REVISED GEOLOGIC MAP OF NORTHEASTERN TABLE ROCK QUADRANGLE, GREENVILLE AND PICKENS COUNTIES, SOUTH CAROLINA

Published geologic maps are a representation of the geology known at a point in time – a progress report to be updated as required or as additional data become available. We remapped 14 km² in northeast Table Rock quadrangle, between Caesars Head State Park and Lakemont, SC in Greenville and Pickens Counties. GPS-based field mapping and selective petrographic analysis of subdivided metamorphic map units allowed tracing of contacts and delineation of detailed structures that were unrecognized in the 2003 geologic map. Map units of the Six Mile thrust sheet include Poor Mountain Formation (amphibolite, quartzite, and mica gneisses), Tallulah Falls gneiss and Tallulah Falls schist (informal map units), and Table Rock gneiss (Walhalla thrust sheet). The ductile Seneca thrust lies between the Six Mile and Walhalla thrust sheets. It is affected by later deformation.

A chronology of events has been determined in the study area. An early structural event involved development of NW-trending, upright-inclined folds in the Six Mile thrust sheet and NW-trending, SW-verging, overturned folds affecting the previously emplaced Seneca fault and adjacent rocks. Earlier NE-trending, NW-vergent structures known elsewhere regionally are absent. Left-reverse oblique movement along the Caesars Head thrust at greenschist grade conditions placed Table Rock gneiss over the Six Mile thrust sheet south of Caesars Head State Park. Later in the chronology, a complex pattern of brittle faults disrupted earlier fold and ductile thrust structures. Brittle fault sets have E-W, NW, and NNE-NE strikes. Faults striking E-W, including the Palmetto Cove and the newly discovered Lakemont faults, have left normal-oblique offset. These faults locally bound narrow graben structures. They are part of a regional zone of oblique movement faults that eastward intersects regional NE-striking brittle faults. In the study area, the early-formed, SW-verging overturned folds of NW trend appear to have been rotated locally into a more easterly trend where transected by the E-W striking left normal-oblique faults. The Tallulah Falls schist unit commonly shows mesoscale SW-vergent shear sense features. A revised version of the geologic map of Table Rock quadrangle will be available to the public at http://www.dnr.sc.gov/geology/publications.htm#gqm.