Quantification of atmospheric oxygen levels during the Paleoproterozoic using paleosol compositions and iron oxidation kinetics

Estimates of atmospheric CO2 in the Neoarchean–Paleoproterozoic from paleosols

“…The errors were calculated from the errors in the retention fractions. f Only the upper limit is shown because of almost complete retention of Fe in the Flin Flon paleosol (Murakami et al, 2011a). g Calcium loss associated with silicates is obtained by subtracting CO 2 loss (mol m À3 ) from the total calcium loss (mol m À3 ).…”

“…The Neoarchean-Paleoproterozoic paleosols used were those passing through a screening test of the absence and presence of significant physical and chemical disturbances (Murakami et al, 2011a): Mt. Roe (1), Mt.…”

“…Roe (1), Mt. Roe (2), Bird, Cooper Lake and Pronto/NAN paleosols) and less so (<$10 À5 mol L À1 ) at <$2.2 Ga (i.e., for the Gaborone, Drakenstein and Flin Flon paleosols), resulting from slower and faster rates of Fe 2+ oxidation, respectively, which is greatly affected by P O 2 levels (Murakami et al, 2011a;Yokota et al, 2013).…”

“…Using this method, Sheldon's group estimated 7-70 PAL of P CO 2 at 2.2 Ga (Sheldon, 2006) and 10-50 PAL at 2.69 Ga (Driese et al, 2011). Importantly, P CO 2 levels have also been used either directly or indirectly as a parameter for the estimation of P O 2 levels from paleosols (Holland, 1984;Murakami et al, 2011a;Yokota et al, 2013). Therefore, the estimated P CO 2 levels need to be sufficiently precise to understand the atmospheric oxygen evolution in the Neoarchean-Paleoproterozoic.…”

Hypothesized link between Neoproterozoic greening of the land surface and the establishment of an oxygen-rich atmosphere

“…A diminution of this volcanic-metamorphic sink, to below the net source of oxygen associated with the sequestration of organic matter produced by oxygenic photosynthesis, occurred at or near the ArcheanProterozoic transition as the continents stabilized and became largely subaerially exposed. This Great Oxidation Event may have been somewhat protracted (20) as oxidative weathering of a large, accumulated reservoir of reduced crustal materials put a damper on oxygen accumulation (21). Eventually this damper was overwhelmed, and atmospheric oxygen levels may have significantly overshot (22)(23)(24) their intermediate Proterozoic steady state of ca.…”