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Upper Illinois River Basin

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Geology of the Upper Illinois River Basin

For a more detailed description of the Basin, see the Environmental Settings Report (WRIR 98-4268)

Bedrock Geology

Bedrock Geology in the upper Illinois River Basin.The entire UIRB is underlain by Precambrian granitic rocks at depths ranging from about 1,000 ft below land surface in the northern part of the basin to about 7,000 ft in the southeastern part. The Precambrian rocks are overlain by sedimentary rocks of the Cambrian System. These sedimentary rocks are predominately sandstone, and include three of the most heavily used aquifers in the study area. Ordovician-aged rocks overlie the Cambrian rocks and are composed predominately of limestone and dolomite, but also include some sandstone and shale. Where present, the Maquoketa Shale confines the Cambrian-Ordovician bedrock aquifer. The uppermost bedrock units of the Kankakee River Basin are predominately Silurian-Devonian dolomite and limestone, and shale (Willman and others, 1975). The uppermost bedrock units of the Iroquois River Basin are predominately Silurian-Devonian dolomite and limestone, and shale, Mississippian siltstone, and Pennsylvanian sandstone. The uppermost bedrock units of the Chicago and Des Plaines River Basins are predominately undifferentiated Silurian-Devonian dolomite and limestone, and Ordovician shale of the Maquoketa Shale Group (Willman and others, 1975; Gray and others, 1987).The uppermost bedrock units of the Illinois River Basin are predominately Pennsylvanian shale of the Carbondale Formation, Ordovician shale of the Maquoketa Shale Group, and Ordovician limestone and dolomite of the Galena-Platteville Formation (Willman and others, 1975).

Physiography and Surficial Geology

Map showing Quaternary geology in the upper Illinois River Basin.Bedrock has been exposed in places along the Illinois, Des Plaines, and Kankakee River valleys by glacial processes such as meltwater floods (Illinois State Geological Survey, 1973). Except for these bedrock exposures in major river valleys, unconsolidated glacial (Quaternary) deposits cover most of the study area. In recent times, glacial deposits and features have been modified by wind and water erosion (Piskin and Bergstrom, 1975). The glacial and erosional processes are the sources of the present-day landforms in the UIRB; these landforms are the basis for the following physiographic definitions.

Map showing physiography in the upper Illinois River Basin.The UIRB lies in the Central Lowlands physiographic province and is divided into two physiographic sections: the Great Lake Section and the Till Plains Section (Fenneman, 1938). Leighton and others (1948) divided the Illinois part of these sections into two subsections each. In the Illinois part of the UIRB, the Great Lake Section was divided into the Chicago Lake Plain and the Wheaton Morainal Plain, whereas the Till Plains Section was divided into the Kankakee Till Plain and the Bloomington Ridged Plain. For the Indiana part of the UIRB, Schneider (1966) subdivided the Great Lake and the Till Plains physiographic sections into the Northern Moraine and Lake Region and the Tipton Till Plain. In the area of the UIRB, the Northern Moraine and Lake Region subsection was further divided into the Valparaiso Morainal Area, the Kankakee Outwash and Lacustrine Plain, and the Steuben Morainal Lake Area (Schneider, 1966).

Although the physiography has been delineated and named in a various ways, defining characteristics of the physiographic sections correspond well across State lines. The Valparaiso Morainal Area in Indiana corresponds to the Wheaton Morainal Plain in Illinois. The Kankakee Outwash and Lacustrine Plain in Indiana corresponds to the Kankakee Till Plain in Illinois. The Tipton Till Plain in Indiana corresponds to the Bloomington Ridged Plain in Illinois.

The Chicago Lake Plain (4.7 percent of the basin) is approximately the area that is now metropolitan Chicago in the Chicago River Basin. It is a relatively flat, glacio-lacustrine deposit formed by the slow moving waters of glacial Lake Chicago. The Chicago Lake Plain consists of poorly drained lake clay and silt and lake sand and gravel. Clayey till of the Wedron Formation also is present and is deposited as moraines. Local topography typically varies less than 50 ft with a minimum elevation of 580 ft and a maximum elevation of 699 ft above sea level.

Map showing surface topography in the upper Illinois River Basin.

