FLUCTUACIONES EUSTÁTICAS DURANTE EL HOLOCENO A PARTIR DEL REGISTRO DE PALEOMICROPLANCTON; ARROYO NAPOSTÁ GRANDE, SUR DE LA PROVINCIA DE BUENOS AIRES

Silvia C. Grill, Mirta E. Quatrocchio

Abstract


"Holocene palaeomicroplankton from arroyo Napostá Grande, southern Buenos Aires province, was studied and its palaeoenvironmental trends inferred. Six depositional sequences (1 to VI) are characterized by marine palaeomicroplankton content. The marine palaeomicroplankton assemblage is dominated by: Operculodinium centrocarpum and Spiniferites Group (Spiniferites multibrevis, Spiníferites ramosus, Spiniferites membranaceus and Spiniferites sp.); with Dapsilidinium sp. and acritarchs (Michrystridium sp., Cymatiosphaera sp. and Baltisphaeridium sp.). By comparison of palaeomicroplankton fossil genera with living ones a neritic/estuarine palaeoenvironment was inferred. The most important sea level change associated to a higher dinocysts diversity was found at 6000 and 5580 years BP. The marine influence ended around 3000 years BP. From that moment until present, retraction of sea is evidenced by the dominance of sporomorphs in the palynomorph association. These conclusions agree with those obtained by other authors from microfossils and isotope analysis."

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