Origin of hummocky glacigenic sediment near Burlington, southeastern Wisconsin
Schenning, James W.
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Three different geologic interpretations have been applied to the hummocky topography between Lake Geneva and Burlington, at the junction of Racine, Kenosha, and Walworth counties, southeastern Wisconsin. New evidence, unavailable to earlier researchers, is now presented based on observations from new gravel pits and the expansion of older ones. The results of this study are incorporated into a three-part model that combines two earlier and apparently disparate interpretations: a recessional moraine interpretation and a pitted outwash interpretation. This combination explains the Quaternary geology of the area better than either of the two interpretations can by itself. Stage 1 of this model depicts the area when it was still covered by the Woodfordian ice sheet. Sediments from previous glaciations are present as well as detritus from that most recent advance. During Stage 2 the glacier receded, stabilized and produced a kame and kettle, ice-contact recessional moraine. Stagnant blocks of ice that were separated and left in front of the glacier as it retreated, began to be buried by sand and silt outwash derived from meltwater streams emerging from the developing moraine. The abandoned blocks of ice were buried and subsequently melted slowly over time, finally resulting in a topography similar to that of the present-day recessional moraine with areas of pitted outwash farther from the old glacier margin.