HR: 0800h
AN: T41A-0370    [Abstracts]
TI: The Galicia Bank Influence on the Southern Iberia Abyssal Plain Drilling Transect
AU: * Clark, S A
EM: s.a.clark@geo.uio.no
AF: Dept. of Geosciences, Univ. of Oslo, POBox 1047 Blindern, Oslo, N-0316, Norway
AU: Sawyer, D S
EM: dale@rice.edu
AF: Dept. of Earth Science, Rice Univ., MS-126, POBox 1892, Houston, TX 77251-1892, United States
AU: Faleide, J
EM: j.i.faleide@geo.uio.no
AF: Dept. of Geosciences, Univ. of Oslo, POBox 1047 Blindern, Oslo, N-0316, Norway
AB: The Iberia nonvolcanic rifted margin has been studied primarily within the context of two distinct segments: Galicia Bank (GB) and the Southern Iberia Abyssal Plain (SIAP). The bathymetric contrast between GB (2-4 km water depth) and the SIAP (~5 km water depth) differentiates the two segments, in addition to distinctions in the widths of extended continental crust (GB: ~260 km; SIAP: ~80 km) and the zone of exhumed continental mantle (ZECM; GB: 0-60 km; SIAP: ~170 km). We have speculated that crustal-scale mass wasting may have altered the original transform segment boundary between GB and the SIAP. Our interpretation proposes transport of extended continental crust and overlying pre-rift sediments southward from GB onto exhumed, serpentinized peridotite of the SIAP. We reexamine the ODP Legs 149/173 drilling transect in the context of this hypothesis. Shallow-water Tithonian-Berriasian sediments sampled at sites 901 and 1065 atop basement highs of interpreted 4-6 km-thick continental crust could have been originally deposited atop GB, slumping with upper crustal blocks to the south sometime during the Tithonian to Valanginian. In this interpretation, serpentinized peridotite sampled at site 1068 represents the pre-existing SIAP ZECM onto which the slump was deposited. We suggest that intra-crustal faulting caused by east-west extension may have weakened the upper crust of GB sufficiently to allow gravitational collapse. Our interpreted slump then represents the latest faulting of a polyphase rift evolution. Examination of the Iberia margin bathymetry hints at a concave fault-scarp at the crown of our proposed slump; we use the bathymetry to resolve other potential locations of slumping, as well as regions that appear unaffected by mass wasting.
DE: 3036 Ocean drilling
DE: 3070 Submarine landslides
DE: 8109 Continental tectonics: extensional (0905)
DE: 8111 Continental tectonics: strike-slip and transform
DE: 8169 Sedimentary basin processes
SC: Tectonophysics [T]
MN: 2007 Fall Meeting