A Revised Cretaceous-Cenozoic Apparent Polar Wander Path for the Pacific Plate and its Tectonic Implications

We have revised calculated pole positions of the Pacific apparent polar wander path (APWP) for the Cretaceous and Cenozoic. Previous poles on the Pacific APWP have been constrained primarily by seamount magnetic anomaly inversions and skewness of seafloor spreading magnetic anomalies, both with shortcomings related to interpretation of magnetic anomalies. We compiled a diverse data set consisting of paleocolatitudes determined from sediment piston cores, sediment and basalt cores from ocean drilling, paleodeclinations from seamount magnetic anomalyinversions, and effective inclinations from magnetic lineation skewness. By combining several types of data, potential bias by any one type is reduced. The APWP shows ~40o of northward movement since Early Cretaceous (~123 Ma) time. Jurassic data are few and suggest southward APW prior to an Early Cretaceous turnaround. Although the timing of the turnaround is poorly constrained, it appears coincident with the timing of Ontong Java Plateau formation, suggesting a link between the two events. Interestingly, a paleomagnetic pole for sites on the Ontong Java Plateau is significantly different from the pole calculated from contemporaneous data elsewhere on the Pacific plate. The difference implies that the plateau is on lithosphere that has moved north ~15o less than the rest of the plate and suggests parts of the Cretaceous Quiet Zone Pacific plate may have been amalgamated from surrounding plates. Contrary to prior interpretations, the APWP does not show an Early to mid-Cretaceous stillstand, but slow northward polar motion until ~92 Ma instead. APW between ~92-83 Ma is rapid, coincident with the polar shift described by Sager and Koppers [Science, v. 287, p. 455, 2000]. Although the rapid shift ended by Chron 33r (~83 Ma), the beginning is poorly constrained by sparse data and thus the drift rate is uncertain. From Chron 33r to ~44 Ma, there is a polar stillstand, and afterwards the poles drift northward to the spin axis. The Late Cretaceous to early Cenozoic stillstand is curious in that it corresponds almost exactly to the duration of formation of the Emperor Seamounts, suggesting a link. Rotated into the Antarctic plate reference frame, Late Cretaceous-Cenozoic Pacific poles show a ~10o offset from the Antarctic APWP, implying problems with the Pacific-Antarctic plate motion circuit. The stillstand implies no northward movement of the Pacific plate for ~35 Myr, at odds with accepted models of plate motion containing significant northward drift at this time. The APW reinforces conclusions that the Emperor Chain melting anomaly moved south (e.g., Tarduno et al., Science, v. 301, p. 1064, 2003), but our results imply greater overall motion (>20o). Data from the Pacific alone do not allow us to say how the southward motion occurred; whether it was entirely through melting anomaly motion or whether other phenomena, such as true polar wander or changing non-dipole components in the geomagnetic field also played a role.