Influence of bottom currents on morpho-sedimentary features along the northern Argentine margin shows the erosive power of the Malvinas Current

The driving hydrodynamic processes from bottom currents leading to large sediment deposits (contourites) are not entirely understood. The aim of this study is to establish a clearer link between features from Contourite Depositional Systems (CDS) and the oceanographic processes that form them. The current dynamics along the northern Argentine continental margin in proximity to the Mar del Plata submarine Canyon were analysed together with the morphosedimentary characteristics of a large CDS. In this study we combine multibeam bathymetry, sediment echosounder data, seismic reflection data, sediment samples, vessel-mounted Acoustic Doppler Current Profiler (VM-ADCP) data and numerical modelling of ocean currents. Generally, bottom currents follow the upper and middle slope morphology (between 200 and 1400 m water depth). Decreasing velocity of water masses flowing northward leads to less erosion and finer sediment deposits. The CDS includes large contourite terraces (La Plata Terrace, Ewing Terrace) and a large abraded surface between the terraces, as well as smaller features like moats, patchy erosion surfaces on the Ewing Terrace, sediment waves and contourite drifts. Measured and modelled near-bottom currents are vigorous (up to 63 cm/s at 150 - 200 m above the seafloor) where abraded surfaces and moats are present, and relatively weak (below 30 cm/s) on the La Plata Terrace and the Ewing Terrace. Hydrodynamic model and the ADCP data show the formation of cyclonic eddies near the seafloor possibly do to the divergence of isobaths and slightly sloping morphology at the Ewing Terrace. These transient eddies probably led to the small erosion surfaces on the terrace, even though it is mainly a depositional environment. Overall, this study represents a step forward in understanding the formation of CDS.