Bonpas Limestone Member

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Lithostratigraphy: McLeansboro Group >>Mattoon Formation >>Bonpas Limestone Member
Chronostratigraphy: Paleozoic Erathem >>Pennsylvanian Subsystem >>Missourian Series
Allostratigraphy: Absaroka Sequence

Primary source

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.

Contributing author(s)

M. E. Hopkins and J. A. Simon


Original description

The Bonpas Limestone Member of the Mattoon Formation (Kosanke et al., 1960, p. 41).


Named for Bonpas Creek, Richland County.

Other names

It previously was called Calhoun Limestone (Weller, in Dunbar and Henbest, 1942, p. 27).


Type section

Type location

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).

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

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

Economic importance



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.

ISGS Codes

Stratigraphic Code Geo Unit Designation