The geological evolution of the western Mediterranean exhibits complicated interactions between orogenic processes and widespread extensional tectonics. The region is located in a convergent plate margin separating Africa and Europe, and consists of marine basins - the Alboran Sea, the Algerian-Provençal Basin, the Valencia Trough, the Ligurian Sea and the Tyrrhenian Sea (Figure 1) - which formed as back-arc basins since the Oligocene. The evolution of these basins, simultaneously with ongoing convergence of Africa with respect to Europe, has been the subject of numerous studies (e.g., Stanley & Wezel 1985, Durand et al. 1999). Widespread extension associated with the formation of these basins led to considerable thinning of the continental crust (i.e., in the Alboran Sea and the northern Tyrrhenian) or to the local initiation of sea floor spreading (i.e., in the southern Tyrrhenian and Provençal Basin). Furthermore, extensional tectonism in the western Mediterranean was coeval with orogenesis in the adjacent mountain chains of the Rif-Betic cordillera, the Maghrebides of northern Africa and Sicily, the Apennines, the Alps and the Dinarides (Malinverno & Ryan 1986, Crespo-Blanc et al. 1994, Tricart et al. 1994, Cello et al. 1996, Azañón et al. 1997, Frizon de Lamotte et al. 2000, Faccenna et al. 2001)(Figure 1).

Figure 1. Regional Map

Regional Map

(a) Topography of the western Mediterranean region; (b) tectonic setting of the western Mediterranean basins and the Alpine orogen (only Mediterranean marine basins are coloured). Ca = Calabria; Co = Corsica; GK = Grand Kabylie; PK = Petite Kabylie; Sa = Sardinia; Si = Sicily.

The simultaneous formation of extensional basins together with thrusting and folding in adjacent mountain belts has led to several tectonic models that acknowledge the role of large-scale horizontal motions associated with the retreat of the subduction trench (hereafter termed subduction rollback) (Malinverno & Ryan 1986, Royden 1993a, Lonergan & White 1997). These provide an explanation for the origin of allochthonous terranes, which drifted great distances to their present locations (e.g., Calabria). However, some issues are yet to be resolved and have been the subject of considerable debate. Different models have been proposed to explain the evolution of the Alboran Sea, namely, as a back-arc basin associated with a retreating slab (Lonergan & White 1997), or as the result of an extensional collapse of thickened lithosphere (Platt & Vissers 1989, Housman 1996). The evolution of the Tyrrhenian Sea is also controversial, with some fundamental problems in the current explanations of the evolution of this basin.

In this work, we aim to develop a coherent visual reconstruction that will best explain the large-scale tectonics of the western Mediterranean region. We use a wealth of accumulated knowledge as published in the literature, as well as a new software package that provides the ability to perform an interactive reconstruction. The reconstruction is presented as an animation, which clearly demonstrates some fundamental features seen in convergent plate margins. It shows the complex interactions between subduction processes, horizontal extension, block rotations and accretion events, and it emphasises the roles of subduction rollback and the episodic accretion of allochthonous terranes during orogenesis.