Mid- to Late Holocene vegetation and palaeoenvironmental conditions at the coastal wetlands, Buenos Aires, Argentina

VILANOVA I ; PRIETO AR

Bonn, Alemania

Congreso; 12th International Palynological Congress (IPC-XII); 2008

Steinmann Institute, Division of Paleontology,University of Bonn

In the light of widespread evidence for global climate and sea level change, reconstructing Holocene coastal vegetation history and palaeoenvironmental conditions occupies a central role in the effort to predict future responses of both vegetation communities and environmental conditions to the accelerating sea-level rise and climatic changes. The palynological analysis of sedimentary sequences, which were deposited during the Holocene sea-level highstand (6500 – 6000 14C yr BP) at the Buenos Aires coastal wetlands (35° 50’ – 35° 55’ S), can be an analogue to explain potential modifications in the vegetation and environmental conditions due to sea level rise. In order to reconstruct the Holocene vegetation and palaeoenvironmental conditions in the coastal wetlands, two mid- to late Holocene records were analyzed. One corresponds to an exposed sequence at the Salado River (35° 55’ S - 57° 53’ W; 5 m. a s. l.) located 30 km at the west of present shoreline. The other is from a core retrieved from the inner shelf (36° 45´ S; 56° 37´ W; 13 m b. s. l.), 4 km at the east of the shoreline. The record from Salado River shows that before ca. 5870/5640 14C yr BP halophytic communities developed on tidal flat that increased in diversity in relation to stabilized estuarine conditions. Between ca. 5870/5640 and ca.1800 14C yr BP, fluvial input is reflected by the rise of hydrophytic types suggesting the development of brackish-freshwater bodies. The core record suggests a mosaic of halophytic– psammophytic communities in marine-brackish environments associated to littoral barriers between ca. 5360 and 3300 14C yr BP. After ca. 3300 14C yr BP, these communities were replaced by vegetation of stabilized sand dunes and a major change in dinocyst abundance and diversity indicates that a normal inner neritic environment was establishing in the present innershelf area. These results show the spatial and temporal variability in vegetation and palaeoenvironmental  conditions as a consequence of the geomorphological evolution related to sea-level changes from ca. 6500 14C yr BP.