Rapid rotation of Fiji: Paleomagnetic evidence and tectonic implications

Abstract

The timing and magnitude of rotation of Fiji in relation to the tectonic evolution of the SW Pacific region has been investigated by extensive (126 sites) paleomagnetic sampling of Late Miocene and younger units. Generally, samples yielded well‐defined characteristic remanence directions which indicate that the main Fiji platform rotated by 135±17.5° counterclockwise commencing at, or before, 10 Ma. This very large and rapid rotation ceased abruptly at 3 Ma, coincident with the onset of spreading on the major N‐S aligned spreading centers in the North Fiji Basin. Latest Miocene to Pliocene paleomagnetic results indicate that Viti Levu, the main island itself, has suffered no internal disruption by localized rotations after 5 Ma. We present a reconstruction for the origin of Fiji which differs markedly from previous models such that Fiji, Tonga, and Lau form a continuous N‐S aligned arc and that arc reversal was initiated at or near Fiji itself.