Steep crustal-scale faults, having their origins in the Late Archean and Early Proterozoic and trending NE-SW, which define the fundamental block lithospheric structure of the North American craton, are seen from geological and geophysical evidence to continue far into the interior of the Late Proterozoic-Phanerozoic Canadian Cordilleran mobile megabelt. This suggests that variously reworked ex-cratonic basement blocks underlie much of the Cordillera. The western edge of the modern craton is probably near the Rocky Mountain-Omineca belt boundary; the Rocky Mountain fold-and-thrust belt on the east side of the Cordillera is evidently rootless and overlies the undisturbed cratonic basement. Phanerozoic differences between the Cordilleran tectonic belts, resulting from a long, dissimilar, multi-cycle history of waxing and waning orogenesis apparent from the rock record, lie chiefly in the degree of indigenous tectonic remobilization and reworking of the ancient crust.

The NE Pacific Ocean is considered the birthplace of many fundamental ideas for modern plate tectonics theory. In this book the orogenic belts of this region are discussed in a single, internally consistent tectonic concept. Geological information is considered the most reliable. Geophysical models are tested for compatibility with observable geological data. The new concept avoids force-fitting interpretations to preconceived assumptions regarding accreted far-traveled terranes in the Cordillera and continental-oceanic plate interactions in the entire region.