This rock is a slope-former adjacent to (and stratigraphically below) the prominent ridge-forming Bald Eagle sandstone unit in the Appalachian Mountains.
The Reedsville Formation is an olive-gray to dark-gray siltstone, shale, and fine-grained sandstone.
[4] In Central Pennsylvania along the Nittany Arch, and extending into the subsurface of northern West Virginia, the base of the Reedsville formation includes the black calcareous Antes Shale formation.
[6] Isotopic dating of shale mylonite in Pennsylvania reveals a K-Ar age of 372+/-8 Ma.
[7] The Reedsville is quarried locally in borrow pits for road material and fill.