Geological and geochronological results of an investigation of the Paleoproterozoic siliciclastic and carbonate supracrustal rocks of the Lake Harbour Group (LHG) and surrounding tonalitic gneisses on southern Baffin Island are presented. Conventional U – Pb geochronology of monazite from rocks of the LHG suggest that penetrative deformation of these rocks occurred prior to, or during, peak metamorphic conditions at ca. 1845 –1840 Ma. Conventional U – Pb zircon results indicate that much of the tonalitic gneiss ranges in age from to 1827. The tonalitic gneisses and Lake Harbour Group units were tectonically imbricated by ca. 1805 Ma, and are part of a southwest-verging thrust belt interpreted from regional considerations to represent the northern continuation of the Ungava Orogen. The present results indicate that current tectonic models for the evolution of northeastern Laurentia that involve a dominantly Archean southeastern Rae province require revision. It is proposed that much of the metaigneous material that lies between the Archean Superior and Nain cratons represents a composite subduction-related domain.