Powell, Ross D.
M.S. (Master of Science)
Department of Geology
Sedimentation and deposition--Wisconsin; Lithofacies--Wisconsin; Geology; Stratigraphic--Pleistocene; Glaciers--Wisconsin; Geology--Wisconsin
Detailed deposystem analysis using lithofacies sequences, lithofacies associations and clast-fabric analyses have been conducted on Wisconsinan glacial and lacustrine successions exposed in coastal bluffs along Lake Michigan in southeast Wisconsin. Results indicate that the Laurentide Ice Sheet had a melting/freezing base where it terminated in a proglacial lake, as a tidewater front. Six different lithofacies types have been identified: (1) unstratified diamicton (sheet Dmu, lens Dmu); (2) stratified diamicton (Dms[r]); (3) interstratified silt and clay (Cld, Zld); (4) unstratified clay (Cud[r]); (5) stratified sand and gravel (G[sub s], S[sub s]); and (6) deformed silt and clay (Md). The oldest sequences preserve proglacial lake sediment of possible Glacial Lake Milwaukee origin. Glacial advance deformed and partially incorporated this sediment subglacially. The overlying subglacial till has previously been identified by others as the Wadsworth Till member of the Oak Creek Formation. Above the till are localized deposits of sediment gravity flows originating from a retreating grounding line. Next, ice-proximal lacustrine rythmites and deeper water muds were deposited along with iceberg-rafted debris. These deposits represent a large- scale glacial retreat previously identified as the Cary- Port Huron retreat. Glacial readvance deposited ice- proximal lacustrine silts and clays which were deformed a overlain by a second subglacial till. Large-scale faults and folds in sediments beneath tills, associated with plastically deformed silts and clays, and subglacial channel deposits indicate that the basal regime of the glacier was melting/freezing. Furthermore, dropstones and debris piles show that the glacier terminated as a grounded temperate glacier front which actively calved and produced icebergs.
Jung, David J., "Pleistocene glacilacustrine sedimentation and lithofacies models in Southeast Wisconsin" (1988). Graduate Research Theses & Dissertations. 4416.
xiii, 336 pages
Northern Illinois University
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