Karnak Limestone Member
Willman, H. B., Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, and Jack A. Simon, 1975, Handbook of Illinois Stratigraphy: Illinois State Geological Survey Bulletin 95, 261 p.
Elwood Atherton, Charles Collinson, and Jerry A. Lineback
The Karnak Limestone Member of the Ste. Genevieve Limestone (Swann, 1963, p. 28-29, 71).
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.
Well log characteristics
Age and correlation
Environments of deposition
“Ohara” is an informal name applied to producing zones in the Karnak Limestone Member of the Ste. Genevieve Limestone.
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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