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Sulfur mass-independent fractionation is proposed as an atmospheric oxygen proxy

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Farquhar, Bao and Thiemens reported that sulfur isotopes in sedimentary rocks older than roughly 2.4 billion years carry a mass-independent fractionation signature, and that this signature disappears in younger rocks. Because the signature is produced by ultraviolet photochemistry in an atmosphere with no ozone shield, and because it is homogenised away once an oxidised sulfate reservoir exists, its disappearance dates the point at which free oxygen became a persistent atmospheric constituent. The result converted the Great Oxidation Event from a qualitative inference drawn from red beds, banded iron formations and detrital uraninite grains into a stratigraphic horizon that could be located and dated in section — which is why the event now has a bracketed date at all.

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Assembled from 21 blocks · 1 evidence · 19 related

  1. Story
  2. Farquhar, Bao and Thiemens reported that sulfur isotopes in sedimentary rocks older than roughly 2.4 billion years carry a mass-independent fractionation signature, and that this signature disappears in younger rocks. Because the signature is produced by ultraviolet photochemistry in an atmosphere with no ozone shield, and because it is homogenised away once an oxidised sulfate reservoir exists, its disappearance dates the point at which free oxygen became a persistent atmospheric constituent. The result converted the Great Oxidation Event from a qualitative inference drawn from red beds, banded iron formations and detrital uraninite grains into a stratigraphic horizon that could be located and dated in section — which is why the event now has a bracketed date at all.
  3. Knowledge
  4. Radiometric dating
  5. Mass-independent fractionation of sulfur isotopes
  6. Sulfur mass-independent fractionation is proposed as an atmospheric oxygen proxy
  7. Connections
  8. Mass-independent fractionation of sulfur isotopes
  9. Radiometric dating
  10. The Great Oxidation Event
  11. The Great Oxidation Event
  12. Sulfur mass-independent fractionation is proposed as an atmospheric oxygen proxy
  13. Mass extinction
  14. Zircon as a geochronometer
  15. Molecular clock dating
  16. The end-Permian mass extinction
  17. Sulfur mass-independent fractionation is proposed as an atmospheric oxygen proxy
  18. The K–Pg boundary is dated to 66.043 ± 0.043 Ma
  19. The end-Permian extinction is resolved to about sixty thousand years
  20. Evidence
  21. Supports the use of mass-independent sulfur isotope fractionation as a proxy for an anoxic, ozone-free atmosphere and its disappearance as a marker of the Great Oxidation Event. V55 verification basis: this session had no network access to any source — WebFetch was egress-blocked and the WebSearch budget was exhausted — so the cited work was not retrieved and its pagination was not re-checked. Volume and page range are quoted from standing knowledge and were not re-checked.
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