Depositional Architecture and Evolution of Deepwater Fan System in the Northwestern Sub-Basin, South China Sea

Key words: 
• deepwater fan system /
• Qiongdongnan center canyon-channel /
• the northwest sub-basin /
• Northern South China Sea

Abstract: Based on the existing high-resolution 2D seismic data, we identified a large deep-water fan system in the Northwest sub-basin, the abyssal plain of northern South China Sea. The results show a canyon-channel transition zone with channel avulsions in the upper fan, channel-levee systems in the middle fan and channel-lobe systems in the lower fan. The Qiongdongnan Center canyon-channel is considered as the main sediment supply system, with sediments mainly from the Red River and Indochina, northern shelf and slope, and Zhongsha and Xisha uplift regions. A combination of the pre-existing topography and sediment supply strength appears to have a control on the temperospatial distribution of the deep-water fan system. Geographically the fan system is divided into north and south parts by the Shuangfeng seamount, and geologically I to V sub-fans can be identified, respectively corresponding to the late Miocene (I), Pliocene (II and III), and Quaternary (IV and V).The early-deposited sub-fans altered the topography, while strong sediment supplies improved the overflow frequency, with obvious lateral migration in individual fans. The "three step" continental slope of northern South China Sea affected the development and evolution of deepwater fan systems.