Trimlines, blockfields and the vertical extent of the last ice sheet in southern Ireland
Trimlines separating glacially abraded lower slopes from blockfield-covered summits on Irish mountains have traditionally been interpreted as representing the upper limit of the last ice sheet during the Last Glacial Maximum (LGM). Cosmogenic 10 Be exposure ages obtained for samples from glacially d...
Published in: | Boreas |
---|---|
Main Authors: | , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
2015
|
Subjects: | |
Online Access: | https://research-portal.st-andrews.ac.uk/en/researchoutput/trimlines-blockfields-and-the-vertical-extent-of-the-last-ice-sheet-in-southern-ireland(51b1a5f9-a888-42b2-84db-a2a036e9d1df).html https://doi.org/10.1111/bor.12109 https://research-repository.st-andrews.ac.uk/bitstream/10023/6021/1/ballantyne2015boreas_earlyview.pdf |
id |
ftunstandrewcris:oai:research-portal.st-andrews.ac.uk:publications/51b1a5f9-a888-42b2-84db-a2a036e9d1df |
---|---|
record_format |
openpolar |
spelling |
ftunstandrewcris:oai:research-portal.st-andrews.ac.uk:publications/51b1a5f9-a888-42b2-84db-a2a036e9d1df 2024-06-23T07:53:46+00:00 Trimlines, blockfields and the vertical extent of the last ice sheet in southern Ireland Ballantyne, Colin Stone, John O. 2015-04 application/pdf https://research-portal.st-andrews.ac.uk/en/researchoutput/trimlines-blockfields-and-the-vertical-extent-of-the-last-ice-sheet-in-southern-ireland(51b1a5f9-a888-42b2-84db-a2a036e9d1df).html https://doi.org/10.1111/bor.12109 https://research-repository.st-andrews.ac.uk/bitstream/10023/6021/1/ballantyne2015boreas_earlyview.pdf eng eng https://research-portal.st-andrews.ac.uk/en/researchoutput/trimlines-blockfields-and-the-vertical-extent-of-the-last-ice-sheet-in-southern-ireland(51b1a5f9-a888-42b2-84db-a2a036e9d1df).html info:eu-repo/semantics/openAccess Ballantyne , C & Stone , J O 2015 , ' Trimlines, blockfields and the vertical extent of the last ice sheet in southern Ireland ' , Boreas , vol. 44 , no. 2 , pp. 277-287 . https://doi.org/10.1111/bor.12109 article 2015 ftunstandrewcris https://doi.org/10.1111/bor.12109 2024-06-13T00:44:41Z Trimlines separating glacially abraded lower slopes from blockfield-covered summits on Irish mountains have traditionally been interpreted as representing the upper limit of the last ice sheet during the Last Glacial Maximum (LGM). Cosmogenic 10 Be exposure ages obtained for samples from glacially deposited perched boulders resting on blockfield debris on the summit area of Slievenamon (721 m a.s.l.) in southern Ireland demonstrate emplacement by the last Irish Ice Sheet (IIS), implying preservation of the blockfield under cold-based ice during the LGM, and supporting the view that trimlines throughout the British Isles represent former englacial thermal regime boundaries between a lower zone of warm-based sliding ice and an upper zone of cold-based ice. The youngest exposure age (22.6±1.1 or 21.0±0.9 ka, depending on the 10 Be production rate employed) is statistically indistinguishable from the mean age (23.4±1.2 or 21.8±0.9 ka) obtained for two samples from ice-abraded bedrock at high ground on Blackstairs Mountain, 51 km to the east, and with published cosmogenic 36 Cl ages. Collectively, these ages imply (i) early (24–21 ka) thinning of the last IIS and emergence of high ground in SE Ireland; (ii) relatively brief (1–3 ka) glacial occupation of southernmost Ireland during the LGM; (iii) decoupling of the Irish Sea Ice Stream and ice from the Irish midlands within a similar time frame; and (iv) that the southern fringe of Ireland was deglaciated before western and northern Ireland. Article in Journal/Newspaper Ice Sheet Sea ice University of St Andrews: Research Portal Boreas 44 2 277 287 |
