Historia de la vegetacion en relacion con la evolution geomorfologica de las llanuras costeras del este de la provincia de Buenos Aires durante el Holoceno

Abstract

Changes in vegetation communities of the eastern coastal plains of Buenos Aires Province during the Holocene were reconstructed based on the comparison of palynological records from two radiocarbon dated cores located north (T9-1, 36 45 S; 56 37? W) and south (La Lagunita, 37 43? S; 57 21? W) of Villa Gesell headland. Between 5,400 and 3,300 14C yr B.P. pollen records suggest the development of similar mosaics of halophytic-psammophytic communities at both sites, on tidal plains related to littoral barriers prograding simultaneously to the north and south of the Villa Gesell headland during the regressive event when sea level was stabilized. The Poaceae/Chenopodiaceae index (PCI) fluctuations suggest environmental instability as a consequence of barriers changes. From ca. 3,300 14C yr B.P. vegetation communities changed and differentiated at both sides of Villa Gesell headland simultaneously with the stabilization of the environments during the sea level regression, as it is reflected by a change in PCI with similar values and sign. To the north, at ca. 3,300 14C yr B.P. the mosaic of halophytic-psammophytic communities from environments associated to the barrier was replaced by a community placed on stabilized sand dunes associated with the advance toward the north of beach ridges of the barrier. To the south, at ca. 2,500 14C yr B.P. halophytic communities dominated by Chenopodiaceae were established reaching a higher development in a sheltered salt marsh and coastal lagoon environment, delimited by the rapid southwest progradation of the barrier. Asociacio?n Paleontolo?gica Argentina.

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