a, Major features and tributaries of the Ganges–Brahmaputra drainage basin. The background topographic image is from GeoMapApp (http://www.geomapapp.org). b, Morphology of the Bengal Fan. Sediment is dominantly delivered via turbidity currents that travel along the single-channel channel-levee system. Red circles show sediment cores used here. c, A Parasound seismic-reflection profile crossing cores SO93-117KL and SO93-120KL from west to east. The upper left inset shows locations of the profile and cores with respect to the pathway of the active channel, imaged by multibeam bathymetry. The upper right inset shows Parasound data around core SO93-118 KL. Figure parts are modified from ref. 6, and details of the sediment fan system are described in ref. 55.