Fission-track age of the Mangaroa Ash and tectonic implications at Wellington, New Zealand

Abstract

Three samples of zircon from the Mangaroa Ash, an important marker bed in the late Pleistocene deposits of the Wellington area, have been dated by fission-track analysis. The average age of the 3 zircon samples is 380 000 years. Since this tephra fell, vertical uplift at Tinakori Hill on the northwest side of the Wellington Fault has been about 266 m, at a rate of about 69 cm per 1000 years; at the Whakatiki Terraces the minimum rate of uplift on the northwest side of this fault has been about 21 cm per 1000 years.