Updated Pacific Plate Paleomagnetic Pole for Chron 32 (72 Ma), Uncertainties in Pacific- Hotspot Rotations, and Updated Pacific-Hotspot Plate Reconstructions

A fundamental problem of global tectonics and paleomagnetism is determining what part of apparent polar wander is due to plate motion and what part is due to true polar wander. One approach for separating these is available if the hotspots are tracking the motion of the mantle beneath the asthenosphere. To make progress on these questions and assumptions, high-quality paleomagnetic poles for the Pacific plate are needed, as well as estimates of Pacific plate motion relative to the hotspots and the uncertainties in such motion. Here we present results for all three. First, we present an updated Pacific paleomagnetic pole for chron 32 (72 Ma) determined from the skewness of magnetic anomaly 32 (Petronotis et al. 1999). The updated paleomagnetic pole corrects for the spreading-rate dependence of anomalous skewness (Dyment & Arkani-Hamed 1995, Koivisto et al. 2006). We furthermore build on a new method for objectively estimating plate-hotspot rotations and their uncertainties (Andrews et al. 2005) and present an updated reconstruction of the Pacific plate relative to the hotspots at 72 Ma along with the uncertainties in the reconstructions. We combine paleomagnetic and plate reconstructions to determine the total uncertainty of the 72 Ma Pacific plate paleomagnetic pole reconstructed into the Pacific hotspot frame of reference. The results indicate that the pole is distinctively different from the present spin axis, but consistent with our estimate of the coeval paleomagnetic pole for the Indo-Atlantic hotspots. These results therefore indicate that the hypothesis that the Indo-Atlantic hotspots have been fixed relative to the Pacific hotspots cannot be rejected from paleomagnetic data.