The Pennsylvanian Pottsville Formation of the Black Warrior Basin in Alabama comprises as much as 3000m of shale, sandstone and coal. The boundary between the informal units of the Lower Pottsville strata include orthoquartzitic sandstone, shale, and coal interpreted as having been deposited in a barrier/back-barrier setting. Upper Pottsville strata consist of lithic arenite, shale, coal, and minor amounts of orthoquartzite, and are interpreted as representing a lateral gradation from lower delta plain to barrier bar. The change in sedimentation patterns in the middle part of the Pottsville suggests introduction into the basin of sediments from an eastern source.-from Author
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Depositional environments of the Pennsylvanian Pottsville Formation in the Black Warrior basin of Alabama.