FROM START TO FINISH: THREE-DIMENSIONAL GEOLOGIC MAPS AND MODELS OF LAKE COUNTY, ILLINOIS

The Great Lakes Geologic Mapping Coalition is a partnership that includes the state geological surveys of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin; the Ontario Geological Survey; and the U.S. Geological Survey. The partnership builds on the collective knowledge of these scientific organizations to map the glacial geology of the of the Great Lakes states in high priority areas. Geologists and other staff use innovative computer aided mapping, drilling, and geophysical technologies and methods to discover and document complex stratigraphic and depositional relationships. Cornerstones of the Coalition are three-dimensional mapping and modeling and the application of maps and models to solving societal issues.

A three-dimensional geologic model for Lake County, Illinois has been made by the Illinois State Geological Survey (ISGS) based on analysis of more than 200 exploration boreholes, 24,000 water-well and engineering borehole records, and several miles of geophysical transect data. A data-sharing agreement with the county has facilitated the exchange of digital data, including access to county-wide, high-accuracy datasets that facilitate mapping and quality control of public domain information, such as water-well records.

In Lake County, the variability of the continuity and physical characteristics of deposits, typically associated with a number of inset proglacial depositional sequences, necessitates application of both lithostratigraphy and allostratigraphy to map and model geologic surfaces. A number of map units are defined based on genesis, as a practical matter, where bounding surfaces are more readily identified than the boundaries of discrete lithologic units.

Throughout the mapping process, ISGS staff have interacted with local decision makers to both gain an understanding of local natural resource issues, and to provide geologic information to those making decisions. Interactions have included presentations to the county board, local municipalities, industry, and the general public. Future challenges include the design and presentation of the three-dimensional model for the end user, noting users may not have the software and hardware capabilities used to make the maps and models.