Integrated Shelly Fossil Biostratigraphy and Carbon and Oxygen Chemostratigraphy: Applying a Multi-Proxy Toolkit to Correlating the Lower Cambrian of South Australia

Abstract

Despite decades of concerted efforts, the Cambrian Period remains one of the most underdeveloped parts of the International Geological Timescale, with the boundaries of a number of series and stages still awaiting definition and subsequent ratification. A major impediment to the development of the Cambrian timescale and global correlation, particularly in Australia, is the paucity of comprehensive biostratigraphic, lithostratigraphic and chemostratigraphic data. Hence, there has been increased drive to utilise the stratigraphic ranges of small shelly fossils (SSF) and apply isotopic chemostratigraphic methods to regional studies in an effort to resolve and calibrate the timescale. In South Australia, the lower Cambrian succession in the Arrowie Basin is well preserved, well exposed and contains rich fossil assemblages. These qualities have been exploited in a new biostratigraphic scheme utilising assemblage zones of SSF and associated mineralised taxa. Shelly fossils have been extracted from ten measured stratigraphic sections and display ranges that are robust and repeatable across the Arrowie Basin. This new scheme correlates well with faunas from the coeval Stansbury Basin; however, endemic and diachronistic taxa hinder effective global application. Chemostratigraphic data, when utilised in concert with biostratigraphy and lithostratigraphy, can allow regional schemes to be put in a global context. Consequently, carbon and oxygen isotope curves have been developed for the Arrowie Basin sections in an effort to provide a more suitable proxy for correlation. This is the first time oxygen and carbon isotopic chemostratigraphic data have been integrated with a robust biostratigraphic scheme for the early Cambrian of Australia, and demonstrates the value of applying a multi-proxy dataset to the problem of stratigraphic correlation.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015