Historical:Sheboygan Member

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Handbook of Illinois Stratigraphy
Series Bulletin 95
Author H. B. Willman, Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, Jack A. Simon
Date 1975
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Lithostratigraphy: Lake Michigan Formation >>Sheboygan Member
Chronostratigraphy: Cenozoic Erathem >>Quaternary System >>Holocene Series


John C. Frye and H. B. Willman

Name Origin

The Sheboygan Member of the Lake Michigan Formation (Lineback et al., 1970, p. 11) is named for Sheboygan, Sheboygan County, Wisconsin.

Type Section

The type section is the interval 112-219.3 cm in core 143, the same core as the type of the South Haven Member.

Extent and Thickness

The member ranges up to 4 feet thick. Its maximum development is in the mid-lake area and it occurs only where water depth exceeds 230 feet. It thins shoreward to the east, south, and west. It is absent from the southwestern part of the lake.

Stratigraphic Position

It is overlain by the Winnetka Member, and rests on the South Haven Member or the Equality Formation.


The member consists of two reddish brown to brown clay units separated by a thin, persistent layer of gray clay.


LINEBACK, J. A., N. J. AYER, and D. L. GROSS, 1970, Studies of Lake Michigan bottom sediments- No. 3. Stratigraphy of unconsolidated sediments in the southern part of Lake Michigan: Illinois State Geological Survey Environmental Geology Notes 35, 35 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation