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Proc Natl Acad Sci U S A. 2019 Aug 27;116(35):17207-17212. doi: 10.1073/pnas.1900325116. Epub 2019 Aug 12.

A productivity collapse to end Earth's Great Oxidation.

Author information

1
Department of Geological Sciences, Stanford University, Stanford, CA 94305; mswh@stanford.edu peter.crockford@weizmann.ac.il.
2
Department of Earth and Planetary Sciences, Weizmann Institute of Science, 761000 Rehovot, Israel; mswh@stanford.edu peter.crockford@weizmann.ac.il.
3
Department of Geoscience, Princeton University, Princeton, NJ 08544.
4
School of Earth Sciences and Engineering, Nanjing University, 210023 Nanjing, China.
5
Department of Geological Sciences, University of Colorado Boulder, Boulder, CO 80309.
6
Non-traditional Isotope Research on Various Advanced Novel Applications (NIRVANA) Labs, Woods Hole Oceanographic Institution, Woods Hole, MA 02543.
7
Department of Marine Chemistry & Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543.

Abstract

It has been hypothesized that the overall size of-or efficiency of carbon export from-the biosphere decreased at the end of the Great Oxidation Event (GOE) (ca. 2,400 to 2,050 Ma). However, the timing, tempo, and trigger for this decrease remain poorly constrained. Here we test this hypothesis by studying the isotope geochemistry of sulfate minerals from the Belcher Group, in subarctic Canada. Using insights from sulfur and barium isotope measurements, combined with radiometric ages from bracketing strata, we infer that the sulfate minerals studied here record ambient sulfate in the immediate aftermath of the GOE (ca. 2,018 Ma). These sulfate minerals captured negative triple-oxygen isotope anomalies as low as ∼ -0.8‰. Such negative values occurring shortly after the GOE require a rapid reduction in primary productivity of >80%, although even larger reductions are plausible. Given that these data imply a collapse in primary productivity rather than export efficiency, the trigger for this shift in the Earth system must reflect a change in the availability of nutrients, such as phosphorus. Cumulatively, these data highlight that Earth's GOE is a tale of feast and famine: A geologically unprecedented reduction in the size of the biosphere occurred across the end-GOE transition.

KEYWORDS:

Great Oxidation Event; Proterozoic; nutrient limitation; primary productivity; triple-oxygen isotopes

PMID:
31405980
PMCID:
PMC6717284
[Available on 2020-02-12]
DOI:
10.1073/pnas.1900325116

Conflict of interest statement

The authors declare no conflict of interest.

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