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
Ancell Group (Templeton and Willman, 1963, p. 29).
Named for Ancell in southeastern Missouri.
The type section of the Ancell Group is a composite of several sections in the bluffs north of Ancell, between Dutchtown and Rock Levee, Missouri.
North of a line roughly extending from Chicago to Quincy, the Ancell strata above the St. Peter Sandstone consist of the members of the Glenwood Formation, but south of that line they consist of the Joachim and Dutchtown Formations (fig. O-15). The Glenwood, Dutchtown, and Joachim Formations all appear to have a facies relation to the upper part (Starved Rock Member) of the St. Peter Sandstone (fig. O-16).
Extent and thickness
As the Everton is present only in southern Illinois, the Ancell Group overlies Canadian strata in most of the state or Cambrian strata locally. Ancell strata underlie most of Illinois, and they vary in thickness from a few feet to as much as 900 feet.
The Ancell Group consists of the sandstone and the argillaceous and sandy limestone and dolomite formations that overlie the Everton Dolomite and underlie the Platteville Group, which is relatively pure limestone. The St. Peter Sandstone is the basal formation in the group.
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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