St. Louis Limestone

St. Louis Limestone
Stratigraphic range: Mississippian Sub-period
Rock anhydrite (St. Louis Limestone; subsurface gypsum mine in Martin County, Indiana)
TypeGeological formation
Unit ofBlue River Group
Sub-unitsDover Chert, Horse Cave Member, Sisson Member
UnderliesSte. Genevieve Limestone
OverliesSalem Formation[1]
Thicknessup to 100 feet (30 m)[2]
Lithology
PrimaryLimestone
OtherShale, chert[2]
Location
RegionIllinois, Indiana, Tennessee, Kentucky and Missouri
CountryUnited States
Type section
Named forSt. Louis, Missouri[1]
Named byEnglemann
Year defined1847
Geological map of Mammoth Cave National Park, incl. St. Louis Limestone
Outcrops of the St. Louis Limestone near Frenchburg, Kentucky

The St. Louis Limestone is a large geologic formation covering a wide area of the midwest of the United States. It is named after an exposure at St. Louis, Missouri. It consists of sedimentary limestone with scattered chert beds, including the heavily chertified Lost River Chert Bed in the Horse Cave Member. It is exposed at the surface through western Kentucky and Middle Tennessee, including the city of Clarksville, Tennessee. 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 rugosan corals Lithostrotion and Lithostrotionella and the bryozoan Fenestrellina.