Large-scale slope instability at the southern margin of the Ediacaran Yangtze platform (Hunan province, central China)

Vernhet, E.; Heubeck, Christoph; Zhu, Maoyan; Zhang, J.-M.

doi:10.1016/j.precamres.2006.03.009

Cited by 45 publications

(12 citation statements)

References 39 publications

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“…Given the fact that unit II carbonates record negative d 13 C carb values (À4 to À9) we believe that they were deposited in deeper realms of the Yangtze Platform and not under shallow marine conditions as Vernhet et al (2006) postulated. The negative Ce-anomalies of unit II would therefore argue for short intervals of suboxic to oxic conditions in the basin at still anoxic to sulfidic pore-water conditions in the sediments.…”

Section: Origin Of Abundance Variations Of Redox-sensitive Elementsmentioning

confidence: 69%

“…A 35 m thick unit, starting with a poorly developed basal phosphorite hard ground, followed by organic-poor dolomite pack-and grainstones and organic-rich muddy dolostones, overlies these strata. This unit also includes micritic phosphorites, biolaminations and possibly current related sedimentary structures and was interpreted as a massive submarine slide block of shallow-water origin (Vernhet et al, 2006;Vernhet, 2007). The carbonate unit is overlain by partly brecciated dolostones and mudstones, containing chert layers and nodules (5 m).…”

Section: Geological Settingmentioning

confidence: 99%

“…According to their stratigraphic position, petrologic description and TOC concentrations we have divided the samples used for this study into four subgroups (see Fig. 2): The section contains smaller allochthonous slide blocks and olistoliths with a variety of sedimentological facies, such as tepees and ripples which has been used to argue for a shallow-water origin of unit II and III lithologies and mass flow transport of parts of the section into deeper environments (Vernhet et al, 2006. We note, however, that d 13 C carb values are negative at about À4 to À9 throughout the Yanwutan section (Guo et al, 2007) as for other slope or deep-water sections on the Yangtze Platform (Ader et al, 2009).…”

Section: Geological Settingmentioning

confidence: 99%

“…2). The only unit that might indicate oxic conditions is therefore unit II, which begins above a phosphoritic hardground at 21 m and which has been discussed as being part of a allochthonous slide sheet which may have originated at shallower slope or platform edge conditions (Vernhet et al, 2006.…”

Section: Origin Of Abundance Variations In Ree+ymentioning

confidence: 99%

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Multiproxy constraints on alteration and primary compositions of Ediacaran deep-water carbonate rocks, Yangtze Platform, South China

Hohl

Becker

Herzlieb

et al. 2015

Geochimica et Cosmochimica Acta

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The occurrence of shallow and deep-water sedimentary facies has established the Yangtze Platform in South China as a key site for the study of Neoproterozoic ocean oxidation and Ediacaran animal evolution following the Marinoan glaciation. The Yanwutan section in Hunan Province is one of the few coherent sections on the Yangtze Platform where Ediacaran deep-water carbonate sediments (predominantly dolostones) are preserved together with organic carbon-rich shales. Here we present new major and trace element abundance data as well as Sr-, O-and C-isotope compositions of leachates from carbonates of the Doushantuo Formation. We evaluate the role of diagenetic modification of the carbonate rocks and constrain the redox evolution of Ediacaran seawater in space and time. 87 O of cap dolostones at many other sections were compromised by hydrothermal alteration. The overlying organic carbon poor micritic dolostone (unit II) shows negative Ce-anomalies that disappear towards the top of the unit. No Ce-anomalies occur in subsequent organic carbon-rich muddy dolostone units (units III to IV). These observations, enrichments in TOC that correlate with variations in redox-sensitive metals in the carbonates, negative d 13 C carb in units II to IV and the decoupling of d 13 C carb from d 13 C org argue for the existence of mostly anoxic deep-water at the Yangtze passive continental margin during the Ediacaran. The negative Ce-anomalies at the base of unit II (with negative d 13 C carb ) may reflect fluctuations towards suboxic or oxic conditions or an allochthonous origin of this unit. However, trace metal enrichments in carbonates of the same unit argue for reducing conditions in pore-water, whereas the carbonates may have preserved the REE+Y signatures inherited from suboxic-to oxic seawater. The trace element and negative d 13 C carb values in units II to IV are consistent with a stratified basin model with a large partially remineralised organic matter reservoir in anoxic bottom and pore-waters.

