OCEANIA (INCLUDING FIJI, PNG AND SOLOMONS) 115 Figure Geological map of Vanuatu, including the Santa Cruz Group in the Solomon Islands (the dashed line marks the international border) The map shows the active Vanuatu trench, the western belt Islands of Late Oligocene to Middle Miocene volcanics, the eastern belt (Maewo and Pentecost Islands) of Late Miocene to Early Miocene volcanic rocks, and the central chain of Late Miocene to Holocene volcanoes Ultramafic and metamorphic rocks (dating to 35 Ma) are exposed on southern Pentecost Island Map drawn by L Cotterall, Geology Department, Auckland University Vanuatu The islands of the Vanuatu archipelago (Figure 5) form a narrow chain that extends for more than 1200 km, from the Torres Islands in the north to Matthew and Hunter islands in the south The island chain is bounded eastward by the North Fiji Basin and westward by the Vanuatu Trench The islands are, with one exception, entirely volcanic in origin, with associated sediments and intrusive rocks The exception is on southern Pentecost Island, where ultramafic rocks associated with blocks of schistose amphibolite, metamorphosed pillow lava, and metagabbro are in