Two reversed refraction/wide-angle reflection profiles obtained across the Nelson Front by CONCRUST (77) group are interpreted in detail. The results indicate that the Moho beneath the boundary zone between the Superior and churhill provinces dips down toward the west and there exists a complicated lateral seismic structure in the upper crustal and midcrustal depths. The ray tracig results also indicate that there may exist a zone of negative velocity gradient along the boundary zone at the depth range of 4-13 km.