Résumé
The northern Canadian Cordillera (NCC) is a high-elevation, low relief (relative to coastal ranges) mountain belt that extends from northern British Columbia to the south, eastern Alaska to the west, the Beaufort Sea to the North and the Canadian Shield to the east. This region has experienced more than 2.5 Gyr of tectonic evolution from the formation of the cratonic core of North America through the development of the Phanerozoic Canadian Cordillera. Contemporaneous tectonic activity generates distributed seismic activity within a wide transpressive belt across the Mackenzie and the Richardson Mountains, presumably substantially driven by convergence of the Yakutat terrane in southeast Alaska. Before the establishment of several recent deployments of broadband seismographs (including the EarthScope USArray Transportable Array), models of the structure and dynamics of the NCC suggested thin and hot cordilleran lithosphere due to its position in a former arc and back arc setting. In recent years, new seismic velocity models of the crust and upper mantle in the NCC have shed light on the role of heterogeneous modern and fossil structures in controlling tectonic history and present activity. Here we provide a review of these models to characterize the crust and upper mantle at different scales, including those obtained from receiver functions, teleseismic shear-wave splitting data, surface-wave and teleseismic body-wave tomography. These models indicate that the Moho is relatively flat at approximately 30-35 km depth, the lithosphere-asthenosphere boundary is located at approximately 50-60 km, and the cratonic lithosphere extends beneath the eastern part of the NCC. Toward the south, we identify a westward dipping structure anchored beneath the Cordillera Deformation Front. Furthermore, sharp changes in seismic velocities and seismic anisotropy at upper mantle depth indicate that the Tintina Fault is a mantle-penetrating shear zone and may have displaced blocks of cratonic lithosphere along the former Laurentian margin. Finally, we explore constraints on the thermal structure of the NCC from these seismic velocity models and indicate where more work is needed to constrain the temperature and composition of the NCC lithosphere.