Historical:Bankston Fork Limestone Member

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

Authors

M. E. Hopkins and J. A. Simon

Name Origin

The Bankston Fork Limestone Member of the Carbondale Formation (Cady, 1926, p. 261-262) is named for Bankston Creek in Saline County.

Type Section

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

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.

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.

Definition

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.

Fig. P-3B -- Strata overlying the Herrin (No. 6) Coal Member of the Carbondale Formation (at the man's feet), including the Bankston Fork Limestone Member (BF), Conant Limestone Member (C), Jamestown Coal Member (J, 1 inch thick), gray calcareous shale (gs), Brereton Limestone Member (B); in a strip mine southwest of Belleville, St. Clair County.

Fossils

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

References

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
2530	--