Chronology of a probable neotectonic Pleistocene rock avalanche, Cordon del Plata (Central Andes), Mendoza, Argentina

Placetas Amarillas-1 rock avalanche located at 32°43′S–69°25′W was geomorphologically, stratigraphically and chronologically studied. This extraordinary event dammed a secondary gully causing the formation of a barrier-lake, indicated by relict lacustrine and diatomite deposits. Stratigraphically, its deposit is overlain by alluvial fans where three tephra layers are intercalated. Dating using Ar–Ar method of the middle ash level at 350±80 ka determined a Middle Pleistocene or older age for this event. Furthermore, the younger age of Placetas Amarillas-2 is established by relative dating techniques such as soil development and rock varnish development. The ages established in this research indicate that Placetas Amarillas-1 may be temporally correlated with the Tigre Dormido rock avalanche, suggesting that the occurrence of these rock avalanches may be related to regional neotectonic activity. Nevertheless, climatic conditions are not underestimated as the Tigre Dormido event occurred before formation of an outwash terrace related to a glaciation of Early Middle Pleistocene age.