DEPOSITIONAL ARCHITECTURE AND PROCESSES OF THE FORT PAYNE FORMATION, SOUTH-CENTRAL KENTUCKY

The Fort Payne Formation (Lower Mississippian), exposed in Cumberland County, Kentucky, is a marine unit deposited within the epeiric sea that dominated the mid-continent of North America during Osagean time. The unit is heterogenous, consisting of both carbonates and siliciclastics, and both autochthonous and allochthonous facies. One depositional model of the Fort Payne Formation interprets the various facies as having distinctly different origins, including turbidites, debrites, reworked debrites and in situ carbonate mounds.

In order to interpret the depositional history of the Fort Payne Formation in southern Kentucky, architectural element analysis has been applied to outcrops along Highway 61 south of Burkesville, at Lake Cumberland and along State Route 90. Three types of elements have been preliminarily identified: sandy tabular geometries that are tens of meters in length and height, muddy tabular beds that are tens to hundreds of meters in length and tens of meters in height and lenticular beds that range from 10-20 m across and 5-10 m high to hundreds of meters across and tens of meters high.

Preliminary examination in the field suggests that abundance, orientation and distribution of larger grains within beds will place important constraints on interpreting depositional processes. The orientation and distribution of larger grains, such as crinoid columnals, are vital data for interpreting whether the sediment was deposited by high viscosity flow or low viscosity flow. Beds with randomly oriented grains and a matrix-supported fabric are attributed to high viscosity flows; whereas beds with relatively uniform orientation of grains and a grain-supported fabric are a product of low viscosity flows.