PALEOHYDROLOGY OF THE LAGUNA LEJIA (NORTH CHILEAN ALTIPLANO) AND CLIMATIC IMPLICATIONS FOR LATE-GLACIAL TIMES

Paleoenvironmental and sedimentological data from Laguna Lejia (23-degrees-30'S, 67-degrees-42'W, 4325 m) in the high Altiplano of the Chilean Atacama desert indicate that climatic conditions during late-glacial times were significantly wetter than today. A water and energy budget model was used to simulate climatic scenarios that would have resulted in the observed changes in the water levels, water surfaces, water volumes and salinity during that time interval. Different climatic scenarios for the Laguna Lejia catchment include precipitation increases of over 100% up to 400- > 500 mm/yr (today 200 mm/yr) to account for the late-glacial lake levels with shorelines 15-25 m higher than at present, and a lake surface of 9-11 km2 compared to the present 2 km2. During the lake maximum about 13,500-11,300 yr B.P. finely laminated sediments consisting of Mg-calcite, diatoms and sometimes gypsum were deposited. The paleoenvironmental evidence indicates that (north)easterly wind direction prevailed, and the summer rainfall resulted from a seasonal poleward shift of the tropical circulation. The lake history of Laguna Lejia is representative for the Altiplano area between 21-degrees and 24-degrees-S.