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Tectonic shortening and gravitational spreading in the Gulf of Cadiz accretionary wedge: Observations from multi-beam bathymetry and seismic profiling

Marc-André Gutscher 1, 2, * Stephane Dominguez 3 Graham K. Westbrook 4 Pascal Gente 1, 2 Nathalie Babonneau 1, 2 Thierry Mulder 5 Eliane Gonthier 5 Rafael Bartolome 6 Joaquim Luis 7 Filipe Rosas 8 Pedro Terrinha 9 The Delila And Delsis Scientific Teams
* Corresponding author
1 LDO - Domaines Océaniques
2 UEB - Université européenne de Bretagne - European University of Brittany
3 Géosciences Montpellier
4 University of Birmingham [Birmingham]
5 EPOC - Environnements et Paléoenvironnements OCéaniques
6 CMIMA
7 University of Algarve [Portugal]
8 Faculdade de Ciências [Lisboa]
9 INETI - Instituto Nacional de Engenharia, Tecnologia e Inovacco
Abstract : The Gulf of Cadiz lies astride the complex plate boundary between Africa and Eurasia west of the Betic-Rif mountain belt. We report on the results of recent bathymetric swathmapping and multi-channel seismic surveys carried out here. The seafloor is marked by contrasting morphological provinces, spanning the SW Iberian and NW Moroccan continental margins, abyssal plains and an elongate, arcuate, accretionary wedge. A wide variety of tectonic and gravitational processes appear to have shaped these structures. Active compressional deformation of the wedge is suggested by folding and thrusting of the frontal sedimentary layers as well as basal duplexing in deeper internal units. There is evidence for simultaneous gravitational spreading occurring upslope. The very shallow mean surface and basal slopes of the accretionary wedge (1° each) indicate a very weak decollement layer, geometrically similar to the Mediterranean Ridge accretionary complex. Locally steep slopes (up to 10°) indicate strongly focused, active deformation and potential gravitational instabilities. The unusual surface morphology of the upper accretionary wedge includes “raft-tectonics” type fissures and abundant sub-circular depressions. Dissolution and/or diapiric processes are proposed to be involved in the formation of these depressions.
Keywords : Iberia Morocco Accretionary wedge Decollement Gravitational spreading
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Submitted on : Friday, July 3, 2009 - 5:59:07 PM
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Marc-André Gutscher, Stephane Dominguez, Graham K. Westbrook, Pascal Gente, Nathalie Babonneau, et al.. Tectonic shortening and gravitational spreading in the Gulf of Cadiz accretionary wedge: Observations from multi-beam bathymetry and seismic profiling. Marine and Petroleum Geology, Elsevier, 2009, 26 (5), pp.647-659. ⟨10.1016/j.marpetgeo.2007.11.008⟩. ⟨insu-00401683⟩

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