Brassfield Formation

The Brassfield Formation, named by A.F. Foerste in 1906, is a limestone and dolomite formation exposed in Arkansas,^[3] Ohio, Kentucky, Indiana, Tennessee and West Virginia in the United States.^[2] It is Early Silurian (Aeronian, Llandoverian) in age and well known for its abundant echinoderms, corals and stromatoporoids.^[4] In Ohio, where the unit has escaped dolomitization, the Brassfield is an encrinite biosparite with numerous crinoid species.^[5][6]

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  Close view of Brassfield Formation near Fairborn, Ohio, showing grains mainly composed of crinoid fragments.
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  Phaenopora superba, a bryozoan from the Brassfield Formation.
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  Encrinite from the Brassfield Formation (Silurian) near Fairborn, Ohio.

Brassfield Formation
Stratigraphic range: Rhuddanian - Telychian[1]Early Silurian PreꞒ Ꞓ O S D C P T J K Pg N ↓
Brassfield Formation exposed in Oakes Quarry near Fairborn, Ohio.
Type	Sedimentary
Underlies	Crab Orchard Formation, Dayton Formation, Osgood Formation, Salamonie Dolomite, and St. Clair Limestone
Overlies	Brainard Shale, Cason Shale, Drakes Formation, and Whitewater Formation
Lithology
Primary	Limestone
Other	dolomite
Location
Region	East-central USA
Country	United States
Extent	Arkansas, Indiana, Kentucky, Ohio, and Tennessee
Type section
Named for	Brassfield, Kentucky
Named by	August Frederick Foerste (1906, p. 18, 27)[2]