Incomplete oxidative sulfide weathering and low atmospheric oxygen levels during the Great Oxidation Event

Multiple lines of evidence support permanent oxygenation of the Earth’s atmosphere during the early Paleoproterozoic (~2.5–2.1 billion years ago). Here, we report geochemical data, along with sulfide textures, for >2.31-bilion-year-old sedimentary rocks from the upper Espanola and Serpent formations that underlie the third glacial diamictite of the Huronian Supergroup, Canada. Redox-sensitive element contents and the isotopic compositions of molybdenum and sulfur are comparable to upper continental crust value. Subangular to rounded pyrite grains of detrital origin are observed in sandstones of the Serpent Formation. Our data indicate limited oxidative weathering of crustal sulfide prior to the third glaciation of the Huronian succession, consistent with low atmospheric oxygen levels (<5×10−4 of the present atmospheric level). We suggest that such low atmospheric oxygen levels persisted for long periods prior to the final glaciation of the Huronian succession.