Map-view restorations of the South Island, New Zealand: a reappraisal of the last 10 Myr of evolution of the Alpine and Wairau faults

ABSTRACT

Retro-deformation of horizontal and vertical displacements is used to reconstruct the evolution of the South Island plate boundary faults since the Late Miocene. Finite dextral offset across the Alpine Fault is estimated from a system of N-S reverse faults displaced from Otago to the Glenroy-Matakitaki area, where the N-S tectonic trends are generally interpreted as a ‘bend’ of the Alpine Fault. Increasing dextral offset on the Alpine Fault was accompanied by a NE-migrating wave of exhumation and uplift of its hanging wall, tracked by syntectonic terrestrial deposits. Strike-slip and dip-slip components both decrease near the ‘bend’, where deformation is transferred to the Wairau and Marlborough faults. The Wairau Fault offsets dextrally by c. 50 km the N-S faults of the Glenroy-Matakitaki area, correlated with the Waimea-Flaxmore Fault System of Nelson. Finite dextral separation along the Alpine Fault is 410 km, and the N-S ‘bend’ is interpreted as a transpressive stepover between the Alpine and the Wairau faults. The lack of connection between the Alpine and Wairau faults, combined with slip transfer to the Hope Fault over the last 2 Myr, do not favour propagation of coseismic rupture from the Alpine Fault to the Wairau Fault across the ‘bend’.

KEYWORDS:

• New Zealand
• Alpine Fault
• Wairau Fault
• Marlborough faults
• transform margin
• restoration
• slip rate
• exhumation
• uplift
• terrestrial deposits

Acknowledgements

Discussions with P. Barnes, N. Barth, M. Beggs, D. Craw, D. Eberhart-Phillips, M. Johnston, K. Lang, N. Mortimer, A. Nicol; J. Pettinga, U. Ring and P. Wopereis on various aspects of this paper are gratefully acknowledged, but inferences and conclusions are the sole responsibility of the author. R.H. Sibson is thanked for his comments on a pre-submission draft. D. Craw and H. Seebeck are gratefully acknowledged for their reviews and suggestions.

Data availability statement

The data that support the findings of this study are openly available in Figshare at http://doi.org/10.6084/m9.figshare.13198580

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

This work was privately funded by TerraGeologica.