New Zealand Journal of Geology and Geophysics abstracts
Evolution of the southern termination of the Taupo Rift,
New Zealand
P. Villamor
K. R. Berryman
GNS Science
P.O. Box 30 368
Lower Hutt, New Zealand
p.villamor@gns.cri.nz
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.
Keywords normal fault; slip rate; displacement
rate; extension; earthquakes; active tectonics; Taupo Fault Belt; Taupo
Volcanic Zone; Taupo Rift; fault propagation; rift evolution
G05023; Received 24 May 2005; accepted 9 September 2005; Online
publication date 28 February 2006
New Zealand Journal of Geology & Geophysics, 2006, Vol. 49:
23–37
0028–8306/06/4901–0023 © The Royal Society of New Zealand 2006
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