灵台剖面石英颗粒表面形态初步研究及其古气候意义

Preliminary SEM Study of Quartz Surface Features from Lingtai Section and its Palaeoclimatic Significance

通过研究甘肃灵台 7.0MaB.P.以来的红黏土 黄土剖面中石英颗粒的形状和表面形态特征,并和标准现代环境中沉积物的特征相对比,得到了红黏土与其上的黄土有较为类似成因的结论.由于晚新生代青藏高原的隆升,高原不断被剥蚀,产生大量的碎屑物质.经过各种地表营力的作用,碎屑物质被带到附近的干旱盆地中,后来才由风力搬运到黄土高原沉积下来.灵台剖面的石英颗粒表面形态揭示了约 7.0MaB.P.以来 4次组合的变化,分别发生在约 4 2～5 0MaB.P.,约 3.6MaB.P.,约 2.6MaB.P.和约 0.9MaB.P.,推测可能与青藏高原约 7.0MaB.P.以来经历的阶段性隆升有关.

We studied the surface features of the quartz grains of the red clay loess deposits from Lingtai,Chinese Loess Plateau,and found that there are no significant differences between the quartz grains from the red clay and from the loess palaeosol layers.All of the samples displayed a similar assemblage of both the freshly crushed features and pits obtained from the collisions of grains during the wind transportation.We think that the red clay formation has a similar origin with the loess palaeosol deposits:the denudation of the plateau (maybe with the process of frost weathering) provides a large amount of silt material,then the northwestern winds blow them to the loess plateau hundreds kilometers away.The combination of the surface features shows that four transitions occurred during the last～7.0 Ma,～4.2～5.0 MaB.P.,～3.6 MaB.P.,～2.6MaB.P.and ～0.9 MaB.P.respectively.This may be related to the phasic uplift of the Tibetan Plateau.