Paleomagnetic Rotations And Continental Deformation

One of the most interesting results obtained in the last two decades in the study of crustal deformation has been the recognition that large regions of continental crust undergo rotations about vertical axis during deformation. Proof of such rotations has come through the paleomagnetic studies, which reveal rotations when paleomagnetic declinations within the deforming region arc compared with those found in coeval rocks in the stable regions outside the deforming zone. Such rotations were first described in Oregon then in the North American Cordilleras and in Southern California and were a surprise to everyone. Even in California which, as a result of oil exploration, was among the best geologically explored regions in the world, no one could claim to have predicted that these rotations would be found. Rotations have subsequently been found in other areas of recent continental tectonic activity, notably in the Basin and Range province, New Zealand, the Andes, Greece and Western Turkey, so that they appear as an important feature of continental deformation.

The Mediterranean is one of the most studied regions of the world. In spite of this, a considerable spread of opinions exists about the geodynamic evolution and the present tectonic setting of this zone. The difficulty in recognizing the driving mechanisms of deformation is due to a large extent to the complex distribution in space and time of tectonic events, to the high number of parameters involved in this problem and to the scarce possibility of carrying out quantitative estimates of the deformation implied by the various geodynamic hypotheses. However, we think that a great deal of the present ambiguity could be removed if there were more frequent and open discussions among the scientists who are working on this problem. The meeting ofERICE was organized to provide an opportunity in this sense. In making this effort, we were prompted by the conviction that each step towards the understanding of the Mediterranean evolution is of basic importance both for its scientific consequences and for the possibleimplicationsfor society. It is well known, for instance, that the knowledge ofongoing tectonic processes in a given region and of their connection with seismic activity may lead to the recognition of middle long term precursors of strong earthquakes. The few cases of tentative earthquake prediction in the world occurred where information on large scale seismotectonic behavior was available. This led to identify the zones prone to dangerous shocks, where observations of short-term earthquake precursors were then concentrated.

The Mediterranean region represents a complex mosaic of continental, microcontinental and ophiolitic terranes, whose overall evolution has been controlled by relative movements between the African and Eurasian plates. Palaeomagnetic studies have played an important part in deciphering the sequence of tectonic events in this region. The 33 papers presented here span the full width of the Mediterranean basin and present results from Permian to Quaternary rocks.