The Loyalty—New Hebrides Arc collision: Effects on the Loyalty Ridge and basin system, Southwest Pacific (first results of the ZoNéCo programme)

The ZoNeCo 1 and 2 cruises of IFREMER's Research Vessel L'Atalante, collected new swath bathymetry and geophysical data over the southern and northern segments of the basins and ridges forming the Loyalty system. Between the two surveyed areas, previous studies found evidence for the resistance of the Loyalty Ridge to subduction beneath the New Hebrides Trench near 22 degree S-169 degree E. On the subducted plate, except for seismicity related to the down-bending of the Australian Plate, recorded shallow seismicity is sparse within the Loyalty system (Ridge and Basin) where reliable focal mechanism solutions are almost absent. Swath bathymetry, seismic reflection and magnetic data acquired during the ZoNeCo 1 and 2 cruises revealed a transverse asymmetric morphology in the Loyalty system, and an along-strike horst and graben structure on the discontinuous Loyalty Ridge.