The Chatham Fan (Fig. 1b, c), a relatively small submarine fan, was mapped as part of the University of New Hampshire's Center for Coastal & Ocean Mapping effort to collect multibeam-bathymetric and backscatter data in support of the US Extended Continental Shelf (United Nations Law of the Sea Convention) project (Gardner & Mayer 2005). It has buried a portion of the head of the much larger Baranof Fan (Stevenson & Embley 1987; von Huene 1989; LeVoir et al. 2011) on the US Gulf of Alaska continental margin. Chatham Fan also either buried the upper reaches of Horizon Channel or diverted it northwestwards. The existing levee of upper Horizon Channel was subsequently incised by a well-developed meandering channel that trends along the strike of the levee, not down the steeper lee side of the levee slope. The meandering levee channel is related indirectly to processes that were contemporaneous with the deposition of Chatham Fan.