Historical:Cooper Limestone Member
Charles Collinson and Elwood Atherton
The Cooper Limestone Member of the Grand Tower Limestone (Swallow, 1855, p. 108, 196) is named for Cooper County, Missouri, where it is classified as a facies of the Calloway Limestone (Koenig, 1961).
The Cooper Limestone Member is similar to the Wapsipinicon Limestone north of the Sangamon Arch and probably is continuous with it west of Illinois.
Extent and Thickness
In Illinois the Cooper Limestone Member is as much as 50 feet thick in a belt 60-90 miles wide that extends eastward across the state south of the Sangamon Arch (fig. D-14). It is exposed only in Calhoun County (Meents and Swann, 1965), where it previously was considered part of the Cedar Valley Limestone.
On its northern margin the Cooper is overlapped by the Lingle Limestone, and on the south it grades laterally to the light-colored dolomite that overlies the Geneva Dolomite Member.
The Cooper Limestone Member is sparsely fossiliferous, gray, dense, lithographic, pure limestone, but it contains scattered grains of quartz sand in some localities.
KOENIG, J. W., 1961, Devonian System, in Stratigraphic succession in Missouri: Missouri Geological Survey, v. 40, p. 36-49.
MEENTS, W. F., and D. H. SWANN, 1965, Grand Tower Limestone (Devonian) of southern Illinois: Illinois State Geological Survey Circular 389, 34 p.
SWALLOW, G. C., 1855, Geology of Missouri: Missouri Geological Survey 2nd Annual Report, p. 59-170.
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