A 22,000 C-14 year BP sediment and pollen record of climate change from Laguna Miscanti (23 degrees S), northern Chile

Lake sediments and pollen, spores and algae from the high-elevation endorhe ic Laguna Miscanti (22 degrees 45'S, 67 degrees 45'W, 4140 m a.s.l., 13.5 k m(2) water surface, 10 m deep) in the Atacama Desert of northern Chile prov ide information about abrupt and high amplitude changes in effective moistu re. Although the lack of terrestrial organic macrofossils and the presence of a significant C-14 reservoir effect make radiocarbon dating of lake sedi ments very difficult, we propose the following palaeoenvironmental history. An initial shallow freshwater lake (ca. 22,000 C-14 years BP) disappeared during the extremely dry conditions of the Last Glacial Maximum (LGM; 18,00 0 C-14 years BP). That section is devoid of pollen. The late-glacial lake t ransgression started around 12,000 C-14 years BP, peaked in two phases betw een ca. 11,000 and < 9000 C-14 years BP, and terminated around 8000 C-14 ye ars BP. Effective moisture increased more than three times compared to mode rn conditions (<similar to> 200 mm precipitation), and a relatively dense t errestrial vegetation was established. Very shallow hypersaline lacustrine conditions prevailed during the mid-Holocene until ca. 3600 C-14 years BP, However, numerous drying and wetting cycles suggest frequent changes in moi sture, maybe even individual storms during the mid-Holocene. After several humid spells, modern conditions were reached at ca. 3000 C-14 years BP, Com parison between limnogeological data and pollen of terrestrial plants sugge st century-scale response lags. Relatively constant concentrations of long- disance transported pollen from lowlands east of the Andes suggest similar atmospheric circulation patterns (mainly tropical summer rainfall) througho ut the entire period of time. These findings compare favorably with other r egional paleoenvironmental data. (C) 2001 Elsevier Science B.V. All rights reserved.