| 扬子地台新元古代碳酸盐盖帽碳、氧同位素研究 |
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| 关键词:cap carbonates negative excursions of δ13C destabilization of gas hydrate overturn |
| 基金项目:国家自然科学基金重点项目（编号：40232020）和面上项目（编号：40073007）资助 |
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| Carbon and Oxygen Isotopic Variations of Neproterozoic Cap Carbonates in Yangtze Platform |
| The end of the Earth's severe glaciations that occurred in late Neoproterozoic about 635 millions years ago is characterized by thin and laterally continuous cap carbonates associated with some lf the largest known negative anomalies of δ13C. To account for these strange geological phenomena, various models have been proposed, such as the shutdown of ecosystem productivity,the overturn of a stagnant glacial ocean, and the destabilization of permafrost gas hydrate. The author's study indicates that the negative excursions of carbon isotoic compositions of Neproterozoic cap carbonates in southern Guizhou and western Zhejiang resulted from the combined action of destabilization of gas hydrate and overturning of sea water. Two pieces of evidence support this opinion: ① The lithologic structures of cap carbonates in Douding profile and Weng'an profile in Guizhou are similar to those precipitated in moderm or ancient seeps. ② The appearance of phosphorous deposits that overlie the cap carbonates in some shallow water areas supports the "oceanic overturn"hypothesis in that the resources of phosphorites were brought from the deep ocean in the process of overturm at the end of Marinoan glaciations. Another result of overturn was the transport of δ13C depleted carbonate to the shallow water area. The negative excursion ofδ13 Cin cap carbonates and the overlying phosphorites can confirm this opinion. |
| NIE Wenming.2005.Carbon and Oxygen Isotopic Variations of Neproterozoic Cap Carbonates in Yangtze Platform[J].Acta Geoscientica Sinica,26(z1):202. |
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