Cenozoic bending of New Zealand basement terranes and Alpine Fault displacement: A brief review

Sutherland, Rupert

doi:10.1080/00288306.1999.9514846

Cited by 149 publications

(183 citation statements)

References 33 publications

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“…Hobbs et al, 2002), a zone of enhanced ductile creep will propagate downwards from the upper crustal fault and a positive feedback loop will lead eventually to a highly focussed fault zone through the crust. Associated with this, pronounced exhumation during localised uplift on the fault will also result in focussed thermal weakening (Ellis et al, 2001;Koons et al, 2003) In the early history of the plate boundary, deformation was distributed across a broad region rather than focussed on the Alpine fault (Sutherland, 1999). The discontinuity that localised the Alpine Fault was the old passive margin along the Resolution Ridge (Sutherland et al, 2000).…”

Section: Discussionmentioning

confidence: 99%

Strain localisation within ductile shear zones beneath active faults: The Alpine Fault contrasted with the adjacent Otago fault system, New Zealand

Norris

2014

Earth Planet Sp

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The Alpine Fault accommodates around 60-70% of the 37 mm/yr oblique motion between the Australian and Pacific plates in the South Island of New Zealand. Uplift on the fault over the past 5 Ma has led to the exhumation of the deep-seated mylonite zone alongside the present surface trace. Shear strain estimates in the mylonites reach 200-300 in the most highly strained rocks, and provide an integrated displacement across the zone of 60-120 km. This is consistent with the amount of displacement during the last 5 Ma, suggesting that displacement on the fault is localised within a 1-2 km wide ductile shear zone to depths of 25-30 km. Existing geodetic data, together with Late Quaternary slip rate and paleoseismic data, are consistent with the steady build-up and release of elastic strain in the upper crust driven by ductile creep within a narrow mylonite zone at depth. Faults of the Otago Fault System form a parallel array east of the Alpine Fault and accommodate c. 2 mm/yr contraction. Long periods of quiescence on individual structures suggest episodic, or "intermittently characteristic", behaviour. This is more consistent with failure on faults within an elastico-frictional upper crust above a ductile lower crust. Localisation of crustal deformation may be initiated by inherited weaknesses in the upper crust, with downward propagation of slip causing strain weakening within the ductile zone immediately beneath. Inherited structures of great length focus a greater amount of displacement and hence more rapidly develop underlying zones of ductile shear.

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Section: Discussionmentioning

confidence: 99%

Strain localisation within ductile shear zones beneath active faults: The Alpine Fault contrasted with the adjacent Otago fault system, New Zealand

Norris

2014

Earth Planet Sp

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“…Mortimer 2004). The Alpine Fault has offset these geological terranes by about 460 km from the northeast to the southwest (Carter & Norris 1976;Sutherland 1999) and has juxtaposed the Eastern and Western Provinces in the Whataroa region. The Whataroa seismic profile extends across the Alpine Fault from the Eastern Province (Pacific Plate) to Western Province (Australian Plate) rocks.…”

Section: Introductionmentioning

confidence: 99%

Crustal seismic reflection profile across the alpine fault and coastal plain at Whataroa, South Island

Davey

2010

New Zealand Journal of Geology and Geophysics

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Crustal seismic reflection data recorded across the Alpine Fault and coastal plain at Whataroa in 1998 are used to derive shallow (4 seconds two-way time or s twt) and deep (14 s twt) seismic reflection images and a simple refraction model. A single 25 km long, 636 channel receiver array recorded energy from 50 kg shots fired at 1 km intervals with intervening shots of 2.5 kg at about 300 m intervals along the profile. Record quality varied from good to poor. Across the Alpine Fault, basement lies at about 300Á500 m (0.2Á0.5 s twt), and a weak basement reflection may be attributed the Alpine Fault. Basement deepens sharply at about 6 km to the northwest of the fault, and a 3 km section of probably Miocene and younger sediments is imaged to the northwest. The southern boundary of the coastal basin probably corresponds to the South Westland Fault. The deeper section images a distinct band of strong reflectivity at a depth of about 9Á10 s twt, the base of which is inferred to be Moho. Depth conversion gives a horizontal Moho across the whole profile at a depth of about 27 km.

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“…1), and more diffuse shearing northwest and southeast of the fault. This shearing is reflected by the bending of belts of rock (terranes) (Sutherland, 1999), and internal rotations shown by paleomagnetic declination anomalies (Mumme and Walcott, 1985).…”

Section: Tectonic Settingmentioning

confidence: 99%

“…Since 45 Ma the South Island has undergone dextral shear with displacements of 850 km (±100 km) (Sutherland, 1999). Its manifestation in crustal rocks include ∼460 km of slip on the Alpine fault (Fig.…”

Section: Tectonic Settingmentioning

confidence: 99%

Structure and strength of a continental transform from onshore-offshore seismic profiling of South Island, New Zealand

2014

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Seismic images of deformation beneath South Island, New Zealand, are provided by a form of seismic exploration uniquely suited to the study of "continental islands"-double-sided, onshore-offshore seismic methods in conjunction with onshore refraction and teleseismic P-wave delay data. Four sets of independent observations and analysis are use to infer rock properties within this plate boundary zone: seismic and electrical indications of highfluid pressures within the crust; P-wave delays from teleseismic anisotropy to show a high-speed zone in the mantle directly below the crustal root; Pn anisotropy of 11 ± 3% distributed over a region > 100 km-wide; and an effective elastic thickness (Te) that is vanishingly small beneath the Southern Alps and surface outcrop of the Alpine Fault, but increases to values of Te > 20 km beyond the coastlines of the South Island. Together, these observations show that deformation in the crust and mantle becomes progressively wider with depth. A region of distributed deformation > 200 km wide is inferred for the upper mantle. We propose that the weakness and the wide zone of deformation are phenomena of plate boundaries where both strike-slip and convergence have persisted for several millions of years.

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Cenozoic bending of New Zealand basement terranes and Alpine Fault displacement: A brief review

Cited by 149 publications

References 33 publications

Strain localisation within ductile shear zones beneath active faults: The Alpine Fault contrasted with the adjacent Otago fault system, New Zealand

Strain localisation within ductile shear zones beneath active faults: The Alpine Fault contrasted with the adjacent Otago fault system, New Zealand

Crustal seismic reflection profile across the alpine fault and coastal plain at Whataroa, South Island

Structure and strength of a continental transform from onshore-offshore seismic profiling of South Island, New Zealand

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