HR: 14:40h
AN: T33D-05    [Abstracts]
TI: Velocity Structure of the Rifted Crust in the Northwestern Ross Sea, From Seismic Refraction Data
AU: * Selvans, M M
EM: selvans@gps.caltech.edu
AF: California Institute of Technology, Mail Stop 252-21, Pasadena, CA 91125, United States
AU: Stock, J M
EM: jstock@gps.caltech.edu
AF: California Institute of Technology, Mail Stop 252-21, Pasadena, CA 91125, United States
AU: Clayton, R W
EM: clay@gps.caltech.edu
AF: California Institute of Technology, Mail Stop 252-21, Pasadena, CA 91125, United States
AU: Cande, S C
EM: scande@ucsd.edu
AF: Scripps Institution of Oceanography, Mail Code 0220, La Jolla, CA 92093-0220, United States
AU: Davey, F J
EM: F.Davey@gns.cri.nz
AF: Institute of Geological and Nuclear Sciences, P.O. Box 30368, Lower Hutt, 00000, New Zealand
AB: Extension in the West Antarctic Rift System produced the Transantarctic Mountains, deep sedimentary basins in the Ross Sea, and the Adare Trough spreading center (43 to 26 Ma). The Adare Basin and Northern Basin are located at the northwesternmost extent of this region of deformation, and are generally assumed to be oceanic and continental crust respectively. Their boundary therefore provides an ideal study area for linking the styles of extension in the two types of crust. We process seismic refraction data collected during research cruise NBP0701 to determine 2D crustal velocity models along four seismic lines at the margin of the Adare and Northern Basins. The 48 closely-spaced sonobuoy records included in this study provide continuous refraction data coverage; three of these lines have reversed sonobuoy records. Finite difference modeling of the individual sonobuoys provides accuracy in our interpreted layer velocities, confidence in tracing refracted arrivals back to their associated reflections in the sonobuoy records, and the ability to match these reflected arrivals with the multi- channel seismic reflection data. Preliminary results from the line trending perpendicular to the margin of the Adare and Northern Basins show no change in crustal velocity structure from one basin to the other, with nearly flat velocity contours along the entire line. An apparent velocity of 8000 m/s is observed along this line in the Northern Basin. A comparable layer velocity is not detected in the sonobuoy record shot in the reverse direction, so this velocity could be due to local basement topography. Alternatively, the high velocity may indicate mantle material, and an unusually thin crust at that location. We model structural layers and associated velocities below the sea floor in order to better understand the physical structure and deformational history of the crust in the northwestern Ross Sea. The velocity horizons determined from this data set provide model constraints for a new type of crust that may be formed during rifting, and should be one end-member resulting from the continental rifting process.
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8159 Rheology: crust and lithosphere (8031)
DE: 8178 Tectonics and magmatism
SC: Tectonophysics [T]
MN: 2007 Fall Meeting