ICNOLOGIA DE LA FORMACION WHISKY BAY (CRETACICO, ISLA JAMES ROSS, ANTARTIDA): IMPLICANCIAS PALEOECOLOGICAS Y PALEOAMBIENTALES

Abstract

Trace fossil assemblages from inner submarine fan deposits of the Whisky Bay Formation (Gustav Group), Cretaceous of James Ross Island. Antarctica are described. Systematic ichnology, ethology and paleoecological/paleoenvironmental implications are taken into account. Trace fossils are grouped in two ichnocoenoses: (A) dominated by dwelling or dwelling-feeding structures of suspension-feeders in a sandy substrate (Arenicolites, Diplocraterion, Palaeophycus, Skolithos and Thalassinoides) and (B) dominated by feeding structures of deposit-feeders in a muddy substrate (Chondrites, Cylindrichnus, and Zoophycos). Ichnocoenosis A includes "shallow water traces" and was developed in minor channels, terraces and sandy proximal plains where high-energy currents kept organic particles in suspension. Ichnocoenosis B was developed in interchannel areas far away from major channels where energy was low and organic-rich sediment was present. Ichnocoenosis B is unusual when it is compared with similar ones from classical turbidites. Agrichnia is absent and Fodinichnia es very abundant. It is suggested that high frequency of sediment gravity flows in an inner submarine fan close to the source area and perhaps at fairly shallow depths than the usual for this type of settings prevents Agrichnia development.