The para-autochthonous section northeast of the surface expression of the triangle zone in west-central Alberta is cut in places by hinterland-vergent backthrusts and by more steeply dipping (ca. 40 degrees) foreland-directed reverse faults. The geometry of the thrust faulting above the upper detachment can be mechanically explained, in principle, by a model in which the para-autochthonous section is underlain by a hinterland-verging detachment. Blind duplexes observed within the foreland basin are interpreted as part of an extremely low-angle intercutaneous wedge that extends into the foreland from the triangle zone. Given this interpretation, geometric relationships between the faulting observed above and below the upper detachment show that these structures could not have formed in sequence. Alternative models that do not involve a low-angle intercutaneous wedge require substantial layer-parallel shortening above the upper detachment and, so far, lack observational support.