The trace element and rare earth element(REE) variations across the Ordovician-Silurian succession are presented from two outcrop sections on the Yangtze Platform:the Nanbazi section,Guizhou Province,deposited in a sh...The trace element and rare earth element(REE) variations across the Ordovician-Silurian succession are presented from two outcrop sections on the Yangtze Platform:the Nanbazi section,Guizhou Province,deposited in a shallow platform interior setting,and the Wangjiawan section,Hubei Province,deposited in a deeper basinal environment.Geochemical analysis of closely spaced samples through three intervals,the Wufeng,Guanyinqiao and Longmaxi,revealed vast palaeoceanographic changes.Some geochemical proxies,including Th/U,Ni/Co,V/Cr,and V/(V+Ni) ratios,together with sedimentary facies and biotic data,indicate that an anoxic condition on the most of the Yangtze Platform during the Wufeng and Longmaxi intervals,but an oxic condition during the Guanyinqiao time.The shift of the anoxic to the oxic environment during the Guanyinqiao time coincided with a global sea-level lowstand,in parallel with the global glaciation.The Longmaxian anoxic environment was a result of a global sea-level rise,which may be synchronized with a mainly catastrophic event in the latest Ordovician.Although the two sections generally show similar variation patterns of trace and REE concentrations and some element ratios,a minor difference occurs between the Wangjiawan and Nanbazi sections,likely reflecting a difference in depositional setting during the accumulation.Such an oceanic oxygen-level variation may add a useful constraint to the current arguments on the cause and consequence of the latest Ordovician mass extinction.展开更多
Paleo-sedimentary environment of Chang 7 Member of Upper Triassic Yanchang Formation in Ordos Basin, including the paleoclimate, paleo-salinity and paleo-redox conditions were restored through geochemical elements ana...Paleo-sedimentary environment of Chang 7 Member of Upper Triassic Yanchang Formation in Ordos Basin, including the paleoclimate, paleo-salinity and paleo-redox conditions were restored through geochemical elements analysis of 289 samples collected from the outcrop sections around and wells drilled in the basin and using a series of identification indexes of paleo-climate, paleo-salinity and paleo-redox conditions, such as CaO/MgO?Al2 O3, Sr/Cu, Rb/Sr, Rb/K2 O, Th/U, V/(V+Ni), the content of element B tested from the mudstone. Comprehensive analysis shows that in sedimentary period of the Chang 7, the paleo-climate was warm temperate to subtropical climate with temperature higher than 15 ?C, the water body was continental brackish water to freshwater, and the sediments were deposited under strong reduction conditions. Suitable temperature, extensively deep lake basin and strongly reductive paleo-sedimentary environment led to the blooming, enrichment and preservation of organic matter in the submember Chang 73. As a result, a set of high-quality source rock was formed, laying material foundation for large-scale accumulation of shale oil.展开更多
This paper investigates the high-solution of Mo isotopes and uses trace-element analyses for fresh and representative black shales and siliceous shales collected from the transition between the Late Ordovician and the...This paper investigates the high-solution of Mo isotopes and uses trace-element analyses for fresh and representative black shales and siliceous shales collected from the transition between the Late Ordovician and the Early Silurian at the Wangjiawan section in Yichang and the Late Permian Dalong Formation in the Shangsi Section of Sichuan. The applicability of different geochemical parameters used as paleo-oxygenation indices are also compared. The preliminary results show that V/（V＋Ni）, Uauth （auth U）, V/Cr, Ceanom and U/Th have a scattered variation range, but most samples plot within the suboxic-anoxic fields. The suboxic-anoxic environment was dominant during the deposition and formation of the two anoxic facies. These redox indicators show little correspondence to the δ98M0 values. The U/Mo ratio can be used as a potential proxy for the paleo-redox conditions due to the possibility that Mo is enriched relative to U at different redox gradients during early diagenesis. This evidence is more significant for the euxinicity condition and corresponds to positive δ98M0 （〉1.5%o） values with low U/Mo ratios. This evidence is likely related to the depositional conditions near the boundary between anoxic and euxinic environ- ments, which are characterised by low bioturbation or water circulation. Other samples reveal a wide scatter of U/Mo ratios and δ98M0 〈1.5%0. These results are likely due to punctuated improvements in oxygenation with intense bioturbation or water circulation, which led to the redistribution of trace element.展开更多
