Persistent late Tonian shallow marine anoxia and euxinia

Abstract

The increase in the complexity of eukaryotic life during the Tonian Period (ca. 1000 to 720 Ma) is commonly associated with the oxygenation of the Earth's ocean–atmosphere system, yet the timing and duration of these redox changes remain uncertain. In particular, it is unclear how shallow marine environments, which were likely crucial habitats for early eukaryotic organisms, responded to Neoproterozoic oxygenation. This study uses trace and rare earth element geochemistry to determine shallow marine redox conditions during the deposition of the late Tonian (ca. 760 Ma) Devede Formation, northern Namibia. In this unit, although carbonate phases (microbialite, former aragonite and high Mg calc..