南海北部白云凹陷-东沙岛西南海区的浅地层探测与深水沉积特点  

Characteristics of deep water sedimentation revealed by sub-bottom profiler survey over the Baiyun Sag-Southwest Dongsha Island Waters in the northern South China Sea

作　　者：阎贫[1,2] 王彦林[1] 郑红波[1] 

机构地区：[1]中国科学院边缘海地质重点实验室,中国科学院南海海洋研究所,广东广州510301 [2]中国科学院广州天然气水合物研究中心,广东广州510640

出　　处：《热带海洋学报》2011年第2期115-122,共8页Journal of Tropical Oceanography

基　　金：中国科学院知识创新工程重要方向项目(KZCX2-YW-228);国家自然科学基金项目(U0733003、40876027);国家重点基础研究发展计划项目(2007CB411706)

摘　　要：采用新引进的海洋深水浅层剖面仪,从珠江口外陆架进入白云凹陷-东沙岛西南海区中陆坡区,进行了浅地层探测,获得了高分辨率反射记录。分析发现,白云凹陷上陆坡段沉积连续性较好,海底反射强度侧向变化平缓,显示了比较均一的沉积底质和微弱的海底水动力条件;在白云凹陷-东沙岛西南海区中陆坡区,海底滑坡严重,局部存在强烈的、平行陆坡的海底洋流冲蚀,海底地形崎岖不平,反射强度侧向变化大,表明海底底质不均匀,海底水动力强。浅地层记录还显示中陆坡海底山丘有海底气体泄露现象,结合常规反射地震识别的海底泥底辟特征,确定海底山丘为泥火山。气体泄露和海底反射振幅的变化代表了海底浅层聚有丰富的气体以及嗜甲烷生物链活动的钙化,因而推断该区不仅是油气的聚集区,也是水合物的聚集带。A new sub-bottom profiler with ability for deep water detection was used along survey lines from the outer shelf of Pearl River Mouth to the mid-slope of Baiyun Sag-Southwest Dongsha Island Waters.From the new high resolution data,it is found that the shallow sediments feature good continuity on the smooth upper slope of the Baiyun Sag,which implies ho-mogenous bedrocks and weak current dynamics.Differently,over the mid-slope of Baiyun Sag-Southwest Dongsha Island Waters,there are remarkable phenomena,such as submarine slide-slump,local along-margin current erosive incision,rugged seafloor topography,and contrasted lateral variation of echoed reflection amplitudes,among others,which implies inhomoge-nous bedrocks and strong along-slope local current dynamics over the mid-slope.Additionally,the data show gas seepage within the submarine ridges,which are recognized as mud volcanoes from multiple channel seismic data.The gas seepage and the contrasted reflection amplitudes variation can be ascribed to plentiful gas existed there and calcification by meth-ane-dependent organism;thus,the mid-slope of Baiyun Sag-Southwest Dongsha Island Waters has good prospects in petro-leum and gas hydrates.

关 键 词：白云凹陷-东沙岛西南海区 浅地层剖面 滑坡 气体泄漏 泥火山 

分 类 号：P736[天文地球—海洋地质]