Tectonism, magmatism and sedimentary basin development, Paleozoic to Paleogene, New Caledonia

Abstract

Three pre-Cretaceous basement terranes are recognised in New Caledonia: 1. Karagreu­ Boghen Terrane - an old accretionary complex, metamorphosed to greenschist facies, of uncertain age but probably Early Permian or older and tentatively correlated with Mid-Late Paleozoic complexes of New England Fold Belt. 2. Mt. Canala-Teremba Terrane - arc type volcanics and volcaniclastics of Upper Permian to Early Jurassic age and correlated with the Brook Street Terrane of New Zealand. 3. Ponerihouen-Baie St. Vincent Terrane - volcaniclastic and terrigenous sandstones and argillites of Mid Triassic to Jurassic age and correlated with the Murihiku and Waipapa Terranes of New Zealand. The Karagreu-Boghen and Mt. Canala-Teremba Terranes were probably juxtaposed by the Late Triassic. The three basement terranes were stitched together by late Mesozoic intrusives and Rangitata (Early Cretaceous) metamorphism and deformation. Late Cretaceous-Paleocene extensional sedimentary basins with bimodal volcanism were developed to the N (Diahot Basin) and S (Noumea Basin). The Cretaceous basalts of the Diahot basin are ocean floor type while those of the Noumea Basin are arc type and represent the final extensional stage of Mesozoic subduction. The allochthonous Cretaceous-Eocene West Coast basalts, believed to be New Caledonia Basin ocean floor, are normal MORB-type tholeiites with some arc affinities. The West Caledonian Fault post dates Early Oligocene obduction of the New Caledonian ultramafic sheet and has 55 km of right lateral transcurrent movement. Vertical movement on this fault has also played a major role in Miocene uplift particularly in the north of the island.