2023 CSDMS meeting-076
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Tectonic geomorphololgy of a plate boundary transfer zone though central Aotearoa New Zealand
Phaedra Upton,
GNS Science Lower Hutt , New Zealand. p.upton@gns.cri.nz
Andy Tulloch, GNS Science Dunedin , New Zealand.
James Crampton, Victoria University of Wellington Te Herenga Waka Wellington , New Zealand.
Alison Duvall, University of Washington Seattle Washington, United States.
Analysis of topography can reveal signals resulting from both past and currently active tectonic regimes. In central Aotearoa New Zealand today, the Marlborough faults transfer plate boundary motion from the Hikurangi subduction zone to the highly oblique Alpine fault. The rocks of the Marlborough region have hosted active structures since the mid-Cretaceous when they sat at the edge of the Gondwana margin. Here we use tectonic geomorphology in conjunction with geological observations to unravel the long-term tectonic history of this plate boundary transition zone with emphasis on variations along and across strike, with depth and in time. To understand the active deformation occurring under the present tectonic regime, as manifested by recent complex faulting during the 2016 Mw 7.8 Kaikōura earthquake, we focus on understanding the 3D structure of the region as well as the development of, and control by, inherited structures. Cretaceous restoration of eastern Marlborough suggests that the major faults formed during extension of Te Riu-a-Māui Zealandia preceding breakaway from Gondwana. Overall, given the uncertainties of the reconstruction, the Cretaceous structural similarity of paleo-Marlborough with wider South Zealandia seems a remarkably clear and consistent match. How much of the distinctive landscape of Marlborough is due to the constraints of the current plate boundary versus the influence of tectonic inheritance?
