A 6K MA PALEOMAGNETIC POLE FOR THE PACIFIC PLATE FROM THE SKEWNESS OF MAGNETIC-ANOMALIES 27R-31

We use the skewness of seafloor-spreading magnetic anomalies 27r-31 to determine a revised Late Maastrichtian-early Palaeocene palaeomagnetic pole for the Pacific plate. We used numerical experiments to estimate the potential information in magnetic profiles that had not been previously analysed for skewness information. The results indicated that profiles obtained between the Murray and Galapagos fracture zones would be the most useful because in this region very different values of remanent magnetic effective inclination are predicted for small changes in the assumed palaeomagnetic pole position. Furthermore, these data would constrain the pole in the direction most poorly constrained by prior data. Using 50 skewness estimates from 17 profiles, we compute a well-constrained pole that agrees with a pole computed from other types of data with similar ages. These other data include a seamount palaeomagnetic pole, effective inclinations from two submarine ridges, palaeolatitudes determined from azimuthally unoriented cores of submarine basalt and from a piston core in deep-sea sediments, two palaeo-equators from equatorial sediment facies, and amplitude data from magnetic lineations. Combining all the data, we determine a best-fit 65 Ma palaeomagnetic pole for the Pacific plate that is located at 71.6-degrees-N, 7.9-degrees-E. The 95 per cent confidence ellipse for the new pole, a 2.9-degrees major semiaxis oriented 75-degrees clockwise of north and a 1.8-degrees minor semiaxis, is approximately 50 per cent smaller in area than that for the prior pole. We conclude that anomaly skewnesses can be used to determine accurate palaeomagnetic poles for plates containing oceanic lithosphere.