Depositional Systems in the Lower Part of the Pottsville Formation, Black Warrior Basin, Alabama

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Three depositional systems have been defined and named within the lower Pottsville Formation in the subsurface in Alabama: (1) the Fayette-Walker barrier system, (2) the Lamar marsh-lagoon system, and (3) the Pickens-Tuscaloosa delta system. These three distinctly different depositional systems were defined on the basis of data from electric logs, sandstone isolith maps, coal distribution, and core descriptions. The Fayett-Walker barrier system is composed of a thick section of northwest-southeast trending orthoquartzitic sandstones containing thin interbeds of mudstone and rare coal beds, and extends throughout the eastern part of the study area. The Lamar marsh-lagoon system is copmosed mostly of mudstone containing few, discontinuous sandstone bodies and extends westward from the Fayette-Walker barrier system. The Pickens-Tuscaloosa delta system extends southward from the southern limit of the Fayette-Walker barrier system and the Lamar marsh-lagoon. Sparse data from the Pickens-Tuscaloosa delta system suggest a northeast-southwest-trending sandstone interbedded with mudstone and coal.