毛乌素沙地全新世地层粒度组成特征及古气候意义

分析结果显示,毛乌素沙地粒度自西北至东南逐渐变细、磁化率值逐渐变大。这一规律不仅表现在地表,而且在不同地点同一层位也有明显反映。说明了毛乌素沙地的形成过程与东亚季风联系密切。就所选剖面分析来看,本区在更新世晚期及全新世早期气候比较寒冷干燥,东亚冬季风影响较明显,此时为堆积成沙期,自北至南堆积的砂粒渐细,砂层渐薄;全新世中期气候温暖湿润,东亚夏季风影响显著,此时为较明显的成壤期,表现在自北至南普遍可见发育较好的黑垆土层,且南部的成壤作用比北部好,土壤的厚度也大;全新世晚期至今,气候向干冷的方向转化,但变化幅度远小于末次冰期

Characteristics of Grain Size Composition Holocene Deposits and Its Paleoclimatic Significance in Mu Us Sandy Land

The analytic consequences show the changing laws of grain size and regional magn etic susceptibility in Mu Us sandy land, the grain size gradually becomes smalle r, while the magnetic susceptibility becomes larger from north to sout h. This phenomenon appears not only on the surface of Mu Us, but also obviously occurs on the same layer of different places, so it shows that Mu Us sandy la nd's forming process is closely related to the East Asian monsoon. According to the analyses from selected profiles, we know that, it is cold and dry in this re gion during the later Pleistocene, and early Holocene East Asian winter monsoon' s influence is obvious, so, it is a period of sand accumulation, when the layer s become thinner gradually from north to south. During Middle Holocene, it is wa rm and humid, influenced evidently by East Asian summer monsoon, so, it is an ob vious pedogenesis, when there are generally well-developed Holecene palaeosol( S0) from north to south, and the pedogenesis in the south is better than that in the north, the soil is also thicker than that in the north. From late Holocene to present, the climate changes tend to be dry and cold, but its changing exten t is smaller than that of last glacial period.