南海西北部晚第四纪典型地震相—沉积相特征

TYPICAL SEISMIC AND SEDIMENTARY FACIES OF THE LATE QUATERNARY IN THE NORTHWESTERN SOUTH CHINA SEA

南海西北部地形变化大,水深由近岸几十米变化至深海盆区的3 500m,跨越了陆架、陆坡、深海盆、岛礁等地貌单元。南海西北部也是深水油气的重要勘探地区。利用高分辨率单道地震资料,采用地震相分析方法,对研究区晚第四纪典型地震相—沉积相分布特征开展深入分析。研究区内的主要地震相包括:①席状、亚平行、强振幅、低连续、中频地震相;②披盖状、波状、中振幅、中—低连续、中低频地震相;③披盖状、平行—亚平行、中—弱振幅、中连续、中—低频地震相;④披盖状、平行、强振幅、高连续、中—高频地震相;⑤席状、平行、中—弱振幅、高连续、中—低频地震相;⑥披盖状、波状、弱振幅、低连续、低频地震相;⑦前积相;⑧下切充填地震相;⑨杂乱地震相;⑩条带状、波状、中—弱振幅、中—低连续、低频地震相;瑏瑡披盖状、平行、强振幅、高频、高连续地震相共11种。对地震相—沉积相及其分布特征的分析结果认为,区内晚第四纪主要发育有三角洲相、河道相、滨浅海相、浅海相、半深海相、深海相、滑塌相、斜坡相、浊流相、生物礁相等沉积相,其分布主要受海底地形地貌、构造运动等多种因素所控制。

The water depth of the northwestrn South China Sea varies from tens of meters at the near shore area up to 3500m in the deep sea basin.Geomorphologically,the study area includes shelf,slope,oceanic basin and reefs,and the sedimentary environments are quite complicated.Detailed analysis of the seismic and sedimentary faices of the Late Quaternary in the study area have been carried out base on thousands of kilometers of high resolution single-channel seismic profiles.There are a total of 11 types of seismic facies distributed including the delta,paleo-river,erosional channel by turbidity current,offshore deposit,shallow sea deposit,hemipelagic deposit,pelagic deposit,slide body,deep slope deposit and carbonate platform.Further research shows that the distribution of different sedimentary facies is controlled by the bathymetry,geomorphology,and tectonic movement in the study area.