CR: Examining the evolution of biospheric oxygenation in Late Archean to Middle Proterozoic oceans through high-resolution trace metal chemostratigra

We propose to obtain high-resolution trace metal geochemical profiles from organic-rich mudrocks (ORM) to examine the evolution of biospheric oxygenation in Late Archean to Middle Proterozoic oceans. The value of high-resolution geochemical profiling was shown in prior collaborative work by the PIs on 2.6-2.5 Ga ORM from Western Australia and South Africa. This work points uniquely to oxygenic photosynthesis and surface ocean oxygenation at least 50-100 M.y. before the first rise of atmospheric O2 (2.45-2.32 Ga Great Oxidation Event; GOE). Our chemostratigraphic approach revealed an otherwise unrecognized history of biospheric oxygenation that is more complex than previously realized. Despite this success, high-resolution geochemical profiles for other Precambrian stratigraphic sections are not yet available.x