During the Late Silurian, the eastern margin of the M'Clintock Basin was the site of slow sedimentation on a relatively stable carbonate platform. It is apparent, however, that contemporaneous (syndepositional) faults segmented this basin into several quasi-independent subbasins during deposition of the Cape Storm, Douro, and Somerset Island formations. Differential subsidence of these subbasins played a major role in controlling sedimentation patterns and stratigraphie thickness. These subbasins may have been sustained into the Early Devonian, as is evident from the facies of the overlying Peel Sound Formation. The east–west orientated, reactivated basement faults bounding the subbasins served as zones of weakness during the development of the Cornwall is Fold Belt and are evident in the present-day outcrop.