Stratigraphy of the Birdrong: an integrated approach

Abstract

A detailed study of the Early Cretaceous Birdrong Sequence (S. areolata - P. burgeri) has been undertaken in the East Spar and Woollybutt fields, which lie in the northern end of the Barrow Delta complex in the Barrow Sub-basin, Northern Carnarvon Basin. This project integrates palynological, sedimentological and seismic stratigraphic interpretations to progress our understanding of the way in which the Barrow Delta evolved. The results will help develop remaining hydrocarbon prospectivity in the northern Barrow area. Palynological analysis within the Helby, Morgan and Partridge (2004) zonation scheme for the North West Shelf has enabled the identification of several significant biostratigraphic events, which have allowed further subdivision of the existing broad palynological zones. These palynological events represent influxes of specific dinoflagellate cyst taxa that may be tied to key stratal surfaces. These surfaces include transgressive ravinement surfaces, sequence boundaries and flooding surfaces. The palynological and sedimentological data, when combined, indicate a strong facies relationship between specific taxa and interpreted depositional environment. Such taxa include Gagiella, freshwater and brackish algae, and fully marine dinoflagellate cysts including Kaiwaradinium scrutillinum, Systematophora areolata, Phoberocysta neocomica and Cribroperidinium muderongense. The integration of sedimentology and palynology provides a powerful tool in interpreting depositional systems in shallow marine palaeoenvironments. Initial results indicate this may be used as a predictive tool for reservoir correlation and facies modelling. Key stratal surfaces identified through palynological and sedimentological study will be tested against 3D seismic to understand fully the stratigraphy of the study interval.