. Its total length is about 2.5 miles. It is named after Nelson School located in T39N, R08E section 23, SW quarter, in Bata- via.

Red Oak Syncline (new): The Red Oak Syncline is in between the Gustafson and Fox Valley Anticlines. It appears to be the sec- ond major structure after the Aurora Syncline. It dips east-southeast and has a local maximum relief of 35 to 40 feet but maybe as much as 50 to 60 feet of relief east of the map area. It also appears in the 1991 cross section of ISGS publication Circular 547 p.20. It also appears on isopac maps and cross sections of the Maquoketa, Galena-Platteville, and Ancell Groups but not on any Cambrian or Precambrian maps. It seems to run parallel to the Aurora Syncline and may be almost as long. It is estimated to be about 10 to 15 miles in length beginning near T39N, R08E, section 30. It is named after Red Oak Park on the east side of the Fox River located in T39N, R08E, sections 27SW quarter to 34, NW quarter, between Batavia and Aurora.

River Hills Monocline (new): The River Hills Monocline is at the southeastern flank of the Gustafson Anticline along its axis and ends where the Nelson and Red Oak Synclines meet. It is named after River Hills Cemetery located in T39N, R08E, section 27, SE quarter between North Aurora and Batavia.

Schneider Monocline (new): The Schneider Monocline is the north descending flank between the Fox Valley Anticline and the Red Oak Syncline and is perpendicular to their axis. It is named after Schneider School located in T39N, R08E, section 34, SW quarter in North Aurora.

13 Structural History of the Batavia Synclinorium:

The local structures that are present formed over millions of years. Even though they are not as grand as many structures in other areas they owe their existence to very slow subsiding events related to things happening thousands of miles away. We know this because of what makes up the geologic record. This not only includes the rocks themselves, but also the fossils they contain. Equally as important is not only what is preserved but what is missing.

Late Precambrian Super-eon (680-570 million years ago): Not much is known from this time span since most of the rocks older than Cambrian have either been eroded or deeply buried. What we do know is that during this time the Illinois Basin began to sub- side. This allowed the seas to flood the land and set the stage for future structural development. At this time the long exposed Precambrian granite and rhyolite hills began to be reduced to near sea level. It is possible that the very base of sedimentary rocks in Illinois were laid down during this time.

Cambrian Period (570-505 million years ago): During this time erosion continued until the Late Cambrian when the Sauk Seas began to encroach on Illinois and the deposition of sands began. No local structures were developing at this time.

Early Ordovician Period (505-478 million years ago): The Sauk Seas which deposited thick amounts of sand over Illinois began to retreat and erosion resumed. As erosion began to remove the some of the sands and form hills. These ancient hills (also called paleo-hills) would form the base of future structures. Near the end of this time a new set of seas returned called the Tippecanoe I Seas.

Middle Ordovician Period (478-458 million years ago): The seas began their advance only retreating for very short periods. Illinois has massive deposits from this relatively narrow span of time. The Ancell, Galena, and Platteville Groups were deposited during this time. Over 1300 feet of sediments in some places. This is when many of the present structures begin to take shape. This is when the Aurora Syncline, Fox Valley Anticline, and Red Oak Syncline all begin to take shape. There are a couple of reasons why these structures began to form. On a local scale the paleo-hills on which the aforementioned sediments were deposited influenced highs and lows in topography. Something much further away was the cause of the subsidence in the Illinois Basin, allow- ing the seas to invade. Tectonic collisions to the east began to form the Appalachian Mountains as North America and Europe began to collide in an event called the Taconic Orogeny. Volcanoes formed to the east spewing ash that would be preserved in the local rock record in Illinois.

Late Ordovician Period (458-438 million years ago): By this time the Appalachians were still being built, but at a slower pace and all of the local structures (except for the Nelson Syncline) were being shaped. Something new would happen. At the end of this period of time the seas retreated (ending the Tippecanoe I), erosion resumed. Not because of tectonic forces but because of a global drop in sea level due to an ice age in the southern hemisphere. The ice age seems to have only lasted 5 million years but it was extensive. Illinois did not get glaciated this time around because we were just south of the equator. This period of erosion would set the stage for the development of the Nelson Syncline which seems to be controlled strictly by paleo-topography as where the other structures seem to be more controlled by tectonic forces.

