Seahorne Limestone Member
Lithostratigraphy: Kewanee Group >>Spoon Formation >>Seahorne 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 Seahorne Limestone Member of the Spoon Formation (Wanless, 1931a, p. 191).
Derivation
Named for Seahorne Branch in Fulton County.
Other names
History/background
Type section
Type location
The type section consists of exposures along the Seahorne Branch stream (S 1/2 SE 5, 3N-3E) (Wanless, 1956, p. 9; 1957, p. 76, 200).
Type author(s)
Type status
Reference section
Reference location
Reference author(s)
Reference status
Stratigraphic relationships
Extent and thickness
The Seahorne is best known in western Illinois, where it varies from limestone nodules in claystone to a solid ledge of limestone more than 6 feet thick. The Seahorne is not persistent but occurs at many places in Illinois and adjacent states.
Lithology
It is usually light gray. In some places it is conglomeratic or brecciated and consists of dark gray fragments that contain abundant brachiopods embedded in a light gray matrix that is dominated by a diverse gastropod fauna. Another fauna, Spirorbis and ostracodes, is found at places and is generally considered nonmarine. It is the caprock of the Tebo coal in Missouri (Wanless, 1957).
Core(s)
Photograph(s)
Contacts
Well log characteristics
Fossils
Age and correlation
Environments of deposition
Economic importance
Remarks
References
WANLESS, H. R., 1931a, Pennsylvanian cycles in western Illinois: Illinois State Geological Survey Bulletin 60, p.
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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