Ostracodes as indicators of Late Quaternary lake levels of Lago Cardiel, Southern Patagonia, Argentina.

CUSMINSKY, G; SCHWALB, A; MARKGRAF, V; GILLI, A; ARIZTEGUI, D; ANSELMETTI, F

Brasilia

Simposio; 16 th International Symposium on Ostracoda; 2009

University of Brasilia

  Southern South America is a key region to study the interactions between the Southern Westerlies and Easterlies, both bringing variable amounts of precipitation to Patagonia causing lake levels to rise and fall during the Late Quaternary. Multi-proxy analysis of an about 11 m long sediment core from Lago Cardiel (49°S, 76 m water depth, 379 km2 area, ~ 10 km east of the Andean cordillera) shows that the lake underwent drastic changes in lake level during the past approximately 15,500 years. According to previous studies of modern ostracode assemblages in Patagonia,  qualitative and quantitative analysis of species assemblages show  three lacustrine ostracod  associations downcore:  Association 1 (15,500 – 12,300 yr BP) is composed of Limnocythere rionegroensis  Cusminsky and Whatley and suggests a small and saline lake; Association 2 (12,300 – 9400 yr BP) comprises  Limnocythere patagonica   Cusminsky and Whatley, Kapcypridopsis megapodus Cusminsky et al., Eucypris fontana (Graf) and  Eucypris virgata Cusminsky and Whatley, suggesting a large and deep lake;  and Association 3 (past 9400 years) is dominated by  E. fontana  and minor numbers of Limnocythere rionegroensis and L. patagonica indicating a decrease in lake level to about modern values. We suggest that the highstand of Lago Cardiel is related to higher levels of precipitation caused by enhanced incursions of Easterly moisture when Southern Westerlies were weak between 12,300 and 9400 yr BP.