Environmental study from the Argentinian continental Shelf using modern foraminifera and ostracods as proxy data

BERNASCONI, E.; CUSMINSKY, G,

C

Simposio; International Symposium of Foraminifera Forams 2014.; 2014

Universidad de Concepción

ENVIRONMENTAL STUDY FROM ARGENTINE CONTINENTAL SHELF USING MODERN FORAMINIFERA AND OSTRACODS AS PROXY DATA. Emiliana Bernasconi1 and Gabriela Cusminsky1 1 Universidad Nacional del Comahue (CRUB-UNcoma), Consejo Nacional de Investigaciones Científicas y Técnicas (INIBIOMA-CONICET), Argentina. (e-mail: emibernasconi@yahoo.com.ar) 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. Two assemblages were recognized: the first, registered between 15 and 74 m of depth, was characterized by Buccella peruviana (d´Orbigny), Elphidium discoidale (d´Orbigny), Elphidium gunteri Cole and Ammonia parkinsoniana (d´ Orbigny) and in less proportion Quinqueloculina patagonica d´Orbigny, Pyrgo peruviana (d´ Orbigny), and Trochammina inflata (Montagu) were presented. Ostracods was represented by Callistocythere 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), Xestoleberis umbonata Whatley, Moguilevsky, Chadwick, Toy and Ramos. This assemblage reflected conditions of inner shelf with littoral species. The other assemblage was denoted in sediments to depth 80 and 130 m. The more represented species founded were Globocassidulina subglobosa (Brady), Cibicides dispars (d´Orbigny), Uvigerina peregrina Cushman, Uvigerina bifurcata d´Orbigny, Angulogerina angulosa f. occidentalis (Cushman) and in less proportion Cibicides mckannai Galloway and Wissler, Cibicides aknerianus, Ehrenbergina pupa (d´Orbigny) and Melonis affine (Reuss). Ostracods were absent. This association suggested an environment of outer shelf. These environments are strongly influenced by the different masses of water present in the continental argentine shelf. The inner shelf environment is connected by coastal waters which has low salinity due to discharge of Río Negro. While that, outer shelf environment is affected by waters from Malvinas current. From the microfauna analysis was possible to identify the physiographical zones from argentine shelf showing the importance of these microfossils in oceanographic studies.