New Zealand Journal of Geology and Geophysics abstracts
Miocene–Recent deformation, surface elevation, and volcanic
intrusion of the overriding plate during subduction initiation,
offshore southern Fiordland, Puysegur margin, southwest New Zealand
Rupert Sutherland
GNS Sciences
P.O. Box 30 368
Lower Hutt, New Zealand
r.sutherland@gns.cri.nz
Philip Barnes
National Institute of Water and Atmospheric Research
P.O. Box 14 901
Kilbirnie, Wellington, New Zealand
Chris Uruski
GNS Sciences
Lower Hutt, New Zealand
Abstract We analyse results of dredge sampling, a
high-resolution seismic reflection survey, and unpublished petroleum
industry data from part of the overriding continental plate of the
Fiordland subduction zone. Plate tectonic calculations show that
convergence rates have progressively increased since Miocene time, when
subduction-related processes started. An initial deformation phase was
characterised by reverse throw on pre-existing structures during the
interval 16–8 Ma. This is interpreted to be when a throughgoing
subduction interface developed, as fracture zone linkage and spreading
ridge extinction occurred south of New Zealand. A Pliocene–Quaternary
deformation phase characterised by renewed folding and reverse faulting
on structures subparallel to the plate boundary may be due to a
regional change in plate motion or the inherited geometry of the Eocene
continent/ocean transition that is obliquely colliding with the plate
boundary, or both. Initial uplift of the region south of Fiordland to
sea level was followed by c. 1800 m of subsidence at the
Snares Depression. This subsidence may have been an isostatic response
to tectonic erosion of a crustal root, or due to negative slab buoyancy
associated with greater total convergence, or both. Persistence of
Fiordland topographic elevations above sea level, and continued rock
uplift of Fiordland, is likely to be related to greater initial crustal
thickness of the overriding Pacific plate in the north, and the present
southward transition from continental collision to intra-oceanic
subduction. The locations of the first three subduction-related
volcanoes have a relationship to pre-existing faults and raise the
possibility that volcanism and deformation may be intimately associated
during subduction initiation.
Keywords Balleny Basin; Solander Basin;
subduction; dredged samples; seismic reflection
G05019; Received 9 May 2005; accepted 4 November 2005; Online
publication date 3 March 2006
New Zealand Journal of Geology & Geophysics, 2006, Vol. 49:
131–149
0028–8306/06/4901–0131 © The Royal Society of New Zealand 2006
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