A REVIEW OF CRETACEOUS PALEOMAGNETISM IN THE CANADIAN CORDILLERA AND THE GLOBAL CRATONIC REFERENCE

Paleomagnetic data from bedded rocks in the Canadian Cordillera suggest that a large region of the Cordillera (called Baja British Columbia) sat 2100±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). This translation evolution is inferred from plots of the paleolatitudes of the paleomagnetic results calculated at a common point in the Cordillera. Paleomagnetic studies from the major cratons are reviewed to produce a new Cretaceous and Paleogene reference paleolatitude curve for North America, and to establish that the global geomagnetic field is well-represented by a geocentric axial dipole. All Cretaceous and Paleogene paleomagnetic data for the Canadian Cordillera (with neighbouring parts of the U.S.A.) are reviewed. Results from intrusions and remagnetized rocks are roughly compatible with the paleolatitudes determined from bedded rocks, but they are scattered due to structural complications. Paleomagnetic as well as geological correlations stitch the Insular and Intermontane superterranes together by mid-Cretaceous time, so the displaced region must include most of the Cordilleran Hinterland. This new interpretation satisfies several geological difficulties with previous interpretations, especially along the Insular / Intermontane Superterrane Boundary. However, there are new geological implications concerning great motion within the western zone of the Foreland belt which are challenging to accommodate.