Evolution from an anoxic to oxic deep ocean during the Ediacaran–Cambrian transition and implications for bioradiation

Wang, Jianguo; Chen, Daizhao; Yan, Detian; Wei, Hengye; Xiang, Lei

doi:10.1016/j.chemgeo.2012.03.005

Cited by 154 publications

(101 citation statements)

References 93 publications

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“…During the early Cambrian Stage 3, less anoxic environments have been supported by Fe speciation data from the middle part of the Niutitang (Jiumenchong) Formation in Zhongnan section, Guizhou , Yangjiaping section, Hunan (Feng et al, 2014), Songtao section, Guizhou (Canfield et al, 2008), and Longbizui section, Hunan (Wang et al, 2012a), suggesting dominantly ferruginous conditions, with mid-depth euxinic conditions retreating from the shelf margin to the slope areas, and even occasionally oxic bottom waters in the shelf margin and upper-slope area (Feng et al, 2014;Jin et al, 2014) (Fig. 6c).…”

Section: Early Cambrian Stagementioning

confidence: 77%

“…The shelf regions of the Yangtze block were subaerially exposed and partially eroded during the earliest Cambrian, but a transgression during Cambrian Stage 2 (∼early Tommotian) submerged the shelf margins and led to homogeneous deposition of fine-grained, frequently organic-rich sediments across the entire Yangtze block Steiner et al, 2007;Zhu et al, 2003). These 'black shales' are suggested to have been deposited under widespread anoxic, or even euxinic conditions based on numerous lines of geochemical evidence (Canfield et al, 2008;Goldberg et al, 2005Goldberg et al, , 2007Guo et al, 2007a;Kimura and Watanabe, 2001;Lehmann et al, 2007;Och et al, 2013;Wang et al, 2012a;Wille et al, 2008;Xu et al, 2012). Presumably, because of the rapidity of this sea level rise, lower Cambrian units across much of South China are condensed with only a few centimeters thickness in the deeper water realms (Goldberg et al, 2007;Schütter, 1998;Steiner et al, 2001Steiner et al, , 2007.…”

Section: Geological Settingmentioning

confidence: 99%

“…Currently available Fe speciation data indicate that euxinic waters were not widespread during the latest Ediacaran -the earliest Cambrian interval and that the water column was stratified with an oxygenated upper layer overlying a ferruginous deepwater column in the basin of South China (Canfield et al, 2008;Chen et al, 2015;Feng et al, 2014;Goldberg et al, 2007;Och, 2011;Och et al, 2013;Wang et al, 2012a) (Fig. 6a).…”

Section: Cambrian Fortunian Stagementioning

confidence: 99%

“…Based on published Fe speciation data (Canfield et al, 2008;Chen et al, 2015;Feng et al, 2014;Jin et al, 2014;Och, 2011;Och et al, 2013;Wang et al, 2012a), the Liuchapo and Niutitang formations (and correlative formations) were mostly deposited under anoxic conditions. Anaerobic degradation of organic matter during early diagenesis retains the initial ␦ 15 N value or decreases ␦ 15 N only to a slight extent (less than 2‰) (Freudenthal et al, 2001;Möbius et al, 2010;Robinson et al, 2012).…”

Section: Evaluation Of Nitrogen Isotope Datamentioning

confidence: 99%

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Marine redox variations and nitrogen cycle of the early Cambrian southern margin of the Yangtze Platform, South China: Evidence from nitrogen and organic carbon isotopes

Wang

Struck

Guo

et al. 2015

Precambrian Research

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Section: Early Cambrian Stagementioning

confidence: 77%

Section: Geological Settingmentioning

confidence: 99%

Section: Cambrian Fortunian Stagementioning

confidence: 99%

Section: Evaluation Of Nitrogen Isotope Datamentioning

confidence: 99%

See 2 more Smart Citations

Marine redox variations and nitrogen cycle of the early Cambrian southern margin of the Yangtze Platform, South China: Evidence from nitrogen and organic carbon isotopes

Wang

Struck

Guo

et al. 2015

Precambrian Research

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“…Although numerous mechanisms have been proposed to account for the co-evolution of these processes, controversies remain. Of these, the extinction of Ediacaran fauna, and subsequent advent and accelerated diversification of skeletonized metazoans concomitant with drastic shifts in oceanic environment and geochemistry have been topics of extensive discussions (Grotzinger et al 1995;Knoll and Carroll 1999;Amthor et al 2003;Marshall 2006;Maloof et al 2010;Wang et al 2012b). …”

Section: Introductionmentioning

confidence: 99%

Submarine silica-rich hydrothermal activity during the earliest Cambrian in the Tarim Basin, Northwest China

