Geology of Bedford County, Pennsylvania

Bedford County, Pennsylvania is situated along the western border of the Ridge and Valley physiographic province, which is characterized by folded and faulted sedimentary rocks of early to middle Paleozoic age. The northwestern border of the county is approximately at the Allegheny Front, a geological boundary between the Ridge and Valley Province and the Allegheny Plateau (characterized by relatively flat-lying sedimentary rocks of late Paleozoic age). (PA Geological Survey Map 13)

The stratigraphic record of sedimentary rocks within the county spans from the Cambrian Warrior Formation to the Pennsylvanian Conemaugh Group (in the Broad Top area). No igneous or metamorphic rocks of any kind exist within the county.

The primary mountains within the county (From west to east: Wills, Evitts, Dunning, and Tussey mountains) extend from the southern border with Maryland to the northeast into Blair County, and are held up by the Silurian Tuscarora Formation, made of quartz sandstone and conglomerate. Chestnut Ridge is a broad anticline held up by the Devonian Ridgeley Member of the Old Port Formation, also made of sandstone and conglomerate. Broad Top, located north of Breezewood, is a plateau of relatively flat-lying rocks that are stratigraphically higher, and thus younger (Mississippian and Pennsylvanian), than most of the other rocks within the county (Cambrian through Devonian). Broad Top extends into Huntingdon County to the north and Fulton County to the east.