Vegetation and climate dynamics in southern South America: The microfossil record of Laguna Potrok Aike, Santa Cruz, Argentina

Pollen and diatom assemblages of the sediment record from Laguna Potrok Aike provide new data about the vegetation and climate history since 16,100 cal BP of the drylands in the Patagonian Steppe, some 80 km east of the Andes on the southernmost Argentinean mainland. In combination with formerly published geochemical sediment proxies it is shown that during the Late Glacial the steppe was cold, wind speeds were low and available moisture was high. Pollen, diatoms and geochemical parameters record increasing temperatures and decreasing moisture availability resulting in falling lake levels in the steppe culminating in the lowest lake levels around 7640 cal BP. Contemporaneously, Andean Forest established in the mountains and probably wind speeds increased. Between 6000 and 2300 cal BP the pollen record points to cyclic seasonality fluctuations in the steppe and the Andes. After 2300 cal BP the research area became increasingly humid and the Andean Forest underwent changes in floristic composition. Sheep breeders arrived in the 19th century, and in the 20th century conditions in the steppe area became drier.