西沙孤立碳酸盐台地的地震层序及演化模式——以永乐环礁为例  

Seismic sequence and evolution model of isolated carbonate platform—A case from Yongle Atoll,Xisha Islands

作　　者：李学林 张汉羽 刘刚[3] 韩孝辉 秦永鹏 吴时国 LI Xuelin;ZHANG Hanyu;LIU Gang;HAN Xiaohui;QIN Yongpeng;WU Shiguo(Guangzhou Marine Geological Survey,China Geological Survey,Guangzhou,510075,China;Laboratory of Marine Geophysics and Georesources,Institute of Deep-Sea Science and Engineering,CAS,Sanya 572000,China;Institute of Marine Geology Survey and Research,Hainan Province,Haikou 570206,China)

机构地区：[1]中国地质调查局广州海洋地质调查局,广州510075 [2]中国科学院深海科学与工程研究所海底资源与探测技术重点实验室,三亚572000 [3]海南省海洋地质调查研究院,海口570206

出　　处：《海洋地质与第四纪地质》2020年第5期87-96,共10页Marine Geology & Quaternary Geology

基　　金：NSFC-广东联合基金重点基金项目“南沙海区减薄陆壳裂陷盆地构造演化及特色深水油气系统”(U1701245);国家科技重大专项课题“南海中建海域深水油气地质条件及目标评价”(2017ZX05026-006);中国地质调查局地质调查项目(DD20190209;DD20190216)。

摘　　要：永乐环礁作为典型的现代孤立碳酸盐台地,记录了西沙海域生物礁以及碳酸盐台地的整个兴衰历史。根据新采集的高分辨率多道地震数据,结合永乐环礁琛科2井以及永乐环礁东部西科1井的研究结果,对永乐环礁内部进行层序地层学研究,讨论了永乐环礁的演化过程,建立了西沙孤立碳酸盐台地的发育模式。根据地震反射同相轴特征变化,自下而上划分出Sq1(下中新统)、Sq2(中中新统)、Sq3(上中新统)、Sq4(上新统)、Sq5(第四系)5个层序,建立了永乐环礁的年代地层格架。重建了永乐碳酸盐台地自中新世以来的演化历史:台地顶部自中新世以来沉积环境相对稳定,以潟湖为主;而台地斜坡早中新世为滨浅海环境,发育生物礁,中中新世至今为半深海沉积环境,斜坡区有水道侵蚀,发育源于台地顶部的重力流沉积,在台地西部的斜坡区还发现了第四纪等深流沉积。综上,将西沙孤立碳酸盐台地发育演化划分为早中新世萌芽期、中中新世繁盛期、晚中新世—上新世淹没期、第四纪现代环礁4个阶段。本次研究弥补了以往对西沙孤立碳酸盐台地发育演化研究的不足。The Yongle Atoll is a typical modern isolated carbonate platform,which has recorded a complete evolutionary history of biological reefs and carbonate platforms in the Xisha Area.Based on the newly acquired high-resolution multi-channel seismic data,combined with the research results of Well CK-2 in the Yongle Atoll and Well XK-1in the east of Yongle Atoll,the sequence stratigraphy of the Yongle Atoll is studied,the evolution of the Atoll discussed,and the evolutionary model for the Xisha isolated carbonate platform established.Based on the change in seismic reflection isophase characteristics,five sequences,i.e.Sq1(Lower Miocene),Sq2(Middle Miocene),Sq3(Upper Miocene),Sq4(Pliocene),and Sq5(Quaternary)were divided from the bottom up,And the chronostratigraphic framework of the Yongle Atoll was established upon the basis.The depositional environment of the platform dominated by lagoons has been relatively stable since Miocene.The platform slope used to be a neritic environment in Early Miocene where biological reefs well developed.It has been a bathyal sedimentary environment since Miocene up to the present.Gravity flow deposits originated from the top of the platform,as Quaternary contour current deposits are also observed on the western slope of the platform.The development and evolution of the isolated carbonate platform in the Xisha may be divided into four stages:initiation in Early Miocene,large-scale carbonate platform growth in Middle Miocene,drowning period in Late Miocene-Pleistocene,and an atoll at present.This study makes up the shortcomings of previous studies on the development and evolution of isolated carbonate platforms in the Xisha Islands.

关 键 词：层序地层 地震相识别 孤立碳酸盐台地 发育模式 永乐环礁 

分 类 号：P736.3[天文地球—海洋地质]