Extensional tectonics in the Amantea basin (Calabria, Italy): a comparisonbetween structural and magnetic anisotropy data

We report on structural and anisotropy of magnetic susceptibility (AMS) res ults from the Upper Miocene sediments of the Amantea basin, located on the Tyrrhenian coast of the Calabrian Are (Southern Italy). The stratigraphic s uccession of the basin is organized in three depositional sequences, separa ted by two major angular unconformities. Detailed geological mapping and st ructural analysis demonstrate that the stratigraphic evolution of the Amant ea basin is strongly controlled by a synsedimentary extensional tectonic re gime. Several NNE-SSW-trending normal fault arrays with large scatter in in clination values have been interpreted as due to a domino faulting mechanis m, consistent with a WNW-ESE stretching direction. AMS data have been obtai ned for 13 sites, both in the not constrained in age first depositional seq uence (3 sites), and in the upper Tortonian-lower Messinian clays from the second depositional sequence (10 sites). All the sites show a strong magnet ic foliation parallel to the bedding planes, and a well defined magnetic li neation subparallel to the local bedding dip directions. The magnetic linea tions cluster around a WNW-ESE trend and are parallel to the stretching dir ections inferred by fault-slip analysis and basin architecture. These new d ata then confirm the possibility to use the magnetic lineation to map the s train trajectory in weakly deformed extensional sedimentary basins. Paleoma gnetic data (from previous studies) show that the whole Calabrian block und erwent a 15 degrees-20 degrees clockwise rotation probably in the Pleistoce ne, postdating the extensional tectonic events which controlled the Amantea basin geometry. Therefore we suggest for the Amantea basin an original E-W -oriented stretching direction, which may be considered as the older extens ional direction characterizing the Late Miocene evolution of the southern T yrrhenian Sea domain. (C) 1999 Elsevier Science B.V. All rights reserved.