HR: 0800h
AN: T41E-1266    [Abstracts]
TI: Cenozoic Tectonism of the Southeastern United States Continental Margin from Deep Seismic Reflection Data
AU: * Addison, A D
EM: aaddison@geol.sc.edu
AF: Department of Geological Sciences, University of South Carolina, 701 Sumter St., Columbia, SC 29208 United States
AU: Knapp, C C
EM: camelia@geol.sc.edu
AF: Department of Geological Sciences, University of South Carolina, 701 Sumter St., Columbia, SC 29208 United States
AU: Knapp, J H
EM: knapp@geol.sc.edu
AF: Department of Geological Sciences, University of South Carolina, 701 Sumter St., Columbia, SC 29208 United States
AB: A deep seismic reflection profile, SEISDATA 6 (SD 6), was collected in the state of Georgia (United States), in 1981, with the main purpose to study the crustal structure and tectonic evolution of the southeastern North American continental margin. The SD 6 profile, with a total length of approximately 430 km, was collected by Seisdata Services Inc. of Houston, Texas in conjunction with the USGS in two separate transects, the Blue Ridge and Piedmont Provinces (8 s) and the Atlantic Coastal Plain Province (6 s). The Piedmont Province consists of metamorphic and igneous rocks that record tectonic regional metamorphism with the intrusion of igneous plutons. The Piedmont is bounded by the Brevard fault zone to the NW and the Fall line to the SE. Exposed faults and Mesozoic rift basins and complex folding are present in the Piedmont. The Atlantic Coastal Plain (ACP) Province is bounded by the Fall line to the NW and the Atlantic Ocean to the SE. Marine and fluvial/deltaic sediments make up the strata and irregularly cover the Piedmont Province. While only limited parts of the SD 6 seismic profile had been processed in the past, the main target of this study is to reprocess the entire profile using more modern techniques in order to obtain a crustal-scale image of the southeastern U. S. continental margin, and evaluate evidence for, still disputable, (1) reactivation and sense of movement of preexisting basement faults in the Piedmont region, (2) recognition of potentially multiple stages of deformation on these faults in the Paleozoic, Mesozoic, and Cenozoic times, and (3) identification of the differences in rheology of the crystalline basement from west to east. Reprocessing of the SD 6 line has focused on reflection enhancement at large depths, static corrections from first break picking, velocity analysis, wavelet deconvolution, time-variant amplitude gain, and post-stacking migration. Preliminary results of the reprocessing show evidence for large offsets in the crystalline basement in the Piedmont, with reverse sense of movement, indicating basement faults that trend predominately toward the northeast. High amplitude crustal reflectors that slightly dip toward the SE are present in the Piedmont and in the ACP below the marine and fluvial/deltaic sediments. Coastal marine sediments reflectors are parallel to sub-parallel with a sharp high amplitude reflector between the coastal plain sediments and the basement. Reprocessing of the data has shown further evidence of Cenozoic movement on the preexisting basement faults. Although it is widely accepted that the Southeastern margin of the U.S. has been a passive boundary since the Cretaceous time, however, there is evidence of Cenozoic tectonism including regional scale uplift from these seismic data.
DE: 8010 Fractures and faults
DE: 8015 Local crustal structure
DE: 8110 Continental tectonics--general (0905)
DE: 8159 Rheology--crust and lithosphere
DE: 7205 Continental crust (1242)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting