巴丹吉林沙漠查格勒布剖面微量元素反映的150ka BP以来的气候变化

Palaeo-Climate Change Indicated from Fluctuations of Trace Elements since 150 ka BP in Chagelebu Stratigraphical Section,Badain Jaran Desert

通过对巴丹吉林沙漠查格勒布剖面150 ka BP以来地层层位中16种微量化学元素的分析发现:化学性质相对稳定的元素P、Mn、Zr、Cr、Pb、Rb、Nb、Y和相对活泼的元素V、Sr、Ni、Cu、Zn、As均随25个风成沙丘砂与黄土、古土壤、湖相、冲坡积砂土砾石层构成的沉积旋回显示为25个含量低-高变化旋回,呈跌宕起伏且多波动的锯齿状的元素相对迁移-聚集过程线。元素在风成沙中呈现的低值,揭示了干旱寒冷气候作用下风力的侵蚀搬运与堆积作用;在砂土砾石层特别是湖相、黄土和古土壤中相对富集,则与暖湿气候背景下剖面所处的特殊洼地地貌位置有关。上述变化特征主要是巴丹吉林沙漠南缘地区150 ka BP以来的25个干寒多风-温湿或暖湿的气候波动所致,其根本原因可能与全球冰期-间冰期气候波动影响下的东亚冬夏季风的“拉锯式”摆动有关。

Chagelebulu section locates in the south-east of Badain Jaran Desert, where is the tail part of the modern summer monsoon of East-Asia, and it is regarded as a high-resolution geology-palaeoclimate record section in the non-monsoon areas in our country. There are 25 sedimentary cycles that are made up of aeolian palaeo-dune sands, loess, palaeosol, lacustrine facies and alluvial-hillslope sandy soils and gravels in this section. The paper makes some analyses on the 16 trace chemical elements, including relatively active elements （V, Sr, Ni, Cu, Zn, As） and relatively stable elements （P, Mn, Zr, Cr, Pb, Rb, Nb, Y）. The results are as follows： the content and variation of the 16 trace elements show remarkably regular changes in the pace with the 25 coarse-fine sedimentary cycles and they manifest 25 changeable cycles between peak and valley values, which compose a multi-fluctuating process line of relatively gather and migrate. The low distribution of these two types trace elements in the aeolian palaeo-dune sands and the alluvial-hillslope sandy soils and gravels represent erosion and accumulation under wind force during the cold-arid climate, whereas their assemble in the loess, fluvio-lacustrine facies and palaeosols are related to its specially low-lying landform position under the warm and humid climate background. The above trace elements change of relatively migrate and gather is the result of 25 cycles of cold-dry and warm-humid, which is probably caused by the repeatedly mutual alternate in the Badain Jaran Desert between the winter monsoon and the summer monsoon influenced by the climate vicissitudes during glacial and interglacial periods since the late Pleisto- cene.