Dating and genesis of the upper Weihe River terraces in Longxi basin,China  

作　　者：Pan Baotian Liu Xiaofeng Gao Hongshan Wang Yong Li Jijun 

机构地区：[1]Key Laboratory of Western China＇s Environmental System, Ministry of Education, Lanzhou University, Lanzhou 730000, China

出　　处：《Progress in Natural Science:Materials International》2007年第11期1334-1340,共7页自然科学进展·国际材料（英文版）

基　　金：Supported by National Natural Science Foundation of China ( Nos 40401007,40471016 ,40421101);the National Programon Key BasicResearch Project (No 2005CB422001)

摘　　要：Seven terraces along the Weihe River in Longxi basin have been investigated. These terraces all consist of archetypal duality in structure, namely the floodplain deposits and the layer of gravels overlaid by varyiring thickness of the loess. By resorting to various dating approaches such as palaeomagnetic, optically stimulated luminescenece （OSL）, 14C and loess-paleosol sequence, we provide preliminary timing of these seven terraces along upper Weihe River. Analysis on sedimentation characteristics and datir^4g of these terraces showed that seven terraces may be jointly generated by tectonic uplifts and climatic changes. Tectonic uplifts may accommodate initial river incision, and climatic change may be responsible for processes of subsequent channel widening and aggradation. Aggradation normally occurs during glacial periods, in contrast to down-cuttings during transitions from glacial to interglacial period. Moreover, on the basis of the tim- ings and heights of these terraces, we infer that the long-term rate of river incision was determined to be 0.2 m/kyr during the last 870 kyr, which differs from other river incision rates. This discrepancy may reflect spatio-temporal differentiation of tectonic activities in the Qinling orogenic belt during the Pleistocene.Seven terraces along the Weihe River in Longxi basin have been investigated. These terraces all consist of archetypal duality in structure, namely the floodplain deposits and the layer of gravels overlaid by varying thickness of the loess. By resorting to various dating approaches such as palaeomagnetic, optically stimulated luminescenece (OSL), 14C and loess-paleosol sequence, we provide preliminary timing of these seven terraces along upper Weihe River. Analysis on sedimentation characteristics and dating of these terraces showed that seven terraces may be jointly generated by tectonic uplifts and climatic changes. Tectonic uplifts may accommodate initial river incision, and climatic change may be responsible for processes of subsequent channel widening and aggradation. Aggradation normally occurs during glacial periods, in contrast to down-cuttings during transitions from glacial to interglacial period. Moreover, on the basis of the timings and heights of these terraces, we infer that the long-term rate of river incision was determined to be 0.2 m/kyr during the last 870 kyr, which differs from other river incision rates. This discrepancy may reflect spatio-temporal differentiation of tectonic activities in the Qinling orogenic belt during the Pleistocene.

关 键 词：loess stratigraphy river terraces climate change Upper Weihe River. 

分 类 号：P461.3[天文地球—大气科学及气象学]