位于山东半岛北部成山头附近的末次冰期地层,被称为"柳夼红层"。在野外调查的基础上,选择柳夼剖面进行工作,其末次冰期地层主要由沙丘砂与古土壤或湖积层叠覆堆积组成,地质时代为13.1―78.9 ka BP。根据铷、锶、Rb/Sr和矿物...位于山东半岛北部成山头附近的末次冰期地层,被称为"柳夼红层"。在野外调查的基础上,选择柳夼剖面进行工作,其末次冰期地层主要由沙丘砂与古土壤或湖积层叠覆堆积组成,地质时代为13.1―78.9 ka BP。根据铷、锶、Rb/Sr和矿物组成的分析结果,得出结论如下:1)不稳定矿物尤其是钾长石和斜长石等分解释放出铷、锶,释放量随着风化作用加强而增加。地球化学行为的差异使铷在风化过程中被吸附而锶淋失,导致铷的质量分数在沉积相中表现为沙丘砂<砂质古土壤<湖积层<粉砂质古土壤,锶则表现为沙丘砂>湖积层>砂质古土壤>粉砂质古土壤。2)铷、锶和Rb/Sr在层段上呈现出明显的峰谷变化,将末次冰期的气候波动特征呈现为LKS4、LKS2的寒冷期和LKS3的温暖期,LKS3又可划分为LKS3b的寒冷期和LKS3c、LKS3a的温暖期,体现了万年尺度的气候波动特征。这些暖阶段同步于中国季风区葫芦洞石笋记录的夏季风强盛期和65°N 7月份天文辐射总量的高峰,冷阶段对应于夏季风减弱期和天文辐射总量低谷,表明柳夼剖面末次冰期的气候变化是太阳辐射量和东亚夏季风格局共同影响下的结果。展开更多
本文利用碳酸盐岩风化剖面土壤中Rb/Sr值、有机碳氮的稳定同位素值（δ^（13）C_（org）和δ^（15）N_（org））并结合^（14）C定年结果,讨论了贵州黔西南喀斯特地区晚更新世以来的植被和气候变化情况。结果表明：（1）晚更新世以来,研...本文利用碳酸盐岩风化剖面土壤中Rb/Sr值、有机碳氮的稳定同位素值（δ^（13）C_（org）和δ^（15）N_（org））并结合^（14）C定年结果,讨论了贵州黔西南喀斯特地区晚更新世以来的植被和气候变化情况。结果表明：（1）晚更新世以来,研究区气候在千年尺度上经历了多个冷热、干湿循环过程,植被以C4植物为主;（2）研究区在14 750 a BP时期可能发生过较为极端的气候事件;（3）Rb/Sr值和δ^（13）C_（org）值可以用来指示古环境变化情况,高Rb/Sr值和高δ^（13）C_（org）值指示湿热气候,低Rb/Sr值和低δ^（13）C_（org）值指示干冷气候。展开更多
Based on the geochemical elements Rb and Sr in sediments with three different grain size fractions from profile H3 on the northern lacustrine bottomland 13 m above the Huangqihai Lake surface in 1986,the paper investi...Based on the geochemical elements Rb and Sr in sediments with three different grain size fractions from profile H3 on the northern lacustrine bottomland 13 m above the Huangqihai Lake surface in 1986,the paper investigates the record of palaeolake stand state, sedimentary environmental evolution,and winter monsoon change.First,these samples are separated into three different grain size fractions,i.e.,total sediments,77-20μm and〈20μm. Second,the chemical elements-Rb and Sr-of the grain size separation were tested and analyzed systematically in this paper.Then the elements compositions of these samples are measured using VP-320 mode fluorescence spectrum instrument,respectively.The magnetic susceptibility of these samples is measured using Kappabridge KLY-3 mode instrument made in Czech AGICO Company.The results showed the elements and the ratios varied regularly with the grain size.But the ratio of Rb/Sr in the sediments〈20μm correlates positively with the magnetic susceptibility of these samples.Therefore,the ratio of Rb/Sr in the fraction〈20 μm from the lake sediments reflected the strengthening of the weathering in the deposition sites.It is a good indicator of the summer monsoon-induced weathering and pedogenesis fluctuations and can be used to reconstruct the conditions of the paleoclimate and paleoenvironment.展开更多
Concentrations and distributions of Rb and Sr in loess and palaeosol samples from the Luochuan profile have been studied, in grain-size fractions and chemical forms. Results show that Rb is quite rich in the fraction ...Concentrations and distributions of Rb and Sr in loess and palaeosol samples from the Luochuan profile have been studied, in grain-size fractions and chemical forms. Results show that Rb is quite rich in the fraction of less than 2 μm, and exits only in the residual phase, while Sr is distributed in sand and silt fractions, occurring in the residual and carbonate phases. Therefore, variations of the concentrations of Rb and Sr in loess and palaeosols are closely related not only to dustfall compositions depending on winter monsoon wind strength but also to summer monsoon-induced pedogenic intensity. This indicates that variations of Rb/Sr ratio in Chinese loess sequences represent cyclic alternations of East Asian summer and winter monsoon climates on the orbital time-scale. Variations in Sr concentrations along the sequence bear a high similarity to the oxygen isotope record of the deep sea sediments over the past 2.5 Ma, whereas variations in Rb concentrations are in good agreement with the record of magnetic susceptibility determined with the duplicated samples from the same profile. This suggests that (1) the high-latitude ice volume is responsible for East Asian monsoon variations and (2) the signal of magnetic susceptibility depends dominantly on pedogenesis in Chinese loess sequences.展开更多
