Tectonic History of Northern Alaska, Canadian Arctic, and Spitsbergen Regions Since Early Cretaceous

ABSTRACT The correlation of interregional unconformities, structures, and magmatic activity suggests tectonic events in the Arctic were controlled by the Early Cretaceous collision and combined interaction of the Eurasian and North American plates in northeastern USSR, the late Mesozoic-Cenozoic accretion of exotic terranes in the North Pacific, and North Atlantic-Arctic sea-floor spreading. Contemporaneous with the accretion of exotic terranes in northeastern USSR and interior Alaska, the Brooks Range developed as a cordilleran mountain belt. At the same time, during the Cretaceous between 125 and 85 Ma, the Canada basin spread north of Alaska about a pole of rotation located southeast of the Mackenzie delta. The “Alaskan plate” was first a part of the northwestern nose of the North American plate. When the Canada basin spreading ceased, the basin was severed by movement along the Kaltag and associated strike-slip faults, and became a part of the northeasterly moving Eurasian plate. The Kaltag fault system is inferred to extend from the western Bering Sea at the northern end of the Kuril arc, through Alaska, and along the outer margin of the Arctic Islands to the north of Greenland. It is postulated to have formed the transform boundary between the North American and Eurasian plates (with the Alaskan plate bonded to the latter) since the Late Cretaceous. The late Eocene change in the direction of Pacific spreading terminated the subduction-related Laramide orogeny as well as the right-lateral displacements of major cordilleran faults, such as the Tintina and Denali faults. Changing Eurasian plate movement may have caused most of the strong middle Eocene right-lateral displacement along the Kaltag fault zone. Continuing displacement from the southwest caused the development of a late Cenozoic foldbelt in coastal northeastern Alaska, herein named the “Romanzof disturbance,” coeval with balancing right-lateral movement along the Kaltag fault zone. The huge undrilled Marsh Creek anticline is a part of this foldbelt. Seismic data show evidence of middle Eocene compression followed by weak extension east of the Kaltag fault zone in the Beaufort Sea. The same activity is evident at the northeastern end of the North American plate at Nares Strait, located between the Arctic Islands and Greenland. Eocene fault movement along the Kaltag, Nares Strait, and De Geer (separating Greenland and Spitsbergen) transforms is regarded as complementary. The presence of Eocene thrust zones, located on the western side of Nares Strait and in western Spitsbergen, suggests that northward movement of the Greenland plate formed both the transforms and the thrust belts.