Provenance and tectonic evolution of the Meguma terrane, northern Appalachian orogen

The Meguma terrane is a fragment of the Armorican terrane assemblage that either (1) was transferred to East Avalonia during Early Paleozoic rifting and opening of the Rheic Ocean or (2) was accreted as an isolated terrane or as part of a Gondwanan promontory. The Meguma terrane comprises two distinct subterranes, which dextrally moved opposite West Avalonia before their Emsian to Frasnian assembly and underthrusting by an Avalonian promontory in SE Cape Breton Island. Dextral oblique flat subduction of the Rheic Ocean inhibited upper plate magmatism and generated folding and oblique reverse faults during early Kejimkujic orogenesis. Late Devonian steepening of the Rheic slab re-established a metasomatized mantle wedge and produced subduction-related magmas in the Meguma terrane with anhydrous A-type magma in the distal backarc situated in West Avalonia. Kejimkujic indentation of the Meguma terrane by the West Avalonian promontory during the Famennian led to sinistral and dextral strike slip faulting, and transpression near the area of indentation. Kejimkujic orogenesis was followed by Early Carboniferous W-directed dextral motion of the Meguma terrane using the Minas Fault zone as a transfer fault and related transtension. Mid-Carboniferous Alleghenian contraction generated localised D 2 sinistral oblique reverse slip, commonly reusing existing shear zones.