文摘位于山东半岛北部成山头附近的末次冰期地层,被称为"柳夼红层"。在野外调查的基础上,选择柳夼剖面进行工作,其末次冰期地层主要由沙丘砂与古土壤或湖积层叠覆堆积组成,地质时代为13.1―78.9 ka BP。根据铷、锶、Rb/Sr和矿物组成的分析结果,得出结论如下:1)不稳定矿物尤其是钾长石和斜长石等分解释放出铷、锶,释放量随着风化作用加强而增加。地球化学行为的差异使铷在风化过程中被吸附而锶淋失,导致铷的质量分数在沉积相中表现为沙丘砂<砂质古土壤<湖积层<粉砂质古土壤,锶则表现为沙丘砂>湖积层>砂质古土壤>粉砂质古土壤。2)铷、锶和Rb/Sr在层段上呈现出明显的峰谷变化,将末次冰期的气候波动特征呈现为LKS4、LKS2的寒冷期和LKS3的温暖期,LKS3又可划分为LKS3b的寒冷期和LKS3c、LKS3a的温暖期,体现了万年尺度的气候波动特征。这些暖阶段同步于中国季风区葫芦洞石笋记录的夏季风强盛期和65°N 7月份天文辐射总量的高峰,冷阶段对应于夏季风减弱期和天文辐射总量低谷,表明柳夼剖面末次冰期的气候变化是太阳辐射量和东亚夏季风格局共同影响下的结果。
文摘本文利用碳酸盐岩风化剖面土壤中Rb/Sr值、有机碳氮的稳定同位素值（δ^（13）C_（org）和δ^（15）N_（org））并结合^（14）C定年结果,讨论了贵州黔西南喀斯特地区晚更新世以来的植被和气候变化情况。结果表明：（1）晚更新世以来,研究区气候在千年尺度上经历了多个冷热、干湿循环过程,植被以C4植物为主;（2）研究区在14 750 a BP时期可能发生过较为极端的气候事件;（3）Rb/Sr值和δ^（13）C_（org）值可以用来指示古环境变化情况,高Rb/Sr值和高δ^（13）C_（org）值指示湿热气候,低Rb/Sr值和低δ^（13）C_（org）值指示干冷气候。
基金National Natural Science Foundation of China, No.40401006
文摘Based on the geochemical elements Rb and Sr in sediments with three different grain size fractions from profile H3 on the northern lacustrine bottomland 13 m above the Huangqihai Lake surface in 1986,the paper investigates the record of palaeolake stand state, sedimentary environmental evolution,and winter monsoon change.First,these samples are separated into three different grain size fractions,i.e.,total sediments,77-20μm and〈20μm. Second,the chemical elements-Rb and Sr-of the grain size separation were tested and analyzed systematically in this paper.Then the elements compositions of these samples are measured using VP-320 mode fluorescence spectrum instrument,respectively.The magnetic susceptibility of these samples is measured using Kappabridge KLY-3 mode instrument made in Czech AGICO Company.The results showed the elements and the ratios varied regularly with the grain size.But the ratio of Rb/Sr in the sediments〈20μm correlates positively with the magnetic susceptibility of these samples.Therefore,the ratio of Rb/Sr in the fraction〈20 μm from the lake sediments reflected the strengthening of the weathering in the deposition sites.It is a good indicator of the summer monsoon-induced weathering and pedogenesis fluctuations and can be used to reconstruct the conditions of the paleoclimate and paleoenvironment.
基金This study was financially supported by the National Natural Science Foundation of China(Grant 49725307)the Doctoral Foundation of the Ministry of Educationof China.
文摘Concentrations and distributions of Rb and Sr in loess and palaeosol samples from the Luochuan profile have been studied, in grain-size fractions and chemical forms. Results show that Rb is quite rich in the fraction of less than 2 μm, and exits only in the residual phase, while Sr is distributed in sand and silt fractions, occurring in the residual and carbonate phases. Therefore, variations of the concentrations of Rb and Sr in loess and palaeosols are closely related not only to dustfall compositions depending on winter monsoon wind strength but also to summer monsoon-induced pedogenic intensity. This indicates that variations of Rb/Sr ratio in Chinese loess sequences represent cyclic alternations of East Asian summer and winter monsoon climates on the orbital time-scale. Variations in Sr concentrations along the sequence bear a high similarity to the oxygen isotope record of the deep sea sediments over the past 2.5 Ma, whereas variations in Rb concentrations are in good agreement with the record of magnetic susceptibility determined with the duplicated samples from the same profile. This suggests that (1) the high-latitude ice volume is responsible for East Asian monsoon variations and (2) the signal of magnetic susceptibility depends dominantly on pedogenesis in Chinese loess sequences.
