| 西江凹陷早新生代断裂演化及其对南海北缘应力场顺时针旋转的响应 |
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| 引用本文： | 程燕君,吴智平,张杰,陈明明,戴伊宁,楚逸忱.西江凹陷早新生代断裂演化及其对南海北缘应力场顺时针旋转的响应[J].地球科学,2020,45(6):2199-2209. |
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| 作者姓名： | 程燕君 吴智平 张杰 陈明明 戴伊宁 楚逸忱 |
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| 作者单位： | 中国石油大学地球科学与技术学院, 山东青岛 266580 |
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| 基金项目： | 国家重大科技专项No.2016ZX05024-002-001山东省自然科学基金博士基金No.ZR2017BD013中国石油大学(华东)自主创新科研计划项目No.17CX02004A |
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| 摘 要： | 南海北部发育了一系列的新生代盆地，该类盆地记录了新生代早期南海北缘应力场顺时针旋转过程，西江凹陷位于珠江口盆地内，记录了这一过程.利用丰富的二维、三维地震资料，针对西江凹陷断裂体系的演化过程进行了研究.凹陷基底在新生代之前作为华南陆缘的一部分，经历了多期次复杂的构造演化，形成了NE和NW两个方向的基底断层; 早-中始新世，NE向先存断裂优先复活，由太平洋板块俯冲后撤在研究区产生的NW-SE向伸展应力所致; 晚始新世-早渐新世，近EW向断裂大量发育，NW向断裂以走滑方式复活，该时期断层演化主要受太平洋俯冲方向的变化、印度板块碰撞及古南海的拖拽导致该地区应力场顺时针转变为近NS向的影响; 进一步通过物理模拟实验验证了断裂的演化机制，NE向先存断裂施加NS向拉张应力，先存NE向断裂局部复活，大量近EW向断层沿着NE向先存断裂展布位置形成，剖面上表现为正断层; NW向断裂在NS向拉张应力条件下，可见NW向走滑大量复活，局部发育少量的近EW向断裂.该研究对南海北缘新生代应力转变过程研究具有重要的借鉴意义.
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| 关 键 词： | 断裂体系 应力旋转 西江凹陷 物理模拟 早新生代 石油地质 |
| 收稿时间： | 2019-07-18 |
Early Cenozoic Evolution of Fault System in Xijiang Sag and Its Implication to Clockwise Rotation of Extension Stress in Northern Margin of South China Sea |
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| Abstract: | The Xijiang sag is located in the Pearl River Mouth basin, the northern margin of the South China Sea. As one of the Cenozoic sags developed along the northern margin of the South China Sea, this sag recorded the clockwise rotation process of extension stress of the northern margin of the South China Sea. Thus, the study on the geological structure and evolution of this sag would provide robust evidence to this phenomenon. Based on the 2-D and 3-D seismic data, in this paper, it analyzes the Early Cenozoic evolution of the fault system in Xijiang sag. As part of the South China block, the basement of the Xijiang sag experienced several stages of complex evolutions, such as the Indo-China-Asian collision during Triassic, the subduction of Izenaqi plate and Pacific plate, which induced the formation of NE- and NW- striking faults in the basement. During Early to Middle Eocene, the pre-existing NE-striking faults reactivated under the control of the NE-SE-directed extension, and this extension was derived from the NNW-direction subduction of the Pacific plate under the Asian plate. During Late Eocene to Early Oligocene, the extension direction clockwise rotated from NW-SE to N-S, which induced the formation of large amount of EW-striking normal faults and the reactivation of the pre-existing NW-striking fault. This rotation resulted from the direction change of the subduction direction of the Pacific plate from NNW to NWW, the India-Asian collision and the southern ward movement of the Proto-South China Sea block. The analogue experiments are used to investigate the mechanism of the fault evolution. The results show that: (1) under the N-S direction extension, a large amount of EW-striking normal faults formed along the pre-existing NE-striking faults; (2) under the N-S direction extension, a group of pre-existing NW-striking strike-slip faults reactivated, and a small group of EW-striking extensional fault formed. |
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