Fluvial piracies in the NE sector of the Sierra de Aconquija (Tafí valley, NW Argentina)

Abstract

The Sierra de Aconquija is a recently uplifted mountain chain in NW Argentina. The NE side of the sierra is drained by the Muñoz and Los Alisos rivers – whose base level is the Las Carreras Depression that is located to the SW of the Tafí valley. Two of the major headwaters of the Muñoz River suffered during its Holocene development from piracy by the Los Alisos River. These piracies had important consequences on the size of both basins and the functioning of their alluvial fans. The main causes of the captures were changes in river dynamics during Lateglacial and Holocene glacial events. Neotectonic activation does not seem to be the most determining factor, although there are active Holocene faults nearby (Las Carreras Fault 2). Geomorphological and human occupation data recovered from the alluvial fans enables us to estimate that the most recent capture was produced during the Late Holocene.