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ABSTRACT: Northward Continental Dispersion on Opposite Flanks of the North Pacific

George W. Moore

Paleomagnetic data have long indicated that accreted terranes along the east coast of Asia and the west coast of North America were dispersed toward the north during the Cretaceous and Tertiary. Recent studies indicate that this dispersion usually occurred during times when subduction was occurring along the adjacent continent-ocean boundary. Typical examples are Stikinia (Canada), dispersed during the Cretaceous, Japan during the Cretaceous, and Wrangellia (Canada-Alaska) during the Paleogene, all when plates in the Pacific basin were converging toward them. Hence, a modern translational tectonic model that is free from local subduction, such as at Baja California (Mexico), seems not to have been the usual setting for this type of displacement. A more appropriate structu e is the right-lateral Sumatra fault that flanks the Sunda subduction zone at the island of Sumatra, or the left-lateral Philippine fault that flanks the Mindanao subduction zone at the Philippines. In each of these examples, the incoming oceanic plate enters the subduction zone obliquely, at a proper angle to account for the sense of movement on the parallel transform fault nearby along which the dispersion occurs. The transform fault closely follows a zone of apparent weakness along the magmatic arc of the subduction zone, so ancient volcano-plutonic belts might be matched together to restore terranes dismembered in this way to their original positions.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990