Casselman Formation

The Casselman Formation mapped sedimentary bedrock unit in Pennsylvania, Maryland, and West Virginia, of Pennsylvanian age. It is the uppermost of two formations in the Conemaugh Group, the lower being the Glenshaw Formation. The boundary between these two units is the top of the marine Ames Limestone.^[2] The Conemaugh Group overlies the Upper Freeport coal bed of the Allegheny Formation and underlies the Pittsburgh coal seam of the Monongahela Group.

Casselman Formation
Stratigraphic range: Pennsylvanian
Outcrop of Casselman Formation at Mile Marker 84.2, Pennsylvania Turnpike
Type	sedimentary
Unit of	Conemaugh Group
Underlies	Monongahela Group
Overlies	Glenshaw Formation
Lithology
Primary	shale, siltstone, sandstone, red beds, coal
Other	limestone
Location
Region	Appalachian Plateau
Country	United States
Extent	Ohio, Pennsylvania, Maryland, West Virginia
Type section
Named for	Casselman River
Named by	N. K. Flint, 1965[1]

Overview

The Conemaugh Group consists of cyclic sequences of shale, siltstone, sandstone, red beds, thin impure limestone, and thin nonpersistent coal. Red beds are associated with landslides.^[3]

The thickness of the Conemaugh Group averages about 400 feet in Ohio, and it ranges from 450 feet on the Ohio River in West Virginia to 520 feet in Washington County, Pennsylvania, and then to 890 feet in Somerset County, Pennsylvania.^[4]

Fedexia remains are among the fossils that have been recovered from the formation.^[5]