Palaeomagnetism and tectonics in Umbria, Italy

Detailed records of palaeomagnetic directions from two Upper Cretaceous Umbrian sections are compared with the composite section compiled by Van den Berg et al. [1]. In addition to these sections, fifty-one geographically distributed sites have been studied magnetically and palaeontologically. The Late Miocene-Pliocene fold belt of the Umbrian Apennines is arcuate in outcrop, being convex toward the east. The fold axes are generally tangential to the Umbrian arc, which can be divided into a northern northwestern-trending part and a southern northeastern-trending part. Sites from the north have more westerly declinations than those from the south. The differences are significant at the 95% probability level and most probably reflect the bending of originally straight fold axes or the development of fold axes with initial curvature. The palaeomagnetic directions from Umbria provide important information concerning the Umbrian tectonic deformation, but are not applicable to the Italian autochthon.