Tectonics of the Umbria-Marche-Romagna Arc (central northern Apennines, Italy): New paleomagnetic constraints

Abstract

We present the results of a paleomagnetic study carried out on 32 sites from mainly Messinian clayey sediments distributed throughout the external Umbria-Marche-Romagna Arc (UMRA). These data, together with published results from coeval sediments, demonstrate that this arc is an orocline in its central northern sector. Bending, not well constrained in time, was due to about 15° clockwise rotations of the central part of this arc and to counterclockwise rotations farther north. In this latter area, post-Messinian counterclockwise rotations are of the same amplitude as those calculated for some classic Mesozoic paleomagnestic sections in northern Umbria, suggesting a Plio-Pleistocene age for the rotations reported from the older sequences.