Historical:Macoupin Limestone Member
M. E. Hopkins and J. A. Simon
The Macoupin Limestone Member of the Modesto Formation (Wanless, 1931b, p. 810-811) is named for Macoupin Creek in Macoupin County.
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.
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