南海北部东沙海底峡谷沉积演化过程及其地质意义

为揭示南海北部东沙海底峡谷沉积演化及其资源效应，利用高分辨率二维多道地震与多波束测深数据，对该峡谷中-上游段的沉积层序、地貌特征及沉积构型展开剖析.东沙海底峡谷上游段表现为6个分支峡谷，中游段则汇聚为2条主峡谷，峡谷头部广泛发育分支水道.峡谷中游段于早中新世晚期开始发育，处于岩浆岩体和构造凸起之间；上游段分支峡谷形成于晚中新世以来，其与峡谷头部分支水道的形成分别受断裂体系和底流作用影响较大.东沙海底峡谷演化分为3个阶段:(1)早中新世晚期-中中新世，峡谷初始发育阶段；(2)晚中新世，峡谷拓展阶段；(3)上新世以来，现代峡谷发育阶段.东沙海底峡谷向马尼拉海沟提供了充足的富有机质沉积物，构成了马尼拉海沟增生楔天然气水合物形成的重要物质基础. 

Sedimentary Evolution and Geological Significance of the Dongsha Submarine Canyon in the Northern South China Sea

Based on high-resolution 2D multiple channel seismic data and multiple beams, this study investigated the sedimentary sequence, morphological features and depositional architectures of the Dongsha submarine canyon (DSC), to reveal the sedimentary evolution of the DSC and its geological significance in resources exploration. The results show that the upper segment of the DSC consists of six branches with widespread dendritic channels around the canyon heads, which have merged into two main branches at the middle segment. The middle segment of the DSC was initially formed at the late Early Miocene, when the canyon was confined between the tectonic uplift and igneous body. The upper segment of the DSC has begun to extend landwards since the Late Miocene; the formation of the upper-segment branches and dendritic channels at the canyon heads was significantly influenced by faults and strong bottom currents, respectively. The evolution of the DSC could be divided into three stages: (1) The initial development stage from late Early Miocene-Middle Miocene, (2) the expansion stage in Late Miocene, and (3) the modern development stage from Pliocene-present. Since the Late Miocene, the DSC has provided Manila trench with a great amount of organic-rich sediments, which are important materials for producing gas hydrates in the accretionary wedge of the Manila subduction zone.