Northern North America
Alaska is the eastern, subaerial part of a large subcontinent of distinctive tectonic character that serves as an isthmus between nuclear North America, with its fringing belt of allochthonous terranes, and the accreted terranes and volcanic belts that constitute northeastern Russia. Physiographically, this subcontinent, which we name Denalia, is a bulge in the continental platform in the vicinity of Alaska, the Chukotsk Peninsula, and the broad continental shelf of the Bering Sea. The bulge is convex to the south and is bounded on the east and west by constrictions in the width of the continental platform and on the north and south by the edge of the continental shelf (Fig. 1). Tectonically, Denalia is characterized by geologic youthfulness and complexity, an abundance of convergent and transcurrent faults, and absence of autochthonous cratonic rocks. It contains a profusion of lithotectonic terranes of diverse origin and age that were emplaced in late Mesozoic and Cenozoic time. In addition, it includes the superimposed Cenozoic Aleutian arc and subduction zone and the Queen Charlotte-Fairweather transform fault system. Parts of Denalia were created by pre-middle Mesozoic tectonic events, but these took place elsewhere, before the affected rocks were tectonically transported and incorporated into the landmass of Denalia. Except for a small area in the Porcupine Plateau region along the Alaska-Yukon boundary, the only Precambrian rocks that have been recognized in the subcontinent are in tectonically emplaced fragments, the largest of which is the Arctic Alaska terrane in the Brooks Range, Arctic Foothills, and Arctic Foothills
Figures & Tables
This volume presents syntheses in twelve chapters of the tectonic evolution of continent-ocean transitions of North America (Canada-Mexico-U.S.A.) since the Precambrian. The syntheses are interpretations based on the 19 continent-ocean transects across North American margins published by GSA as part of its Decade of North American Geology (DNAG) series. The transitional region is the part of North America between the craton, little deformed in Phanerozoic time, and the modern ocean basins. The region developed heterogeneously within plate boundary zones that led to sequences of passive, collisional, and active margins that differ place to place. Nine chapters address individual segments of the transitional region, two consider active and passive margin tectonics topically, and one treats the evolution of Phanerozoic transitions of North America as a whole.