Terrane accretion, production, and continental growth: A perspective based on the origin and tectonic fate of the Aleutian–Bering Sea region

Abstract

Orogenesis in the Aleutian–Bering Sea region would create an expansive new area of Pacific-rim mountain belts. The region itself formed about 55 Ma as a consequence of the suturing of a single exotic fragment of oceanic crust—Aleutia—to the Pacific's Alaskan-Siberian margin. A massive overlap assemblage of the igneous crust of the Aleutian Arc and the thick sedimentary masses of the Aleutian Basin have since accumulated above the captured basement terrane of Aleutia. Future closure of the Aleutian–Bering Sea region, either northward toward the continent or southward toward the Aleutian Arc, would structurally mold new continental crust to the North American plate. The resulting “Beringian orogen” would be constructed of a collage of suspect terranes. Although some terranes would include exotic crustal rocks formed as far as 5000 km away, most terranes would be kindred or cotetonic blocks composed of the overlap assemblage and of relatively local (100–1000 km) derivation. The Aleutian–Bering Sea perspective bolsters the common supposition that, although disrupted and smeared by transcurrent faulting, examples of kindred assemblages should exist, and perhaps commonly, in ocean-rim mountain belts.