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学科主题: 地球科学::地质学
题名: 青藏高原东北缘六盘山地区新生代构造旋转研究
作者: 刘永前
答辩日期: 2008
导师: 方小敏
授予单位: 中国科学院研究生院
授予地点: 北京
学位: 硕士
关键词: 青藏高原 ;  六盘山 ;  新生代地层 ;  构造旋转 ;  变形隆升
索取号: S000010
部门归属: 图书馆
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。通过六盘山地区由南向北跨越不同断裂围限地块和盆地的5个代表性剖面新生代地层古地磁平均磁偏角的变化研究,表明该区于早白垩世结束以来各断裂块体基本经历了非常相似的构造旋转历史,早白垩世结束后至中新世早期累计总体顺时钟旋转了约23-29o,旋转不是连续进行,而是呈现为事件性快速旋转,主要发生在约33Ma、30Ma和23Ma,中新世期间几乎没有任何有意义的旋转,晚中新世约8Ma六盘山地区结束盆地沉积,仅在六盘山西南侧的天水盆地继续接受沉积,那里自上新世中期约3.6Ma发生了快速顺时针构造旋转。早期的长期顺时钟旋转在六盘山最北面的丁家二沟剖面和中部的隆德剖面表现为地块自早白垩纪结束后至渐新世初期期间(~33Ma-~30Ma)发生了约9°和12°的顺时针旋转,早渐新世晚期(~30Ma-~23Ma)研究区有约9°和13°的顺时针快速旋转,而在中新世初期(~23Ma)至中期期间再次产生了约5°的顺时针旋转;六盘山南部的泾源剖面渐新世初期至早渐新世晚期(~30Ma-~23Ma)研究区有8.8°的顺时针快速旋转,而在中新世初期(~23Ma)至中期期间再次产生了4.9°的顺时针旋转;而六盘山中部的凤凰蛋剖面在中新世初、中期(~21.8Ma)至中新世末(~8.1Ma)期间未发生有意义的构造旋转;六盘山西南面的天水喇嘛山剖面自中新世中期(~15.6Ma)至上新世中期(~3.6Ma)期间也未发生有意义的构造旋转,但在上新世中期之后(约3.6Ma)发生了约12°的快速顺时针旋转。结合其它地层变形、侵蚀和沉积演化所记录,推测海原-六盘山断裂或阿尔金断裂因印度-欧亚大陆板块碰撞的巨大驱动力作用下产生了大规模的走滑,从而可能引起六盘山地区各地块间大型弧形断裂的同时激活,发生左旋走滑,断裂间块体开始同时顺时针构造旋转,揭示印度-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,为深入认识高原隆升过程和环境效应提供了新的证据。
英文摘要: The Liupan Shan region is the northeastern-most corner of the Tibetan Plateau in tectonics. A series of southward-arced sinistral faults (Haiyuan– Liupan Shan 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 region will enhance our understanding of the mechanisms of the Tibetan growth and its influence on global climate change. High-resolution paleomagnetic study of Longde Section, Dingjiaergou section, Jingyuan Section, Fenghuangdan Section and Lama Shan Section, shows different vast scales clockwise tectonic rotation of the Liupan Shan region from the Cretaceous to the Mid-Miocene and since Mid-Pliocene, manifesting as three intervals of fast rotations in ~33 Ma-~30Ma at ~9° and ~12°, in ~30Ma-~23Ma at ~9° and ~13°, in ~23Ma-~16.2Ma at ~5° from Longde Section and Dingjiaergou Section; in ~30Ma-~23Ma at ~8.8° and ~13°, in ~23Ma-~16.2Ma at 4.9° from Jingyuan Section; no roation in ~21.8Ma-~8.1Ma from Fenghuangdan Section; no rotation in ~15.6Ma-~3.6Ma, since 3.6Ma at 12°. 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 latest at about late Eocene to the early Oligocene, which is at least ~30 million years earlier than the current general view that the deformation and uplift of the Liupan Shan began since the Quaternary, adding new information for colleagues.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.itpcas.ac.cn/handle/131C11/1203
Appears in Collections:图书馆_学位论文

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Recommended Citation:
刘永前.青藏高原东北缘六盘山地区新生代构造旋转研究[硕士].北京.中国科学院研究生院.2008
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