The Central Canyon depositional patterns and filling process in east of Lingshui Depression, Qiongdongnan Basin, northern South China Sea

Abstract

Central canyons are considered to be important conduits for the transfer of sediment to the abyssal plains. High‐resolution 3D seismic data and logging data from the east of Lingshui Depression are used to investigate the depositional elements, patterns, and filling processes of central canyon in the Qiongdongnan Basin, northern South China Sea. The Central Canyon in this segment is 30 km wide and more than 1,000 m deep. It was found to be characterized by being subparallel to the continental shelf. In this study, 6 types of deep‐water gravity flow depositional elements were identified, including erosion surfaces, basal lags, turbidite channel complexes, mass transport deposits, lobe complex, and pelagic deposits. Each type of these depositional elements was found to have distinct external features, internal structures, and lateral characteristics in the seismic profiles. Meanwhile, these different assemblages of depositional elements could be composed of 5 depositional units. And in a vertical direction, the evolutionary history could be divided into 5 stages as follows: (a) a repeated cut and fill stage; (b) high net‐to‐gross channel complex dominated stage; (c) low high net‐to‐gross channel and pelagic shale dominated stage; (d) lobe complex deposition stage; and (e) mass transport deposit dominated stage. During Stage 3, the development of small‐scale turbidite channels is the indicators of northern sediment supply. During Stage 4, 7 lobes have been identified in the lobe complexes. The evolution and depositional processes in the study area were most likely controlled by the negative relief induced by the palaeo‐seafloor morphology, as well as the structural inversions of the Red River Fault and the basement faults. Additionally, the sediment supply, sea‐level fluctuations, and tectonic activities also controlled and influenced the depositional processes, along with the internal architecture of the canyon.The results of this study have potentially important implications for the improved understanding the vertical evolution of submarine canyons and also shed a new light on the reservoir potential of the Lingshui section of the Central Canyon.