Ages and geological significance of the river terrace of Datong River in Qilian Mountains
YU Hang1, BU Fan1, HU Daogong2, ZHANG Xujiao3, YANG Jinzhong1
1.China Aero Geophysical Survey and Remote Sensing Center for Land and Resources, Beijing 100083, China; 2.Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China; 3.China University of Geosciences(Beijing), Beijing 100083, China
摘要祁连山是研究青藏高原隆升与构造变形的关键部位,其中大通河河流阶地是祁连山地区早更新世以来构造隆升和气候变化的载体,厘定大通河河流阶地的形成时代及地质意义对于分析祁连山地区的区域构造和气候环境改变具有重要意义。通过ESR测年技术,并对大通河流域江仓区域的剖面样品实测,获取岩层形成时代数据,分别为(42±4) ka B.P.、(71±5) ka B.P.、(121±12) ka B.P.、(210±20) ka B.P.和(602±60) ka B.P.。根据测年结果,确认剖面为河流相沉积环境,形成时代对应中晚更新世酒泉砾岩和戈壁砾岩时期,表明大通河河流阶地在542~662 ka B.P.之前就已经形成,推测其可能是受到中新世白杨河组之后的盆山运动或早更新世祁连山的褶皱变形影响而形成的。利用测年数据计算抬升速率,从中更新世晚期到晚更新世中期,抬升速率加快,反映了大通河流域的构造运动和气候变化加强,祁连山江仓地区在此期间快速隆升,为青藏高原东北缘以面积和体积扩张的观点提供了新的依据。
Abstract：Qilian Mountains are the key study areas for tectonic deformation and uplift of Tibetan Plateau. Since Early Pleistocene, the river terrace of Datong River has been the record of tectonic uplift and climate changes in Qilian Mountains. Ascertaining the ages and geological significance of the river terrace of Datong River is of great significance in analyzing the regional structure and climate changes in Qilian Mountains. Using ESR dating technique, the authors measured the section samples in Jiangcang Area of Datong River and acquired the rock strata ages, which were (42±4) ka B.P., (71±5) ka B.P., (121±12) ka B.P., (210±20) ka B.P. and (602±60) ka B.P. respectively. According to the dating results, the authors confirmed the section was formed in the environment of fluvial facies deposition, and that its ages were the periods of Jiuquan conglomerate and Gobi conglomerate in Middle and Late Pleistocene. And it showed that the river terrace of Datong River has been formed before 542~662 ka B.P., and that its formation might be influenced by the basin-mountain movement after Miocene Baiyanghe Formation or by the wrinkle deformation in Early Pleistocene in Qilian Mountains. The authors calculated the uplift rate via the dating results, and the results showed that the uplift rate was increasing from the late period of Middle Pleistocene to the middle period of Late Pleistocene, which reflected the enhancement of tectonic movement and climate changes in Datong River Basin and the rapid uplift of Jiangcang Area in Qilian Mountains. These conclusions could provide new proofs for the viewpoint that the northeastern edge of Qinghai-Tibet Plateau has expanded in both area and volume.
于航, 步凡, 胡道功, 张绪教, 杨金中. 祁连山大通河河流阶地形成时代及地质意义[J]. 中国地质调查, 2018, 5(3): 43-48.
YU Hang, BU Fan, HU Daogong, ZHANG Xujiao, YANG Jinzhong. Ages and geological significance of the river terrace of Datong River in Qilian Mountains. , 2018, 5(3): 43-48.
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2018, Vol. 5 
