A zone of structural weakness, characterized by thrust faulting, extends across Newfoundland from the southwestern coast to White Bay on the north. Studies in recent years in the Bay St. George area, at Grand Lake, and in White Bay make possible a discussion of the age and nature of the faulting. It is clearly marked in the Bay St. George area on the southwestern coast, where igneous and metamorphic rocks of the Long Range are in thrust contact with Carboniferous. In the interior, at Grand Lake, a high-angle fault separates Paleozoic lavas from Carboniferous sediments. Extensive thrust faulting in the Carboniferous paralleling the western side of the bay, dissimilarity of the sections on the opposite sides of the bay, and topography point to the presence of the zone in the White Bay region. A pronounced lowland connects Grand Lake with White Bay; deformation of the rocks in the lowland, as well as its continuity with the White Bay trough, suggests the presence of the zone of weakness.
The faults, wherever observed, dip at relatively high angles eastward and strike north-northeast. Carboniferous rocks are involved in all the areas mentioned. The zone of weakness is believed to be late Paleozoic, probably representing a feature of Appalachian orogeny.
Faulting of similar nature has been discovered on Cape Rouge and Cape Fox peninsulas on the eastern coast of the Northern Peninsula, where Carboniferous and Ordovician are in thrust relationship. It is suggested that the remarkably straight coast of the Northern Peninsula may represent the locus of a northward prolongation of the transinsular zone of weakness.
Other possible connections of fault lines on the northwestern coast of Newfoundland and in Notre Dame Bay with the main zone are also discussed.