Geology and palaeontology of the Marine Maastrichtian of the James Ross Basin, Antarctica: New multi proxy approach

BONA, P.; O´GORMAN, J.P.; RAFFI, M.E.; TINEO, D.E.; REGUERO, M.

Hobart

Congreso; SCAR OPEN SCIENCE CONFERENCE 2020; 2020

SCAR

During the last summer 2020 field trip carried out under the Argentine Antarctic Program (IAA-DNA), new geological and palaeontological data of the Maastrichtian López de Bertodano Formation (Upper Cretaceous), James Ross Basin was recovered. This transgressive/regressive sequence is well exposed in the Sandwich Bluff Member of Vega Island and in the southern part of Seymour (Marambio) Island. The aim of this study is to compare both areas, in order to evaluate in detail their potential palaeoecological differences. We elaborate detail sedimentological logs and exhume new fossil material of vertebrates, invertebrates and plants. Fossil vertebrates belong to neognathae birds, chondrichthyes and osteichthyes fishes and marine reptiles. In comparison with Seymour Island fossil vertebrates at Sandwich Bluff Member were found isolated or incomplete, and the fossil association of marine reptiles is characterized by less abundance of mosasaurs vs plesiosaurs. The invertebrate fauna is less abundant and diverse. Few isolated bivalves were recovered and the presence of abundant and well preserved leaves and logs suggest a stressful environment. Vega fossil assemblages indicate marginal near-shore environments under tidalinfluence characterized by an impoverished of invertebrate. In terms of diversity and taphonomy, the fossil record of marine reptiles in this area could be indicating that they would not have actively inhabited these environments, and that the incomplete remains found correspond to fragments of skeletons dragged towards the coast. The sedimentological data shows that upper beds of the Sandwich Bluff Member consist of siltstone to fine-grained sandstone deposits.