Cosmogenic 10 Be and 26 Al ages of Holocene moraines in southern Norway II: evidence for individualistic responses of high-altitude glaciers to millennial-scale climatic fluctuations
Abstract: 10 Be and 26 Al exposure ages are reported for boulder moraine ridges in front of two high-altitude cirque glaciers (Austanbotnbreen, Jotunheimen and Østre Tundradalskyrkjabre, Breheimen) in southern Norway. Ages and 1σ external uncertainties for Austanbotnbreen moraines range from 7.4 ± 0...
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crsagepubl:10.1177/0959683608096592 2024-04-07T07:52:39+00:00 Cosmogenic 10 Be and 26 Al ages of Holocene moraines in southern Norway II: evidence for individualistic responses of high-altitude glaciers to millennial-scale climatic fluctuations Shakesby, Richard A. Matthews, John A. Schnabel, Christoph 2008 http://dx.doi.org/10.1177/0959683608096592 http://journals.sagepub.com/doi/pdf/10.1177/0959683608096592 en eng SAGE Publications http://journals.sagepub.com/page/policies/text-and-data-mining-license The Holocene volume 18, issue 8, page 1165-1177 ISSN 0959-6836 1477-0911 Paleontology Earth-Surface Processes Ecology Archeology Global and Planetary Change journal-article 2008 crsagepubl https://doi.org/10.1177/0959683608096592 2024-03-08T03:21:04Z Abstract: 10 Be and 26 Al exposure ages are reported for boulder moraine ridges in front of two high-altitude cirque glaciers (Austanbotnbreen, Jotunheimen and Østre Tundradalskyrkjabre, Breheimen) in southern Norway. Ages and 1σ external uncertainties for Austanbotnbreen moraines range from 7.4 ± 0.75 ka to 8.7 ± 0.9 ka when no adjustment for snow shielding is made. With the maximum conceivable snow cover effect (2 m thick, a density of 0.2 g/cm 3 , 6 months duration) at the exposed site, the resulting adjusted (7.7 ± 0.8 to 10.9 ± 1.3 ka) as well as unadjusted ages suggest moraine formation possibly during both the 8.2 ka event (Finse Event in southern Norway) and the Erdalen Event ( c. 10.0 ka). In contrast, ages obtained for the outer ridges of the large moraine complex in front of Østre Tundradalskyrkjabre range from 1.1 ± 0.3 ka to 1.9 ± 0.4 ka assuming no snow shielding. Assuming extreme snow-lie conditions (4 m thick, 0.2 g/cm 3 density, 6 months duration) at this more sheltered site, the adjusted ages (1.4 ± 0.4 to 2.4 ± 0.5 ka) still indicate late-Holocene, pre-`Little Ice Age' ridge formation. Less likely alternative explanations of the late-Holocene ages, including avalanching of debris onto the moraine, inventories of inherited nuclides in the samples and possible episodic `push-deformation' disturbance of the ice-cored moraine complex, are discussed. The results point to the potential of surface exposure dating in reconstructing Holocene glacier variation chronologies, particularly with respect to high-altitude glaciers and to individualistic responses of these glaciers to Holocene millennial-scale climatic fluctuations. Difficulties with dating moraines in front of small high-altitude glaciers using cosmogenic nuclides, including uncertain snow shielding effect, short glacial transport distance, possibly not `zeroing' an inherited cosmogenic signal and repeated disturbance of a moraine complex, are discussed. Article in Journal/Newspaper glacier SAGE Publications Norway The Holocene 18 8 1165 1177 |
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SAGE Publications |
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English |
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Paleontology Earth-Surface Processes Ecology Archeology Global and Planetary Change |
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Paleontology Earth-Surface Processes Ecology Archeology Global and Planetary Change Shakesby, Richard A. Matthews, John A. Schnabel, Christoph Cosmogenic 10 Be and 26 Al ages of Holocene moraines in southern Norway II: evidence for individualistic responses of high-altitude glaciers to millennial-scale climatic fluctuations |
topic_facet |
Paleontology Earth-Surface Processes Ecology Archeology Global and Planetary Change |
