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

Grain-size analysis of the Minhe loess on the northern margin of the Qinghai-Tibet Plateau in-dicates that the grain-size distribution of t he 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 sim ple to as-sign the Minhe loess to the southern part of the loess belt traditio nally because of ignorance of the effect of the plateau source area induced b y 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 produc ed as a result of re-peated glacial ablation and abrasion of the plateau has supplied a substantial amount of coarse material for the Minhe loess.The vol uminous dust produced by the Quaternary glaciation and melting of glaciers on the Qinghai-Tibet Plateau is not only the principal material source for the l oess area in the interior of the plateau but alsoone of the principal materi al sources for the loess on the margins of the plateau.