Corrigendum to “A redox-stratified ocean 3.2 billion years ago” [Earth Planet. Sci. Lett. (2015) 430 (43–53)] (S0012821X15005270)(10.1016/j.epsl.2015.08.007)

The authors have discovered a calculation error in the concentration data for U, Th and Pb. This error does not affect any measured isotopic compositions: ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, ²³⁸U/²⁰⁴Pb, ²³²Th/²⁰⁴Pb, and ²³⁵U/²⁰⁴Pb; these all remain the same. None of the Fe isotope data are affected. Hence, none of the conclusions for open or closed-system U–Th–Pb behavior are affected, nor the conclusions of a redox gradient between shallow- and deep-water U contents. The magnitude of the shallow- and deep-water U content contrast remains the same, where U contents in shallow seawater are estimated to have been about three times that of deep-water samples. The corrected U, Th, and Pb contents, noted in red in the table below, are all lower by ∼30% from the original publication. For Figs. 2, 3, and 4 in the original publication, which plot Fe/Th ratios, the relative position of plotted data does not change, but the corrected concentrations affect the scale at which these data are plotted. To illustrate this, for Figs. 2, 3, and 4 both the original Fe/Th scale and the corrected Fe/Th scale are shown for comparison. As noted above, because there is no change in the relative position of the data on these plots, there is no change in the conclusion of a redox gradient between shallow- and deep-water samples. For Figs. 3 and 4, which compare Fe/Th ratios to Fe isotope compositions, these relations remain the same but simply change the assumed Fe/Th ratio at 100% oxidation. Fig. 7 requires revision in terms of the estimated seawater U contents for the shallow- and deep-water samples, which is based on Fe–U concentration relations. In the original publication, these were estimated at 0.14 ppb and 0.04 ppb, respectively. The revised values, noted in the figure below, are 0.10 ppb and 0.03 ppb (rounded to 2 decimal places), respectively. As noted above, the contrast in shallow- and deep-water U contents remains identical to the original publication. The estimated U contents for the Marble Bar Chert is unchanged, at 0.02 ppb (Li et al., 2013). Note also, that these modified U contents change in the labels in Fig. 8, but that figure is not duplicated here. Although we regret the error, we stress that this does not at all affect the reported isotopic compositions, nor the conclusions that this is the oldest known (at the time of publication) marine redox gradient, supported by both the stable Fe isotope variations, as well as the contrast in U contents for shallow- and deep-water samples.