A detailed study of the mineral composition and microstructure of the black shales associated with OAEla(Eastern Russian Platform),OAElb(Middle Caspian),and the host rocks has been carried out using X-ray diffraction,...A detailed study of the mineral composition and microstructure of the black shales associated with OAEla(Eastern Russian Platform),OAElb(Middle Caspian),and the host rocks has been carried out using X-ray diffraction,scanning electron microscopic,and microprobe analyses.The results provide important constraints for depositional environments in the sedimentary basins.Black shales with pyrite framboids imply euxinic(sulfidic)conditions with increased organic matter preservation.Disintegrating framboids suggest partial or complete dissolution of the organic matter inside the framboids due to increasing water oxygenation.OAEla on the Eastern Russian Platform is heterogeneous as it includes thin interbeds of concretionary coccolith limestones within the interval of bituminous shales,and correlates with the Lower Aptian Rhagodiscus angustus nannofossil zone.The coccolith limestones indicate short intermittent episodes of interrupted stagnation,rapid oxygenation,and restoration of normal marine conditions.The presence of montmorillonite,albite,microcline,and diopside in the bituminous siltstones and in the host siltstones of OAEla on the Eastern Russian Platform,as well as a high content of titanium in the black siltstones correlated with OAElb in the Middle Caspian allow proposing significant input of pyroclastic material into the extant sea.展开更多
1 Introduction Rogoznica Lake is a typical example of euxinic saline lake,situated on the eastern Adriatic coast(43o32’N15o58’E).It is a karstic depression filled with seawater,
中国东部陆相渤海湾盆地东营凹陷古近系沙河街组油页岩中有机质的富集机制一直是研究热点,但关于异养生物及硫循环对有机质富集过程影响的研究较少.通过有机地球化方法对东营凹陷沙河街组第三、四段富有机质烃源岩进行精细研究,认为伴...中国东部陆相渤海湾盆地东营凹陷古近系沙河街组油页岩中有机质的富集机制一直是研究热点,但关于异养生物及硫循环对有机质富集过程影响的研究较少.通过有机地球化方法对东营凹陷沙河街组第三、四段富有机质烃源岩进行精细研究,认为伴随着明显的水体分层,藻类勃发进一步加剧了底水缺氧的条件,海水带来了丰富的硫酸盐促进了强烈的细菌硫还原(Bacterial Sulfur Reduction,BSR)作用,将这种缺氧条件进一步扩展到水柱上部形成透光层缺氧(Photic Zone Euxinia,PZE),而PZE有利于光合自养绿硫菌的剧烈活动.强烈的BSR作用及间歇性的PZE控制东营凹陷古湖盆中藻类等水生生物的组成,原核细菌及海相金藻类对有机质富集有一定贡献.通过分析海相藻类生物标志物C3024-正丙基胆甾烷和透光层缺氧生物标志物异海绵烷与有机碳丰度的关系,研究认为在相对丰富的外源硫酸盐输入、厌氧异养细菌作用、光能自养细菌作用和透光层缺氧条件下形成的硫循环,对东营古湖盆沙河街组烃源岩有机质的富集起主要控制作用.展开更多
Early oceans(>520 Ma) were characterized by widespread water-column anoxia, stratification, and limited oxidant availability, which are comparable to the chemical characteristics of modern marine sedimentary pore-w...Early oceans(>520 Ma) were characterized by widespread water-column anoxia, stratification, and limited oxidant availability, which are comparable to the chemical characteristics of modern marine sedimentary pore-waters in productive continental margins. Based on this similarity and our current understanding of the formation mechanism of early Earth ocean chemistry, we propose an idealized chemical zonation model for early oceans that includes the following redox zones(from shallow nearshore to deep offshore regions): oxic, nitrogenous(NO3?-NO2?-enriched), manganous-ferruginous(Mn2+ or Fe2+-enriched), sulfidic(H2S-enriched), methanic(CH4-enriched), and ferruginous(Fe2+-enriched). These zones were dynamically maintained by a combination of processes including surface-water oxygenation by atmospheric free oxygen, nitrate reduction beneath the chemocline, nearshore manganese-iron reduction, sulfate reduction, methanogenesis, and hydrothermal Fe2+ inputs from the deep ocean. Our modified "euxinic wedge" model expands on previous versions of this model, providing a more complete theoretical framework for the chemical zonation of early Earth oceans that helps to explain observations of unusual Mo-S-C isotope patterns. This model may provide a useful foundation for future studies of ocean chemistry evolution and elemental biogeochemical cycles in early Earth history.展开更多
