Transient and stepwise ocean oxygenation during the late Ediacaran Shuram Excursion: Insights from carbonate δ238U of northwestern Mexico

The Ediacaran Shuram Excursion (SE) was a key episode in the history of atmospheric and oceanic oxygenation that has also been linked to contemporaneous bioevolutionary events. However, key aspects of the redox state of Ediacaran oceans during the SE remain in doubt. Here, the uranium isotope compositions (δ238U) of marine carbonates from Sonora, northwestern Mexico were measured to investigate ocean oxygenation during the SE. We found that the...