Holocene relative sea-level changes in Harris, Outer Hebrides, Scotland, UK

Jason T Jordan, David E Smith, Sue Dawson, Alastair G Dawson

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Evidence for relative sea-level changes during the middle and late Holocene is examined from two locations on the Atlantic coast of Harris, Outer Hebrides, Scotland, using morphological mapping and survey, stratigraphical, grain size and diatom analysis, and radiocarbon dating. The earliest event identified is a marine flood, which occurred after 7982–8348 cal. a (7370 ± 80 14C a) BP, when the sea crossed a threshold lying at −0.08 m Ordnance Datum Newlyn (OD) (−2.17 m mean high water springs (MHWS)) before withdrawing. This could have been due to a storm or to the Holocene Storegga Slide tsunami. By 6407–6122 cal. a (5500 ± 60 14C a) BP, relative sea levels had begun to fall from a sandflat surface with an indicated MHWS level of between 0.08 and −1.96 m (−2.01 to −4.05 m). This fall reached between −0.30 and −2.35 m (−2.39 to −4.44 m) after 5841–5050 cal. a (4760 ± 130 14C a) BP, but was succeeded by a relative sea-level rise which reached between 0.54 and −1.57 m (−1.55 to −3.66 m) by 5450–4861 cal. a (4500 ± 100 14C a) BP. This rise continued, possibly with an interruption, until a second sandflat surface was reached between 2.34 and −0.26 m (0.25 to −2.35 m) between 2952–3375 cal. a (3000 ± 80 14C a) and 1948–2325 cal. a (2130 ± 70 14C a) BP, before present levels were reached. The regressive episode from the earliest sandflat is correlated with the abandonment of the Main Postglacial Shoreline. It is maintained that the fluctuations in relative sea level recorded can be correlated with similar events elsewhere on the periphery of the glacio-isostatic centre and may therefore reflect secular changes in nearshore sea surface levels. Despite published evidence from trim lines of differential ice sheet loading across the area, no evidence of variations in uplift between the locations concerned could be found. Copyright © 2009 John Wiley & Sons, Ltd.
Original languageEnglish
Pages (from-to)115-134
Number of pages20
JournalJournal of Quaternary Science
Volume25
Issue number2
Early online date26 May 2009
DOIs
Publication statusPublished - Feb 2010

Keywords

  • morphology
  • stratigraphy
  • grain size
  • diatoms
  • radiocarbon dating
  • holocene
  • relative sea-level changes
  • glacio-isostasy

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