Global warming,the most severe faunal mass extinction and the shift of biogeochemical cycles were observed in the ocean across the Permian-Triassic boundary about 252 million years ago,providing an analog to understan...Global warming,the most severe faunal mass extinction and the shift of biogeochemical cycles were observed in the ocean across the Permian-Triassic boundary about 252 million years ago,providing an analog to understanding the modern oceans.Along with the progressive global warming,the biogeochemical cycle was documented to show a shift from the decoupled processes of carbon,nitrogen and sulfur prior to the mass extinction to the coupled biogeochemical processes during faunal mass extinction.The coupled biogeochemical cycle was further observed to shift from the coupled C-N processes during the first episode of the faunal mass extinction to the coupled C-N-S processes during the second episode,diagnostic of the progressive development of more deteriorated marine environmental conditions and the more severe biotic crisis across the Permian-Triassic boundary.The biogeochemical cycles could thus be an indication to the progressive collapse of marine ecosystems triggered by the global warming in Earth history.In modern oceans,the coupled C-N cycle triggered by the global warming was observed in some regions.If these local C-N processes develop and expand to the global oceans,the coupled C-N-S processes might be brought into existence and the marine ecosystems are inevitable to suffer from complete collapse as observed at 252 million years ago.展开更多
基金a contribution to UNESCO-IUGS International Geoscience Programme (IGCP) Project 609 "Climate-environmental deteriorations during greenhouse phases:Causes and consequences of short-term Cretaceous sea-level changes"(SZ)
文摘A detailed study of the mineral composition and microstructure of the black shales associated with OAEla(Eastern Russian Platform),OAElb(Middle Caspian),and the host rocks has been carried out using X-ray diffraction,scanning electron microscopic,and microprobe analyses.The results provide important constraints for depositional environments in the sedimentary basins.Black shales with pyrite framboids imply euxinic(sulfidic)conditions with increased organic matter preservation.Disintegrating framboids suggest partial or complete dissolution of the organic matter inside the framboids due to increasing water oxygenation.OAEla on the Eastern Russian Platform is heterogeneous as it includes thin interbeds of concretionary coccolith limestones within the interval of bituminous shales,and correlates with the Lower Aptian Rhagodiscus angustus nannofossil zone.The coccolith limestones indicate short intermittent episodes of interrupted stagnation,rapid oxygenation,and restoration of normal marine conditions.The presence of montmorillonite,albite,microcline,and diopside in the bituminous siltstones and in the host siltstones of OAEla on the Eastern Russian Platform,as well as a high content of titanium in the black siltstones correlated with OAElb in the Middle Caspian allow proposing significant input of pyroclastic material into the extant sea.
基金financial support of the Ministry of Science, Education and Sports of the Republic of Croatia, under Projects 098-0982934-2717, 119-1191189-1228, 2750000000-3186
文摘1 Introduction Rogoznica Lake is a typical example of euxinic saline lake,situated on the eastern Adriatic coast(43o32’N15o58’E).It is a karstic depression filled with seawater,
文摘中国东部陆相渤海湾盆地东营凹陷古近系沙河街组油页岩中有机质的富集机制一直是研究热点,但关于异养生物及硫循环对有机质富集过程影响的研究较少.通过有机地球化方法对东营凹陷沙河街组第三、四段富有机质烃源岩进行精细研究,认为伴随着明显的水体分层,藻类勃发进一步加剧了底水缺氧的条件,海水带来了丰富的硫酸盐促进了强烈的细菌硫还原(Bacterial Sulfur Reduction,BSR)作用,将这种缺氧条件进一步扩展到水柱上部形成透光层缺氧(Photic Zone Euxinia,PZE),而PZE有利于光合自养绿硫菌的剧烈活动.强烈的BSR作用及间歇性的PZE控制东营凹陷古湖盆中藻类等水生生物的组成,原核细菌及海相金藻类对有机质富集有一定贡献.通过分析海相藻类生物标志物C3024-正丙基胆甾烷和透光层缺氧生物标志物异海绵烷与有机碳丰度的关系,研究认为在相对丰富的外源硫酸盐输入、厌氧异养细菌作用、光能自养细菌作用和透光层缺氧条件下形成的硫循环,对东营古湖盆沙河街组烃源岩有机质的富集起主要控制作用.
