Structure and stratigraphy in the Pennsylvanian tectonic zone of southern New Brunswick, Canada: the ‘Maritime coastal disturbance’ revisited

Abstract

Abstract Identified as the ‘Variscan Front’ 40 years ago, the Pennsylvanian tectonic zone of southern New Brunswick has presented structural and stratigraphic challenges for the last century. In 1986, R. Damian Nance presented an integrated tectonostratigraphic analysis which suggested that the zone represented a transpressive flower structure controlling both deposition of Pennsylvanian sedimentary formations and their subsequent deformation, a consequence of Meguma terrane docking and subsequent adjustment. The strength of this model is demonstrated through the integration of recent field studies and more recent geochronology, which refines the details and expands the scale of the flower structures. Current understanding suggests that three large transpressive structures developed diachronously, and the southern tectonic zone is linked with strike-slip faults to the north (especially the Kennebecasis Fault) via the Spruce Lake Shear Zone. The early history of this zone coincides with a change from deposition of locally sourced continental red beds (lower Pennsylvanian or youngest Mississippian Balls Lake Formation) to more distally sourced fluvial deposits (lower Pennsylvanian Lancaster and Tynemouth Creek formations). Rather than being an isolated segment of a late Pennsylvanian ‘Variscan front’, this tectonic zone can be integrated into the overall strike-slip regime that dominated the Carboniferous evolution of this orogen and the successor basins.