Geology
The bedrock at the park consists of the Devonian Brallier Formation, Harrell Formation, Mahantango Formation, and Marcellus Formation. These formations are all dominantly shales and siltstones, which dip to the southeast at approximately 20-30 degrees. The park lies at the southern end of Chestnut Ridge, which is a broad, doubly plunging anticline. Some of the shales (probably the Harrell Formation) outcrop along the shores of the lake, particularly the southern shore near the dam.
Read more about this topic: Shawnee State Park (Pennsylvania)