Abstract

The Cobequid–Chedabucto fault system of the Canadian Appalachians is a major anastomosing fault system over 300 km in length. It separates the Meguma Terrane of southern Nova Scotia from the Avalon Terrane to the north. These terranes are distinct tectonic and lithological entities in the Appalachian Orogen. Two areas at either end of this fault system have been examined in detail to determine the sense and history of offset along it. Both areas are situated on major component fault zones of the system, and both exhibit structures due to early intense ductile shearing that are overprinted by semi-brittle to brittle structures caused by later faulting. Along the eastern Chedabucto fault zone (area A), ductile structures were examined. This area is characterized by the progressive development of S–C textures and shear bands, rotated syntectonic porphyroblasts, and asymmetric minor folds, features indicative of and caused by ductile shearing. Along the western Cobequid fault zone (area B), semi-brittle and brittle structures were studied. A distinctive asymmetric geometrical package of faults, self-similar at a variety of scales, is developed throughout this part of the fault system. Ductile and brittle displacement sense (kinematic) indicators at both sites indicate a protracted history of dextral strike-slip movement. No evidence was observed for major sinistral movement.

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