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A HT Australian MT B Fault zones sample 3A
Plate strike-slip, reverse
Challenger ICSZ
Plateau HP Loca on of GSSZ
AF AF profile and J
samples 72,
A M GD 79, 22, 23,
45°S Chatham Rise 45°S Fig. 2 J
Inset
Fiordland
PT
reac vated HP
Paleozoic J
50 km boundary 8.5
8.5
SM Grebe
35 mm yr -1 A’ J 50 km

eastern limit
46°S T rench 20 12 46°S J of Paleozoic
Puysegur T rench upper crust 5-15 km (≤ 0.4 GPa) inboard Cretaceous plutons (WFO)
Gondwana margin
T r
T
Cretaceous Paleodepths
egur
168°E
167°E
15-20 km (0.42-0.58 GPa)
middle
Pacific
crust
Plate
Carboniferous plutons
35-50 km (0.95-1.4 GPa)
shear zones
lower 20-35 km (0.58-0.95 GPa) J outboard Jurassic arc Cretaceous
crust 50-65 km (1.4-2.1 GPa) Paleozoic Gondwana Hikurangi
margin Plateau
166°E 167°E 168°E
Figure 1. (A) Map of Fiordland showing the imbrication of Cretaceous lower, middle, and upper crust by Miocene reverse faults. Profile along line of
section A–A′ is shown in Figure 3. Paleodepth uncertainties are ±0.1 GPa (±3.7 km). Reconstruction of the subducting Australian Plate at 20, 12, and 7
Ma is from Sutherland et al. (2009). AF—Alpine fault; GD—Glade-Darran fault zone; HP—Hikurangi Plateau; HT—Hikurangi Trench; M—Misty fault; MT—
Mt. Thunder fault; SM—Spey-Mica Burn fault zone; PT—Puysegur Trench. (B) Map showing position of two Carboniferous crustal boundaries (black
dashed lines). The western boundary coincides with the George Sound shear zone (GSSZ) and SM fault zone. The eastern one coincides with the Grebe
and Indecision Creek (ICSZ) shear zones, and Mt. Thunder fault. WFO is Western Fiordland Orthogneiss. Locations of three pseudotachylyte samples
(22, 23, 3A) dated at 8–7 Ma shown with white stars. Dashed blue line surrounding light blue region represents high Vp (~8.5 km s ) eclogite crust at the
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base of the Hikurangi Plateau at ~100 km depth (after Reyners et al., 2017).
Cretaceous Western Fiordland Orthogneiss Rock Uplift and Topographic Growth precipitation rates (Jiao et al., 2017).
(WFO), which was emplaced mainly as Sutherland et al. (2009) documented Although Sutherland et al. (2009)
diorite into Paleozoic plutonic and the onset of rapid exhumation in SW postulated that age-elevation relationships
metasedimentary rocks at the base of a Fiordland at 25–15 Ma, coincident with and spatial variations in exhumation rates
Mesozoic arc (Bradshaw, 1990). Early the initiation of subduction south of New were caused by reverse faulting, their
petrologic investigations showed that the Zealand. During the 15–5 Ma period, relationship to specific faults was
western belt records high metamorphic zones of high exhumation rates broadened unresolvable with existing data.
temperatures (T ≥ 750 °C) and a depth of and expanded into the interior of
exposure that is unique in New Zealand Fiordland, although exhumation occurred Subsurface Imaging
(Oliver, 1976; Blattner, 1976; Bradshaw, mainly in the west. These patterns, A regional 3D seismic velocity model
1985). Approximately 35% of the WFO which include an estimated 12–15 km derived from seismic tomography studies
contains high-pressure mineral of total rock uplift, are thought to be by Eberhart-Phillips et al. (2010) has
assemblages indicative of garnet granulite, associated with the development of recently allowed geophysicists to image
omphacite granulite, and eclogite facies elevated topography. They also have the subsurface extent of the partially
metamorphism (Turnbull et al., 2010), been interpreted to result from either a subducted Hikurangi Plateau beneath
making it Earth’s largest (~4500 km ) and combination of crustal shortening and New Zealand (Fig. 1, inset) (Reyners et
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deepest (to at least 65 km) known exposure dynamic uplift above the subducting slab al., 2011; Davy, 2014). This oceanic
of lower crust from a Mesozoic continental (Sutherland et al., 2009) and/or glacial plateau formed ca. 122 Ma (Neal et al.,
arc (Ducea et al., 2015). erosion coupled with high (>8 m/yr ) 1997) and was underthrust beneath the
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