Echoes from the Deep

Sediment on the deep ocean floor is commonly divided into three types: turbidites, contourites, and pelagites. Turbidites form from turbidity currents—dense, sediment-laden flows that travel through submarine channels into the deep sea. Contourites are shaped by large-scale ocean currents that move parallel to the continental slope as part of the global ocean circulation. Pelagites result from the slow vertical settling of fine particles from surface waters. These processes were long thought to operate separately. However, growing evidence shows that turbidity currents and contour currents can occur at the same time, creating a combined flow field. This matters because turbidity currents may supply sediment to contourites, which serve as valuable archives for reconstructing Earth’s climate over millions of years. Their interaction may also influence how pollutants such as microplastics are dispersed across the seafloor. Until now, understanding of combined flow systems has relied mainly on studying sediment deposits, without direct measurements of the active flows. This thesis addresses that gap by recreating combined currents in laboratory experiments and computer simulations, allowing detailed three-dimensional measurements. The experimental deposits are compared with natural samples from the Mar del Plata region off Argentina, where both current types interact. The results demonstrate that contour currents alter turbidity currents by enhancing vertical mixing and sideways sediment transport, producing distinctive grain-size patterns. By directly linking flow dynamics to the sediments they create, this research improves the interpretation of deep marine processes and deposits.