The kinematic evolution of the southeastern Canadian Cordiller (52¿N--54¿N) during the Jurassic is characterized by an eastward migration of the active boundary of convergence between North America and allochthonous terranes and by two reversals in regional structural vergence. To investigate possible mechanical controls on the kinematics of convergence, the thermal and geological structure of the Jurassic continental margin at three stages in its history of shortening were palinspastically reconstructed and analyzed with the use of strength versus depth profiles. The resulting models reproduce to a first order the observed distribution of brittle and ductile deformation and provide a mechanical basis for the localization and orientation of displacement zones during shortening of the continental margin. The initial eastward migration of the active boundary of convergence between North America and allochthonous terranes from outboard of the continental margin sediment prism into the thick central part of the continental margin prism is attributed to thermal weakening of the continental margin lithosphere during obduction of the oceanic terrane. The subsequent eastward migration of the ocnvergence boundary into the inner part of the continental margin lithosphere is attributed to thermal weakening of the lithosphere during prograde regional metamorphism. Reversals in regional structural vergence accompaning each migration apparently occur because the push necessary to continue displacement on one displacement trajectory exceeds the failure strength of another dispacement trajectory that dips in the opposite direction. ¿ American Geophysical Union 1989