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Rocks that characterize this region include: limestone, dolomite, slate, shale, sandstone, siltstone, and some scattered basalt. Almost all of the rocks in the Great Valley in Pennsylvania are Ordovician in age and were deposited during a quiet period before the Taconic orogeny. The limestones and dolomites of this area are extensively quarried ...
The following is a list of the mapped bedrock units in Pennsylvania. The rocks are listed in stratigraphic order. [1] System Group name Formation name Member name
The Devonian Catskill Group or the Catskill Clastic wedge is a unit of mostly terrestrial sedimentary rock found in Pennsylvania and New York. Minor marine layers exist in this thick rock unit (up to 10,000 feet (3,000 m)). It is equivalent to the Hampshire Formation of Maryland, West Virginia, and Virginia.
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.
Shaped rock piles on boulders at the Oley Hills site Large shaped rock pile at the Oley Hills site Cairn or rock pile at the Oley Hills site: sometimes said to resemble a turtle The Oley Hills site , or Oley Hills stone work site , located in Berks County, Pennsylvania , is an enigmatic complex of snaking dry stone walls, carefully shaped rock ...
Rock formations of Pennsylvania (2 P) V. Valleys of Pennsylvania (6 C, 23 P) W. Waterfalls of Pennsylvania (1 C, 8 P) Wetlands of Pennsylvania (1 C, 4 P)
The fine-grained rocks represent a shallow sea environment and accounts for many of the fossils. Coarser grained sediments represent near-shore environments, beaches, or possibly delta lobes. These environments were tide-dominated and often had violent storms. The Montebello Sandstone member is an example of a storm dominated rock unit.
In Pennsylvania, the Allegheny Group includes rocks from the base of the Brooksville Coal to the top of the Upper Freeport Coal, and was defined to include all economically significant coals in the upper Pennsylvanian sequence. [4] The unit consists of cyclothemic sequences of coal, shale, limestone, sandstone, and clay.