HR: 10:35h
AN: T52B-02    [Abstracts]
TI: Synrift geometry, structural complexity and low-angle activity of the S reflector at the west Galicia rifted margin.
AU: Booth-Rea, G
EM: gbooth@ugr.es
AF: Dpt. de Geodin mica, Universidad de Granada, Campus Fuentenueva S/N, Granada, 18076 Spain
AU: * Reston, T J
EM: treston@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstrasse 1-3, Kiel, D24148 Germany
AU: Klaeschen, D
EM: dklaeschen@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstrasse 1-3, Kiel, D24148 Germany
AB: The west Galicia rifted margin is characterised by tilted fault blocks above a well-developed reflection, the S reflector. By analogy with the H reflection further south, from wide-angle velocities and from seismic images, S is interpreted as a detachment fault developed at the top of a zone of serpentinized mantle. Previous authors failed to recognize the youngest synrift sedimentary units above S, although the presence of deep water sediments tilted within the fault blocks implies the presence of older synrift sedimentary units. However, detailed examination of the sedimentary geometries above S imaged on prestack depth migrated data has revealed the presence of wedges of sediments fanning towards the block-bounding faults. In some case these wedges represent hanging-wall syncline basins formed by fault-bend folding above faults with flat-ramp-flat geometry. From the geometry and basin-fill architecture of the syncline basins, we can reconstruct the original fault geometry, the amount of tilting that has occurred during and since fault movements, and the importance of sedimentation/erosion during rifting. The results indicate that faults detached upon the S reflector that was active at angles considerably less than 20°, and as such S is a genuine low-angle fault. The angle at which S appears to have been active cannot readily be explained by Mohr-Coulomb theory even in the presence of weak serpentinites. We propose that movement along S was facilitated by transient high pore pressures associated with the process of serpentinisation.
DE: 3025 Marine seismics (0935, 7294)
DE: 8010 Fractures and faults
DE: 8045 Role of fluids
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8109 Continental tectonics: extensional (0905)
SC: Tectonophysics [T]
MN: Fall Meeting 2005