【摘要】 风尘堆积沉积速率的变化对揭示大气环流与古气候变化具有重要意义。基于中亚东北部天山及其周边黄土剖面已有的释光和放射性14 C年代数据的分析筛选整理,初步获得了该区深海氧同位素MIS3以来黄土沉积速率的时空变化特征,并探讨了可能的原因。结果表明:(1)末次盛冰期(LGM)沉积速率总体上表现出天山西部低、伊犁盆地高的特征。这种空间变化特征可能与地形、大气环流以及伊犁盆地黄土的近源堆积有关。(2)LGM和MIS3b时期是MIS3阶段以来主要的粉尘沉积阶段。MIS3b时期沉积速率最高,LGM次之,而全新世沉积速率较低。MIS3b时期高的沉积速率可能与大规模的冰川发育有关。在全新世期间,中全新世的沉积速率相对较高,可能与中全新世气候湿润、地表捕获粉尘的能力强有关。更多还原

【Abstract】 Eolian loess is an important archive for understanding Quaternary environmental changes.The sedimentation rate of loess,as an important proxy to environmental changes,is helpful to revealing atmospheric circulation and paleoenvironmental changes.With the application of various dating methods especially the high-accuracy Optically Stimulated Luminescence(OSL),sedimentation rate has been widely applied to the orbital-scale and millennial-scale paleoclimatic changes recently in the study of Chinese Loess Plateau(CLP).Central Asia is also one of the main distribution areas of world loess.This paper is specially devoted to the spatio-temporal distribution pattern of dust sedimentation rate of the Tianshan loess in order to provide a new horizon for understanding paleoclimatic patterns in Central Asia,where sedimentation rate has been poorly studied.Therefore,we collected the available geochronological data including OSL and 14 C of the last glacial loess sections from the Tianshan Mountains of Central Asia in this paper,analyzed the reliability of age data and discussed spatial and temporal distribution pattern of the sedimentation rate.The results suggest that:(1)During the Last Glacial Maximum(LGM),sedimentation rate is relatively low in the west of Tianshan,but high in the Ili Basin.This spatial pattern of distribution is closely related to geographic and atmospheric conditions as well as proximal accumulation.(2)LGM and MIS3 b are the main dust deposition stages since MIS3.In the Tianshan area,the sedimentation rate of MIS3 b is higher than that of LGM.Since the solar insolation in the MIS3 b stage is higher than that in the LGM stage,the westerly will bring more moisture from the Atlantic Ocean,Caspian Sea and Mediterranean Sea.In the Tianshan area,moisture is believed the main factor affecting glaciers.In this regard,the scale of glacier in the wetter MIS3 b period is larger than that in the LGM period,and the intensified abrasion of the glaciers will bring in more fine particulate matters.(3)Sedimentation rate is low in Holocene,and thevariations in sedimentation rate are similar to the‘westerly model’.We speculate that the amount of dust in the atmosphere is relatively low in Holocene.Dust is mainly deposited under wet climate since humidity is conducive to vegetation and helpful for dust to settle down.More moisture will result in higher sedimentation rate.更多还原