Multichannel seismic reftection profdes obtained on Vancouver Island show that above a zone of decoupling between the North American and Juan de Fuca plates, Wrangellia is underplated by two accreted terranes of probable oceanic origin. Both the zone of decoupling and Wrangellia are disrupted by easterly dipping faults, some of which are thrusts. The crustal structure of Wrangellia comprises Paleozoic and Mesozoic volcanic and sedimentary rocks disposed as roof pendants upon, and large irregular masse s within, a ubiquitous Jurassic plutonic and metamorphic complex.