INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
capítulos de libros
Clustering of Pleistocene rock avalanches in the Central Andes, Argentina
Cenozoic Geology of Central Andes of Argentina
Three huge rock avalanche deposits with volumes in the order of about one million cubic meters have been studied in detail at the northwestern Cordon del Plata range (32º LS). The diamictons are generally characterised by a poor sorting, but have a typical vertical succession of sediment facies. These rock avalanche events are inferred to have occurred during the Late Pliocene Middle Pleistocene based on stratigraphic relations with Pleistocene drifts previously studied along the Mendoza river valley and tephra layers overlaying both the glacial and rock avalanche deposits. The tephras have been Ar39/Ar40 dated to 350±80 Ky. This age is well correlated with the paleontological content found in one of impounded paleo-lake, consisting in dental pieces of Hyppidium sp. A high magnitude earthquake is proposed as triggering mechanism based on geomorphological evidences, clustering of the rock avalanches, and present regional seismicity. The seismic activity was related to the Carrera fault system as lacustrine sediments are intensively deformed. These findings corroborate the assumption of Pleistocene activity of the regional faults. Nevertheless, warm paleo-climate conditions during Late Pliocene-Early Pleistocene could have favoured the occurrence of these events.