LITHOLOGIC AND PARTICLE-SIZE CHANGE OF OUTWASH SANDS AND GRAVELS ALONG FLOWPATHS OF THE GREEN BAY LOBE DURING THE WISCONSIN EPISODE DEGLACIATION, EASTERN WISCONSIN

During the Wisconsin Episode Glaciation, eastern and northeastern Wisconsin was covered by the Green Bay Lobe of the Laurentide Ice Sheet (LIS). When the lobe went through deglaciation between 18,000 and 10,000 ¹⁴C yr. B.P., extensive outwash deposits were left behind. This project uses thirteen outwash samples from various parts of eastern Wisconsin to study how the particle size of outwash changes down flow based on lithology. Samples of glacial outwash were collected from a total of thirteen sites: 12 sites that spanned the length and width of the Green Bay Lobe and one from the Wisconsin Valley Lobe during the last glaciation. These samples were then sieved through a series of sieves ranging from 50mm to 63µm. The sediment in each size was weighed and the composition documented to understand how the lithology of glacial outwash changes down the flowpath. As expected, there is a significant variance in particle size, which decreases down the flowpath of the glacier. Outwash from the eastern margin of the Green Bay Lobe (Manitowoc, Fond du Lac, Dodge and Washington counties) consists mostly of dolomite whereas that from the western margin (Waupaca and Waushara counties) contains more granite and rhyolite, which is reflective of the bedrock geology of Wisconsin showing the outwash is close to its source.