西沙海域中中新世早期古地貌及其控制因素  

PALEOGEOMORPHOLOGY OF EARLY MIDDLE MIOCENE IN THE XISHA SEA AREA AND ITS CONTROL FACTORS

作　　者：杨振[1,2] 张光学[2] 张莉[2] 夏斌[1] 

机构地区：[1]中山大学海洋学院,广州519082 [2]国土资源部海底矿产资源重点实验室广州海洋地质调查局,广州510075

出　　处：《海洋地质与第四纪地质》2016年第3期47-57,共11页Marine Geology & Quaternary Geology

基　　金：国家专项"南海北部陆坡及台湾海峡盆地西部油气地质特征与赋存规律研究"(GZH20120511);国家自然科学重点基金项目(91228208)

摘　　要：古地貌的构造格局控制了物源体系和沉积体系的发育,对其研究有利于确定油气勘探目标。基于西沙海域丰富的地震资料、钻井资料以及高精度的多波束资料,重点经过去压实校正和古水深校正之后,恢复西沙海域中中新世早期的古地貌。该时期的古地貌显示:西沙海域以两个近北东向的西沙、广乐隆起为纽带串联周缘的深水区域,西沙隆起和广乐隆起之上水体较浅,处于滨海环境,利于碳酸盐岩的沉积。西沙隆起之上岛屿众多,岛屿之间以洼地相隔,为需要地势高点生长的生物礁的发育创造了条件,西沙隆起南部于渐新世发育大量的火山,后期多演化为孤立的台地,隆起周缘多以陡坡为主。而广乐隆起之上地势开阔、平坦,隆起南、北两侧的斜坡有一定的差异,具有"南陡、北缓"的特点,其北部斜坡地貌复杂,发育至少三组近平行的水道,利于碳酸盐岩碎屑的搬运和沉积,活跃于渐新世的断裂控制古地貌的空间格局,同时,生物礁碳酸盐岩的发育以及其碎屑的搬运和沉积作用对地貌的不断改造,造就了该时期的地貌形态。The study of tectonic paleogeomorphology,which controls the sediment sources and depositional system,is helpful to oil and gas exploration.Based on the abundant seismic,wells and high-resolution multi-beam data we have in hand so far,the early Middle Miocene paleogeomorphology in the Xisha Sea Area is recovered in this paper,in particular,after the treatment of decompaction and palaeobathymetric correction.Results show that in early Middle Miocene,there were two nearly northeast-trending uplifts surrounded by deep water areas in this region.The uplifts were favorable for development of shallow water carbonate platforms.Volcanism was active in the Oligocene leaving aquantity of topographic highs on the Xisha Uplift,which provided opportunities for the growth of reefs.With the sea level rise,many volcanoes to the south of this Uplift also evolved into small isolated carbonate platforms and the slopes around the Xisha Uplift were usually very steep.However,the terrain on the Guangle Uplift was very broad and flat,and its slopes were characterized by the framework of'steep in south and smooth in north'.The northern slope was rather complicated,where exist at least three roughly parallel channels which were favorable for transportation and deposit of carbonate clasts.There are two main controlling factors on the paleogeomorphology in the area in early Middle Miocene,i.e.tectonic movement and sedimentation,including the simultaneous faulting in Oligocene,the development of reef and carbonate platform,and the transport and deposition of carbonate clasts.

关 键 词：古地貌 控制因素 中中新世早期 西沙海域 

分 类 号：P618.13[天文地球—矿床学] P534.621[天文地球—地质学]