Climatic and environmental conditions play a pivotal role in the evolution of the biosphere,serving as the primary natural factors influencing biological evolution and the development of human civilization.The study o...Climatic and environmental conditions play a pivotal role in the evolution of the biosphere,serving as the primary natural factors influencing biological evolution and the development of human civilization.The study of the evolution of Earth's habitability primarily revolves around the reconstruction of climatic and oceanic conditions in geohistorical periods,shedding light on their dynamic changes.This paper collates classic geological indicators and geochemical proxies associated with paleoclimatic and oceanic environmental conditions.The latest“big data”analyses and simulations made possible by the availability of previously unimagined massive datasets reveal several key findings:During the early Paleozoic,atmospheric oxygen levels were low,and widespread oceanic anoxia was prevalent;the Devonian era witnessed a greenhouse climate,followed by the Carboniferous ice age characterized by higher oceanic oxidation levels and alkalinity.The latest Paleozoic deglaciation occurred under high pCO_(2) conditions,extending into much of the Mesozoic and early Cenozoic,marked by multiple hyperthermal and anoxia expansion events,until the resurgence of global glaciation in the middle-late stages of the Cenozoic,ultimately bringing environmental and climatic conditions closer to modern levels.By correlating the aforementioned long-term trends with major geological events,we can delineate the co-evolution of paleoclimate and oceanic environments in tandem with the development of Tethys tectonics as follows.(1)During the Proto-Tethys stage,global paleo-elevations were relatively low,and atmospheric oxygen levels were also relatively modest.Despite the occurrence of significant tectonic movements that led to noticeable transgressive-regressive cycles,their effects on climate and oceanic environments were somewhat limited due to the relatively weak interactions.(2)The emergence of the Paleo-Tethys was a significant event that coincided with the formation of the supercontinent Pangaea.Intensive orogenic movements during this 展开更多
该研究以显生宙碳循环异常环境的地球生物学过程为研究主体,重点研究二叠纪-三叠纪之交和晚泥盆世两大重大地质突变期的地球生物学过程特点和规律,查明碳循环异常的起因及其对生态系统的影响,探索生物与环境的相互作用。二叠纪—三叠纪...该研究以显生宙碳循环异常环境的地球生物学过程为研究主体,重点研究二叠纪-三叠纪之交和晚泥盆世两大重大地质突变期的地球生物学过程特点和规律,查明碳循环异常的起因及其对生态系统的影响,探索生物与环境的相互作用。二叠纪—三叠纪之交是古生代海洋生态系破坏和中生代型海洋生态系开始重建的转折点,古海洋缺氧对该转折影响深远。通过对华南多条剖面高精度碳同位素、碳-硫形态、碳酸盐晶格硫(CAS)、DOP和Δδ13C等分析测试,该年度研究在认识该时期古海洋缺氧的时限、程度、演化和成因机制等方面取得明显进展。大灭绝前的二叠纪浅水碳酸盐岩台地以氧化环境为主。由于火山活动释放大量的CO2、SO2等气体,导致气温上升、陆地生态系统开始瓦解、陆源输入增加、海洋贫氧层(OMZ)扩张,大灭绝后海洋环境向缺氧环境转变。早三叠世早期δ34SCAS明显比晚二叠世偏重,波动剧烈,且与δ13Ccarb明显正相关(3次同步正漂),意味着严重的海洋缺氧、硫化事件,海水硫酸盐浓度很低(<3 m M)。早三叠世早期δ13Ccarb频繁和幅度较大的波动,指示了动荡不稳定的海洋碳循环;之后δ13Ccarb和δ34SCAS变化率同步减小,两者呈现负相关关系,可能是由于海水温度下降、海水循环增强,海洋碳循环趋于稳定。中三叠世δ34SCAS下降,变化率进一步降低,碳-硫同位素的正相关关系逐渐消失,反映该时期海洋硫酸盐浓度进一步升高,以正常的氧化状态为主。大灭绝后动荡的海洋碳-硫循环及缺氧环境导致了生物复苏迟缓。晚泥盆世弗拉斯-法门(F-F)生物大灭绝事件是显生宙又一重大地质转折时期,集中体现在生物礁生态系中,菌藻类取代后生动物(珊瑚-层孔虫)造礁。对华南地区多个剖面细致的观察和统计分析表明,菌藻类可侵入"活着"的后生动物并抑制后生动物的发育。后生动物骨�展开更多
基金Supported by National Basic Research Program of China (Grant No.2005CB422101)
