De Long Coal Member
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 De Long Coal Member of the Spoon Formation (Wanless, 1931a, p. 188-192).
Named for De Long, Knox County.
It was called the Upper De Long Coal until "De Long," which had been applied to three coals, was restricted to the uppermost coal (Kosanke et al., 1960, p. 33).
It is the uppermost of three thin coals that crop out about 1 1/2 miles southwest of De Long along Brush Creek, the type locality (6, 8, 9N-2E) (Wanless, 1956, p. 9; 1957, p. 188-192).
The coal is separated from the overlying Seahorne Limestone by soft, poorly laminated shale 1-15 feet thick, and from the underlying Brush Coal by 1-3.5 feet of claystone and, commonly, a few inches of soft, light gray shale immediately over the Brush Coal.
Extent and thickness
The De Long Coal is widespread in western Illinois but is not known to be more than a few inches thick.
It is commonly made up of two thin coal seams separated by as much as 2 feet of claystone.
Well log characteristics
Age and correlation
The De Long Coal is correlated with the Mt. Rorah Coal of southern Illinois.
Environments of deposition
KOSANKE, R. M., J. A. SIMON, H. R. WANLESS, and H. B. WILLMAN, 1960, Classification of the Pennsylvanian strata of Illinois: Illinois State Geological Survey Report of Investigations 214, 84 p.
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.
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