LATE HOLOCENE ENVIRONMENTS IN ARID AND SEMIARID REGIONS OF CENTRAL-WESTERN ARGENTINA (30° - 35°S): POLLEN RECORDS AND PALEOCLIMATIC INFERENCES

ROJO, L.; VILLALBA, R.; GIL, A

VALDIVIA, CHILE

Simposio; PAGES 2010 II International symposium "Reconstructing Climate Variations in South America and the Antarctic Peninsula over the last 2000 years"; 2010

PAGES-CANTRO DE ESTUDIOS CIENTIFICOS (VALDIVIA, CHILE)

In arid and semiarid regions from central-western Argentina (30°-35°S), sparse vegetation with poor pollen production, in combination with high deposition rates of clastic sediments with abundant carbonate and sulfate cements, hamper the production of continuous, well-dated, high-resolution paleoenvironmental archives to reconstruct past changes in regional vegetation. Paleoecological and paleoclimatic records are scarce, non-continuous and of low-temporal resolution. In order to contribute to the regional paleoclimatology, a multidisciplinary study is currently in progress to reconstruct past environmental changes for the late Quaternary in central-western Argentina. In the framework of this investigation, two pollen records from the Piedmont and the plain at 33°-34°S were studied to reconstruct the vegetation history of the region during the Holocene. Our results show changes in hydrophytic plant communities during the late Holocene, attributed to the hydrological dynamics of local basins. In the La Estacada creek (33º27’S/69º03’W), two intervals with higher water availability at ca. 4000-3000 yrs BP and ca. 500 yrs BP were related to hydrophytic communities in the ��lood plain. In the Salinas del Bebedero (33º20’S/66º45’W) shallow lake, minor water level ��luctuations during the last ca. 3400 yrs BP are associated with the presence of halophytic communities. These hydrologic variations at the La Estacada and Salinas del Bebedero basins are compared with additional paleoenvironmental proxies in the area to assess the local (��luvial dynamics) or regional (climate) nature of these humid events. Paleoclimatic scenarios are proposed for subtropical central-western Argentina during the late Holocene according to the current knowledge of past vegetation and paleoclimate indicators. These scenarios are compared with paleoclimatic reconstructions from the nearby regions of Central Chile, Pampa Bonaerense and Northern Patagonia. Finally, the paleoclimatic inferences from subtropical South America are contrasted with the results from general circulation models available for the region.