Skip to content

Research at St Andrews

Timing and pace of ice-sheet withdrawal across the marine–terrestrial transition west of Ireland during the last glaciation

Research output: Contribution to journalArticlepeer-review


Open Access permissions



Colm Ó Cofaigh, S. Louise Callard, David H. Roberts, Richard C. Chiverrell, C. K. Ballantyne, David J. A. Evans, Margot Saher, Katrien J. J. Van Landeghem, Rachel Smedley, Sara Benetti, Matthew Burke, Chris D. Clark, Geoff A. T. Duller, Derek Fabel, Stephen J. Livingstone, Stephen Mccarron, Alicia Medialdea, Steven G. Moreton, Fabio Sacchetti

School/Research organisations


Understanding the pace and drivers of marine‐based ice‐sheet retreat relies upon the integration of numerical ice‐sheet models with observations from contemporary polar ice sheets and well‐constrained palaeo‐glaciological reconstructions. This paper provides a reconstruction of the retreat of the last British–Irish Ice Sheet (BIIS) from the Atlantic shelf west of Ireland during and following the Last Glacial Maximum (LGM). It uses marine‐geophysical data and sediment cores dated by radiocarbon, combined with terrestrial cosmogenic nuclide and optically stimulated luminescence dating of onshore ice‐marginal landforms, to reconstruct the timing and rate of ice‐sheet retreat from the continental shelf and across the adjoining coastline of Ireland, thus including the switch from a marine‐ to a terrestrially‐based ice‐sheet margin. Seafloor bathymetric data in the form of moraines and grounding‐zone wedges on the continental shelf record an extensive ice sheet west of Ireland during the LGM which advanced to the outer shelf. This interpretation is supported by the presence of dated subglacial tills and overridden glacimarine sediments from across the Porcupine Bank, a westwards extension of the Irish continental shelf. The ice sheet was grounded on the outer shelf at ~26.8 ka cal bp with initial retreat underway by 25.9 ka cal bp. Retreat was not a continuous process but was punctuated by marginal oscillations until ~24.3 ka cal bp. The ice sheet thereafter retreated to the mid‐shelf where it formed a large grounding‐zone complex at ~23.7 ka cal bp. This retreat occurred in a glacimarine environment. The Aran Islands on the inner continental shelf were ice‐free by ~19.5 ka bp and the ice sheet had become largely terrestrially based by 17.3 ka bp. This suggests that the Aran Islands acted to stabilize and slow overall ice‐sheet retreat once the BIIS margin had reached the inner shelf. Our results constrain the timing of initial retreat of the BIIS from the outer shelf west of Ireland to the period of minimum global eustatic sea level. Initial retreat was driven, at least in part, by glacio‐isostatically induced, high relative sea level. Net rates of ice‐sheet retreat across the shelf were slow (62–19 m a−1) and reduced (8 m a−1) as the ice sheet vacated the inner shelf and moved onshore. A picture therefore emerges of an extensive BIIS on the Atlantic shelf west of Ireland, in which early, oscillatory retreat was followed by slow episodic retreat which decelerated further as the ice margin became terrestrially based. More broadly, this demonstrates the importance of localized controls, in particular bed topography, on modulating the retreat of marine‐based sectors of ice sheets.


Original languageEnglish
Number of pages28
JournalJournal of Quaternary Science
VolumeEarly View
Early online date7 Apr 2021
Publication statusE-pub ahead of print - 7 Apr 2021

    Research areas

  • British–Irish Ice Sheet, Glacimarine sediments, Ice sheet extent, Ice sheet retreat, Last Glacial Maximum, Porcupine Bank, Radiocarbon dating, Subglacial till, Western Ireland

Discover related content
Find related publications, people, projects and more using interactive charts.

View graph of relations

Related by author

  1. The Scenery of Scotland revisited: retrospective assessment of a classic geomorphological text

    Ballantyne, C., 15 Apr 2021, In: Scottish Geographical Journal. Latest Articles

    Research output: Contribution to journalArticlepeer-review

  2. The deglaciation of the western sector of the Irish Ice Sheet from the inner continental shelf to its terrestrial margin

    Roberts, D. H., Ó Cofaigh, C., Ballantyne, C. K., Burke, M., Chiverrell, R. C., Evans, D. J. A., Clark, C. D., Duller, G. A. T., Ely, J., Fabel, D., Small, D., Smedley, R. K. & Callard, S. L., 1 Jun 2020, In: Boreas. Early View

    Research output: Contribution to journalArticlepeer-review

  3. Scottish landform examples 45: Sgriob na Caillich: a landslide-sourced medial moraine on the Isle of Jura

    Ballantyne, C. K. & Dawson, A. G., 18 Sep 2019, In: Scottish Geographical Journal. 135, 1-2, p. 139-149 11 p.

    Research output: Contribution to journalArticlepeer-review

  4. The last Scottish Ice Sheet

    Ballantyne, C. K. & Small, D., Mar 2019, In: Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 110, 1-2, p. 93–131 39 p.

    Research output: Contribution to journalArticlepeer-review

Related by journal

  1. Journal of Quaternary Science (Journal)

    Colin Ballantyne (Member of editorial board)

    1994 → …

    Activity: Publication peer-review and editorial work typesEditor of research journal

Related by journal

  1. The interpretative value of transformed tephra sequences

    Dugmore, A., Thompson, P., Streeter, R. T., Cutler, N., Newton, A. & Kirkbride, M., 29 Jan 2020, In: Journal of Quaternary Science. 35, 1-2, p. 23-38

    Research output: Contribution to journalArticlepeer-review

  2. Deglaciation chronology of the Donegal Ice Centre, north-west Ireland

    Wilson, P., Ballantyne, C. K., Benetti, S., Small, D., Fabel, D. & Clark, C. D., 11 Jan 2019, In: Journal of Quaternary Science. 34, 1, p. 16-28 13 p.

    Research output: Contribution to journalArticlepeer-review

  3. Continuous human presence without extensive reductions in forest cover over the past 2500 years in an aseasonal Amazonian rainforest

    Kelly, T. J., Lawson, I. T., Roucoux, K. H., Baker, T. R., Honorio-Coronado, E. N., Jones, T. D. & Rivas Panduro, S., 4 May 2018, In: Journal of Quaternary Science. 33, 4, p. 369-379 11 p.

    Research output: Contribution to journalArticlepeer-review

  4. Ice margin oscillations during deglaciation of the northern Irish Sea Basin

    Chiverrell, R. C., Smedley, R. K., Small, D., Ballantyne, C. K., Burke, M. J., Callard, S. L., Clark, C. D., Duller, G. A. T., Evans, D. J. A., Fabel, D., van Landeghem, K., Livingstone, S., O Cofaigh, C., Thomas, G. S. P., Roberts, D. H., Saher, M., Scourse, J. D. & Wilson, P., 9 Oct 2018, In: Journal of Quaternary Science. 33, 7, p. 739-762 24 p.

    Research output: Contribution to journalArticlepeer-review

ID: 273717682