GLACIAL LANDSCAPE OF THE LATE WISCONSIN LAKE MICHIGAN LOBE IN NORTHEAST ILLINOIS: NEW INSIGHTS INTO ICE-MARGIN RETREAT AND PROCESSES

The mapping of glacial-landscape features in northeast Illinois and southeast Wisconsin have allowed detailed interpretation of the glacial recession and associated processes of a sublobe(s) of the late-Wisconsin Lake Michigan Lobe. Geomorphic relationships between prominent tunnel valleys and associated outwash fans indicate regional ice-margin positions and subglacial/proglacial meltwater-drainage patterns. High-resolution land-surface models from LiDAR data have also allowed mapping of newly-identified subtle landscape features. Hummocky-moraine assemblages, which include former ice-walled lake plains, indicate recessional ice-margin positions and ice-disintegration processes. Other subtle features such as lineations, segmented outwash fans and esker/ice-walled lake plain assemblages indicate local ice-margin positions and ice/meltwater flow directions during glacial retreat. The mapping of these features has led to a new interpretation of glacial history in this area, which has important implications for glacier retreat rates, processes and meltwater-discharge pathways.