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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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