Brassfield Formation

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.

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