3-D MAPPING OF GLACIGENIC DEPOSITS IN NORTHEAST ILLINOIS: INTEGRATING MODELING AND VISUALIZATION SOFTWARE, DATABASES, AND DRILLING

On-going geologic mapping in northeast Illinois, supported in part since 2000 by the National Cooperative Geologic Mapping Program and the Central Great Lakes Geologic Mapping Coalition, has led to better understanding of the complex glacial record left by the Wisconsinan advances of the Lake Michigan Lobe. Detailed mapping in the area of Lake County, IL is providing critical information for land-use planning, environmental issues, aggregate resource evaluation, and groundwater supply assessment.

The glacial geology in Lake County is characterized by deposits of at least three Wisconsinan advances and the interaction of at least two sublobes of the Lake Michigan Lobe. The deposits range from 50-100 meters in thickness and include lithologically distinct tills that are intertongued with glaciolacustrine and glaciofluvial sediments. The saturated sand and gravel deposits are critical for private and municipal aquifer resources in the study area. In western Lake County, the area of current 3-D geologic mapping, the presence of overlapping and stagnant ice morphology creates a very complex glacial succession.

3-D geologic mapping of these deposits has extended from a pilot study of the Antioch Quadrangle to include three surrounding quadrangles, which encompass much of the complex ice-marginal facies in western Lake County. The integration of Rockworks software (Rockware, Inc.), custom database utilities, GIS, and 3-D visualization techniques coupled with an extensive drilling and geophysics program have been most valuable to improve 3-D mapping efficiency and quality.