珠江口盆地白云凹陷裂陷期断裂活动特征与动力学机制  

Fault Activity and Dynamic Mechanisms During the Rifting Stage in the Baiyun Depression of the Pearl River Mouth Basin

作　　者：马凌 单玄龙[1] 向绪洪 郝国丽[1] 张朋霖 闫博 衣健[1] Ma Ling;Shan Xuanlong;Xiang Xuhong;Hao Guoli;Zhang Penglin;Yan Bo;Yi Jian(College of Earth Sciences,Jilin University,Changchun 130061,China;CNOOC Deepwater Development Limited,Shenzhen 518054,Guangdong,China;CNOOC China Limited,Shenzhen Branch,Shenzhen 518054,Guangdong,China)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]中海石油深海开发有限公司,广东深圳518054 [3]中海石油(中国)有限公司深圳分公司,广东深圳518054

出　　处：《吉林大学学报（地球科学版）》2024年第6期1968-1985,共18页Journal of Jilin University：Earth Science Edition

基　　金：中国海洋石油有限公司“十四五”重大科技项目(KJGG2021-0100)。

摘　　要：珠江口盆地深水区白云凹陷构造特征复杂,勘探程度低,对凹陷内部断裂构造特征仍需深入研究,其裂陷期断层活动性及区域应力场动态演化亟需厘清。为揭示南海北部陆缘深水区白云凹陷裂陷期断裂活动特征及动力学机制,本文以珠二坳陷白云凹陷为例,基于最新的三维地震资料和地层解释方案,应用相干属性、古落差法等方法对白云凹陷的构造特征进行相关分析。研究表明:白云凹陷主要活动断裂划分为一级控盆断裂、二级控凹断裂、三级控带断裂;依据高精度的三维地震资料,在研究区识别出铲状断裂、阶梯状断裂、Y字形断裂、嵌套V字形断裂、似花状断裂5种断裂类型;平行式断裂、雁列式断裂、斜交式断裂、帚状断裂4种断裂组合样式。结合各时期断裂产状特征,定量统计507条断裂,进而分析区域应力场的动态演化并探讨其动力学机制。研究表明:在早始新世—晚始新世期间,断裂走向呈现NE—NEE—EW向顺时针旋转;结合断裂古落差分析,一级断裂的活动强度在逐渐减弱,同一时期不同断裂活动性及同一断裂在不同位置差异显著;研究区共发育早文昌、晚文昌和恩平组3期断裂活动。基于此,本文探讨了白云凹陷裂陷期动力学成因机制,同前人认为是印度—欧亚板块碰撞、太平洋板块俯冲后撤和古南海持续南移的耦合作用相互印证,形成了研究区典型的伸展拉张背景。The Baiyun sag in the deepwater area of the Pearl River Mouth basin is characterized by complex tectonic features and low exploration levels.There is still a need for in-depth research on the fault structures within the sag,and the activity of faults during the rifting stage and the dynamic evolution of the regional stress field remains unclear.To reveal the fault activity characteristics and dynamic mechanisms during the rifting stage in the Baiyun sag of the northern margin of the South China Sea,this paper takes the Baiyun sag in the ZhuⅡdepression as an example.Based on the latest 3D seismic data and stratigraphic interpretation schemes,methods such as coherence attributes and ancient fault throw analysis are used to analyze the tectonic characteristics of the Baiyun sag.The main active faults in the Baiyun sag are classified into three levels:First-order basin-controlling faults,second-order sag-controlling faults,and third-order zone-controlling faults.Based on high-resolution 3D seismic data,five fault types were identified in the study area:Flower-like faults,imbricate faults,step faults,Y-shaped faults,and nested V-shaped faults.Four fault combination patterns were identified:Parallel faults,en-echelon faults,oblique faults,and broom-like faults.By quantitatively analyzing the characteristics of 507 faults across different periods,the dynamic evolution of the regional stress field and its associated dynamic mechanisms were further explored.The study shows that from the Late Eocene to the Early Oligocene,the fault orientations underwent a clockwise rotation from NE NEE to EW.Based on the analysis of ancient fault throw,the activity intensity of the first-order faults gradually weakened,and significant differences were observed in the activity of different faults during the same period,as well as in different segments of the same fault.Three phases of fault activity were identified in the study area:The Late Wenchang,Early Wenchang,and Enping Formations.Finally,the paper discusses the dynamic mechanisms

关 键 词：南海北部陆缘 珠江口盆地 白云凹陷 区域应力 断层活动性 断裂类型 组合样式 

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