PAN-PACIFIC TECTONICS

The Pan-Pacific region generally comprises two areas, the Western Pacific and the Eastern Pacific. In the Western Pacific, oceanic island arcs lie both east and west of active marginal basins. Subduction zones dip west (e.g., most of Japan, Philippines, Tonga-Kermadec, Izu-Bonin-Marianas, New Zealand) east (Halmahera, Honshu, West Luzon, Macquarie), northeast (Vanuatu-Solomon), north (Indonesia, New Britain-New Ireland). Active marginal basins include the Lau-Havre and Mariana troughs, and the Fiji and Caroline basins. Island arc-island arc collisions include Japan-Izu-Bonin, Japan-Kuriles, Sangihe-Halmahera. Active island arc-continent collisions include China-West Luzon (Taiwan); and Australia-Indonesia-New Britain (New Guinea). Active and recent subduction flips include New Guinea, Honshu, and the Solomon-Vanuatu subduction zone. Active tectonics include collisions, subduction polarity flips, large-scale strike slip faults, oroclinal bends, and rapid changes in plate configuration.

Transform faulting and eastward-subduction currently dominate the eastern Pacific. However, oceanic island arcs, at least one extensive ribbon continent, and island arc-continental margin collisions likely were present in the Mesozoic Eastern Pacific. The west-dipping Caribbean and Scotia arcs may be remnants of Pacific-originated island arc-subduction complexes. Ophiolites and sutures (scars of disappeared oceans) abound in both the western Pacific and in eastern Pacific collided terranes. The Mesozoic Eastern Pacific region probably resembled the modern Western Pacific.

Remnants of Paleozoic-Mesozoic intraoceanic island arcs, oceanic regions, and microcontinents--originally within Panthalassa--now are present as accreted fragments around the entire Circumpacific orogen.