THE SENCA FAULT AND MACROSCOPIC FOLDING IN NORTHERN DACUSVILLE AND WESTERN PARIS MOUNTAIN 7.5-MINUTE QUADRANGLES, GREENVILLE AND PICKENS COUNTIES, SOUTH CAROLINA

Detailed geologic mapping at 1:24,000 scale has been carried out in northern Dacusville and adjacent western Paris Mountain 7.5-minute quadrangles of the Inner Piedmont. The significant structural feature is the Seneca fault, which marks the base of the Six Mile allochthon. This fault was not recognized previously in Paris Mountain quadrangle (Niewendorp and others, 1997). Rocks in the hanging wall of the thrust are interlayered migmatitic muscovite-biotite gneiss, schist, sillimanite schist, and amphibolite/ hornblende gneiss. Footwall rocks include fine biotite gneiss, coarse leucocratic biotite granitoid gneiss, and biotite augen gneiss. The sinuous main trace of the Seneca fault (~N45°E, dipping gently SE) can be followed from southern Slater quadrangle, through Travelers Rest, SC, into southern Dacusville quadrangle. Several klippen of the Six Mile, up to 1 x 4 km in aerial extent, lie several kilometers west of the main Seneca fault trace. Preservation of the klippen is due to ~N20°E- striking downwarping of the fault’s surface after Seneca emplacement, based on: 1) the nature of the fault contact in relation to topography; 2) cross sections constructed through both quadrangles; and 3) similarity to the trend and dimensions of klippen mapped in the Cleveland quadrangle to the north. Two sets of foliations are identified in the klippen, which correspond to major fold phases before and after Senca fault emplacement.

Northwest-striking hanging wall foliation attitudes in the main Six Mile allochthon and in outlying klippen of the map area lie along the northwest limb of the regional Stratford Forest antiform (plunges ~ 34°/N66°E in Paris Mountain quadrangle). Our interpretation is that the Stratford Forest antiform pre-dates transport on the Seneca fault. It may be the same fold phase as the Taylors synform (19°/N78°E) in Taylors quadrangle (Maclean and Blackwell, 2001). The north-northeast striking, post-Seneca warping affecting rocks of the klippen also produced the Greer antiform (31°/N13°E) in Six Mile rocks of Greer quadrangle (Maybin, 1998). A fold-thrust –fold chronology is thereby suggested, based on macroscopic regional map patterns.