APPLICATION OF AIRBORNE LIDAR-DERIVED DEM TO GLACIAL AND POSTGLACIAL LANDFORMS OF WILL COUNTY, ILLINOIS, UNITED-STATES: PRELIMINARY RESULTS

The Illinois State Geological Survey (ISGS) geologic mapping efforts in the suburban Chicago area address the mapping priorities of the State of Illinois, the Great Lakes Geologic Mapping Coalition, and the ISGS through the production of large-scale, 3-D geologic maps of the glacial deposits. The main objective of this study is to reconstruct the complex successions of ice marginal and frontal deposits in Will County by a geomorphologic approach based on LiDAR DEM. Therefore specific goals are to: (1) identify the nature of landforms and surficial deposits, (2) define their spatial and chronological relationships and (3) describe the paleogeography of Will County by using a time lapse sequence map of each major depositional event that reflect the dynamics of the Lake Michigan lobe.

Extensive field work was carried out in 2014, including surficial mapping, and detailed geologic investigations, and a resulting database is composed of ISGS testholes and archival waterwells borehole logs. Preliminary mapping at 1:50 000 scale, based on LiDAR DEM suggests that the Will County geomorphology can be divided into three main sedimentary facies according to their respective spatial relationships with the glacier: 1) glacial, 2) fluvial and 3) lacustrine. Moraines are conspicuous topographic ridges in the county. The most extensive one is the Valparaiso morainic system that covered most of the eastern portion of Will County. Fluvial channels flowing southwestward are found scattered in the central and the eastern part of Will County and are in almost all of the small valleys that drain the Valparaiso morainic system. In the western part of the county, there are extensive areas of flat, level topography produced by glacial Lake Wauponsee (Willman & Payne, 1942). Geomorphic evidence associated with the Kankakee Torrent (Ekblaw & Athy, 1925), has also been identified and mapped across this area.

Further work will focus on the characterization of the identified landforms based on various criteria like the nature of sediments, dimensions, elevation, texture, orientation, spatial relationship, and chronology. Paleoecological investigations will also be conducted on the different facies to gain information on environmental conditions, and to derive paleoclimatic interpretation of the lithostratigraphic units.