Lateglacial and Holocene relative sea‐level changes and first evidence for the Storegga tsunami in Sutherland, Scotland

Antony J Long,Fraser D Milne,Catherine Kelham,Alastair Dawson,James B Innes,Jon Hill,Natasha L M Barlow,Sue Dawson

doi:10.1002/jqs.2862

Antony J Long, Fraser D Milne + Show 6 more

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https://doi.org/10.1002/jqs.2862

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Abstract

ABSTRACTWe reconstruct one of the longest relative sea‐level (RSL) records in north‐west Europe from the north coast of mainland Scotland, using data collected from three sites in Loch Eriboll (Sutherland) that we combine with other studies from the region. Following deglaciation, RSL fell from a Lateglacial highstand of +6−8 m OD (Ordnance Datum = ca. mean sea level) at ca. 15 k cal a BP to below present, then rose to an early Holocene highstand and remained at ca. +1 m OD between ca. 7 and 3 k cal a BP, before falling to present. We find no evidence for significant differential Holocene glacio‐isostatic adjustment between sites on the north‐west (Lochinver, Loch Laxford), north (Loch Eriboll) and north‐east (Wick) coast of mainland Scotland. This suggests that the region was rapidly deglaciated and there was little difference in ice loads across the region. From one site at the head of Loch Eriboll we report the most westerly sedimentary evidence for the early Holocene Storegga tsunami on the Scottish mainland. The presence of the Storegga tsunami in Loch Eriboll is predicted by a tsunami wave model, which suggests that the tsunami impacted the entire north coast of Scotland and probably also the Atlantic coastline of north‐west Scotland.

Highlights

The north coast of the Scottish mainland is an important area for studying Late Glacial and Holocene relative sea-level (RSL) changes and for testing and developing different models of ice sheet history and glacio-isostatic adjustment (GIA)
Our observations show that RSL had risen to close to present Mean Tide Level (MTL), leading us to propose that the raised beach of Unit 4 was likely deposited by the Main Postglacial Transgression (Smith et al, 2012)
Our objective has been to combine new field and laboratory investigations based in Loch Eriboll (Sutherland), with GIA and palaoetsuanmi modelling to improve understanding of Late Glacial and Holocene RSL change and the potential impact of the Storegga tsunami along the north coast of Scotland

Summary

Introduction

The north coast of the Scottish mainland is an important area for studying Late Glacial and Holocene relative sea-level (RSL) changes and for testing and developing different models of ice sheet history and glacio-isostatic adjustment (GIA). One GIA model that uses a thermodynamical ice sheet model to define ice load history, predicts ice that was 500-750 m thicker in the northeast of Scotland compared to that in the northwest of Scotland (Kuchar et al, 2012). Such a contrast would be expected to cause significant west-east differential GIA movements across the northern Scottish mainland that would be observable in Late Glacial and Holocene RSL records. These latter models broadly agree with isobase maps developed from field observations of the altitude of the Main Postglacial Transgression, a sea-level highstand attained in the early to mid-Holocene, that suggest the north mainland sits on the same shoreline isobase (e.g. Smith et al, 2012) (Figure 2)

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