The Casselman Formation is one of three formations in Parks Township. It lies above the Glenshaw Formation, which in turn lies above the Allegheny Formation. The least exposed formations within Parks Township are the Casselman and the Allegheny. N. K. Flint named the Casselman in 1965 for good exposures along the Casselman River valley in Somerset County, Pennsylvania. The formation begins just above the Ames Limestone, which caps the underlying Glenshaw Formation.

The Casselman is Late Pennsylvanian in age. Because the Glenshaw ends about 303.7 million years ago (Perera and Stigall, 2018), the Casselman begins at roughly the start of the Gzhelian Stage, the Virgilian in North American terms.

Rock layers of Parks Township Simplified stratigraphic column, youngest at the top: Monongahela Group, Casselman Formation, Glenshaw Formation with the Ames, Woods Run, Pine Creek and Brush Creek limestones, Allegheny Formation, and Pottsville Formation. Not to scale. ▲ younger Monongahela Group Pittsburgh coal Casselman Formation Casselman Fm. ◀ You are here Glenshaw Formation Glenshaw Fm. ◀ You are here Woods Run limestone Pine Creek Limestone Pine Creek Limestone ◀ here Brush Creek Limestone Brush Creek Limestone ◀ here Ames Limestone Ames Limestone ◀ here Upper Freeport coal Allegheny Formation Allegheny Fm. ◀ You are here Brookville coal Pottsville Fm. Conemaugh Group Late Pennsylvanian Middle Pennsylvanian ▼ older · not to scale
Rock layers of Parks Township, simplified and not to scale. Select a layer to read more.

Casselman Fossils

One of the most important discoveries in the formation is Fedexia striegeli, an early amphibian whose skull was found in 2004 on FedEx property near Pittsburgh International Airport in Moon Township (Berman et al., 2010). I have not yet found any fossils in 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 of the formation are still useful, because the Ames Limestone lies directly beneath its base. That limestone is very fossil rich and 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 lower part of the formation includes the Birmingham shale and the Morgantown sandstone; the Connellsville sandstone lies higher, beneath the Pittsburgh limestones. Limestone occurs often, with layers named the Duquesne, Clarksburg, and Lower and Upper Pittsburgh limestones. The formation ends at the base of the Pittsburgh Coal, the first layer of the overlying Pittsburgh Formation in the Monongahela Group.

Cross-section of Parks Township geology across about two and a half miles, showing the Pottsville, Allegheny and Glenshaw formations, with small patches of the Casselman Formation capping the highest hilltops above the Ames Limestone; elevations from about 750 to 1,200 feet, with the Kiskiminetas River at the left
Generalized Formation illustration by J. Harper in 2019. This shows the relative extent of the formation within Parks Township.

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.

Casselman Formation in Parks Township
The Casselman Formation within Parks Township

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.

More Online about the Casselman Formation

References

Cross-section of Parks Township

Cross-section of the rock layers under Parks Township Simplified geologic cross-section about two and a half miles long, after J. A. Harper (2019). From the bottom up: Pottsville Formation, Brookville coal, Allegheny Formation, Upper Freeport coal, Glenshaw Formation with the Brush Creek, Pine Creek, Woods Run and Ames limestones, and the Casselman Formation, which survives only as caps on the highest hilltops. Vertical scale exaggerated about five times. Casselman Formation Glenshaw Formation Allegheny Formation Pine Creek Limestone Brush Creek Limestone Ames Limestone Glenshaw Formation Allegheny Formation Pottsville Formation Casselman Formation Ames Limestone Woods Run limestone Pine Creek Limestone Brush Creek Limestone Upper Freeport coal Brookville coal Kiskiminetas River 1,000 ft 1,200 ft 01 mile After J. A. Harper (2019) · vertical scale exaggerated about 5×
Rock layers beneath Parks Township along a line about two and a half miles long, after J. A. Harper (2019). The Brush Creek, Pine Creek and Woods Run limestones are drawn at their approximate positions within the Glenshaw. Select a layer to read more.