东沙群岛海区晚新生代构造特征及其对弧-陆碰撞的响应  

LATE CENOZOIC NEOTECTONICS IN THE DONGSHA ISLANDS REGION AND ITS RESPONDS TO COLLISION BETWEEN CHINESE CONTINENTAL MARGIN AND LUZON

作　　者：吴时国[1] 刘展[2] 王万银[3] 郭军华[1,4] Lüdmann T Wong H K 

机构地区：[1]中国科学院海洋研究所 [2]石油大学 [3]长安大学地质与测绘工程学院 [4]中国科学院研究生院北京100039 [5]德国汉堡大学生物地球化学研究所

出　　处：《海洋与湖沼》2004年第6期481-490,共10页Oceanologia Et Limnologia Sinica

基　　金：中国科学院知识创新重要方向性项目 ;KZCX3 SW 2 19号 ;国家"973"重点基础研究资助项目 ;2 0 0 0 0 6 4 70 4号 ;中国科学院院长基金项目 ;2 0 0 10 30 2号

摘　　要：东沙群岛及其邻近海区 (简称东沙海区 )位于南海北部大陆边缘 ,东邻马尼拉俯冲构造带。为了讨论晚新生代以来东沙海区的构造变形特征 ,从中找出吕宋弧对中国东南大陆边缘碰撞的构造相关 ,特别是 8Ma以来的吕宋岛弧和中国大陆边缘之间构造消减过程的响应。根据地震地层学分析 ,结合区域重磁资料、ODP1 84钻孔资料对东沙群岛海区晚新生代构造特征进行了分析。东沙海区自南海扩张后发育了 3个沉积层序 (层序Ⅴ ,Ⅵ ,Ⅶ ) ,经历了较强烈的构造抬升作用、岩浆活动、沉积物剥蚀。该区发育NEE SWW和NW SE向两组断裂 ,且以NEE SWW向断裂最为发育。断裂大多具有多次活动 ,且为上新世到第四纪的活动断裂构造 ,断块抬升幅度大 ,沿断裂带发生岩浆侵入。分析结果表明 ,晚新生代期间经历了二次重要的构造运动 ,即东沙运动 ( 9 8— 4 4Ma)和流花运动 ( 1 89— 1 4Ma) ,奠定了该区的构造格局。综合该区东强西弱构造变形、构造抬升发生的时间和应力场变化等特征看 ,该区受 8Ma以来中国东部大陆边缘与吕宋岛弧碰撞所产生的构造运动的影响 ,在 8Ma以前 ,由于台湾岛不存在 ,活动的古东海大陆边缘延伸至东沙群岛海区东北部。Dongsha Islands and adjacent sea area located at northern continental margin of the South China Sea (SCS), which is connected to the Manila Trench to the east. In order to discuss the deformation characteristics of Dongsha Islands and adjacent sea area since Late Cenozoic, and to reveal the tectonics shaped by the collision between Luzon arc and southeast Chinese continental margin, especially the responds caused by the collision, according to the analyses of seismic stratigraphy in combination with gravity, magnetic and drilling wells data, three post-rift sequences (Ⅴ, Ⅵ, Ⅶ) have been discerned. Sequence Ⅰ—Ⅲ deposited before the SCS rifting overlying the acoustic basement with subparallel, discontinuous and medium to high amplitude reflectors and typical faulted basin sedimentation. Terrestrial sandstones, siltstones are the major lithofacies. Sequence Ⅰ, Ⅱ and Ⅲ correspond to Shenhu, Wanshan and Enping formations, respectively. Sequence Ⅳ appeared in the shelf margin of the Dongsha rise, and is comprised of carbonate facies and carbonate reef facies. Well-logging showed that the bottom of this sequence is composed of chaotic, hyperbolic and high amplitude reflectors. The seismic facies may vary from fluvial to estuarine facies corresponding to Zhujiang formation. The upper part is characterized by continuous and high amplitude parallel reflectors. Sequences Ⅳ and Ⅴ are divided by regional unconformity. Sequence Ⅴ and Ⅵ are marked by very continuous, high amplitude and parallel reflectors representing Miocene and Pliocene deltaic mudstones and siltstones making Yuehai formation and Hanjinag formation. The seismic exterior of the sequence changes from parallel to slanting across structural cover. The unconformity on the top (T 1) is the boundary between Miocene and Pliocene. Sequence Ⅶ downlaping and terminating on Sequence Ⅵ in the east of the study area, formed after the spreading of the SCS, and consists of parallel, continuous and medium to high amplitude reflectors

关 键 词：晚新生代构造运动 地震地层学 弧-陆碰撞 南海 

分 类 号：P736[天文地球—海洋地质]