14 Early Silurian Period (438-421 million years ago): After the ice retreated, the Tippecanoe II Seas advanced with a vengeance. Subsidence continued but now the depositional setting changed. This is when massive carbonates began to be deposited as ocean currents changed due to the collision between North America and Europe. All local structures con- tinue to form until the end of this time span when all sedimentation briefly stopped forming the diastem at the top of the Alexandrian Series. The building of the Appalachian Mountains is complete.

Late Silurian Period (421-408 million years ago): This time the continents begin to shift again and local subsidence slowed. As a result, deposition resumed. It is during this time that the massive coral reefs of the Niagaran Series at Thornton, Stony Is- land, and many other locations were deposited in an environment identical to the modern Great Bar- rier Reef. Deposits 400 feet thick and greater formed in a matter of 10 million years. The reefs served as a barrier. This created evaporite deposits to the east as Illinois moved north towards the equator.

Devonian (408 million years ago) to the Permian Period (245 million years ago): On the scale of the Fox River Valley much isn’t known about this span of time. We do know that the Tippecanoe II Seas retreated at the end of the Devonian (360 million years ago) and the Kaskaskian Seas moved in. However, once the Kaskaskian Seas retreated (during the Permian) a long extended period of erosion began as the local area stopped subsiding and all local structures took on their modern shapes. The area stopped subsiding because of the formation of the supercontinent called Pangaea. We do know that the water did cover the area at times. We see Devonian and Pennsylvanian sediments that have filled some of the cracks and fissures in the underlying Silurian. We do not see any Mississippian or Permian sediments. Once the seas moved out at the end of the Paleozoic, they would not return to the area.

Mesozoic Era (245-65 million years ago): The Fox River area was high and dry, just like today. It was the age of the dinosaurs. The breaking apart of Pangaea had only minor effects on the area. It is possible that the Sandwich Fault Zone (about 25 miles to the south) formed during this period thru the release of continental stress exerted during the initial formation of Pangaea. We do not know for sure when the fault formed since no rocks from this period are preserved in the area. We just know it is younger than Silurian.

Tertiary (65-2 million years ago): The Dinosaurs were gone. No new rocks formed and erosion continued. No local tectonic events. Ac- cording to some estimates, it is possible that during the 250 million years that the area has been dry land. As much as a mile or more thick of the rock record was lost forever to erosion.

Quaternary (2 million years ago to present): During this period the most recent ice age encroached the area and almost covered the entire state at times. The glaciers left sediments as much as 300 feet thick. No new structures formed. The glacial sediments in the area show no deformation caused by tectonic forces. Erosion has resumed.

15 Fossil Information:

Only a few local units produce fossils. The only outcrop visited with any collectable amounts is Stop 7 at Oswego. The Oswego outcrop holds a unique fossil called Tentaculites oswegoensis. Tentaculites is a genus that existed from the early Ordovician to the Late Devonian and was worldwide. Although in Illinois they are only known from the Upper Ordovician. However, a T. oswegoensis like fossil was discovered at the very base of the Silurian in Kankakee, IL, unpublished. The exact classification of this fossil is problematic. No one is sure what it was related to. They are often classified as criconarids or worm-like creatures. They are usually found in a nearly straight position. Most worms ball up or fold in on themselves. It is also possible that T. oswegoensis maybe a snail since the fossil itself seems to be more of hard bodied animal and no known identifiable heads have been found. They also preserve better than worms. It is possible that it is a unique phylum that no longer exists. Figure 14 shows actual specimens from Oswego at Outcrop 7.

Figure 14: Tentaculites oswegoensis (approximately 2X normal size)

Other fossils are present at Outcrop 7, and all come from the lower dolostones facies of the Brainard Formation. Some that have been identified are as follows: Fragments of possible Ambonychia and/or Stophomena (just a couple of feet above the creek). Fragments have been found of of Glyptorthis and Hyspiptycha (a couple of feet below the Ordovician-Silurian contact). Pictures of these fossils can be found in ISGS publication Circular 528, 1983.

Also crinoid debris is abundant in the form of broken stems. No heads have been found to date. Cri- noids are related to today’s sea lilies and are rooted animals, not plants. Today they are not as abundant as they once were but are among the most long lived group of animals. Their origins may extend as far back as the Middle Cambrian, over 540 million years ago. This would make them more success- ful than humans, mammals, dinosaurs, sharks, and all other vertebrates. Preserved mats as much as 200 feet thick have been found in the limestones of Alberta Canada.

