Basement geology of Taranaki and Wanganui Basins, New Zealand

Abstract

We present a revised interpretation of the basement geology beneath Late Cretaceous to Cenozoic Taranaki and Wanganui Basins of central New Zealand, based on new petrographic, geochemical, and geo‐chronological data from 30 oil exploration wells. Recently published structural and magnetic interpretations of the area assist in the interpolation and extrapolation of geological boundaries. Torlesse and Waipapa Terranes have been identified in Wanganui Basin, and Murihiku Terrane in eastern Taranaki Basin, but Maitai and Brook Street Terrane rocks have not been recognised. Separation Point Suite, Karamea Suite, and Median Tectonic Zone igneous rocks are all identified on the basis of characteristic petrography, geochemistry, and/or age. SHRIMP U‐Pb zircon measurements on igneous samples from western Taranaki wells do not give precise ages but do provide useful constraints: Motueka‐1 granite is latest Devonian — earliest Carboniferous; Tangaroa‐1 and Toropuihi‐1 are Carboniferous; and Surville‐1 is Cretaceous (cf. Separation Point Suite). Our interpretation of sub‐basin geology is compatible with previously observed onland relationships in the North and South Islands.

Keywords:

• North Island
• Taranaki
• Wanganui
• Eastern Province
• Western Province
• Median Tectonic Zone
• terranes
• granitoids
• petrology
• petrography
• geochemistry
• U‐Pb dating
• zircon