Late Holocene paleolimnological reconstructions in the Pampa plain, south of South America: regional paleoclimatic inferences from multiple shallow lake records

STUTZ, S.M.; NAVARRO, D.; TONELLO, M.S.; HASSAN, GABRIELA SUSANA; PEÑA, L; RAYÓ, M.C.; GONZÁLEZ SAGRARIO, M.A.; FONTANA S.L.; DE FRANCESCO, CLAUDIO GERMÁN; CRISTINI, PAULA ANDREA; TIETZE, ELEONOR; FERRERO, L.; GARCÍA-RODRIGUEZ, F.; BOREL, C.M.

Glasgow

Simposio; International Paleolimnology Symposium IPS2012; 2012

To reconstruct the late Holocene environmental history of the southeastern Pampa plain of Argentina (37°-38°S; 57°-58°W), in the context of regional Holocene paleoclimatic changes, a multi-proxy analysis was performed. Diatoms, charcoal, plant macro-remains and associated fauna, mollusks, ostracods, pollen and non pollen palynomorphs (NPPs) were analyzed from four shallow lakes. Similar patterns of variation of the proxies in the analyzed lake-records indicate the presence of a climatic control at a regional scale. Three phases in the evolution of the lakes were recognized. Between ca. 4500 and ca. 700 cal yr. BP, a clear macrophyte-dominated phase, with charophytes and brackish-freshwater diatoms, ostracods and NPPs (dinocysts and crustacean eggs), can be described in a context of regional arid conditions indicated by high percentages of Chenopodiaceae in the pollen record. After ca. 700 cal yr. BP the lakes changed gradually towards turbid phytoplankton-dominated conditions, with chlorococales and freshwater diatoms and a pollen record dominated by emergent macrophytes in a regional more humid context. Modern even more turbid conditions have recently established due to re-suspended sediments and a regimen of periodic droughts. The shift between lake phases may be attributed to a climatic change occurred at ca. 700 cal yr. BP towards wetter conditions after the Medieval Climate Anomaly. Even though each record is primarily representing local conditions, the joint analysis of a network of lakes has shown great potential in deciphering regional climatic and hydrological changes.