Neogene-Quaternary evolution of the Central Mediterranean region

Mountain building, continent-continent collision and post-collisional opening of back-arc basins are the result of geological processes obviously controlled by plate interaction. In the case of the Central Mediterranean region, the kinematic system describing the interaction between the Europe and Africa plates is closely controlled by the kinematic system describing the evolution of Central and North-Atlantic Ocean. Kinematic models derived from the analysis of the Atlantic magnetic anomalies predict in the Mediterranean region slip vectors acting through Tertiary times that fit very well a lot of first-order observed tectonic structures, mostly in the Alps. The same slip vectors, however, do not justify the development in Neogene and Quaternary times of important geological features such as the Western Mediterranean basin, the Tyrrhenian basin, the Southern Apennines and the Calabrian Arc. These vectors, in fact, appear incompatible both in the magnitudes and in the directions with the vectors reconstructed by regional geology that describe the displacement path the investigated geological objects. The occurrence of such large-scale structural features that appear incompatible with the Atlantic-derived kinematic constraints can be justified by different geodynamic processes, the most important of which is certainly represented by the roll-back of down-going lithosphere in subduction zones (the latter do not necessarily coincide with convergence zones) producing rapid flexure-hinge retreat of the lower plate. The roll-back of a subducting lithosphere appears to be the only mechanism able to modify the Atlantic-versus-Mediterranean kinematic balance by adding in the system new source areas and new sink areas. In our presentation we will illustrate some well documented case histories in which maximum flexure-hinge retreat developed at about 90° with the Atlantic-derived slip vectors and in which the Africa/Adria subduction rates computed from the amount of extension in the back-arc basins, from the flexure-hinge retreat in the forward-migrating foredeep-foreland system and from the amount of shortening in the thrust belt system reached values three or four times greater that the values predicted by the Atlantic-derived models