SHALLOW SEISMIC PROFILING OF THE CAMDEN FAULT, SOUTH CAROLINA COASTAL PLAIN

New geophysical data, collected as part of a course in reflection seismology at USC during the Fall 2000 semester, provide evidence for an ~30 m (80-100') offset in the basal contact of Coastal Plain sediments across the Camden Fault in north-central South Carolina. These new data include a high-resolution (800 Hz), shallow (500 ms) 2-D seismic reflection profile (~120 m or 720' long) and coincident 2-D gravity survey, acquired northwest of Camden, South Carolina, where the Camden Fault constitutes part of the Fall Line. The Camden Fault was previously mapped along strike for more than 25 km as a NE-trending fault of Paleozoic age separating distinct basement terranes of the Carolina Piedmont. Evidence for Cenozoic reactivation of this fault was based on offset of Upper Cretaceous sands of the Coastal Plain, with an apparent throw of southeast side down. The new seismic data show evidence for an abrupt northwestward shallowing to the surface of a prominent subhorizontal reflector at ~50 ms (~30 m), which is interpreted as the contact between Coastal Plain sediments and underlying crystalline basement. At least at the location of the profile, the Camden fault consists of a zone of faulting some 25-30 m thick, probably involving several fault strands, rather than a single discrete fault surface. A subtle but recognizable gradient can also be recognized in coincident gravity data along the mapped trace of the Camden Fault. At present, the dip of the high-angle fault zone cannot be discerned from the data. As such, two possible models for the fault geometry can be entertained: (1) a northwest-dipping reverse fault, and (2) a southeast-dipping high-angle normal fault that has been reactivated in Cenozoic time as a reverse fault. Projection of the fault zone to the southwest suggests that the Camden fault is covered by deposits of the Tertiary Upland Conglomerate, providing a potential upper age limit on the Cenozoic movement of the fault.