Low mid-proterozoic atmospheric oxygen levels and the delayed rise of animals

Noah J. Planavsky, Christopher T. Reinhard, Xiangli Wang, Danielle Thomson, Peter McGoldrick, Robert H. Rainbird, Thomas Johnson, Woodward W. Fischer, Timothy W. Lyons

Research output: Contribution to journalReview articlepeer-review


The oxygenation of Earth's surface fundamentally altered global biogeochemical cycles and ultimately paved the way for the rise of metazoans at the end of the Proterozoic. However, current estimates for atmospheric oxygen (O2) levels during the billion years leading up to this time vary widely. On the basis of chromium (Cr) isotope data from a suite of Proterozoic sediments from China, Australia, and North America, interpreted in the context of data from similar depositional environments from Phanerozoic time, we find evidence for inhibited oxidation of Cr at Earth's surface in the mid-Proterozoic (1.8 to 0.8 billion years ago). These data suggest that atmospheric O2 levels were at most 0.1% of present atmospheric levels. Direct evidence for such low O2 concentrations in the Proterozoic helps explain the late emergence and diversification of metazoans.

Original languageEnglish (US)
Pages (from-to)635-638
Number of pages4
Issue number6209
StatePublished - Oct 31 2014

ASJC Scopus subject areas

  • General


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