Large scale rockslides in the Argentinean Andes. Distribution and forcing factors

摘要

The interplay of processes acting over long to short time scales, which drive mountain building and erosion, condition the occurrence of rockslides. Due to the active geodynamic setting in the Central Andes and its southern limit towards the Patagonian Andes (24°S–38°S), large rockslides are wide spread; south of 38°S their occurrence decreases significantly. The aim of this work is to review the distribution and forcing factors of those large scale slope failures, which are mostly located in three regions. 1) Between 24°–27°30’S: large slope failures were observed on deeply incised narrow valleys and steep fault-bounded mountain fronts. Rockslides volumes reach 0.44 km3. They involved granites, metamorphic and sedimentary rocks. Quaternary tectonic activity along reverse faults has played a major role in the development of these slope collapses. 2) Between 30°–33°S, 38 rockslides with volumes up to 1.6 km3 are observed. Failure occurred both in glacial and fluvial valleys, as well as in mountain fronts. Most of the rockslides developed along or within 1 km of main tectonic structures. Some of which were related to post-glacial climatic conditions. 3) Between 36°–38°S, corresponding to the transition between the Central and Patagonian Andes, ∼45 rockslides developed in glacial and fluvial valleys. Neotectonic activity was proposed here as being responsible for the generation of rockslides with volumes up to 4 × 10~9 m~3. Large scale rockslides in the Argentinean Andes tend to occur in zones where the combination of tectonic deformation (past and quaternary), relief and seismicity results in favorable conditions for failure.