Uranium isotope evidence for limited euxinia in mid-Proterozoic oceans

Reconstructing Earth's oxygenation history is key to deciphering environmental controls on early biospheric evolution. During the mid-Proterozoic Eon, low (but potentially variable) atmospheric pO2 led to highly heterogeneous marine redox conditions, with most studies indicating a relatively shallow depth of oxygen penetration. The relative proportion of oxic, anoxic and iron-rich (ferruginous), and anoxic and sulfide-rich (euxinic) conditions...