Post-Tortonian deformation pattern in the Central Mediterranean : A result of extrusion tectonics driven by the Africa-Eurasia convergence

The tectonic activity which has ocurred in the Central Mediterranean since the late Tortonian is explained as a result of the Africa-Eurasia convergence roughly along a SSW-NNE direction. This convergence has been first accommodated by a considerable reduction of the Adriatic foreland, through the consumption of its eastern and western margins, and then by the lateral escapes of crustal wedges, accompanied by crustal thickening, in the zone comprised between the Adriatic and African forelands. The lateral escapes of the Calabria and Sicily blocks, towards SE and NW respectively, have been allowed by the presence, at the sides of the most strongly compressed zone, of poorly constrained boundaries, corresponding to the thinned Ionian foreland and, to the zone of crustal stretching in the Tyrrhenian basin. This interpretative scheme allows physically plausible explanations of a considerable amount of geological, geophysical and volcanological evidence in the framework of relatively simple and coherent tectonic mechanisms

Africa-Eurasia kinematics in the Mediterranean : An alternative hypothesis

The post-Tortonian deformation pattern in the Central Mediterranean can be satisfactorily interpreted in the framework of a SSW-NNE to SW-NE convergence between Africa and Eurasia (Mantovani et al., 1992 and this volume). However, this hypothesis is not in line with the most widely used Africa-Eurasia kinematic models, based on the analysis of North Atlantic kinematic data, which predict a SE-NW to S-N motion between Africa and Eurasia. Here it is argued that these models might be not reliable, since are based on the assumption that Eurasia is a unique coherent block from the Atlantic ridges to the Pacific trenches, which can hardly account for the significant intraplate deformation occurring in Western Europe, and in particular, in the Iberian Peninsula and surrounding regions. This evidence would imply that the kinematic data observed along the Mid-Atlantic ridges just North of Azores and those on the Azores-Gibraltar belt cannot be used to constrain the relative motions of Eurasia with respect to North America and Africa respectively. It is shown by quantitative computations that the remaining kinematic data in the North Atlantic can be reconciled, within errors, with a NNE to NEward motion of Africa with respect to Eurasia, in the Central Mediterranean. This kinematic pattern does not involve any significant difficulty in explaining the tectonic pattern in the other sectors of the Mediterranean area and along the boundaries of the Eurasian continent