Submarine channels ‘swept’ downstream after bend cutoff in salt basins

Abstract

Channel-bend expansion and downstream translation, as well as vertical movements by aggradation and incision, set the stratigraphic architecture of channelized depositional systems. Early work on submarine-channel evolution has suggested that downstream translation is rare. It is proposed here that downstream translation of bends might be common in deep-water salt-tectonic provinces, where complex topography can localize channel pathways that promote meander cutoffs and the generation of high-curvature bends. Three-dimensional seismic-reflection data from a region with salt-influenced topography in the Campos Basin, offshore Brazil, is used to characterize the structural geometry of a salt diapir and stratigraphic architecture of an adjacent submarine-channel system that extends for 18 km. The combined structural and stratigraphic evolution is interpreted, including meander-cutoff development near the salt diapir followed by ~10 km of downstream translation of a channel bend. The stratigraphic evolution is tested with a simple numerical model of channel meandering. This integrated subsurface characterization and stratigraphic modelling study sheds light on the processes and controls of submarine-channel downstream translation, which might be common in rapidly deforming settings, such as salt basins, that promote localized subsidence, meander cutoffs, and rapidly translating, high-curvature bends.