The New Caledonia–D’Entrecasteaux orocline and its role in clockwise rotation of the Vanuatu–New Hebrides Arc and formation of the North Fiji Basin
Stephen T Johnston, 2004. "The New Caledonia–D’Entrecasteaux orocline and its role in clockwise rotation of the Vanuatu–New Hebrides Arc and formation of the North Fiji Basin", Orogenic curvature: Integrating paleomagnetic and structural analyses, Aviva J. Sussman, Arlo B. Weil
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The origin of map-view bends of orogenic belts and arcs remains enigmatic. Here I summarize geological evidence indicating that a bend of the northern end of a ribbon continent extending north from the Northland Peninsula, New Zealand, through New Caledonia and the Loyalty Islands and into the submarine d’Entrecasteaux ridge (the NNNCd’E ribbon continent) is an orocline that has formed as a result of oroclinal orogeny (buckling about vertical axes of rotation due to pinning of the leading edge of a migrating lithospheric beam). An analogue model is used to investigate the geometric relationship between orocline development, the rotation of the Vanuatu–New Hebrides arc, and the origin of the North Fiji basin.
The NNNCd’E ribbon continent terminates to the northeast in the Vanuatu–New Hebrides arc. The asymmetric, triangular, northwest-tapering North Fiji lies northeast of (behind) the arc. Paleomagnetic, geological, and geodetic data imply that since 10 Ma the Vanuatu–New Hebrides arc has rotated ~60° clockwise about a pole of rotation located at its northwest end, opening the North Fiji basin. The analogue model demonstrates that the arc was forced to rotate clockwise due to its southward advance being impeded by the NNNCd’E ribbon continent. In this model, the ribbon continent originated as a linear, north-trending feature that ended in the arc, just west of its midpoint. Southward advance of the arc buckled the ribbon continent, giving rise to the orocline. Buckling forced the arc to rotate clockwise, opening the asymmetric North Fiji basin. The lithospheric-scale of buckling is consistent with orocline formation controlling the clockwise rotation of the Vanuatu–New Hebrides arc and formation of the North Fiji basin.
Buckling of the NNNCd’E ribbon continent against the migrating Vanuatu–New Hebrides arc explains the curved ribbon continent, the clockwise rotation of the arc, and the origin of the North Fiji basin. This ongoing oroclinal orogeny provides us with an opportunity to further understand the processes responsible for and involved in the buckling of lithospheric beams and to refine interpretations of ancient orogens that are thought to be the products of oroclinal orogeny.