Chemocline instability and isotope variations of the Ediacaran Doushantuo basin in South China

Jiang, Ganqing; Zhang, Shihong; Shi, Xiaoying; Wang, Xinqiang

doi:10.1007/s11430-008-0116-2

Cited by 40 publications

(26 citation statements)

References 41 publications

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“…Taken together, the evidence suggests that the Ediacaran sedimentary environment in the Guozigou area is similar to the sedimentary environment in South China [48] and the Kuruktag area, Xinjiang [47] at the same age. The character of the sedimentary environment is an oxic and weak hydrodynamic water.…”

Section: Geochemistrymentioning

confidence: 60%

Sedimentary environment of Ediacaran glacigenic diamictite in Guozigou of Xinjiang, China

Ding

Yao

et al. 2009

Chin. Sci. Bull.

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The Talisayi Formation found in the Guozigou region on the southern side of Sayram Lake of Xinjiang, China is a Neoproterozoic glacigenic diamictite succession that has not been adequately researched. According to its isotopic geochronology and regional stratigraphic correlation, the Talisayi Formation is equivalent to the Ediacaran glacial sediments. The present paper provides the geochemical data of the Talisayi Formation that reveals the tectonic setting and sedimentary environment in this area during the Ediacaran period. The oxides of Si, K, Na and Al and their ratios of matrix materials from glacigenic diamictites and bulk rock of siltstone and argillaceous siltstones indicate that the sedimentary environment of this formation evolved from a tectonically active region to a passive continental margin. Values of CIA (carbonate-corrected Chemical Index of Alteration) ranging from 54 to 74 show a low-middle weathering action under a glacial environment. Total organic carbon (TOC), V/Cr, Ni/Co and U/Th ratios suggest that the sediments deposited in shallow water with an oxic and weak hydrodynamic condition. There is an abrupt rise in TOC, V/Cr, Ni/Co and U/Th ratios respectively in the overlying Lower Cambrian dolomitic limestones and in the bottom of Talisayi Formation, indicating a rapidl increase in biologic productivity and a variation in redox conditions, which was probably caused by seawater mixing of deep anoxic water and surface oxic water.Guozigou, Ediacaran, glacigenic diamictite, geochemistry, sedimentary environment Neoproterozoic glacigenic diamictite outcropping around the world and cap carbonates directly covering the glacigenic diamictite indicate the oscillations and sudden changes of climate that were closely related to the breakup of the Rodinia supercontinent, Ediacaran Radiation, and the Cambrian explosion. The "Snowball Earth model" hypothesis [1,2] proposed by Hoffman provided impetus for study of the climate and environment changes in that period. The significance of Neoproterozoic glacigenic diamictite for the Earth climate evolution has since made it a frontier and focus field of global paleoenvironmental research.The frequency of global glaciations happening during the Neoproterozoic remains unambiguous. The Marinoan glaciation that ended in 635 Ma [3] is generally considered to have been the last globally correlated glaciation during the Neoproterozoic. The possibility that there were globally correlated glaciations during the Ediacaran (635-542 Ma, equivalent to Sinian in China), i.e. post-Marinoan glaciations, is now receiving more attention [4,5] .Most Neoproterozoic paleoenvironment and paleoclimate studies focus on stratigraphic carbon isotope analysis [4,6−10] , paleontology, sedimentology and paleomagnetism. However, the research on glacigenic diamictites and interglacial sedimentary clastic rocks is relatively poor, mainly because of the low carbonate content in these rocks. In addition, glacigenic diamictites and interglacial sedimentary clastic rocks were usually

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Section: Geochemistrymentioning

confidence: 60%

Sedimentary environment of Ediacaran glacigenic diamictite in Guozigou of Xinjiang, China

Ding

Yao

et al. 2009

Chin. Sci. Bull.

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“…It is traditionally argued that the carbon isotope records can be used as a useful tool for global correlation of Ediacaran strata, particularly for those sections lacking agediagnostic biostratigraphic markers and/or precise radiometric dating [12][13][14][15] . However, published Ediacaran δ 13 C curves from different continents show major inconsistencies not only in age but also in number and magnitude [9,10] , even in the same basin. In South China, for instance, the carbon isotope variations display great difference between various sedimentary environments [9,10,16] .…”

mentioning

confidence: 99%

“…Unusually negative carbon isotope anomalies (with magnitude from ≥+5‰ down to ≤−12‰) have been documented in the Ediacaran succession over the world [1][2][3][4][5][6][7][8][9][10][11] . These great perturbations in carbon cycling, which are much more prominent and widespread than any other intervals in the Earth history, apparently imply an abnormal Ediacaran seawater chemistry [10] .…”

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confidence: 99%

“…These great perturbations in carbon cycling, which are much more prominent and widespread than any other intervals in the Earth history, apparently imply an abnormal Ediacaran seawater chemistry [10] . It is traditionally argued that the carbon isotope records can be used as a useful tool for global correlation of Ediacaran strata, particularly for those sections lacking agediagnostic biostratigraphic markers and/or precise radiometric dating [12][13][14][15] .…”

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confidence: 99%

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Spatio-temporal carbon isotope variation during the Ediacaran period in South China and its impact on bio-evolution

Wang

Shi

2009

Sci. China Ser. D-Earth Sci.

