SEAFLOOR TOPOGRAPHY AND DEPOSITIONAL COMPLEXITY RECORDED IN THE MISSISSIPPIAN FORT PAYNE FORMATION OF SOUTH-CENTRAL KENTUCKY

The Fort Payne Formation, exposed in Cumberland County, Kentucky, is a marine unit deposited in the epeiric sea of the North American mid-continent during Osagean time. This unit is heterogeneous, consisting of both carbonates and siliciclastics. These rocks previously have been interpreted either as entirely transported, or as a complex mixture of turbidites, small-scale debrites, reworked debrites, and in situ carbonate mounds.

The depositional history of the Fort Payne Fm. in southern Kentucky has been interpreted using architectural element analysis of a 600 m-long outcrop along Kentucky Hwy 61 south of Burkesville. Thirteen depositional elements were identified on photomosaics of the outcrop. Channelform elements at the N end dip to the S, while the channelform elements at the S end dip to the N. All channelform elements lie below ground in the middle of the outcrop, but share enough lithologic characteristics to support correlating them. Element 3 (at the N end) and Element BB (at the S end) are dominated by thin-bedded packstones and subordinate shales, with abundant wavy, lenticular and flaser bedding. Element 2 (at the N end) and Element BA (at the S end) are dominated by shales, and also contain wavy, lenticular and flaser bedding. Correlating these pairs of elements suggests that they form the flanks of a channel ~595 m wide, with relief of at least 15 m.

Conditions varied during deposition at the Hwy 61 locality, with intervening episodes of minor erosion that helped define the individual elements. Depositional processes included turbidity currents and small-scale debris flows, with varying amounts of reworking superimposed. All of these processes operated episodically against a background of silt deposition via suspension fallout and/or dilute bottom flows.