A COMPARATIVE PROVENANCE STUDY OF THE LOWER PENNSYLVANIAN POTTSVILLE FORMATION FROM THE NORTHERN APPALACHIAN BASIN IN PENNSYLVANIA AND THE GREATER BLACK WARRIOR BASIN IN ALABAMA

The lower Pennsylvanian Pottsville Formation is found from Northern Appalachian basin in Pennsylvania to the Greater Black Warrior basin (GBWb) in Alabama & Mississippi. These syn-Alleghanian clastic wedges of siliciclastic sediments are characterized predominantly by interbedded sandstone, siltstone, conglomerate, conglomeratic sandstone, shale, limestone, and coal beds. The formation was deposited mainly in two locations in Pennsylvania; at the western Bituminous field (20-250 feet) and the eastern Anthracite field (100-1600 feet). In the southern Appalachians, the Pottsville Formation however is deposited in three sub-basins of the GBWb (i.e. the Black Warrior basin, the Cahaba basin and the Coosa basin) where the thickness of the formation is around 8000 feet in the central part of the basin. The higher thickness of the Pottsville may be due to greater syntectonic subsidence at the southern Appalachian.

The composition of Pottsville sandstones varies from western bituminous field to eastern anthracite field of Pennsylvania. The sandstones from western Bituminous field are compositionally more mature than the eastern Anthracite field. The Pottsville sandstones are dominated by litharenite in Anthracite field and quartz arenite in the Bituminous field of Pennsylvania. Compositions of these sandstone suites (Qt₇₀F₃L₂₇ in Bituminous field and Qt₅₅F₅L₄₀ in Anthracite field) reflect a recycled orogenic provenance, which resemble closely with the composition of the Pottsville sandstones (Qt₆₀F₇L₃₃) from the GBWb in Alabama. The compositionally immature sandstones from eastern Anthracite field and the GBWb indicate that they were deposited by deltaic systems that drained from the nearby Appalachians. The relatively mature sandstones in the western Bituminous field reflect the influence of mixed source areas, i.e., the Canadian cratonic area in the north as well as the Appalachians in the east. The presence of heavy minerals including garnets and rutile in both northern Appalachian basin and the GBWb suggests deeper level exhumation of the Appalachian orogenic belts for the Pottsville sandstones. Ongoing work on garnet geochemistry using electron microprobe and ⁴⁰Ar/³⁹Ar analysis on detrital muscovites will provide more information on the provenance history of the Appalachian foreland basins.