南海北缘古近纪断裂活动规律及控盆特征:以阳江东凹为例  

Paleogene Fault Activity and Basin Controlling Characteristics in the Northern South China Sea Margin-A Case Study of the Eastern Yangjiang Sag

作　　者：占华旺 蔡国富 张志伟 王光增 李颖薇 索艳慧[1,2] 王鹏程 姜素华[1,2] 刘博 郭玲莉[1,2] 朱俊江 李三忠[1,2] ZHAN Huawang;CAI Guofu;ZHANG Zhiwei;WANG Guangzeng;LI Yingwei;SUO Yanhui;WANG Pengcheng;JIANG Suhua;LIU Bo;GUO Lingli;ZHU Junjiang;LI Sanzhong(Frontiers Science Center for Deep Ocean Multispheres and Earth System,Key Lab of Submarine Geosciences and Prospecting Techniques,MOE and College of Marine Geosciences,Ocean University of China,Qingdao 266100,Shandong,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266100,Shandong,China;Shenzhen Branch,CNOOC China Limited,Shenzhen 518000,Guangdong,China)

机构地区：[1]深海圈层与地球系统教育部前沿科学中心,海底科学与探测技术教育部重点实验室,中国海洋大学海洋地球科学学院,山东青岛266100 [2]青岛海洋科学与技术国家实验室海洋矿产资源评价与探测技术功能实验室,山东青岛266100 [3]中海石油(中国)有限公司深圳分公司,广东深圳518000

出　　处：《大地构造与成矿学》2021年第1期20-39,共20页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(91958214、41976054);国家科技重大专项(2016ZX05004001-003);泰山学者项目对李三忠和刘永江教授的资助;青岛创新领军人才项目(19-3-2-19-zhc);中央高校科研经费联合资助。

摘　　要：南海北缘发育了一系列新生代陆缘盆地,从西向东可划分为北部湾盆地、琼东南盆地、珠江口盆地及台西南盆地,这些盆地记录了新生代南海北缘构造演化过程。为加深对南海北部陆缘新生代盆地断裂活动及构造演化的认识,本文以珠三坳陷阳江东凹为例,基于覆盖阳江东凹研究区的高分辨率三维地震资料,对该地区的断裂体系进行了系统解剖,阐述了古近纪断裂的展布特征,并对主干断裂的活动速率进行定量计算,探讨了断裂体系演化规律及沉积中心迁移过程,并利用2Dmove软件对典型地震剖面进行了构造演化恢复。结果表明,文昌组沉积期阳江东凹主要以NE-NEE向断裂活动为主,且活动强度大;恩平组沉积期,NWW向断裂大量发育,少数NE-NEE向断裂继续活动。阳江东凹的断裂活动表现出从早到晚,同沉积主干断裂走向由NE-NEE向转变为近E-W向和NWW向,同时沉积中心相应的整体向西、向南迁移。而单一主干断裂在不同位置不同时期,其活动强度也存在差异。基于断裂体系展布特征和平衡剖面分析,本文认为阳江东凹的基底作为中生代华南陆缘的一部分,经历了多次变形作用,形成了NE向和NWW向基底卷入型共轭断裂;早-中始新世, NE向先存断裂在NW-SE向应力作用下优先复活,其断裂活动强度达到最大;进入中-晚始新世, NE向断裂活动继承性发展, NEE向断裂大量发育,在右旋应力作用下,早期NE向断裂呈右行右阶走滑,控制着地层沉积与断裂构造样式;至渐新世,NE向断裂少数继承性活动,近E-W向及NWW向断裂大量发育,以左行走滑方式存在。因此,阳江东凹裂陷期主要经历了文三段沉积期NW-SE向伸展、文二段沉积期NE向右行右阶走滑拉分和文一段-恩平组沉积期NWW向左行左阶走滑拉分的三阶段演化过程。结合前人对南海北部陆缘研究成果可知,南海北缘盆地群宏观格局主要为受NE向断裂控制The Cenozoic continental marginal basins in the northern South China Sea margin can be divided into the Beibu Gulf Basin,the Qiongdongnan Basin,the Pearl River Mouth Basin,and the Taixinan Basin from west to east.These basins recorded the Cenozoic evolution of the northern South China Sea margin.To deepen the understanding of the fault activity and the Cenozoic tectonic evolution in the northern South China Sea margin,a case study of the eastern Yangjiang Sag in the ZhuⅢDepression was carried out on the bases of high-resolution 3D seismic data.The 2D move software was used to restore the structural evolution of representative seismic profiles.The results showed that the structures in the eastern Yangjiang Sag during depositional period of the Wenchang Formation were dominated by the intensive NE-NEE-striking faults.By the depositional period of the Enping Formation,the NWW-striking faults became prevalent while a few NE-NEE-trending faults remainded active.The estimated activity rates showed that from early to late,the strikes of syn-sedimentary main faults changed from NE-NEE to near EW and NWW,while the corresponding depocenter migrated westward and southward.However,the activity intensity of individual main faults varied both temporally and spatially.The distribution and balanced cross sections of the fault system showed that the Mesozoic basement in the eastern Yangjiang Sag underwent multiple deformation and formed NE-and NWW-trending conjugate basement-involved faults.In the Early-Middle Eocene,the NE-striking pre-existing fault was preferentially re-activated under NW-SE-directed stress field,and its fault activity reached its climax during this period.During the Middle-Late Eocene,under the influence of the dextral slipping,the NE-trending faults evolved into NEE-striking and formed the NE-striking dextral faults which are characterized by right-step strike-slip and controlled the sedimentation and fault pattern.In the Oligocene,the NE-trending faults were mostly ceased,and the near-EW-and NWW-trending

关 键 词：南海北部陆缘 阳江东凹 控盆断裂 活动强度 平衡剖面 构造演化 

分 类 号：P542[天文地球—构造地质学] P618.13[天文地球—地质学]