文摘The trace element and rare earth element(REE) variations across the Ordovician-Silurian succession are presented from two outcrop sections on the Yangtze Platform:the Nanbazi section,Guizhou Province,deposited in a shallow platform interior setting,and the Wangjiawan section,Hubei Province,deposited in a deeper basinal environment.Geochemical analysis of closely spaced samples through three intervals,the Wufeng,Guanyinqiao and Longmaxi,revealed vast palaeoceanographic changes.Some geochemical proxies,including Th/U,Ni/Co,V/Cr,and V/(V+Ni) ratios,together with sedimentary facies and biotic data,indicate that an anoxic condition on the most of the Yangtze Platform during the Wufeng and Longmaxi intervals,but an oxic condition during the Guanyinqiao time.The shift of the anoxic to the oxic environment during the Guanyinqiao time coincided with a global sea-level lowstand,in parallel with the global glaciation.The Longmaxian anoxic environment was a result of a global sea-level rise,which may be synchronized with a mainly catastrophic event in the latest Ordovician.Although the two sections generally show similar variation patterns of trace and REE concentrations and some element ratios,a minor difference occurs between the Wangjiawan and Nanbazi sections,likely reflecting a difference in depositional setting during the accumulation.Such an oceanic oxygen-level variation may add a useful constraint to the current arguments on the cause and consequence of the latest Ordovician mass extinction.
基金Supported by the National Key Basic Research and Development Program(973 Project)National Science and Technology Major Project(2016ZX05050,2017ZX05001002)
文摘Paleo-sedimentary environment of Chang 7 Member of Upper Triassic Yanchang Formation in Ordos Basin, including the paleoclimate, paleo-salinity and paleo-redox conditions were restored through geochemical elements analysis of 289 samples collected from the outcrop sections around and wells drilled in the basin and using a series of identification indexes of paleo-climate, paleo-salinity and paleo-redox conditions, such as CaO/MgO?Al2 O3, Sr/Cu, Rb/Sr, Rb/K2 O, Th/U, V/(V+Ni), the content of element B tested from the mudstone. Comprehensive analysis shows that in sedimentary period of the Chang 7, the paleo-climate was warm temperate to subtropical climate with temperature higher than 15 ?C, the water body was continental brackish water to freshwater, and the sediments were deposited under strong reduction conditions. Suitable temperature, extensively deep lake basin and strongly reductive paleo-sedimentary environment led to the blooming, enrichment and preservation of organic matter in the submember Chang 73. As a result, a set of high-quality source rock was formed, laying material foundation for large-scale accumulation of shale oil.
基金supported by National Natural Science Foundation of China (Grant Nos. 40673020, 40839903, 40821061)Ministry of Education of China (Grant Nos. IRT0441 and B07039)+2 种基金China Petroleum & Chemical Corporation Project (Grant No. G0800-06-ZS-319)MOST Special Fund from the State Key Laboratory of Geological ProcessesMineral Resources and the Fundamental Research Funds for the Central Universities
文摘This paper investigates the high-solution of Mo isotopes and uses trace-element analyses for fresh and representative black shales and siliceous shales collected from the transition between the Late Ordovician and the Early Silurian at the Wangjiawan section in Yichang and the Late Permian Dalong Formation in the Shangsi Section of Sichuan. The applicability of different geochemical parameters used as paleo-oxygenation indices are also compared. The preliminary results show that V/（V＋Ni）, Uauth （auth U）, V/Cr, Ceanom and U/Th have a scattered variation range, but most samples plot within the suboxic-anoxic fields. The suboxic-anoxic environment was dominant during the deposition and formation of the two anoxic facies. These redox indicators show little correspondence to the δ98M0 values. The U/Mo ratio can be used as a potential proxy for the paleo-redox conditions due to the possibility that Mo is enriched relative to U at different redox gradients during early diagenesis. This evidence is more significant for the euxinicity condition and corresponds to positive δ98M0 （〉1.5%o） values with low U/Mo ratios. This evidence is likely related to the depositional conditions near the boundary between anoxic and euxinic environ- ments, which are characterised by low bioturbation or water circulation. Other samples reveal a wide scatter of U/Mo ratios and δ98M0 〈1.5%0. These results are likely due to punctuated improvements in oxygenation with intense bioturbation or water circulation, which led to the redistribution of trace element.
