Submarine fans – Fans are “a relatively smooth, fan-like, depositional feature normally sloping away from the outer termination of a canyon or canyon system” (IHO, 2008). Since submarine fans are sediment deposits, the NGDC map of global ocean sediment thickness (Divins, 2003) was used to assist with identifying them. Fans overlay and comprise part of the continental rise and are located offshore from the base of the continental slope (Curray et al., 2002; Dowdeswell et al., 2008; Covault et al., 2011).
Sediment transported down submarine canyons is deposited to form submarine fans at the mouth of the canyon where the seabed flattens out adjacent to the deep ocean floor. Submarine fans and other sediment deposits, located at the foot of the continental slope especially along passive continental margins, accumulate over time to form a gently-dipping ramp composed of land-derived sediment (Walker, 1992). Currents flowing along the foot of the slope (referred to as contour currents because they flow parallel to an isobath-contour line) can transport the sediments delivered by canyons along-slope to form large sediment drifts. Hence, fans are inter-related with submarine canyons and sediment drift deposits; in cases where canyon axes extend across the rise, the canyon-channels may be flanked by sediment drift deposits, which have been grouped with fans in this study.