北京市昌平区钻孔岩芯的磁化率与粒度组份变化的相关性研究

以昌平区钻孔岩芯为例,分析沉积物粒级组分与磁化率大小变化的相关性。从厚约150 m的剖面选取590多个样品,分别测试从0.5~500 μm各个粒度区间颗粒的百分含量和磁化率。通过计算它们之间的相关关系,认为湖相沉积物磁化率的变化与0.5~30 μm间细粒物质的含量,特别是与0.5~10 μm区间悬浮物质的含量反相关,而与65~500 μm间较粗粒物质的含量正相关。这种相关性与黄土沉积刚好相反,反映了二者之间磁化率不同的变化机制, 蕴涵着一定的古气候信息。

Correlation Between the Content of Different Grain Size and Magnetic Susceptibility in Core Changping

The different grain size content range from 0.5~500 μm and magnetic susceptibility were measured to study the correlation between grain size and magnetic susceptibility,selected more 590 samples,in sediments from Core Changping.The results show that magnetic susceptibility of the profile is of some relationship with that of the content of different grain sizes,the correlation coefficient between susceptibility and the mean grain size is positive for the whole core.The magnetic minerals are mainly concentrated in fractions with coaster grains.Furthermore,the correlation between grain size and magnetic susceptibility is also affected by sediment source,the degree of sorting process and so on.The correlation coefficient of susceptibility with the content of 0.5~30 μm,especially 0.5~10 μm,is negative,and with the content of 65~500 μm is positive,dominated by large particles of magnetic minerals in the core.In addition,the correlation is different in various depth.Due to the different condition of lake and aggregation,the correlation between magnetic susceptibility and grain sizes should be analyzed depending on deferent sedimental environment.When the strong hydrodynamic,magnetic susceptibility are relatively large,and relatively weak,the magnetic susceptibility is relatively small.Therefore,the grain size and magnetic susceptibility changes to reflect the changes in hydrodynamic conditions,indicating that changes in the strength of the East Asian monsoon.Especially,the climate cycle from the Quaternary period,the to-and-fro of the glaciation and interglaciation,we concluded that data and magnetic susceptibility,particle size and get paleoclimate information of the drilling: 1100~800 ka B.P.is mainly cool and there is a small heating between them,800~600 ka B.P.cool and warm alternate in temperature,600~400 ka B.P.climate is prior to hot and humid,400~200 ka B.P.climate is prior to cold and dry,200~0 ka B.P.climate is priority to cool alternate fluctuation.Research shows that the core may reflect the 8~10 climatic cyclicities.The area of precipitation increases in humid climate period,with alluvial deposits containing more coarse particles and larger magnetic susceptibility.The fluctuations of susceptibility indicate the changes of paleoclimate.