Southern Alps Faults, Cox et al.
AUXILIARY MATERIAL
The Textural Zone Classification Scheme
Rocks in the Southern Alps have been mapped and classified on the basis of a textural zone
classification scheme that is widely applied in New Zealand [Figure 3; Cox and Barrell, 2007;
Turnbull et al., 2001]. Textural zone 1 (TZ1) rocks retain their sedimentary (primary)
appearance, detrital grain texture is preserved, and bedding (when present) dominates
outcrops. Metamorphic minerals may be present, but are very fine grained (<0.075 mm), and
there is no metamorphic fabric. TZ2A rocks retain their primary appearance and sedimentary
texture, but detrital grains are flattened. Metamorphic minerals are fine grained (<0.075 mm)
and impart a slight cleavage to sandstones. Mudstones have slaty cleavage. Bedding (where
present) and metamorphic cleavage are equally predominant in outcrop, although bedding is
commonly transposed. Textural zone 2 rocks have a cleavage (TZ2A weaker than TZ2B), and
textural zone 3 and 4 rocks have a thinly (1-2 mm, TZ3) to thickly (>2 mm, TZ4) segregated
foliation and relatively coarse mica grain size.
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Southern Alps Faults, Cox et al.
Tables
Table S1 Summary section describing key elements of the zone of faults exposed beneath the
Main Divide in the west wall of Hooker Valley, including the Black Blob Fault. Well-exposed
reference localities are 170.10173E 43.66378S [Figure 4B] and 170.11067E 43.63249S
[Figure 4C].
Hanging wall
Pumpellyite-actinolite facies sandstone and argillite, bedding orientation relatively
constant with mean strike/dip = 192/47ºW [Figure 4D, E stereonets], but numerous
intraformational isoclinal folds and local penetrative cleavage occur. Abundant 110 m scale faults and fractures, with quartz-chlorite and quartz-carbonate fibres or
striations indicating dextral oblique-slip [Figure 4D; Cox and Findlay, 1995].
Some km-scale, bedding-parallel, argillite-rich faults.
Clay-rich gouge
0.01-1m
Soft, clay-rich, planar fault gouge and fault-breccia, locally altered from gray to
light-cream colour. Composed of interlayered muscovite/illite, smectite/illite, with
lesser ankerite/siderite, calcite, lepidocrocite (hydrous iron oxide), and
stilpnomelane. Quartz only present in the coarse (>2 µm) fraction of the fault
gouge. Gouge poorly exposed – coincides with a prominent scree-covered ledge.
Striations on margin of gouge difficult to find and observe. Clay-sized fraction of
gouge is 20-30% by mass.
Cataclasite Zone
10-50 m
Zone containing irregular, folded- or lensoid-shaped bodies of dark, black
cataclastic argillite in green to green-brown cataclastic sandstone and weakly
brecciated sandstone. Bedding is discontinuous, truncated and offset by numerous
small-scale faults and shears, commonly with striated chlorite-rich fibres
[measurements included in Figure 4D]. Clay-sized fraction 6-10% by mass.
Black Blob Fault
Hard flinty, dark black, silicified argillite with an anastomosing phacoidal shear
fabric. Contains shears of ultracataclasite, layers and lenses of disrupted
(boudinaged) siltstone and sandstone. Shear-surfaces are mostly matt, but highly
polished, reflective, surfaces are common near the basal surface. Composed of
clay-sized muscovite/illite, chlorite, and accessory ankerite/siderite, lepidocrocite
(hydrous iron oxide), gypsum, zeolite, pumpellyite, quartz, feldspars and
interlayered chlorite/smectite. High silica content (66-78% SiO2) suggest
silicification or incorporation of chert into the dark, fine-grained fault material.
Clay-sized fraction 4% by mass.
Argillitic-shears and
basal fault surface
1-2 m
Foot wall
Prehnite-pumpellyite facies medium-bedded sandstone and minor argillite. Handspecimens have abundant, small, healed brittle micro-fractures and are commonly
altered with white zeolites and cross-cut by prehnite veins. Bedding predominantly
dips west, but varies locally about steeply plunging folds [Figure 4A stereonet].
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Southern Alps Faults, Cox et al.
Table S2 Summary section through the faults on the western side of Murchison valley.
