Response of river terraces to holocene climatic changes in Hexi Corridor, Gansu, China

Abstract

The Hexi Corridor is a Cenozoic foreland basin system at the northeast front of the Qinghai-Xizang(Tibet) Plateau. The Shiyang River, Heihe River, Beida River and Shule River, rising in the Qilian Mountains, developed two Holocene terraces each in the plain area of the Hexi Corridor. ¹⁴C ages of alluvial fills show that the lower terraces formed between 5.57 ka B.P. and 3.15 ka B.P., the higher terraces formed between 12 ka B.P. and 8 ka B.P., and there was downcutting period from 8 ka B.P. to 6 ka B.P.. Comparing the alluvial terraces with the Holocene climatic changes, it is concluded that the downcutting period was coincident with the stable warmer and wetter climate, and the aggradation took place when the climate was changing either from drier to wetter or from wetter to drier. It is the climatic changes that caused the variations of vegetation density, soil erosion, and river sediment yields which controlled the aggradation and degradations of the rivers.