Typical Loess Sedimentary Sections "Welded"and Paleoclimatic Interpretation In Northeastern China

Long-term continuous deposit and well-preserved deep loess sections are archives for reconstructing global climate changes.During the deposition process of loess,soil erosion and accumulation occur due to regional sedimentological factors（such as topography,geomorphology,internal and external geological forces,etc.）.It is difficult to preserve these long-term continuous deposits and well-preserved ideal loess sections in nature because the lithology of loess strata varies greatly in diverse geomorphic parts.Therefore,to reconstruct a long-term continuous record of the paleoclimate of a region,it is crucial to weld these similar sections at different sites or different periods of deposition.Reconstructing long-term,continuous paleoclimate records by welding loess core sections from a region would increase efficiency.Two typical loess sections in northeast China were investigated to explore the possibility of welding core sections for paleoclimate reconstruction.The characteristics of sedimentary,pedogenesis,and luminescence dating analysis were also conducted in this study.The main findings of this study include the following:（1）The DJG section is a typical eolian loess and the DJG section had undergone different pedogenic intensities and recorded multicycle variations of the paleoclimate.（2）The DJG section can be welded to the SBH section with similar geomorphic features and consistent loess deposits and genesis processes.Paleoclimate information inferred from the DJG section could impute the paleoclimate data from 71 to 14 ka that were lacking in the SBH section.（3）Significant cold events were recorded in the EM1 content variation curve of the DJG section,and the occurrence of these cold events corresponded well with the marineδ¹⁸O record.（4）By comparing magnetic susceptibility（MS）withδ¹⁸O curve（MIS 2-MIS 4）and Luochuan loess section,the paleoclimate of the study area generally consisted of three periods from 71 to 14 ka:the cold-dry periods from 29 to 14 ka,with mean average precipitation and mean average temperature of 560～470 mm and 7.8～6.5℃,respectively;the alternating cold-warm periods from 57 to 29 ka,with mean average precipitation and mean average temperature of 440～580 mm and 5.6～8.2℃,respectively;and cold-dry periods from 71 to 57 ka,with mean average precipitation and mean average temperature of 550～420 mm and 8.0～5.4℃.The results indicated that loess core section welding can be an alternative way for reconstructing continuous paleoclimate records.The main objective of this study is to reconstruct long-term continuous paleoclimate records by welding typical loess sections.Two typical loess sections in northeast China were investigated to explore the possibility of welding core sections for paleoclimate reconstruction.Sanbahuo（SBH）section was used as a core section for reconstructing paleoclimate from 1.22 Ma to 92 ka BP.Dajiugang（DJG）section that 1 km from SBH section was selected for loess section welding and reconstructing paleoclimate from 71 to 14 ka BP.