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 elastic sediments from the frontal portions of the northern Apennines. These results are combined wit h Cenozoic data from the literature to evaluate whether rotations of units in this region are related to the Oligo-Miocene Corsica-Sardinia rotation a nd/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 countercl ockwise above a main boundary thrust onto the Adria/Africa margin. We propo se that about 24 out of a total of 52 degrees of rotation observed in the E piligurian units can be related to the Oligo-Miocene motion of the Corsica- Sardinia block, in partial agreement with previous conclusions, and the rem aining 28 degrees to the Pliocene tectonic phase at the Apennine chain fron t, which may have (re)activated thrust planes in the Adria/Africa successio n below the Ligurian wedge. (C) 2000 Elsevier Science B.V. All rights reser ved.