Tectonic reconstructions of New Zealand: 40 Ma to the present

Reconstructions of the New Zealand sub-continent from 40 Ma to the Present are presented. Assumptions that have constrained the model include: semi-st raight initial alignment of basement terranes and markers; Australian plate fixed; onset of Emerald Basin spreading at c. 45 Ma; and Pacific plate sub duction north of New Zealand from c. 30 Ma. Five independent, rigid, crusta l blocks are employed, including: Northland-Taranaki-western South Island ( combined), East Coast (North Island), east Nelson (Marlborough Sounds), eas tern South Island, and Fiordland. At 40 Ma the Pacific/Australian rotation pole was located close to or withi n the Wanganui region. A proto-plate boundary zone was propagating through western New Zealand, as an incipient link between Emerald Basin spreading i n the south and subduction in the northwest. Lateral offset on the Alpine F ault was initiated by c. 23-22 Ma, mainly as an effect of changing subducti on kinematics and increasing relative motion of the Australian and Pacific plates in the central New Zealand region. Extension in the south became inc reasingly oblique, whereas areas north of the Alpine Fault were affected by near-orthogonal compression. From c. 23 Ma to the Present, the foci of con traction, extension, and are volcanism in central-western New Zealand have migrated southwards, in response to progressive changes in the location, or ientation, inclination, and kinematics of the subducted Pacific plate.