基金supported by the National Natural Science Foundation of China (Grant Nos.92155201,42272361)China Geological Survey (The Establishment of Chinese Stratigraphic Standards Project)。
文摘Climatic and environmental conditions play a pivotal role in the evolution of the biosphere,serving as the primary natural factors influencing biological evolution and the development of human civilization.The study of the evolution of Earth's habitability primarily revolves around the reconstruction of climatic and oceanic conditions in geohistorical periods,shedding light on their dynamic changes.This paper collates classic geological indicators and geochemical proxies associated with paleoclimatic and oceanic environmental conditions.The latest“big data”analyses and simulations made possible by the availability of previously unimagined massive datasets reveal several key findings:During the early Paleozoic,atmospheric oxygen levels were low,and widespread oceanic anoxia was prevalent;the Devonian era witnessed a greenhouse climate,followed by the Carboniferous ice age characterized by higher oceanic oxidation levels and alkalinity.The latest Paleozoic deglaciation occurred under high pCO_(2) conditions,extending into much of the Mesozoic and early Cenozoic,marked by multiple hyperthermal and anoxia expansion events,until the resurgence of global glaciation in the middle-late stages of the Cenozoic,ultimately bringing environmental and climatic conditions closer to modern levels.By correlating the aforementioned long-term trends with major geological events,we can delineate the co-evolution of paleoclimate and oceanic environments in tandem with the development of Tethys tectonics as follows.(1)During the Proto-Tethys stage,global paleo-elevations were relatively low,and atmospheric oxygen levels were also relatively modest.Despite the occurrence of significant tectonic movements that led to noticeable transgressive-regressive cycles,their effects on climate and oceanic environments were somewhat limited due to the relatively weak interactions.(2)The emergence of the Paleo-Tethys was a significant event that coincided with the formation of the supercontinent Pangaea.Intensive orogenic movements during this
文摘该研究以显生宙碳循环异常环境的地球生物学过程为研究主体,重点研究二叠纪-三叠纪之交和晚泥盆世两大重大地质突变期的地球生物学过程特点和规律,查明碳循环异常的起因及其对生态系统的影响,探索生物与环境的相互作用。二叠纪—三叠纪之交是古生代海洋生态系破坏和中生代型海洋生态系开始重建的转折点,古海洋缺氧对该转折影响深远。通过对华南多条剖面高精度碳同位素、碳-硫形态、碳酸盐晶格硫(CAS)、DOP和Δδ13C等分析测试,该年度研究在认识该时期古海洋缺氧的时限、程度、演化和成因机制等方面取得明显进展。大灭绝前的二叠纪浅水碳酸盐岩台地以氧化环境为主。由于火山活动释放大量的CO2、SO2等气体,导致气温上升、陆地生态系统开始瓦解、陆源输入增加、海洋贫氧层(OMZ)扩张,大灭绝后海洋环境向缺氧环境转变。早三叠世早期δ34SCAS明显比晚二叠世偏重,波动剧烈,且与δ13Ccarb明显正相关(3次同步正漂),意味着严重的海洋缺氧、硫化事件,海水硫酸盐浓度很低(<3 m M)。早三叠世早期δ13Ccarb频繁和幅度较大的波动,指示了动荡不稳定的海洋碳循环;之后δ13Ccarb和δ34SCAS变化率同步减小,两者呈现负相关关系,可能是由于海水温度下降、海水循环增强,海洋碳循环趋于稳定。中三叠世δ34SCAS下降,变化率进一步降低,碳-硫同位素的正相关关系逐渐消失,反映该时期海洋硫酸盐浓度进一步升高,以正常的氧化状态为主。大灭绝后动荡的海洋碳-硫循环及缺氧环境导致了生物复苏迟缓。晚泥盆世弗拉斯-法门(F-F)生物大灭绝事件是显生宙又一重大地质转折时期,集中体现在生物礁生态系中,菌藻类取代后生动物(珊瑚-层孔虫)造礁。对华南地区多个剖面细致的观察和统计分析表明,菌藻类可侵入"活着"的后生动物并抑制后生动物的发育。后生动物骨�
