Ostrea stentina Payraudeau, 1826 found in a marine deposit of Middle-Late Pleistocene in the south of Buenos Aires province, Argentina

CHARO MELISA; ACEÑOLAZA, GUILLERMO; CAVALLOTTO, JOSE LUIS

CABA

Encuentro; I Meeting of Systematics, Biogeography and Evolution A joint effort in the Coronavirtual Era; 2020

This is the first time a marine deposit of Ostrea stentina found in the south of Buenos Aires Province, Argentina is reported. This littoral deposit dates to the Middle ? Late Pleistocene and is located near Channel Villalonga in the Anegada bay area. This deposit is divided into two levels. Level A is made of gravel sediments with parallel stratification and cemented by calcium carbonate. This level is composed of Ostrea stentina with 1 m in thickness and Level B is composed of a clast-supported gravel with low-angle cross stratification with marine bivalves and gastropods. Level A is dated to 43 Ka by 14C. These data suggest that this deposit is correlated with MIS 3 and it is associated with a deposit older than MIS 7 because MIS 3 is not represented in marine deposits on the continental shelf of Argentina. This interglacial event is characterized by lower temperatures than today. Several studies indicate that, during MIS 3, the sea level would have oscillated between ? 80 m and -20 m in height. The bottom level is dated to 28.7 and 38.5 Ka by 14C and it is correlated with MIS 5e. The benthonic marine fauna of level B is similar to that of other marine deposits of Anegada bay and San Blas area in the south of Buenos Aires Province. This deposit may indicate older Pleistocene marine deposits such as MIS 11. This was the warmest Interglacial event among recent events. MIS 11 is dated between 425 - 390 Ka when the averaged position of the sea level was at 1.5 m ± 3 in height. The geographical range of Ostrea stentina species is a predominant tropical distribution influenced by the Brazilian Current. Finally, the presence of Ostrea stentina in a marine deposit at Villalonga suggests that the superficial sea temperature (SST) was higher than MIS 5e SST. We conclude that the marine deposit of Ostrea stentina may indicate the existence of marine deposits correlated with MIS 11 in the south of Buenos Aires province.