Covel Conglomerate Bed
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.
M. E. Hopkins and J. A. Simon
The Covel Conglomerate Member of the Carbondale Formation (Willman, 1939, p. 174-176).
Named for Covel Creek in La Salle County.
The type section is along Covel Creek near its mouth (SE SW 26, 33N-3E) (Willman and Payne, 1942, p. 116; Wanless, 1956, p. 10).
Extent and thickness
This unit is remarkably persistent in northern Illinois and is locally present in western and eastern Illinois. The Covel is generally 1-3 inches thick and is an easily recognized stratigraphic marker. It is also present in southern Iowa and western Indiana (Wanless, 1957).
It is composed of rounded, dark gray to black, phosphatic limestone pebbles and water-worn marine fossils in a matrix of lighter gray limestone or of pyrite. In many places the member is covered with laminated algal growths.
Well log characteristics
Age and correlation
Environments of deposition
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.
WILLMAN, H. B., 1939, Covel Conglomerate, a guide bed in the Pennsylvanian of northern Illinois: Illinois Academy of Science Transactions, v. 32, p. 174-176; Illinois State Geological Survey Circular 60, p. 8-10.
WILLMAN, H. B., and J. N. PAYNE, 1942, Geology and mineral resources of the Marseilles, Ottawa, and Streator Quadrangles: Illinois State Geological Survey Bulletin 66, 388 p.
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