TIMING AND IMPLICATIONS OF LATE QUATERNARY SEDIMENT DEPOSITION AND LANDSCAPE EVOLUTION IN SOUTH-CENTRAL WISCONSIN
Notably absent throughout south-central Wisconsin are any deposits that are clearly older than Marine Isotope Stage 2 (MIS 2). This raises the question of what the ice-margin positions, drainage patterns, and overall landscape of south-central Wisconsin were like prior to the most recent glaciation. The current course of the Wisconsin River across the glacial Lake Wisconsin basin and around the east end of the Baraboo Hills is necessarily a post-glacial construct. Our recent research strongly indicates that the entirety of south-central Wisconsin drained to the northeast in pre-Quaternary time, and that the routing of the Wisconsin and upper Mississippi Rivers to the south is a result of likely middle Quaternary glaciations. In what direction, then, did water runoff in the interim between the apparent pre-Quaternary pattern of drainage toward the northeast and the modern drainage toward the south? The growing inventory of sedimentary basins with thick sequences of latest Pleistocene deposition in south-central Wisconsin suggest that MIS 2 materials deposited by the Green Bay Lobe may have exerted a primary control on routing the Wisconsin River to the south and southwest.