The stratigraphy and structural geology of the southeastern Cape Breton Highlands National Park and its implications for the tectonic evolution of Cape Breton Island, Nova Scotia, with emphasis on lineations in shear zones

The southeastern Cape Breton Highlands National Park lies astride the Aspy-Bras d'Or terrane boundary. Detailed structural analysis shows that the structural evolution of the area is a history of movement along ductile and brittle shear zones. Pre-Carboniferous deformation comprises two major episodes of ductile shearing: D;Study of the geometrical relationships between foliations and lineations in shear zones demonstrates that significant errors can arise from the common practice of directly correlating the obliquity of the stretching lineation with the obliquity of the movement direction. A simple method is established so that the orientation of the stretching lineation can be used to quantitatively deduce the movement direction. This study also helps to determine the nature of the D;Slickensides exposed by parting along C-surfaces in the D;Stratigraphic studies combined with structural analysis lead to a new interpretation of the stratigraphy in the area which involves a depositional relationship between the Aspy and the Bras d'Or terranes. Placing the new findings in the area in the context of the geology of the whole of Cape Breton Island results in the proposal of a model for the tectonic evolution of the island. The Aspy terrane is interpreted as a back-arc basin which opened as a result of Ordovician to Silurian northwestward subduction of the Iapetus Ocean under the Bras d'Or terrane volcanic arc and which closed in Late Silurian to Early Devonian times following the closure of the ocean.