Sulphur isotope evidence for an oxic Archaean atmosphere

Hiroshi Ohmoto, Yumiko Watanabe, Hiroaki Ikemi, Simon R. Poulson, Bruce E. Taylor

Research output: Contribution to journalArticlepeer-review

193 Citations (Scopus)


The presence of mass-independently fractionated sulphur isotopes (MIF-S) in many sedimentary rocks older than ∼2.4 billion years (Gyr), and the absence of MIF-S in younger rocks, has been considered the best evidence for a dramatic change from an anoxic to oxic atmosphere around 2.4 Gyr ago. This is because the only mechanism known to produce MIF-S has been ultraviolet photolysis of volcanic sulphur dioxide gas in an oxygen-poor atmosphere. Here we report the absence of MIF-S throughout ∼100-m sections of 2.76-Gyr-old lake sediments and 2.92-Gyr-old marine shales in the Pilbara Craton, Western Australia. We propose three possible interpretations of the MIF-S geologic record: (1) the level of atmospheric oxygen fluctuated greatly during the Archaean era; (2) the atmosphere has remained oxic since ∼3.8 Gyr ago, and MIF-S in sedimentary rocks represents times and regions of violent volcanic eruptions that ejected large volumes of sulphur dioxide into the stratosphere; or (3) MIF-S in rocks was mostly created by non-photochemical reactions during sediment diagenesis, and thus is not linked to atmospheric chemistry.

Original languageEnglish
Pages (from-to)908-911
Number of pages4
Issue number7105
Publication statusPublished - Aug 24 2006

All Science Journal Classification (ASJC) codes

  • General


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