Phosphogenesis associated with the Shuram Excursion: Petrographic and geochemical observations from the Ediacaran Doushantuo Formation of South China

Cui, Huan; Xiao, Shuhai; Zhou, Chuanming; Peng, Yongbo; Kaufman, Alan J.; Plummer, Rebecca E.

doi:10.1016/j.sedgeo.2016.05.008

Cited by 68 publications

(55 citation statements)

References 112 publications

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“…1). The detailed geology of these sections has been described in previous publications (see McFadden et al, 2008;Jiang et al, 2011;Cui et al, 2015;Cui et al, 2016c). The Jiulongwan section preserves a typical Shuram Excursion (i.e., the EN3 interval in McFadden et al, 2008), with carbonate δ 13 C values consistently around − 9‰ in the upper 50 m of the Doushantuo Formation.…”

Section: Methodsmentioning

confidence: 81%

“…5-7) were conducted. All isotope analyses were performed using routine methods (e.g., McFadden et al, 2008;Cui, 2015;Cui et al, 2015Cui et al, , 2016aCui et al, , 2016bCui et al, , 2016c, which are briefly outlined below.…”

Section: Methodsmentioning

confidence: 99%

“…Data were corrected via automated MATLAB scripting on the VPDB and LSVEC scale using periodic in-run measurement of international reference carbonate materials and in-house standard carbonates, from which empirical corrections for signal amplitude, sequential drift, and one or two-point mean corrections were applied (Evans et al, 2016 Sr) were analyzed for selected limestone and calcite nodule samples at the UMD Thermal Ionization Mass Spectrometry (TIMS) Laboratory. Detailed method has been fully described in our previous publications (Cui et al, , 2016a(Cui et al, , 2016c Sr = 0.710245 ± 0.000011 (2σ) during the analytical window.…”

Section: Methodsmentioning

confidence: 99%

“…(C) Simplified litho-, bio-, and chrono-stratigraphy of the Ediacaran Doushantuo and Dengying formations in South China. Modified from Chen et al (2013) and Cui et al (2016c). Radiometric ages from Condon et al (2005) and Schmitz (2012).…”

Section: Sedimentology Petrography and Paragenesismentioning

confidence: 99%

“…This profound carbon cycle anomaly is further characterized by: (1) covariations of carbon and oxygen isotopes in carbonates (Derry, 2010a;Grotzinger et al, 2011), (2) decoupling between carbonate carbon and organic carbon isotope compositions (Fike et al, 2006;McFadden et al, 2008;Lee et al, 2013), (3) a strong negative δ 34 S excursion recorded in both pyrite and carbonate-associated sulfate (CAS) (Fike et al, 2006;Kaufman et al, 2007;McFadden et al, 2008), and (4) a progressive increase in 87 Sr/ 86 Sr isotopes (Melezhik et al, 2009;Sawaki et al, 2010;Cui et al, 2015;Xiao et al, 2016). This negative δ 13 C excursion may result from the influence of 13 C-depleted authigenic carbonates Schrag et al, 2013;Cui et al, 2016c), but to evaluate this possibility requires new detailed petrographic and geochemical data.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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The Ediacaran Period is characterized by the most profound negative carbon isotope (δ 13 C) excursion in Earth history, the Shuram Excursion. 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 13 C-depleted carbon. More recently, it has been suggested that global-scale precipitation of early authigenic carbonates, driven by anaerobic microbial 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 13 C -suggesting a buildup of alkalinity in pore fluids through the anaerobic oxidation of methane (AOM) -and systematically depleted in 18 O 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 13 C and 18 O 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 the way for subsequent evolution and diversification of animals. Our study highlights the significance of an integrated approach that combines petrography, mineralogy, and texture-specific micro-drilling geochemistry in chemostratigraphic studies.

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