Cold-water coral reefs and glacial landforms from Sula Reef, mid-Norwegian shelf

Abstract

Cold-water coral reefs are commonly found associated with positive-relief glacial and other geological landforms such as shelf breaks, bedrock ridges and submarine slide terrains. Such reefs are generally restricted to ocean water temperatures of 4–12°C and water depths of 50–1000 m. Cold-water corals include stony corals (Scleractinia, including Lophelia pertusa ), soft corals (Octocorallia, including ‘precious’ corals, gorgonian sea fans and bamboo corals), black corals (Antipatharia) and hydrocorals (Stylasteridae) (Roberts et al. 2006). The coral Lophelia pertusa , which constitutes an important part of the cold-water coral reefs found in Norwegian waters, requires a hard bottom substrate for settlement, and growth is favoured in areas of relatively strong currents (Dons 1944; Mortensen et al. 2001). Glacial landforms such as iceberg ploughmarks, moraine ridges and streamlined glacial landforms (drumlins and mega-scale glacial lineations or MSGLs) can provide an elevated position relative to the surrounding seafloor, giving exposure to enhanced currents, and sometimes a relatively hard bottom substrate through consolidation and the winnowing of fines. The Sula Reef is located on the ENE–WSW-trending Sula Ridge on the mid-Norwegian continental shelf (Fig. 1a, e). The ridge is about 20 km long and up to 50 m high (Fig. 1a); ridge height decreases towards the NE. The Sula Ridge is made up of layered, resistant sedimentary rocks, with Quaternary glacial to Holocene hemipelagic acoustically laminated …