16 Map Notes (Attachment A and B):

Attachment A shows the locations of Outcrops 1 thru 6, with contours on the top of the Alexandrian Series in feet above mean sea level. It also has the names of all of the previously mentioned structures. Attachment B shows the location of Outcrop 7 at Waubonsie Creek.

Well Log Notes (Attachments C and D):

There are two detailed well logs included as attachments. The first is less than a quarter of a mile north of Attachment A. It is a full log showing the geological descriptions to its bottom at 2200 feet below the surface.

Attachment D is a partial log actually located in the Aurora Syncline. It is described in detail in ISGS publication Report of Investigation #218 and is out of print. The original description had Silurian mis- labeled as Maquoketa. Although the actual well is much deeper, it is only corrected down thru the Maquoketa in Attachment D.

Conclusions and Lessons:

Geology is an ever evolving science. We build on what others before us have discovered. Either by intention or by accident. As demonstrated in this publication, so much is left to be discovered in your back yard!

The Fox River area is somewhat an unexplored geologic area. The glacial deposits get most of the at- tention and as a consequence the Paleozoic gets neglected. However, it is one of the few areas in Illi- nois where so many different types of sedimentary rocks exist. It is also unique in the fact that all of the structures described are not formed by faults but gentle structures. Understanding these structures is important in not only studying the history of the earth but also in the search for resources in an a world where we keep having to look in never before searched places to satisfy our never ending appe- tite for materials and goods.

17 Glossary:

Alexandrian Series: Rock units deposited during the Early Silurian about 438 to 421 million years ago.

API Well Logs: A database, accessable thru the Illinois State Geological Survey (ISGS) website, that includes the detailed information in driller’s well logs from drilling into the land.

Aurora Syncline: A subtle structure that extends from southeast Kane to Northwest Will County.

Batavia Synclinorium: A series of subtle anticlines, synclines, and folds that exist just north of and include the larger Aurora Syncline bedrock: The solid Paleozoic rock that lies beneath the glacial deposits. bedrock aquifer: Extractable water that exists within bedrock units. chert: Nodules of relatively pure silicon dioxide (SiO2). crinoids: A group of extinct ancient marine animals that resemble modern sea lilies. diastem: An type of unconformity that represents a period of non-deposition of sediments. formation: The basic formal unit of rock. It has specific characteristics that make it traceable horizontally and/or vertically based on composition and lithology. fossils: Any evidence of past life.

Galena-Platteville Unit: A series of aquaifers and aquitards in the Galena and Platteville carbonate rocks of Mid- dle Ordovician age.

Great Barrier Reef: A modern series of coral reefs that exist off the cost of Eastern Australia.

Illinois Basin: A broad depression shaped spoon structure that extends thru Illinois, part of Indiana, and extreme west part of Kentucky.

Maquoketa Confining Unit: An aquitard between the Upper Bedrock and Midwest Bedrock Aquigroups that produces almost no extractable water.

Maquoketa Group: Rock units deposited during the Late Ordovician from about 458 to 438 million years ago.

Michigan Basin: A broad depression shaped bowl structure that essentially covers the entire state of Michigan.

Midwest Auqigroup: A series of aquifers and aquitards that include the Early to Middle Ordovician rocks. micritic: A term used to describe carbonate rocks that consist of microscopic crystals.

Niagaran Series: Rock units deposited during the Late Silurian about 421 to 408 million years ago. non-deposition: A period of time where neither deposition or erosion occurs.

18 Ordovician Period: A system of rock units that were deposited during a period of time from 505 to 438 million years ago.

Ordovician-Silurian Contact: An erosional unconformity at the top of the Ordovician caused by a rapid drop in global sea levels due to glaciation in the southern hemisphere. outcrop: A location where a rock unit is exposed at the surface and is not buried by soil, debris, or human structures.

Paleozoic Era: Collection of periods from 570 to 245 million years ago when macro-animal life was predomi- nantly marine. potable water: Water that is used for direct human consumption.

Prairie Aquigroup: Series of aquifers that are discontinuous throughout the Quaternary deposits.

Quaternary Period: A system of rock units that were deposited during a period of time from 2 million years ago to the present day. It is during this time that the modern ice ages occur.

