HR: 15:25h
AN: S22C-08    [PDF]
TI: Deep Seismic Imaging of an Active Foreland Basin: Implications for Flexural Models
AU: * White, N
EM: nwhite@esc.cam.ac.uk
AF: University of Cambridge, Bullard laboratories Madingley Rise Madingley Road, Cambridge, CB3 0EZ United Kingdom
AB: The South Falkland basin is a partially filled, active, foreland basin located at the southern edge of the Falkland Plateau. It was formed by flexure of the South American plate as a result of loading by the northern edge of the Scotia plate. Flexure probably started in the Paleogene and continues to the present day. The entire region is submarine and the detailed structure of this basin is clearly imaged on shallow reflection data. Admittance analysis of free-air gravity and bathymetry together with gravity and basement profile modelling suggest that the elastic thickness is 10--20 km. Recently, we have acquired and processed a deep seismic reflection profile which crosses the foreland basin and the zone of active collision. This line was shot to 18 seconds two-way travel time using a 5600 cubic inch airgun array and a 6 km streamer. These new data have yielded spectacular images of the active foreland basin and of the adjacent plateaux. The most striking features are a clearly imaged Moho and a set of highly reflective normal faults which penetrate to about 20 km depth. We can show that these normal faults were active during the process of plate flexure. Their existence, depth of penetration and reflectivity raise important questions about the applicability of elastic models to foreland basin formation. Here we explore alternative models which can account for these new observations without requiring the existence of large elastic stresses.
DE: 8105 Continental margins and sedimentary basins
DE: 8107 Continental neotectonics
DE: 8162 Rheology--mantle
DE: 8164 Stresses--crust and lithosphere
SC: Seismology [S]
MN: 2003 Fall Meeting