Schweizer Member

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Lithostratigraphy: Hunton Limestone Megagroup >>Wilhelmi Formation >>Schweizer Member
Chronostratigraphy: Paleozoic Erathem >>Silurian System >>Alexandrian Series
Allostratigraphy: Tippecanoe Sequence

Primary source

Willman, H. B., Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, and Jack A. Simon, 1975, Handbook of Illinois Stratigraphy: Illinois State Geological Survey Bulletin 95, 261 p.

Contributing author(s)

H. B. Willman and Elwood Atherton


Original description

The Schweizer Member of the Wilhelmi Formation (Willman, 1973, p. 13).


Named for Schweizer School a mile east of the type section.

Other names


Type section

Type location

The type section of the Schweizer Member is part of the Wilhelmi Formation type section, located in a railroad cut about 5 miles southwest of Wilhelmi Airport (SE SW SE 35, 35N-9E).

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

The Schweizer Member is the basal member of the Wilhelmi Formation.

Extent and thickness

Although widely present in subsurface in northeastern Illinois and as much as 80 feet thick, the Schweizer Member is well exposed only in and near the type section, where it is 25 feet thick.


The Schweizer Member consists of medium to dark gray dolomitic shale at the base that grades to very argillaceous, silty dolomite at the top. A thin bed of limestone conglomerate marks the base in the type section.




Well log characteristics


Age and correlation

Environments of deposition

Economic importance



WILLMAN, H. B., 1973, Rock stratigraphy of the Silurian System in northeastern and northwestern Illinois: Illinois State Geological Survey Circular 479, 55 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation