The Brassfield Formation, named by A.F. Foerste in 1906, is a

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...

and

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

formation exposed in Arkansas, Ohio, Kentucky, Indiana, Tennessee and West Virginia in the United States.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. It is Early

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleoz ...

(Aeronian, Llandoverian) in age and well known for its abundant

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the ...

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and se ...

s and stromatoporoids.Schneider, K.A. and Ausich, W.I. 2002. Paleoecology of framebuilders in Early Silurian reefs (Brassfield Formation, southwestern Ohio). ''Palaios'' 17: 237-248. In Ohio, where the unit has escaped dolomitization, the Brassfield is an

encrinite Encrinites are a type of grain-supported bioclastic sedimentary rock in which all or most of the grains are crinoid ossicles. In older literature, the word is sometimes used to refer to individual fossil crinoids, but this usage is obsolete. Di ...

biosparite Fossiliferous limestone is any type of limestone, made mostly of calcium carbonate (CaCO3) in the form of the minerals calcite or aragonite, that contains an abundance of fossils or fossil traces. The fossils in these rocks may be of macroscopic ...

with numerous

crinoid Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, which are ...

species.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. File:BrassfieldEncrinite042112.jpg, Close view of Brassfield Formation near Fairborn, Ohio, showing grains mainly composed of crinoid fragments. File:Phaenopora superba Silurian Brassfield.jpeg, ''Phaenopora superba'', a

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a ...

n from the Brassfield Formation. File:BrassfieldEncrinite041915.JPG, Encrinite from the Brassfield Formation (Silurian) near Fairborn, Ohio.

References

Silurian System of North America Silurian Arkansas Silurian Indiana Silurian Kentucky Geologic formations of Ohio Geologic formations of Tennessee Geologic formations of West Virginia Silurian southern paleotemperate deposits Rhuddanian Aeronian Telychian {{US-geologic-formation-stub