INVESTIGADORES
BERNASCONI emiliana
congresos y reuniones científicas
Título:
PALEOENVIRONMENTAL INFERENCES FROM ALATE QUATERNARY MARINE SEQUENCE IN SAMBOROMBÓN BAY, BUENOS AIRES (SOUTH AMERICA)
Autor/es:
ANGÉLICA BALLESTEROS PRADA; BERNASCONI EMILIANA
Lugar:
Edinburgo
Reunión:
Workshop; Forams 2018 Foraminifera in a Changing World; 2018
Institución organizadora:
Universidad Edinburgo
Resumen:
The successive glacial and interglacial events in the Quaternary influenced theposition of the coastline and helped to model the Argentine continental margins. The coastal zone of Samborombón bay is an excellent example of the deposits originated by the transgressions of the Late Pleistocene and the Holocene. With the aim of better understanding the variations occurred during the Holocene, we carry out a preliminary analysis of the Holocene benthic foraminifers from a sequence of 258 cm length, located on the margin of Channel 15 (Samborombón bay). It was dated between 5900 ± 100 years BP(252 cm) and 5550 ± 120 years BP (128cm). The sediments analyzed are mostly composed by sand and silt-sized particles. Some intermediate levels are characterized by the abundance of bivalve and gastropod shells.The fauna of foraminifers is relatively abundant (̴150 per gram of bulk sediment), although not very diverse (≤10 species). The species identified mainly belong to Order Rotaliida. The assemblages were characterized by individual of Elphidium a ff. poeyanum (Balkwill& Wright), Buccella peruviana (d´Orbigny), Ammonia parkinsoniana (d´Orbigny), Ammonia tepida Cushman, Elphidium gunteriCole, Quinqueloculina seminula(Linnaeus) and Buliminella elegantissima (d´Orbigny). The abundance and diversity presented variations along the sequence. The highest values registered at the lower levels decreased drastically towards the top; in fact in the upper 25 cm foraminifers are absent. Additionally, the foraminifer?sassemblages presented a gradual replacement of species from the base to the top. Individuals of infaunal forms such as Bulimina, Buliminella and Ammonia characterized the base of the sequence while toward the top increased the abundance of species of the genera Elphidium and Ammonia. The data reflected marginal marine environment with estuarine conditions during the late Holocene in Samborombón Bay. Salinity changes, according to the variations of abundance, diversity and the replacement of species, could be recognized. A more detailed subsequent analysis will apply a higher resolution in the paleoenvironmental interpretation.