CONICET | Buscador de Institutos y Recursos Humanos

Bioerosion traces are abundant on marine molluscs in Late Quaternary deposits along the South American Atlantic coast. The study of biogenic traces in fossil mollusc shells of the South Atlantic coasts has been significant in recent years, providing clues for the study of paleoenvironmental and paleoecological conditions as well as the evolution of hard substrate communities. The aim of work 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 datings are at the limit of the method, and hence, are considered as minimum ages. They are associated with fauna that indicate warm conditions; thus the deposits were correlated with the Interglacial (MIS 5e). Bioerosion marks were recorded on 38.9 % of 298 valves of 18 species (9 gastropods and 9 bivalves). Five ichnogenera were reported: 4 Domichnia: Maeandropolydora (33.3%), Pinaceocladichnus (25%), Entobia (16.6%), Iramena (8.3%), and one Praedichnia: Oichnus (8.33%). In addition, a new biogenic hollow trace was found, characterized by a multiradiate star-shaped outline. This new trace is similar to Stellatichnus radiates but about 2000 - 3000 µm length. In addition, seven bioeroded species were identified: Nucula nucleus, Brachidontes rodriguezii, Ostreola equestris, Ostreola puelchana (bivalvia), and Tegula patagonica and Siphonaria lessoni (gastropods). The benthonic marine community is composed of polychaete annelids, cheilostome bryzoans, clionaid sponges and predator gastropods, associated with warm marine molluscs. The area was described as a sublittoral enviroment, with low-energy and sandy bottoms in the Late Pleistocene.

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