Grain-size distribution and material source analysis of loess on the northeastern margin of the Qinghai-Tibet Plateau

Abstract: Grain-size analysis of the Minhe loess on the northern margin of the Qinghai-Tibet Plateau indicates that the grain-size distribution of the Minhe loess is obviously different from that in other areas such as Lanzhou and Luochuan and Xi'an. Its grain size is notably much higher. It seems too simple to assign the Minhe loess to the southern part of the loess belt traditionally because of ignorance of the effect of the plateau source area induced by the uplift of the Qinghai-Tibet Plateau. It is advisable to assign the Minhe loess to a transition zone between loess and sandy loess. The sandy dust produced as a result of repeated glacial ablation and abrasion of the plateau has supplied a substantial amount of coarse material for the Minhe loess. The voluminous dust produced by the Quaternary glaciation and melting of glaciers on the Qinghai-Tibet Plateau is not only the principal material source for the loess area in the interior of the plateau but also one of the principal material sources for the loess on the margins of the plateau.