关键词: 青藏高原, 第四纪, 定量地貌学, 年代标尺

Abstract: The comparative research of the river terraces along the northeastern margin of Qinghai Xizang plateau indicates that the heights and ages of terraces of different grade rivers are quite different. But there is correlation between the heights and the ages. A statistical relationship formula is proposed. The terrace ages of river and the drainage system are compared with the ages of paleosoil in the loess profile. The results indicate that the development of terrace is controlled by tectonics and climate. We can use the paleosoil ages of Lanzhou area loess profiles (one of the standard loess profiles) to establish an initial late Quaternary microgeomorphogy time scale. The vertical rising rates reflected by the terraces show that since 1.5Ma the northeastern margin of Qinghai Xizang plateau are continuelly rising with a tendency of becoming quicker. During mid Pleistocene the rise rate is about 0.1～0.25mm/a. Since late Pleistocene to Holocene, the rise rate is about 0.5～1.5mm/a. The relationship between the rise rates and ages has been changed with time.

Key words: Qinghai Xizang plateau, Quaternary, Quantitative geomorphology, Time scale