Silurian (map symbol S)

Distribution
Silurian rocks occur in Nelson, Stewart Island and probably in Fiordland.

Content
Silurian rocks are dominantly quartzite, with minor argillite and limestone. The equivalent metamorphic rocks known from Nelson and Stewart Island are schist, gneiss and amphibolite.

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.

Deformation
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.