南京下蜀土的岩石磁学特征

对南京附近的下蜀土进行了岩石磁学测定，通过磁化率各向异性测量研究了它的沉积磁性组构特征，下蜀土的各异向性很不明显，各向异性废Ｐ小于水成岩的Ｐ值（＞１．０２），且与困面理度Ｆ高度相关，与磁线理度Ｌ相关不明显，这种特征与中国中部风成黄土极相似。对新生圩剖面进行的磁化率测量发现用化率曲线上有７个旋回的波峰、波谷变化，这与剖面中的古土壤－黄土系列相一致，说明下蜀土的剖面磁化率同样可以作为地层划分与对比，反映古气候冷暧变化的物理参数。对典型下蜀土样品进行的低温磁化率测量揭示出古土壤和黄土的成颗粒的构成不同，古土壤以超顺磁质为主，黄土以顺磁质为主。细小磁颗粒在古土壤中的积聚可能与古土壤的发育及古气候的暧湿程度有关。

Charactrristics of Xiashu Loess Near Nanjing on Rock Magnetism

The methods of rock magnetism have been applied to the research of Xiashu loess near Naming. The anisotropy of magnetic susceptibility (AMS) has been measured on the typical samples.The AMS of Xiashu loess is quite weak, the percent (P) of AMS of ah samples is less than that (>1. 02) of aqueous rock and has high close relationship with the foliation (F) of AMS but little distinct relationship with the lineation (L) of AMS. Such charactristics are much similar to those of aeolian loess in Central China. So the Xiashu loess should be wind born sediments as well. 7 eycles of alternation of rest and trough on the magnetic susceptibility (MS) curve of Xinshengwei section have been found, which could be correlated with the paleosol-loess sequence of the section. So the MS of section of Xiashu loess shoulld be regarded as a physical parameter for the division and correlation of strata and the relection of paleoclimatic fluctuation.The MS behavior of typical samples in low temperature has been analysed to explain the characteristics of the cystalline grains of magnetic minerals in Xiashu loess.The results show that the dominent magnetic minerals of loess samples are paramagnets and those of paleosol samples are super-paramagnets, the fine magnetic grains concentrated in paleosol may have relation with the development of the paleosol and the warm wet climates.