Mantle reflections along the Lithoprobe Slave Northern Cordillera Lithospheric Evolution (SNORCLE) deep seismic reflection transect in northwestern Canada are interpreted as a relict subduction zone. Geometric features of the data in the vicinity of the interpreted subduction zone are compared with those of the Vancouver Island profile, which images a modern convergent margin. Comparisons are made at both a regional scale, as in the case of the location of the magmatic arc with respect to the subduction zone, as well as a local scale, such as the geometry of structures within the accretionary wedge. The comparison provides a test for the paleosubduction hypothesis and aids the interpretation of the deep reflection profile where it is difficult to trace individual features to outcrop. The similarity of geometry and scales of the structures gives support to the interpretation that the lithospheric structures in the Wopmay orogen are the products of accretionary processes at ~1.88--1.84 Ga and that these accretionary processes are similar to those observed today. ¿ 1999 American Geophysical Union