Study On Landform Development Model At Longzhong Basin Since Late Pliocene

Landforms are results of climatic and geologic efferts. Traditional landform researches often separate these two efferts from each other. However, researches based on long-timescale river terrace sequences indicate that crust uplift rate increased at the time of harsher climate, which infers that landforms are results of coupling between climatic and geologic efferts. It is well known that there is a coupling relationship between climatic efferts and asthenosphere flowing. However, that model can't explain landform development histories in most regions. This paper introduces a model of landform development which was brought out by Westaway: coupling between climatic efferts and lower-crust flowing, and was then tested at Longzhong Basin.Using Yellow river terraces at Lanzhou region, northwestern part of Longzhong Basin, a 22km-thick flowing-lower-crust layer is given by Quantitative Simulation,which consists with geological setting of this region:situated between Sino-Korea province and Songpan-Ganzi province with thick lower crust layer.Using Weihe river terraces at Longxi and Zhongtan-Weinan regions, southeastern part of Longzhong Basin,a 11km-thick flowing-lower-crust layer is given by Simulation, which also consists with geological setting of these two regions:situated between Sino-Korea province and Yangtze province with thin lower crust layer.This study implies that landform development at Longzhong Basin since Pliocene is a result of coupling between climatic efferts and lower-crust flowing.