The Chengdu Basin lies upstream of the Yangtze River,which is also the special transition between the second step and the first step of China geomorphy.The Quarternary red earth sediments are widely abundant in the basin.To obtain better understanding of palaeoclimate evolution in the area,clay mineralogy of the Shengli laterite profile in Chengdu Basin was investigated using X-ray diffraction(XRD) methods.The XRD analysis results showed that clay minerals in the red earth sediments were mainly illite, kaolinite,vermiculite,and montmorillonite,with small amounts of illite-smectite and kaolinite-montmorillonite mixed-layer clay minerals.Based on relative contents of clay minerals along the profile,palaeoclimate evolution in Chengdu Basin was divided into four stages since the middle Early Pleistocene,which experienced two warm/humid to cold/arid cycles.The CIA curve as well as change of the general trend of clay minerals reflects that the climate gradually became cold since the Quarternary time.This is consistent with the global climate change in Quarternary,especially the climate change in China.