Paleomagnetic Evidence for a Neogene Two-Phase Counterclockwise Tectonic Rotation in the Northern Apennines (Italy)

Paleomagnetic directions have been determined for a new collection of Early Oligocene and Late Miocene-Pliocene Epiligurian clastic sediments from the frontal portions of the northern Apennines. These results are combined with Cenozoic data from the literature to evaluate whether rotations of units in this region are related to the Oligo-Miocene Corsica-Sardinia rotation and/or to younger phases of deformation of the Apennine chain. When Corsica/Sardinia moved counterclockwise off the coast of France, the Ligurian units located at its front were presumably pushed eastward and rotated counterclockwise above a main boundary thrust onto the Adria/Africa margin. We propose that about 24 out of a total of 52° of rotation observed in the Epiligurian units can be related to the Oligo-Miocene motion of the Corsica-Sardinia block, in partial agreement with previous conclusions, and the remaining 28° to the Pliocene tectonic phase at the Apennine chain front, which may have (re)activated thrust planes in the Adria/Africa succession below the Ligurian wedge