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Science 18 February 2005:
Vol. 307. no. 5712, pp. 1088 - 1091
DOI: 10.1126/science.1105692
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Reports

Iron Isotope Constraints on the Archean and Paleoproterozoic Ocean Redox State

Olivier J. Rouxel,1* Andrey Bekker,2 Katrina J. Edwards1

The response of the ocean redox state to the rise of atmospheric oxygen about 2.3 billion years ago (Ga) is a matter of controversy. Here we provide iron isotope evidence that the change in the ocean iron cycle occurred at the same time as the change in the atmospheric redox state. Variable and negative iron isotope values in pyrites older than about 2.3 Ga suggest that an iron-rich global ocean was strongly affected by the deposition of iron oxides. Between 2.3 and 1.8 Ga, positive iron isotope values of pyrite likely reflect an increase in the precipitation of iron sulfides relative to iron oxides in a redox stratified ocean.

1 Marine Chemistry and Geochemistry Department, Geomicrobiology Group, Woods Hole Oceanographic Institution, Mail Stop 8, Woods Hole, MA 02543, USA.
2 Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015, USA.

* To whom correspondence should be addressed. E-mail: orouxel{at}whoi.edu

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Comment on "Iron isotope constraints on the Archean and Paleoproterozoic ocean redox state"..
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Comment on "Iron Isotope Constraints on the Archean and Paleoproterozoic Ocean Redox State".
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Science. ISSN 0036-8075 (print), 1095-9203 (online)