Tectonic rotations in the Tyrrhenian arc system during the Quaternary and late Tertiary

In the Central Mediterranean area, one of the most interesting geodynamical processes on our Earth takes place: the vertical sinking of a (northwest-ward dipping) lithosphere fragment results in the outward movements of continental blocks, thereby creating the Tyrrhenian arc system, This arc system comprises Sicily, Calabria and the southern part of peninsular Italy (Campania, Basilicata, Apulia), This process started in late Miocene times and caused the opening of the Tyrrhenian basin. The Tyrrhenian area is the source area for the continental blocks. In the rocks which were formed during this process the occurrence of tectonic rotations is to be expected. Earlier paleomagnetic results from Mesozoic to Eocene sediments show a pattern of major (100-140°) clockwise rotations in the southwestern part of the arc (Western Sicily) and major counter-clockwise rotations (30-100°) in the northeastern part of the arc (southern Apennines and northern Calabria). Most of these workers interpret the tectonic rotations as late Tertiary events. It is the aim of the present study to establish the (absence/presence of) tectonic rotations in sediments that were formed during this late Tertiary arc development, and hence to determine age estimates (timing and duration) for these rotations. This is essential because paleomagnetic directions in rocks only reflect the sum rotation of the underlying unit; interpretation of paleomagnetic results in terms of rotation events is only possible if one knows the tectonic rotation of the younger rocks in the same area.