PALEOZOIC TECTONIC HISTORY OF ARCTIC BASIN NORTH OF ALASKA

The geology of the margin of the Canada Basin, together with geophysical data, leads me to reject the continental subsidence theory for the origin of the deep Canada Basin. Instead, the Canada Basin is, I believe, a true and probably very ancient ocean basin floored by oceanic crust and rimmed by an early Paleozoic geosynclinal belt. In the Upper Devonian, uplifts in this circumarctic geosyncline, accompanied by granitic intrusion, produced a wedge of coarse clastic sediments (exogeosyncline) that spread southward onto adjoining areas of Alaska, Canada, and Siberia. In both northern Alaska and the Canadian Arctic Islands, thick sequences of upper Paleozoic and younger strata were deposited unconformably on the rocks of the early Paleozoic geosyncline, showing a similarity in tectonic history between the areas. The Paleozoic history of the southern rim of the Canada Basin resembles that of other mobile belts bordering North America. The movement of the floor of the Arctic Ocean against the continental crust of North America (sea-floor spreading) would provide a mechanism to account for the long history of orogenic activity along the basin margin. The sharp bend in the structural elements of southern Alaska (the Alaska orocline) has been cited as evidence of clockwise rotation of the Arctic Islands of Canada from Alaska and the Soviet Arctic to their present position during the Mesozoic. However, the geologic and geophysical evidence available indicates that the Arctic basin has a longer history, extending into the Paleozoic, and that this bend in Alaskan structures may have been largely caused by spreading of the Pacific sea floor against the continental margin in the Gulf of Alaska.