10 Be exposure age dating of Late Quaternary relative sea level changes and deglaciation of W Jura and NE Islay, Scottish Inner Hebrides

• Published in: Earth and Environmental Science Transactions of the Royal Society of Edinburgh
• Main Authors: Dawson, Alastair G., Bishop, Paul, Hansom, James, Fabel, Derek
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2022
• Subjects: Be exposure dating; emerged beach ridges; emerged shorelines; glacio-isostatic rebound; global meltwater pulse 1A; ice sheet deglaciation; marine terraces; shore platforms; /dk/atira/pure/subjectarea/asjc/2300/2300; name=General Environmental Science; /dk/atira/pure/subjectarea/asjc/1900/1900; name=General Earth and Planetary Sciences; Islay; Jura; Long Beach; Ice Sheet
• Online Access: https://discovery.dundee.ac.uk/en/publications/7bce4bf2-5512-46f5-911e-f1010657d49f; https://doi.org/10.1017/S175569102200010X; https://discovery.dundee.ac.uk/ws/files/94853363/10be_exposure_age_dating_of_late_quaternary_relative_sea_level_changes_and_deglaciation_of_w_jura_and_ne_islay_scottish_inner_hebrides.pdf; http://www.scopus.com/inward/record.url?scp=85146528870&partnerID=8YFLogxK

New 10Be exposure age dating and geomorphological mapping of emerged shoreline features in W Jura and NE Islay throw new light on the regional pattern of ice sheet deglaciation and late-glacial relative sea level change. We conclude that the oldest and highest emerged shorelines in this area were produced ~15.7-16.3 ka, shortly after ice sheet deglaciation ~16.5 ka. It is envisaged that the first incursion of marine waters into coastal areas took place close to a former ice sheet margin that oscillated in position across this part of the Scottish Inner Hebrides. The first evidence of late-glacial marine sedimentation following deglaciation consists of emerged marine terrace fragments and unvegetated gravel beach ridges, the former represented by a prominent glacio-isostatically tilted shoreline that declines in altitude NE to SW, from ~40 m above ordnance datum (OD) in NW Jura to ~19 m OD in central Islay. In W Jura, north of Loch Tarbert, spectacular staircases of up to 55 unvegetated gravel beach ridges were formed shortly after regional deglaciation, possibly within 1 ka. A preliminary estimate of the average rate of relative sea level lowering across W Jura between deglaciation and the Younger Dryas is in the order of ~7 mmyr-1. Geomorphological evidence from Shian Bay, W Jura, indicates a truncation of the late-glacial beach ridge staircases by a large 480-m-long beach ridge (the Colonsay Ridge) at ~14.9 ka, when former relative sea level was at ~18 m OD. This ridge may represent the product of either a stillstand in the progressive lowering of relative sea level during the late-glacial or a reversal. This raises the intriguing possibility of an association between ridge formation and the timing of the well-established global meltwater pulse 1A between ~14.65 and ~14.8 ka.