INTERPRETATION OF GLORIA SIDE-SCAN SONAR IMAGERY FOR THE CORIOLIS TROUGHS OF THE NEW-HEBRIDES BACKARC

The Coriolis backarc troughs in southern Vanuatu are elongate, rhomboi dal depressions with steep walls and flat floors, formed by extension. The Futuna Trough is relatively immature and, like Erromango Basin, s hows no recent volcanism. Vate Trough is most developed, and its floor is largely covered by lava fields. Between Vate and Banks Islands, th e backarc has three distinct characters: in the south it is sediment-d raped; centrally, either lava projects through sediment cover or the a rea is covered by slide debris; in the north, a steep escarpment may r esult from collision of the arc with the D'Entrecasteaux Ridge.