Abstract
The west Galicia rifted margin is a non-volcanic rifted margin, characterised by landward tilted fault blocks bound by ocean ward dipping faults. The fault blocks are underlain on time sections by an undulating group of bright reflections, the so-called Galicia S reflector. We use a variety of advanced processing techniques to constrain the nature of S, including pre stack depth migration to construct detailed velocity models of the section overlying S, and to provide optimum images of portions of the data in depth. Our results show that S passes continuously beneath the tilted fault blocks of the deep margin. We interpret S and associated reflectors as a brittle detachment fault system, similar to those observed in the western USA. We infer that the detachment was active during the last phase of extension immediately prior to continental breakup. To the west, S appears to be truncated by east-dipping reflections coming off a ridge of peridotite. This ridge, drilled during ODP Leg 103 is characterised by top-to-the-east shear structures. We relate these east-dipping reflections, not S, to this shear zone and propose that this east-dipping structure (rather than S) was responsible for the exhumation of the mantle rocks. Our results are discussed in the context of the evolution of the margin.
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Krawczyk, C.M., Reston, T.J. (1995). Detachment Faulting and Continental Breakup: The S Reflector Offshore Galicia. In: Banda, E., Torné, M., Talwani, M. (eds) Rifted Ocean-Continent Boundaries. NATO ASI Series, vol 463. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-0043-4_13
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DOI: https://doi.org/10.1007/978-94-011-0043-4_13
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