Global warming during the Miocene Climate Optimum(MCO,~17-14 million years ago)is associated with massive carbon emissions sourced from the flood basalt volcanism and ocean crustal production.However,the perturbation ...Global warming during the Miocene Climate Optimum(MCO,~17-14 million years ago)is associated with massive carbon emissions sourced from the flood basalt volcanism and ocean crustal production.However,the perturbation of tectonic carbon degassing on the interaction between climate change and carbon cycle remains unclear.Here,through time-evolutive phase analysis of new and published high-resolution benthic foraminiferal oxygen(δ^(18)O)and carbon(δ^(13)C)isotope records from the global ocean,we find that variations in the marine carbon cycle lead the climate-cryosphere system(δ^(13)Clead-δ^(18)O)on 405,000-year eccentricity timescales during the MCO.This is in contrast to the previously reported climate-lead-carbon(δ^(18)O-lead-δ^(13)C)scenario during most of the Oligo-Miocene(~34-6 million years ago).Further sensitivity analysis and model simulations suggest that the elevated atmospheric CO_(2) concentrations and the resulting greenhouse effect strengthened the low-latitude hydrological cycle during the MCO,accelerating the response of marine carbon cycle to eccentricity forcing.Tropical climate processes played a more important role in regulating carbon-cycle variations when Earth's climate was in a warm regime,as opposed to the dominant influence of polar ice-sheet dynamics during the PlioPleistocene(after~6 million years ago).展开更多
全球层型剖面和点(Global Stratotype Section and Point,GSSP)定义了地质时期大部分年代地层阶的底界,但无法对地层阶内部单元(单位层型)进一步划分和对比。本文对旋回地层学原理及其应用进行简要介绍,认为高分辨率旋回地层学和天文年...全球层型剖面和点(Global Stratotype Section and Point,GSSP)定义了地质时期大部分年代地层阶的底界,但无法对地层阶内部单元(单位层型)进一步划分和对比。本文对旋回地层学原理及其应用进行简要介绍,认为高分辨率旋回地层学和天文年代学识别出时间周期稳定的米兰科维奇旋回可为完整的沉积序列提供高分辨率的年代学约束,进而提出天文时间带的概念,即:将地层中受天文轨道作用力控制的沉积旋回校准至周期稳定的天文目标曲线(如偏心率、斜率、岁差)后形成的具有年代学意义、有全球对比潜力的地层时间单元。本文对天文时间带在新生代应用的经典范例进行介绍并探讨将其引入中生代和古生代的可能性。天文时间带是全球年代地层标准的有益补充,可使标准的地质年代、高分辨率综合地层及天文年代相结合。天文时间带在地质时间上既不受地层阶跨度的影响,又可为其单位层型的建立提供重要依据。展开更多
The simultaneity and the regionality of the chemo-cycles are proved by cycle-to-cycle correlation integrated with conodont biostratigraphic correlation of the upper part of the Givetian (Devonian) between Liujing and ...The simultaneity and the regionality of the chemo-cycles are proved by cycle-to-cycle correlation integrated with conodont biostratigraphic correlation of the upper part of the Givetian (Devonian) between Liujing and Dale. The study indicates that these chemo-cycles with time spans of 0.10 Ma have an internal relation with paleoclimatic changes, and it might have an origin through Milankovitch eccentricity cyclicity.展开更多
正常使用条件下，裂缝在钢筋混凝土（RC）结构中不可避免，沿海地区的 RC 结构裂缝使氯离子更容易浸入混凝土腐蚀钢筋，严重影响结构耐久性。在试验室模拟沿海地区环境，对不同宽度的初始裂缝（裂缝宽度 w 分别为0、0．07、0．1、0．14...正常使用条件下，裂缝在钢筋混凝土（RC）结构中不可避免，沿海地区的 RC 结构裂缝使氯离子更容易浸入混凝土腐蚀钢筋，严重影响结构耐久性。在试验室模拟沿海地区环境，对不同宽度的初始裂缝（裂缝宽度 w 分别为0、0．07、0．1、0．14 mm）的RC 柱试件进行100次海水干湿循环侵蚀后，测试其受拉侧保护层混凝土不同深度范围（0～10、10～20、20～30 mm）的氯离子含量，计算出表观扩散系数（Dw ），并对构件寿命进行了预测。结果表明：与无裂缝柱相比，当裂缝宽度 w ﹤0．1 mm 时，氯离子含量差别不大；当0．1 mm≤w≤0．14 mm 时，0～10 mm 深的氯离子含量略有增加，10～30 mm 深的氯离子含量明显增大，达到无裂缝柱的1．79～3．12倍。当 w ﹤0．1 mm 时，Dw 随 w 增大缓慢增长；当0．1 mm≤w≤0．14 mm 时，Dw 增长迅速，达到无裂缝柱的3～5倍。提出基于裂缝宽度 w 的修正表观扩散系数 Dw 及其计算式，计算式计算结果与试验结果吻合良好。随 w 增大，计算寿命明显缩短，当裂缝宽度 w≥0．13 mm 时，较无裂缝区缩短80％以上。展开更多
