The Lower Youghiogheny basin (130 sq mi or 338 sq km) ranks fourth in total area of the five synclinal coal basins of western Maryland. Approximately 1,000 ft (305 m) of coal-bearing strata of Early to Late Pennsylvanian is exposed (Pottsville, Allegheny, and Conemaugh Formations). The Pottsville Formation rests unconformably on the Mauch Chunk Formation of Late Mississippian. The contact separating the Pottsville and Allegheny Formations is the top of the Homewood Sandstone, and that separating the Allegheny and Conemaugh Formations is the top of the Upper Freeport coal bed. A coal bed correlated with the Little Clarksburg, which occurs in the upper third of the Conemaugh formation in West Virginia, is

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stratigraphically the highest coal bed in the section; the uppermost part of the Conemaugh is not present. Structurally, the basin in Maryland is the southern termination of the Youghiogheny syncline, which is asymmetrical and plunges to the northeast.

The coal beds of the basin were traced using new data from surface mines, water well logs, a mine-drainage pollution study, recent aerial photographs (May 1979), and unpublished data from the Maryland Geological Survey. Field checking, where possible, substantiated the available data. Two marine intervals, the Ames and the Brush Creek shale, aided in the correlation of the coal beds. A structure contour map of the top of the Upper Freeport coal bed was used to project the outcrop patterns of coal beds onto a topographic map.

Fourteen coal beds were identified in the Lower Youghiogheny basin. Of these, five are minable or potentially minable, the Upper Freeport and the Lower Kittanning being the more important. On the basis of this study, the Barton and Clarion coal beds are newly recognized in the basin. The Clarion coal bed has been mined in conjunction with the Lower Kittanning coal bed and knowledge of its existence adds a significant tonnage to calculated coal resources of the basin. A revised stratigraphic column for the basin shows the stratigraphic position of the Barton and Clarion coal beds. A map showing the coal beds indicates minable and potentially minable areas in the basin.

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