Sandwich Fault Zone: A series of tightly spaced faults extending from Ogle to Will County.

Silurian Dolomite Aquifer: (see Upper Bedrock Aquifer)

Silurian Period: A system of rock units that were deposited during a period of time from 438 to 408 million years ago. During this time most of the stone presently quarried in the Chicago area was deposited as carbonate reefs. stratigraphic column: A conceptual model of the rock units present in a specified area.

Taconic Orogeny: A mountain building event beginning in the Cambrian and ending in the Ordovician. tectonic forces: Forces caused by the motion of Earth’s plates over the mantle. tufa: A carbonate precipitate formed on the faces of rock exposures thru the action of groundwater. It has a spongy appearance but is very hard and destroys the internal original rock structure. unconformity: A period of time where the rock record is incomplete due to either erosion, tectonics, or a period of non-deposition.

Upper Bedrock Aquifer: In Northeastern Illinois it is equivalent to the Silurian rocks. It refers to the upper most bedrock water bearing units that are recharged directly by groundwater from glacial deposits. The water within the aquifer fills holes and cracks and does not move horizontally very well. This makes it very susceptible to contamination from the surface.

19 References:

API Well Logs, 120890060500, 120893234000, 120893234100, 120893234200, 120893234300, 120893623500

Cambrian and Ordovician Strata of Northeastern Illinois, T.C. Buschbach, 1964, ISGS Report of Investigation 218

Core Log #AU-2102, Hurd’s Island Aurora Illinois, S.D.J. Baumann, 2006, C-122006-1A

Cross Section of the Paleozoic Rocks of Northeastern Illinois, D. G. Mikulic, 1990, ISGS Illinois Minerals 106

Facies Analysis of the Ordovician Maquoketa Group and Adjacent Strata in Kane County Illinois, A.M. Graese, 1991, ISGS ircular 547

The Fossil Book, A Record of Prehistoric Life, P.V. Rich, 1996, ISBN 0-486-29371-8

Geology Underfoot: In Illinois, Raymond Wiggers, 1997, ISBN 0-87842-346-X

Guide to the Geology of the Joliet Area, W.T. Franke, 2003, ISGS Guidebook 2003A

Handbook of Illinois Stratigraphy, H.B. Willman, 1975, ISGS Bulletin 95

Lithostratigraphy and Depositional Environments of the Maquoketa Group in Northern Illinois, A.M. Graese, 1983, ISGS Circular 528

The Platteville and Galena Groups in Northern Illinois, H.B. Willman, 1978, ISGS Circular 502

Rock Stratigraphy of the Silurian System in NE and NW Illinois, H.B. Willman, 1973, ISGS Circular 479

Silurian Geology of the Des Plaines River Valley, NE Illinois, Donald G. Mikulic, 1985, ISGS Guidebook 17

Some Deep Borings in Illinois, J. A. Udden, 1914, ISGS Bulletin 24

Structural Features in Illinois, W. John Nelson, 1995, ISGS Bulletin 100

Summary of the Geology of the Chicago Area, H.B. Wilman, 1971, ISGS Circular 460

Credits:

Edited by: Rebecca Chambers

Field research by: Steven Baumann, Tiffany Mikes, Adam Wolosyzn

Photographed by: Steven Baumann

Written by: Steven Baumann, Teresa Arrospide

0 5 6

Stop 2 Stop 1 A x is N o S f e y N ls n e o c ls n li o G n n S u e yn st 6 a 60 fs c on l A in Ax n 120893234300 e is tic o lin f G e 6 A us 65 n t ti a cl fs in on e

Stop 3

R iv e r 0 H 3 6 650 il ls

M 0 o 4 n 6 oc l 630 in e

Attachment A Structural Contour Map on Top of the Alexandrian Stop 4 62 0 Series of the

Red O ak Fox River Area from Sy nc Ax lin is o e Batavia to Aurora, IL f R ed S O yn ak clin e

61 5

630

620 Legend

e n li c o n o N Topographic Contour Interval = 10 feet M r e id e n h c S 6 1200 feet 6 4 5 0 0

6 5 0

Stop 5 6 10 foot structural contour interval 5 5 6 5 5 5 foot structural contour level

