Rb and Sr Geochemical Characterization of the Chinese Loess Stratigraphy and Its Implications for Palaeomonsoon Climate

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 2μm, 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     

Tremendous change of the earth surface system and tectonic setting of salt-lake formation in Yuncheng Basin since 7.1 Ma

The Yuncheng salt lake has formed under the setting of stepped subsidence of fault-blocks from the north to the south in Yuncheng Basin. In the phase of red clay accumulation during 7.1-3.6 Ma, the size of palaeo-lake was larger than the present salt lake, and palaeo-monsoon had formed. At 3.6 Ma, the northern basement in the basin raised abruptly due to the radiative effect of Qinghai-Tibet Plateau uplifting, and palaeo-lake was contracting southwards. At ca. 2.6 Ma ancient river flowed into the northern part of the basin. During ca. 2.0-1.9 Ma aerolian effect strengthened and loess started to accumulate on the most part of the basin. Since ca. 1.8-1.0 Ma the subsidence of the lake fault-block has been speeding up abruptly. As under the natural hydrogradient the salt lake received enough groundwater supply, and the rate of loess accumulation in the lake area was lower than that of subsidence of the lake fault-block, the lake could be preserved and becomes the only modern lake on Chinese Loess Plateau. Four large strengthening change records of the monsoon were found in the lake sequence of 5.8-1.9 Ma B.P.     

九江—澎泽一带沙山研究存在问题探讨

依据ＴＬ和＾１４Ｃ测年数据及各项环境指标分析，对九江－红光澎泽一带沙册剖面进行了研究和对比，讨论了１４７ｋａＢ．Ｐ．至晚冰期的年代地层序列和古气候环境，同时对沙山在、古湖沼形机制进行了深入探讨。该区沙山地貌并非新的构造运动所致，属差异侵蚀作用的结果，泥炭层由风积地区沙丘间湖沼沉积形成。     

中国黄土地层Rb和Sr地球化学特征及其古季风气候意义

本文详细研究了陕西洛川黄土剖面中Rb,Sr的含量变化及其在不同粒级与不同相态中的分布特征。结果表明Rb在粘粒中含量高，基本只存在于残留态中，而Sr则主要分布于砂和粉砂粒级中，并以残留态与碳酸盐结合态为主要赋存相态，因此黄土和古土壤中Rb、Sr含量的差异应与冬季风驱动的粒度分选作用引起的物质组成变化及风驱动的风化成壤强度密切相关。Rb／Sr值变化实际上反映了东一业季风系统的两个相互消长因子－－冬季风与夏季风在轨道时间尺度上的循环交互特征。洛川剖面2.6Ma以来Sr含量总体演化趋势与北半球冰量变化模式的相似性验证了高纬度冰盖生长与东亚季风强度之间存在着耦合关系，而Rb含量与磁化率之间极佳的正相关关第为今后用Rb画评估成壤作用对磁化率的贡献成为可能。     

Palaeoenvironmental change in Java island and its surrounding areas

Palaeoenvironment in Java island and its surrounding areas since the last interglacial stage was reconstructed initially using previous studies by various researchers. The karst area in Gunung Sewu on Java island was also examined by the authors in order to reconstruct the palaeoenvironment through the process of karstification. Summarizing the evidence related to palaeoclimate in the various areas made it clear that the palaeoclimatic condition was cooler and drier at the Last Glacial Maximum 18 000 yr BP, than today. Formation of dry valleys in Gunung Sewu was conditioned by lowering of sea-level, and establishment of a cool and extremely dry climate. Subsequent to the initial reconstruction, the results of the estimated palaeoclimate at 18 000 yr BP were plotted at the respective points where the samples were obtained, and maps for northern winter and northern summer were constructed showing the estimated streamlines of monsoon circulations, polar frontal zones and intertropical convergence zones, in order to better explain the distribution of the palaeoclimate conditions of the area. ©1997 John Wiley & Sons, Ltd.     

沔阳地区一万多年来孢粉记录的环境演变

依据Ｍ１孔孢粉组合特征及＾１４Ｃ年龄数据,结合孢粉数理统计分析,重建了江汉平原沔阳地区一万多年来的古季风气候变迁序列。研究结果表明,该区气候经历了六个阶段的变化。６．７－４．４ｋａＢＰ间。为水热配置最佳时期。夏季降水显著增多;３．９－１２．７ｋａＢＰ,气温有所下降,但有效湿度很高,为古云楚泽扩张时期,其湿度的增加既受锋面降水带的影响,同时恙长江南移,河床迅速抬高有关。约６ｋａＢＰ后,人类活动在本区     

云南鹤庆古湖晚更新世的孢粉记录及其古气候学意义

本文通过鹤庆古湖沉积物的孢粉记录对该区晚更新世的古植被和古气候进行了恢复。该区末次间冰期和末次冰期内部气候波动性特点与深海氧同位素记录有着较好的可比性,反映在全球变化的背景上,气候的不稳定性同样在本区有明显的响应。而且不同季风区气候资料对比也表明,本区冷湿和暖干的气候组合具有明显的区域特征,末次冰期该区夏季锋面降水增多,而间冰期则与之相反。造成这种区域环境效应的原因,与西南季风区大气环流的复杂性、云贵高原的地貌部位以及由青藏高原地表反照率引起的热力学和动力学过程有关。