Bankston Fork Limestone Member

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Lithostratigraphy: Kewanee Group >>Carbondale Formation >>Bankston Fork Limestone Member
Chronostratigraphy: Paleozoic Erathem >>Pennsylvanian Subsystem >>Desmoinesian Series
Allostratigraphy: Absaroka 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)

M. E. Hopkins and J. A. Simon


Original description

The Bankston Fork Limestone Member of the Carbondale Formation (Cady, 1926, p. 261-262).


Named for Bankston Creek in Saline County.

Other names


Type section

Type location

The type section consists of outcrops along the south side of Bankston Creek (NE NW 19, 9S-5E).

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

Extent and thickness

It occurs in southwestern, central, eastern, and southeastern Illinois, where it is commonly several feet thick but seldom over 6 feet. It does not occur west of the Illinois River or in northern Illinois. It commonly is not present over the thick portions of the Anvil Rock Sandstone.


The Bankston Fork is a fine-grained, argillaceous, thick-bedded limestone that is dolomitic in places (fig. P-3B). It is commonly nodular in the upper and lower portions and is generally divided into two benches by a greenish gray shale several inches thick.




Well log characteristics


It is sparsely fossiliferous, its open-marine fauna dominated by brachiopods, fusulinids, and a few crinoids.

Age and correlation

The Bankston Fork correlates with the Universal Limestone Member of Indiana and is present in parts of western Kentucky, where it locally is as much as 8 feet thick.

Environments of deposition

Economic importance



CADY, G. H., 1926, Areal geology of Saline County: Illinois Academy of Science Transactions, v. 19, p. 250-272.

ISGS Codes

Stratigraphic Code Geo Unit Designation