基金supported by the National Natural Science Foundation of China(42122042,42030403,and 42188102)the Fundamental Research Funds for the Central Universities(22120220531)+1 种基金the Shanghai Pilot Program for Basic Researchthe Netherlands Earth System Science Centre(024.002.001)。
文摘Global warming during the Miocene Climate Optimum(MCO,~17-14 million years ago)is associated with massive carbon emissions sourced from the flood basalt volcanism and ocean crustal production.However,the perturbation of tectonic carbon degassing on the interaction between climate change and carbon cycle remains unclear.Here,through time-evolutive phase analysis of new and published high-resolution benthic foraminiferal oxygen(δ^(18)O)and carbon(δ^(13)C)isotope records from the global ocean,we find that variations in the marine carbon cycle lead the climate-cryosphere system(δ^(13)Clead-δ^(18)O)on 405,000-year eccentricity timescales during the MCO.This is in contrast to the previously reported climate-lead-carbon(δ^(18)O-lead-δ^(13)C)scenario during most of the Oligo-Miocene(~34-6 million years ago).Further sensitivity analysis and model simulations suggest that the elevated atmospheric CO_(2) concentrations and the resulting greenhouse effect strengthened the low-latitude hydrological cycle during the MCO,accelerating the response of marine carbon cycle to eccentricity forcing.Tropical climate processes played a more important role in regulating carbon-cycle variations when Earth's climate was in a warm regime,as opposed to the dominant influence of polar ice-sheet dynamics during the PlioPleistocene(after~6 million years ago).
文摘全球层型剖面和点(Global Stratotype Section and Point,GSSP)定义了地质时期大部分年代地层阶的底界,但无法对地层阶内部单元(单位层型)进一步划分和对比。本文对旋回地层学原理及其应用进行简要介绍,认为高分辨率旋回地层学和天文年代学识别出时间周期稳定的米兰科维奇旋回可为完整的沉积序列提供高分辨率的年代学约束,进而提出天文时间带的概念,即:将地层中受天文轨道作用力控制的沉积旋回校准至周期稳定的天文目标曲线(如偏心率、斜率、岁差)后形成的具有年代学意义、有全球对比潜力的地层时间单元。本文对天文时间带在新生代应用的经典范例进行介绍并探讨将其引入中生代和古生代的可能性。天文时间带是全球年代地层标准的有益补充,可使标准的地质年代、高分辨率综合地层及天文年代相结合。天文时间带在地质时间上既不受地层阶跨度的影响,又可为其单位层型的建立提供重要依据。
文摘The simultaneity and the regionality of the chemo-cycles are proved by cycle-to-cycle correlation integrated with conodont biostratigraphic correlation of the upper part of the Givetian (Devonian) between Liujing and Dale. The study indicates that these chemo-cycles with time spans of 0.10 Ma have an internal relation with paleoclimatic changes, and it might have an origin through Milankovitch eccentricity cyclicity.
文摘正常使用条件下，裂缝在钢筋混凝土（RC）结构中不可避免，沿海地区的 RC 结构裂缝使氯离子更容易浸入混凝土腐蚀钢筋，严重影响结构耐久性。在试验室模拟沿海地区环境，对不同宽度的初始裂缝（裂缝宽度 w 分别为0、0．07、0．1、0．14 mm）的RC 柱试件进行100次海水干湿循环侵蚀后，测试其受拉侧保护层混凝土不同深度范围（0～10、10～20、20～30 mm）的氯离子含量，计算出表观扩散系数（Dw ），并对构件寿命进行了预测。结果表明：与无裂缝柱相比，当裂缝宽度 w ﹤0．1 mm 时，氯离子含量差别不大；当0．1 mm≤w≤0．14 mm 时，0～10 mm 深的氯离子含量略有增加，10～30 mm 深的氯离子含量明显增大，达到无裂缝柱的1．79～3．12倍。当 w ﹤0．1 mm 时，Dw 随 w 增大缓慢增长；当0．1 mm≤w≤0．14 mm 时，Dw 增长迅速，达到无裂缝柱的3～5倍。提出基于裂缝宽度 w 的修正表观扩散系数 Dw 及其计算式，计算式计算结果与试验结果吻合良好。随 w 增大，计算寿命明显缩短，当裂缝宽度 w≥0．13 mm 时，较无裂缝区缩短80％以上。
