Historical:Shullsburg 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 >>Platteville Group >>Plattin Subgroup >>Quimbys Mill Formation >>Shullsburg Member
Chronostratigraphy: Paleozoic Erathem >>Ordovician System >>Champlainian Series >>Blackriveran Stage
Allostratigraphy: Tippecanoe Sequence

Authors

H. B. Willman and T. C. Buschbach

Name Origin

The Shullsburg Member of the Quimbys Mill Formation (Templeton and Willman, 1963, p. 92), which overlies the Hazel Green Member, is named for Shullsburg, Lafayette County, Wisconsin, 5 miles east of the type section.

Type Section

The type section of the Shullsburg Member is in the same type section as Quimbys Mill (a small quarry near Etna, Lafayette County, Wisconsin (SE SE 11, 1N-1E)) where it is 2.5 feet thick.

Extent and Thickness

The Shullsburg Member is as much as 5 feet thick in the northern outcrop area in Illinois and 7 feet in Calhoun County, but it thickens to about 20 feet near St. Louis and commonly is about 15 feet thick in outcrops south of there.

Description

The Shullsburg consists of brown to buff, slightly argillaceous, lithographic limestone or fine-grained dolomite. It is thin to medium bedded, strongly shaly in the north, but only slightly shaly in the southern outcrop area. In Missouri it contains some white, "glassy" beds. In northern Illinois the bedding surfaces at some places are mud-cracked or ripple-marked.

References

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
7890
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