末次间冰期兰州黄土记录中的粘土矿物及其环境意义探讨

本文研究了末次间冰肮分辨率兰州黄土（Ｓ１）２１个样口的粘土矿物，并与现代尘暴沉积物作了对比。研究结果表明，Ｓ１三个古土壤导春间所夹两个黄土层中的粘土矿物组合特征基本一致，以伊利石为主，其次为绿泥石和高岭石及少量伊／蒙间层矿物。粘土矿物的形成以碎屑成因为主，其一在剖面上的变化具有批示气候变化的意义。古土壤层中伊利石结晶度较黄土层中低，反映在气候温暖潮湿的条件下粘土矿物受到了不同和蔼的改造。粘土矿物总

ORIGIN AND SIGNIFICANCE OF CLAY MINERALS IN THE LAST INTERGLACIAL LOESS IN LANZHOU AREA,NORTH CENTRAL CHINA

A newly dug 45 m deep loess well section at Gaolanshan near Lanzhou indicates that loess formed during the last interglacial (MIS 5)is 7 5 m thick and can be identified into five layers named downward S 1 1 ,S 1 2 ,S 1 3 ,S 1 4 ,and S 1 5 that are correlated with the Marine Isotope Stages (MIS) 5a ,5b,5c,5d and 5e respectively.Clay minerals in 21 samples from these loess/paleosol layers and from a recent extraordinary dustfall were deeply analysed and inter contrasted with each other.Researches show that the assemblages of clay minerals in paleosol and loess layers are nearly the same.Illite is dominant(66 5%),chloritoid,kaolinite are the second,and illite/montmorillonite is in small quantity.The clay minerals both in the loess and paleosol layers are of detritus origin.The contents of clay minerals in the different layers are different and can indicate climate changes.The crystallinity of illite in paleosols is lower than in loesses.The possible interpretation is that the illite must have been reformed at different degrees under the conditions of warm and humid climate.The MIS 5e substage was the optimum during the last interglacial period in this monsoonal area.