Collision along an irregular margin: a regional plate tectonic interpretation of the Canadian Appalachians

Abstract

An idealized plate tectonic model for the pre-Carboniferous development of the Canadian Appalachians explains the 400 km dextral offset of tectonostratigraphic zones from Quebec and northern New Brunswick to Newfoundland and the up to 600 km offset of oppositely verging belts of Acadian deformation from the Gaspé Peninsula to eastern Newfoundland. It is proposed that these offsets, which occur at the St. Lawrence promontory, result from the collision of an irregular North American passive continental margin with island arc and continental crust to the east, along an east-dipping subduction zone. The line of subduction is assumed to have been linear and the subducting slab to have maintained its mechanical integrity during collision. A "jigsaw fit" of the opposite sides of the Iapetus Ocean is made unnecessary by invoking lithospheric delamination and tectonic wedging during the Acadian orogeny in Newfoundland. The model is consistent with surface geology and recent deep seismic reflection observations from north of Newfoundland.