The Lower Cambrian McNaughton Formation of the Gog Group occupies a stratigraphic position transitional between the rift-related rocks of the underlying Upper Proterozoic Miette Group, and the overlying Paleozoic passive margin succession. A major regional unconformity, overlain by a distinctive orthoquartzite marker, has been traced within the McNaughton Formation. This unconformity has been shown to truncate normal faults active during the deposition of the lower McNaughton Formation. The lower McNaughton Formation consists of mature, coarse-grained fluvial sediments accumulated in hanging-wall half-grabens of active normal faults. These faults represent the final stage of rifting on the continental margin. The unconformity on the footwall blocks of these faults can be traced into the hanging wall, and is overlain by the shoreface sediments of the transgressive upper McNaughton Formation. Formal subdivision of the McNaughton Formation into four lithostratigraphic members is proposed, in order to describe this geometry.