青藏高原东北缘六盘山地区新生代构造旋转及其意义  

Cenozoic Tectonic Rotation of the Liupan Shan Region in the Northeastern Tibetan Plateau and Its Implications

作　　者：刘永前[1] 方小敏[1,2] 宋春晖[2] 李立立[2] 程彧[2] 

机构地区：[1]中国科学院青藏高原研究所盆地与资源环境研究中心,北京100085 [2]兰州大学西部环境教育部重点实验室／资源环境学院,甘肃兰州730000

出　　处：《大地构造与成矿学》2009年第2期189-198,共10页Geotectonica et Metallogenia

基　　金：中国科学院知识创新工程重要方向项目(编号:KZCX2-YW-104);国家教育部科学技术研究重大项目(编号:306016);国家973重点基础研究发展计划项目(2005CB422001)的联合资助

摘　　要：青藏高原东北缘构造变形的研究是认识高原隆起过程、机制和印度-欧亚板块碰撞远程效应的重要途径。新生代时期,海原-六盘山断裂、香山-天景山断裂、烟筒山-窑山断裂和青铜峡-固原断裂控制的青藏高原最东北缘六盘山地区山前盆地群,接受了巨厚的新生代沉积,较完整地记录了高原东北部的变形隆升历史。通过六盘山地区丁家二沟剖面的精细古地磁研究发现,白垩纪结束后至中新世六盘山地区发生了约23°的长期顺时针构造旋转,并主要发生在三个时期:可能于晚始新世至早渐新世六盘山地区发生了约9°的顺时针旋转、早渐新世晚期顺时针快速旋转约9°、早中新世初顺时针快速旋转约5°,同时它们也被地层变形侵蚀和沉积演化所记录,说明印度-欧亚板块碰撞变形的前峰最迟在约始新世末-渐新世初就已经达到六盘山地区。这比目前普遍认同的六盘山地区变形隆升是青藏高原隆起中最晚形成(第四纪以来)的观点早了至少3千多万年,它为深入认识高原隆升过程和环境效应提供了新的证据。The Liupan Shan region is located at the northeastern-most corner of the Tibetan Plateau in tectonics. A series of southward-arced sinistral faults （Haiyuan-Liupan Shah Fault, Xiang Shan-Tianjing Shan Fault, Yantong Shan-Yao Shan Fault and Qingtongxia-Guyuan Fault） control the formation and distribution of inter-fault blocks and basins, in which thick Cenozoic sediments were deposited. Knowledge of the evolution and deformation of this re- gion will enhance our understanding of the mechanisms of the Tibetan growth and its influence on global climate change. High-resolution paleomagnetie study of the Dingjiaergou section, 5 km north of Tongxin County, Ningxia Hui-autonomous Region shows a total 23° clockwise tectonic rotation of the Liupan Shan region from the Cretaceous to the Mid-Miocene, manifesting three intervals of fast rotations in 33 - 30Ma at 9 ±2.6° , in 30 - 23 Ma at 9± 3. 5°and in 23 -16 Ma at 5±3.7°. These rotations are accordant with some unconformities or sedimentary environmental rapid changes. All these indicate that the deformation frontier from the India-Eurasia collision had reached the Liupan Shan region at least about Late Eocene to the Early Oligocene, which is almost 30 million years earlier than the current general view that the deformation and uplift of the Liupan Shan had begun since the Quaternary.

关 键 词：青藏高原东北缘 六盘山 新生代 构造旋转 高原隆升变形 

分 类 号：P542[天文地球—构造地质学]