Holocene Paleoenvironmental evolution of the Pampa Coastal plain (Argentina) based on calcareous microfossils

MARQUEZ, MELINA; FERRERO, L; CUSMINSKY , G. C.

REVISTA BRASILEIRA DE PALEONTOLOGIA

SOC BRASILEIRA PALEONTOLOGIA

Lugar: Porto Alegre; Año: 2016 vol. 19 p. 25 - 40

1519-7530

ABSTRACT - In the present contribution, we studied assemblages of benthic foraminifera, ostracods and charophyceae in a Holocene outcrop in the southeast of the Pampa coastal plain in Argentina. The main species recorded were, Spirillina sp. A, Buccella peruviana, Ammonia parkinsoniana, Ammonia tepida, Elphidium margaritaceum and Elphidium gunteri among foraminifera, Limnocythere cusminskyae and Cyprideis salebrosa among ostracods. These species allowed determining restricted environments characterized by significant changes in salinity. Qualitative and quantitative studies conducted on the faunal content in the outcrop allowed identifying four environments closely linked to the sea-level changes occurred during the Holocene. In a first stage, between 7500-7200 and 6300-6200 cal yr BP represent the development of a non-marine environment. Around 6300-6200 cal yr BP this environment change to brackish-estuarine with moderate energy. Sometime before c. 6000-5700 cal yr BP a clear-water lagoon, probably oligohaline, with abundant submerged vegetation is inferred. In a final stage (from 2300-2000 to 2000-1700 cal yr BP), a continental environment not influenced by the proximity of the sea was established. The new calcareous microfossils evidences and the new chronologies provided by this work allowed us to adjust the moment of the maximum sea level rise during the Holocene transgression and contribute to a better knowledge of the evolution of coastal paleoenvironments in relation to sea level changes.