Reconnaissance composition of river sand from northern South Island, New Zealand: a modern analogue for southern Taranaki Basin

The composition of 20 modern sand samples (18 streams, one beach, and one lakeshore) collected from the northern South Island provide a dataset for assessing detrital signatures of Paleozoic-Mesozoic basement terranes that may have served as sediment sources for reservoir sandstones in the Taranaki Basin. Non-plutonic terranes produce lithic-rich sand dominated by metamorphic fragments. Samples derived from erosion of the Rakaia and Caples terranes are more quartz-rich than the other non-plutonic terrane samples. Sand from the Dun Mountain-Maitai and Brook Street terranes has the lowest quartz content and is further distinguished by detrital serpentine. Pervasive pumpellyite-bearing metamorphic lithic fragments characterise the Caples, Dun Mountain-Maitai and Brook Street terranes. Feldspar is rare in Eastern province terrane sand. Sand from the Median Batholith tends to have less quartz than sand from the Karamea Batholith and a higher percentage of plagioclase, while sand from the Karamea Batholith has a higher proportion of potassium feldspar. Petrographic analyses were compared with published reports describing the composition of offshore sandstone reservoirs to evaluate their likely provenance.