Hanging wall
>3 km
Prehnite-pumpellyite facies sandstone and minor argillite, alternating in turbidite
sequences. Bedding facing mostly north, but locally folded about macroscopic
steeply plunging folds [Lillie, 1962]. Bedding strikes NW-SE at the range crest,
but NE-SW near the faults. Red argillite containing Atomodesma fragments
indicates some strata are Permian, intercalated within Triassic rocks [Waterhouse,
1985, 1987].
Fault
Oriented 220/45ºW, based on structure contours generated from fault trace
mapping. Fault rocks and/or gouge are approximately 10- 20 m wide, but have not
been inspected in detail.
TZ2A belt
700 m
Moderately-dipping belt of cleaved, TZ2A, sandstone and argillite, prehnitepumpellyite facies. Bedding is homoclinal, with mean orientation 238/47ºW.
Murchison Fault
Exposed approximately 200-400m above Murchison valley floor. Oriented
225/50ºW at the northern end, 235/70ºW at the south. Zone up to 50 m wide.
Striations at 170.32393E -43.59083S range between 275/40º and 295/50º.
Footwall
Prehnite-pumpellyite facies massive sandstones and volcanogenic sandstone,
minor argillite and black mudstone. Some mesoscopic folding, bedding mean
orientation is 233/68ºW.
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Southern Alps Faults, Cox et al.
Table S3 Summary section through the Liebig Fault at 170.36961E 43.69366S on western
side of Cass valley.
Hanging wall
>3 km
Greywacke and argillite, TZ1 prehnite-pumpellyite facies, with steeply-dipping
bedding folded about 500 m – 1 km wavelength folds. Cleavage locally developed
in argillite, parallel to the fold-axial surface.
Fracture-zone
Irregular ‘knobby’ outcrops of sandstone and argillite traversed by a dense array of
extremely close small-scale fractures and abundant carbonate veins.
Milled-cataclasite
2-3 m
Carbonate matrix-supported breccia with sub-rounded fragments of sandstone
[Figure 5B]. Passes gradationally into fracture zone above. Mineralogy includes
clay-sized illite, chlorite, calcite, Ca-smectite, wairakite, lepidocrocite (hydrous
iron oxide) and basaluminite – the latter four minerals interpreted to be newly
grown due to fluid circulation associated with fault movement.
Dark cataclasite
150 mm
Dark, welded, aphanitic argillitic cataclasite and ultracataclasite [Figure 5C].
Cleaved parallel to the fault, but containing secondary fractures at a low-angle to
the fault. Contains thin horizons of disrupted sandstone, which that have been
offset and provide small-scale reverse slip indicators.
Liebig Fault
basal fault plane
<5 mm
Thin-layer of clay coating a hard, polished surface of cream- or grey-coloured
cataclasite. Fault plane 195/65ºW with slickensides 295/60º-300/55º.
Footwall
Greywacke and argillite, TZ1 prehnite-pumpellyite facies, with northwards facing
steeply-dipping bedding folded about a broad, >3 km wavelength syncline. Within
50 m of the fault, sandstones are green-brown, altered with chlorite- and zeoliteveins, and contain abundant healed microfractures.
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Southern Alps Faults, Cox et al.
Figures
Figure S1 Faults exposed in the west wall of Tasman valley. (A) Panorama looking northwest
at Aoraki/Mt Cook, Mt Tasman, Grand Plateau and Haast Ridge, outlining the location of
major faults (white dashes are accurate/well-defined, black with “?” under snowfields are
inferred). Photo: L. Homer/GNS Science CN35886. (B) View southwest at 170.15847E 44.48596N along the Haast Ridge Fault. The prominent fold in the footwall is approx. 10 m
across. Photo: S. Cox. (C) Unweighted kinematic analysis of striated fractures in the Haast
Ridge Fault hanging wall damage zone (n=26). Measurements were made <150 m from the
fault, mostly within the field of view in photo B or on the ridge from where the photo was
taken. (D) Stereonet showing the orientation of the Haast Ridge Fault, measured slip
directions, bedding in the hanging wall and footwall, and unweighted kinematic analysis of
fault slip (n=6).
Figure S2 Photograph looking westwards across the northern end of Liebig Range towards
Murchison valley, Malte Brun Range and Aoraki/Mt Cook (distant background). Faults with
soft clay-rich gouge are highlighted with white dotted lines whereas other faults have white
dashed lines. Inset stereonets show kinematic analyses for the basal Liebig (LF) and
Murchison (MF) faults. Photo: S. Cox.
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