Taphonomic analysis of Littoridina Souleyet, 1852 (Gastropoda : Hydrobiidae) in Holocene sections of the Quequen Grande river (Buenos Aires province): Paleobiological and paleoenvironmental significance.

Taphonomic aspects of dense deposits of Littoridina australis (d'Orbigny) a nd Littoridina parchappii (d'Orbigny), from a Holocene outcrop located at t he Quequen Grande river, were used as paleobiological and paleoenvironmenta l indicators to reconstruct the evolution of the estuarine environment betw een circa 7,000 and 5,000 C-14 yr BP. Levels with dominance of Littoridina parchappii correspond to autochtonous fossil assemblages deposited under lo w energy estuarine conditions. On the other hand, most specimens of Littori dina australis were redeposited and represent transported assemblages. The differences shown by both species are probably related to the energy condit ions of the environments where they lived. As Littoridina parchappii is par t of a fossil population, it can be considered a good paleobiological and p aleoenvironmental indicator whereas Littoridina australis, which basically belongs to a taphocoenosis, can be a useful tool to evaluate both paleoenvi ronmental and depositional conditions such as the relative energy and direc tion of the dominant currents.