RESEARCH OF DEEP-WATER SEDIMENT WAVES IN THE SOUTHERN OCEAN

Fine-grained sediment waves formed by deep-water bottom current usually occur on continental slopes or ocean basins. This paper takes some examples from the wavy bedforms occurred at the upper slope of the Great Australian Bight and the southwestern slope of the Conrad Rise. The morphology, distribution pattern and formation mechanisms are discussed. The fine-grained calcareous sediment waves near the shelf-slope break of the Great Australian Bight are oriented parallel to contours in a strip along the shelf-slope break. They are up to 40 m high, 1~2 km wide and 10 km long composed of cool water carbonate oozes. Bryozoans were abundant during the interglacial period, and then moved to the edge of shelf and the upper slope, forming sediment waves under the action of bottom current with a velocity of about 16cm/s. There are some sediment waves developed at the southwestern slope of the Conrad Rise. They are composed of diatom ooze. This is probably due to the high diatom productivity caused by vigorous upwelling of nutrients in the Antarctic Circumpolar Current. Diatoms were abundant for the formation of sediment waves under the action of bottom current, with a velocity about 6 cm/s. The sedimentation rate of the landward flank is higher than the rate on the seaward flank, thus the sediment waves show a pattern of landward migration.