Historical:Charter Member

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Handbook of Illinois Stratigraphy
Series Bulletin 95
Author H. B. Willman, Elwood Atherton, T. C. Buschbach, Charles Collinson, John C. Frye, M. E. Hopkins, Jerry A. Lineback, Jack A. Simon
Date 1975
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Lithostratigraphy: Potsdam Sandstone Megagroup >>Mt. Simon Sandstone >>Charter Member
Chronostratigraphy: Paleozoic Erathem >>Cambrian System >>Croixan Series >>Dresbachian Stage
Allostratigraphy: Sauk Sequence


T. C. Buschbach

Name Origin

The Charter Member of the Mt. Simon Sandstone (Templeton, 1950, p. 156), the uppermost member, is named for Charter Oak School, De Kalb County.

Type Section

The type section of the Charter Member of the Mt. Simon Sandstone is located 3.5 miles south of Charter Oak School, DeKalb County. It is the interval from 1381-1648 feet deep (sample set 1466) in the same boring as the Lacey Member.

Extent and Thickness

The Charter Member is 145-320 feet thick.


It is medium- to fine-grained, partly conglomeratic sandstone with some red micaceous shale at or near the base.


TEMPLETON, J. S., 1950, Mt. Simon Sandstone in northern Illinois: Illinois Academy of Science Transactions, v. 43, p. 151-159.

ISGS Codes

Stratigraphic Code Geo Unit Designation