Late Holocene to recent palynological and stable isotope from eastern coastal plain, Argentina

VILANOVA, I.; MALAMUD-ROAM, F.; INGRAM, B.L.; YANG, W; CLEDÓN, M

Budapest, Hungría

Congreso; 8th European Palaeobotany and Palynology Conference; 2010

Hungarian Natural History Museum

Late Holocene to recent palynological records were analyzed anDcompared with C and N stable isotopes in order to establish vegetation dynamics from wetlands located in the eastern coastal plains of Buenos Aires, Argentina. Calibration of the modern palynological spectra and stable isotope values from surface sediments to the natural plant zonation in the wetlands provided a basis for inferring late Holocene vegetation dynamics from sedimentary records. A 130 cm sediment core collected 1.5 km from the present shoreline (35° 58’ 19’’ S; 57° 23’ 38’’ W) encompasses the last 1600 14C yr BP. The core contains fossil records that reveal a trend from a co-dominance of Poacee and Chenopodiaceae ca. 1097 14C yr BP toward the dominance of Chenopodiaceae occurring recently, indicating a transition from a low brackish marsh to the establishment of a high salt marsh. This trend may reflect ecological succession related to accreationary and geomorphological processes associated with highly dynamic environment with water channels crossing throughout the wetland area. Stable C isotope values also trended from higher to lower values (d 13C = -19 to -25 ‰) consistent with increasing Chenopodiaceae dominance toward the present. C/N ratio increased toward the present from 9 to 20 possibly related to diminishing marine contribution as ecological succession took place. These results demonstrate that fossil and isotopic proxies are complementary and enhance palaeoecological interpretations