EarthRef.org Reference Database (ERR) -- Petronotis & Gordon 1999

The asymmetry (skewness) of marine magnetic anomaly 32 (72.1-73.3 Ma) on the Pacific plate has been analysed in order to estimate a new palaeomagnetic pole. Apparent effective remanent inclinations of the seafloor magnetization were calculated from skewness estimates of 108 crossings of anomaly 32 distributed over the entire Pacific plate and spanning a great-circle distance of similar to 12000km. The data were inverted to obtain a palaeomagnetic pole at 72.1 degrees N, 26.8 degrees E with a 95 per cent confidence ellipse having a 4.0 degrees major semi-axis oriented 98 degrees clockwise of north and a 1.8 degrees minor semi-axis; the anomalous skewness is 14.2 degrees +/- 3.7 degrees. The possible dependence of anomalous skewness on spreading rate was investigated with two empirical models and found to have a negligible effect on our palaeopole analysis over the range of relevant spreading half-rates, similar to 25 to similar to 90 mm yr(-1). The new pole is consistent with the northward motion for the Pacific plate indicated by coeval palaeocolatitude and palaeoequatorial data, but differs significantly from, and lies to the northeast of, coeval seamount poles. We attribute the difference to unmodelled errors in the seamount poles, mainly in the declinations. Comparison with the northward motion inferred from dated volcanoes along the Hawaiian-Emperor seamount chain indicates 13 degrees of southward motion of the Hawaiian hotspot since 73 Ma. When the pole is reconstructed with the Pacific plate relative to the Pacific hotspots, it differs by 14 degrees-18 degrees from the position of the pole relative to the Indo-Atlantic hotspots. This has several possible explanations including bias in one or more of the palaeomagnetic poles, motion between the Pacific and Indo-Atlantic hotspots, and errors in plate reconstructions relative to the hotspots.