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Allegheny Formation facts for kids

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Allegheny Formation
Stratigraphic range: Pennsylvanian
Type Sedimentary
Underlies Conemaugh Group
Overlies Kanawha Formation and Pottsville Formation
Primary Sandstone, coal
Region Appalachian Mountains
Country United States
Extent Pennsylvania, Maryland, West Virginia, Ohio
Type section
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.

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