Geology of New Zealand - Separation From Gondwana

Separation From Gondwana

New Zealand and New Caledonia represent the visible part of a portion of continental crust, usually referred to as Zealandia. The rest of Zealandia includes the Challenger Plateau and Lord Howe Rise, which stretch from Northwest of New Zealand almost to Northern Australia, and the Campbell Plateau and Chatham Rise, to the southeast of New Zealand.

The Australia-New Zealand continental fragment of Gondwana split from the rest of Gondwana in the late Cretaceous time (95-90 Ma). Then around 83 Ma, Zealandia started to separate from Australia forming the Tasman Sea, initially separating from the south. By 75 Ma, Zealandia was essentially separate from Australia and Antarctica, although only shallow seas might have separated Zealandia and Australia in the north. The landmasses continued to separate until early Eocene times (53 Ma). The Tasman Sea, and part of Zealandia then locked together with Australia to form the Australian Plate (40 Ma), and a new plate boundary was created between the Australian Plate and Pacific Plate. Zealandia ended up at a pivot point between the Pacific and Australian Plates, with spreading in the south, and convergence in the north, where the Pacific Plate was subducted beneath the Australian Plate. A precursor to the Kermadec Arc was created. The convergent part of the plate boundary propagated through Zealandia from the north, eventually forming a proto-Alpine Fault in Miocene times (23 Ma). The various ridges and basins north of New Zealand relate to previous positions of the plate boundary.