Provenance of the Pakawau Group and Farewell Formation (Late Cretaceous - Paleocene), Taranaki Basin, northwest Nelson, New Zealand

摘要

Paleogeographic and tectonic models for the southern Taranaki Basin are refined with sandstone and conglomerate provenances determined from the Late Cretaceous fluvial Rakopi, marginal marine North Cape and Paleocene fluvial Farewell formations. These syn-rift deposits were controlled by the Wakamarama Fault, which bounds the eastern side of the Pakawau Sub-basin graben. The conglomerates of the North Cape and Farewell formations are dominated by metasedimentary clasts with petrography and geochemistry consistent with the Takaka Terrane; minor Takaka Terrane volcanics; and minor Separation Point Suite granitoids and an unknown A-type granite. The sandstones have Takaka Terrane/Separation Point Suite provenance. This indicates that the deposits were sourced from the east with sediments fed into the basin from the Wakamarama Fault, in contrast to previous works indicating axial drainage and southern Buller Terrane provenance. The Farewell Formation has decreasing labile components up-section, indicating increased chemical weathering with the cessation of rifting.