AN ALLEGHANIAN (?) BRITTLE THRUST AND ASSOCIATED HINTERLAND-DIRECTED BACK-THRUST SYSTEM IN THE WESTERN INNER PIEDMONT OF SOUTH CAROLINA AND ADJACENT NORTH CAROLINA
Regionally Six Mile thrust sheet rocks lie structurally above Walhalla thrust sheet rocks in the IP. However, associated with the NW-directed Alleghanian thrusting, Walhalla thrust sheet gneisses were back-thrust toward the hinterland over the Six Mile thrust sheet rocks, to the SW, S, and SE. This system of brittle back-thrusts is present in Table Rock, Cleveland, Standingstone Mountain, Zirconia, and Slater quadrangles. Some back-thrusts appear to be localized along or near older greenschist-grade ductile muscovite-quartz shear zone schists and strain-softened zones in Table Rock gneiss produced by earlier gravitational collapse of the IP thrust stack. Back-thrusting deformed Six Mile and Walhalla thrust sheet rocks and locally folded and truncated these older, collapse-related ductile shear zones.
The Slicking Gap normal fault may be related to hanging wall extensional stresses associated with hinterland-directed back-thrusting. Alternately, the normal fault developed, or was reactivated, during later regional Mesozoic SE-ward extension. The Slicking Gap fault is interpreted to be listric and to reactivate the older Alleghanian thrust surface at depth.
*based on NC Geological Survey mapping