HR: 14:25h
AN: T33D-04    [Abstracts]
TI: Cenozoic rifting in the West Antarctic Rift System
AU: * Granot, R
EM: rgranot@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0220, United States
AU: Cande, S S
EM: scande@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0220, United States
AU: Stock, J M
EM: jstock@gps.caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 921125, United States
AU: Clayton, R W
EM: clay@gps.caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 921125, United States
AU: Davey, F J
EM: F.Davey@gns.cri.nz
AF: Institute of Geological and Nuclear Sciences, PO Box 30368, Lower Hutt, 6040, New Zealand
AB: The West Antarctic Rift System (WARS) experienced two episodes of Cenozoic rifting. Seafloor spreading at the Adare spreading axis, north of the Ross Sea, from Middle Eocene to Late Oligocene time (43 – 26 Ma), was directly linked with motions within the WARS. For this time interval, marine magnetic anomalies within the Adare Basin and structural features within the Ross Sea constrain the motion between East and West Antarctica. During this episode, widespread intrusive activity took place in the continental part of the rift. Subsequent Late Oligocene until present-day (26 - 0 Ma) extension was characterized by a transition to volcanic activity. Yet, the details of extension during this episode have been poorly resolved. We present preliminary results of new seismic reflection and seafloor mapping data acquired on geophysical cruise 07-01 aboard the R/VIB Nathaniel Palmer in the northern part of the rift. Our results suggest that the style of deformation changed from spreading-related faulting into diffuse normal faulting (tilted blocks) that trend NE-SW with little resultant E-W extension. Recent volcanism is distributed throughout but tends to align with the NE-SW trend, into a localized zone. Formation of the Terror Rift, Ross Sea, within the same time frame suggests that the pole of rotation has changed its position, reflecting a change in the relative magnitudes of tensile stresses along the rift. Moreover, this change was accompanied with a sharp decrease of extension rates.
DE: 3025 Marine seismics (0935, 7294)
DE: 3075 Submarine tectonics and volcanism
DE: 8109 Continental tectonics: extensional (0905)
DE: 9310 Antarctica (4207)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting