Stratigraphy Within Lower Pottsville Formation of Alabama
Stewart T. Taylor
Recent studies of the Lower Pennsylvanian Pottsville Formation in the northern Warrior basin of Alabama have led to the correlation of several lithostratigraphic units on the basis of drill and outcrop data. These include the Bear Creek and Polecat coal seams, which extend from northwestern to north-central Alabama. Formal nomenclature is proposed for three widespread units within the basin. The correlated stratigraphic units lie above the Boyles Sandstone Member of the Pottsville Formation, a repetitious series of gray shales, coal, and gray sandstones that resulted from cyclic sedimentation during the Early Pennsylvanian.
Within the study area, the Boyles Sandstone Member is overlain by a thick, gray, siliciclastic sequence ranging progressively from fine-grained shales and coal of interdistributary bay-fill sequences to tightly cemented channel sandstones that contain carbonaceous debris above basal pebble conglomerates. Overlying the bay-fill sequences are poorly cemented fluviodeltaic sandstones that are pink to red and well cemented along the basal contact with the gray shales or gray clay. The unconsolidated to friable sands are exposed below the Cretaceous unconformity in the study area. This succession of lithologies reflects the southward progradation of the Pottsville deltaic complex during the Early Pennsylvanian. During this time, the deltaic system prograded over the underlying East Warrior platform.
AAPG Search and Discovery Article #91031©1988 AAPG Eastern Section, Charleston, West Virginia, 13-16 September 1988.