HR: 17:15h
AN: T14A-06    [Abstracts]
TI: Neotectonic Structure of Terror Rift, Western Ross Sea, Antarctica: Initial Interpretations of New Geophysical Data
AU: * Wilson, T J
EM: wilson.43@osu.edu
AF: Dept. of Geological Sciences, Ohio State University, 125 S. Oval Mall, Columbus, OH 43210 United States
AU: Lawver, L A
EM: lawver@ig.utexas.edu
AF: University of Texas Institute for Geophysics, 4412 Spicewood Springs Rd, Austin, TX 78759 United States
AU: Henrys, S
EM: S.Henrys@gns.cri.nz
AF: Institute of Geological and Nuclear Sciences, PO Box 30368, Lower Hutt, 0000 New Zealand
AB: The Terror Rift in the western Ross Sea is a prominent neotectonic element of the West Antarctic Rift, yet insufficient data have been available to define the geometries of faults and volcanic bodies or to constrain rift timing in any detail. The RVIB Nathaniel B. Palmer completed a geophysical cruise in the western Ross Sea in early 2004 in order to better understand the history and kinematics of the Terror Rift. Over 7000 km of gravity, magnetic and multibeam bathymetric data were obtained, and extensive new multichannel (2000 km) and single-channel (500 km) seismic reflection profiles were acquired. In addition to the geophysical data, dredging and sampling of submarine and exposed volcanic vents were completed. Limited access to the westernmost Ross Sea due to extensive ice cover precluded complete profiling across the Terror Rift. A significant improvement in line spacing over the eastern Terror Rift, however, allows us to define the eastern limit of the rift basin, and to map fault geometries, displacements and along strike variations in border and intrabasinal fault systems. Volcanic features were mapped by both bathymetric and geophysical data. New mapping of the volcanic field surrounding Franklin Island revealed clusters of submarine volcanic cones and connecting volcanic ridges. The field as a whole has a north to northeast elongation. A separate series of prominent volcanic edifices define a NNW trend extending northward from Beaufort Island and is associated with a zone of intense faulting. Another large submarine volcanic complex is located east of Beaufort Island. In McMurdo Sound, volcanic ridges radiate from the western margin of Ross Island. Successful dredging of seven submarine cones yielded basaltic rocks containing abundant glassy material, as well as mantle and crustal xenoliths. Faults were imaged in the western part of McMurdo Sound and prominent unconformities related to downward flexure in response to Ross Island volcano mass loads were imaged in the eastern Sound. These new seismic profiles will allow us to derive a regional flexural history for this part of the basin. Intriguing glacial erosional and depositional features were clearly imaged by the bathymetric data and provide us with a means to constrain relative timing of glaciation, volcanism and tectonism in the region.
DE: 9310 Antarctica
DE: 8015 Local crustal structure
DE: 8107 Continental neotectonics
DE: 8109 Continental tectonics--extensional (0905)
DE: 3025 Marine seismics (0935)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting