Evolution of the southern termination of the Taupo Rift, New Zealand

Abstract

To understand the tectonic evolution of the southern termination of the Taupo Volcanic Zone (TVZ), New Zealand, we compare the late Quaternary structure and kinematics of the southern part of the Taupo Rift or Taupo Fault Belt (Mt Ruapehu Graben) with central parts of the rift (Ngakuru Graben), and with the South Wanganui Basin. We also investigate the differences between displacements of Pliocene and late Quaternary markers within the southern Taupo Rift. Comparison of fault displacement rates derived from displacements of late Quaternary and Pliocene markers yields a preliminary estimate of <400 000 yr for fault initiation of the majority of faults in the southern Taupo Rift. The timing of the onset of faulting in the southern TVZ appears to be younger than central parts of the TVZ and may indicate a step-wise southward propagation of the rift. Faulting also appears to be less evolved in the south than in the central parts of the Taupo Rift (thicker seismogenic crust and hence wider fault spacing), reinforcing the impression of a recent incremental propagation of the Taupo Rift to the south. The onset of faulting coincides with independent observations of the initiation of volcanism in the southern TVZ. We propose that the termination of the TVZ, geographically short of the limit of the Hikurangi margin, may only be temporary, and it is most likely to propagate southward in association with future major perturbations in the subduction margin, such as the occurrence of large ignimbrite volcanism.

Late Quaternary geometry and kinematics of faults at the southern termination of the Taupo Volcanic Zone, New Zealand

“…For the purpose of estimating total displacement and extension rates across the fault set we need to assign a maximum displacement rate to the Snowgrass Fault. The Quaternary traces of the Snowgrass Fault have a similar surface expression to the Karioi (0.4 mm/yr) and the Tertiary displacements (Villamor & Berryman 2006, this issue) seem similar to the Oruakukuru (0.7 mm/yr). We thus assign the maximum of these values to the maximum displacement rate for the Snowgrass Fault, that is, 0.7 mm/yr (Table 3).…”

The Erua earthquake cluster and seismic anisotropy in the Ruapehu region, New Zealand

“…[19] The Erua earthquake cluster lies around the Raurimu fault, a north-south oriented normal fault that is downthrown to the east [Villamor and Berryman, 2006]. Seismicity in the cluster does not however, seem to be generated from this fault, with earthquake locations distributed evenly around it.…”

The effect of crustal melt on rift dynamics: case study of the Taupo Volcanic Zone

“…Anomalously low-velocity mantle has been imaged below the TVZ (Reyners et al 2006;Eberhart-Phillips et al 2008) while the presence of shallower zones of partial melt in the crust has been inferred from magnetotelluric data (Heise et al , 2010Bertrand et al 2012). The locus of tectonic rifting and voluminous rhyolitic volcanism has narrowed during the c. 2 Ma evolution of the rift (Wilson et al 1995;Villamor & Berryman 2006). Extension is predominantly accommodated by normal faults within a central fault belt, although dyke intrusion is locally important within the Okataina Volcanic Centre (Seebeck & Nicol 2009).…”