Direct in situ evidence of tidal roles in the formation of contourite depositional systems

Tidal currents are ubiquitous in the oceans, but the role of these currents in contributing to form contourite depositional systems is poorly understood. Here we evaluated the significance of these currents in the formation and shaping of the contourite depositional systems. We examined in situ current data, spanning three months to one year, from four contourite sites at the exit of the Strait of Gibraltar, the northern North Atlantic Ocean, the Pacific margin of the Antarctic Peninsula, and the Lake Champlain. These current data indicate that tidal currents contribute to varying degrees to the formation of contourite erosional and depositional features, depending on the relative strengths of local tidal currents and background water mass circulation. Tidal currents enhance sediment resuspension in moats and channels, and encourage deposition on drifts, thereby promoting the development of contourite depositional systems. Baroclinic (internal) tidal currents are likely the dominant agent. Our findings indicate that tidal influences, especially those of internal tides, need to be considered in studies of the generation and evolution of contourite depositional systems.