Magnetic lineations in marginal basins of the western Pacific

Abstract This paper separates the small oceanic basins around the western perimeter of the Pacific Ocean into marginal basins that have formed through back-arc extension and those that apparently have not, and reviews our knowledge of magnetic lineation patterns observed in possible and probable back-arc basins. Magnetic lineations in these basins resemble lineations commonly associated with the world’s mid-oceanic spreading systems, indicating that similar processes of crustal accretion occur in both tectonic environments. In some back-arc basins of the southwestern Pacific, magnetic lineation and other evidence suggest that back-arc basins can evolve through the interaction and growth of ‘multi-plate’ systems. Because of the small time and space characteristics of back-arc basins compared with the world’s major oceanic spreading systems, tectonic conditions favourable for the generation of back-arc basins are either relaxed rapidly or easily interrupted. Models proposed to account for back-arc basin development include (a) ‘local’ models, where back-arc extension is mechanically driven by the downgoing slab, and (b) global plate kinematics models, where conditions favourable for back-arc extension are governed by the motion of the overriding plate relative to the trench axis.