Historical:Karnak Limestone Member
Elwood Atherton, Charles Collinson, and Jerry A. Lineback
The Karnak Limestone Member of the Ste. Genevieve Limestone (Swann, 1963, p. 28-29, 71) is named for Karnak, Pulaski County, about 4 miles southeast of the type section.
The type section of the Karnak Limestone Member is located in Johnson County (SW SW 32, 13S-2E, and NW NW 5, 14S-2E), where the top 16 feet of an estimated 20-25 feet of limestone is exposed in cuts on Illinois Highway 37.
Extent and Thickness
The Karnak is a persistent unit and is generally traceable throughout the area of the Ste. Genevieve (fig. M-22), but in western Washington County it thins and grades laterally into the Aux Vases Sandstone. The Karnak is generally 10-35 feet thick.
The limestone is relatively pure, oolitic, crinoidal, mostly light gray, and cross-bedded.
SWANN, D. H., 1963, Classification of Genevievian and Chesterian (Late Mississippian) rocks of Illinois: Illinois State Geological Survey Report of Investigations 216, 91 p.
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