The tectonic setting of the Fiordland region, south-west New Zealand

Abstract

The Indian/Pacific plate boundary to the south-west of New Zealand has undergone highly oblique compression during the past 15 Myr. Subduction of the Indian plate north-eastwards under the Pacific plate has probably occurred at Puysegur Trench, south of New Zealand, for most of this period. In contrast, subduction at the plate boundary through south-west New Zealand (Fiordland) has only occurred during the last 7 Myr when oceanic lithosphere of the Indian plate has been adjacent to the continental lithosphere of Fiordland (Pacific plate). Transcurrent motion at the plate boundary during this time has transferred the continental lithosphere forming Challenger Plateau on the Indian plate northwards relative to southern New Zealand. Most geophysical features of the Fiordland region can be accounted for in terms of this recent subduction event at the Fiordland margin. However, the intermediate depth seismicity appears to arise from a fragment of the Indian plate, subducted at Puysegur Trench and subsequently moved northwards by the transcurrent motion between the two plates.