Anna Shale Member
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.
M. E. Hopkins and J. A. Simon
The Anna Shale Member of the Carbondale Formation (Jewett, 1941, p. 316-317).
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.
Extent and thickness
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.
Well log characteristics
The Anna has a nektonic and planktonic marine fauna and many of the shells are fragmentary and pyritized.
Age and correlation
Environments of deposition
JEWETT, J. M., 1941, Classification of the Marmaton Group, Pennsylvanian, in Kansas: Kansas Geological Survey Bulletin 58, p. 1-148.
|Stratigraphic Code||Geo Unit Designation|