干旱区生态环境知识资源中心

A well-preserved and continuous Neogene red clay deposit, the Caihonggou section, was recently discovered in the eastern Xorkol Basin, in the Altun Shan area at the northern margin of the Tibetan Plateau. We report detailed grain-size analyses for the Caihonggou red clay and also for the Shilou red clay section of the Chinese Loess Plateau in east-central China. Although the grain sizes are similar and can be modeled as two-component mixtures, the temporal variation of grain size and the proportions of grain-size components are very different between the Caihonggou and Shilou sections, indicating that their transportation and deposition processes and/or source areas were completely different. The fine component of the Caihonggou red clay was transported by high-level westerlies, whereas the coarser particles were carried by lower-level westerlies coming from the Taklimakan Desert, as indicated also by previous detrital zircon provenance analysis. A range of grain-size parameters for the Caihonggou section indicate that since about 8 Ma, and particularly between 8 and 6 Ma, the westerly winds strengthened, and the aridity of the Asian interior increased.