BRITTLE FAULTING IN LANDRUM, SALUDA, AND TIGERVILLE 7.5-MINUTE QUADRANGLES, INNER PIEDMONT OF SOUTH CAROLINA

Inner Piedmont mapping in upstate South Carolina has focused traditionally on compressive structures. Recent 1:24,000-scale mapping in Landrum, Saluda, and Tigerville quadrangles, however, shows a complex pattern of siliceous cataclastic rocks (SCR) and younger brittle faults affecting amphibolite-grade metamorphic rocks of the Walhalla nappe (WN) and the Six Mile thrust sheet (SM). The faults and associated SCR strike NW, N, NE, and E. SCR indicate the proximity of younger faulting; damage zones and slickenlines related to younger faulting deform the SCR bodies. WN and SM rocks, and the intervening ductile Seneca thrust, are repeatedly offset by a dominant set of N60°-75°E faults; both oblique, left- and right-lateral offsets are produced by that fault set. Zones of right-stepping SCR bodies occur along the Pax Moutain fault. Another prominent N70°E zone of SCR with associated syntaxial veins defines the Cross Plains fault that extends southwestward from Landrum into Slater quadrangle. Sets of N10°-45°W faults, E-striking faults, and SCR are consistently offset or terminated by NE-striking faults. North-striking faults (N5°-20°W) are confined to the SM in Landrum quadrangle. Normal faults are not commonly mapped in the Inner Piedmont. The regional NW-striking faults, however, display a dominant component of down-to-the-east normal-oblique movement. The NW-trending Alexander Creek graben in Landrum quadrangle and the Vaughn Creek graben in Saluda quadrangle are bound by such normal faults. The latter graben previously was interpreted in the Tryon, N. C. area as a window through the SM, exposing younger rocks beneath (Davis, 1993 CGS Guidebook). The Hogback Mountain and Hooker Ridge faults truncate the WN, forming its eastern structural margin. SM rocks crop out across these down-to-the-east faults; the WN is not present at the surface farther east in the Inner Piedmont.