NEW CHARACTERIZATION OF THE S-REFLECTOR FROM GALICIA MARGIN, OFFSHORE SPAIN

The crustal architecture of passive continental margins provides valuable clues for understanding rift initiation and the rift-drift transition. The Galicia Margin is an archetype magma-poor margin displaying many common features of its kind such as a wide necking zone, serpentinized mantle, lack of a clear Moho in the exhumed zone, etc. Here we focus on the S-reflector, the major low-angle detachment fault in the Deep Galicia Margin. We present interpretations from a 3-D seismic dataset from this region that was acquired and processed to prestack time migration in 2013, along with extracted attribute analyses.

We mapped the S-reflector and the overlying low velocity zone (LVZ) as two related but distinct, non-parallel surfaces (here labelled as S and S') enveloping a fault zone of varying thickness. We interpret the intervening layer as fault gouge. The gouge zone ranges in thickness from essentially no thickness to 429 m. A new nomenclature for this reflection package is also presented and called the "S-interval". Additionally, we interpret the area to be a unique type of "blended" core complex. The fault surface is strongly corrugated in several patches of the fault zone. These occur in the NW, center and S parts of the dataset. The patches have azimuths of 159, 153 and 178 degrees which averages to the normal of the M0 magnetic anomaly, but also displays that the minimum stress vectors may have been oriented at different angles, at different times along the margin.