Wetlands and Paleolakes in the Hyperarid Atacama Desert During the Late Quaternary and Their Implications for Early Human Occupation of South America

The hyperarid Atacama Desert has long been considered a natural barrier to human dispersal. However, several archaeological sites dating from the late Pleistocene have been recently reported on, and other as yet unpublished evidence is rapidly accumulating. It has been established that these occupations were facilitated by increased fluvial activity and biologically productive riparian ecosystems along the western slope of the Andes, and that the presence of humans disappeared with declines in this water flow. The considerable evidence for regional stream flow suggests that basins and lowlands should have contained lakes or wetlands contemporaneous with the ages of the fluvial activity, but there has been no published data on late Quaternary lakes in the region. Here, we report on our observations that possibly many present day salars (salt covered basins) were fresh water lakes and marshlands during the Central Andean Pluvial Event (CAPE) that occurred during the late Pleistocene and early Holocene. We performed radiocarbon analysis of described stratigraphic profiles on paleo-shorelines or in paleo-lake basins that lie within the Pampa del Tamarugal (PDT) basin. We additionally described gastropods, plant remnants, phytoliths and diatomea, which provide a reliable source for paleoenvironmental facies interpretation. These data indicate that a paleolake existed at the location of the present-day Salar de Bellavista, and that wetlands (and possibly lakes) were present at the Salar de Llamara and Pintados. These past aquatic systems are coeval with the activation of the riparian systems of the PDT reported by previous studies. Furthermore, they would have contributed to a starkly different set of resource constraints for early inhabitants than the inhospitable conditions existing today. Additionally, the presence of these water sources provides guidance in the search for additional evidence of human occupation in the region, and for understanding the geographical connections that existed among these earliest inhabitants of the Western Hemisphere.