CIRCUM-NORTH PACIFIC OROGENS: FORMATION OF A TERRANE COLLAGE Available to Purchase

The Circum-North Pacific orogens make up a collage of terranes that are fragments of island arcs, active and passive continental margins, accretionary complexes, or cratons. The formation of the Mesozoic and Cenozoic orogens was controlled by convergent motions of oceanic (paleo-Pacific) and continental (North American and North Asian or Siberian) plates accompanied by rifting and by opening and closure of small ocean basins behind active continental margins and island arcs. Various systems of island arcs and active continental margins of different ages, extending for thousands of kilometers, are common in North America and northeastern Asia, similar to those now existing on the Pacific periphery. The fragmentation of major tectonic units (island arcs etc.) was either syn- or postaccretional, the latter chiefly resulted from large-magnitude strike-slip motions on faults roughly parallel to the continent-ocean boundary. A tectonic interpretation is illustrated by a set of palinspastic maps built on previous analysis of terranes, including overlap and suture complexes, and critically reviewed published paleomagnetic and paleobiogeographic data for the Russian Far East, Alaska, the Canadian Cordillera, and Hokkaido (Japan).