西伯利亚南部黄土古土壤记录的第四纪气候变化研究
杨太保
2009-01
项目
【英文摘要】Siberia loess is mostly distributed in the mid and north part of Eurasian loess zone, which is the transition and conjunction zone of the Eastern European loess, central Asian loess and Chinese loess. Because of the special location, It is significant difference with other loess area at the formation of loess, the development of palaeosols, the mechanism of paleocliamte and paleoenvironment and so on. Using high-resolution indicators of magnetic susceptibility, CaCO3, grain size, Carbon and oxygen isotopic and age model, we study three loess sections in Siberia, four loess sections in xinjiang province, three lake drill in the arid land and one loess section in the edge of the asian monsoon area. We preliminarily discuss the relationship of different indicators in different area, in different types of deposition. Furthermore, we discuss the process of paleoenvironment in different area. The mechanism of climatic record in Siberia is very similarity to that in the westerly area of Xinjiang. Magnetic susceptibility is not the optimum indicator for recording climate change, especially in millennial time scales. The mechanism of magnetic susceptibility is very complicated, and the grain size is an effect indictor of the climate change at this area. We primarily construct climate and environment change in different area and different depositional record, and analyze the controlling factors. For understanding current physical process,we also study the relationship between global warming and the variations of glaciers in westerly area and the edge of Asian monsoon area. Generally, the glaciers are retreated in the last 40 years. The rate of glacier retreat is varied in different mountain ranges, for example the rate of the glacier retreat in the eastern part is faster than that in the western part of Qilian Mountains.
【中文摘要】西伯利亚黄土分布区处于欧亚黄土草原带的中北端,是东欧黄土、中亚黄土和中国黄土几大特色黄土分布区的过渡和连接地带,由于其本身所处的特殊的地理位置,在黄土的形成、古土壤的发育、气候环境的记录机制、气候代用指标的物理机理等方面与其他黄土区有着显著的不同。通过对西伯利亚三个黄土剖面,新疆西风区四个黄土剖面及季风边缘区的一个黄土剖面,以及干旱区三个湖泊钻孔样品的高分辨率磁化率、CaCO3、粒度、碳氧同位素和年代等气候代用指标研究,对不同区域不同沉积类型的各环境代用指标的相互关系进行了初步探讨,进而探讨了各区域的环境变化过程。西伯利亚和新疆西风区在气候记录机制上有很大的相似性,磁化率不是西伯利亚黄土气候变化的最好的记录信号,特别是在千年以下尺度,其机理更为复杂。而黄土粒度指标是该区域气候环境变化较为有效的指标。项目研究出初步建立了不同区域、不同沉积类型记录的环境变化过程,并分析了其控制因素。项目还利用遥感资料和气候资料研究了西风区和季风区边缘冰川变化与全球变化的关系,以便理解现代环境过程的相互关联性。结果表明近40年来冰川总体处于退缩状态,但各山区退缩幅度有差异,如在祁连山,东段退缩幅度大于西段。