长江中游地区洪泛沉积物与正常河流沉积物磁组构特征对比研究

A COMPARATIVE STUDY OF MAGNETIC FABRIC CHARACTERS BETWEEN FLOODED SEDIMENTS AND NORMAL RIVER SEDIMENTS

在地层剖面中 ,洪泛沉积物与正常的河道沉积物的沉积学特征非常相似 ,仅靠沉积学特征很难将两者区分 .为了识别古洪灾事件 ,因而从环境磁学角度建立两种沉积物的识别标志是非常必要和有意义的 .本文通过对1998年长江洲湾溃口扇及其附近的长江现代河漫滩沉积物进行磁组构参数测量和对比分析 ,并结合长江下游河漫滩沉积物的磁组构参数特征 ,揭示出长江中游正常河流沉积物与河流溃口沉积物的磁组构参数特征具有明显的不同 ,并且它们与沉积时的沉积环境有着密切的关系 .因此 ,对长江中游地区沉积物磁组构参数的测试及磁化率各向异性量值椭球体形态的研究 。

The flooded sediments and normal river sediments have similar sedimentary features in stratigraphic profile. It is difficult to identify these two types of sediments only based on sedimentary features. In order to identify the ancient flood disaster events, it is significant to establish identification marks of sediments from the environment magnetism. We have made a systematic sampling and measuring, and compared the magnetic fabric character of Paizhouwan dam-break fan deposits with the magnetic fabric character of modern flood land deposits of the Yangtze River nearby Paizhouwan, and combined with the magnetic fabric character of flood land sediments in lower reaches of the Yangtze River. It is shown that the features of magnetic fabric of normal river sediments in middle and lower reaches of the Yangtze River are greatly different from that of dam-break fan deposits. And they are closely related with the sedimentary environment. So it is an effective method for identifying flood sediments and normal river sediments through measuring magnetic fabric parameters of sediments in the middle reaches of the Yangtze River and studying the shape of magnetic anisotropy susceptibility magnitude ellipse.