Zhou

Chen

Qing

et al. 2014

International Geology Review

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Siliceous rocks were widely deposited in many continents during the Ediacaran-Cambrian (E-C) transition. Based on detailed field investigations in the Aksu area of the Tarim Basin in Northwest China, this study presents evidence of a submarine silica-rich hydrothermal system preserved in the E-C boundary successions. This system consists of a lower stockwork silica-dominant vein swarm zone in the karstified dolostone of the uppermost Ediacaran Qigebulake Formation, which terminates directly under the overlying bedded chert and black shale succession of the lowermost Cambrian Yurtus Formation. The stockwork vein swarms were filled dominantly by a wide spectrum of silica precipitates (amorphous silica, chalcedony, spherulite, fine to coarse quartz) with subordinate pyrite, Fe-(oxyhydr)oxide, and barite. The host dolostones that were dissected by the vein swarms also suffered extensive silicification and recrystallization. The vertical stacking relationship of silica-dominant vein swarms and overlying bedded chert suggests they were formed by an identical lowtemperature, silica-rich diffusive submarine hydrothermal system in the earliest Cambrian. This suggestion is further supported by fluid inclusion microthermometry (T h 40-200°C) of the quartz-barite vein fills. In this case, silica-rich hydrothermal fluids were channelled and precipitated partially along the stockwork veins in the antecedent karstified dolostone and vented mostly into seawater, promoting widespread deposition of bedded chert on the seafloor of Tarim Basin in the earliest Cambrian. This study provides a useful clue and analogue to understand the widespread silica deposition and coeval vast oceanic and geochemical changes during the E-C transition in the Tarim Basin and elsewhere.

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Germanium/silicon of the Ediacaran-Cambrian Laobao cherts: Implications for the bedded chert formation and paleoenvironment interpretations

Dong

Shen

Lee

et al. 2015

Geochem. Geophys. Geosyst.

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Sedimentary strata of the terminal Ediacaran (635-542 Ma) to early Laobao-Liuchapo bedded cherts in the South China Block include the Ediacaran Oxidation Event and the Cambrian explosion. Understanding the origin and depositional environment of the bedded cherts may provide insight into how the Earth's surface environment changed between the Proterozoic and Phanerozoic. We measured major and trace element compositions and Ge/Si ratios of the Laobao cherts from northern Guangxi province. The Laobao cherts were deposited in the deep basinal environment of the South China Block. We show that the composition of the Laobao cherts is determined by a mixture of four components: quartz, clay, carbonate, and pyrite/iron-oxide. The quartz component is the dominant component of the Laobao cherts. The maximum estimated Ge/Si of the quartz component is between 0.4 and 0.5 lmol/ mol, which is close to the Ge/Si of modern seawater and biogenic silica but 1 order of magnitude lower than that of hydrothermal fluids. These Ge/Si systematics suggest that normal seawater rather than midocean ridge hydrothermal fluids is the primary Si source for the Laobao cherts. The Ge/Si of the clay component varies between 1 and 10 lmol/mol, which is comparable to the Ge/Si of typical marine clays, but 10-100 times lower than that of chert nodules from early Ediacaran beds (the Doushantuo Formation) predating the terminal Ediacaran Laobao cherts studied here. Our observations indicate that the clay component Ge/Si ratio decreased from the early Ediacaran to the late Ediacaran. We speculate that high Ge/Si ratios in clays reflect the preferential chelation of Ge by dissolved organic compounds adsorbed onto clays. If so, this suggests that the decrease in Ge/Si ratio of the clay component in the Ediacaran signifies a decrease in the total dissolved organic carbon content of seawater toward the Ediacaran-Cambrian transition, consistent with oxidation of the oceans during the late Ediacaran. Finally, the seawater origin of the Laobao cherts also suggests that replacement of carbonate may not be the primary cause for bedded chert formation. Instead, direct precipitation from seawater or early diagenetic silicification of calcareous sediments, perhaps due to the emergence of Si-accumulation bacteria, may have been responsible for the bedded Laobao-Liuchapo chert formation in South China Block.

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Evolution from an anoxic to oxic deep ocean during the Ediacaran–Cambrian transition and implications for bioradiation

Cited by 154 publications

References 93 publications

Marine redox variations and nitrogen cycle of the early Cambrian southern margin of the Yangtze Platform, South China: Evidence from nitrogen and organic carbon isotopes

Marine redox variations and nitrogen cycle of the early Cambrian southern margin of the Yangtze Platform, South China: Evidence from nitrogen and organic carbon isotopes

Submarine silica-rich hydrothermal activity during the earliest Cambrian in the Tarim Basin, Northwest China

Germanium/silicon of the Ediacaran-Cambrian Laobao cherts: Implications for the bedded chert formation and paleoenvironment interpretations

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