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.