MAGNETIC FABRIC OF WEAKLY DEFORMED CLAY-RICH SEDIMENTS IN THE ITALIANPENINSULA - RELATIONSHIP WITH COMPRESSIONAL AND EXTENSIONAL TECTONICS

We present the results of anisotropy of magnetic susceptibility (AMS) analyses carried out in weakly deformed Neogene and Quaternary clay-ri ch sediments from different compressional and extensional settings of the Italian peninsula discussing the relationships between the magneti c 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 sedime ntary basins, where strain markers are not available. In the extension al basins the magnetic lineation coincides almost always with the stre tching direction, obtained from mesostructral analysis of faults and j oints, and it is generally aligned with the bedding dip. This geometri c relationship is different in the compressional basins, where the mag netic 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 tectoni c phases.