Dimensions and deglacial chronology of the Outer Hebrides Ice Cap, northwest Scotland: implications of cosmic ray exposure dating
Abstract Cosmic ray exposure ages of frost‐weathered bedrock from mountain summits in the Outer Hebrides exceed the age of Late Devensian glaciation. Exposure ages of most glacially‐abraded bedrock surfaces at low and intermediate elevations are younger than the age of maximum Late Devensian glaciat...
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crwiley:10.1002/jqs.933 2024-06-02T08:08:04+00:00 Dimensions and deglacial chronology of the Outer Hebrides Ice Cap, northwest Scotland: implications of cosmic ray exposure dating Stone, John O. Ballantyne, Colin K. 2005 http://dx.doi.org/10.1002/jqs.933 https://onlinelibrary.wiley.com/doi/pdf/10.1002/jqs.933 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Journal of Quaternary Science volume 21, issue 1, page 75-84 ISSN 0267-8179 1099-1417 journal-article 2005 crwiley https://doi.org/10.1002/jqs.933 2024-05-03T11:49:24Z Abstract Cosmic ray exposure ages of frost‐weathered bedrock from mountain summits in the Outer Hebrides exceed the age of Late Devensian glaciation. Exposure ages of most glacially‐abraded bedrock surfaces at low and intermediate elevations are younger than the age of maximum Late Devensian glaciation. These results confirm that previously mapped periglacial trimlines in the Outer Hebrides define the upper limit of bedrock erosion by Late Devensian ice. They are consistent with the interpretation, based on geomorphological evidence, that the trimlines mark the approximate upper limit of a Late Devensian Outer Hebrides Ice Cap. A postglacial exposure age from the summit of Oreval (662 m) suggests that this mountain was overrun during the last glaciation, indicating thicker ice cover and a lower surface gradient west of the ice‐cap divide than previously inferred. Although bedrock surfaces below the trimlines are strongly ice‐moulded, some show evidence of prior cosmic ray exposure, which we attribute to limited erosion during Late Devensian glaciation. If this interpretation is correct, the youngest apparent ages from these surfaces give the most reliable dates for deglaciation, at ca. 14.5–14 ka. This implies that ice persisted at favourable sites through the warm opening phase of the Windermere Interstade. Comparison with radiocarbon‐dated evidence from offshore cores suggests net ice margin retreat of ∼74 km eastwards across the adjacent shelf in > 2.3 ± 1.0 ka. The dating evidence is consistent with relatively rapid retreat of calving margins to the coast, then slower withdrawal of ice margins to high ground. Copyright © 2005 John Wiley & Sons, Ltd. Article in Journal/Newspaper Ice cap Wiley Online Library Journal of Quaternary Science 21 1 75 84 |
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English |
description |
Abstract Cosmic ray exposure ages of frost‐weathered bedrock from mountain summits in the Outer Hebrides exceed the age of Late Devensian glaciation. Exposure ages of most glacially‐abraded bedrock surfaces at low and intermediate elevations are younger than the age of maximum Late Devensian glaciation. These results confirm that previously mapped periglacial trimlines in the Outer Hebrides define the upper limit of bedrock erosion by Late Devensian ice. They are consistent with the interpretation, based on geomorphological evidence, that the trimlines mark the approximate upper limit of a Late Devensian Outer Hebrides Ice Cap. A postglacial exposure age from the summit of Oreval (662 m) suggests that this mountain was overrun during the last glaciation, indicating thicker ice cover and a lower surface gradient west of the ice‐cap divide than previously inferred. Although bedrock surfaces below the trimlines are strongly ice‐moulded, some show evidence of prior cosmic ray exposure, which we attribute to limited erosion during Late Devensian glaciation. If this interpretation is correct, the youngest apparent ages from these surfaces give the most reliable dates for deglaciation, at ca. 14.5–14 ka. This implies that ice persisted at favourable sites through the warm opening phase of the Windermere Interstade. Comparison with radiocarbon‐dated evidence from offshore cores suggests net ice margin retreat of ∼74 km eastwards across the adjacent shelf in > 2.3 ± 1.0 ka. The dating evidence is consistent with relatively rapid retreat of calving margins to the coast, then slower withdrawal of ice margins to high ground. Copyright © 2005 John Wiley & Sons, Ltd. |
format |
Article in Journal/Newspaper |
author |
Stone, John O. Ballantyne, Colin K. |
spellingShingle |
Stone, John O. Ballantyne, Colin K. Dimensions and deglacial chronology of the Outer Hebrides Ice Cap, northwest Scotland: implications of cosmic ray exposure dating |
author_facet |
Stone, John O. Ballantyne, Colin K. |
author_sort |
Stone, John O. |
title |
Dimensions and deglacial chronology of the Outer Hebrides Ice Cap, northwest Scotland: implications of cosmic ray exposure dating |
title_short |
Dimensions and deglacial chronology of the Outer Hebrides Ice Cap, northwest Scotland: implications of cosmic ray exposure dating |
title_full |
Dimensions and deglacial chronology of the Outer Hebrides Ice Cap, northwest Scotland: implications of cosmic ray exposure dating |
title_fullStr |
Dimensions and deglacial chronology of the Outer Hebrides Ice Cap, northwest Scotland: implications of cosmic ray exposure dating |
title_full_unstemmed |
Dimensions and deglacial chronology of the Outer Hebrides Ice Cap, northwest Scotland: implications of cosmic ray exposure dating |
title_sort |
dimensions and deglacial chronology of the outer hebrides ice cap, northwest scotland: implications of cosmic ray exposure dating |
publisher |
Wiley |
publishDate |
2005 |
url |
http://dx.doi.org/10.1002/jqs.933 https://onlinelibrary.wiley.com/doi/pdf/10.1002/jqs.933 |
genre |
Ice cap |
genre_facet |
Ice cap |
op_source |
Journal of Quaternary Science volume 21, issue 1, page 75-84 ISSN 0267-8179 1099-1417 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1002/jqs.933 |
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Journal of Quaternary Science |
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21 |
container_issue |
1 |
container_start_page |
75 |
op_container_end_page |
84 |
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1800753230623277056 |