LAABS, Ben J., bjlaabs@students.wisc.edu; PRINCIPATO, Sarah M., Dept. of Geology and
Geophysics, University of Wisconsin, 1215 W Dayton St, Madison WI, 53706.

Late Wisconsin activity of the Lake Michigan Lobe of the Laurentide Ice Sheet is well recorded in the Lake Michigan shoreline bluffs of eastern Wisconsin. These deposits in northern Sheboygan County include three members of the red, clayey Kewaunee Formation and at least one member of the older gray Waubeka Member of the Holy Hill Formation. In this area, where roadcuts and other exposures are rare or do not exist, bluff exposures are most useful for surface mapping and interpretation of glacial history.

The diamicton units of the Kewaunee Formation are fairly continuous along the shoreline and are often separated by sand and gravel or lake sediments deposited during transgressions of Lake Michigan. However, physical characteristics of these tills are very similar and they are difficult to distinguish in outcrop. Grain size analyses of diamicton samples from northern Sheboygan County yield evidence for the presence of three members of the Kewaunee Formation: Ozaukee (14% sand, 43% silt, 43% clay), Haven (20% sand, 48% silt, 32% clay), and Valders (30% sand, 50% silt, 20% clay). The three members have similar Munsell colors, varying from reddish yellow to brown, and similar % calcite/dolomite (means range from .075 to .085). Ozaukee and Haven Members contain slightly lower magnetic susceptibility values (.00147 and .00138 MSK values respectively) than the Valders Member (.00171MSK value). Selected samples will be further analyzed to determine their clay mineralogy and microfabric. In-situ sand bodies and other characteristics imply most diamicton is basal till.

Diamicton of the Waubeka Member has 36% sand, 47% silt, 17 % clay and is more compact than the diamicton units of the Kewaunee Formation. This is unit is rarely exposed in the shoreline bluffs and underlies diamicton and lake deposits of the Haven and Ozaukee Members.
 
 This is a contribution of the Quaternary Geology group at the University of Wisconsin--Madison.  For complete citation return to publications list.