institution |
Open Polar |
collection |
University of St Andrews: Research Portal |
op_collection_id |
ftunstandrewcris |
language |
English |
description |
Trimlines separating glacially abraded lower slopes from blockfield-covered summits on Irish mountains have traditionally been interpreted as representing the upper limit of the last ice sheet during the Last Glacial Maximum (LGM). Cosmogenic 10 Be exposure ages obtained for samples from glacially deposited perched boulders resting on blockfield debris on the summit area of Slievenamon (721 m a.s.l.) in southern Ireland demonstrate emplacement by the last Irish Ice Sheet (IIS), implying preservation of the blockfield under cold-based ice during the LGM, and supporting the view that trimlines throughout the British Isles represent former englacial thermal regime boundaries between a lower zone of warm-based sliding ice and an upper zone of cold-based ice. The youngest exposure age (22.6±1.1 or 21.0±0.9 ka, depending on the 10 Be production rate employed) is statistically indistinguishable from the mean age (23.4±1.2 or 21.8±0.9 ka) obtained for two samples from ice-abraded bedrock at high ground on Blackstairs Mountain, 51 km to the east, and with published cosmogenic 36 Cl ages. Collectively, these ages imply (i) early (24–21 ka) thinning of the last IIS and emergence of high ground in SE Ireland; (ii) relatively brief (1–3 ka) glacial occupation of southernmost Ireland during the LGM; (iii) decoupling of the Irish Sea Ice Stream and ice from the Irish midlands within a similar time frame; and (iv) that the southern fringe of Ireland was deglaciated before western and northern Ireland. |
format |
Article in Journal/Newspaper |
author |
Ballantyne, Colin Stone, John O. |
spellingShingle |
Ballantyne, Colin Stone, John O. Trimlines, blockfields and the vertical extent of the last ice sheet in southern Ireland |
author_facet |
Ballantyne, Colin Stone, John O. |
author_sort |
Ballantyne, Colin |
title |
Trimlines, blockfields and the vertical extent of the last ice sheet in southern Ireland |
title_short |
Trimlines, blockfields and the vertical extent of the last ice sheet in southern Ireland |
title_full |
Trimlines, blockfields and the vertical extent of the last ice sheet in southern Ireland |
title_fullStr |
Trimlines, blockfields and the vertical extent of the last ice sheet in southern Ireland |
title_full_unstemmed |
Trimlines, blockfields and the vertical extent of the last ice sheet in southern Ireland |
title_sort |
trimlines, blockfields and the vertical extent of the last ice sheet in southern ireland |
publishDate |
2015 |
url |
https://research-portal.st-andrews.ac.uk/en/researchoutput/trimlines-blockfields-and-the-vertical-extent-of-the-last-ice-sheet-in-southern-ireland(51b1a5f9-a888-42b2-84db-a2a036e9d1df).html https://doi.org/10.1111/bor.12109 https://research-repository.st-andrews.ac.uk/bitstream/10023/6021/1/ballantyne2015boreas_earlyview.pdf |
genre |
Ice Sheet Sea ice |
genre_facet |
Ice Sheet Sea ice |
op_source |
Ballantyne , C & Stone , J O 2015 , ' Trimlines, blockfields and the vertical extent of the last ice sheet in southern Ireland ' , Boreas , vol. 44 , no. 2 , pp. 277-287 . https://doi.org/10.1111/bor.12109 |
op_relation |
https://research-portal.st-andrews.ac.uk/en/researchoutput/trimlines-blockfields-and-the-vertical-extent-of-the-last-ice-sheet-in-southern-ireland(51b1a5f9-a888-42b2-84db-a2a036e9d1df).html |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1111/bor.12109 |
container_title |
Boreas |
container_volume |
44 |
container_issue |
2 |
container_start_page |
277 |
op_container_end_page |
287 |
_version_ |
1802645587565215744 |