6 60 Fo Stop 3 Outcrop x V all ey An tic Axis of anticline or syncline lin e 66 5 Stop 6 120893234300 Well location and API number Attachment B Fox River Area and Waubonsie Creek Oswego, Illinois

k ree C sie on aub W Stop 7

LEGEND

Contour Interval = 10 feet N

1200 feet

Stop 3 Outcrop location Attachment C: Interpretation of Batavia Well #3

API#: 120890060500 Drilling Info: Publications Well Appears In: Well Name: City of Batavia, Well #3 Date: January 1st, 1941 ISGS Report of Investigation Location: GPS: N: 41.848627 W: 88.308336 Drilled by: J.P. Miller Co. #218, p.74, 1964 Township and Range: T39N R08E Sec. 22 NE SW NE Total Depth: 2200 feet Elevation: 670 feet above mean sea level

System Group, Formation Member Elevation Depth Thickness Series, or (feet) Stage Top Bottom Top Bottom Quaternary

Wedron and NOT LOGGED 670 610 0 60 60 Mason Alexandrian

Silurian Silurian Birds 610 600 60 70 10 Wilhelmi Schweizer 600 575 70 95 25

Brainard basal dolostones facies 575 536 95 134 35 Maquoketa Fort Atkinson ————— 536 500 134 170 36 Scales Elgin 500 460 170 210 40

Wise Lake and ————— 460 230 210 380 170 Galena Dunelith Ordovician Ordovician Guttenberg ————— 230 220 380 390 10 Nachusa ————— 220 175 390 435 45 Grand Detour ————— 175 140 435 470 35 Platteville Mifflin ————— 140 120 470 490 20 Pectonica ————— 120 85 490 525 35 Loughridge 85 37 525 573 48 Glenwood Daysville 37 20 573 590 17 Ancell Tonti 20 -230 590 840 250 Saint Peter Kress -230 -265 840 875 35

Tr e m Eminence ————— -265 -310 875 920 45 p e a le a u an Potosi ————— -310 -410 920 1020 100

Franconia ————— -410 -482 1020 1092 72

Franconian * Mooseheart -482 -510 1092 1120 28 * Marywood -510 -558 1120 1168 48 Ironton

Cambrian Cambrian * Fox Valley -558 -570 1168 1180 12

* Buelter -570 -620 1180 1230 50

Galesville ————— -620 -675 1230 1285 55

Proviso -675 -878 1285 1488 203

Dresbachian Eau Claire Lombard -878 -1040 1488 1650 162

Elmhurst -1040 -1050 1650 1660 10

Charter -1050 -1335 1660 1945 285

Mount Simon Gunn -1335 -1465 1945 2075 130

Lacey -1465 -1590 2075 2200 >125

Bottom of Well = -1590 feet mean sea level / 2200 feet below surface

NOTES: * = type section

Elevation of units is in feet mean sea level.

The Precambrian basement rock was not penetrated during the construction of the well. Attachment D: Interpretation of Aurora Well #16

API#: 120890060400 Drilling Info: Publications Well Appears In: Well Name: City of Aurora, Well #16 Date: January 1st, 1952 ISGS Report of Investigation Location: GPS: N: 41.735456 W: 88.317698 Drilled by: Layne Western Co. #218, p.74, 1964 Township and Range: T38N R08E Sec. 34 Total Depth: 2139 feet Elevation: 655 feet above mean sea level

System Group, Formation Member or Elevation Depth Thickness Series, or facies (feet) Stage Top Bottom Top Bottom

Quaternary Wedron Lemont Yorkville 655 635 0 20 20

Mason Henry ————— 635 575 20 80 60

Elwood ————— 575 570 80 85 5 Alexandrian Maquoketa Silurian

Wilhelmi Birds 570 560 85 95 10

Brainard dolostone / shale facies 560 520 95 135 40 Ordovician Fort Atkinson ————— 520 475 135 180 45

Clermont 475 465 180 190 10

Scales dolostones facies 465 455 190 200 10

shale facies 455 405 200 250 50 Galena-Platteville Galena-Platteville

undivided ————— 405 77 250 578 328

Bottom of Well = -1484 feet mean sea level / 2139 feet below surface

NOTES: Elevation of units is in feet mean sea level.

The Precambrian basement rock was not penetrated during the construction of the well.

The well encounters Middle and Lower Ordovician rocks.

The well ends after penetrating 384 feet of the Mount Simon Formation.