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埃迪卡拉纪-早寒武世是地球历史上碳循环的重大波动期,但有关其成因和古环境意义仍存在很大分歧.为阐明这一问题,本文对华南晚埃迪卡拉纪-早寒武世两条剖面进行了高分辨的碳同位素研究.在浅水相区九龙湾-季家坡剖面,晚埃迪卡拉纪灯影组大部分δ13Corg值在δ29‰~δ24‰变化;而在深水相区龙鼻嘴剖面,大部分δ13Corg值在δ35‰~δ32‰.这些新的研究结果与华南埃迪卡拉纪δ早寒武世其他剖面发表的δ13Corg数据对比表明,δ13Corg在时间和空间上均存在着巨大变化,并受岩相的明显约束.在以碳酸盐岩为主的地层中,δ13Corg相对较高,通常大于δ30‰;而在黑色页岩和暗色硅质岩为主的地层中,δ13Corg相对较低,一般小于δ32‰.这种有机碳同位素组成的显著差异很难以存在巨大的溶解有机碳库(DOC)解释,我们认为不同微生物类群的贡献可能是导致这种差异的主要因素.浅水相样品中较高的δ13Corg值(>δ30‰)与显生宙同位素变化相近,可能反映了光合作用为主的同位素分馏;而深水样品较低的δ13Corg值(<δ32‰)可能反映了缺氧环境条件下化能自养或甲烷氧化微生物对有机质的重要贡献.这意味着在埃迪卡拉纪-早寒武世之交扬子地台的海洋仍处于强烈分层状态,且氧化还原界面波动频繁.
The Edicala-Precambrian is a major period of carbon cycle in the history of the earth, but there are still many differences on its causes and paleoenvironmental significance.In order to elucidate this issue, Most of the δ13Corg values of the Late Edoucallauji Formation varied from δ29 ‰ to δ24 ‰ in the Jiulongwan-Jijiapo section of the shallow-water facies. In the deep-water phase Long nose and mouth area profile, most δ13Corg value δ35 ‰ ~ δ32 ‰. δ13Corg comparison of the data with these new findings Ji Hua 南埃迪卡拉 δ early Cambrian other profiles published show, δ13Corg in time and space are present With significant variations and being significantly constrained by the lithofacies, δ13Corg is relatively high, usually greater than δ30 ‰, in carbonate-dominated strata, whereas in strata dominated by black shale and dark chert, δ13Corg relatively low, generally less than δ32 ‰. this significant difference in isotopic composition of organic carbon is difficult to huge libraries of dissolved organic carbon (DOC) explanation, we believe that the contribution of different groups of microorganisms may be the main factor leading to this difference. Shallow water looks like Δ13Corg product in higher values (> δ30 ‰) Phanerozoic similar isotopic variations may reflect isotopic fractionation based photosynthesis; whereas a lower value δ13Corg Sham samples (<δ32 ‰) may reflect a hypoxic environment Under this condition, the autotrophic or methane-oxidizing microbes could contribute significantly to the organic matter, which means that the ocean at the Yangtze River Delta during the Edith Calan-Precambrian period is still strongly stratified and the redox interface fluctuates frequently.