INITIAL LOOK AT 3D SEISMIC DATA ACQUIRED OVER THE GALICIA RIFTED MARGIN
The 3D seismic box covered a variety of geologic features including the Peridotite Ridge (PR) associated with the exhumation of upper mantle rocks to the seafloor, the S reflector interpreted to be a low-angle detachment fault formed late in the rifting process, and a number of rotated fault block basins and ranges containing pre- and syn-rift sediments.
Initial observations, based only on 2D seismic dip lines (albeit 400 m apart), show the along strike variation of the PR: ~1050 m higher than adjacent basement in the South of the 3D box and much increased in height, ~2200 m high in the North. Some cross-sections of the PR show possible internal structure that may help identify the emplacement mechanism of the feature and its relationship with the boundary between rifted continental crust blocks and exhumed upper mantle rocks. To the immediate East and West of the PR there are strong negative-polarity reflectors, apparently at the boundary between post-rift sediment above and transparent sediments below. Based on the reflector polarity, the transparent sediments seem to be of lower velocity than the post-rift sediments above. This material may have sloughed off the PR as it was emplaced at the seafloor and thus may not be found in the fault bounded continental crustal blocks to the East.