基金supported by the National Basic Research Program of China(Grant No.2013CB955704)National Natural Science Foundation of China(Grant No.41172030)support from the U.S.National Science Foundation,the NASA Exobiology Program,and the China University of Geosciences(Wuhan)(SKL-GPMR program GPMR201301,and SKL-BGEG program BGL21407)
文摘Early oceans(>520 Ma) were characterized by widespread water-column anoxia, stratification, and limited oxidant availability, which are comparable to the chemical characteristics of modern marine sedimentary pore-waters in productive continental margins. Based on this similarity and our current understanding of the formation mechanism of early Earth ocean chemistry, we propose an idealized chemical zonation model for early oceans that includes the following redox zones(from shallow nearshore to deep offshore regions): oxic, nitrogenous(NO3?-NO2?-enriched), manganous-ferruginous(Mn2+ or Fe2+-enriched), sulfidic(H2S-enriched), methanic(CH4-enriched), and ferruginous(Fe2+-enriched). These zones were dynamically maintained by a combination of processes including surface-water oxygenation by atmospheric free oxygen, nitrate reduction beneath the chemocline, nearshore manganese-iron reduction, sulfate reduction, methanogenesis, and hydrothermal Fe2+ inputs from the deep ocean. Our modified "euxinic wedge" model expands on previous versions of this model, providing a more complete theoretical framework for the chemical zonation of early Earth oceans that helps to explain observations of unusual Mo-S-C isotope patterns. This model may provide a useful foundation for future studies of ocean chemistry evolution and elemental biogeochemical cycles in early Earth history.
基金supported by the National Natural Science Foundation of China-Research Councils United Kingdom_Natural Environment Research Council Program (41661134048)the National Natural Science Foundation of China (41825019, 41821001), the National Key Research & Development Program of China (2016YFA0601100)+1 种基金111 Project of China (BP0820004) to Chao Li. Meng Chengsupport from the National Natural Science Foundation of China (41703008, 41902027)。
基金supported by the State Key R & D Project (Grant No. 2016YFA0601100)the National Natural Science Foundation of China (Grant No. 41330103)the 111 Project of China (Grant No. B08030)
文摘Global warming,the most severe faunal mass extinction and the shift of biogeochemical cycles were observed in the ocean across the Permian-Triassic boundary about 252 million years ago,providing an analog to understanding the modern oceans.Along with the progressive global warming,the biogeochemical cycle was documented to show a shift from the decoupled processes of carbon,nitrogen and sulfur prior to the mass extinction to the coupled biogeochemical processes during faunal mass extinction.The coupled biogeochemical cycle was further observed to shift from the coupled C-N processes during the first episode of the faunal mass extinction to the coupled C-N-S processes during the second episode,diagnostic of the progressive development of more deteriorated marine environmental conditions and the more severe biotic crisis across the Permian-Triassic boundary.The biogeochemical cycles could thus be an indication to the progressive collapse of marine ecosystems triggered by the global warming in Earth history.In modern oceans,the coupled C-N cycle triggered by the global warming was observed in some regions.If these local C-N processes develop and expand to the global oceans,the coupled C-N-S processes might be brought into existence and the marine ecosystems are inevitable to suffer from complete collapse as observed at 252 million years ago.