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] | |
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] |
References
edit- ^ The Silurian of central Kentucky, U.S.A.: Stratigraphy, palaeoenvironments and palaeoecology
- ^ a b 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.
- ^ McFarland, John David (2004) [1998]. "Stratigraphic summary of Arkansas" (PDF). Arkansas Geological Commission Information Circular. 36: 7–8. Archived from the original (PDF) on 2016-12-21. Retrieved 2018-01-11.
- ^ Schneider, K.A. and Ausich, W.I. 2002. Paleoecology of framebuilders in Early Silurian reefs (Brassfield Formation, southwestern Ohio). Palaios 17: 237-248.
- ^ Ausich, W.I. 1984. Calceocrinids from the Early Silurian (Llandoverian) Brassfield Formation of southwestern Ohio. Journal of Paleontology 58: 1167-1185.
- ^ 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.
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