南海北部白云峡谷群富有孔虫砂层沉积特征及发育机制  

Sedimentary Features and Genetic Mechanisms of the Foraminifera-rich Sand Layers in the modern Baiyun Submarine Canyons,Northern South China Sea

作　　者：高胜美 卓海腾 王英民[1,4] 王星星[1] 贾凯育 周伟[5] GAO ShengMei;ZHUO HaiTeng;WANG YingMin;WANG XingXing;JIA KaiYu;ZHOU Wei(University of Petroleum (Beijing),Beijing 102249,China;Key Laboratory of Marine Mineral Resources,Ministry of Natural Resources,Guangzhou,510075,China;CAS Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Guangzhou 510301,China;State Key Laboratory of Petroleum Resources and Prospecting,China;College of Energy,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]浙江大学海洋学院,浙江舟山316021 [2]自然资源部海底矿产重点实验室,广州510075 [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),广州510301 [4]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249 [5]成都理工大学能源学院,成都610059

出　　处：《沉积学报》2019年第4期798-811,共14页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目（41372115）;自然资源部海底矿产重点实验室开放基金项目（KLMMR-2018-B-08）~~

摘　　要：选取南海北部珠江口盆地白云迁移峡谷群中典型陆坡限制型峡谷为研究对象,利用重力活塞样在峡谷头部晚更新世-全新世沉积地层中揭示出了5个泥质砂层,其砂粒成分包括石英、生物碎屑和较高含量的有孔虫。研究发现,这些富有孔虫砂层不仅表现出底部侵蚀、定年倒置等重力流沉积特征,也表现出了明显的牵引流特征,包括:1)累积概率曲线图与C-M图显示砂层中的粗粒沉积物表现出滚动搬运过程;2)滚动和悬浮组分颗粒分选性较好;3)部分位置可见顶、底岩性突变面和双向交错层理。综合以上证据认为,南海活跃的深水底流对先期重力流沉积的改造可能是形成这些砂层的内在机制。同时,结合三维地震揭示的峡谷内沉积物波以及南海现今水流实测数据,认为峡谷内改造沉积物的底流主要来源于活跃的内波内潮作用,而砂层层理厚度的周期性变化与浮游有孔虫的大量富集可能均是该过程的直接体现。Two gravity piston core samples were taken for investigation from a typical Late Pleistocene-Holocene slope-confined canyon in the Baiyun Sag,Pearl River Mouth Basin. Sediment analyses from the core located at the canyon head revealed the presence of five sand layers containing particles of quartz,shell fragments,and abundant foraminifera. Sedimentary features(e.g.,inverted ages and eroded base)showed that the sand in each layer was transported by gravity currents,but other features also revealed the action of traction currents,evident from(1)cumulative frequency diagrams and C-M cross-plots,which showed that the coarse particles were transported by rolling;(2)well-sorted sand particles;and(3)top or basal lithological contacts and bidirectional cross-bedding within some intervals. These sedimentary features,considered together,indicate that the sediments were deposited at the canyon head by gravity current,which itself was possibly modified by active bottom currents in the northern South China Sea.The sediment waves recognized in the canyon,together with in-situ mooring observations,have raised the postulation that the bottom current was caused by the interplay of complex canyon morphology and internal waves and tides,which would have also led to the observed cyclic variation of cross-bedding thickness and the exceptional abundance of planktonic foraminifera. These conclusions increase the knowledge of possible mechanisms of sand sedimentation within the canyon,and have important implications for the prediction of deepwater reservoirs for both hydrocarbons and natural gas hydrate.

关 键 词：珠江口盆地 海底峡谷 重力活塞样 沉积物波 内波 内潮 

分 类 号：P736.21[天文地球—海洋地质] P618.13[天文地球—海洋科学]