Structural and stratigraphic investigations of the Bays Mountain synclinorium, Parrottsville and a portion of Cedar Creek 7.5-minute quadrangles, East Tennessee

by 1980- Whitmer, Neil Eric

The southern Valley and Ridge foreland fold-thrust belt is comprised of a wedge of Lower Cambrian through Pennsylvanian sedimentary rocks that were folded and faulted during the late stages of the Alleghanian orogeny. Within one of the eastern thrust sheets lies the Bays Mountain synclinorium. Rocks as young as Middle Ordovician are preserved in the core of the synclinorium and record the evolution of a Taconian (Blountian) Sevier tectonic basin. The Parrottsville and Cedar Creek 7.5-minute quadrangles are located on the southeastern flank of the Bays Mountain synclinorium of East Tennessee and contain rocks belonging to the Conasauga, Knox, and Chickamauga Groups. In the southeastern part of this region, the Pulaski thrust sheet overrode the Sevier basin and exposes rock as old as Middle Cambrian along its trace. Post-emplacement folding of the Pulaski fault created a sinuous fault trace that juxtaposes the southeastern and northwestern phases of the Knox and Conasauga Groups. Until recently, Sevier basin rocks in the Parrottsville and Cedar Creek 7.5-minute quadrangles have been divided into two units: Lenoir Limestone and Sevier Shale. Previous studies concluded divisions proposed elsewhere for the Sevier basin sediment were not applicable in the vicinity. Geologic mapping during this study, however, has identified one subdivision that has been traced along and across strike some 50 km to the northeast. The conventional model for Sevier basin formation has been that of a foredeep basin that formed in response to crustal loading during the Taconic orogeny. Petrologic iv analyses of Sevier basin sedimentary rocks combined with recent detrital zircon data indicate new tectonic models for the basin need consideration. Unit thicknesses acquired in this study suggest a recently proposed back-bulge model that requires a peripheral bulge preventing sediment from the interior of the mountain belt from reaching the Sevier basin to be rheologically infeasible. Rather, data supports a complex development basin model in which basement thrusting sufficient to isolate the Sevier basin from potential sediment sources in the interior portion of the mountain belt occurred during its development. v