Based on the mesostructural analysis of deformed conglomerates discussed in the present note, the Tortonian-Quaternary stress evolution is reconstructed for a large sector of the external Southern Alps. Based also on the literature concerning the Late Cenozoic Tectonic Stratigraphy of the ESA, an older NNW-SSE trending compressional event has been documented in Serravallian-Tortonian times. Furthermore, if we consider the Present-day seismicity of the broader area, the complex evolution of the stress regime probably affecting the entire Eastern Southern Alps from Serravallian to Present can be depicted. Accordingly, it is clear that the stress trajectories of the sigma 1 axis changed several times during this period, though always remaining in the fourth azimuth quadrant. However, it seems that these variations were associated to repeated rotations of the principal axis from a mean NNW-SSE to NW-SE direction and vice versa. This behaviour, characterised by rapid and frequent flipping of the principal horizontal stress axes, has been already described by in the Central Apennines where Quaternary crustal extension occurs. Although the ESA from Serravallian onwards were always affected by a compressional regime, we can claim for the Twist Tectonics as a governing mechanism. Moreover, by comparing the above described tectonic evolution with the convergence direction between Adria-Africa and Europe plates from Tortonian onwards, it is clear that 'local' perturbations of the stress field have occurred in this region of ongoing crustal collision, possibly due to accomodation processes of the Adria indenter.
Neogene-Quaternary twist tectonics in the eastern Southern Alps, Italy
CAPUTO, Riccardo;
2003
Abstract
Based on the mesostructural analysis of deformed conglomerates discussed in the present note, the Tortonian-Quaternary stress evolution is reconstructed for a large sector of the external Southern Alps. Based also on the literature concerning the Late Cenozoic Tectonic Stratigraphy of the ESA, an older NNW-SSE trending compressional event has been documented in Serravallian-Tortonian times. Furthermore, if we consider the Present-day seismicity of the broader area, the complex evolution of the stress regime probably affecting the entire Eastern Southern Alps from Serravallian to Present can be depicted. Accordingly, it is clear that the stress trajectories of the sigma 1 axis changed several times during this period, though always remaining in the fourth azimuth quadrant. However, it seems that these variations were associated to repeated rotations of the principal axis from a mean NNW-SSE to NW-SE direction and vice versa. This behaviour, characterised by rapid and frequent flipping of the principal horizontal stress axes, has been already described by in the Central Apennines where Quaternary crustal extension occurs. Although the ESA from Serravallian onwards were always affected by a compressional regime, we can claim for the Twist Tectonics as a governing mechanism. Moreover, by comparing the above described tectonic evolution with the convergence direction between Adria-Africa and Europe plates from Tortonian onwards, it is clear that 'local' perturbations of the stress field have occurred in this region of ongoing crustal collision, possibly due to accomodation processes of the Adria indenter.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
