A six-step sequential chemical extraction experiment has been conducted on samples of loess and paleosols from Luochuo section,each for one of folowing:(1)soluble;(2)exchangeable;(3) carbonate bounded;(4)Fe-Mn-oxide bounded;(5)the organic mater bounded;and(6)residual forms of elements.Results show that elements,such as K and Rb,are predominantly associated with the residual,whereas Ca and Sr are mainly in carbonate bounded and residual forms.As Sr is preferentialy partitioned into Ca-rich minerals such as carbonates and plagioclase,its distribution is associated with Ca in loess and paleosols.Sr is likely to be leached when carbonates are eluviated and Ca-containing silicates are decomposed during weathering and pedogenesis,while Rb tends to stay in situ.Therefore,Rb Sr ratios can be used to indicate leaching degree that loess and paleosols have undergone,reflect precipitation variations in the Loess Plateau and serve as a proxy index of the summer monsoon intensity.