Trace fossils on shelly substrate. An example from the Miocene of Patagonia, Argentina

Abstract

Bioerosion is a common process in lithified substrates. Nevertheless, organic shelly substrates can be used by dwelling organisms as temporary hard substrates. This study introduces an example from the Miocene of Patagonia (Río Negro Formation), cropping out at sea cliffs. The Río Negro Formation includes three members, the middle member being a shallow marine level that represents a complete transgressive - regressive cycle. The upper portion of the trangressive interval commonly includes pavements of oysters (Ostrea patagonica), which show many bioerosive structures. The traces have been assigned to the ichnogenera Gastrochaenolites and Entobia. Maeandropolydora isp. appears in a smaller proportion. The assemblage belongs to the Entobia Ichnofacies.