The eastern Waddington thrust belt cuts the eastern margin of the Coast Mountains mid-Cretaceous magmatic arc. Thrust faults carried Triassic rocks of the Intermontane superterrane, Early Cretaceous volcanic and clastic rocks, and volcanic and plutonic rocks of the active arc to the northeast, outward from the core of the arc. Minimum shortening across the thrust belt is estimated as 50% or 40 km. Synkinematic through postkinematic metamorphism produced an inverted metamorphic gradient with the structurally higher magmatic arc as the likely heat source. Radiometric, thermochronologic, and structural data indicate that the thrust belt was active at 84 Ma and probably at 87 Ma and suggest that the peak of postkinematic metamorphism occurred about 82--84 Ma. The thrust belt was intruded by postkinematic plutons in latest Cretaceous and early Tertiary time (68 Ma and 58Ma). The eastern Waddington thrust belt is coeval with or slightly younger than a system of west directed thrusts in the western and southern parts of the Coast Mountains arc. The prominence of these structures suggests that synmagmatic contraction played a major role in development of the arc. The distribution and character of syn-and postthrusting metamorphism indicate that this contraction, rather than localized loading by magma, produced the metamorphism. ¿ American Geophysical Union 1994