The St. Louis Limestone is a large

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

covering a wide area of the midwest of the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

. It is named after an exposure at

St. Louis, Missouri St. Louis () is the second-largest city in Missouri, United States. It sits near the confluence of the Mississippi and the Missouri Rivers. In 2020, the city proper had a population of 301,578, while the bi-state metropolitan area, which e ...

. It consists of sedimentary

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 whe ...

with scattered

chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a ...

beds, including the heavily chertified Lost River Chert Bed in the Horse Cave Member. It is exposed at the surface through western

Kentucky Kentucky ( , ), officially the Commonwealth of Kentucky, is a state in the Southeastern region of the United States and one of the states of the Upper South. It borders Illinois, Indiana, and Ohio to the north; West Virginia and Virginia ...

and

Middle Tennessee Middle Tennessee is one of the three Grand Divisions of the U.S. state of Tennessee that composes roughly the central portion of the state. It is delineated according to state law as 41 of the state's 95 counties. Middle Tennessee contains the ...

, including the city of

Clarksville, Tennessee Clarksville is the county seat of Montgomery County, Tennessee, United States. It is the fifth-largest city in the state behind Nashville, Memphis, Tennessee, Memphis, Knoxville, and Chattanooga. The city had a population of 166,722 as of the 202 ...

. The limestone deposit is Mississippian in age, in the Meramecian series, roughly 330-340 million years old. Fossils commonly found in the St. Louis include the

rugosa The rugosa, also called the tetracorallia or horn coral, are an extinct order of solitary and colonial corals that were abundant in Middle Ordovician to Late Permian seas. Solitary rugosans (e.g., '' Caninia'', '' Lophophyllidium'', '' Neoza ...

n corals '' Lithostrotion'' and '' Lithostrotionella'' and the bryozoan '' Fenestrellina''.

References

Limestone formations of the United States Mississippian United States Carboniferous Kentucky Carboniferous Missouri Carboniferous geology of Virginia Carboniferous geology of Tennessee Mississippian Illinois Carboniferous southern paleotropical deposits {{US-geologic-formation-stub

See also

References