Sedimentology and integrated chronostratigraphy of the lower Heatherdale Shale (Cambrian, stages 2-3), Stansbury Basin, South Australia

Abstract

Major progress has recently been made regarding the biostratigraphy, lithostratigraphy and isotope chemostratigraphy of the lower Cambrian successions in South Australia, in particular of the Arrowie Basin, which has facilitated robust global stratigraphic correlations. However, lack of faunal and sedimentological data from the lower Cambrian Normanville Group in the eastern Stansbury Basin, South Australia - particularly the transition from the Fork Tree Limestone to the Heatherdale Shale - has prevented resolution of the age range, lithofacies, depositional environments and regional correlation of this succession. Here we present detailed sedimentologic, biostratigraphic and chemostratigraphic data through this transition in the eastern Stansbury Basin. Three lithofacies are identified that indicate a deepening depositional environment ranging from inner-mid-shelf (Lithofacies A and B) to outer shelf (Lithofacies C). New δ13C chemostratigraphic data capture global positive excursion III within the lower Heatherdale Shale. Recovered bradoriid Sinskolutella cuspidata supports an upper Stage 2 (Micrina etheridgei Zone). The combined geochemistry and palaeontology data reveal that the lower Heatherdale Shale is older than previously appreciated. This integrated study improves regional chronostratigraphic resolution and interbasinal correlation, and better constrains the depositional setting of this important lower Cambrian package from the eastern Stansbury Basin, South Australia.