Concordant Cretaceous Palaeolatitudes from Felsic Plutons in the Canadian Cordillera

Abstract

Beck and Noson1 report that three sites from a Cretaceous (≈85 m.y.) granitic batholith in the Cascade Mountains of central Washington, USA, give anomalously low palaeomagnetic inclinations compared to coeval rocks from the rest of the North American plate. They suggest that the discordance results from post-emplacement northward translation of the western Cordillera by about 25 arc deg relative to the North American craton. Here I report palaeomagnetic results from 17 sites of Cretaceous (≈95 m.y.) quartz diorites and grano-diorites collected along Howe Sound in southwestern British Columbia. These plutonic rocks are geologically part of the Coast Crystalline Belt of the western Cordillera graphically part of the Coast Mountains which are the northward continuation of the Cascade Mountains. The pole position for these sites is not significantly different from Cretaceous positions for units from cratonic North America and therefore does not support the hypothesis of northward tectonic translation of the western Cordillera relative to the craton.