The Yukon-Tanana terrane (YTT) in southeastern Yukon consists predominantly of a mid-Paleozoic volcanic-plutonic (arc?) assemblage built on continental crust. The YTT had experienced strong deformation and metamorphism by Late Triassic time. By mid-Cretaceous the metamorphic complex and Late Triassic clastic rocks derived from it were imbricated with middle and upper Paleozoic “ophiolitic” sheets. The YTT differs markedly from adjacent parts of the North American continental margin in both its depositional and tectonic histories. The composition and tectonic history of the YTT is comparable to that of the Kootenay and Barkerville terranes of southern and central British Columbia from which the YTT may have been displaced.