Abstract

Large-scale hydrological changes had major impacts on the vegetation of the Atacama Desert during the late Quaternary. Rodent middens (accumulations of feces, plant remains, insects and bone) have proven fundamental for reconstructing the magnitude and chronology of these impacts. To date, the vast majority of these studies come from the northern and central Atacama Desert with little data from the southern portion, which has a stronger winter rainfall influence. We collected 31 middens from Quebrada Incahuasi (QIN, 25°36’S, 3600 masl) a high elevation valley that sits across the boundary between the Andean steppe and the absolute desert. We identified plant macrofossils: fruits, seeds, flowers and leaves as well as plant cuticles from rodent pellets. AMS radiocarbon dates reveal that the QIN middens span the interval between 17 ka to the present almost continuously. A total of 16 taxa were identified, many of which are extralocal. Just three species occur in a midden dated to 17 ka implying a cold and arid climate. Diverse assemblages indicated increased available moisture at 15 ka and lasting until 10 ka. These data replicate the timing of the Central Andean Pluvial Event (CAPE) and extend its influence south of the central Atacama. Only minor changes in midden assemblages occurred during the Holocene with the most important changes seen at 2 ka, when modern assemblies were established. By comparing the QIN midden series to similar records from lower elevation, we reconstruct the migrational history of high Andean steppe during the late Quaternary