CLAY MINERALS INDICATORS OF PALEOCLIMATE CHANGES OF CHENGDU PLAIN SINCE 4 kaBP

By the analyses of the X-ray diffraction, contents of clay minerals of the sediments from Jinsha site IT6814 of Chengdu are measured. The results show that the main types of the clay minerals are illite, chlorite, illite-montmorillonite and kaolinite. Analyses and study on these clay mineral types and contents show that Chengdu plain can be divided into five phases. Climate in Chengdu plain went from temperate-cool and a little dry to warm and moist. The temperature decreased abruptly since 2 500 aBP.And the influence of the ancient activity on the clay mineral is low. So the ingredient and content of clay mineral may be taken as the climatic indicator.