Instability of a lithospheric step beneath western North Island, New Zealand

Abstract

Research Article| April 01, 2013 Instability of a lithospheric step beneath western North Island, New Zealand Tim Stern; Tim Stern 1Institute of Geophysics, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand Search for other works by this author on: GSW Google Scholar Gregory Houseman; Gregory Houseman 2School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK Search for other works by this author on: GSW Google Scholar Michelle Salmon; Michelle Salmon 3Research School of Earth Sciences, Australian National University, Acton, ACT 0200, Australia Search for other works by this author on: GSW Google Scholar Lynn Evans Lynn Evans 4School of Geosciences, Monash University, Clayton, VIC 3800, Australia Search for other works by this author on: GSW Google Scholar Geology (2013) 41 (4): 423–426. https://doi.org/10.1130/G34028.1 Article history received: 09 Sep 2012 rev-recd: 15 Oct 2012 accepted: 18 Oct 2012 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Tim Stern, Gregory Houseman, Michelle Salmon, Lynn Evans; Instability of a lithospheric step beneath western North Island, New Zealand. Geology 2013;; 41 (4): 423–426. doi: https://doi.org/10.1130/G34028.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Lithospheres of different thicknesses are often juxtaposed by movement on a continental-transform boundary. Such a boundary with a step change in densities may trigger a gravitational instability as lateral pressure gradients are created where normal mantle lithosphere terminates against less dense asthenospheric mantle. Here we show, for plausible values of the lithospheric viscosity, a mechanism by which the thicker mantle lithosphere will drip off into the lower density asthenosphere. As the mantle deforms it also progressively thickens and then thins the overlying crust, creating a topographic wave that migrates in concert with the removal of mantle lithosphere. Within western North Island, New Zealand, geophysical data define a sharp lithospheric step across the Taranaki-Ruapehu line, and geological observations provide a history of uplift and subsidence that has propagated southward in the past 12 m.y. The rate of observed north to south migration of the wave (∼30 mm/yr), its wavelength (∼250 km), and amplitude (∼±1 km) are compatible with it being caused by progressive removal of mantle lithosphere, if the viscosity of the uppermost lithospheric mantle is ∼5 × 1020 Pa·s, providing one of the clearest examples yet of this fundamental geological process. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.