河西走廊平原区全新世河流阶地对气候变化的响应

RESPONSE OF ALLUVIAL TERRACES TO HOLOCENE CLIMATIC CHANGES IN THE HEXI CORRIDOR BASINS, GANSU, CHINA

河西走廊的石羊河、黑河、北大河和疏勒河在平原区发育了两级阶地，根据１４Ｃ测年数据，低阶地形成于５．５７～３．１５ｋａＢ．Ｐ．，高阶地形成于１１～８ｋａＢ．Ｐ．，在８～６ｋａＢ．Ｐ．之间为河流下切期。将河流作用与古气候变化对比发现，下切期与稳定的湿热气候同期，河流加积作用发生在由干向湿或由湿向干的过渡时期。

The Shiyang River, Heihe River, Beida River and Shule River developed 2 Holocene terraces each in the plain area of the Hexi Corridor. Based on 14 C ages from the sediments on the terraces, it is discovered that the lower terraces were formed between 5.57 ka B.P. and 3.15 ka B.P., the higher terraces were formed between 11 ka B.P. and 8 ka B.P., and that there was downcutting perod of the rivers from 8 ka B.P. to 6 ka B. P. Comparing the alluvial terraces with the climatic changes in the Holocene, 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.