Depositional evolution of the confined submarine fan within the Central Canyon in the Qiongdongnan Basin and their main controlling factors

Based on the well data and high-resolution 3D seismic data, as well as numerical simulation, we find that the confined submarine fan within the Central Canyon consists of two fan bodies connected by the turbidite channels. Depositional evolution of turbidity flows forming the submarine fan was severely influenced by the paleotopography. Turbidity flows accelerated within the first slope and mainly bypassed. They decelerated abruptly when they flowed into the first step and hydraulic jump occurred. Therefore turbidity flows spilled out of the turbidite channel to form the fan body 1. The fast deposition of turbidity flows is probably responsible for the poor sorting of turbidite sandstones within the fan body 1. Noting that turbidity flows accelerated slightly in the second slope and mainly bypassed. Finally, they flowed into the second step and slowed down gradually to form the fan body 2. Within the fan body 1, the late turbidite channel migrated at least 5km southeastward resulting from the gentle topography. Additionally, the late turbidite channel extended forward for tens of kilometers compared to the early turbidite channel. This is attributed to the enhanced sediment supply resulting from the sea level falling. Overall, variations of the topography and sediment supply are the main controlling factors for the depositional evolution of the confined submarine fan. Future researches should pay more attention to these factors.