The Ellesmerian orogeny of Laurussia – A far-field effect of the late Devonian collision of Gondwana with North America

Convergent tectonics of the Ellesmerian orogeny affected Arctic Canada and Svalbard in late Devonian - early Carboniferous times. The coeval ultra-high pressure metamorphism in NE-Greenland, the formation of the Maritimes Basin in the Canadian Appalachians, and tectonic activity in the Antler orogeny (Nevada, USA), raised a controversy about whether the Ellesmerian orogeny was related to either late Caledonian plate tectonics or renewed, i.e., post-Caledonian convergence of Laurentia with the rest of Laurussia. Here, we argue that the Ellesmerian orogeny represents a far-field effect of the collision of a Gondwanan promontory with the Appalachian segment of Laurussia. This collision caused the decoupling of the North American lithosphere from Laurussia. The northward motion of this lithospheric domain relative to Laurussia explains the tectonic events along its boundaries, namely the Ellesmerian and the Antler orogenies along the frontal and the Panthalassan margins, respectively. Furthermore, it triggered the reactivation of the NE segment of the Greenland Greenland-Scandinavian Caledonides under dextral transpression causing UHP metamorphism. To the southeast, the formation of the Maritimes Basin reflects dextral transtension and associated strike-slip faults parallel to the edge of SE-Greenland. Strain compatibility requires the existence of a dextral lithospheric-scale strike-slip fault that links the tectonic structures and transects the Greenlandian part of the North American Craton. Because this proposed shear zone in SE Greenland follows small-circle trajectories of the motion of Gondwana relative to Laurussia, we interpret the southeastern edge of Greenland as a dextral transform boundary of the decoupled North American lithosphere.