Devonian (map symbol D)

Devonian rocks are present in the Nelson region and near Reefton. Rocks of this age also occur on Stewart Island and probably in Fiordland. Many igneous intrusions in the South Island, from the Nelson region down to Stewart Island, are of Devonian age.

Devonian rocks are more varied than Silurian rocks, with calcareous mudstone, sandstone, and conglomerate in the northwest Nelson area. Near Reefton quartzite, limestone, and mudstone are the dominant rock types.

Large granite and granodiorite intrusions occurred in the Devonian, mainly as the Karamea Batholith in the northwest of the South Island, and also as smaller intrusions further south. South of Riwaka in the Nelson area, a basic complex of gabbro, peridotite, and diorite is of Devonian age.

Paleogeographic conditions
The Silurian and Devonian sedimentary rocks were the final deposits of the offshore trough which had existed throughout the early Paleozoic. Crustal movements generated magma which penetrated the sedimentary pile, and eventually cooled to become the large batholiths of granite, granodiorite, and diorite. The resulting pressure and heat were responsible for much of the metamorphism of the lower Paleozoic rocks.

The crustal movements in the Devonian (and continuing intermittently through to the Permian - Tuhua Orogeny) were largely responsible for the deformation of the lower Paleozoic rocks. On the whole, the Silurian and Devonian rocks were not involved in the earlier major thrusting events, but they are faulted and tightly folded.