Last abstract (GSA 2016)
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 as two related by distinct, non-parallel surfaces (here labelled as S and S') enveloping a fault zone of varying thickness that has a range from essentially no thickness to 429 m. We interpret this as the fault gouge. A new nomenclature for this reflection package is also presented and called the "S-interval".
Some comparative evidence is provided for the area being a unique type of "blended" core complex. Additionally, we show certain corrugations in patches on the fault surface in the NW, center and S of the dataset, with azimuths of 159, 153 and 178 degrees respectively. We discuss these corrugations' implications on determining rift axes, and finally display that the minimum stress vectors may have been oriented at different angles along the margin.