Lake-Level Chronology on the Southern Bolivian Altiplano (18°–23°S) during Late-Glacial Time and the Early Holocene☆

Abstract Stratigraphic analyses of outcrops, shorelines, and diatoms from the southern Bolivian Altiplano (Uyuni-Coipasa basin) reveal two major lacustrine phases during the late-glacial period and the early Holocene, based on a chronology established by radiocarbon and U/Th control. A comparison of 14 C and 230 Th/ 234 U ages shows that during times of high lake level, radiocarbon ages are valid. However, during low-water periods, 14 C ages must be corrected for a reservoir effect. The lacustrine Tauca phase started a little before 16,000 14 C yr B.P., and the lake level reached its maximum between 13,000 and 12,000 14 C yr B.P. A dry event (Ticana) occurred after ca. 12,000 and before 9500 14 C yr B.P. A moderate lacustrine oscillation (Coipasa event) occurred between ca. 9500 and 8500 14 C yr B.P., using a reservoir-corrected conventional 14 C chronology. Comparisons between the lake-level chronology in the Uyuni-Coipasa basin and data from other southern tropical areas of South America suggest that the lacustrine evolution may reflect large-scale climatic changes.