ENVIRONMENTAL STUDY FROM THE ARGENTINEAN CONTINENTAL SHELF USING MODERN FORAMINIFERA AND OSTRACODS AS PROXY DATA

BERNASCONI EMILIANA; CUSMININSKY GABRIELA

Concepción

Simposio; INTERNATIONAL SYMPOSIUM ON FORAMINIFERA (FORAMS 2014); 2014

Universidad Nacional de Concepción

Foraminifers and ostracods are microorganisms, which due to their specific environmental requirements, are used as bio-indicators of marine environments. In this study, we evaluated modern sediments from Argentine continental shelf (35° 20´ - 39° 04´ S and 58° 43´ - 55° 33´ W), which were extracted between 15 and 130 m of depth, in order to understand their distribution patterns and ecological preferences. We detect 61 species of foraminifers corresponding to Orders Rotaliida, Miliolida, Lagenida, Buliminida, Lituolida and Trochamminida. With respect to the distribution of ostracods, 18 species belonging to Superfamily Cytheridae were recognized. Between 15 and 74 m of depth, an assemblage represented especially by Buccella peruviana (d´Orbigny), Elphidium discoidale (d´Orbigny), Elphidium gunteri Cole and Ammonia parkinsoniana (d´ Orbigny) and the ostracods: Callistocytoere litoralensis (Rossi de García), Ambostracom cf. bertelsae (Sanguinetti, Ornellas and Coimbra), Oculocytheropteron macropunctatum Whatley, Chadwick and Toy, Argenticytheretta levipunctata Sanguinetti, Ornellas and Coimbra, Keigia falklandi (Brady) and Xestoleberis umbonata Whatley, Moguilevsky, Chadwick, Toy and Ramos was determinate. Species of genus Elphidium and Ammonia parkinsoniana are typical of brackish and coastal waters and the ostracods corresponding to littoral species that reflects a shallow environment of inner shelf. A second assemblage was recognized between 80 and 130 m, only forams were present. The foraminifers founded were Globocassidulina subglobosa (Brady), Cibicides dispars (d´Orbigny), Uvigerina peregrina Cushman, Uvigerina bifurcata d´Orbigny, Angulogerina angulosa f. angulosa (Williamson), Ehrenbergina pupa (d´Orbigny) and Pullenia subcarinata subcarinata (d´Orbibny). All these species are typical of cold waters, reflecting an environmental with typical salinity content of subantartic waters of the outer shelf. From the microfauna analysis, in the study area, two water masses can be distinguished: the coastal zone water, which is influence by the discharge of Río Negro and the waters from the outer shelf corresponding to Malvinas current.