Interactions between internal tides and turbidity currents: an under-recognized process in deep-marine stratigraphy?

Deep-sea currents transfer sediment, nutrients, and pollutants, which drive climatic, ecological and geomorphological variation in the global ocean. The complex interaction of downslope currents and internal tides in submarine canyons has meant that interpreting their stratigraphic record and therefore reconstructing oceanic environments through geological time has proven challenging. We integrate flow measurements with sediment core observations from the Whittard Canyon, to determine whether the stratigraphic signature of turbidity current and internal tide interaction is preserved. Sand is transported by turbidity currents and re-worked by internal tides, forming a suite of characteristic deposits; near-bed flow measurements show that turbidity currents superposed on internal tides collectively exceed a critical bed shear stress for mobilizing fine sand at least 1% of a year, suspending sediment tens of meters above the bed over longer periods. Using these observations, we present a framework to recognize this interaction in the stratigraphic record.