Elwood Atherton, Charles Collinson, and Jerry A. Lineback
The Elviran Stage (Swann, 1963, p. 23, 65), originally called the Elvira Group (J. M. Weller, 1939), is named for Elvira Township, Johnson County (12S-2E).
The Elviran Stage is the youngest stage of the Chesterian Series. It includes the nine formations younger than the Glen Dean Limestone (fig. M-25).
The limestones of the Elviran Stage are generally darker and finer grained and contain more silt and argillaceous material and less abundant fossils than the older Chesterian limestones.
Representative fossils include Pentremites fohsi, Pterotocrinus menardensis, Composita subquadrata, Eumetria costata, and Sulcatopinna missouriensis.
SWANN, D. H., 1963, Classification of Genevievian and Chesterian (Late Mississippian) rocks of Illinois: Illinois State Geological Survey Report of Investigations 216, 91 p.
WELLER, J. M., 1939, Mississippian System: Kansas Geological Society Guidebook, 13th Annual Field Conference, southwestern Illinois and southeastern Missouri, p. 131-137.
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