Summary: River systems of the North American mid-continent, including the upper Mississippi River, developed over the course tens of millions of years and were then radically impacted by the cycles of glaciations over the past 2.5 million years. Here, we reinterpret the geologic evolution of the upper Mississippi River and present evidence that the uppermost Mississippi River basin (upstream of the confluence of the Mississippi and Wisconsin Rivers) evolved as a drainage system that carried water eastward into the Gulf of St. Lawrence and North Atlantic Ocean rather than south to the Gulf of Mexico.

The never-glaciated Driftless Area of southwest Wisconsin and northwest Illinois provides a key geographic window to observe geologic processes on a longer timescale than available in the glaciated Midwest. Geomorphic features in this region, primarily along the lower Wisconsin River, provide the crucial data for the interpretation of this earlier river network. Expansion to surrounding regions indicates that likely the entirety of Wisconsin and Minnesota were part of this northeast draining river system prior to reorganization of mid-continent rivers in response to glaciation.

Biography: Eric Carson is a research geologist with the Wisconsin Geological and Natural History Survey and is currently serving as Interim Director and State Geologist there. He received his B.S. (Geology) from West Virginia University, and both his M.S. (Geology) and Ph.D. (double major, Geology and Geography) from the University of Wisconsin-Madison. He has 20 years’ experience in academia and research. His research at the WGNHS investigates the timing of the last glaciation in Wisconsin, processes associated with rivers and flooding, and how landscapes evolve over timescales ranging from thousands to tens of millions of years.