Abstract It is well established that the Hawaiian hotspot moved southward relative to the spin axis in Paleogene time. Two contrasting prior explanations are: (a) reorientation of the solid Earth relative to the spin axis (i.e., true polar wander (TPW)), and (b) independent southward motion of the Hawaiian hotspot through the mantle. Here we distinguish between these hypotheses by determining a new chron C24r (56 Ma) Pacific plate paleomagnetic pole from skewness of marine magnetic anomalies. This extends a set of Pacific plate spin‐axis locations for which the repeatability is 2–5.5 times better than for coeval continental paleomagnetic poles. The new pole extends the northward progression of the prior 73–58 Ma Pacific plate apparent polar wander (APW) track such that it overlaps the southern end of the 48–12 Ma track. From 56 to 48 Ma (between two intervals of true polar stillstand) either the Pacific plate moved rapidly southward relative to the mantle (with even faster southward motion of Pacific hotspots with both Hawaii and Louisville hotspots moving south) or TPW occurred. The reconstructed plate geometry and relative plate motions are inconsistent with ancient plate driving forces having caused the observed southward motion relative to the spin axis. The best explanation is an ∼6°–7° episode of TPW, but motion between hotspots and some southward motion of all Pacific hotspots through the mantle may also have occurred. The hypothesized TPW episode occurred near the end of the Early Eocene Climate Optimum and the onset of Cenozoic cooling.
Woodworth et al. (Mon,) studied this question.