The depositional characteristics of turbidity currents in submarine sinuous channels

Abstract

Submarine channels with meandering patterns and extensive levee complexes are commonly found on continental slopes and fans. Here, a three-dimensional numerical model is applied to conduct a systematic study of poorly-sorted depositional turbidity currents in sinuous submarine channels with different side slope and sinuosity. Multiple runs with the same inflow conditions are made to study deposition patterns inside the channel and levees. Not only many known facts, such as the spilling and stripping of turbidity currents at channel bends as well as the different pattern of deposition at the inner and outer banks of channel bends, are produced, but also some important new findings, such as: i) small river-like circulation near the bottom corner of outer bank co-exists with predominant lateral convection as secondary flow; ii) the levee on the outer bank of a channel bend apex of steeper lateral slope shows larger variation in grain size distribution than the thinner, more smooth levee on its opposite side; iii) the levees at bend inflections inherit the characteristics of the upstream levees at channel bend apexes; iv) the downstream cross-section that cuts both sinuous channel beds and banks is characterized by thicker channel bed deposits intersected by arch-shaped thinner on-bank deposits; v) the levee deposit displays an asymmetric wave pattern in the downstream direction, and the flow direction is from the short rising side to the long dropping side. The flow and sedimentation patterns summarized in this study may promote the understanding of physical processes of submarine turbidity currents and their depositions and assist in interpreting seismic, outcrop and/or borehole data for reconstruction of original depositional environment.