Kermadec arc—New Zealand tectonic confluence

Abstract

The transition in tectonic style from that of the Kertnadec island arc to that of continental crust in New Zealand has been ascribed, in global tectonic schemes, to the reduction of “shortening” rate as the pole of rotation between the Australian and Pacific crustal blocks is approached. However, the recognition of a west-facing island arc south of New Zealand and of widespread Quaternary crustal shortening within the New Zealand continental crust leads to the conclusion that the differing tectonic styles reflect instead the variation in mechanical response of oceanic and continental crust. The Alpine Fault is not considered to be a trench-trench transform because it parallels and co-exists with island arc features. Displacement of the early Tertiary Vening Meinesz fracture zone by the Alpine Fault indicates 70 km of late Tertiary-Quaternary horizontal motion along this fault. It is possible that the rest of the 500 km displacement along the South Island trace occurred during the late Mesozoic when the fault was a trench-trench transform between oppositely facing arcs in Northland and the Campbell Plateau.