Powell Formation

Powell Formation Stratigraphic range: Ordovician
Type	Formation
Underlies	Everton Formation
Overlies	Cotter Formation
Lithology
Primary	Dolostone
Other	Shale, sandstone, chert
Location
Region	Arkansas, Missouri and Virginia
Country	United States

The Powell Formation or Powell Dolomite is a geologic formation in northern Arkansas, southeast Missouri and Virginia. It contains gastropod, cephalopod, and trilobite fossils dating back to the Ordovician Period.

...
Wikipedia