The Casselman Formation is one of 3 formations in Parks Township. It lies above the Glenshaw Formation and the Allegheny Formation. The least exposed formations within Parks Township are the Casselman and the Allegheny Formation. The Ames Limestone is the bottom most layer within the Casselman.
Among one of the most important discoveries within the formation is Fedexia striegeli. For my purposes, I have not yet found any fossils within the Casselman locally. The formation typically lies at the hilltops and often under layers of soil and clay. I have yet to find an exposed outcrop of rock from the formation within Parks Township. Maps with the formation are important, however, as the base contains the Ames Limestone. This layer within the strata is very fossil rich. It is an excellent target when searching for a place to explore.
Layers within the Casselman
The formation contains many named layers, including the Duquesne, Wellersburg and Clarksburg coals. The Birmingham, Morgantown and Connellsville sandstones make up a large portion of the oldest part of the formation. Limestone occurs often, with layers appearing and named as the Duquesne, Clarksburg, Lower and Upper Pittsburgh Limestones. The entire formation is capped by a layer named the Pittsburgh Coal. Above the Casselman you will find the Pittsburgh Formation contained within the Monongahela Group.
The Formation within Parks Township
The formation covers much less than 30% of the land in Parks Township, estimated using the map below. It occurs only at the highest hilltops locally.
The Casselman Formation in Pennsylvania
The following Google Map shows the formation as it lies in Pennsylvania. To produce this map, I used shape files provided by the state of Pennsylvania.