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Geologic Unit: Rock Island
Map showing publication footprint
  • Usage in publication:
    • Rock Island (No. 1) Coal Member
  • Modifications:
    • Overview
  • AAPG geologic province:
    • Illinois basin
Publication:

Willman, H.B., Atherton, Elwood, Buschbach, T.C., Collinson, Charles, Frye, J.C., Hopkins, M.E., Lineback, J.A., and Simon, J.A., 1975, Handbook of Illinois stratigraphy: Illinois Geological Survey Bulletin, no. 95, 261 p.


Summary:

Rock Island (No. 1) Coal Member of Spoon Formation is basal member of Spoon in western IL. First called Coal Number 1 by Worthen (1868) because it was believed to be oldest (and first deposited) minable coal in Fulton, Morgan, Scott, and Schuyler Cos. Typically exposed in Spoon River Bluff near Seville, Fulton Co. (Worthen, 1870). Exposure was designated type section (SW1/4SW1/4 sec. 23, T6N, R1E) by Wanless (1957). As that coal was correlated with coal mined at Rock Island (Worthen and Shaw, 1873), the name Rock Island (No. 1) Coal came into general use. Occurs only in widely scattered areas. Attains a maximum thickness of about 8 ft in belts trending east-west or northeast-southwest (Wanless, 1965; Searight and Smith, 1969); in other places only a few inches to a foot or two of coal is present and it is absent throughout broad areas. Tentatively correlated with Assumption and Lithfield Coals of west-central IL. Has been correlated with Murphysboro Coal (Wanless, 1957) but floras indicate it is lower that Murphysboro (Kosanke, 1950). Correlated with Minshall Coal Member in Indiana.

Source: GNU records (USGS DDS-6; Reston GNULEX).


Map showing publication footprint
  • Usage in publication:
    • Rock Island Coal Member*
  • Modifications:
    • Biostratigraphic dating
  • AAPG geologic province:
    • Illinois basin
Publication:

Lesnikowska, A.D., and Willard, D.A., 1997, Two new species of Scolecopteris (Marattiales), source fructifications of the stratigraphically significant miospores Torispora securis Balme and Thymospora thiessenii (Kosanke) Wilson and Venkatachala, IN Paul, C., and Zodrow, E.L., eds., Euramerican Carboniferous paleobotany and coal geology; proceedings of the first Walter A. Bell memorial symposium: Review of Palaeobotany and Palynology, v. 95, nos. 1-4, p. 211-225.


Summary:

Cliffland Coal Member of Kalo Formation in Iowa has been correlated with Rock Island Coal Member of the Spoon Formation in IL, but its stratigraphic position is under debate. Authors favor a late Westphalian C to early Westphalian D age because THYMOSPORA PSEUDOTHIESSENII occurs in Cliffland Coal Member and base of THYMOSPORA epibole occurs near middle of Westphalian D in Illinois basin. Also assigned an early Desmoinesian age.

Source: GNU records (USGS DDS-6; Reston GNULEX).


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).

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