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North-Central Section - 47th Annual Meeting (2-3 May 2013)

Paper No. 2
Presentation Time: 8:00 AM-12:00 PM

QUATERNARY GEOLOGIC MAP OF FOND DU LAC COUNTY, WISCONSIN


MODE, William N., Department of Geology, University of Wisconsin - Oshkosh, Oshkosh, WI 54901, SANDERFOOT, Benjamin, Department of Geology, University of Wisconsin Oshkosh, 645 Dempsey Trail, Oshkosh, WI 54901-8649 and HOOYER, Thomas S., Department of Geosciences, University of Wisconsin-Milwaukee, P.O. Box 413, Lapham Hall 366, Milwaukee, WI 53201, sandeb88@uwosh.edu

The new Quaternary geologic map of Fond du Lac County, Wisconsin reveals diverse landscapes and surficial deposits, including lowlands underlain by glacial lake sediment and meltwater-stream sediment and uplands composed of till and meltwater-stream sediment. Map units combine sediment genesis, stratigraphic position, and landform association. Glacial sediments were deposited by the Green Bay and Lake Michigan lobes of the Laurentide Ice Sheet between about 19 and 11 ka BP during ice recession from the region (Syverson and Colgan, 2011). Glacial strata are divided into two formations, the Holy Hill and Kewaunee formations, that are distinguishable by the color and texture of the tills they contain. Kewaunee Formation deposits are restricted to the north-central part of the county. Holy Hill deposits are the surficial material in the southern part of the county and also occur beneath Kewaunee deposits in places. Glacial landforms include active-ice features (drumlins and end moraines) as well as ice-disintegration features (kettles, kames, ice-walled outwash plains, and eskers). Ice-disintegration features dominate the Kettle interlobate moraine in the eastern part of the county where the Green Bay and Lake Michigan lobes intersected. Glacial lake sediment was deposited in glacial lakes Fond du Lac and Oshkosh. Glacial lake Fond du Lac was impounded when the Green Bay Lobe readvanced (during overall recession) into Fond du Lac County. This advance terminated at the Eureka moraine and deposited till of the Kirby Lake Member of the Kewaunee Formation. A new AMS 14C date on plant macrofossils from the base of glacial Lake Fond du Lac sediment places the formation of the lake and the Eureka moraine at 15,500 cal yr BP. The ice margin soon receded from the Eureka moraine. The next readvance (13,700 cal yr BP), which buried the Two Creeks forest bed farther north, terminated north of the county. Glacial Lake Oshkosh persisted in Fond du Lac County until the Green Bay Lobe margin receded from the state 13,000 cal yr BP.

Session No. 11--Booth# 32

T10. Mapping the Glacial Geology of the Great Lakes States (Posters)
Thursday, 2 May 2013: 8:00 AM-12:00 PM
Courtyard (Schneider Hall)
Geological Society of America Abstracts with Programs. Vol. 45, No. 4, p.14
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