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.
H. B. Willman and T. C. Buschbach
The Shullsburg Member of the Quimbys Mill Formation (Templeton and Willman, 1963, p. 92).
Named for Shullsburg, Lafayette County, Wisconsin, 5 miles east of the 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.
The Shullsburg Member overlies the Hazel Green Member of the Quimbys Mill Formation.
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.
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.
Well log characteristics
Age and correlation
Environments of deposition
TEMPLETON, J. S., and H. B. WILLMAN, 1963, Champlainian Series (Middle Ordovician) in Illinois: Illinois State Geological Survey Bulletin 89, 260 p.
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