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引用本文:卢海建1 王二七2 李仕虎3 李海兵1. 青藏高原东南缘构造旋转变形分析:以四川盐源盆地古地磁研究为例[J]. 中国地质, 2015, (5): 1188-1201.
LU Hai-jian1, WANG Er-qi2, LI Shi-hu3, LI Hai-bing1. Rotational deformation of the southeastern margin of Tibet: A paleomagnetic study of the Yanyuan basin, Sichuan Province[J]. Geology in China, 2015, (5): 1188-1201(in Chinese with English abstract).
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青藏高原东南缘构造旋转变形分析:以四川盐源盆地古地磁研究为例
卢海建1 王二七2 李仕虎3 李海兵1
作者单位
卢海建1 王二七2 李仕虎3 李海兵1 1. 中国地质科学院地质研究所大陆构造与动力学国家重点实验室 北京 1000372. 中国科学院地质与地球物理研究所特提斯研究中心 北京 1000293. 中国科学院地质与地球 物理研究所岩石圈演化国家重点实验室 北京 100029 
摘要:
提要:探究青藏高原东南缘构造旋转变形有助于理解青藏高原内部物质向东南方向的挤出过程。目前,有关青藏高原东南缘的构造旋转研究主要针对于两套地层:侏罗系—始新统和中新统—第四系。对侏罗系—始新统研究表明了大范围的顺时针旋转变形的存在,而对中新统—第四系的研究则表明该区域可能同时存在逆时针旋转变形。然而,对这两种构造旋转变形的时间和幅度仍缺乏充分的制约。位于川滇地块的四川盐源盆地同时出露这两套地层。磁性地层研究表明,上新统—中更新统的时代为>3.6~0.6 Ma。磁偏角数据揭示上新统—中更新统经历了逆时针旋转变形(-14.4°±2.7°),而古新统—始新统经历了明显的顺时针旋转 (10°~21.5°),两套地层间的旋转幅度高达36.6°。鉴于青藏高原东南缘发生大规模顺时针旋转变形的最年轻地层为始新统地层,因此顺时针旋转变形可能发生在始新世—中新世某个时间段。这个时间与红河—哀牢山走滑断裂带的活动时间基本一致,因此顺时针旋转变形可能与该大型断裂带的活动直接相关。盐源盆地记录到的逆时针旋转变形发生于至少3.6 Ma以来,平均旋转速率为4°/Ma。由于磁组构数据表明上新世—中更新世地层并未受到挤压变形作用,因此其逆时针旋转变形可能受周围走滑断裂带的控制。
关键词:  磁性地层  旋转变形  新生代  盐源盆地  青藏高原东南缘
DOI:
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基金项目:国家自然科学基金面上项目(41472187)、国家自然科学基金重点项目(41130312)资助。
Rotational deformation of the southeastern margin of Tibet: A paleomagnetic study of the Yanyuan basin, Sichuan Province
LU Hai-jian1, WANG Er-qi2, LI Shi-hu3, LI Hai-bing1
Abstract:
Abstract: Investigating rotational deformation of the southeastern margin of the Tibet is the key to understanding how and why the Tibet material extruded to the southeast. Until now there are two sets of strata used to study the rotational deformation on the southeastern margin of the Tibet: the Jurassic-Eocene and the Miocene-Quaternary strata. Paleomagnetic studies of the Jurassic-Eocene strata indicate widespread clockwise rotational deformation, similar studies of the Miocene-Quaternary strata suggest multiple deformation patterns, including clockwise rotation, counter-clockwise rotation and also no rotation. However, it is still not well constrained as to the timing and degree of rotational deformation on the southeastern margin of Tibet. Two sets of strata (the Paleocene-Eocene and Pliocene-Quaternary sediments) are well exposed in the Yanyuan basin, Sichuan Province. Magnetostratigraphic studies indicate an age of >3.6-0.6 Ma for the Pliocene-Quaternary strata. Declination data suggest that the Pliocene-Quaternary sediments experienced counter-clockwise rotation (-14.4°), and the Paleocene-Eocene deposits underwent notable clockwise rotation (10°-21.5°). As the age of the youngest strata that experienced clockwise rotational deformation on the southeastern margin of Tibet is the Eocene, the clockwise rotational deformation likely occurred during a time interval between the Eocene and the Miocene. The counter-clockwise rotational deformation recorded in the Yanyuan basin happened before 3.6 Ma with an average rotational rate of 4°/Ma. Since anisotropy of magnetic susceptibility (AMS) data indicate that the Pliocene-Quaternary sediments underwent no compressional deformation at all, the counter-clockwise rotational deformation was initiated most likely by strike-slip faults around the Yanyuan basin.
Key words:  magnetostratigraphy  rotational deformation  Cenozoic  Yanyuan basin  southeastern margin of the Tibet