Magnetic fabric of weakly deformed clay-rich sediments in the Italian peninsula: Relationship with compressional and extensional tectonics

Abstract

We present the results of anisotropy of magnetic susceptibility (AMS) analyses carried out in weakly deformed Neogene and Quaternary clay-rich sediments from different compressional and extensional settings of the Italian peninsula, discussing the relationships between the magnetic fabrics and the tectonic settings. A well defined magnetic lineation of tectonic origin was found in several structures. The studied cases indicate that the AMS analysis of fine-grained sediments constitutes a powerful method to better constrain the tectonic evolution of sedimentary basins, where strain markers are not available. In the extensional basins the magnetic lineation coincides almost always with the stretching direction, obtained from mesostructral analysis of faults and joints, and it is generally aligned with the bedding dip. This geometric relationship is different in the compressional basins, where the magnetic lineation is almost parallel to the bedding strike. In both the extensional and compressional environments the magnetic lineation was acquired during the early stages of deformation, when the bedding was still sub-horizontal and it was not modified by the subsequent tectonic phases.