Carbonate mounds are very steep-sided mounds of variety of shapes, which may be up to 350 m high and 2 km wide at their base (Weering et al, 2003). They occur offshore in water depths of 500 m-1100 m with examples present in the Porcupine Seabight and Rockall Trough (Kenyon et al, 2003). Carbonate mounds may have a sediment veneer, typically composed of carbonate sands, muds and silts. The cold-water reef-building corals Lophelia pertusa and Madrepora oculata, as well as echiuran worms are characteristic fauna of carbonate mounds. Where cold-water corals (such as Lophelia) are present on the mound summit, coral debris may form a significant component of the overlying substratum. There is currently speculation on the origin of carbonate mounds, with possible associations with fault-controlled methane seepage from deep hydrocarbon reservoirs, or gas-hydrate dissociation (Henriet et al, 1998) through to the debris from ‘cold-water’ coral colonies such as Lophelia.