Historical:Oak Grove Limestone Member
M. E. Hopkins and J. A. Simon
The Oak Grove Limestone Member of the Carbondale Formation, originally called the Oak Grove beds (Wanless, 1931a, p. 184, 187, 192), is named for Oak Grove School in Fulton County.
The type section is in a ravine just north of the Oak Grove School (SW SE 6, 5N-3E) (Wanless, 1956, p. 10; 1957, p. 91, 197).
Limestones equivalent to the Oak Grove are present in western Indiana, southern Iowa, and western Missouri.
Extent and Thickness
In western and northern Illinois the Oak Grove consists of a remarkably persistent sequence of thin, lithologically and paleontologically distinctive limestone beds. Most of them are only a few inches thick, but some are a few feet thick. They are interbedded with dark gray and black shale beds that also have characteristic properties (Wanless, 1957, p. 91-94). The total thickness of the Oak Grove seldom exceeds 15 feet. Limestone units are less abundant in the Oak Grove in southern Illinois.
The Lowell and Shawneetown Coals appear to occur within strata equivalent to the Oak Grove.
WANLESS, H. R., 1931a, Pennsylvanian cycles in western Illinois: Illinois State Geological Survey Bulletin 60, p.
WANLESS, H. R., 1956, Classification of the Pennsylvanian rocks of Illinois as of 1956: Illinois State Geological Survey Circular 217, 14 p.
WANLESS, H. R., 1957, Geology and mineral resources of the Beardstown, Glasford, Havana, and Vermont Quadrangles: Illinois State Geological Survey Bulletin 82, 233 p.
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