泥河湾盆地沉积物粒度组分与磁化率变化相关性研究

以泥河湾盆地郝家台剖面为例,分析沉积物粒级组分与磁化率大小变化的相关性。从厚约 12 2m的剖面选取 80 0多个样品,分别测试从 0.2～ 5 0 0 μm各个粒度区间颗粒的百分含量和质量磁化率。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 0.2～ 35 μm间细粒物质的含量,特别是与 0.2～ 7.5 μm区间悬浮物质的含量反相关,而与 35～ 5 0 0 μm间较粗粒物质的含量正相关。这种相关性与顶部的黄土堆积刚好相反,反映了二者之间磁化率不同的变化机制。据此可认为以外源碎屑输入为主的湖泊中,沉积物磁化率的变化主要受控于外源铁磁性矿物,它反映了湖水面的升降,蕴涵着一定的古气候信息。

The Correlation between the Content of the Different Grain Size and Magnetic Susceptibility in Lacustrine Sediments, Nihewan Basin

The different grain size content range from 0. 2～ 500 μ m and magnetic susceptiblity were measured to study the correlation between grain size and magnetic susceptibilty, selected more 800 samples, in Lacustrine sedi-ments from Nihewan Bain. The correlation coefficient of susceptibility with the content of 0. 2～ 35 μ m, especially 0.2～ 7.5 μ m, is positive, and with the content of 35～ 500 μ m is negative. This correlation is contrast to the loess deposits on top of profile, which shows the mechanism of magnetic response towardspaleoclimate changes in lacus-trine sediments is unlike that in loess. So, we can conclude that the susceptibility change in lake ( the sedimentsare mainly allogenic)sediments is controlled by the allogenic magnetic minerals. The fluctuations of susceptibilty indi-cate the changes of the lake level and paleoclimate.