Influence of contour currents on the flow dynamics and deposition patterns of turbidity currents in deep-sea channels

Abstract

Contour currents alter the movement and deposition of turbidity currents, forming a mixed turbidite-contourite system that is essential for the cross-shelf transport of material and energy, as well as the formation and evolution of submarine canyons and channels. However, the specific details of the interaction processes remain unclear due to limited field observations and potential biases in interpretations based on sedimentary results. This numerical study investigates turbidity current-contour currents interactions by analyzing flow dynamics and deposition patterns. Without contour currents, turbidity currents predominantly flow along the channel centerline with minor deviations, exhibiting nearly symmetrical overspill on both sides. The presence of contour currents leads to the coexistence of blocked overspill on the up-current channel side, tractional transport of fine-grained sediments on the down-current channel side, and enhanced Kelvin–Helmholtz (K-H) waves within the channel. The erosion of the down-current channel side is facilitated by the intensified K-H waves, while its deposition is concurrently promoted by the tractional transport of fine-grained sediments. In this simulation, the influence of tractional transport of fine-grained sediments surpasses that of K-H waves, as the calculated additional deposition rate exceeds the additional erosion rate, resulting in an up-current migrating channel. However, variations in parameters of the turbidity currents, contour currents, and topography may allow K-H waves to dominate, potentially leading to a down-current migrating channel. Considering the competition between these two effects, this paper proposes a novel mechanism for the interaction between turbidity currents and contour currents. This offers new insights into the formation of unidirectional migrating channels and provides valuable references for the study of deep-sea canyon geomorphological evolution and hydrocarbon resource exploration.