THE RESEARCH PROGRESS ON ILI LOESS

Abstract

The evolution and changes of the natural environment in Central Asia are well recorded by Ili loess-paleosol sequence since the Pleistocene.Over the past ten years,based on masses of meaningful exploration studies of the loess in the study area by the use of environmental magnetism,sedimentology,mineralogy,geochemistry and other research methods,significant progress has been achieved.In the paper,we summarized the environmental significance of grain size,magnetic susceptibility,carbonate content,pollen assemblage and other proxies;as well as geochemical weathering features,depositional environment and spatial distribution pattern of the loess and paleosol.The results show that: magnetic susceptibility and color are complex in climate interpretation due to the influence of various factors to certain degrees.However,the combination of pollen and carbonate indicates that there was relatively cold and dry during some paleosol formation periods,and relatively wet during some loess formation periods,and it was the same in the glacial stages.Mineral and element compositions indicate that the Ili loess formed in the a relatively cold and dry climatic condition;and the grain size is a good indicator of a warm and cold climate alternation in the study area.The weathering differentiation of the Ili loess and paleosol is not so obvious,the ground circulation in the paleosol formation period was stronger than that in the formation period of loess paleosol at the Zhaosu loess section.The spatial differences of the loess accumulation in Ili Basin are observed.