Historical:Macoupin Limestone 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: McLeansboro Group >>Modesto Formation >>Macoupin Limestone Member
Chronostratigraphy: Paleozoic Erathem >>Pennsylvanian Subsystem >>Missourian Series
Allostratigraphy: Absaroka Sequence


M. E. Hopkins and J. A. Simon

Name Origin

The Macoupin Limestone Member of the Modesto Formation (Wanless, 1931b, p. 810-811) is named for Macoupin Creek in Macoupin County.

Type Section

The type section is exposed along Macoupin Creek (NE NW 2, 9N-7W) (Wanless, 1956, p. 11; Ball, 1952, p. 85-86).

Extent and Thickness

It is a widespread unit, found throughout much of the Illinois Basin. The limestone is generally less than 2 but locally as much as 5 feet thick.


In the type area it is composed of thin, even beds of crinoidal limestone separated in places by shale partings. Most of it is dark gray and very argillaceous.


BALL, J. R., 1952, Geology and mineral resources of the Carlinville Quadrangle: Illinois State Geological Survey Bulletin 77, 110 p.
WANLESS, H. R., 1931b, Pennsylvanian section in western Illinois: Geological Society of America Bulletin, v. 42, p. 801-812.
WANLESS, H. R., 1956, Classification of the Pennsylvanian rocks of Illinois as of 1956: Illinois State Geological Survey Circular 217, 14 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation