Abstract:

To explore the differentiation rule of aeolian sediment characteristics in Madoi Basin of the source region of Yellow River， the sediments with different degrees of aeolian desertification， different geomorphic parts and different dynamic conditions in the Madoi Basin were sampled for particle size analysis. The results show that： （1） With the development of aeolian desertification， the mean grain size of sediments in the Madoi Basin increases， the proportion of coarse particle fraction grows， the sorting coefficient becomes better， the skewness approaches to negative skewness， the kurtosis gradually shifts to flat， and the frequency distribution curve also changes from bimodal to unimodal. （2） Sand dunes are all dominated by medium sand and fine sand fractions， with good sorting coefficient， nearly symmetric skewness and moderately sharp kurtosis. There is no obvious change rule of sediment particle size parameters in different landform parts of each dune due to the change of wind direction. The coarser particle size and better sorting of aeolian sand dune sediments compared with the active aeolian sandy land sediments may be due to the re-sorting of the sediments by the wind during the formation of the dunes. （3） Medium sand and fine sand are the main grain fractions of the river terrace profile， with medium deviation in sorting， positive deviation in skewness and sharp kurtosis. The grain size composition of the river terrace sediment is highly similar to the active aeolian sand dunes and sandy land formed by the surrounding wind-forming action， which is most likely to provide source material for the local aeolian activities.

Key words: aeolian desertification, particle size, Madoi Basin, the source region of Yellow River, Tibetan Plateau