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The Ediacaran period is characterized by the extremely negative carbon isotope anomalies and great biotic evolution in Earth history. At least four negative carbon isotope anomalies have been reported from this interval in South China so far. It is traditionally argued that the isotope variations can be used as a useful tool for global correlation of Ediacaran succession; however, more and more researches argued against this idea. We reviewed the previously published carbon isotope data in South China, and distributed the mean values of a certain time to the paleogeographic maps. The results show that the carbon isotope values (δ 13 C) vary greatly in different environments, but a clear tendency of becoming lighter from shallow platform to deep basin, with a maximum variation up to 11‰. Moreover, the important changes in Ediacaran biota, marked by the introducing of new taxa or ecologic groups, seemed to always postdate the negative anomalies but coincide with the positive shift. If the negative excursions represented the oxidation of a large dissolved organic carbon (DOC) reservoir in the ocean, the diverse Ediacaran organisms and the carbon isotope anomalies may suggest totally different environments: oxic and anoxic/euxinic. We also suggest that the elimination of euxinic state through precipitation of pyrites is one of the important environment factors in prompting the Ediacaran bio-evolution.

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“…Recently, researches on the Neoproterozoic "snowball Earth events" [7,8], Rodinia supercontinent [9] and cap carbonates [10][11][12][13] have made the Neoproterozoic glacial events as new focus around the international geology community. In China, the Neoproterozoic successions are dominated by carbonates and are mostly distributed in the Tarim [14,15], North China [16] and South China [17][18][19] blocks. Previous work mainly focuses in the Quruqtagh area of the Tarim Block and the Three Gorges area of the South China Block.…”

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confidence: 99%

Carbon and oxygen isotopes analyses for the Sinian carbonates in the Helan Mountain, North China

et al. 2013

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We conducted detailed studies of the Sinian carbonates from the Helan Mountain, Ningxia by both field investigation and laboratory analyses of carbon and oxygen isotopes. The carbon isotopic compositions of the Sinian Zhengmuguan Formation shows variations with regularity in the five studied sections, the δ 13 C values all gradually decrease from bottom to top, with a total range from −4.51‰ to 0.11‰, and the biggest negative excursion reaches up to −6.88‰. In addition, abundant macro-body fossils were also found from the Tuerkeng Formation in this study, similar to those found from the Dengying Formation in the South China Block. This observation firmly constrained the age for the Zhengmuguan and Tuerkeng formations to the Sinian period. Here we interpreted that the Zhengmuguan Formation formed during a glacial period when the extremely cold climate substantially decreased the amount of burial of organic matter in the ocean and thus led to the general negative δ 13 C excursion. The increasing δ 13 C values in the Tuerkeng Formation dolomites imply the ending of the glacial period in the Zhengmuguan epoch, biological recovery and increase of organic matter burial in the ocean occurred during this period. Comparing our obtained carbon and oxygen isotopes of the Zhengmuguan and Tuerkeng formations with those of coeval carbonate successions from other places all over the world, the Zhengmuguang-aged glacial deposits might be deposited after the Gaskiers glaciation. This study provides important information for paleo-ocean, paleogeographic and biological evolution in the North China Block during the Ediacaran period and adds new carbon and oxygen isotopes data for the global Sinian carbon-oxygen isotopes dataset. carbon and oxygen isotopes, Sinian carbonate, Helan Mountain, Glacial deposits Citation:Yang J, Zeng Z X, Cai X F, et al. Carbon and oxygen isotopes analyses for the

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Chemocline instability and isotope variations of the Ediacaran Doushantuo basin in South China

Cited by 40 publications

References 41 publications

Sedimentary environment of Ediacaran glacigenic diamictite in Guozigou of Xinjiang, China

Sedimentary environment of Ediacaran glacigenic diamictite in Guozigou of Xinjiang, China

Spatio-temporal carbon isotope variation during the Ediacaran period in South China and its impact on bio-evolution

Carbon and oxygen isotopes analyses for the Sinian carbonates in the Helan Mountain, North China

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