北部湾盆地北部坳陷马尾状构造成因新认识  

New insight into the origin of horsetail-like structure in Beibu depression,Beibu Gulf Basin

作　　者：刘一鸣 吴智平[1,2] 颜世永 杨希冰[3] 平明明 张勐 LIU Yiming;WU Zhiping;YAN Shiyong;YANG Xibing;PING Mingming;ZHANG Meng(School of Geosciences,China University of Petroleum,Qingdao,Shandong 266580,China;Key Laboratory of Deep Oil and Gas,Qingdao,Shandong 266580,China;Zhanjiang Branch of CNOOC,Zhanjiang,Guangdong 524057,China)

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [2]深层油气重点实验室,山东青岛266580 [3]中海石油(中国)有限公司湛江分公司,广州湛江524057

出　　处：《中国矿业大学学报》2021年第1期163-175,共13页Journal of China University of Mining & Technology

基　　金：“十三五”国家科技重大专项(2016ZX05024-002-001);国家建设高水平大学公派留学基金项目(201706450007)。

摘　　要：为明确北部湾盆地北部坳陷的构造演化历程和厘清走滑作用对盆地形成演化的控制和影响,利用最新的钻井资料、三维地震资料解释和地层年代学资料,通过对断裂时空演化及其沉积响应的精细刻画,并结合区域构造演化与局部应力特征分析,对盆地内以往认为具有走滑成因的马尾状构造进行了再研究,认为该马尾状构造为区域应力场旋转背景下不同期次断裂叠加的产物,受控于周缘板块重组所诱导的区域应力场转变,基底先存断裂的差异性活动控制了裂陷盆地的发育演化.研究结果表明:该构造的发育特征体现了伸展作用与走滑作用的叠加效应,并控制了古近纪盆地3幕显著差异的裂陷过程.断裂体系优势展布方向经历了由NE向(76.8°)→NEE向(82.8°)→近EW向(85.1°)的转型,主干断裂活动强度峰值经历了200→100→140m/Ma的转换,次级断裂数量经历了由306→103→389条的转变,不同幕次沉积中心厚度经历了5000→1800→2000m的演化过程.体现了古近纪早期NE向优势断裂体系在应力场旋转的背景下向NEE向转型,古近纪晚期形成的NW向和NEE向共轭走滑断裂体系对构造格局进行了强烈改造.明确了在古太平洋板块俯冲后撤产生的NNW-SSE向区域伸展背景下,NE向基底断裂的强烈张扭性活动控制了盆地的形成.先存断裂的斜向伸展和隐性断裂的走滑复活效应导致了盆内显著的走滑变形特征,决定了盆地现今复杂的构造面貌.受断裂分期和分段发育的控制,在陡坡带源岩内发育的各类扇体可以成为源内勘探的有利目标,NW向隐性走滑断裂带控制的压扭背斜应成为今后重要的勘探方向.This study aims to identify the tectonic evolution history of the Beibu Gulf Basin,and to distinguish the role of strike-slipping in controlling the basin formation and evolution.Based on the new released borehole data,3Dseismic data and latest strata age data,the spatial and temporal evolution of fault system and its sedimentation were studied.Combining with the analyses of regional tectonics and logical stress features,reinvestigation on horsetail-like structure which was always thought to be formed by slipping was carried out.It is suggested that the horsetail-like structure resulted from the overprint of episodic faulting caused by the clockwise rotation of the regional stress field,and was influenced by the regional stress change induced by the plate reorganization.The differential expressions of the pre-existing faults determined the distinct rifting stages of basin evolution.The results show that the structural characteristics reflect the overprint of extension and strike-slipping,which determined three distinct episodic rifting stages of the Paleogene basin.The distribution of controlling fault system experienced the transformation from NE(76.8°)to NWW(82.8°)to nearly EW-trending(85.1°).The peak value of dip-slip active faulting rate experienced the transition from 200to 100to 140 m/Ma.Besides,the number of minor faults changed from 306to 103to 389,and the thickness of depocenters shifted from 5000to 1800to 2000m.It was suggested that the basin-controlling NE-trending fault system transformed to NEE-trending during the Early Paleogene,and that the structural pattern was strongly reworked by the Late Paleogene strike-slipping,forming the conjugate NW and NEE shearing fault system.Under the NNW-SSE-oriented stretching due to the roll back of the Paleo Pacific Plate,the transtensional NE-trending faulting led to the basin formation.Besides,it was recognized that oblique extension and regional strikeslipping contributed to the striking shearing deformation within the basin,and the reactivation of pre-exist

关 键 词：马尾状构造 走滑作用 先存断裂 斜向伸展 裂陷演化 北部湾盆地 

分 类 号：P542[天文地球—构造地质学]