Brassfield Formation

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Brassfield Formation
Stratigraphic range: Early Silurian
Brassfield Formation exposed in Oakes Quarry near Fairborn, Ohio.
Type Sedimentary
Underlies Dayton Formation
Overlies Drakes Formation
Primary Limestone
Other Dolomite
Region East-central USA
Country United States
Extent East-central USA
Type section
Named for Brassfield, Kentucky
Named by Foerste (1906, p. 18, 27)

The Brassfield Formation, named by A.F. Foerste in 1906, is a limestone and dolomite formation exposed in Ohio, Kentucky, Indiana, Tennessee and West Virginia in the United States.[1] It is Early Silurian (Aeronian, Llandoverian) in age and well known for its abundant echinoderms, corals and stromatoporoids.[2] In Ohio, where the unit has escaped dolomitization, the Brassfield is an encrinite biosparite with numerous crinoid species.[3][4]


  1. ^ Foerste, A.F. 1906. The Silurian, Devonian, and Irvine formations of east-central Kentucky, with an account of their clays and limestones. Geological Survey of Kentucky, Bulletin 7, 369 p.
  2. ^ Schneider, K.A. and Ausich, W.I. 2002. Paleoecology of framebuilders in Early Silurian reefs (Brassfield Formation, southwestern Ohio). Palaios 17: 237-248.
  3. ^ Ausich, W.I. 1984. Calceocrinids from the Early Silurian (Llandoverian) Brassfield Formation of southwestern Ohio. Journal of Paleontology 58: 1167-1185.
  4. ^ Coogan, A.H. 1996. Ohio’s surface rocks and sediments, in Feldmann, R.M., and Hackathorn, M., eds., Fossils of Ohio: Ohio Department of Natural Resources, Division of Geological Survey Bulletin 70: 31–50.
Close view of Brassfield Formation near Fairborn, Ohio, showing grains mainly composed of crinoid fragments.
Phaenopora superba, a bryozoan from the Brassfield Formation.