The Wheaton Morainal Plain (32 percent of the basin) is approximately the area of the upper Fox River Basin and the northern portion of the Kankakee River Basin. This area is characterized by gently rolling Wisconsinan-age moraines that are approximately parallel to the Lake Michigan shoreline. The Wheaton Morainal Plain is predominately clayey till, sandy loamy till, and sand and gravel. Other surficial deposits in this area include lake clay and silt, and alluvium. Relief is generally less than 100 ft with a minimum elevation of 505 ft and a maximum elevation of 1,188 ft above sea level.

The Kankakee Till Plain (37 percent of the basin) is approximately the area covered by the western three-quarters of the Kankakee River Basin, the Illinois River Basin, and the western part of the Iroquois River Basin. The Kankakee Till Plain is an outwash plain formed by the variable gradient, variable volume, and variable velocity of glacial floods (Mickelson and others, 1984). Surficial deposits are predominately outwash sand and gravel, but also include alluvium and fill materials. Local changes in elevation are generally less than 100 ft with a minimum elevation of 482 ft and a maximum elevation of 899 ft above sea level.

The Bloomington Ridged Plain (22 percent of the basin) is approximately the area of the lower Fox River Basin and the southern part of the Iroquois River Basin. Surficial deposits in this area are mostly loamy till and clayey till deposited as moraines. The lower Fox River Basin has well developed rolling moraines whereas the southern part of the Iroquois River Basin has lower and more gently rolling moraines. In the Iroquois River Basin, the Bloomington Ridged Plain is mostly loamy till, and lake clay and silt deposits. Topography in upland areas of the Bloomington Ridged Plain is flat or gently rolling. Lowland areas, such as along the Fox and Illinois Rivers, are very hilly and rugged with local relief as great as 300 ft where the rivers are deeply incised and bedrock is exposed (Piskin and Bergstrom, 1975). Topography generally varies less than 300 ft with a minimum elevation of 472 ft and a maximum elevation of 981 ft above sea level.

The Steuben Morainal Lake Area (4.3 percent of the basin) is the eastern-most part of the Kankakee River Basin. This area is characterized by hilly knob and kettle glacial terrain. Knobs are formed when a melting glacier deposits hills of sand and gravel into a depression left by the ice. Kettles are formed when ice blocks from a glacier melt in depressions left by the ice. The kettles form the basins for many kames and peat bogs in the area. Surficial deposits are predominately loamy till. Topography is generally less than 100 ft with a minimum elevation of 721 ft and a maximum elevation of 899 ft above sea level (Schneider, 1966).

REFERENCES

Fenneman, N.M., 1938, Physiography of the eastern United States: New York, McGraw-Hill Book Co., 714 p.

Gray, H.H., Ault, C.H., and Keller, S.J., comps., 1987, Bedrock geologic map of Indiana: Indiana Geological Survey, scale 1:500,000.

Illinois State Geological Survey, 1973, Pleistocene glaciations in Illinois: Illinois State Geological Survey, Educational Extension Publications, 10 p., 5 maps (revised 1988)

Leighton, M.M., Ekblaw, G.E., and Horberg, C.L., 1948, Physiographic divisions of Illinois: Illinois State Geological Survey Report of Investigation 129, 19p.

Mickelson, D.M., Clayton, L., Baker, R.W., Mode, W.N., Schneider, A.F., 1984, Pleistocene stratigraphic units of Wisconsin: Wisconsin Geology and Natural History Survey, Miscellaneous Paper 84-1, 82 p.

Piskin, K., Bergstrom, R.E., 1975, Glacial drift in Illinois—thickness and character: Illinois State Geological Survey, Circular 490, 35 p., 2 plates

Schneider, A.F., 1966, Physiography: The Indiana Sesquicentennial Volume, Natural Features of Indiana, Indiana Academy of Science, State Library, Indianapolis, Indiana, ? p. (reprinted [n.d.], Indiana Geological Survey, p. 15)

U.S. Geological Survey, [n.d.], Digital Elevation Model—30-arc second: U.S. Geological Survey, digital data.

Willman, H., Atherton, E., Buschbach, T., Collinson, C., Frye, J., Hopkins, M., Lineback, J., Simon, J., 1975. Handbook of Illinois Stratigraphy: Illinois State Geological Survey Bulletin 95, 261 p.

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