The Guajira contourite depositional system along the northern Colombian Caribbean convergent margin

Bottom currents have a significant role in the transport, erosion and deposition of sediments. They also have the power to modify the seabed morphology. Contourite depositional systems have been reported worldwide, mainly in passive margins; with few examples reported at convergent margins. This study uses regional multibeam bathymetry and seismic data, to document for the first time a∼20,000 km² slope contourite depositional system along the upper continental slope of the northern Colombian Caribbean convergent margin. We compare the characteristics of the slope geomorphology with hydrodynamic modeling of the bottom currents. We identified on the upper slope, close to the shelf edge, the presence of erosional terraces and moats over an area of∼2,700 km². Near this sector, the modelled ocean currents can reach speeds of up to∼10 cm/s. However, the bottom currents have a high degree of variability, and low values of∼1 cm/s are also identified over the terraces; this may suggest that erosion can occur when the currents reach their highest speeds of circulation. Therefore, the erosion is neither homogeneous nor continuous along the slope. On the other hand, the plastered drift and sediment wave fields related to sediment accumulation have low current velocities between∼1 - 5 cm/s, and they cover a large area of the upper slope (∼17,600 km²), suggesting that sediment accumulation may occur in areas where bottom currents have low velocities. The plastered drift thickness also shows high variability in the study area. The major thicknesses of∼785 ms (or ± 800 m) are related to a gentle slope topography (<2°). In contrast, the lowest thicknesses of∼300 ms (or ± 300 m) are identified in areas with steep slope topography (>2–5°), indicating that in gently slope topography (<2°) plastered drift deposits have a greater thickness. This work allows us to characterize for the first time a regional slope contourite depositional system along the northern Colombian Caribbean margin and highlights the influence of bottom current strength and slope gradient topography in controlling the erosion and preferential accumulation of sediments in an active margin with low sediment supply. This mode of occurrence may be characteristic of contourite depositional system development on convergent margins with low fluvial sediment discharge worldwide.