Western Canada

In this volume the main Western Cordillera of North America is represented by the following analysis of a segment across south-western Canada from the Interior Plains to the Pacific. It is an orogenic belt which has been intensively studied as a unit in many of its aspects, and in the eastern part of which accurate deep borehole data are available from oil exploration activities. It is a complex, with outward facing highly deformed zones separated by a much less deformed median belt, and one which has a long history of plutonic intrusion. Much of the critical information quoted is new, and the detailed data are preceded by a full analysis of the developmental history of the belt. Segment: the ‘segment’ of the Western Canadian Cordillera described here has a length, measured along the strike, of 160 km. Within this segment the margin of the belt against the non-orogenic area to the east is narrowly gradational (½ to 3 km) and the western margin is submarine. The orogenic belt has an exposed width of 800 km. Zones: the Canadian Cordillera is formed of two intensely tectonized belts—the Western and Eastern Cordillera—separated by a less tectonized zone, the Interior Plateau. The Western Cordillera comprises zones 1–3, the Interior Plateau is zone 4 and the Eastern Cordillera includes zones 5 and 6. Zone 1 (Insular Belt)—volcanic and plutonic rocks are dominant, with thick Triassic basaltic volcanics and major Jurassic plutonic rocks. Metamorphism occurred in Jurassic times. Stratified rocks range in age from Carboniferous