Bioerosion on marine Quaternary gastropods from the southern Golfo San Jorge, Patagonia, Argentina: What do they tell US?

Abstract

We present the ichnological characterization on marine gastropod shells from Late Pleistocene, mid-Holocene and modern beaches at 5 sampling sectors along the southern Golfo San Jorge, a key area at central Patagonia in terms of geological, physical and biological features of the southern Southwestern Atlantic margin. Based on bioerosion recovered in 579 gastropod shells (22% showing bioerosion and 78% free of traces), a total of 12 ichnogenera were recorded: Caedichnus, Caulostrepsis, Entobia, Finichnus, Iramena, Maeandropolydora, Oichnus, Pennatichnus, Pinaceocladichnus, Podichnus, Renichnus and Stellichnus. Of these, Iramena (57%), Oichnus (12%) and Maeandropolydora (9%) are the most abundant representing near 80% of the traces recorded, while Stellichnus is the first record for the marine Quaternary of Argentina. A comparison of bioerosional patterns along the area through time (Late Pleistocene, mid-Holocene and modern) allows reinforcing our previous ichnological evidence and hypotheses for Patagonia and other areas of Argentina. Overall, they tell us about changes to the present, pointing to a Last Interglacial colder water and higher productivity within a different circulation scenario compared to the mid-Holocene amelioration and present day conditions.