Autochthonous rocks of the bounty islands region, south-west Pacific ocean

Abstract

The Bounty Islands lie in the south-west Pacific, about 850 km east of southernmost New Zealand, and close to the eastern margin of the submerged quasicontinental crustal segment known as the Campbell Plateau. The islands themselves consist of coarse granodiorite, but autochthonous rocks dredged from the adjacent sea floor include quartz-feldspar porphyries, dioritic intrusives, and sedimentary rocks of greywacke facies. The granodiorites have been radiometrically dated as early Jurassic; the acidic and intermediate intrusives are presumably either syngenetic or younger. The greywackes are petrographically comparable with rocks of late Precambrian (?)-early Paleozoic age on the New Zealand mainland. The occurrence of a very similar assemblage of igneous and sedimentary rocks in Marie Byrd Land favours the supposed original proximity of Campbell Plateau and westernmost West Antarctica.