Evidence for oxygenic photosynthesis half a billion years before the Great Oxidation Event

Noah J. Planavsky, Dan Asael, Axel Hofmann, Christopher T. Reinhard, Stefan V. Lalonde, Andrew Knudsen, Xiangli Wang, Frantz Ossa Ossa, Ernesto Pecoits, Albertus J.B. Smith, Nicolas J. Beukes, Andrey Bekker, Thomas M. Johnson, Kurt O. Konhauser, Timothy W. Lyons, Olivier J. Rouxel

Research output: Contribution to journalArticlepeer-review

Abstract

The early Earth was characterized by the absence of oxygen in the ocean-atmosphere system, in contrast to the well-oxygenated conditions that prevail today. Atmospheric concentrations first rose to appreciable levels during the Great Oxidation Event, roughly 2.5-2.3 Gyr ago. The evolution of oxygenic photosynthesis is generally accepted to have been the ultimate cause of this rise, but it has proved difficult to constrain the timing of this evolutionary innovation. The oxidation of manganese in the water column requires substantial free oxygen concentrations, and thus any indication that Mn oxides were present in ancient environments would imply that oxygenic photosynthesis was ongoing. Mn oxides are not commonly preserved in ancient rocks, but there is a large fractionation of molybdenum isotopes associated with the sorption of Mo onto the Mn oxides that would be retained. Here we report Mo isotopes from rocks of the Sinqeni Formation, Pongola Supergroup, South Africa. These rocks formed no less than 2.95 Gyr ago in a nearshore setting. The Mo isotopic signature is consistent with interaction with Mn oxides. We therefore infer that oxygen produced through oxygenic photosynthesis began to accumulate in shallow marine settings at least half a billion years before the accumulation of significant levels of atmospheric oxygen.

Original languageEnglish (US)
Pages (from-to)283-286
Number of pages4
JournalNature Geoscience
Volume7
Issue number4
DOIs
StatePublished - Apr 2014

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

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