HR: 11:20h
AN: U32A-05    [Abstracts]
TI: Cretaceous Apparent Polar Wander Relative to the Major Cratons and Displacement Estimates of Baja British Columbia
AU: * Enkin, R J
EM: renkin@nrcan.gc.ca
AF: Geological Survey of Canada - Pacific, P.O. Box 6000, Sidney, BC V8L 4B2 Canada
AB: When paleogeographic interpretations derived from independent observations conflict, the methods and results from each discipline come under careful scrutiny, as illustrated by the Baja British Columbia controversy. Cretaceous paleomagnetic data from a large region of the Canadian Cordillera render paleopoles which are far-sided with respect to cratonic North American poles, suggesting this region, designated Baja British Columbia, translated northward during Late Cretaceous - Paleogene time. Criticism of this interpretation based on other geological reasoning prompted me to perform new reviews of Cretaceous to Eocene paleomagnetic results from the Cordillera and from the major cratons of the globe. The global review follows the method of Besse and Courtillot (1991; 2002). One difference between our methods is that I compiled paleomagnetic results from highly studied rock units to single results to balance data weightings spatially and temporally, thus reducing the number of individual results. For the period 160 to 40 Ma, 51 poles were included compared to 92 poles by Besse and Courtillot (2002). Differences between apparent polar wander paths in their and my analyses are never significant at 95% confidence, however mean pole positions differ by up to 500 km, which is important for paleogeographic analysis. The global distribution of sampling localities and the tight clustering of the paleomagnetic poles after plate reconstruction provide invaluable confirmation of plate tectonically derived Euler rotations, the reliability of paleomagnetic remanence directions, and the geocentric dipole geometry of the geomagnetic field. My Cordilleran review shows that paleolatitudes derived from plutons and remagnetized rocks are significantly more scattered than those derived from bedded rocks. Using bedded rocks only, the paleomagnetic record shows that Baja British Columbia sat $2100 \pm 500$ km south of its present position with respect to cratonic North America during the Late Cretaceous (90 to 70 Ma) with accretion finishing by the mid-Eocene (50 Ma).
DE: 9350 North America
DE: 9609 Mesozoic
DE: 8102 Continental contractional orogenic belts
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
DE: 1532 Reference fields (regional, global)
SC: Union [U]
MN: 2004 AGU Fall Meeting