Deepwater Canyons Reworked by Bottom Currents: Sedimentary Evolution and Genetic Model

Based on multi-beam bathymetric data and 2D high-resolution, multi-channel seismic profiles, combing ODP1148 drilling data, the morphology, internal sedimentary architecture, and evolution pattern of 17 deepwater canyons from the Middle Miocene to present are documented in the northern Baiyun sag (BS), Pearl River Mouth basin (PRMB), and northern South China Sea (SCS). There exist six seismic architectural elements in these canyons, including basal erosive surfaces (BES), thalweg deposits (TD), lateral migration packages (LMP), mass transport deposits (MTD), canyon margin deposits (CMD), and drape deposits (DD). According to the stratigraphical ages and geometrical features of these canyons, their formation and evolution processes are divided into three stages: (1) Middle Miocene scouring-filling, (2) Late Miocene lateral migration, and (3) Pliocene-Quaternary vertical overlay. An auto-cyclic progressive in the scouring-filling and vertical overlay; process of eroding and filling by turbidity currents results bottom currents are responsible for the remarkable asymmetry between the two flanks of canyons; and faults are inherent dynamic forces triggering these can yons. It is inferred that these canyons are caused by the double effects of turbidity and bottom currents under the control of faults as inherent dynamic forces.