LAUSR

Abstract A flight of nine river terraces has been well developed and preserved along the course of the lower Taohe River. Based on optically stimulated luminescence (OSL), electron spin resonance (ESR), paleomagnetic and loess-paleosol stratigraphic analyses, we found that the accumulation ages of the gravel layers of terraces T9–T1 correspond to the loess layers L13, L9, L8, L6, L5, L4, L3-L2, L1-4 and L1-1, respectively. The chronologic results indicate that the formation and development of the modern river valley in this area occurred between 1.4 and 1.14 Ma. The topographic fluctuation caused by the Kunhuang Movement appears to have been the main reason for the reorganization of the river system and valley development in the area. In the context of this tectonic uplift, fluvial processes were coupled with the regional climate on a geomorphic equilibrium scale; i.e., over a glacial-interglacial cycle. That is, river aggradation appears principally to have occurred during glacial periods, while a graded state existed during interglacial periods. In addition, rapid river downcutting in response to climate change occurred during the transition periods from glacial to interglacial climates.