Historical:Rock Island Coal Member

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Handbook of Illinois Stratigraphy
Series Bulletin 95
Author H. B. Willman, Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, Jack A. Simon
Date 1975
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Lithostratigraphy: Kewanee Group >>Spoon Formation >>Rock Island Coal Member
Chronostratigraphy: Paleozoic Erathem >>Pennsylvanian Subsystem >>Desmoinesian Series
Allostratigraphy: Absaroka Sequence


M. E. Hopkins and J. A. Simon

Name Origin

The Rock Island (No. 1) Coal Member of the Spoon Formation is the basal named member of the formation in western Illinois. It was first called Coal Number 1 (Worthen, 1868, p. 6, 10, 11) because it was believed to be the oldest (the first deposited) minable coal in Fulton, Morgan, Scott, and Schuyler Counties. As the type section coal was correlated with the coal mined at Rock Island (Worthen and Shaw, 1873, p. 221, 229-232), the name Rock Island (No. 1) Coal came into general use.

Type Section

It is typically exposed in the Spoon River Bluff near Seville, Fulton County (Worthen, 1870, p. 194). This exposure was designated the type section (SW SW 23, 6N-1E) by Wanless (1957, p. 72, 201).


The Rock Island Coal is tentatively correlated with the Assumption and the Litchfield Coals of west-central Illinois. It has been correlated with the Murphysboro Coal (Wanless, 1957), but the floras indicate it is lower than the Murphysboro (Kosanke, 1950). It is correlated with the Minshall Coal Member of Indiana.

Extent and Thickness

In western Illinois the Rock Island (No. 1) Coal occurs only in widely scattered areas. It attains a maximum thickness of about 8 feet in belts trending east-west or northeast-southwest (Wanless, 1965, p. 27, 29-30; Searight and Smith, 1969, p. 13), in other places only a few inches to a foot or two of coal is present, and it is absent throughout broad areas.


KOSANKE, R. M., 1950, Pennsylvanian spores of Illinois and their use in correlation: Illinois State Geological Survey Bulletin 74, 128 p.
SEARIGHT, T. K., and W. H. SMITH, 1969, Strippable coal reserves of Illinois, Part 5B: Illinois State Geological Survey Circular 439, 22 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.
WANLESS, H. R., 1965, Environmental interpretation of coal distribution in the eastern and central United States: Illinois Mining Institute Proceedings, p. 19-35.
WORTHEN, A. H., 1868, Geology and paleontology: Geological Survey of Illinois, v. 3, 574 p.
WORTHEN, A. H., 1870, Geology and paleontology: Geological Survey of Illinois, v. 4, 508 p.
WORTHEN, A. H., and JAMES SHAW, 1873, Geology of Rock Island County: Geological Survey of Illinois, v. 5, p.217-234.

ISGS Codes

Stratigraphic Code Geo Unit Designation