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Allegheny Formation and Pottsville Formation

Allegheny Formation - Interbedded sandstone, siltstone, claystone, shale, and coal beds; Upper Freeport coal at top; where present, Brookville coal defines base; thickness 275 feet in northeast, increases to 325 feet in south and west. And Pottsville Formation - Interbedded sandstone, siltstone, claystone, shale, and coal beds; conglomeratic orthoquartzite and protoquartzite at base; thickness 60 feet in northeast, increases to 440 feet in southwest
StateMaryland
NameAllegheny Formation and Pottsville Formation
Geologic agePennsylvanian
Original map labelPap
Primary rock typesandstone
Secondary rock typeshale
Other rock typesclaystone; siltstone; coal; limestone
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone
Sedimentary > Clastic > Mudstone > Shale
Minor
Sedimentary > Clastic > Siltstone
Sedimentary > Clastic > Mudstone > Claystone
Incidental
Sedimentary > Coal
Map references
Cleaves, E.T., Edwards, J., Jr., Glaser, J.D., 1968, Geologic Map of Maryland: Maryland Geological Survey, Baltimore, Maryland, scale 1:250,000.
Unit references
Cleaves, E.T., Edwards, J., Jr., Glaser, J.D., 1968, Geologic Map of Maryland: Maryland Geological Survey, Baltimore, Maryland, scale 1:250,000.
Unpublished digital version of the Maryland state geologic map that was digitized by the USGS Water Resources Office in Towson, MD
CountiesGarrett

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