Girkin Formation
Encyclopedia
The Girkin Formation is a geologic formation
located in the Chester Escarpment of central Kentucky
, USA. It comprises a level of Mammoth Cave and lies above the Ste. Genevieve Limestone
and St. Louis Limestone
and below the Big Clifty Sandstone
in that area. The Girkin is a limestone
Mississippian
in age.
Members of the Girkin are as follows in descending order:
Geologic formation
A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
located in the Chester Escarpment of central Kentucky
Kentucky
The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...
, USA. It comprises a level of Mammoth Cave and lies above the Ste. Genevieve Limestone
Ste. Genevieve Limestone
The Ste. Genevieve Limestone is a geologic formation named for Ste. Genevieve, Missouri where it is exposed and was first described. It is a thick-bedded limestone that overlies the St. Louis Limestone. Both are Mississippian in age and part of the Meramecian series.Members of the Ste...
and St. Louis Limestone
St. Louis Limestone
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...
and below the Big Clifty Sandstone
Big Clifty Sandstone
The Big Clifty Sandstone is a geologic formation in Kentucky. It is sandstone that is Pennsylvanian in age. At Mammoth Cave National Park it overlies the Girkin Formation, the Ste. Genevieve Limestone, and the St. Louis Limestone, providing a cap for the entire cave system...
in that area. The Girkin is a limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
Mississippian
Mississippian (geologic period)
The Mississippian is a subperiod in the geologic timescale or a subsystem of the geologic record. It is the earliest/lowermost of two subperiods of the Carboniferous period lasting from roughly 359 to 318 Ma...
in age.
Members of the Girkin are as follows in descending order:
- Beech Creek Member
- Elwren Member
- Reelsville Member
- Sample Member
- Beaver Bend Member
- Bethel Member
- Paoli Member