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, SOUTH CAROLINA
DUFF, Patrick1, KELLOGG, James1, HOWARD, Scott2 and HORTON, J. Wright3, (1)Earth and Ocean Sciences, University of South Carolina, Columbia, SC 29208, (2)S.C. Department of Natural Resources – Geological Survey, 5 Geology Rd, Columbia, SC 29212, (3)U.S. Geological Survey, 926A National Center, Reston, VA 20192, pduff119@aol.com
Potential-field data, with its excellent spatial coverage, used in combination with seismic imaging, can help to 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. 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, are being 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 a quality assessment have been performed on gridded aeromagnetic data and land gravity data. A database of rock properties, including densities and magnetic susceptibilities, is being compiled from publications and ongoing lab analyses. 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 South Georgia and Dunbarton rift basins, where interpretation is constrained by wells to basement, as well as 20 two-dimensional seismic reflection lines, and two seismic refraction surveys. The profiles are ideal because they cross major regional tectonic and geologic elements, including Paleozoic faults, Triassic rift basins, plutons, and mafic dikes, and because high densities and magnetic susceptibilities allow estimation of rock volumes, areal extent, and depth of mafic plutons associated with continental rifting and the Central Atlantic Magmatic Province. The coastal-plain basement maps and profiles will also assist assessment of the potential for CO2 sequestration and geothermal-power generation in and near the rift basins.
