Thermo-tectonic History of the Marlborough Region, South Island, New Zealand

Abstract

Apatite fission track analysis has been used to study the thermal and tectonic history of the Marlborough Region, South Island, New Zealand. The very young ages (<10 Ma) of apatite in the vicinity of the Alpine Fault bend and Seaward Kaikoura Range, are consistent with the recent rapid uplife/erosion in these areas. Most of the apatite ages are younger than depositional ages, indicating that the host rocks in Marlborough have experienced exposure to temperatures in the zone of partial annealing for apatite. In addition, apatite ages obtained along the Wairau Fault are always younger than those of other areas. Apatite fission track ages and mean lengths show that there are two major cooling events. one occurring from the early Miocene (~20 Ma) and the other in the mid-Cretaceous (~100 Ma). Modeled thermal histories of eleven samples selected from Marlborough samples are consistent with the stratigraphic record and reflect that in the Wairau block the timing of the main Neogene uplift/erosion event is earlier (mid to late Miocene) than to the southeast in the Seaward Kaikoura Range (late Pliocene-Pleistocene).

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