Miocene Shale Tectonics in the Northern Alboran Sea (Western Mediterranean)
Juan I. Soto, Fermín Fernández-Ibáñez, Asrar R. Talukder, Pedro Martínez-García, 2011. "Miocene Shale Tectonics in the Northern Alboran Sea (Western Mediterranean)", Shale Tectonics, Lesli J. Wood
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The Alboran Basin is a back-arc basin in the Mediterranean developed during the Miocene by the extensional collapse of the thick continental orogen known as the Betic-Rif arc. Collision and basin formation occurred in the Neogene as a result of oblique convergence of the Eurasian and African plates. A major, curved depocenter (with sedimentary accumulations >10 km [>6 mi]) is located to the west of this basin, containing a diapiric province with overpressured shales and mud volcanoes. This study presents a detailed reconstruction of the three-dimensional geometry of the diapirs and associated minibasins in the northern margin of this major depo-center (offshore Spain). Basin formation began in the early Miocene when rapid initial subsidence of the basin floor was accompanied by massive sedimentation and burial of fine-grained sediments. Gravity-driven tectonics and continuous basement subsidence during the Miocene led to downslope migration of mobile shales, whereas the basin margins were affected by syn-sedimentary extension, and associated shale-cored thrusts occurred in the basin depocenter. Extension occurred by means of low-angle normal faults coalescing with the basement surface, which represents a master detachment surface. Thin-skinned extension during the Miocene was accompanied by punctuated diapir ascent and the advance of shale sheets. Downslope shale advance was enhanced by counterregional high-angle normal faults isolating noncylin-drical minibasins in the overburden. The Alboran Basin therefore is a useful area for analysis of the structural pattern associated with shale tectonicprocesses and a key basin for comparing the geometries and evolution of shale with structures formed in salt basins.