Cruise MUSORSTOM 6 


12th-26th February 1989



Abstract

The MUSORSTOM 6 cruise took place from 12 to 26 February 1989, on the Loyalty Islands Ridge. This ridge, situated on the edge of the New Hebrides Trench, is an extension of the Norfolk Ridge, and is separated from New Caledonia by the Loyalty Islands Trench, which is more than 2000 m deep. On the Ridge itself lie scattered coral formations, built on volcanic substrata. Running from North-West to South-East are: Astrolabe Reef, Beautemps-Beaupré Atoll, Ouvéa Atoll, Lifou Island, Maré Island, Durand Reef, Walpole Island and Orne Bank.
The camber of the Ridge resulting from the meeting of the two plates has caused the uplift of the islands and an East-West slope. Thus the reefs of Walpole Island rise to more than 75 m high, those of Maré to 138 m, Lifou to 60 m, and the atoll of Ouvéa is raised only on the eastern coast (46 m).
In the course of MUSORSTOM 6, R.V. "Alis" carried out 102 operations between Beautemps-Beaupré and Maré: 78 with a Warén dredge, 18 with a beam trawl, 2 with a Charcot dredge, 3 lines of traps were laid, and one shrimp trawl shot.
The sea-bed of the upper bathyal zone (200-1000 m) is very bumpy and rocky and there are few areas that can be dredged.
The most interesting collections made during the MUSORSTOM 6 Cruise were some Gymnocrinus with a very long peduncle, found on a sea-mount East of Tiga Island, and a small black crinoid belonging to the Holopidae family which had never before been reported in the Pacific Ocean although known in the Caribbean and the Azores.

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