Rb/Sr GEOCHEMISTRY OF LOESS DEPOSITS IN THE HORQIN DUNEFIELD, NORTHEASTERN CHINA, AND ITS IMPLICATIONS FOR CLIMATE CHANGE DURING LATE QUATERNARY

Abstract

The aeolian silt deposit is a good record of palaeoclimatic and paleoenvironmental changes in Late Quaternary.However,Loess deposition and Palaeoclimatic changes in the Horqin dunefield,Northeastern China,during the late Quaternary remains poorly understood.In this paper,the Rubidium(Rb) and Strontium(Sr) geochemical characteristics of the typical loess sequence in the southern margin of the Horqin dunefield are analyzed.Results show that the variation pattern of Rb-Sr in the Horqin loess are similar to those of the Chinese Loess Plateau,excepted for that the Rb content is lower and the Sr content is higher,probably resulted from the colder and drier climate in this study area,which led to very weak chemical weathering.It further indicates that the variations in Rb/Sr ratio in the Northeastern China loess sequence may represent the alternation of East Asian summer and winter monsoon climates.Based on the Rb-Sr geochemical data,it is suggested that Horqin dunefield had experienced a warmer and wetter climate in the periods of 108-144 ka 86±7 ka,and 233±21 ka,while it was very cold and dry,even worse than the desertification environment in the period of 262±32 ka.The climate changes in this study area are consistent with variations of the East Asian monsoon during Late Quaternary.It could be a footprint of the global glacial-interglacial climatic variations in northeastern China.