Interpreting past glacial dynamics from the glacial record requires that the depositional environ... more Interpreting past glacial dynamics from the glacial record requires that the depositional environments of glacial sediments and landforms be understood. In the case of interlobate deposits, models that incorporate various components of pro, supra and subglacial deposition have been developed and tested in the northern Kettle Moraine (nKM), Wisconsin; a large interlobate deposit that formed between the Green Bay and Lake Michigan lobes of the Laurentide Ice Sheet during the last deglaciation. In this paper, we interpret a new genesis for the nKM using sediment analysis and distribution along with landform distribution. In Sheboygan County, the nKM consists of two steep-sided, high-relief, hummocky ridges separated by a low elevation and lowrelief central axis. Gravel in the bounding hummocky ridges is well-sorted and well-rounded. Some bedding is collapsed. Large, isolated moulin kames are restricted to the axis area and composed of relatively poorly sorted, more angular gravel and diamicton. The distribution of these different sediments and landforms are explained by the accumulation of supraglacial debris that insulated the ice below the axis of the nKM, while the melting of cleaner ice on either side formed channels on the ice surface. As deglaciation proceeded, a substantial thickness of well-rounded, stream-deposited sand and gravel accumulated on ice in the bounding channels. Eventual collapse of this sediment formed the two hummocky ridges. Poorly sorted debris along the axis fell and slid into moulins and larger collapse areas in the ice. Thus, differential debris insulation and ice ablation controlled the mainly supraglacial deposition of this part of the nKM.
Appreciation is expressed to Jeff Bluske from La Crosse County and Jeff Helmuth of the Wisconsin ... more Appreciation is expressed to Jeff Bluske from La Crosse County and Jeff Helmuth of the Wisconsin Department of Natural Resources for their support for the project. Funding for this project was received from the County of La Crosse and Wisconsin Department of Natural Resources. Special thanks are given to Tom Berendes and Mark Johnson of the City of La Crosse Water Utility for their help in understanding the hydrologic system and the pumping stresses operating therein.
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Papers by Dawn Chapel