Uranium and molybdenum isotope evidence for an episode of widespread ocean oxygenation during the late Ediacaran Period

To improve estimates of the extent of ocean oxygenation during the late Ediacaran Period, we measured the U and Mo isotope compositions of euxinic (anoxic and sulfidic) organic-rich mudrocks (ORM) of Member IV, upper Doushantuo Formation, South China. The average δ238U of most samples is 0.24 ± 0.16‰ (2SD; relative to standard CRM145), which is slightly higher than the average δ238U of 0.02 ± 0.12‰ for restricted Black Sea (deep-water Unit I)...