Abstract The Cobequid Highlands of northern Nova Scotia lie at the intersection of two major dextral intra-continental shear zones which developed during closure of the Rheic Ocean and formation of Pangea. The Cobequid Shear Zone was an ENE–WSW transfer zone in a NE–SW-trending, orogen-parallel, shear system in the late Devonian–early Carboniferous (Neo-Acadian phase), in which syntectonic granite–gabbro plutons and volcanic strata <4 km thick were progressively deformed along multiple faults. In the Late Carboniferous–Permian, the Alleghanian collision of Africa with Laurentia formed the east–west-trending Minas Fault Zone, reactivating parts of the Cobequid Shear Zone. This deformation was mostly taken up on the master Cobequid–Chedabucto Fault. Deformation chronology is well constrained by the biostratigraphy of syntectonic sedimentary rocks, and by radiometrically dated igneous rocks and minerals in faults and veins. Early strike-slip faults were lubricated by magmatic heating, leading to dyke-to-pluton construction along multiple faults. During cooling, rooted gabbro was more resistant than ductile granite, thereby deflecting solid-state deformation. Neo-Acadian strike-slip displacement across the shear zone is estimated as >50 km. The location of Alleghanian deformation was influenced by the paucity of magmatism and the resistance offered by older stitching plutons.

Abstract The east–west Minas fault zone, separating the Early Palaeozoic Meguma and Avalon terranes of the Appalachians, experienced dextral strike-slip motion during the Carboniferous. Abundant oblique contractional structures indicate localized dextral transpression, immediately south of the zone, probably associated with a restraining bend. Subsurface data indicate that the deformed Horton Group clastic rocks are thrust above younger Windsor Group evaporites. Excellent exposures on wave-cut platforms of the Bay of Fundy show structures developed in transpression, including NE-trending upright and inclined folds; south-verging thrust and reverse faults; and NW-striking normal faults. Northwest-trending boudins, which are perpendicular and slightly rotated in a clockwise sense relative to fold hinges, provide a field indicator for dextral transpression. The earliest folds (F 1 ) are curvilinear and may have formed by deformation of wet sediment. F 2 tectonic folds show weak axial-planar cleavage. Locally, these have been rotated into reclined orientations; spectacular downward-facing folds are probably due to refolding by more east–west F 3 folds. The structures observed are consistent with pure-shear-dominated transpression, with the local angle of convergence α increasing over time. This strain history is compatible with progressive strain partitioning, probably associated with the spreading of topography developed at the restraining bend.