Aeolian Activity And Climatic Changes In The Mu Us Sandy Since The Last Glacial Maximum

The Mu Us Sandy is located at the northwestern margin of the East Asian monsoon.It is an agricultural-pastoral boundary in the north of China.Its southeastern margin is rich in sedimentary facies and contains abundant climate and environmental evolution information.This paper selects two stratigraphic profiles for high-density sampling and establishes their chronological frameworks.The particle size distribution,particle size composition,particle size parameters,magnetic susceptibility,oxides of chemical elements,oxide ratios of chemical elements were analyzed,and the sedimentary facies and dating data of several typical profiles were compared.The following conclusions were obtained:?1?The paleo-eolian sand deposits in the strata can be used as evidence for the aeolion activities in the geological period.Sand?>63?m particles?content can be used as an indicator of the intensity of aeolion activities to explore the process of changes in the intensity of sand-draining activity in the sand regions in the past geological period.?2?The sediments in the southeastern margin of the Mu Us Sandy are mainly composed of sand,and the sand content in the aeolian sand is the highest,followed by the weak soil and the paleosol.The magnetic susceptibility is the highest in the paleosol,followed by the silt,and the weak soil,modern soil layer and eolian sand.The sediments have the largest SiO₂ content in the chemical elements.The climate proxies of the entire profiles show some regular changes.?3?Since the last Glacial Maximum,the aeolion activity was extensive at 25.6—16.8±1.30 ka BP?Last Glacial Maximum?.And eolian sand had weakened soil formation at 16.8±1.30—11.8±0.60 ka BP?Last Deglaciation?,and aeolion activity reduced.In the Early Holocene,aeolian sand was widely accumulated in the sandy,and wind and aeolion activities were frequent.During the Middle Holocene,the sandy developed paleosol extensively,and aeolion activities were curbed.In the Late Holocene,sandstorms were frequent.?4?The climate change can also be roughly divided into five stages.During the Last Glacial Maximum,the climate was dry and cold.The temperature in the Last Deglaciation period increases and the humidity increases.In the Holocene the climate is fluctuating frequently.The overall performance is becoming warm,but there are still cold and dry climate fluctuations in the Early Holocene.In the Middle Holocene,4 to 5 layers of paleosols are generally developed.However,the paleosols are not continuously developed but interbedded with the eolian sands.In the Late Holocene,the climate gradually became arid.