Environmental Changes In The Qianhe River Inferred From Particle Size Analysis Since The Late Pleistocene

The loess is the dust accumulation formed by the dusty weather in the geological period.The particle size characteristic records the paleoenvironmental evolution information during the dust handling process.The Qianhe River Basin is located in the southwestern part of the Loess Plateau.It is affected by the East Asian monsoon.Since the Quaternary,the accumulation of thick loess deposits has been recorded,and the evolution of the East Asian monsoon is well recorded.Based on the analysis of the high-resolution loess climatic substitutes in the Qianhe River Basin,this paper reconstructs the climate change sequence in the Qianhe River Basin since late Pleistocene,analyzes the climatic evolution characteristics of the Qianhe River Basin since late Pleistocene,and explores the climate evolution The driving force and the interaction mechanism.The study area is located in the northwest of the Qianhe River Basin,located in the Qianhe River on the north bank of Qianhe River in Qianyang County.Based on the petrological characterization of 12.2m sediments and the data processing and analysis of granular environmental substitutes,the evolution process and characteristics of paleoclimatic environment since the last interglacial period of Luojiaoyou were established.Which provides a unique material for further discussion of the evolution of climate and environment in eastern and western China during this period.According to the analysis of the sedimentary lithology characteristics,the median particle size,the probability cumulative curve and the frequency curve of the sedimentary rocks since the late Pleistocene,the sedimentary particle size of the section is mostly clay and silt,Few,sedimentary particle sorting better reflects the depositional environment of the profile as a typical dust accumulation.S1?S1SS3?S1SL3?S1SS2?S1SL₂?S1SS1?S1SL1??L1LL₂?L1LS2?L1LL1?S0,and the depositional environment of the Luojiaguan profile is divided into five stages.And the climatic history of the Luojia Grottoes in the Qianhe River Basin has experienced the following stages: the depth of 12.2-11.8m is relatively dry and cold climate;11.8-9.5m?127Ka B.P 29 Ka B.P?is relatively warm and humid climate,The results show that there are three peaks,indicating that the climate has a regular change,which is consistent with the previous study of the late Pleistocene S1 ancient soil layer sedimentary characteristics consistent;9.5-5.9m 29.08 Ka B.P 20.47 Ka B.P)for the relative dry and cold Climate is 5.9 4?20.47 Ka B.P 16.48 Ka B.P?is relatively warm and humid climate;4 1m?16.48 Ka B.P 10.08 Ka B.P?is relatively dry and cold climate;1 0m?10.08 Ka B.P so far?is relatively warm and humid climate.In summary,since the late Pleistocene,the climate has experienced four distinct climatic and three dry and cold climatic characteristics.The sedimentary record of the last glacial period in the Luojiayuan profile is compared with the paleoclimatic environment evolution since the last interglacial period in the Luojia Grove profile is characterized by consistent with the global climatic environment.The distribution characteristics of the Loess Plateau soil in different areas of the Loess Plateau are different,and the distribution characteristics of the strata in different areas of the Loess Plateau are different,and there are significant spatial distributions.In the western part of the Loess Plateau,the deposition thickness is much larger than that in the central and eastern regions.This reflects that the deposition of the Loess Plateau is affected by the source area and the monsoon intensity.