DEFORMATION OF THE SALTVILLE THRUST SHEET, VALLEY AND RIDGE, EAST TENNESSEE

The Saltville (SV) fault is a major fault in the southern Appalachian Valley and Ridge, extending from southwest of the central-southern Appalachian transition at Roanoke, Virginia south through east Tennessee, becoming the Rome fault in northeast Georgia, and the Helena fault in Alabama. Deformation style varies both along and across the SV thrust sheet, and industry and government seismic reflection data shed some light on fault and fold geometry both in and below the sheet in east Tennessee.

Just south of the Virginia-Tennessee border, the overlying Pulaski fault moves east, and the outcrop width of the SV thrust sheet widens. Between the border and Gatlinburg, Tennessee, the sheet contains anticlines most visible in outcrops of Knox Group and older rocks amid a broad expanse of Middle Ordovician Tellico-Sevier basin units. It has been suggested that folds in the SV sheet are the result of duplexing in the underlying Copper Creek thrust sheet, or that they are due to imbricate faulting in the SV sheet as it lies flat-on-flat above the Copper Creek (CC) thrust sheet, which in turn lies above the basal detachment. Seismic reflection data indicate that the CC sheet extends only as far east as the western margin of Tellico-Sevier basin, and that imbricates in the SV sheet instead extend to basement, originating as splays off the basal detachment. Furthermore, where the Copper Creek sheet does lie below the SV sheet, it is not deformed sufficiently to induce folding in the SV above.

South of Gatlinburg, the outcrop width of the sheet narrows, and some imbricates are overridden by older rocks of the Blue Ridge Piedmont (BRP) megathrust sheet forming the Foothills duplex in the footwall of the BRP. Narrowing of the eastern belt of Middle Ordovician rocks correlates with their appearance to the west above a major splay off the SV (Knoxville thrust). This transition is also marked by changes in the geometry of the SV thrust. A small lateral ramp occurs in the footwall where the SV fault steps down from a flat in Mississippian units in the northeast, to a flat in the Middle Ordovician units to the southwest. Farther south, near the Tennessee-Georgia border, the SV fault shallows and the SV sheet is dominated by folding, rather than by faulting. Here, folding occurs as a result of footwall collapse and duplexing in the underlying Beaver Valley sheet.