| Autor: |
Johnson AC; School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA.; Department of Geophysical Sciences, University of Chicago, Chicago, IL, USA., Ostrander CM; School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA.; Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA., Romaniello SJ; Department of Earth and Planetary Sciences, University of Tennessee-Knoxville, Knoxville, TN, USA., Reinhard CT; School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA., Greaney AT; Oak Ridge National Laboratory, Knoxville, TN, USA., Lyons TW; Department of Earth and Planetary Sciences, University of California, Riverside, Riverside, CA, USA., Anbar AD; School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA.; School of Molecular Sciences, Arizona State University, Tempe, AZ, USA. |
| Abstrakt: |
Evidence continues to emerge for the production and low-level accumulation of molecular oxygen (O 2 ) at Earth’s surface before the Great Oxidation Event. Quantifying this early O 2 has proven difficult. Here, we use the distribution and isotopic composition of molybdenum in the ancient sedimentary record to quantify Archean Mo cycling, which allows us to calculate lower limits for atmospheric O 2 partial pressures ( P O 2 ) and O 2 production fluxes during the Archean. We consider two end-member scenarios. First, if O 2 was evenly distributed throughout the atmosphere, then P O 2 > 10 –6.9 present atmospheric level was required for large periods of time during the Archean eon. Alternatively, if O 2 accumulation was instead spatially restricted (e.g., occurring only near the sites of O 2 production), then O 2 production fluxes >0.01 Tmol O 2 /year were required. Archean O 2 levels were vanishingly low according to our calculations but substantially above those predicted for an abiotic Earth system. |
