U-shaped slope gully systems and sediment waves on the passive margin of Gabon (West Africa)

► U-shaped slope gullies associated with sediment waves are discovered offshore Gabon. ► The gullies display both aggradational and erosional morphologies. ► Gullies occur at the modern seabed and buried in Pleistocene-Holocene sediments. ► Sheet-like, fine-grained turbidity currents can form both gullies and sediment waves. ► Perturbation in cross-flow direction of wide turbidity currents may form gullies.