Editor's Summary

27 March 2008

Oxygen steps in the ocean

The oxygenation of the Earth's atmosphere is thought to have occurred in two steps near the beginning and the end of the Proterozoic eon, around 2,500 to 550 million years ago. The oxidation state of the ocean between these two steps and the timing of deep ocean oxygenation, however, remain poorly known. Scott et al. now use molybdenum and total organic carbon data from black shales to track the redox state of the ocean at this time. Molybdenum is an essential participant in nutrient cycling, and its availability is highly sensitive to Earth's redox state. The results provide a new narrative for the historical texture of Earth's oxygenation, and will be of relevance for the study of the events that presaged the appearance of animals on Earth.

LetterTracing the stepwise oxygenation of the Proterozoic ocean

C. Scott, T. W. Lyons, A. Bekker, Y. Shen, S. W. Poulton, X. Chu & A. D. Anbar