Polyphase faulting during the development of the west Galicia rifted margin.

Reston, Timothy J. (2005) Polyphase faulting during the development of the west Galicia rifted margin. Earth and Planetary Science Letters, 237 (3-4). pp. 561-576. DOI 10.1016/j.epsl.2005.06.019.

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Rifted margins are commonly characterised by an extension discrepancy: the amount of extension measurable from the observed faulting is far less than that required to explain the crustal thinning. It is shown here that polyphase faulting may provide a simple explanation for this paradox, but can be very hard to recognise on seismic sections. However at the west Galicia rifted margin (the Galicia Interior Basin between the Galicia Bank and the mainland, and the deep Galicia margin to the west of the Galicia Bank), a combination of high quality depth images, seismic velocity information and stratigraphic control through ODP drilling and submersible sampling, provide complementary evidence for polyphase faulting. Berriasian–Hauterivian rifting in the Galicia Interior Basin occurred along two sets of faults: the first unroofed deep crustal rocks, evidenced by high seismic velocities close to top basement; the second cut and dismembered these early faults. Further rifting (up until the Aptian) then focussed west of the Galicia Bank, where two further phases of faulting can be inferred from the diachronous nature of seismostratigraphic units tilted within fault blocks. Removal of the latest phase of faulting aligns discontinuous reflections within the fault blocks into an anastomosing network of earlier faults; restoration along these brings the crust back to its early Hauterivian state, similar to the present structure of the Interior Basin.

Document Type: Article
Keywords: rifting; polyphase; faulting; seismic; extension discrepancy
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.epsl.2005.06.019
ISSN: 0012-821X
Date Deposited: 05 Dec 2008 12:01
Last Modified: 21 Dec 2016 09:19
URI: http://oceanrep.geomar.de/id/eprint/3902

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