St. David Limestone Member

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Lithostratigraphy: Kewanee Group >>Carbondale Formation >>St. David 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 St. David Limestone Member of the Carbondale Formation (Savage, 1927, p. 309).


Named for St. David, Fulton County.

Other names


Type section

Type location

The type section consists of outcrops near the village of St. David (SE SE 17, 6N-4E) (Wanless, 1956, p. 10; 1957, p. 105, 197).

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

Extent and thickness

The St. David is widespread in western Illinois, where its thickness is generally less than 1 foot but locally reaches 2 feet. In eastern and southwestern Illinois also it is persistent and locally is 3-4 feet thick. In southeastern Illinois and western Kentucky, it is continuous but is commonly no more than a few inches of very fossiliferous calcareous shale or impure limestone.


The St. David is a thin, dark gray, argillaceous limestone containing an abundant open-marine fauna dominated by brachiopods; it also contains a few fusulinids. It is almost invariably present where the Springfield-Harrisburg (No. 5) Coal occurs, although the limestone and coal are generally separated by 1-3 feet of black fissile shale. The underlying black fissile shale is widely characterized by an abundance of Dunbarella rectilaterarius (fig. P-6) in its lower few inches. The St. David is usually absent where the gray Dykersburg Shale, which underlies it in places, is more than 25 or 30 feet thick.




Well log characteristics


Age and correlation

Environments of deposition

Economic importance



SAVAGE, T. E., 1927, Significant breaks and overlaps in the Pennsylvanian rocks of Illinois: American Journal of Science, v. 14, p. 307-316.
WANLESS, H. R., 1956, Classification of the Pennsylvanian rocks of Illinois as of 1956: Illinois State Geological Survey Circular 217, 14 p.
WANLESS, H. R., 1957, Geology and mineral resources of the Beardstown, Glasford, Havana, and Vermont Quadrangles: Illinois State Geological Survey Bulletin 82, 233 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation