The Great Oxidation Event and early eukaryote evolution

Atmospheric oxygen levels first permanently increased in the Great Oxidation Event around 2.4 billion years ago. This pre-dates the earliest fossil evidence of eukaryotes (1.7 Ga) by several hundred million years. We set out to generate redox proxy records that could determine whether this interim period was marked by conditions hospitable to eukaryotes. Using selenium and nitrogen isotope records in Paleoproterozoic shales, we were able to show that the surface ocean in fact was likely well-oxygenated enough to support early eukaryotes long before their appearance in the fossil record. We're now following up on this work in a few ways, including by looking at higher-resolution chemostratigraphy in well-preserved Paleoproterozoic basins, such as the Francevillian Series of Gabon.