新疆伊犁地区典型黄土磁学特征及其环境意义初探  

MAGNETIC CHARACTERISTICS OF LOESS IN THE ILI AREA AND THEIR ENVIRONMENTAL IMPLICATION

作　　者：夏敦胜[1,2] 陈发虎[1] 马剑英[2] 金明[1] 王训明[2] 贾佳[1] 魏海涛[1] 刘现彬[1] 

机构地区：[1]兰州大学西部环境教育部重点实验室,兰州730000 [2]中国科学院寒区旱区环境与工程研究所沙漠与沙漠化实验室,兰州730000

出　　处：《第四纪研究》2010年第5期902-910,共9页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:40871090;40721061和90502008)资助

摘　　要：黄土地层记录的磁学参数受控因素复杂,全球不同地区黄土磁化率的主要受控因子存在差别。文章在伊犁地区选取两个地层磁化率与成壤作用分别存在较明显正相关和负相关的典型黄土剖面,进行了系统磁性地层学研究。结果表明伊犁地区黄土地层中磁性矿物浓度较大,磁学性质主要受呈现准单畴状态磁铁矿控制,黄土沉积物中磁性矿物主要为原生矿物,后期改造作用弱,地层的磁学特征受物源影响明显。地层的成壤强度与地层中磁性矿物浓度无明显相关关系,与磁性矿物中细粒磁性矿物的含量呈正相关关系。本研究结果暗示伊犁地区黄土沉积物的磁化率增强模式既区别于典型的西伯利亚黄土"风速说"模型,也不同于中国黄土高原"成壤说"模型;当后期改造作用弱时,地层的磁学特征主要受物源影响;随着地层成壤作用的增强,对原生磁性矿物的改造作用逐渐增强,次生磁性矿物含量逐渐增加,磁化率变化规律趋近于"成壤说"模型。There are positive correlations, negative correlations, or no correlation between magnetic susceptibility and pedogenic degree of loess in different sites around the world. This indicates that the magnetic property of loess is complicated and controlled by different mechanisms at different areas. In this study,two loess sections in the Ili area were selected and studied by using multi-environmental magnetic parameters （such as xlf, xHd%, XARM, SIRM, HIRM,SOFT. ）and grain size. One is section Kansu（KS） , where the magnetic susceptibility is higher in paleosols and lower in loess. The other one is section Axike （ AXK）, where part of paleosol has lower values of magnetic susceptibility and part of loess has higher values of magnetic susceptibility. The results show that （1）the concentration of magnetic minerals in loess of the lli area is higher than that in loess of China＇s Loess Plateau and the magnetic properties are controlled mainly by pseudo-single domain （PSD）magnetite; （2）magnetic minerals in loess are mainly primary minerals and their post-depositional alternation is weak, suggesting that the magnetic characteristics of loess were clearly affected by source materials ; and （3） there is no significant correlation between the concentration of magnetic minerals and the pedogenic intensity, but the concentration of fine-gralned magnetic minerals is positively correlated with the pedogenic degree.

关 键 词：黄土 成壤作用 环境磁学 磁化率 伊犁 

分 类 号：P534.63[天文地球—第四纪地质学] P539.3[天文地球—古生物学与地层学]