Historical:Gunn 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 >>Gunn Member
Chronostratigraphy: Paleozoic Erathem >>Cambrian System >>Croixan Series >>Dresbachian Stage
Allostratigraphy: Sauk Sequence


T. C. Buschbach

Name Origin

The Gunn Member of the Mt. Simon Sandstone (Templeton, 1950, p. 155), which overlies the Lacey Member, is named for Gunn School, De Kalb County.

Type Section

The type section of the Gunn Member of the Mt. Simon Sandstone is located 2.75 miles southeast of Gunn School, De Kalb County. The member is 1648-1880 feet deep (sample set 1466) in the same boring as the Lacey Member.

Extent and Thickness

The Gunn Member is 130-150 feet thick in the Chicago area, but elsewhere it is 71-260 feet thick.


It is a relatively fine-grained member, but the sand ranges from fine to medium grained. A few thin conglomeratic beds are present in some areas.


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