Testing the Mid-Holocene Relative Sea-Level Highstand Hypothesis in North Wales, United Kingdom

Greg T. Rushby*, Geoff T. Richards, W. Roland Gehrels, William P. Anderson, Mark D. Bateman, William H. Blake

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Accurate Holocene relative sea-level curves are vital for modelling future sea-level changes, particularly in regions where relative sea-level changes are dominated by isostatically induced vertical land movements. In North Wales, various glacial isostatic adjustment (GIA) models predict a mid-Holocene relative sea-level highstand between 4 and 6 ka, which is unsubstantiated by any geological sea-level data but affects the ability of geophysical models to model accurately past and future sea levels. Here, we use a newly developed foraminifera-based sea-level transfer function to produce a 3300-year-long late-Holocene relative sea-level reconstruction from a salt marsh in the Malltraeth estuary on the south Anglesey coast in North Wales. This is the longest continuous late-Holocene relative sea-level reconstruction in Northwest Europe. We combine this record with two new late-Holocene sea-level index points (SLIPs) obtained from a freshwater marsh at Rhoscolyn, Anglesey, and with previously published regional SLIPs, to produce a relative sea-level record for North Wales that spans from ca. 13,000 BP to the present. This record leaves no room for a mid-Holocene relative sea-level highstand in the region. We conclude that GIA models that include a mid-Holocene sea-level highstand for North Wales need revision before they are used in the modelling of past and future relative sea-level changes around the British Isles.

Original languageEnglish
Pages (from-to)1-12
Number of pages12
JournalThe Holocene
Publication statusPublished - 12 Jun 2019

Bibliographical note

© The Author(s) 2019


  • foraminifera
  • glacial isostatic adjustment (GIA)
  • groundwater
  • Irish sea
  • salt marsh

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