Submarine Fans and Their Channels, Levees, and Lobes

Abstract

Submarine fans are complex morphological features that develop on the continental slope, rise and abyssal plain, normally at the mouths of submarine canyons. They are constructed principally from the deposits of sediment gravity flows (mainly turbidity currents and debris flows) as terrigenous and shallow marine sediment is redistributed into deeper water. In this chapter we focus on the most important building blocks of submarine fans: leveed submarine channels and the submarine lobes they feed. Mass transport deposits are also important components of many submarine fans; they are described in the Chapter on “ Submarine Canyons and Gullies”. Submarine channels are the most noticeable geomorphic features on submarine fans, linking net erosional elements like canyons and gullies to net depositional elements like submarine lobes. They develop through both erosional and depositional processes, and have straight to highly sinuous planform geometries. Where they are flanked by aggradational levees or are entrenched into the seabed, they provide stable pathways through which sediment is transported and partitioned into different fan settings. Coarse-grained sediment commonly accumulates on the floors or at the mouths of submarine channels; finer-grained sediment preferentially accumulates on channel banks and on adjacent aggradational levees. In this chapter we describe the wide range of morphological features recognised on the surfaces of submarine fans, and the physical processes that shape the seabed in areas where submarine channels, levees, and lobes develop.