Holocene palaeoenvironmental evolution of the Pampa coastal plain (Argentina) based on calcareous microfossils.

MELINA MÁRQUEZ; LAURA FERRERO; GABRIELA C. CUSMINSKY

REVISTA BRASILEIRA DE PALEONTOLOGIA

SOC BRASILEIRA PALEONTOLOGIA

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

1519-7530

In the present contribution, we studied assemblages of benthic foraminifers, ostracods and charophytesin a Holocene outcrop in the southeast of the La Pampa coastal plain in Argentina. The main species recorded wereSpirillina sp. A, Buccella peruviana, Ammonia parkinsoniana, A. tepida, Elphidium margaritaceum and E. gunteri amongforaminifers, Limnocythere cusminskyae and Cyprideis salebrosa among ostracods. These species allowed to determinerestricted environments characterized by signifi cant changes in salinity. Qualitative and quantitative studies conducted onthe faunal content in the outcrop allowed to identify four environments closely linked to the sea-level changes occurredduring the Holocene. In a fi rst stage, between 7500-7200 and 6300-6200 cal yr BP represent the development of a non-marineenvironment. Around 6300-6200 cal yr BP this environment change to brackish-estuarine with moderate energy. Sometimebefore c. 6000-5700 cal yr BP a clear-water lagoon, probably oligohaline, with abundant submerged vegetation is inferred.In a fi nal stage, from 2300-2000 to 2000-1700 cal yr BP, a continental environment not infl uenced by the proximity of thesea was established. The new calcareous microfossils evidences and the new chronologies provided by this work, allowed usto adjust the moment of the maximum sea level rise during the Holocene transgression and contribute to a better knowledgeof the evolution of coastal paleoenvironments in relation to sea level changes.