Uplift history of south westland using the fission-track dating technique

Abstract

Apatite and zircon fission-track ages have been determined for rocks at varying distances from the Alpine Fault in SouthWestland. Zircon ages between and within samples are widely scattered and are nowhere younger than Late Cretaceous, implying thatburial has been no greater than about 7 km since that time. Apatite ages, particularlythose close to the Alpine Fault, are dominantly Late Tertiary-Quaternary; such ages imply burial to depths >3 km prior to uplift. Three samples more than 10 km from the fault have mixed apatite ages; they most likely represent an uplifted, partially annealed zone from burial depths of 3 km. Uplift rates are maximum about 2 mm/acloseto the fault and 1 mm/a along the coast. Theserates are consistent with thosepreviously determined from raised late Quaternary river-terrace levels. © 1990 Taylor & Francis Group, LLC.