A structural scheme for the Western Mediterranean area in Jurassic and Early Cretaceous times

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Abstract
On the basis of the available reconstructions of the central Atlantic Ocean opening, a model of the early structural development of the Western Mediterranean area is presented. Following an early rifting step in the Upper Triassic-Lowermost Liassic, the most important rifting begins in the Sinemurian. At the Callovian times, the central Atlantic has undertaken its oceanic speading. Correlatively, as in the Western Alps, such a spreading needs to be active in the Western Mediterranean area. Just like in the external and foreland regions of the Alpine Belt, the extension proceeded by NE-SW graben which cut across the Alpine internal zones (Alboran plate) and then evolved as narrow basins underlain by thinned continental crust or by oceanic crust. These graben-basins were offset by E-W transform faults, the most important one lying along North Africa. During the second half of the Lower Cretaceous, large clastic inputs coming from the Sanarian shield, contributed to form the external flysch deposits of North Africa; deep sea fans of this detritic material were also able to reach the internal basins and form the Internal (« ultra ») Flysch. The proposed structural pattern is able to explain the complex tectonic evolution of the Internal Zones around the Western Mediterranean.