Was the Ediacaran Shuram Excursion a globally synchronized early diagenetic event? Insights from methane-derived authigenic carbonates in the uppermost Doushantuo Formation, South China

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dc.contributor.authorCui, Huanen
dc.contributor.authorKaufman, Alan J.en
dc.contributor.authorXiao, Shuhaien
dc.contributor.authorZhou, Chuanmingen
dc.contributor.authorLiu, Xiao-Mingen
dc.contributor.departmentGeosciencesen
dc.date.accessioned2017-02-13T20:00:33Zen
dc.date.available2017-02-13T20:00:33Zen
dc.date.issued2017-02en
dc.description.abstractThe Ediacaran Period is characterized by the most profound negative carbon isotope (δ13C) excursion in Earth history, the ShuramExcursion. Various hypotheses – including the massive oxidation of dissolved organic carbon (DOC) in the oceans, the weathering of terrestrial organic carbon, or the release and oxidation of methane hydrates and/or expelled petroleum from the subsurface – have been proposed as sources of the 13C-depleted carbon. More recently, it has been suggested that global-scale precipitation of early authigenic carbonates, driven by anaerobicmicrobial metabolism in unconsolidated sediments, may have caused the Shuram Excursion, but empirical evidence is lacking. Here we present a comprehensive analysis of a Shuram-associated interval from the uppermost Doushantuo Formation in South China. Our study reveals petrographic evidence of methane-derived authigenic calcite (formed as early diagenetic cements and nodules) that are remarkably depleted in 13C – suggesting a buildup of alkalinity in pore fluids through the anaerobic oxidation of methane (AOM) – and systematically depleted in 18O relative to co-occurring dolomite. Early authigenesis of these minerals is likely to be driven by increased microbial sulfate reduction, triggered by enhanced continental weathering in the context of a marked rise in atmospheric oxygen levels. In light of the finding of methane-derived authigenic carbonates at Zhongling, and based on our basin-scale stratigraphic correlation, we hypothesize that the marked 13C and 18O depletion (including their co-variation noted worldwide) in the Shuram Excursion may reflect an episode of authigenesis occurring within a sulfate–methane transition zone (SMTZ). If true, the Shuram Excursion was then a global biogeochemical response to enhanced seawater sulfate concentration in the Ediacaran ocean driven by the Neoproterozoic oxidation of surface environments. This paleo-oceanographic transition may have therefore paved theway for subsequent evolution and diversification of animals. Our study highlights the significance of an integrated approach that combines petrography, mineralogy, and texture-specificmicro-drilling geochemistry in chemostratigraphic studies.en
dc.description.notespublisher: Elsevier articletitle: Was the Ediacaran Shuram Excursion a globally synchronized early diagenetic event? Insights from methane-derived authigenic carbonates in the uppermost Doushantuo Formation, South China journaltitle: Chemical Geology articlelink: http://dx.doi.org/10.1016/j.chemgeo.2016.12.010 content_type: article copyright: © 2016 Elsevier B.V. All rights reserved.en
dc.description.versionPublished versionen
dc.format.extent59 - 80 page(s)en
dc.identifier.doihttps://doi.org/10.1016/j.chemgeo.2016.12.010en
dc.identifier.issn0009-2541en
dc.identifier.urihttp://hdl.handle.net/10919/75019en
dc.identifier.volume450en
dc.language.isoenen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.titleWas the Ediacaran Shuram Excursion a globally synchronized early diagenetic event? Insights from methane-derived authigenic carbonates in the uppermost Doushantuo Formation, South Chinaen
dc.title.serialChemical Geologyen
dc.typeArticle - Refereeden
pubs.organisational-group/Virginia Techen
pubs.organisational-group/Virginia Tech/All T&R Facultyen
pubs.organisational-group/Virginia Tech/Scienceen
pubs.organisational-group/Virginia Tech/Science/COS T&R Facultyen
pubs.organisational-group/Virginia Tech/Science/Geosciencesen

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