INVESTIGATION OF RIFT BASINS AND UNDERLYING CRUST BENEATH THE SOUTHEASTERN ATLANTIC COASTAL PLAIN USING TELESEISMIC PHASES

The Southeastern Suture of the Appalachian Margin Experiment (SESAME) was designed to better constrain the record of lithospheric deformation in the southeastern United States related to the late Paleozoic Alleghenian orogeny during the formation of Pangea and subsequent Mesozoic extension associated with the development of the Atlantic passive margin. In this study, direct P waves (Pp) were used as a virtual seismic source for wide-angle reflections generated by teleseismic phases, to image the base of the coastal plain and Mesozoic rift basins, mid- to lower crustal features, the crust-mantle transition zone or Moho, and upper mantle beneath the coastal plain. Results from deconvolved sections for both SESAME lines E and W indicate that Moho travel times increase northward from 8-12 s below the coastal plain to a maximum of 18-19 s beneath the Blue Ridge, and that the Alleghanian suture may dip gently southward and sole into a mid-crustal shear zone. The underlying upper mantle has a layered nature, and the bases of the coastal plain and Mesozoic rift basins deepen southward from the Fall Line. These findings provide insight into the late Paleozoic to Mesozoic evolution of the southeastern Atlantic coastal plain.