Evaluating the coastal deformation mechanisms of the Raukumara Peninsula, northern Hikurangi subduction margin, New Zealand and insights into forearc uplift processes

Abstract

Coastlines that trend both parallel and normal to the Hikurangi subduction margin along the Raukumara Peninsula, New Zealand, provide a globally unique situation that enables study of the coastal deformation and its spatial variance across and along the forearc. The data suggest there is margin-parallel zoning of the forearc deformation processes across the Raukumara segment of the Hikurangi margin. On forearc promontories closest to the Hikurangi trench (within 80 km), Holocene marine and fluvial terraces record localised zones of intermittent uplift driven by large coseismic events on landward-dipping nearshore reverse faults. At greater distances from the trench ( !100 km), Holocene and Pleistocene coastal stratigraphy and geomorphology suggest that surface uplift occurs by a gradual mechanism: either by frequent small earthquakes or by an aseismic process. In concurrence with geophysical models, we suggest the gradual uplift of this area is most likely driven by the buoyancy of underplated sediment with a contribution from subduction of the over-thickened crust of the Hikurangi Plateau. There is an intermediate zone at c. 80Á100 km from the trench that is uplifted at low to moderate rates, probably by the effects of Hikurangi Plateau subduction with some contributions from outboard upper plate faulting and inboard sediment underplating.

Mineral authigenesis within chemosynthetic microbial mats: Coated grain formation and phosphogenesis at a Cretaceous hydrocarbon seep, New Zealand

“…The Raukumara Peninsula is being uplifted to this day due to buoyancy created by the underplated sediments, whereby the uplift rates are some of the highest seen along the entire Hikurangi-Kermadec subduction zone (Walcott, 1987;Berryman et al, 1989). The main tectonic zones of the north-western part of North Island are the offshore outer fore arc, the onshore inner fore arc and the inner fore arc backstop, whereby the latter two units represent a relict accretionary wedge now exposed on land (Figure 1A,B; Clark et al, 2010). The Raukumara Peninsula itself consists of three distinct tectonic units, the Raukumara Range, the East Coast allochthon and Neogene sedimentary rocks that partly overlie the allochthon (Figure 1B; Reyners et al, 1999).…”

Foraminiferal record of Holocene paleo-earthquakes on the subsiding south-western Poverty Bay coastline, New Zealand

“…However, most of this stretch of coast has stepped sequences of uplifted Holocene coastal and fluvial terraces that document a segmented regime of net tectonic uplift (e.g. Ota et al 1988;Berryman et al 1989;Berryman 1993a;Clark et al 2010). Each regional segment of the coast has had a separate deformation history, with most segments having been uplifted by a sequence of co-seismic events (uplift c. 1-4 m each) at recurrence intervals of 400-2000 years (Berryman et al 1989(Berryman et al , 2011.…”

The last interglacial sea-level record of New Zealand (Aotearoa)

“…However, recent advances in sea-level studies have highlighted the need for increased spatio-and temporal density of relative sea-level (RSL) indicators, analyzed using standard definitions and methods, to assist in constraining paleo ice sheet limits and to improve models of glacio-and hydro-isostatic adjustment (GIA) research questions such as paleoclimate) and away from attempts to resolve sea-level fluctuations or eustatic sea-level history (e.g. Ghani, 1978;Hesp and Shepherd, 1978;Pillans, 1983;1986;Bull and Copper, 1986;Ward, 1988a;Suggate, 1992;Berryman, 1993;Ota et al, 1996;Rees-Jones, 2000;Begg et al, 2004;Kim and Sutherland, 2004;Litchfield and Lian, 2004;Alloway et al, 2005;Cooper and Kostro, 2006;Wilson et al, 2007;Claessens et al, 2009;Clark et al, 2010;Oakley et al, 2018). However, this heralded the practice of correlating a presumed last interglacial terrace with a generic age (e.g.…”