HR: 10:35h
AN: T52B-02 INVITED     [Abstracts]
TI: Subduction, convergence and the mode of backarc extension in the Mediterranean region
AU: * Jolivet, L
EM: laurent.jolivet@lgs.jussieu.fr
AF: Universite Pierre et Marie Curie, 4 place Jussieu, Paris, 75252 France, Metropolitan
AU: Augier, R
EM: romain.augier@lgs.jussieu.fr
AF: Universite Pierre et Marie Curie, 4 place Jussieu, Paris, 75252 France, Metropolitan
AU: Faccenna, C
EM: faccenna@uniroma3.it
AF: Universita Roma Tre, Largo San Murialdo 1, Rome, 00146 Italy
AB: The Cenozoic period in the Mediterranean region was characterized by a sharp change in the subduction dynamics some 30-35 Ma ago, from generalized compressional subduction, leading to the formation of Alpine mountain belts, to extensional subduction and the formation of backarc basins, from the Alboran Sea to the Aegean Sea. Backarc extension was thus associated with collapse of the mountain belts formed before this Oligocene revolution. Sedimentary basins evolved in connection with the reactivation of thrust faults as extensional detachments or the creation of new detachments. From the Aegean Sea to the Tyrrhenian Sea and the Alboran Sea we have analysed onshore the kinematic and P-T evolution of the ductile crust exhumed by extension and the transition from ductile to brittle conditions and the relations between deep deformation and the formation of basins. We show two different types of evolution : in the eastern Mediterranean where subduction had been engaged in the Early Mesozoic, and in the Central and Western Mediterranean where it started only in the late Cretaceous or Early Cenozoic. We show that (1) the early tectonic fabric has little influence of the kinematic of the post-orogenic extension, (2) the asymmetry of extension (sense of shear along crustal-scale detachments) differs whether subduction is associated or not with convergence. We tentatively propose a scheme explaining how the interactions between the subducting slab and the mantle control the basal shear below the upper plate and the geometry and distribution of detachments and the associated sedimentary basins. The example of the Betic Cordillera and the Rif orogen, where the direction of stretching where different in the lower and the upper crust and changed through time, is discussed and we proposed a scenario of evolution from the Eocene to the Tortonian.
DE: 8199 General or miscellaneous
DE: 8109 Continental tectonics--extensional (0905)
DE: 8110 Continental tectonics--general (0905)
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting