Historical:Cramer Limestone Member
M. E. Hopkins and J. A. Simon
The Cramer Limestone Member of the Modesto Formation (Kosanke et al., 1960, p. 38) is named for Cramer, Peoria County.
The type section consists of exposures in a ravine northeast of Pea Ridge School, 1.3 miles northeast of the village of Cramer (Wanless, 1956, p. 11; 1957, p. 121, 193).
It previously was called Trivoli Limestone (Wanless, 1931a, p. 182, 190, 192).
It is correlated with the Sniabar Limestone of southern Iowa, Missouri, and eastern Kansas.
Extent and Thickness
The Cramer is generally less than 1 foot thick. It is lenticular but widespread and is commonly found throughout the same area as the underlying Chapel (No. 8) Coal, from which it is commonly separated by 1-2 feet of black fissile shale.
The Cramer Limestone is normally very argillaceous.
The Cramer contains an abundant open-marine fauna.
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.
|Stratigraphic Code||Geo Unit Designation|