Upper Triassic calcareous nannoplankton biostratigraphy, Wombat Plateau, northwest Australia

Investigation has been carried out on Carnian-Rhaetian nannofossils from Sites 759, 760, 761 and 764. The recovery of continuous sequences containing well-reserved nannofossils has enabled the refinement of previous taxonomy and biostratigraphy for this interval. Fossil assemblages are of two major types: previously described calcareous taxa were recoverd at Sites 761 and 764; sideritic forms, which may represent diagenetic replacement of calcareous nannofossils, were observed in material from Sites 759 and 760. Stable isotopic analyses of Wombat Plateau nannofossil assemblages indicate that they thrived in open ocean conditions. Biostratigraphy allows sequence chronostratigraphic interpretation of Site 761 and supports the eustatic-chronostratigraphic framework of Haq et al. (1987). -from Authors