TRANSFER FAULTS OF THE SOUTH GEORGIA RIFT

Subsurface mapping of the South Georgia Rift (SGR), a buried Triassic rift system, reveals a series of sub-basins which reverse polarity across northwest striking transfer faults. Two of these transfer faults project along strike of oceanic fracture zones, suggesting they are related. Transfer fault extensions of oceanic fracture zones have been hypothesized to be present through the SGR by previous workers (Tauvers and Muehlberger, 1987; Salvador, 1987; Etheridge et al., 1990); however, this is the first study to document a reversal in sub-basin polarity, thus confirming their existence. Reversals in polarity are observed as abrupt reversals in dip of seismic reflections, such as at VP 490 on COCORP GA-19, and also are indicated by reversals in dip of basin bounding normal faults constrained by well and geophysical data. A transfer fault in Georgia, which corresponds with the Jacksonville fracture zone, appears to offset the Brunswick anomaly (Tauvers and Muehlberger, 1987) and marks a distinct change in the SGR structure. Southwest of this fault, the SGR has a much wider aerial extent and is structurally complex (McBride, 1991), while to the northeast the SGR appears to exhibit an asymmetric half-graben style. In South Carolina, a transfer fault which projects toward the Blake Spur fracture zone bounds the Dunbarton sub-basin to the northeast and runs through the southwest edge of the Charleston seismic zone. Additional transfer faults are inferred from the rift geometry where the rift extent changes abruptly. Although the SGR overlies the Gondwana-Laurentia suture, it ultimately failed to open into an ocean; and yet some SGR transfer faults correspond with Atlantic Ocean fracture zones. The coincidence of these continental and oceanic features illustrates the importance of structural inheritance of transfer faults on the development of a passive margin (Thomas, 2005). The close correspondence of the Blake Spur transfer fault to the Charleston seismic zone further indicates that these lithospheric-scale planes of weakness provide a framework for Cenozoic intra-plate tectonics.