Abstract The first part of this chapter deals with the concepts of morphogeological belts, tectonic assemblages and terranes. These concepts are fundamental to the understanding of Canadian Cordilleran evolution and play an important role in the organization of the volume. Part B is mainly devoted to recent paleontological studies and their significance relative to the characterization of Cordilleran terranes. No attempt is made to synthesize the full scope of paleontology in the context of Cordilleran geology, a subject beyond the purview of this volume, but the importance of this discipline will be apparent in the chapters on stratigraphy. Part C presents a synthesis of crustal geophysical surveys including refraction and reflection seismology, seismicity, heat flow, geomagnetism, gravity, isostasy and magnetotellurics. Although many of these studies are in their infant stages they have already provided a wealth of data on the nature of the deep crust and processes contributing to its evolution.

Abstract The pre-Late Devonian Cordilleran miogeocline consisted of extensive shallow-water platforms upon which carbonate-clastic deposits accumulated. They were flanked to the west by deep-water environments where shale and carbonate accumulated (Rocky Mountains Assemblage). Clastic sediments were largely craton-derived. During the Late Devonian sedimentation patterns changed dramatically as turbiditic, chert-rich clastics, derived from the west and north, flooded the northern Cordillera (Earn and Imperial assemblages). Shale (Besa River Assemblage) was deposited far out onto the miogeocline and InteriorPlatform; the carbonate front of the Rundle Assemblage retreated far to the east and south of its Middle Devonian position. By mid-Mississippian time the clastic influx waned and normal marine shelf carbonate and clastic sedimentation resumed, once again with clastics derived from the craton. Devono-Mississippian plutonism occurred only in northernmost Yukon Territory, and volcanism was restricted to central Yukon and south-central British Columbia.Pre-Late Mississippian folding occurred in northern Yukon but elsewhere deformation is expressed only by local high-angle faults and disconformities. Devono-Mississippian tectonism in the northern Yukon involved uplift and granitic intrusion in Frasnian to Early Mississippian time, resulting in an upward shoaling and southward-prograding clastic wedge. The sequence consists of shale at the base, flyschoid sediments near the middle, and partly fluvial-deltaic strata at the top. Deformation migrated southward from the area of uplift until the clastics themselves were folded prior to the mid-Carboniferous. The source of Devono-Mississippian sediments in the central Cordillera was uppermost Precambrian quartzose clastics and lower Paleozoic chert from the western miogeocline. Western coarse clastics are typified