Bioerosion on valves of mollusks in Los Pocitos (Late Pleistocene) southern Buenos Aires Province, Argentina.

CHARÓ, M.P., ACEÑOLAZA, G.F., Y CAVALLOTTO, J.

Valencia

Congreso; 1rst Palaeontological Virtual Congress; 2018

Universidad de Valencia

Bioerosion traces are abundant on marine mollusks in Late Quaternary deposits along the South American Atlantic coast. The study of biogenic traces in fossil mollusk shells of the South Atlantic coasts has been significant in recent years, providing clues for the study of palaeoenvironmental and palaeoecological conditions as well as for the evolution of hard substrate communities. The aimof this contribution is to report the first Late Pleistocene bioerosion traces on marine bivalves and gastropods of Los Pocitos (40º26´S - 62º25´W), in the south of Buenos Aires Province. The marine deposit is dated in 43, 38.8 and 31 Ky(14C) with heights of 8.6 m. These dates are at the limit of the method, and hence, they are considered as minimum ages. The marine deposits are associated with fauna that indicate warm conditions; thus the deposits were correlated with the Interglacial (MIS 5e). Bioerosion traces were recorded in 38.9 % of the 298 valves of attributed to 18 species (9 gastropods and 9 bivalves). Five ichnogenera were reported: Four Domichnia: Maeandropolydora (33.3%), Pinaceocladichnus (25%), Entobia (16.6%), Iramena (8.3%), and one Praedichnia: Oichnus (8.33%). In addition, a new biogenic hole trace was found in this area, characterized by a multiradiate star-shaped outline. This trace is Stellatichnus radiates but about 2000 - 3000 μm length.The benthonic marine community is composed of polychaete annelids, cheilostome bryozoans, clionaid sponges and predator gastropods, associated with warm marine mollusks. The area was described as a sublittoral environment, with low-energy and sandy bottoms in the Late Pleistocene.