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对甘肃西峰地区晚第三纪红土和第四纪风成典型黄土的化学元素、矿物组成和矿物颗粒形态特征研究揭示出 ,该区红土下部 (6 .2MaB .P .前 )是红化的土壤物质与其它物质一起经流水搬运再堆积的产物 ;中部 (6 .2～ 3.4MaB .P .)未发现再搬运的痕迹 ,是风尘堆积经风化和间歇性地下水位波动作用所形成的 ;上部 (3.4～ 2 .6MaB .P .)是典型的风尘堆积 -土壤序列。由于干旱区的存在是黄土高原风尘堆积的前提条件 ,该区大规模风尘物质的堆积起始于 6 .2MaB .P .前后 ,由此我们认为早在晚第三纪作为源区的中国西北和中亚地区干旱化发展趋势已经相当明显 ,而且这种变化特征对黄土高原沉积环境产生的影响是深远的。
The study on the chemical elements, mineral composition and mineralogical characteristics of late-Tertiary lateritic and Quaternary aeolian loess in the Xifeng area of Gansu reveals that the lower part of the laterite (6.2 Ma BP) is the red soil material and And other materials carried by the water along the flow of re-accumulation of products; the middle (6.2 ~ 3.4MaB. P.) No traces of re-transport was found, the dust accumulation of weathering and intermittent groundwater level fluctuations formed by the formation of the upper (3.4 ~ 2 .6MaB .P.) Is a typical dust accumulation - soil sequence. Since the existence of the arid zone is a prerequisite for dust accumulation in the Loess Plateau, the accumulation of large-scale dust and dust material in this area began around 6.2 MaB .P. Therefore, we think that the northwestern China The development trend of aridification in Central Asia has been quite obvious, and the impact of this change on the sedimentary environment of the Loess Plateau is far-reaching.