Late Cretaceous Polar Wander of the Pacific Plate: Evidence of a Rapid True Polar Wander Event

We reexamined the Late Cretaceous–early Tertiary apparent polar wander path for the Pacific plate using 27 paleomagnetic poles from seamounts dated by40Ar/39Ar geochronology. The path shows little motion from 120 to 90 million years ago (Ma), northward motion from 79 to 39 Ma, and two groups of poles separated by 16 to 21 degrees with indistinguishable mean ages of 84 ± 2 Ma. The latter phenomenon may represent a rapid polar wander episode (3 to 10 degrees per million years) whose timing is not adequately resolved with existing data. Similar features in other polar wander paths imply that the event was a rapid shift of the spin axis relative to the mantle (true polar wander), which may have been related to global changes in plate motion, large igneous province eruptions, and a shift in magnetic field polarity state.