Lithostratigraphy: Ottawa Limestone Megagroup >>Platteville Group >>Plattin Subgroup >>Mifflin Formation >>Brickeys Member
Chronostratigraphy: Paleozoic Erathem >>Ordovician System >>Champlainian Series >>Blackriveran Stage
Allostratigraphy: Tippecanoe Sequence
H. B. Wilman and T. C. Buschbach
The Brickeys Member of the Mifflin Formation (Templeton and Willman, 1963, p. 81) is named for Brickeys, Ste. Genevieve County, Missouri, which is 3 miles east of the type section.
The type section of the Brickeys Member is located in a quarry on the east side of Missouri Highway 25 (SE SW SE 28, 39N-7E), where the member is 15.5 feet thick.
Extent and Thickness
The Brickeys Member is commonly 13-20 feet thick in the outcrop area in Missouri but is as much as 40 feet thick in subsurface in southern Illinois. Where locally differentiated in the northern outcrop area, it is 1-2 feet thick.
In the southern area much of the Brickeys Member is relatively pure, brown, lithographic limestone, but it contains a few beds of gray to buff, argillaceous limestone and dolomite. Several beds are strongly oolitic; others are a fine conglomerate or breccia. The member also contains a few beds of green shale as much as 5 inches thick, domes of Stromatocerium, several scour surfaces with a relief of 2-8 inches, and, in one locality, a thin bentonite near the base. The shale beds are persistent from Calhoun County, Illinois, to Ste. Genevieve County, Missouri, but elsewhere the unit is dominantly a relatively pure limestone containing oolite beds. In the northern outcrop area the Brickeys is relatively pure but not oolitic.
The Brickeys Member contains domes of Stomatocerium.
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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