Probable Rift Origin of Canada Basin, Arctic Ocean: ABSTRACT

ABSTRACT Formation of the Canada basin by post-Triassic rifting and rotating apart of the continental edges that border it seems the most workable and logical hypothesis with information available. Speculated counterclockwise rotation of the Alaska-Chukchi edge best rationalizes the complex geology of northern Alaska, whereas a single continental block before the Jurassic makes the best palinspastic fit for Arctic America. An ancient Canada basin rimmed by an early Paleozoic geosyncline would be unique, for no present sea floor older than about 200 m.y. has been identified elsewhere. The Arctic Ocean is the focus of present-day spreading and probably was the focus of earlier stages of spreading (a condition ignored in many generalizations on global plate-tectonics). Current spreading from the Gakkel ridge appears to have been preceded by a stage of spreading from the Alpha Cordillera, and spread of the Canada basin would be an initial stage, logically preceding the Alpha stage. Such a progressive shift of spreading-foci can be reversed to restore the fragmented American and European plates into the Arctic. Spread of the Canada basin is probable if the Atlantic formed by sea-floor spreading because analogies between the Arctic and Atlantic edges indicate a common origin: Late Devonian clastic wedges, shed continentwards from tectonic lands along or within present oceans, in Wrangel Island and northern Alaska and in the Arctic Islands are analogous to those in Europe and on the Atlantic seaboard. Permian-Triassic sedimentation in the Sverdrup basin, 190–200 m.y. diabase sills in northern Alaska, and Mesozoic-Cenozoic continental-edge sedimentation in the Arctic Islands are mirrored on the Atlantic seaboard. The Cretaceous-Holocene clastic depositional basin at the south end of the Canada basin is analogous to the Gulf of Mexico. The Late Cretaceous and younger deflections of the Cordillera in the Arctic and the diabasic emplacements in the northern Arctic Islands may reflect the later stages of spreading. Pre-Mesozoic plate tectonism may be represented by the widespread Proterozoic diabasic emplacements in the Canadian Arctic and by the Franklinian-Innuitian tract, where the volcanogenic rocks and deformation resulted not from a classical eugeosyncline-miogeosyncline couple but from the junction of a mid-Paleozoic continental edge and another plate on closure of a proto-Arctic Ocean.