Late Quaternary climate history of the Bolivian Altiplano

Sediment cores and outcrops from the Bolivian Altiplano are used to interpret late Pleistocene/Holocene paleoclimates and lake evolution based on a multi-proxy approach (ostracod content, palynology, sedimentology, and radiocarbon dating). Despite the different sensitivity of the lacustrine basins to environmental changes, interpreting the records in terms of paleohydrology, climate, and more especially timing of events is difficult. Notwithstanding these problems, Lake Titicaca in the north and Lake Pocoyu (Lake Poopo, salars of Coipasa and Uyuni) in the south reveal a similar evolution in general trends through the course of time. During the Minchin phase (until 30-26 kyr BP), the Altiplano was wetter than present. The Last Glacial Maximum (ca. 26-14 kyr BP), marked by cooler, drier conditions, was followed by a return to a wetter climate, interrupted by short arid events, between ca. 14 and 10.5 kyr BP. Another cycle of aridity, between 10.5 and 8 kyr BP, took place abruptly just after the humid Tauca phase. The mid-Holocene is interpreted as climatically unstable, with an alternation of humid and dry episodes. Since 3.9 kyr BP, wetter conditions have persisted and intensified to the present. The data are interpreted in terms of changes in inter-tropical convergence zone extension (summer precipitation) and in polar air mass intensity (winter precipitation). (C) 2000 Published by Elsevier Science Ltd and INQUA. All rights reserved.