Carboniferous (map symbol C)

The only known Carboniferous fossil localities occur in sedimentary rocks in south Canterbury and north Otago, within the greywacke. Several of the granite plutons mapped on Stewart Island are also of this age, but they are not shown separately on the map.

Greywacke consists of hard grey sandstone and darker coloured mudstone (argillite). These generally form alternating sequences with the sandstone predominant. In southern Canterbury, the Carboniferous fossil locality is in limestone within a melange unit. In north Otago, Carboniferous fossils have been recorded from interbedded marble and chert.

On Stewart Island, granite and granodiorite, together with foliated rocks of similar compositions (gneisses) occur among much younger intrusive rocks.

Paleogeographic conditions
Carboniferous sedimentary rocks were deposited in a marine environment, possibly in an enormous submarine trough or series of basins.

The greywacke rocks are commonly extremely deformed, fractured, and veined, and in some areas it is difficult to see original sedimentary features because of this severe deformation.