The D'Entrecasteaux Zone (Southwest Pacific) is an arched submarine horst- and graben structure, which extends from the northern end of the New Caledonia ridge to the western border of the New Hebrides island arc. A review of the bathymetry, seismic-reflection data, paleomagnetism, gravimetry, seismology and DSDP data available for this area is combined with a study of basaltic samples dredged along the horsts of this regional fracture zone. Their fissiontrack ages range between 56 Ma (Paleocene-Eocene boundary) and 36 Ma (Eocene-Oligocene boundary). It is suggested that the D'Entrecastreaux Zone represents the northern arcurate extension of the northeast-dipping Eocene subduction/obduction zone, located along the New Caledonia/Loyalty Islands ridge, while its present morphology appeared from post-obductionextensional movements, resulting in a progressive uplift of basaltic ocean floor since Middle Miocene times.