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Abstract: The present-day arcuate shape of the Calabrian Arc has been accomplished during Neogene and Early Pleistocene by large and opposite vertical axis rotations along the two arms of the Arc. Clockwise (CW) rotations have been systematically registered in Sicily and Calabria, whereas counterclockwise (CCW) rotations were measured in Southern Apennines. Such opposite vertical axis rotations ceased in the uppermost part of the Lower Pleistocene (about 1 Ma ago) along almost the entire Calabrian Arc and are not observed in the present-day GPS velocity field. The end of the Calabrian Arc bending during the Quaternary marks a decrease in the efficiency of the tectonic processes related to the long-lived subduction of the Ionian slab, which caused the halting of the back-arc opening in the Southern Tyrrhenian Sea. [Copyright &y& Elsevier]

Abstract: New paleomagnetic results from Neogene sedimentary sequences from the Betic chain (Spain) are here presented. Sedimentary basins located in different areas were selected in order to obtain paleomagnetic data from structural domains that experienced different tectonic evolution during the Neogene. Whereas no rotations have been evidenced in the Late Tortonian sediments in the Guadalquivir foreland basin, clockwise vertical axis rotations have been measured in sedimentary basins located in the central part of the Betics: the Aquitanian to Messinian sediments in the Alcalà la Real basin and the Tortonian and Messinian sediments in the Granada basin. Moreover, counterclockwise vertical axis rotations, associated to left lateral strike-slip faults have been locally measured from sedimetary basins in the eastern Betics: the Middle Miocene to Lower Pliocene sites from the Lorca and Vera basins and, locally, the Tortonian units of the Huercal-Overa basin. Our results show that, conversely from what was believed up to now, paleomagnetic rotations continued in the Betics after Late Miocene, enhancing the role of vertical axis rotations in the recent tectonic evolution of the Gibraltar Arc. [Copyright &y& Elsevier]

Abstract: In extensional sedimentary basins fine-grained sediments that appear undeformed at the outcrop scale can carry a magnetic fabric consistent with the regional deformation pattern. The origin of the magnetic lineation, which is often found in extensional basins, is not yet well understood. In clays from extensional basins in southern Italy, the magnetic lineation is tectonically controlled and oriented perpendicular to the main normal faults. A combined analysis of magnetic and mineral fabrics was made to gain insight into the processes that lead to a lineation in extensional settings. Low-field, high-field and low-temperature susceptibility measurements were used to distinguish the ferrimagnetic and paramagnetic contributions to the magnetic susceptibility and its anisotropy. The magnetic anisotropy of the sediments is predominantly carried by paramagnetic phyllosilicates. Neutron texture analysis was used to evaluate the spatial distribution of chlorite basal planes. Results demonstrate that the orientation of the magnetic lineation is related to the spatial distribution of chlorite, lying parallel to the common axis of differently oriented basal planes. A quantitative correlation between the magnetic and rock fabric was made comparing the low- and high-field magnetic anisotropy (AMS, HFA) to the theoretical anisotropy calculated from the chlorite-preferred orientation. A good linear correlation is found between the degree of theoretical anisotropy and the AMS and HFA. Results show that the integrated approach of magnetic and mineral fabric investigations represents a valid alternative tool for detecting grain scale and regional deformation patterns in weakly deformed extensional basins, where macroscopic evidence of deformation is often not visible. [Copyright &y& Elsevier]

Abstract: Dikes provide important information on the structure, state of stress and activity of a volcano. Mt. Somma borders part of the Vesuvio cone (Italy), displaying ∼100 dikes emplaced between ∼18 and 30ka. Field, AMS (anisotropy of magnetic susceptibility) and thin section analyses are used to characterize their geometry and kinematics (direction and sense of flow). The dikes mostly have a NNW–SSE to NE–SW strike. Approximately 57% are radial to the older Somma edifice, ∼27% are oblique and ∼16% tangential. Among the latter two groups, ∼32% are outward dipping and ∼11% inward dipping. The dike thickness varies between 0.2 and 3m, with a mean value of 1.17m. The kinematics of 19 dikes is determined through a combination of field (8 dikes), AMS (16 dikes) and thin section analyses (15 dikes). Thirteen dikes have a vertical upward flow, whereas six have an oblique-subhorizontal flow, suggesting a lateral propagation from the summit or eccentric vents of the former Somma edifice. These propagation paths differ from those deducible from the recent activity, as all the seven major fissure eruptions between 1631 and 1944 were related to the lateral propagation of radial dikes. We propose that these different behaviours in dike propagation may be mainly related to the opening conditions of the summit conduit. The laterally propagating dikes in 1631–1944 formed with an open conduit. Conversely, the vertically propagating dikes may have formed, between 18 and 30ka, with a closed conduit. [Copyright &y& Elsevier]