Significance of the Baie Verte Flexure, Newfoundland

Abstract

The Baie Verte Flexure is a regional structure defined by the change in trends of early Paleozoic rocks of the Baie Verte Peninsula, Newfoundland. The flexure affects all major geological elements on the peninsula, including the Baie Verte Line, a fundamental polygenetic structural zone that juxtaposes continental polydeformed metaclastic rocks of the Fleur de Lys Supergroup, to the west, against inhomogeneously deformed ophiolites and volcanic rocks to the east. The tectonic history of both sequences has been a major point of contention in northern Appalachian geology; recognition of the flexure resolves this problem. Central to this problem has been the geological setting of an apparently isolated sequence of metaclastic rocks, the Ming9s Bight Group, that occurs in the midst of the ophiolite-volcanic terrane. Previous workers have assumed that the group, which is lithically and structurally similar to parts of the Fleur de Lys, is conformable with the adjacent ophiolitic-volcanic terrane. Delineation of features along the flexure clarifies the stratigraphic and structural relationships of the group. In particular, recognition of a continuous belt of Fleur de Lys rocks that wraps around the northern portion of the peninsula indicates that the Ming9s Bight Group forms part of the supergroup; in addition, the tracing of the Baie Verte Line around the flexure shows that the group is tectonically severed from the ophiolitic-volcanic terrane. The polydeformation of the Fleur de Lys rocks and northerly parts of the ophiolitic-volcanic terrane appears to have been inhomogeneous. Regional relationships and recent Ar 40 / Ar 39 ages indicate that rocks of the main Fleur de Lys outcrop belt were deformed mainly during the Taconic, whereas the Ming9s Bight Group and parts of the ophiolitic-volcanic terrane were affected by an Acadian event. This can be explained by two separate, noncoaxial events acting upon some pre-existing manifestation of the flexure, probably the irregular margin of the ancient continent. Relationships along the Baie Verte Flexure may reflect inherent complexities of larger flexures, salients, and recesses of the Appalachian Orogen and may be important to interpretation throughout the orogen.