FORAMINÍFEROS Y OSTRÁCODOS DE SEDIMENTOS RECIENTES DEL ESTUARIO DE BAHÍA BLANCA, ARGENTINA

CUSMINSKY GABRIELA; MARTÍNEZ DINA; BERNASCONI EMILIANA

REVISTA ESPANOLA DE MICROPALEONTOLOGIA

Instituto Geominero de España

Lugar: España; Año: 2006 vol. 2-3 p. 395 - 410

0556-655X

[Foraminifera and Ostracoda of recent sediments from the Bahía Blanca estuary, Argentina]. The results of qualitative and quantitative analysis applied to the assemblages of foraminifers and ostracods from surface sediments are presented. The samples were extracted from the channel Tres Brazas, Bahía Blanca estuary, Argentine. The analyzed sectors were tidal flats, accretion flank and erosion flank. In tidal flats Ammonia beccarii predominates, characterizing a restricted environment with variable salinities. The most abundant ostracod species are Loxocythere variasculpa, Neocythereis ruidis and Cyprideis salebrosa hartmanni, reflecting unstable environmental conditions; the ostracod density and the high percentage of juveniles valves indicate an environment of low energy. In the accretion flank the foraminifers appear with  high densities, with a predominance of Ammonia beccarii and Elphidium discoidale; the ostracod fauna decreases and Callistocythere litoralensis, Hemicytherura escobasensis and Semicytherua rugosareticulata dominate. These assemblages suggest an estuarine to littoral shallow depth environment characterized by the increase of the sedimentary dynamics and a more stable salinity. In the erosion flank, Buccella peruviana f. campsi increases, suggesting less restricted conditions as well as the presence of live individuals of euhaline species, like Callistocythere litoralensis, Hemicytherura chuiensis and Cytheretta punctata indicate an environment with greater energy. These sector would correspond to older sediments suffering erosion that could be indicative of  sea level oscillations.