Canadian Cordilleran displacement: palaeomagnetic results from the Early Jurassic Hazelton Group, Terrane I, British Columbia, Canada

SUMMARY The Early Jurassic Telkwa Formation, comprising the base of the Hazelton Group, was sampled at three areas in the central part of the Stikine Terrane, British Columbia. Detailed alternating field and thermal step demagnetization on samples from nine sites from the Red Canyon area and 10 sites from the Zymoetz River area, both of which are in the Bulkley Ranges, and eight sites from the Telkwa Range area isolate stable remanence magnetization components. The components are interpreted to be primary magnetizations because of the presence of two polarities and the much improved agreement of their inclinations after full tilt correction of the sites from the Bulkley Ranges. Within‐locality declinations agree well; between‐locality declinations are discordant. The expected cratonic declination is ˜340° whereas declinations from this study are 265°, 227° and 328° for the Red Canyon, Zymoetz River and Telkwa Range areas respectively. These results are similar to those of Monger & Irving (1980) and we concur that the discordant declinations are the result of differential rotation about vertical axes between sample localities. Our observed mean inclination of 52° is in good agreement with Monger & Irving's (1980) result of 54°. They interpreted this to indicate ˜1300 km of northward displacement since the Early Jurassic and their interpretation was substantiated by several later studies. However, with revisions to the geologic time‐scale and the Early Jurassic reference pole for North America, the Early Jurassic Canadian Cordillera palaeomagnetic data base appears latitudinally concordant. This indicates that Terrane I and southern Wrangellia were in much the same latitudinal position relative to the North American craton as they are now. Tectonic displacement models developed in view of discordant Cretaceous palaeomagnetic data from the Canadian Cordillera must now consider latitudinally concordant Permian to Early Jurassic data and Middle Eocene to Recent data. This tectonic senario appears more reconcilable with the regional tilt hypothesis. However, this hypothesis cannot account for discordant Cretaceous data from bedded volcanic rocks in Terrane I. It is therefore probable that Cretaceous Cordilleran tectonics were characterized by both regional tilting and moderate latitudinal displacement.