Bonpas Limestone 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 Bonpas Limestone Member of the Mattoon Formation (Kosanke et al., 1960, p. 41).
Named for Bonpas Creek, Richland County.
It previously was called Calhoun Limestone (Weller, in Dunbar and Henbest, 1942, p. 27).
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).
Extent and thickness
The Bonpas is 3 feet thick in the type locality and is widely distributed in eastern Illinois.
Well log characteristics
The Bonpas contains a varied open-marine fauna.
Age and correlation
It is correlated with the Omega Limestone of the western side of the area covered by the Mattoon Formation.
Environments of deposition
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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