Geodynamics of the central-western Mediterranean region: plausible and non-plausible driving forces

In the last 30 millions years the Mediterranean region has undergone a profound tectonic modification. The pre-existing Alpine orogenic belt have undergone considerable distortions and long migrations of even several hundreds of kilometers. Some zones, mainly located in the internal side of the migrating arcs, have undergone crustal extension and consequent thinning, with the formation of large basins. The complex of the above tectonic processes is generally identified as Arc-Trench-Back Arc system. The old oceanic and thinned continental zones which surrounded the African/Adriatic promontory have been almost completely consumed by subduction. Since extensional deformations are generally considered as scarcely compatible with the compressional context induced by plate convergence, some authors have tentatively advanced the hypothesis that other types of forces acted in the Mediterranean region. In particular, the most often cited interpretation suggests that the migration of arcs and the related back-arc extension have been driven by the gravitational sinking of subducted lithosphere (slab pull).

However, Italian researchers from the Department of Physical, Earth and Environmental Sciences at University of Siena: Professor Enzo Mantovani, Dr. Marcello Viti, Dr. Daniele Babbucci, Dr. Caterina Tamburelli together with Dr. Nicola Cenni from the Department of GeoSciences at University of Padua have argued that the implications of the slab pull driving force can hardly be reconciled with major features of the observed deformation pattern. In particular, the development of the northern, central and southern Tyrrhenian basins in three well distinct phases, since such events would require a discontinuous, very peculiar and scarcely plausible action of gravity on the Adriatic subducted margin. The above authors proposed that a more plausible and coherent explanation of the evolutionary history could be achieved by supposing that Arc-Trench-Back Arc systems developed in the framework of extrusion processes, that in some constricted contexts represented the most convenient shortening mechanism for accommodating plate convergence. Their work is currently published in the research journal, Marine and Petroleum Geology.

In summary, the Italian study critically reviewed existing literature and showed that majority of studies concerning the Mediterranean region often start by citing the various geodynamic interpretations so far proposed for this area, underlying the considerable ambiguity that still surrounds this problem. As such, the dependability of the obtained results is therefore heavily conditioned by the reliability of the adopted tectonic model. Overall, the focus of Professor Enzo Mantovani and his colleagues was to provide expert opinion aimed at obliviating the presumed ambiguity by analyzing the plausibility of the geodynamic interpretations so far proposed, first focusing attention on the models most often cited in literature.