North Park & Its Geology: Location 4

The Duquesne Coal layer represents
another interval of cool and wet
climatic conditions that was caused
by the advance of polar glaciers. 
Farther to the west in Pennsylvania,
this coal is overlain by marine shale
similar to the Ames Limestone. In
the Pittsburgh area this fossiliferous
layer is called the Birmingham Shale,
but in Ohio it is called the Skelly

North Park Geology: Location 4 Chart