Age and nature of the Canadian part of the circum-pacific orogenic belt

Abstract

The Canadian Cordilleran orogen evolved from a miogeosyncline which existed from Proterozoic to mid-Jurassic time in the Rocky Mountains and part of the Yukon, and a more or less contemporaneous, complex eugeosyncline on the west. The history of the eugeosynclinal belt since the mid-Palaeozoic, was influenced by the more or less persistent Coast and Omineca crystalline geanticlines and at times, by the non-metamorphic Pinchi geanticline between them. Since mid-Triassic time the crystalline geanticlines have been the principal sites of frequent uplift, recurrent granitic intrusion, metamorphism and deformation. Orogeny was rarely widespread at any time. The crystalline geanticlines were repeatedly deformed but not always synchronously, whereas adjoining troughs were rarely deformed more than once. Orogenic pulses took place at the following times: Proterozoic, Early and mid-Palaeozoic, Middle and locally Early Triassic, Middle Jurassic, latest Jurassic and earliest Cretaceous, mid-Cretaceous, Early and Late Tertiary.