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dc.contributor.authorThomas, Katherine
dc.contributor.authorOno, Shuhei
dc.contributor.authorJohnson, Jena E.
dc.contributor.authorWebb, Samuel M.
dc.contributor.authorKirschvink, Joseph L.
dc.contributor.authorFischer, Woodward W.
dc.date.accessioned2014-03-10T20:00:10Z
dc.date.available2014-03-10T20:00:10Z
dc.date.issued2013-06
dc.date.submitted2013-03
dc.identifier.issn0027-8424
dc.identifier.issn1091-6490
dc.identifier.urihttp://hdl.handle.net/1721.1/85597
dc.description.abstractThe emergence of oxygen-producing (oxygenic) photosynthesis fundamentally transformed our planet; however, the processes that led to the evolution of biological water splitting have remained largely unknown. To illuminate this history, we examined the behavior of the ancient Mn cycle using newly obtained scientific drill cores through an early Paleoproterozoic succession (2.415 Ga) preserved in South Africa. These strata contain substantial Mn enrichments (up to ~17 wt %) well before those associated with the rise of oxygen such as the ~2.2 Ga Kalahari Mn deposit. Using microscale X-ray spectroscopic techniques coupled to optical and electron microscopy and carbon isotope ratios, we demonstrate that the Mn is hosted exclusively in carbonate mineral phases derived from reduction of Mn oxides during diagenesis of primary sediments. Additional observations of independent proxies for O[subscript 2]—multiple S isotopes (measured by isotope-ratio mass spectrometry and secondary ion mass spectrometry) and redox-sensitive detrital grains—reveal that the original Mn-oxide phases were not produced by reactions with O[subscript 2], which points to a different high-potential oxidant. These results show that the oxidative branch of the Mn cycle predates the rise of oxygen, and provide strong support for the hypothesis that the water-oxidizing complex of photosystem II evolved from a former transitional photosystem capable of single-electron oxidation reactions of Mn.en_US
dc.description.sponsorshipAgouron Instituteen_US
dc.language.isoen_US
dc.publisherNational Academy of Sciences (U.S.)en_US
dc.relation.isversionofhttp://dx.doi.org/10.1073/pnas.1305530110en_US
dc.rightsArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.en_US
dc.sourcePNASen_US
dc.titleManganese-oxidizing photosynthesis before the rise of cyanobacteriaen_US
dc.typeArticleen_US
dc.identifier.citationJohnson, J. E., S. M. Webb, K. Thomas, S. Ono, J. L. Kirschvink, and W. W. Fischer. “Manganese-Oxidizing Photosynthesis before the Rise of Cyanobacteria.” Proceedings of the National Academy of Sciences 110, no. 28 (July 9, 2013): 11238–11243.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciencesen_US
dc.contributor.mitauthorThomas, Katherineen_US
dc.contributor.mitauthorOno, Shuheien_US
dc.relation.journalProceedings of the National Academy of Sciencesen_US
dc.eprint.versionFinal published versionen_US
dc.type.urihttp://purl.org/eprint/type/JournalArticleen_US
eprint.statushttp://purl.org/eprint/status/PeerRevieweden_US
dspace.orderedauthorsJohnson, J. E.; Webb, S. M.; Thomas, K.; Ono, S.; Kirschvink, J. L.; Fischer, W. W.en_US
dc.identifier.orcidhttps://orcid.org/0000-0002-1348-9584
mit.licensePUBLISHER_POLICYen_US


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