A POSSIBLE TRIPLE JUNCTION AT 14-DEGREES-50'S ON THE NORTH FIJI BASIN RIDGE (SOUTHWEST PACIFIC)

Recent full coverage bathymetric and geophysical surveys (Yokosuka 90 and 91), carried out in the framework of the STARMER Japanese-French joint project, reveal details of the structure of the N160-degrees segment of the North Fiji Basin Ridge. Despite its intermediate spreading rate this segment shows a ''slow spreading'' type morphology with steep 1000 m high walls reaching an axial depth of 4000 m. Its northern tip at 14-degrees-50'S is a complex area involving several plates boundaries. This domain can be interpreted either as a complex boundary between two plates, or as a new triple junction, symmetrical with the 16-degrees-50'S Triple Junction characterizing its southern tip. In either case, the complexity of the spreading ridge geometry in this area illustrates the instability of the accretionary geometry due to the deformation of the whole North Fiji Basin between the much larger Indo-Australian and Pacific plates.