H. B. Willman and T. C. Buschbach
The Abernathy Member of the Joachim Dolomite (Templeton and Willman, 1963, p. 58), the basal member, is named for Abernathy School, 2 miles north of the type section.
The type section of the Abernathy Member is 1.5 miles east of Dutchtown, Missouri (SE NW NE 20, projected, 30N-13E). The upper 25.6 feet is exposed at the type section.
Extent and Thickness
In southern Illinois the Abernathy is present in the subsurface, extending northward as far as Jackson County. It is as much as 150 feet thick in a well in Pulaski County but more commonly is 50-100 feet thick.
The Abernathy Member is largely silty, sandy, thick-bedded dolomite containing layers of dolomitic, medium-grained sandstone. It contains some dark brown layers of limestone and dolomite. A persistent layer of sandstone of St. Peter type 1.5-14 feet thick occurs at the top. Chert is common just below the sandstone.
TEMPLETON, J. S., and H. B. WILLMAN, 1963, Champlainian Series (Middle Ordovician) in Illinois: Illinois State Geological Survey Bulletin 89, 260 p.
|Stratigraphic Code||Geo Unit Designation|