北祁连山晚中新世以来的隆升历史——来自河道高程剖面的约束

LATE MIOCENE UPLIFT HISTORY OF THE NORTHERN QILIAN SHAN CONSTRAINED BY THE LONGITUDINAL PROFILE

北祁连山作为青藏高原隆升与扩展的最前缘,一直以来都是研究的热点。本研究为弥补活动构造与热年代学方法时间尺度上难以链接的不足及提供青藏高原扩展隆升机制相关证据,利用河流水力侵蚀模型的方法模拟得出北祁连山河道陡峭指数与部分河流地质隆升历史。结果揭示出北祁连山河道陡峭指数与距断裂的距离存在显著关系,且具有从中间向东西两侧减小的特征,表现出北祁连山隆升速率大致也呈现自中向两侧减慢的特征;并通过分析处于北祁连山非沉积区白杨河、洪水坝河、丰乐河、马营河、大渚马河及洪水河这6条流域的地质隆升历史,发现在4 Ma左右,北祁连山隆升速率逐渐增加,且隆升速率大致在0.20~0.38 mm/a之间。直到0.6~1.0 Ma,隆升速率迅速加快,呈现陡增的趋势。因此,北祁连山的构造隆升并不是均匀的,而是随时间发生变化的。

The North Qilian Shan are located on the northeast edge of the Qinghai-Xizang Plateau,where a series of thrust fault zones have developed.They are roughly divided into three parts:the South,Central,and North Qilian Shan,divided by two large strike slip faults:the Haiyuan Fault and the Changma Fault.The selected rivers in this article are six river basins:Baiyang River,Hongshuiba River,Fengle River,Maying River,Dazhuma River,and Hongshui River.The Baiyang River is located in the central part of the Qilian Shan fault,the Hongshuiba River is between the West Qilian Shan fault and the Fodongmiao-Hongyazi fault,the Fengle River is located in the central part of the Fodongmiao-Hongyazi fault,the Maying River is located in the eastern part of the Fodongmiao-Hongyazi fault,and the Dazhuma River and Hongshuihe River are located in the central part of the Zhangye fault.The 10 Be samples were collected from metamorphic rocks,granite,and some sedimentary rocks located in the Mesozoic or Quaternary periods during the Carboniferous Ordovician and Precambrian periods.Using the RiverProAnalysis method,a set of river elevation profile analysis functions,to simulate the geological uplift history of the samples.Research has found that at around 4 Ma,the uplift rate of the North Qilian Shan gradually increases,and the uplift rate is roughly between 0.20 mm/a and 0.38 mm/a.Until 0.6~1.0 Ma,the uplift rate rapidly accelerated and showed a steep increase trend.Therefore,the tectonic uplift of the North Qilian Mountains is not uniform,but changes over time.