Historical:Troutman 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: Hunton Limestone Megagroup >>Kankakee Formation >>Troutman Member
Chronostratigraphy: Paleozoic Erathem >>Silurian System >>Alexandrian Series
Allostratigraphy: Tippecanoe Sequence


H. B. Willman and Elwood Atherton

Name Origin

The Troutman Member of the Kankakee Formation (Willman, 1973, p. 18), which overlies the Offerman Member, is named for Troutman Grove Cemetery, Will County, 2 miles south of the type section.

Type Section

Two miles north of Troutman Grove Cemetery, the lower part of the type section of the Troutman Member is in the same exposure as the Drummond Member, whereas the upper part is in a small quarry one-fourth of a mile east (SW NW SE 30, 35N-10E). The two sections are correlated by a thin bed of white clay that occurs near or slightly above the middle of the member in both sections and also in nearly all exposures of the member in northeastern Illinois.

Extent and Thickness

The Troutman is 27 feet thick in the type locality but thins to 11 feet along the Kankakee River.


The Troutman Member has the typical lithology of the Kankakee Formation. It contains a few widely scattered nodules of chert.


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