Magnitude and timing of New Hebrides Arc rotation: Paleomagnetic evidence from Nendo, Solomon Islands

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Paleomagnetic results from Nendo record a total rotation of the northwestern corner of the New Hebrides Arc of 52° ± 12° clockwise. Reversed magnetic polarity and a nannofossil assemblage constrain the age of the Nendo pole to 4.29 ‐ 3.58 Ma. Paleomagnetic data from Malekula, farther south in the same arc, imply a rotation of only about 28° since the late Miocene, probably because these poles have been affected by rotation of Malekula in response to collision of the arc with the D'Entrecasteaux Zone aseismic ridge. A new late Miocene reconstruction of the New Hebrides and Vitiaz arcs based on the paleomagnetic evidence requires a rotation of 39° around the point of intersection of the two arcs. The same rotation restores both the northwestern and southeastern segments of the New Hebrides Arc, although rotation of the southeastern segment commenced earlier. A series of sequential movements of segments of the arc, occurring at different times but acting to keep the arc roughly collinear, may be driven by a mechanism which minimizes deformation of the subducted plate. Propagation of spreading into the northwestern corner of the North Fiji Basin after 4.3 Ma is implied by the paleomagnetic results, and is consistent with spreading anomaly patterns in the basin. When the New Hebrides and Vitiaz Arcs are restored to their position relative to the Lau Ridge at 10 Ma, the Fiji Platform can be accommodated after clockwise rotation of 140°, to a position in line with the New Hebrides Arc. The large rotation for Fiji is consistent with paleomagnetic evidence indicating at least 115° of rotation.