Radiocarbon reservoir effect and the timing of the late-glacial/early Holocene humid phase in the Atacama Desert (Northern Chile)

We revise substantially the regional chronology of lake-level fluctuations from the late-glacial/early Holocene humid phase along a high altitude transect (3500 to 4500 m) between 18 degrees S and 28 degrees S in the Southwestern Altiplano of Northern Chile, Radiocarbon dates and Pb-210 profiles for limnic and terrestrial materials allow us to estimate and justify reservoir correction values for conventional C-14 dates, Our chronology suggests that the latest Pleistocene/early Holocene humid phase started between 13,000 and 12,000 C-14 Yr B.P., and that maximum lake levels were reached between 10,800 and 9200 C-14 yr B.P. This is significantly younger than what has been established so far for the Titicaca-Uyuni Basin in Bolivia. The paleolakes disappeared sometime between 8400 and 8000 C-14 Yr B.P. Our revised chronology agrees with the regional history of human occupation, and is broadly synchronous with vegetation changes in subtropical continental South America, and with the onset of wetland expansion in the northern hemisphere tropics. (C) 1999 University of Washington.