Historical:Tyson 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: Ottawa Limestone Megagroup >>Galena Group >>Decorah Subgroup >>Kings Lake Formation >>Tyson Member
Chronostratigraphy: Paleozoic Erathem >>Ordovician System >>Champlainian Series >>Trentonian Stage
Allostratigraphy: Tippecanoe Sequence


H. B. Willman and T. C. Buschbach

Name Origin

The Tyson Member of the Kings Lake Formation (Templeton and Willman, 1963, p. 111), the upper member, is named for Tyson Hollow, St. Louis County, Missouri, the mouth of which is 0.5 mile northeast of the type section.

Type Section

The type section of the Tyson Member is located in the same section as the Mincke type section (a railroad cut in the Meramec Valley bluff (near cen. E1/2 SE SE 21, 44N-4E)) where the Tyson is 7.5 feet thick.

Extent and Thickness

The Tyson Member thins northward to 4.3 feet in the Kings Lake type section and to 3.9 feet at New London, Missouri.


The Tyson Member is largely dolomitic, silty, argillaceous limestone that weathers buff and chalky. It occurs in medium to thick beds and contains a few thin beds of buff to reddish brown shale, coarse calcarenite, and coquinite.


TEMPLETON, J. S., and H. B. WILLMAN, 1963, Champlainian Series (Middle Ordovician) in Illinois: Illinois State Geological Survey Bulletin 89, 260 p.

ISGS Codes

Stratigraphic Code Geo Unit Designation