李家岗下蜀黄土剖面的反射光谱研究

SYSTEMATIC STUDY ON REFLECTANCE SPECTRUM OF XIASHU LOESS IN LIJIAGANG, NANJING

采用色度学方法，系统研究了下蜀黄土典型剖面的反射光谱特征。结合磁化率、微量元素Ｒｂ、Ｓｒ的含量和比值，讨论了色度参数的古气候意义，初步把下蜀黄土形成以来的古气候划分为３个波动旋回。丁蜀黄土和黄土高原色度参数的对比，揭示了长江中下游地区更强的化学风化作用和成壤强度。

This paper deals with the reflectance spectrum of Xiashu Loess. Lijiagang profile, a typical profile of Xiashu loess, has been selected to study the difference in reflectance spectrum between the loess layers and its overlaping paleosol layers. The results determined by two kinds of color differential meter show that both of the brightness and the red index can be served as a useful tool to discriminate the paleosols from the sequence. The paleoclimate revealed by color indexes in Xiashu loess has been divided into 3 main cycles based on the configuration of reflectance spectrum, which can be also confirmed by the signals of magnetic susceptibility and the contents and ratio of element Rb to Sr. Compared with the equivalents in Loess Plateau, west China. the Xiashu loess shows higher values in reflectance spectrum, which implies a relative stronger chemical weathering and pedogenesis in the lower reach area of Changjiang River.