摘要
在东部季风区的黄土研究中 ,磁化率是反映季风区气候变化的重要替代性指标之一 ,但关于中国西风区黄土磁化率的研究至今仍然为空白。通过对新疆典型的西风区———伊犁地区现代土壤和两个典型剖面黄土与古土壤序列磁化率研究发现 ,两个剖面黄土与古土壤磁化率特征存在差别。地处荒漠草原地带的则克台黄土剖面中马兰黄土的磁化率值略高于弱成壤层 ,末次间冰期古土壤层的上部磁化率也低于黄土 ,与东部季风区相比黄土磁化率偏高 ;而位于草原地带的库尔德能布拉克剖面黄土磁化率为低值 ,古土壤为高值 ,表现出与东部季风区类似的变化特点。两个黄土剖面所反映的磁化率的区域差异在一定程度上揭示了气候对磁化率变化的控制作用 ,但另一方面也反映了该区磁化率物理意义的复杂性。提出虽然在西风区黄土记录研究中不能简单套用东部季风区的方法 ,但磁化率和碳酸盐含量在西风区可指示湿度变化。
The magnetic susceptibility has been used as an index of summer monsoon strength which varies with orbitally forced solar radiation in the Loess Plateau. Many scientists think that the precipitation-driven pedogenesis is largely responsible for the production of ultrafine-grained magnetic minerals that strongly influence the strength of the magnetic susceptibility signal in the loess and paleosol sequence. For this reason, paleosols usually have higher magnetic susceptibility than the loess. The stronger the summer monsoon is, the higher the magnetic susceptibility is. Variations in magnetic susceptibility correlate closely with the global marine {}+{18}O record too. The Heinrich events and the interstadials happened at the North Atlantic Ocean and Greenland have left their signature in the Chinese loess records. This implies that the climate changes in the high latitude Northern Hemisphere may significantly affect the intensity of the Chinese monsoon systems and the climates of the North Atlantic and China were linked by the effect of westerly winds. However, few studies on the magnetic susceptibility of loess and paleosol have been done in the westerly region of Xinjiang. This will hinder the understanding to the global change well.;The investigation of two typical loess sections in Yili area where the westerly circulation is prevailing shows that there are some differences on magnetic susceptibility of loess and paleosol between monsoon region and westerly region and regional features as well. Zeketai section is located in the desert steppe zone where the annual precipitation is lower than 300 mm. It is different from the monsoon areas that most pedogenic layers during the Last Glaciation have relatively low magnetic susceptibility values, whereas the values of the loess layers are relatively high. On the contrary, the contents of the carbonate of the poorly developed paleosols are higher than those of the loess. The content of carbonate is negatively related to the value of magnetic susceptibility. At the upp
出处
《中国沙漠》
CSCD
北大核心
2001年第4期380-386,共7页
Journal of Desert Research
基金
国家重点基础研究发展规划项目 (G19990 435 0 2 )
国家自然科学基金项目 ( 4 96 710 0 9)资助
