Cora Limestone Member

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Lithostratigraphy: Pope Megagroup >>Clore Formation >>Cora Limestone Member
Chronostratigraphy: Paleozoic Erathem >>Mississippian Subsystem >>Chesterian Series >>Elviran Stage
Allostratigraphy: Kaskaskia Sequence

Primary source

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.

Contributing author(s)

Elwood Atherton, Charles Collinson, and Jerry A. Lineback


Original description

The Cora Limestone Member of the Clore Formation (Swann, 1963, p. 40-41).


Named for Cora, Jackson County.

Other names


Type section

Type location

The type section of the Cora Limestone Member is at the mouth of Degonia Creek Hollow (SW SE 16, 8S-5W).

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

The Cora Limestone Member is the lowest member of the Clore Formation.

Extent and thickness

The Cora is 15-45 feet thick.


It varies from dominantly limestone to dominantly shale. In both facies, the Cora is interbedded limestone and shale and locally contains sandstone lenses.




Well log characteristics


A zone in the Cora Member in which the limestone surfaces are covered with delicate branching bryozoans is the Batostomella nitidula Peak Zone (S. Weller, 1926).

Age and correlation

Environments of deposition

Economic importance



SWANN, D. H., 1963, Classification of Genevievian and Chesterian (Late Mississippian) rocks of Illinois: Illinois State Geological Survey Report of Investigations 216, 91 p.
WELLER, STUART, 1926, Faunal zones in the standard Mississippian section: Journal of Geology, v. 34, p. 320-335.

ISGS Codes

Stratigraphic Code Geo Unit Designation