A high-resolution pollen and diatom record from Laguna Los Polulos (22°36’S/66°44’W/4500 masl), NW Argentinean Puna, since ca. 800 AD

LILIANA LUPO1, MARCELO MORALES2, ANTONIO MALDONADO3, MARTIN GROSJEAN4

Malargüe

Simposio; Reconstrucciones Regionales de las Variaciones Climáticas en América del Sur durante el Holoceno tardío: Una nueva Iniciativa de PAGES; 2006

Pollen and diatom data from Laguna Polulos are presented. L. Polulos is a brakish-saline highland lake surrounded by high Andean grasslands with a low vegetation cover (ca. 10-15%). The 120 cm long sediment core has a basal age of  ~550 AD (14C y 210Pb). The pollen record, analysed every 1 to 11 cm, shows several periods with dominance of littoral vegetation, which is interpreted as periods with low lake levels between 1870-1700, 1500-1400, and 1050-650 AD; and humid periods as suggested by the presence of pollen from regional terrestrial vegetation with a maximum between 1700 and 1500 AD. A trend towards more brackish conditions is suggested by the increase of Pediastrum abundance in the pollen spectrum since 1910 AD. The diatom record (analysed every 2 cm) shows similar general trends, with strong short-term variability and strong lake level shifts (decadal scale; within 10-15 years). High lake levels are recognized, by benthic to plankton ratios, during the last 100-150 years, between 1660 and 1590 AD and circa 666 AD. Dry moments occurred between 1540 and 1310 AD. We discuss the relationship of these results with previously published paleoenvironmental information from the Andean region, and with broader scale climatic changes as during the Little Ice Age (LIA) and Medieval Climatic Anomaly chronozones.