Triassic (map symbol T)

Distribution
Triassic rocks have a similar distribution pattern to Permian rocks in the South Island (i.e., Nelson and Southland). However, they also occur in the west of the North Island, from northern Taranaki to the Waikato River. Triassic rocks of the greywacke belt occur in Otago, Canterbury, Marlborough, the axial ranges of the North Island and Northland.

Content
The Triassic rocks are similar to the Permian rocks. Conglomerate, sandstone, and mudstone, mainly derived from volcanic rock types, are common, while tuff beds are widespread particularly in the North Island; volcanic flow rocks are rare. In places the rocks are very fossiliferous giving good age control.

The greywacke belt rocks are grey sandstone and mudstone, with minor limestone, chert, conglomerate, spilite, and melange (see Greywacke).

Paleogeographic conditions
All Triassic rocks of New Zealand are marine, with the same depositional environments and volcanic activity continuing from the Permian. Rock units with significant quantities of conglomerate indicate closeness to a land mass.

Triassic

Deformation
Triassic rocks are involved in the major downfolds of the Kawhia, Nelson, and Southland regional synclines. In Southland and Kawhia the rocks are not highly deformed, but in the main only gently folded. In Nelson the syncline is severely faulted. The greywacke rocks are also very deformed, with many crush zones and faults, and some have been metamorphosed into schist, especially in Otago and Nelson. The Otago (Haast) Schist forms a belt which crosses the southern part of the South Island from east to west, then curves north to trend northeast in a narrow wedge. Schist is also present locally near Wellington and in the Kaimanawa Mountains.