The Study Of High-resolution Osl Chronology On Loess Sediments On The Northeast Tibetan Plateau

As a reliable indicator and a good carrier of past climate change,loess in China systematically recorded the continuous climate change history of Asian hinterland climate change in the late Cenozoic,and has the characteristics of the glacial-interglacial period in the Northern Hemisphere.A large number of aeolian deposits are widely distributed on the Tibetan Plateau.These aeolian deposits are important carriers for the reconstruction of the past climatic environment of the Tibetan Plateau,especially the loess in the northeastern part of the plateau for understanding the interaction between Asian monsoon circulation and the westerly circulation on the Tibetan Plateau.In the northeastern part of the Tibetan Plateau,the predecessors made detailed works on the loess(Xining,Ledu,etc.)which is belong to the western part of the Loess Plateau and established a high-density chronological framework to reconstruct the past environmental changes in the area,but for the Tibetan the alpine loess in the northeastern part of the plateau,especially the loess above 3000 m,the works had been concentrated since the last deglaciation,for the elder sections are limited,lacks the aeolian sedimentary study of the last glacial or the last interglacial period,while the long-term loess deposits are of great significance for understanding the past environmental changes in the Tibetan Plateau.Therefore,it is necessary to conduct a study of loess deposits on a longer time scale.In this paper,thick aeolian loess profiles were discovered in the Gonghe Basin and the Anyemaqen Mountains area in the northeastern Tibetan Plateau by field investigation works.The sedimentary records of these sections were found to reach the last interglacial period.It provides a good carrier for understanding the past environmental evolution on the Tibetan Plateau.Through high-density OSL dating and combined with the OSL dating results of the predecessors in the northeastern part of the Tibetan Plateau,it was found that the loess in the northeastern part of the Tibetan Plateau since the last interglacial was mainly deposited during the interglacial/interstadial periods,which are belong to warm stages,and the deposition rate in these periods is relatively high,while in the cold period,it is mainly dominated by erosion,only some special topography could deposited loess and the deposition rate is low.The aeolian deposits that could be preserved in other areas were mainly aeolian sand;Compared with K-feldspar and quartz age found that when the quartz dose <120 Gy(~40 ka)the feldspar and quartz age has a good consistency,and when the quartz dose >120 Gy,quartz signal to reach saturation and could not give accurate age,more than the saturated dose of quartz age is not suitable for chronological study;Compared to the Loess Plateau,the overall trend of grain size,magnetic susceptibility and geochemical element index changes in Tibetan Plateau is not so large,it may be that the climate of the Tibetan Plateau was not particularly humid during the warm period,or it may be related to the insensitivity of these environmental indicators to environmental changes.