New paleomagnetic results from the Ediacaran Doushantuo Formation in South China and their paleogeographic implications

Zhang, Shihong; Li, Haiyan; Jiang, Ganqing; Evans, David A.D.; Jia, Dong; Wu, Huaichun; Yang, Tianshui; Liu, Pengju; Xiao, Qiuping

doi:10.1016/j.precamres.2014.09.018

Cited by 120 publications

(61 citation statements)

References 79 publications

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“…In this case, the precipitation of pre‐Silurian terrestrial carbonates is supposed to be related to six other degassing mechanisms (temperature rise, deep‐sourced CO 2 , evaporation, common‐ion effect, freeze‐out and boiling springs; Brasier, ). Because the cavity network of the Dengying Formation was developed in an exposed tropical carbonate platform (Zhang et al ., ), temperature rise or freeze‐out below the surface was unlikely. In addition, there is no evidence for deep‐sourced CO 2 , boiling springs, strong air flow below the surface (triggering evaporation) and dissolution of massive gypsum (inducing common‐ion effect).…”

Section: Interpretation and Discussionmentioning

confidence: 99%

Cavity‐filling dolomite speleothems and submarine cements in the Ediacaran Dengying microbialites, South China: Responses to high‐frequency sea‐level fluctuations in an ‘aragonite–dolomite sea’

et al. 2019

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Speleothems, mostly composed of calcium carbonate, are widely present in modern karst‐originated caves, but have rarely been reported in palaeokarst systems. This study presents a novel type of dolomite speleothem and subsequent submarine dolomite cement, which are widely present in the upper Ediacaran Dengying Formation in the upper Yangtze area. These precipitated materials occur in the cavity system that cuts across several peritidal cycles. The interconnected cavity networks with irregular shapes, embayed walls, internal breccias on cavity floor and their preferential development in the shallower cycle tops (for example, tepee‐deformed beds) suggest that they were initially generated by subaerial dissolution. As the earliest infills, the hemispherical protrusions, icicle‐like pendants and ground‐up columns show similar morphological features and occurrence patterns to the cave popcorn, stalactites and stalagmites, respectively. Thus, these earliest infills are speleothems resulting from associated meteoric precipitation during subaerial exposure. The isopachous growth pattern of subsequent more extensive fibrous dolomite cements points to a submarine diagenetic environment in which they were precipitated. Microscopically, the micritic to micro‐crystalline dolomite, acicular dolomite in speleothems and the subsequent fibrous dolomite share similar crystal fabrics to metastable precursors (for example, Mg‐calcite). Meanwhile, the carbon‐oxygen isotope compositions of the speleothem and fibrous dolomite, although partly altered by burial diagenesis, share a large overlap with host rock and coeval marine carbonates all over the Yangtze Platform. For these reasons, these speleothems and fibrous cements are considered to have been initially precipitated as metastable carbonate precursors in meteoric and submarine environments, respectively, and stabilized during submarine mimetic dolomitization. The cyclic occurrence of cavity systems filled with speleothems and submarine cements reflects periodic subaerial exposure and marine flooding of broad tidal flat in the upper Yangtze area, driven by high‐frequency sea‐level fluctuations. Furthermore, the Neoproterozoic seawater chemistry that favoured early dolomitization of carbonate precursor mineralogies was an advantage for the preservation of fabrics from metastable precursor minerals.

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Section: Interpretation and Discussionmentioning

confidence: 99%

Cavity‐filling dolomite speleothems and submarine cements in the Ediacaran Dengying microbialites, South China: Responses to high‐frequency sea‐level fluctuations in an ‘aragonite–dolomite sea’

et al. 2019

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“…B,C; Jiang et al ., ), a passive margin developed in the southeastern side of the Yangtze Block (YB) that was well connected with the open ocean during the Ediacaran–early Cambrian (Fig. A; Jiang et al ., ; Zhang et al ., , ), and (2) relatively complete Ediacaran strata in this section are enriched in black shales that allow currently available redox proxies to capture paleoceanographic signals.…”

