伊犁盆地黄土分布、年代及粉尘来源分析

Distribution,Age and Dust Sources of Loess in the Ili Basin

本文根据最新的研究资料,结合野外考察对处于西风区的伊犁黄土的分布、年代和粉尘来源进行了分析总结,并探讨了伊犁盆地黄土堆积的空间差异性。研究结果表明,伊犁黄土主要分布在山前丘陵和高阶地上,这些地貌部位堆积厚度最大,黄土沉积受地形和气候影响明显;已有的剖面年代学研究表明伊犁黄土主要形成于末次冰期,与新疆其它地区黄土开始大范围堆积的时间大体一致,但还可能有比中更新世更老的黄土存在;粒度分布和矿物表面形态特征表明伊犁黄土可能是近源物质与远源粉尘沉积作用叠加的结果,不同地区黄土在堆积过程所受到动力条件可能存在明显的差异;伊犁黄土中粘土组分可能主要来自中亚荒漠和伊犁河中、下游地区,西风带来的粉尘对伊犁盆地不同地区黄土的贡献率不同。

On the basis of previous studies and new data,the authors investigated the distribution,age and origin of the Ili loess.The conclusions are drawn as follows： the Ili loess is mainly distributed at the piedmont and high terraces.The loess sediments in the study area have been mainly deposited since the last glaciation,which is consistent with the time of loess deposition in other parts of Xinjiang Uygur Autonomous Region.However,there maybe have older loess than Middle Pleistocene.The particle size distribution and surface morphology of minerals indicate that the Ili loess may be the result of superposition of the close source material and far dust deposition,and the dynamic conditions in the process of deposition of loess in different regions in the Ili Basin may have significant differences.The grain size analysis shows that the clay components in loess in the Ili Basin may be transported from the Central Asia desert and the middle and lower reaches of the Ili River,but the dust brought by the westerlies have different contributions to the loess in the different regions of the Ili Basin.