TOWARDS A COMPREHENSIVE ANALYSIS OF LATE-GLACIAL LAKE LEVELS WITHIN THE LAKE SUPERIOR BASIN

The increasing availability of LiDAR digital elevation models (DEMs) for Canada and the United States is improving our ability to recognize and detail the geomorphological record of former glacial lakes revealed by strandlines. More accurate strandline maps refine our understanding of glacial-isostatic adjustment (GIA), reveal information about deglacial ice margins, help identify rapid drawdown events and catastrophic flooding by ice dam failure, and advance models that connect waterplane curvature to age. Here we present new strandline maps in the Lake Superior Basin based on LiDAR DEMs from Wisconsin, Michigan, and Ontario. When combined with published records from Minnesota, they comprise the most extensive set of strandlines detailing former lake levels from any lake basin. Multiple lakes and lake phases are associated with these strandlines, including glacial lakes Wrenshall, Ontonagon, Duluth, Algonquin and Minong, as well as Holocene Lake Nipissing. The relative degree of strandline development varies widely, likely due to factors such as the availability of gravel and sand, length of time of formation, fetch, and local shoreline geometry (e.g. bay or headland). Strandlines for at least one level of glacial Lake Duluth are much more extensive on the southern shore, suggesting formation from only a very few numbers of storms with winds from the north. New LiDAR DEMs from the Sault Ste. Marie region are particularly helpful because they allow us to determine isobases (lines of equal GIA) across the primary basin outlet with high confidence. In general, our work supports the work of prior researchers, but adds details that are easily missed by field surveys or when using coarser resolution DEMs.