IMAGING GRANITES, OTHER PLUTONS AND FAULTS ASSOCIATED WITH CONTINENTAL COLLISION AND RIFTING USING POTENTIAL-FIELD, SEISMIC, AND WELL DATA, SOUTH CAROLINA

Aeromagnetic data, with its excellent spatial coverage of the eastern North American margin, used in combination with seismic imaging can help to illuminate basement and upper- to mid-crustal structures, especially igneous rock bodies associated with Paleozoic orogenesis and features attributed to early Mesozoic continental rifting. The nature of basement structures and bedrock geology in the Appalachian Piedmont and beneath the Atlantic Coastal Plain is poorly constrained. These metamorphic and igneous basement rocks record the large-scale geologic processes responsible for the evolution of continental lithosphere spanning a Wilson cycle, including continental assembly, mountain building, continental rifting, and post-rift passive margin evolution. In order to better characterize these rocks, maps and 2D cross-section models (constrained by seismic, borehole, and outcrop data) are being developed for South Carolina by forward and inverse modeling of the aeromagnetic and gravity fields. A quality assessment of potential-field data has been performed, and a database of rock properties, including densities and magnetic susceptibilities has been compiled from publications and ongoing lab analyses.

Five new crustal profiles, including a mountains-to-sea profile, traverse the central Piedmont suture, the eastern Piedmont fault system, and South Georgia rift basin, where interpretation is constrained by 74 wells to basement, as well as 28 2D seismic-reflection lines, and two seismic refraction surveys. The profiles cross major regional tectonic and geologic elements, including Paleozoic faults, granites, and gabbros, as well as Mesozoic rift basins and associated CAMP mafics. High densities and magnetic susceptibility contrasts allow estimation of areal extents, rock volume, and depth of major basement features. The aeromagnetic field is particularly useful for delineating terrane boundaries, structure in Piedmont metamorphic rocks, granite-Piedmont intrusive contacts, and CAMP mafic conduit and pluton geometries. Data products will also assist assessments of the potential for CO₂ sequestration and low-temperature geothermal energy.