THREE DIMENSIONAL HYDROGEOLOGIC INVESTIGATION OF THE KISHWAUKEE CHANNEL, NORTHERN ILLINOIS, USA

The Kishwaukee Channel is a buried bedrock valley in north-central Illinois that first developed prior to the Laurentide glaciations. It also served as a glacial spillway during the Pre-Illinois, Illinois and Wisconsin glaciations. This project entailed the construction of a 3D geologic model of the Kishwaukee Channel fill materials to quantify the spatial relationships between these sediments and the underlying Ordovician strata. Existing data was compiled from publically available geophysical and water well bore hole logs and supplemented by seismic refraction profiling. Using these data, a 3D geologic model of the Kishwaukee Channel was built in Surfer and ArcGIS that depicts a southwest trending U-shaped valley that is approximately 30 km (18 mi) long and 1.6 km (1 mi) wide. Terraces of Henry formation outwash fill the channel while Glasford formation tills cover the upland surfaces. To the east the Channel is carved into resistant Galena and Platteville group carbonates creating steep valley walls. To the west, the top of the St. Peter sandstone is entrenched forming gentle slopes. The Kishwaukee Channel is geometrically related to the Paleozoic Plum River Fault, which likely controlled the position of the Channel. We interpret the Kishwaukee Channel first formed as a minor drainage feature on the preglacial Galena Upland. Mesozoic deformation and Quaternary glacial action entrenched and buried the Kishwaukee Channel. Ultimately, the 3D model of the Kishwaukee Channel has helped improved the resolution of the preglacial and glacial history of Northern Illinois and will provide the basis for future hydrologic investigations within the study area.