Section: Introductionmentioning

confidence: 99%

Oceanic oxygenation events in the anoxic Ediacaran ocean

et al. 2016

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The ocean-atmosphere system is typically envisioned to have gone through a unidirectional oxygenation with significant oxygen increases in the earliest (ca. 635 Ma), middle (ca. 580 Ma), or late (ca. 560 Ma) Ediacaran Period. However, temporally discontinuous geochemical data and the patchy metazoan fossil record have been inadequate to chart the details of Ediacaran ocean oxygenation, raising fundamental debates about the timing of ocean oxygenation, its purported unidirectional rise, and its causal relationship, if any, with the evolution of early animal life. To better understand the Ediacaran ocean redox evolution, we have conducted a multi-proxy paleoredox study of a relatively continuous, deep-water section in South China that was paleogeographically connected with the open ocean. Iron speciation and pyrite morphology indicate locally euxinic (anoxic and sulfidic) environments throughout the Ediacaran in this section. In the same rocks, redox sensitive element enrichments and sulfur isotope data provide evidence for multiple oceanic oxygenation events (OOEs) in a predominantly anoxic global Ediacaran-early Cambrian ocean. This dynamic redox landscape contrasts with a recent view of a redox-static Ediacaran ocean without significant change in oxygen content. The duration of the Ediacaran OOEs may be comparable to those of the oceanic anoxic events (OAEs) in otherwise well-oxygenated Phanerozoic oceans. Anoxic events caused mass extinctions followed by fast recovery in biologically diversified Phanerozoic oceans. In contrast, oxygenation events in otherwise ecologically monotonous anoxic Ediacaran-early Cambrian oceans may have stimulated biotic innovations followed by prolonged evolutionary stasis.

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“…India (I) and south China (SC) were reconstructed following their relative position to Australia proposed byZhang et al (2015) (option I). The inferred position of the subduction zones (red line) and of the domes projected on the surface (yellow small circle) is indicated.…”

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confidence: 99%

True Polar Wander: A Key Indicator for Plate Configuration and Mantle Convection During the Late Neoproterozoic

Robert

Greff-Lefftz

Besse

2018

Geochem Geophys Geosyst

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Large polar motions are observed in the apparent polar wander paths of several continents during the Ediacaran. Among various hypotheses proposed in the literature, one consists of the occurrence of two successive fast and large true polar wander (TPW) episodes, from 615 to 590 Ma and then between 575 and 565 Ma. In this study, we explored the effect of the reactivation of a girdle of subduction to produce such TPW. First, we performed a reconstruction of the main continents between 615 and 520 Ma including Laurentia, Baltica, west and central Gondwana, and Australia‐Antarctica. We then implemented this paleogeography into a simple mantle dynamic model to calculate the TPW during the Ediacaran. Our results show that the reactivation of a girdle of subduction surrounding the continents along with a reduced effect of the return flow rising from the lower mantle can produce two TPW episodes consistent with the paleomagnetic observations. This mechanism is possible if the sinking velocities associated with the girdle of subduction drastically decrease between 635 and 730 Ma. Such a large geodynamic event is consistent with the detrital zircon age distribution of the Neoproterozoic supporting a low subduction activity during the Cryogenian and a boost during the Ediacaran. Decrease of subduction‐related stress induced on the lithosphere may have interrupted the rifting of the supercontinent Rodinia for 100 Ma. Finally, the weakening in subduction magmatism might have strongly reduced the CO2 flux into the atmosphere and played a major role in driving the Neoproterozoic global‐scale glaciations.

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New paleomagnetic results from the Ediacaran Doushantuo Formation in South China and their paleogeographic implications

Cited by 120 publications

References 79 publications

Cavity‐filling dolomite speleothems and submarine cements in the Ediacaran Dengying microbialites, South China: Responses to high‐frequency sea‐level fluctuations in an ‘aragonite–dolomite sea’

Cavity‐filling dolomite speleothems and submarine cements in the Ediacaran Dengying microbialites, South China: Responses to high‐frequency sea‐level fluctuations in an ‘aragonite–dolomite sea’

Oceanic oxygenation events in the anoxic Ediacaran ocean

True Polar Wander: A Key Indicator for Plate Configuration and Mantle Convection During the Late Neoproterozoic

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