Biostratigraphy and chemostratigraphy of the lower Cambrian Normanville Group, South Australia

Australia has lagged behind in constructing a workable lower Cambrian regional biostratigraphic scheme. However, recent work utilising both bio- and chemostratigraphic data has produced a robust chronostratigraphic scheme for the Arrowie Basin in South Australia. This multi-proxy approach provides independent datasets that facilitate refined chronostratigraphic correlation of Australian lower Cambrian rock packages with the global Cambrian timescale. The Kulparina rostrata Zone in the Arrowie Basin closely aligns with a significant negative δ13C (carbon-13/12 isotope ratio) excursion, the ‘SHICE’. A key prediction of this correlation was that older successions in the neighbouring Stansbury Basin should contain a significant positive δ13C isotope excursion, the ‘ZHUCE’. This study, using similar multi-proxy data for the eastern Stansbury Basin, tested the validity of this prediction. The topmost 83 m of the ‘WANG’ section was confidently correlated with the Kulparina rostrata Zone based on co-occurring, diagnostic fossil assemblages. The chemostratigraphic results closely match the global chemostratigraphic curve. The ‘SHICE’ negative excursion occurs within the upper Sellick Hill Formation. Significantly, a large positive δ13C excursion (max +5.70‰) was discovered in the lower Sellick Hill Formation; interpreted to represent the global ‘ZHUCE’ positive δ13C event which is identified from Australia for the first time, confirming previous chronostratigraphic predictions.