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

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.

本研究基于晚白垩世河流相拉科皮（Rakopi）组、边缘海相北角（North Cape）组以及古新世河流相费尔韦尔（Farewell）组的砂岩与砾岩物源分析，对塔拉纳基（Taranaki）盆地南部的古地理与构造模型进行了精细化修正。上述同裂谷沉积受作为帕卡沃次级地堑（Pakawau Sub-basin graben）东侧边界的瓦卡马罗马（Wakamarama）断层控制。北角组与费尔韦尔组的砾岩以变沉积岩碎屑为主，其岩石学与地球化学特征与塔卡卡地体（Takaka Terrane）一致；此外还包含少量塔卡卡地体火山岩、分离点套（Separation Point Suite）花岗岩类以及未知A型花岗岩。该套砂岩的物源同样源自塔卡卡地体与分离点套岩体，这表明整套沉积的物源来自东侧，沉积物经瓦卡马罗马断层注入盆地，与此前认为其轴向水系来源于南部布尔（Buller）地体的研究结论相悖。费尔韦尔组的不稳定组分向上层序逐渐减少，反映随着裂谷作用停息，化学风化作用持续增强。