南海东沙海域树枝型峡谷体系形成演化对拉张构造作用的响应

由分支峡谷与主干峡谷共同构成的树枝型峡谷体系是大陆边缘重要的物质搬运系统，明确其形成演化过程对于陆缘“源—汇”过程中沉积物通量的准确评价十分关键。然而，目前针对拉张构造背景下树枝型峡谷体系形成演化机制的研究不足。受新构造运动影响，南海东沙海域自中中新世以来处于拉张构造背景。本项目以东沙海域树枝型峡谷体系为研究对象，利用高分辨率二维多道地震和多波束测深数据，开展地震地层学、构造地质学和沉积学研究，明确中中新世以来峡谷体系地貌特征和主要沉积过程的时空差异及内在联系，掌握研究区拉张构造变形的空间展布及活动演化，构建峡谷体系与拉张构造作用之间的时空匹配关系，阐明峡谷体系中分支与主干峡谷的协同演化过程及其对拉张构造作用的响应方式，最终揭示东沙海域树枝型峡谷体系对拉张构造作用的响应机制。研究成果有助于完善树枝型峡谷体系的形成演化机制，为进一步开展拉张构造背景下陆缘“源—汇”过程定量研究提供重要支撑。

Dendritic canyon system is an important kind of material-delivering system at continental margin, which is consisted of mainstems and tributaries. A good understanding on the formation and evolution of dendritic canyon system is critical for accurately evaluating the sediment budget in source-to-sink processes at continental margin. However, it remains unclear about the formation and evolution of the dendritic canyon system in extensional tectonic settings. Influenced by neotectonics, the dendritic canyon system in the Dongsha Region, South China Sea, has begun to develop in the extensional tectonic setting since the middle Miocene. By utilizing the high-resolution multi-channel seismic data and bathymetry, this study will conduct researches on the formation and evolution of the dendritic canyon system in the Dongsha Region, South China Sea, through the integrated analyses including seismic stratigraphy, structure geology and sedimentology. The results will show the spatial and temporal differences and relationships in morphological features and the dominated sedimentary processes of the canyon system since the middle Miocene, and also display the major spatial distribution and temporal evolution of the extensional structures in the study area. Based on these results, this study will further establish the coupling relationships between the canyon system and extensional tectonics, which will be used to illuminate how the mainstems and tributaries of the dendritic canyon system evolve synchronously and respond to extensional tectonics. Finally, this study will reveal the response mechanism of the formation and evolution of the dendritic canyon system to extensional tectonics in the Dongsha Region, South China Sea. This study would improve the mechanism on the formation and evolution of dendritic canyon system, providing an important basis for quantitative researches on source-to-sink processes in extensional tectonic settings in future.