The Evolution And Tectonic Meaning Of Yellow River Terraces From Gonghe To Guide

The research area is located in the northeast of Qinghai province,the upstream of Yellow River,and belongs to an important unit in the northeast of Tibetan Plateau,the tectonic evolution history has always been a frontier issue in the field of geoscience.Since the late Cenozoic tectonic uplift,the Yellow River valley in the the research area has been incised,and caused the typical river terraces landscape zone.Thus,this article recovered the tectonic uplift history of the northeastern margin of Tibetan Plateau since the late Cenozoic by researching the development status of Yellow River terraces(the nature of the river terraces,altitude,tug-of-war,sedimentary characteristics)and the age,and discussed the constraints for the uplift mode,time and spatial scalability of the qinghai-tibet plateau.The main results are summarized as follows:1)The Yellow River terraces developed very well in Gonghe basin and Guide basin,among them,Gonghe basin located upstream developed as many as 20 levels of Yellow River terrace,totally tug-of-war up to 647m,nevertheless Guide basin located downstream widely developed T1-T6.2)Gonghe-Guide Yellow River terraces was developed under the combination of tectonic uplift and climate change.Among them,T19,T18,T16,T14,T13,T6,T5,T3 terraces formed in a warm,humid climate with large river flow and river erosion is relatively strong,terrace formation mainly influenced by climate.T20,T17,T15,T11,T9,T8,T7,T4 terraces formed in a cold,dry climate with small river flow and edimentation was strong with relatively weak erosion,terrace formation mainly influenced by tectonic uplift.T12 terraces formed in a transition from warm,moist to cold and dry in which river flow was decreased significantly,and the erosion of river was also decreased significantly.terraces formation was mainly influenced by the climate in the early,and the latter was mainly controlled by tectonic motion.3)The incision rate of Gonghe-Guide Yellow River terraces In each stage indicated the uplift process of the northeast margin of the Tibetan Plateau:The average uplift rate of northeast margin of the Tibetan Plateau was 0.26 mm/a since 2.47Ma;2.47?1.71 Ma,the average uplift rate was 0.51 mm/a;1.71?0.41 Ma,the tectonic uplift motion being slower,uplift rate down to 0.09mm/a;and then the uplift rate began to accelerate to 0.35mm/a after 0.41Ma.The Yellow River terrace history of Gonghe-Guide indicated the uplift amount of the northeast margin of the Tibetan Plateau is 647m and the average uplift rate was 0.26 mm/a.The result is consistent with the previous research that the uplift pattern of the Tibetan plateau was multistage growth and denudation.The result also support the view that the Tibetan plateau extends from the middle to the north and south.It is believed that the central plateau(Lhasa and south qiangtang massif4)Combin the results of the article research and the studying results of predecessors,the combination of theories 8 Ma northeastern margin of qinghai-tibet plateau uplift of models for periodic uplift,average uplift rate was 0.13?0.25 mm/a.