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Gaullier, Virginie1, J. Deverchere2, J.-P. Bouillin3, C. Bracene4, E. Calais5, A. Kherroubi6, B. Mercier de Lepinay7, P. Le Roy2, H. Pauc8, B. Savoye9, A. K. Yelles6
(1) Université de Perpignan, Perpignan, France
(2) Domaines Oceaniques, UMR 6538, University of Brest, Brest, France
(3) LGCA, University of Grenoble, Grenoble, France
(4) SONATRACH, Boumerdes, Algeria
(5) Purdue University
(6) C.R.A.A.G, Algiers, Algeria
(7) Geosciences-Azur, UMR 6526, Nice, France
(8) LEGEM, University of Perpignan, Perpignan, France
(9) IFREMER, Brest, France

ABSTRACT: Combined Salt-Related Thin-Skinned Tectonics and Crustal Tectonics in the Algerian Deep Waters (SW Mediterranean): Evidence from the MARADJA Research Cruise

The margin and deep basin offshore Algeria, although representing a major part of the Europe-Africa convergent plate boundary, are among the least-imaged oceanic domains in the Mediterranean. Data from our recent survey (MARADJA cruise, on board the R/V "Suroit") conducted in August and September 2003 on the slope and deep basin fill the gap and allow to better understand the interaction between tectonics (crustal-scale or gravity-driven), and sedimentary processes. We collected multibeam bathymetry data, back-scattering imagery, 3.5 kHz profiles (Chirp), 6-channel and 24-channel seismic reflection, and few cores. Our data illustrate how an area comprising thick, mobile evaporites (Messinian) deforms in response to combined crustal-scale tectonics and gravity-driven tectonics.We observe that (1) the salt layer pinches out abruptly at the slope break, (2) the proximal extension domain is narrow, and (3) there is no transitional, translational domain between the extensional and contractional domains. This pattern may be related to the steep slope of the Algerian margin or to the influence of compressional crustal tectonics. In some areas, such as in front of the Messinian palaeo-topographic high of Khayr Al-Din, offshore Bou-Ismail Bay, deformation of the brittle Upper Evaporites and Plio-Quaternary sedimentary cover is typical of pure gravity gliding/spreading. There, large salt ridges form a complex 3-D network, suggesting that they formed in response to multi-directional shortening. Elsewhere, in areas reactivated recently, salt is more passively deformed by crustal-scale convergence. Most salt walls and anticlines are oriented perpendicular to the NW-SE crustal compressional stress direction.

 

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.