Euxinia linked to the Cambrian Drumian carbon isotope excursion (DICE) in Australia: Geochemical and chemostratigraphic evidence

Abstract

The Cambrian Drumian carbon isotope excursion (DICE) event is a negative carbon isotope (δ13C) excursion. It is associated with the first appearance datum (FAD) of the agnostoid arthropod Ptychagnostus atavus, whose first appearance in the Global boundary Stratotype Section and Point (GSSP) defines the base of the Cambrian Series 3 Drumian Stage. Although this isotopic event has been clearly identified in the Great Basin, USA, it has not been consistently reported in other areas of the world. Here, we report a study integrating isotopic and geochemical data from middle Cambrian (Series 3) sections from the northeastern Georgina Basin, Australia, to investigate the occurrence of the DICE event in Australia and the paleoenvironmental conditions associated with this event. The similarity between the isotopic excursions observed in the Georgina Basin (−2‰ to −3.2‰ δ13C excursion) and that observed in the Great Basin (−2‰ to −3.6‰ δ13C excursion) highlighted the presence of the DICE in Australia and emphasized the potential use of this event for refining global isotopic correlations. The multi-proxy correlation used in this study also showed a pulse of euxinia in association with the DICE, suggesting strongly euxinic conditions near the base of the Drumian Stage.