Researchers report low oxygen levels in the early Earth atmosphere, suggesting large variations in oxygen concentration during the development of early life. Oxygen levels in the atmosphere have varied widely throughout Earth's history. Eric J. Bellefroid and colleagues investigated a succession of carbonate rocks in Northern Canada from around 1.87 billion years ago to assess oxygen levels during that time. The authors examined the ratio of cerium, which is highly sensitive to oxidation, to other rare earth elements and yttrium, and used the ratio as a proxy for atmospheric oxygen. The rocks analyzed represent different depths of formation in a marine environment, and the results showed a significant change in water oxidation chemistry below a depth of 50 meters. Using that measurement, the authors modeled atmospheric oxygen concentrations and report that oxygen levels had fallen to around 0.1% of present atmospheric levels around 1.87 billion years ago, a level low enough to influence the development of complex organisms. According to the authors, the use of carbonate rocks as a proxy for ancient atmospheric conditions can help reconstruct a detailed history of atmospheric oxygen on Earth.
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Article #18-06216: "Constraints on Paleoproterozoic atmospheric oxygen levels," by Eric J. Bellefroid, Ashleigh v.S. Hood, Paul, F. Hoffman, Matthew D. Thomas, Christopher T. Reinhard, and Noah J. Planavsky.
MEDIA CONTACT: Eric J. Bellefroid, Yale University, New Haven, CT; tel: 203-589-2304; e-mail: eric.bellefroid@yale.edu
Proceedings of the National Academy of Sciences