3-D GEOLOGIC MAPPING OF WILL COUNTY, ILLINOIS

As a county with urban, suburban, and rural environments, Will County is located at the confluence of the moraines of the Joliet sublobe, including the oldest (Minooka Moraine) as well as the outboard Lake Border Moraine (the Tinley Moraine). This project continues ISGS efforts in northeastern Illinois to map deposits at both land surface and in the subsurface to gain a better understanding of complexities left behind by repeated glaciations and associated flooding events. The main objective is to reconstruct the complex successions of ice marginal and paraglacial outwash deposits by a geomorphologic approach based on LiDAR DEM. In most cases, sediments and landforms are significant indicators of the extent of former ice-dammed lakes because their elevation is intimately linked to well-documented outlets. Their stratigraphic architecture is, however, complex, and their subsurface extent poorly documented. A methodology for three-dimensional numeric geomodelization of surficial deposits is proposed in this study. This kind of model is based on the integration of surficial sediments map and boreholes logs with the use of GIS and 3D geomodeling system. Most of the eastern portion of Will County is covered by the Valparaiso Morainic System. In the western part of the county, there are extensive areas of flat, level topography associated with an old lake plain formed by glacial Lake Wauponsee (Willman & Payne, 1942) and few lacustrine terraces and scarps associated with the former shorelines of this short-lived lake. Preliminary mapping, based on LiDAR-derived DEM has identified evidence of two glacigenic successions including some evidence of the Tiskilwa Till Member. Ice-walled lake plains and ice-marginal lakes associated with the Tinley Moraine have been identified. They will be characterized, and may contain fossils that can constrain the age of the Tinley Moraine. The discovery of new sections should be allow reassessment of depositional environments, correlation, and extent of the Haeger Member of the Lemont Formation (Wedron Group).