St. David Limestone Member
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
Name
Original description
The St. David Limestone Member of the Carbondale Formation (Savage, 1927, p. 309).
Derivation
Named for St. David, Fulton County.
Other names
History/background
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.
Lithology
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.
Core(s)
Photograph(s)
Contacts
Well log characteristics
Fossils
Age and correlation
Environments of deposition
Economic importance
Remarks
References
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
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