Isotopic Tracing On The Source Of Loess In East China

The 234U/238U ratio of the fine-grained material records the length of time since its crushing and separation,and has great potential for tracking the surface process of matter.In this study,the age of uranium isotopes is applied to representative loess accumulation in eastern China.Loess accumulation is widely distributed in the eastern part of China.During the trace process of studying the source area,people can better understand the ancient environment signs at different levels.There are some analysis results of the loess material sources in eastern China,which can be summarized as two types.The first one is to determine that the eastern loess of China originates from the sediments of the nearby rivers and sediments of the continental shelf,which is near-source;another view is that The loess in eastern China is mainly from arid regions in the north,similar to the loess in the Loess Plateau of China.In view of the problem of loess source in eastern China,the uranium isotope crushing chronology method was used in this study.Combined with the traditional Nd-Sr isotope source tracing method,the loess,the Yangtze River sediments,the Yellow River sediments,and the Loess Plateau loess in East China were tested.The Sr-Nd-U isotope characteristics of the fine-grained components of the potential source material zone in the north,some preliminary understanding of the provenance of loess in eastern China,and the paleo-sedimentary environment of the loess in eastern China were analyzed.The initial 234U/238U ratio of loess in eastern China is lower than that in the Loess Plateau,indicating that the loess source in the Loess Plateau is not the same.Combined with Nd-Sr isotope evidence,this study found that loess source in eastern China has strong regional characteristics and is near-sourced.There is a close relationship between the source of the Shandong Peninsula and its coastal loess and Yellow River sediments on the outcropping shelf in the Huangpan Plain and the ice age.On the Yellow River coast,the basic source of the loess is the nearby Yellow River floodplain.In the earlier period,the sediments of the Yangtze River may be the main source area of Xiashu loess.The formation of loess in eastern China may be related to the local desertification formed by the relative decrease of global precipitation in the late Quaternary period and is the product of near-source sedimentation.Large areas of floodplain and continental sediments are exposed,providing plenty of silt particles for loess accumulation and becoming a potential source area under the influence of winter monsoon erosion,eventually forming a loess accumulation sequence in eastern China.