EXAMINING MULTIPLE SCALES OF PALEOSLOPE INFLUENCES ON THE MISSISSIPPIAN FORT PAYNE FORMATION, KENTUCKY

The Early to Middle Mississippian Borden Formation represents a subaqueous delta wedge that prograded westward across the Appalachian foreland into the Illinois Basin. In Kentucky, mixed carbonates and clastics were deposited west of an abandoned lobe of the Borden delta in the Fort Payne Formation. The juxtaposition of these two units results in a wide variety of marine facies in close proximity along the delta front. Ettensohn and other researchers examined the stratigraphic relationships between units as an early relaxational response to the Neoacadian orogeny. Aside from far-flung tectonic influences, the units were strongly influenced by paleotopography and paleoslope at a variety of scales. Fort Payne mud mounds are sometimes deposited on top of and onlap paleotopographic highs on the basin floor west of the abandoned Borden delta lobe. Off-slope and bottom currents and possibly structural influences influenced paleotopography and the sites for mud-mound initiation. Mounds began with concentrations of fenestrate bryzoa trapping clastic sediments, followed by carbonate buildup. The Borden front exhibits large-scale rotational slumps. Slumps and mass flows on the Borden delta front were undoubtedly the source for turbidity current and turbidite submarine fan deposits, which occur between Fort Payne mounds. Many mounds have elliptical outlines with long axes parallel to the Borden front and steeper faces towards the front, suggesting that currents along the Borden front influenced mound geometry. Submarine channels with a variety of mass flow deposits occur between some mounds. Soft-sediment deformation, and slumping is also common on some mound flanks. The variety and geometry of sedimentary deposits within the Fort Payne mound interval suggests that mound initiation may have been initiated by large-scale paleoslope influences, but once mounds began to accrete, the paleotopography created by the mounds themselves strongly influenced sedimentation.