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

Potential-field data, with its excellent spatial coverage, used in combination with seismic imaging, can illuminate basement and upper- to mid-crustal structures, especially igneous rock bodies associated with the Alleghanian orogeny and features attributed to subsequent continental rifting. The nature of the metamorphic and igneous basement rocks underlying coastal-plain sediments along the southern portion of the Eastern North American passive margin is poorly constrained and represents a major EarthScope target. These 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 two-dimensional cross-section models, constrained by deep-well and seismic data, have been developed for the basement beneath the South Carolina Coastal Plain by forward and inverse modeling of the aeromagnetic and gravity fields. Exploratory data analysis and quality assessment is being performed on potential field data, and a database of rock properties has been compiled. Prior to inversion of the non-unique potential-field data, two-dimensional density/magnetic forward models are being developed with deep-well, seismic reflection and refraction data control, to better constrain inverse models.

Three crustal profiles traverse the Piedmont and South Georgia rift basin, where interpretation is constrained by 74 wells to basement, as well as 21 two-dimensional seismic reflection lines. The profiles coincide with SUGAR seismic refraction lines, and are ideally situated to cross major regional tectonic and geologic elements, including the Carolina Terrane, Sewanee Suture, Brunswick Magnetic Anomaly, Triassic rift basins, and the Central Atlantic Magmatic Province (CAMP). This work will allow estimation of rock volumes, areal extent, and depth of CAMP mafic sills and dikes. Basement maps and profiles will also assist assessment of potential for CO² sequestration and geothermal-power generation.