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Section: Origin Of Abundance Variations Of Redox-sensitive Elementsmentioning

confidence: 69%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Origin Of Abundance Variations In Ree+ymentioning

confidence: 99%

See 2 more Smart Citations

Multiproxy constraints on alteration and primary compositions of Ediacaran deep-water carbonate rocks, Yangtze Platform, South China

Hohl

Becker

Herzlieb

et al. 2015

Geochimica et Cosmochimica Acta

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“…1). The cap dolostones and overlying mudstones of the lower Doushantuo at Yanwutan were deposited in deep waters of the Nantuo Basin (Guo et al, 2007;Zhu et al, 2007;Ader et al, 2009) whereas the middle and upper Doushantuo are considered to be composed of a massive slide sheet from a more shallow water environment (Vernhet et al, 2006). However, Guo et al (2007) and Hohl et al (2015) have shown that negative δ…”

Section: Geological Settingmentioning

confidence: 99%

Chromium isotope stratigraphy of Ediacaran cap dolostones, Doushantuo Formation, South China

2016

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The Yangtze Platform in South China is considered a key site for studying Neoproterozoic ocean oxygenation. Comprehensive Cr concentration and isotopic signatures are presented from cap dolostones of the Doushantuo Formation from a deep water and a shallow marine carbonate section, that have previously been used to constrain the redox evolution of Ediacaran seawater in space and time employing major and trace element abundances as well as Sr-, O-and C-isotope compositions. The majority of the studied samples yield elevated Cr concentrations and negatively fractionated δ Sr signal close to Ediacaran seawater values with relatively high Sr and Cr concentrations, with decreased detrital contamination and with a pronounced negative Ce anomaly. They indicate either light pulses of enhanced oxidative weathering or, inferred from a few leastaltered samples, prevailing oxic conditions during cap dolostone deposition. The Cr isotopic composition of Ediacaran cap dolostones pertaining to the Doushantuo Formation reveals fine-scale fluctuations in postglacial detrital contamination and diagenesis balanced against a clear signal of oxidative weathering. Cr isotopes have the potential to further enhance our understanding of Neoproterozoic weathering regimes and past ocean oxygenation, however, before the Cr isotope system can be faithfully applied to delineate changes in redox conditions recorded in ancient marine carbonates, possible diagenetic alteration of the Cr signal as well as Cr contribution from detrital contamination need to be taken into consideration.

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Early Cambrian highly metalliferous black shale in South China: Cu and Zn isotopes and a short review of other non-traditional stable isotopes

et al. 2022

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Early Cambrian black shales on the Yangtze Platform host a regionally distributed highly metalliferous sulfide-rich carbonaceous unit which has been the subject of extensive debate. This marker unit, with a few centimeters or tens of centimeters in thickness, displays extreme enrichment in Mo and Ni (wt% range), and in a broad spectrum of other metals such as As, Au, PGE, Re, Cu, Zn, Cd, Ag, Sb, Se, Tl, and Hg, and occurs discontinuously along the western passive margin of the Yangtze Platform. It grades laterally in stratigraphically equivalent meter-thick vanadium-rich shale and tens-of-meter-thick sapropelite (combustible shale). New Cu and Zn isotope data, combined with existing Cd, Cr, Ni, Mo, Hg, and Se isotope and other chemical data, allow to attempt an integrated view on the formation of this intriguing unit of hyper-enriched metalliferous black shale. The authigenic Cu enrichment in the 1000-ppm range has produced no or little Cu isotope fractionation (0.03 ± 0.26 ‰ δ65Cu) beyond the lithogenic background. Heavy zinc and cadmium isotope enrichment in the sulfidic samples (1.11 ± 0.18 ‰ δ66Zn, 0.31 ± 0.10 ‰ δ114Cd) is controlled by sulfide fractionation and contrasts with V-rich and barren shale (0.60 ± 0.18 ‰ δ66Zn, 0.00 ± 0.14 ‰ δ114Cd). The distinctly negative Ni isotope composition of the metalliferous unit (−0.84 ± 0.05 ‰ δ60Ni) with Ni in the percent range has been interpreted as due to hydrothermal activity related to the leaching of mafic rocks and their sulfides. Sorption processes (Fe-oxyhydroxides) and redox cycling in the water column and the bottom sediment with microbial activity could be an alternative interpretation. The extreme metal enrichment can be understood as due to a process chain, from high biological productivity in the oxic photic zone to sulfate reduction in the deeper sulfidic water column and upper sediment layer. Key to the metal enrichment seems to be extremely low clastic sedimentation and advanced carbon destruction by anaerobic oxidation. Hydrothermal input of basinal brines along the rifted margin of the Yangtze Platform was likely a part of this scenario.

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Large-scale slope instability at the southern margin of the Ediacaran Yangtze platform (Hunan province, central China)

Cited by 45 publications

References 39 publications

Multiproxy constraints on alteration and primary compositions of Ediacaran deep-water carbonate rocks, Yangtze Platform, South China

Multiproxy constraints on alteration and primary compositions of Ediacaran deep-water carbonate rocks, Yangtze Platform, South China

Chromium isotope stratigraphy of Ediacaran cap dolostones, Doushantuo Formation, South China

Early Cambrian highly metalliferous black shale in South China: Cu and Zn isotopes and a short review of other non-traditional stable isotopes

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