Subduction, volcanism, collision, orogenesis and faults: How do they shape the central Mediterranean region?

Abstract

From a geological and geodynamical point of view, the central Mediterranean area represents one of the most intriguing and enigmatic regions in the world and it still continues to capture Earth scientists’ attention. The region is characterized by spectacular surface geological features due to the complex mechanisms in the lithosphere and mantle of this fascinating region. Long-term geodynamical processes as well as active tectonics are testified by high mountain belts (up to 4000 m) thousands of kilometres long, deep sea basins as well as frequent and strong earthquakes and widespread volcanism. The central Mediterranean inherited the ∼250 Myr – long history of the oceanic Tethys realm and its continental surroundings (Dewey et al., 1989 and Dercourt et al., 1986). The region is the result of several phases of fragmentation of the former continuous Western Mediterranean subduction zone and its opening took place mostly in the last 30 Myr with the development of several back-arc extensional basins (Gueguen et al., 1998). It is a very complex area, characterized by the presence of four subduction zones (the W-directed Apennines–Maghrebides; the SW-directed Carpathians; the NE-directed Dinarides-Hellenides-Taurides; the SE-directed Alps) characterized by variable geometry and subduction rates and also by different polarity and type of involved lithosphere (oceanic, thinned continental crust). In addition, the region is characterized by a significant seismicity and intense volcanism and by the presence of active thrust belts like the Apennines, the Alps and the Carpathians that are small and narrow orogenic systems characterized by an accentuated arcuate shape (oroclines) that makes them quite different with respect to other orogenic systems worldwide (Nemcock et al., 2005). The geodynamic evolution of the region results from the complex interaction among several coeval and in some cases contrasting processes, such as early passive margin development and subsequent basin inversion, oceanic subduction, plate collision, slab rollback, back-arc basin opening, crustal delamination and rock exhumation (e.g. Jolivet et al., 2008). The slow long-lasting N–S convergence processes between the African and Eurasian major plates has always been considered as the primary tectonic mechanism in modelling the shape of the area (e.g. Wortel and Spakman, 2000). Moreover, the presence of first-order mega-scale extensional structures such as the Alboran Sea, the Algero-Provençal and Tyrrhenian basins as well as the Pannonian basin synchronous to the development of arched and narrow fold-and-thrust belts such as the Betics, the Maghrebides, the Apennines, the Alps, the Carpathians, and the Dinarides-Hellenides undeniably required forces and processes in addition to the Africa–Eurasia collision and being partly independent of it (e.g. Jolivet and Faccenna, 2000). Several authors agree in invoking the subduction zone retreat and associated arc migration, tearing and subsequent slab break-off as pilot mechanisms capable of explaining the combination of such different tectonic styles in a quite narrow area as well as the intense volcanism explained as possible tear-related magmatism (e.g. Govers and Wortel, 2005 and Schellart, 2010). In the last decade, there has been a growing number of geological and seismological studies that contribute to a great improvement and advance in the knowledge of the present-day configuration of the central Mediterranean region and its geodynamic history (e.g. Rosenbaum et al., 2008, Guillaume et al., 2010, Diaz et al., 2010, Baccheschi et al., 2011, Baccheschi et al., 2008, Pastor-Galán et al., 2012, Palomeras et al., 2014, Barruol et al., 2011, Bokelmann et al., 2013 and D’Amico et al., 2013). Yet, many questions about the spatio-temporal changes in the nature of subduction, collisional and extensional plate boundaries and consequent seismicity, as well as crustal uplift and intense erosion, crustal shortening and thickening, lateral displacement of both lithosphere and asthenosphere, are still poorly answered. There is a need to obtain new data to understand the present-day geodynamic interactions between tectonic plates and mantle convection, subduction processes, crustal extension and compression, large-scale subsidence and uplift. This Special Issue collects original research papers with the aim to give an updated characterization of the relationships between geodynamic processes, surface processes and earthquake distribution in the central Mediterranean and surroundings. The topics span from the imaging of three-dimensional deep and crustal structures and mantle dynamics to the study of surface processes such as active tectonics, magmatic activity, and sedimentary evolution of basins through the analysis of body wave tomography, receiver function, shear wave splitting anisotropy, earthquake distributions, geodetic data and structural geology.