Polk Creek Shale
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| Polk Creek Shale | |
|---|---|
| Stratigraphic range: Ordovician | |
| Type | Formation |
| Unit of | none |
| Sub-units | none |
| Underlies | Blaylock Sandstone |
| Overlies | Bigfork Chert |
| Thickness | 50 to 225 feet[1] |
| Lithology | |
| Primary | Shale |
| Location | |
| Region | Arkansas, Oklahoma |
| Country | United States |
| Type section | |
| Named for | Polk Creek, Montgomery County, Arkansas |
| Named by | Albert Homer Purdue[2] |
The Polk Creek Shale is a Late Ordovician geologic formation in the Ouachita Mountains of Arkansas and Oklahoma. First described in 1892,[3] this unit was not named until 1909 by Albert Homer Purdue in his study of the Ouachita Mountains of Arkansas.[2] Purdue assigned Polk Creek in Montgomery County, Arkansas as the type locality, but did not designate a stratotype. As of 2017, a reference section for this unit has yet to be designated.
