Stratigraphic range: Pennsylvanian
|Extent||Pennsylvania, Maryland, West Virginia, Ohio|
|Named by||H. D. Rogers, 1840|
The Pennsylvanian Allegheny Formation is a mapped bedrock unit in western and central Pennsylvania, western Maryland and West Virginia, and southeastern Ohio. It is a major coal-bearing unit in the Appalachian Plateau of the eastern United States.
In Pennsylvania, the Allegheny Formation 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. The formation consists of cyclothemic sequences of coal, shale, limestone, sandstone, and clay. It contains six major coal zones, which, in stratigraphic order, are:
- Upper Freeport Coal
- Lower Freeport Coal
- Upper Kittanning Coal
- Middle Kittanning Coal
- Lower Kittanning Coal
- Brookville Coal
Glen Richey (PA), Laurel Run (PA), Mineral Springs (PA), Millstone Run (PA), Clearfield Creek (PA); Clarion (OH, MD, PA, WV), Kittanning (PA), Freeport (PA, MD, OH, WV); Putnam Hill (OH, PA); Vanport (PA, MD, OH, WV); Butler (MD, PA), Worthington (MD, PA); Washingtonville (OH, PA, WV), Columbiana (OH)
Relative age dating of the Allegheny places it in the middle Pennsylvanian period.
- Rogers, H.D., 1840, Fourth annual report of the Geological Survey of the State of Pennsylvania: Pennsylvania Geological Survey Annual Report, no. 4, 215 p.
- The Geology of Pennsylvania, C. H. Shultz, ed., DCNR Special Publication 1, 1999. (Ch. 10) 
- GEOLEX database, Geologic Unit: Allegheny, retrieved 28 December 2010
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