Giant Induan oolite: A case study from the Lower Triassic Daye Formation in the western Hubei Province, South China

Mingxiang, Mei; Gao, Junfeng

doi:10.1016/j.gsf.2011.11.017

Cited by 14 publications

(10 citation statements)

References 32 publications

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“…Ooids (\2 mm in diameter) and ''giant ooids'' ([2 mm in diameter; may be also termed pisoids, but pisoids commonly refer to a freshwater or terrestrial origin) are spherical, concentric, coated grains (Li et al 2010;Mei and Gao 2012) (Fig. 10).…”

Section: Comparison With Microbial Ooidsmentioning

confidence: 99%

Cambrian oncoids and other microbial-related grains on the North China Platform

Han

Zhang

Chi

et al. 2014

Carbonates Evaporites

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This study illustrates features of the Cambrian oncoids and provides a comparison with other microbialrelated carbonate grains found in the Cambrian succession of the North China epeiric platform. Based on cortex structures, four types of oncoids were distinguished: thincortex (superficial) oncoids, laminated-cortex oncoids, clotted-cortex oncoids, and full-cortex (without nucleus) oncoids. Thin-and clotted-cortex oncoids are often associated with oolites, laminated-cortex oncoids are present within oolitic-bioclastic grainstones, and full-cortex oncoids occur in bioturbated wackestones. The oncoids with nucleus-cortex structures are easily distinguished from other carbonate grains due to the lack of nucleus-cortex structures, and from microbial-related ooids which have more circular shape and more continuous cortex than oncoids. Oncoids without nucleus and with only crudely laminated cortex (i.e., full-cortex oncoids) can be differentiated from microbialite intraclasts and microbial lumps by the following evidences: (1) microbialite intraclasts, either rounded or angular, are characterized by margins that sharply truncate the included calcified microbes or carbonate grains and, in addition, intraclast-bearing conglomerates commonly show clear sedimentary structures such as cross-stratification and normal grading; (2) microbial aggregates have irregular but smooth margins, and rather chaotic inner structures.

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Section: Comparison With Microbial Ooidsmentioning

confidence: 99%

Cambrian oncoids and other microbial-related grains on the North China Platform

Han

Zhang

Chi

et al. 2014

Carbonates Evaporites

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“…In addition, the Lower Triassic margins of the Yangtze Platform and GBG commonly contain oolitic grainstone with giant ooids (up to 1 cm diameter) and composite coated grains ranging up to 6 cm across (Figure 17C). Giant ooids are especially prevalent in the southern margins of the Yangtze Platform and GBG but also have been found on the north margin of the GBG and in numerous localities along the Yangtze Platform margin (Lehrmann et al, 2012; Mei & Gao, 2012). The Lower Triassic oolitic margin facies also contains abundant sheet cracks and peculiar irregular lumps or clasts of oolite with large volumes of bladed isopachous marine cements and cement fans filling the voids of sheet cracks and between the oolite clasts (Figure 17D through F).…”

Section: Resultsmentioning

confidence: 99%

The role of carbonate factories and sea water chemistry on basin‐wide ramp to high‐relief carbonate platform evolution: Triassic, Nanpanjiang Basin, South China

Lehrmann

Stepchinski

Wolf

et al. 2021

The Depositional Record

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The end-Permian extinction and its aftermath altered carbonate factories globally for millions of years, but its impact on platform geometries remains poorly understood. Here, the evolution in architecture and composition of two exceptionally exposed platforms in the Nanpanjiang Basin are constrained and compared with geochemical proxies to evaluate controls on platform geometries. Geochemical proxies indicate elevated siliciclastic and nutrient fluxes in the basal Triassic, at the Induan-Olenekian boundary and in the uppermost Olenekian. Cerium/Ce* shifts from high Ce/Ce* values and a lack of Ce anomaly indicating anoxia during the Lower Triassic to a negative Ce anomaly indicating oxygenation in the latest Olenekian and Anisian. Uranium and Mo depletion represents widespread anoxia in the world's oceans in the Early Triassic with progressive oxygenation in the Anisian. Carbonate factories shifted from skeletal in the Late Permian to abiotic and microbial in the Early Triassic before returning to skeletal systems in the Middle Triassic, Anisian coincident with declining anoxia. Margin facies shifted to oolitic grainstone in the Early Triassic with development of giant ooids and extensive marine cements. Anisian margins, in contrast, are boundstone with a diverse skeletal component. The shift in platform architecture from ramp to steep, high-relief, flat-topped profiles is decoupled from carbonate compositions having occurred in the Olenekian prior to the onset of basin oxygenation and biotic stabilisation of the margins. A basin-wide synchronous shift from ramp to high-relief platforms points to a combination of high subsidence rate and basin starvation coupled with high rates of abiotic and microbial carbonate accumulation and marine cement stabilisation of oolitic margins as the primary causes for margin up-building. High sea water carbonate saturation resulting from a lack of skeletal sinks for precipitation, and basin anoxia promoting an expanded depth of carbonate supersaturation, probably contributed to marine

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“…syndepositionally in an unknown shallow-water depositional environment and were shed basinwards towards Hydra. The cortical thickness is larger than the size of the nucleus for the majority of the studied ooids (see d/t ratio in Table 2) reflecting the primary depositional environment for this Middle Triassic oolite in a high-energy, agitated setting (Mei and Gao, 2012). Although a non-selective microfabric partially made up of non-oolitic, micritic/microsparitic clasts and oolitic fragments (Figure 4A through C,H through O) in some of the analysed microfacies represents a before-relocation alteration outside this island, the Middle Triassic grain flow was diagenetically evolved after relocation (Richter, 1999).…”

Section: Oncoidsmentioning

confidence: 96%

“…Ooids, mainly calcareous, spherical to subspherical coated grains consisting of one to several nearly concentric cortices encrusting a nucleus, are ubiquitous features of (sub) tropical oceans throughout Earth's history (Flügel, 2004;Tucker, 2011). Although there is no commonly accepted elucidation for ooid genesis, processes such as accretion of fine particles around a nucleus while agitating on a soft substrate (Mei and Gao, 2012), abiotic precipitation from an ambient supersaturated water around a nucleus (Duguid et al, 2010) and organomineralization of a surface biofilm (Diaz et al, 2014;Li et al, 2017;Batchelor et al, 2018) have been diversely put forward. Ancient ooids are | 345 VARKOUHI And JAQUES RIBEIRO valuable palaeoenvironmental proxies for water energy, temperature, salinity, seawater geochemistry and bathymetry (after Sandberg, 1975;Plee et al, 2008).…”

Section: Introductionmentioning

confidence: 99%