An examination of spatial variability in the timing and magnitude of Holocene relative sea-level changes in the New Zealand archipelago

Abstract

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Zealand archipelago: the northern North Island (including Northland, Auckland, and the Coromandel 13 Peninsula); the southwest coast of the North Island; the Canterbury coast (South Island); and the 14 Otago coast (South Island). In the North Island the RSL highstand commenced c. 8,100-7,2400 cal yr 15 BP when present mean sea-level (PMSL) was first attained. This is c. 600-1,400 years earlier than has 16 been previously indicated for the New Zealand region as a whole, and is consistent with recent 17Holocene RSL reconstructions from Australia. In North Island locations the early-Holocene sea-level 18 highstand was quite pronounced, with RSL up to 2.75 m higher than present. In the South Island the 19 onset of highstand conditions was later, with the first attainment of PMSL being between 7,000-20 6,400 cal yr BP. In the mid-Holocene the northern North Island experienced the largest sea-level 21 highstand, with RSL up to 3.00 m higher than present. This is demonstrably higher than the 22 highstand recorded for the southwest North Island and Otago regions. A number of different drivers 23 region, while research from Australia has suggested that north-south variations in Holocene RSL 32 changes due to hydro-isostatic influences are limited or non-existent. At the regional-to local-scale, 33 post-glacial meltwater loading on the continental shelf around New Zealand is predicted by GIA 34 modelling to have a significant effect on the timing and magnitude of RSL changes through the 35 phenomenon of continental levering. The spatial variation in continental levering is controlled by the 36 configuration of the coast and the width of the adjacent continental shelf, with continental levering 37 providing a robust explanation for the observed spatial and temporal variations in RSL changes. 38Further research is required to characterise the regional and local effects of different tectonic 39 regimes, wave climates, and sediment regimes. These are potentially very significant drivers of RSL 40 variability at the regional-to local-scale. However, the magnitude of their potential effects remains 41 equivocal. 42Highlights 43  RSL histories were reconstructed for four regions in the New Zealand archipelago 44  Northern sites experience RSL rise earlier compared to southern sites 45  Northern sites experience a higher-magnitude highstand compared to southern sites 46  Long-wavelength signals from Antarctica cannot explain the observed variation in RSL 47  A range of processes potentiall...

Glacial Isostatic Adjustment modelling: historical perspectives, recent advances, and future directions

“…In particular, it should be noted that coastlines orientated perpendicular to the continental shelf break will experience differential amounts of uplift (e.g. Lambeck and Nakada, 1990;Clement et al, 2016). 310…”

Late Holocene intensification of the westerly winds at the subantarctic Auckland Islands (51° S), New Zealand

“…Downcore changes in magnetic susceptibility, oxygen and carbon stable isotopes of benthic foraminifera, and bulk organic carbon isotopes and atomic C / N provide evidence for the Holocene palaeoenvironmental evolution of Hanfield Inlet. Seismic data and a transition from lacustrine to marine sediments reveal the post-glacial evolution of Hanfield Inlet, where marine incursion into a palaeolake occurred around 10 000-9000 yr BP, based on fjord entrance sill height and local sea level reconstructions (Clement et al, 2016;Dlabola et al, 2015). Magnetic susceptibility, bulk organic δ 13 C, and atomic C / N indicate increased SHWW influence from 1600 to 900 yr BP, consistent with previous palynological reconstructions of precipitation and wind strength at the Auckland Islands (McGlone et al, 2000;Turney et al, 2016b).…”

“…Two sharp transitions identified in seismic profiles occur beneath the fine-grained marine and lacustrine sedimentary sequence and probably represent glacial sediment deposited on eroded volcanic basement during glacial retreat. Based on the height of the submarine sill (∼ 8 m) and relative sea level curves from southern New Zealand (Clement et al, 2016;Dlabola et al, 2015), marine incursion of Hanfield Inlet likely occurred between 10 000 and 9000 yr BP.…”

Storm response of a mixed sand gravel beach ridge plain under falling relative sea levels: A stratigraphic investigation using ground penetrating radar

“…Sea level curve for the Canterbury Coast, New Zealand, adapted from Clement et al . (), showing that relative sea levels have been falling in the region over the last c . 4000 years.…”