A Rb-Sr whole-rock isochron from a suite of granitoid clasts in a Late Triassic conglomerate of the Kawhia Syncline, New Zealand, yields an age of 226 ± 6 (2σ) Ma. This age falls within the range of sedimentary ages for the conglomerate (Late Carnian — Early Norian), an implies rapid uplift and erosion of the clast protolith, and rapid transport and deposition of the derived material. Petrographic, chemical and isotopic characteristics of the suite are consistent with a volcanic arc tectonic setting; a possible protolith could be a northwards continuation of the Permo-Triassic Brook Street magmatic arc.