Historical:Bonpas Limestone Member
M. E. Hopkins and J. A. Simon
The Bonpas Limestone Member of the Mattoon Formation (Kosanke et al., 1960, p. 41) is named for Bonpas Creek, Richland County.
The type section is in a roadcut exposure about 1.5 miles west of Bonpas Creek, the same location as the Calhoun Coal type section (Kosanke et al., 1960, p. 41, 82).
It previously was called Calhoun Limestone (Weller, in Dunbar and Henbest, 1942, p. 27).
It is correlated with the Omega Limestone of the western side of the area covered by the Mattoon Formation.
Extent and Thickness
The Bonpas is 3 feet thick in the type locality and is widely distributed in eastern Illinois.
The Bonpas contains a varied open-marine fauna.
DUNBAR, C. O., and L. G. HENBEST, 1942, Pennsylvanian Fusulinidae of Illinois: Illinois State Geological Survey Bulletin 67, 218 p.
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.
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