Paleoecology of Foraminfera from a Holocene sequence cropping out at Las Brusquitas creek, Buenos Aires, Argentina

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

Mendoza

Congreso; 4th International Paleontological Congress; 2014

International Paleontological Asociation

PALEOECOLOGY OF FORAMINIFERA FROM A HOLOCENE SEQUENCE CROPPING OUT AT LAS BRUSQUITAS CREEK, BUENOS AIRES, ARGENTINAMelina Márquez1, Laura Ferrero1 and Gabriela C. Cusminsky21. Instituto de Geología de Costas y del Cuaternario UNMDP, IIMyC-CONICET,Funes 3350, Mar del Plata, 7600, Argentina. mmarquez@mdp.edu.ar2. Centro Regional Universitario Bariloche. Universidad Nacional del Comahue. INIBIOMACONICET.Quintral 1250, Bariloche, 8400, Río Negro, Argentina.Foraminifera associations from sediments cropping out at Las Brusquitas Creek, in the southeastern coast of the Pampas of Argentina, were studied in order to provide evidence of Holocene paleoenvironmental evolution and its probable relationship with the last transgressive-regressive cycle. The most frequent and abundant species were Ammonia parkinsoniana (d?Orbigny), Ammonia tepida (Cushman) and Buccella peruviana(d?Orbigny). Qualitative and quantitative analyses allowedthe recognition of three main stages in the palaeonvironmental evolution of the studied sequence. In ca. 6400 years BP, foraminifera were very scarce, but based upon previous studies estuarine and low salinity conditions would have prevailed. In a second stage deposited between caless diverse foraminifera associations, revealing the evolution towards brackish-fresh water, lowenergy and more restricted environments. This last phase may be explained by the onset of the sand-dune barrier during the regressive phase of the Holocene transgression. Finally, the record was buried by dune sands partially modified by soild development.