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Sedimentary strata record in VA loess section from the southern Kazakhstan during past 25 000 a

RAN Min;YANG QI-li;HUANG Chang-qing;Key Laboratory of Western China's Environmental Systems(Ministry of Education),Lanzhou University;Cellege of Resource and Environmental Soiences,Xinjiang University;  
The loess-covered area of Central Asia is surrounded by other three loess areas,including European loess area,Siberia loess area and Chinese Loess Plateau.Therefore,the loess deposits in Central Asia is of great significance in clearifying the similarities and differences of loess deposits between Central Asia and other loess areas and in understanding the regional climate importance in terms of loess deposition and paleosol development.Climatologically,Central Asian arid zone is affected by the Asian monsoon and the westerlies,understanding the regional paleoclimate change allows us to clarify the interacting history of the Asian monsoon and the westerlies.This paper focused on a loess section(VA section)in central Asian,combined with field investigation and laboratory analysis(grain size,magnetic susceptibility,total organic matter and carbonate content),based on AMS14C dates,constructed the strata sequence in VA section during past ~25 000 a.The results indicate that the strata sequence in study area during past ~25 000 a BP can be divided into five units:① ~26000 14C a BP—~22 00014C a BP,a fluvially-altered loess deposition layer;② ~22 00014C a BP—~19 00014C a BP,a weakly-gleyed loess deposition layer;③ ~ 19 00014C a BP—~10 00014C a BP,an accretionary entisol layer;④ ~10 00014C a BP—~500014C a BP,a major loess deposition layer;⑤ past ~5 00014C a,a typical mollisol layer.Furthermore,the regional comparison of loess strata in Central Asia and Europe indicates that the VA section loess is similar to the Europe loess during the past ~ 25 00014C a BP and there is a converse phase relationship between VA loess strata and East Asian loess strata during the past ~25 00014C a BP.Based on the VA loess section,the predominant gaciation between ~25 000 and ~ 10 00014C a BP suggested that the last glacial climate in the Central Asia domain was constantly wetter than that in the East Asia domain.
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