南海西沙海域永乐海底峡谷形成演化过程分析

远海孤立碳酸盐台地周缘发育了碳酸盐岩峡谷,对其开展研究有助于深刻理解碳酸盐碎屑沉积物的“源-汇”体系及深水油气成藏等方面。文章利用多波束测深、高分辨率二维多道地震等数据,精细刻画南海西沙海域永乐海底峡谷的地貌形态及内部充填特征,揭示该峡谷沉积演化过程,分析峡谷成因控制因素及稳定性。永乐海底峡谷形成演化可分为萌芽、汇聚和拓展3个阶段,随着演化过程的发展,峡谷规模及对沉积物输运作用增加。永乐海底峡谷形成及演化主要受古地貌隆起形成的负地形和沉积物重力流侵蚀作用影响。峡谷在第四纪以后仍有较明显的活动迹象。分析显示永乐海底峡谷是西北次海盆的重要物质输送通道,其沉积演化过程及稳定性对研究碳酸盐台地沉积物输运等深水沉积过程及岛礁工程建设具有一定参考意义。

Formation and evolution of Yongle Submarine canyon in the Xisha Sea area,South China Sea*

Carbonate canyons are developed around isolated carbonate platforms in offshore environment. The study of these canyons is helpful to understand the “source-to-sink” system of carbonate clastic sediments and deep water hydrocarbon accumulation. Based on the data of multi-beam bathymetric, high-resolution 2D multi-channel seismic profiles, we depicted the geomorphic features and internal filling characteristics of the Yongle Submarine Canyon in the Xisha area, South China Sea. We attempted to reveal the sedimentary evolution process of the canyon, and analyze its genetic controlling factors and stability. The evolution of Yongle Submarine Canyon can be divided into three stages: Embryonic stage, Convergence stage and Expansion stage. The development scale and sediment transportation is increasing with canyon evolution. The formation and evolution of the Yongle Submarine Canyon is mainly affected by the negative topography formed by paleogeomorphic uplift and the erosion of sediment gravity flow. There are still obvious signs of activity of the canyon after the Quaternary. The Yongle Submarine Canyon is an important material transport channel in the Northwest Sub-basin, and the analysis of its sedimentary evolution and stability carry significant implications for the study of deepwater sedimentary processes, such as carbonate platform sediment transport and island construction.