南海礼乐盆地新生代构造沉降特征及其成因分析  

Tectonic subsidence and its mechanism of the Liyue Basin,South China Sea

作　　者：裴健翔 施小斌[3,4] 王丽芳 任自强 谌永强[3,5] 史德锋 刘奎 赵鹏 闫安菊[1,2] PEI Jianxiang;SHI Xiaobin;WANG Lifang;REN Ziqiang;SHEN Yongqiang;SHI Defeng;LIU Kui;ZHAO Peng;YAN Anju(Hainan Energy Ltd.of CNOOC,Haikou 570100,China;Zhanjiang Branch of CNOOC Ltd.,Zhanjiang 524057,China;Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences,Guangzhou 510301,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China;University of Chinese Academy of Science,Beijing 100049,China)

机构地区：[1]中海油海南能源有限公司,海口570100 [2]中海石油(中国)有限公司湛江分公司,湛江524057 [3]中国科学院边缘海与大洋地质重点实验室,南海海洋研究所,南海生态环境工程创新研究院,广州510301 [4]南方海洋科学与工程广东省实验室(广州),广州511458 [5]中国科学院大学,北京100049

出　　处：《海洋地质与第四纪地质》2020年第4期17-29,共13页Marine Geology & Quaternary Geology

基　　金：国家科技重大专项课题(2017ZX05026-005);国家自然科学基金项目“南海北部陆缘异常构造沉降形成机制与破裂阶段热状态的数值模拟”(41776078);南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0104)。

摘　　要：为深入认识礼乐盆地的构造演化史,基于已有钻井资料和重新处理解释的地震数据,对区内43个代表点进行了系统的沉降史重建,发现礼乐盆地新生代3个演化阶段分别具有快速、缓慢和快速的构造沉降特点,并且总构造沉降量与地壳减薄程度密切相关;礼乐滩礁体发育区晚渐新世以来构造沉降量为580~900 m,礁体厚度与构造沉降量和下伏沉积层厚度有关.分析表明礼乐盆地构造沉降具有"先抑后扬"的特征,礼乐地块裂离和漂移阶段,构造沉降受到深部热物质上涌产生的浮力作用而出现明显亏损,拗陷阶段,礼乐盆地随着南海海底扩张停止而失去深部浮力的支持,从而发生幕式的快速构造沉降,以补偿早期亏损的构造沉降.In order to further understand the tectonic evolution of the Liyue Basin,we systematically rebuilt the tectonic subsidence history for 43 representative stations selected from existing drill holes with reprocessed 2D seismic data.The results suggest that the Cenozoic tectonic subsidence are characterized by rapid,slow and rapid tectonic subsidence responding to the three tectonic evolutionary stages of synrift,drift and subsidence,respectively,and the total tectonic subsidence is mainly controlled by the thinning crust.In the Reed Bank,the accumulated tectonic subsidence since Late Oligocene has reached a figure from 580 m to 900 m.However,the thickness of the reef deposits not only depended on tectonic subsidence,but also related to the thickness of the underlying Cenozoic deposits.Further analyses suggest that the tectonic subsidence history of the Liyue basin is featured by a slow early subsidence followed by a rapid subsidence,while the deficit of tectonic subsidence during the margin breakup and drift stages might be caused by the buoyancy of the upwelling thermal asthenosphere material driven by seafloor spreading.Since Middle Miocene,with the cessation of seafloor spreading in the South China Sea,the upwelling of deep hot material became so weak that could not provide enough buoyancy to support the overlying Liyue basin,episodic rapid subsidence thus occurred for compensating the earlier deficit of subsidence.

关 键 词：构造演化 异常沉降 南沙海域 礼乐地块 礼乐滩 

分 类 号：P736.1[天文地球—海洋地质]