| Plattin Limestone | |
| Type: | Formation |
| Age: | Ordovician |
| Period: | Ordovician |
| Prilithology: | Limestone |
| Namedfor: | Plattin Creek, Jefferson County, Missouri |
| Namedby: | Edward Oscar Ulrich[1] |
| Region: | Arkansas, Illinois, Missouri |
| Country: | United States |
| Unitof: | Black River Group |
| Underlies: | Kimmswick Limestone, Kope Formation, Lexington Limestone, and Trenton Limestone |
| Overlies: | Joachim Dolomite and Pecatonica Formation |
| Thickness: | up to 250 feet in Arkansas[2] |
The Plattin Limestone is a Middle Ordovician geologic formation in Arkansas, Illinois, and Missouri.[2] The name was first introduced in 1904 by Edward Oscar Ulrich in his study of the geology of Missouri.[1] A type locality was designated at the mouth of the Plattin Creek in Jefferson County, Missouri, however a stratotype was not assigned. As of 2017, a reference section has not been designated. The name was introduced into Arkansas in 1927, replacing part of the, now abandoned, Izard Limestone.[3]