Historical:Anna Shale Member
M. E. Hopkins and J. A. Simon
The Anna Shale Member of the Carbondale Formation (Jewett, 1941, p. 316-317) is named for Anna, Bourbon County, Kansas.
The Anna is persistent and generally accompanies the overlying Brereton Limestone, but in parts of southern Illinois the Anna lenses out and the Brereton Limestone lies directly on the Herrin (No. 6) Coal. The Anna otherwise generally lies in abrupt contact with the Herrin Coal, except where the thick wedges of silty gray shale intervene.
It is a fissile, black, hard, carbonaceous shale that seldom is as much as 4 feet thick. Locally it contains dark gray, impure limestone concretions up to a foot thick. The Anna Shale and the Brereton Limestone, and locally even higher units, thin to zero over the gray shale wedges.
The Anna has a nektonic and planktonic marine fauna and many of the shells are fragmentary and pyritized.
JEWETT, J. M., 1941, Classification of the Marmaton Group, Pennsylvanian, in Kansas: Kansas Geological Survey Bulletin 58, p. 1-148.
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