ENVIRONMENTAL SIGNIFICANCE OF MICROFAUNAL ASSOCIATIONS IN THE PAMPEAN REGION, BUENOS AIRES, ARGENTINA.

CALVO-MARCILESE, L.; BEILINSON, ELISA; RAIGEMBORN, M. S.; CUSMINSKY, G.C.; PIAZZA, D.

Mendoza

Congreso; 4th International Paleontological Congress; 2014

International Paleontological Association

The Cantera Vignogna is a quarry located in the NE of Buenos Aires province, since the last decade vertebrate fossils have been recovered in this location, establishing an exceptional record of megafauna with a remarkable degree of preservation. Within this area, four particular sections were studied for sedimentological and facies analysis, with the aim of establishing paleonvironmental conditions during the Upper Pleistocene. The succession starts with laminated mudstones and siltstones interpreted as paludal or as marsh deposits with tidal influence, and it culminates with sandstones and silty sandstones related to fluvial channels and floodplain deposits. It is believed that accumulation of the lower units took place during highstand or transgressive base-level (or sea-level) conditions of the MIS 3 and that the upper units correspond to regressive fluvio-alluvial deposits. For the first time in this zone, calcareous microfossils (ostracods) have been collected, in order to be used as proxy for environmental reconstructions. In three of the four analyzed sections, a conspicuous association of freshwater to brackish ostracods has been registered. Even though the diversity and abundance is low, and some specimens presented signs of transport and reworking, various valves and carapaces were recovered. The ostracods assemblage is dominated by Candona sp., Cyprideis multidentata Hartmann, Cyprideis salebrosa hartmanni Ramírez and Limnocythere sp. This assemblage is common in continental to brackish environments, from truly freshwater to saline, with the presence of pools and ponds where salinity, could be higher than in the surrounding areas. These preliminary data along with additional information in process, will be significant to characterize the climate variability occurred during the MIS 3 in South America.