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"I, inclinations from deep-sea cores; S, skewness of magnetic anomalies; C, relative amplitude factor from magnetic anomalies; M, seamount magnetization; E, equatorial sediment facies. 'l, Acton and Gordon (1994); 2, Sager (1987); 3, Petronotis et al. (1994); 4, Acton and Gordon (1991); 5, Sager and Pringle (1988); 6, Petronotis et al. (1992).

"I, inclinations from deep-sea cores; S, skewness of magnetic anomalies; C, relative amplitude factor from magnetic anomalies; M, seamount magnetization; E, equatorial sediment facies. 'l, Acton and Gordon (1994); 2, Sager (1987); 3, Petronotis et al. (1994); 4, Acton and Gordon (1991); 5, Sager and Pringle (1988); 6, Petronotis et al. (1992).

Fig. 5.23. Apparent polar wander path for the Pacific plate for the past 125 Myr, based on the data of Table 5.3. From Petronotis et al. (1994).

determined from 7 deep-sea sediment cores, 5 analyses of skewness, 1 analysis of the relative amplitude factor and 5 seamount paleomagnetic poles. These 18 measurements combine to give a paleomagnetic pole at 70.0°N, 3.6°E with confidence limits having semimajor axis of 3.2° with an orientation of 91° and semiminor axis of 1.9°.

The most recently determined apparent polar wander path for the Pacific plate is that given by Petronotis et al. (1994), based on the data listed in Table 5.3 and illustrated in Fig. 5.23 (see §6.4.1 for details regarding plotting apparent polar wander paths). The apparent polar wander path shows that the Pacific plate drifted northwards from 82 Ma to the present, although not at a steady rate. Prior to 82 Ma there is little northward motion and the east-west trend of the poles could have been caused by a rotation of the Pacific plate between 125 and 82 Ma. Most of this period coincides with the Cretaceous Normal Superchron, following which the plate drifted northwards. Several authors have suggested from studies of the evolution of the North Pacific that a reorganisation of plate boundaries occurred near the end of the KN Superchron (Rea and Dixon, 1983; Sager and Pringle, 1987; Mammerickx and Sharman, 1988).

Unfortunately, analyses as described above have not been applied to plates other than the Pacific. However, paleomagnetic inclinations have been measured using the sediments and basalts from the many DSDP cores that have been

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