新疆伊犁黄土研究

THE RESEARCH PROGRESS ON ILI LOESS

新疆伊犁黄土-古土壤序列记录了更新世以来中亚伊犁地区自然环境的演化和变迁。总结了伊犁黄土粒度、磁化率、碳酸盐和孢粉等各指标的环境意义及其黄土和古土壤地球化学风化特征、形成环境和空间分布的差异性。结果发现:磁化率和色度由于受到多种因素不同程度的影响,对气候的指示意义较为复杂;孢粉组合和碳酸盐均指示研究区有些古土壤形成时期相对干旱,有些黄土堆积时期相对湿润;矿物和元素组成均表明伊犁盆地黄土形成于较干冷气候条件下;粒度对研究区气候的冷暖波动具有较好的指示意义。此外,古环境研究表明伊犁盆地黄土和古土壤风化分异作用不明显,古土壤形成时期地面环流较黄土形成时强,黄土-古土壤堆积存在空间差异性。

The evolution and changes of the natural environment in Central Asia are well recorded by Ili lo ess-paleosol sequence since the Pleistocene. Over the past ten years, based on masses of meaningful exploration studies of the loess in the study area by the use of environmental magnetism, sedimentology, miner alogy, geochemistry and other research methods, significant progress has been achieved. In the paper, we summarized the environmental significance of grain size, magnetic susceptibility, carbonate content, pollen assemblage and other proxies; as well as geochemical weatherii g features, depositional environment and spatial distribution pattern of the loess and paleosol. The results show that： magnetic susceptibility and color are complex in climate interpretation due to the influence of various factors to certain degrees. How- ever, the comhination of pollen and carbonate indicates that there was relatively cold and dry during some paleosol formation periods, and relatively wet during some loess formation periods, and it was the same in the glacial stages. Mineral and element compositions indicate that the Ili loess formed in the a relatively cold and dry climatic condition; and the grain size is a good indicator of a warm and cold climate alternation in the study area. The weathering differentiation of the Ili loess and paleosol is not so obvious, the ground circulation in the paleosol formation period was stronger than that in the formation period of loess paleosol at the Zhaosu loess section. The spatial differences of the loess accumulation in Ili Basin are observed.