description |
Abstract: 10 Be and 26 Al exposure ages are reported for boulder moraine ridges in front of two high-altitude cirque glaciers (Austanbotnbreen, Jotunheimen and Østre Tundradalskyrkjabre, Breheimen) in southern Norway. Ages and 1σ external uncertainties for Austanbotnbreen moraines range from 7.4 ± 0.75 ka to 8.7 ± 0.9 ka when no adjustment for snow shielding is made. With the maximum conceivable snow cover effect (2 m thick, a density of 0.2 g/cm 3 , 6 months duration) at the exposed site, the resulting adjusted (7.7 ± 0.8 to 10.9 ± 1.3 ka) as well as unadjusted ages suggest moraine formation possibly during both the 8.2 ka event (Finse Event in southern Norway) and the Erdalen Event ( c. 10.0 ka). In contrast, ages obtained for the outer ridges of the large moraine complex in front of Østre Tundradalskyrkjabre range from 1.1 ± 0.3 ka to 1.9 ± 0.4 ka assuming no snow shielding. Assuming extreme snow-lie conditions (4 m thick, 0.2 g/cm 3 density, 6 months duration) at this more sheltered site, the adjusted ages (1.4 ± 0.4 to 2.4 ± 0.5 ka) still indicate late-Holocene, pre-`Little Ice Age' ridge formation. Less likely alternative explanations of the late-Holocene ages, including avalanching of debris onto the moraine, inventories of inherited nuclides in the samples and possible episodic `push-deformation' disturbance of the ice-cored moraine complex, are discussed. The results point to the potential of surface exposure dating in reconstructing Holocene glacier variation chronologies, particularly with respect to high-altitude glaciers and to individualistic responses of these glaciers to Holocene millennial-scale climatic fluctuations. Difficulties with dating moraines in front of small high-altitude glaciers using cosmogenic nuclides, including uncertain snow shielding effect, short glacial transport distance, possibly not `zeroing' an inherited cosmogenic signal and repeated disturbance of a moraine complex, are discussed. |
format |
Article in Journal/Newspaper |
author |
Shakesby, Richard A. Matthews, John A. Schnabel, Christoph |
author_facet |
Shakesby, Richard A. Matthews, John A. Schnabel, Christoph |
author_sort |
Shakesby, Richard A. |
title |
Cosmogenic 10 Be and 26 Al ages of Holocene moraines in southern Norway II: evidence for individualistic responses of high-altitude glaciers to millennial-scale climatic fluctuations |
title_short |
Cosmogenic 10 Be and 26 Al ages of Holocene moraines in southern Norway II: evidence for individualistic responses of high-altitude glaciers to millennial-scale climatic fluctuations |
title_full |
Cosmogenic 10 Be and 26 Al ages of Holocene moraines in southern Norway II: evidence for individualistic responses of high-altitude glaciers to millennial-scale climatic fluctuations |
title_fullStr |
Cosmogenic 10 Be and 26 Al ages of Holocene moraines in southern Norway II: evidence for individualistic responses of high-altitude glaciers to millennial-scale climatic fluctuations |
title_full_unstemmed |
Cosmogenic 10 Be and 26 Al ages of Holocene moraines in southern Norway II: evidence for individualistic responses of high-altitude glaciers to millennial-scale climatic fluctuations |
title_sort |
cosmogenic 10 be and 26 al ages of holocene moraines in southern norway ii: evidence for individualistic responses of high-altitude glaciers to millennial-scale climatic fluctuations |
publisher |
SAGE Publications |
publishDate |
2008 |
url |
http://dx.doi.org/10.1177/0959683608096592 http://journals.sagepub.com/doi/pdf/10.1177/0959683608096592 |
geographic |
Norway |
geographic_facet |
Norway |
genre |
glacier |
genre_facet |
glacier |
op_source |
The Holocene volume 18, issue 8, page 1165-1177 ISSN 0959-6836 1477-0911 |
op_rights |
http://journals.sagepub.com/page/policies/text-and-data-mining-license |
op_doi |
https://doi.org/10.1177/0959683608096592 |
container_title |
The Holocene |
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18 |
container_issue |
8 |
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1165 |
op_container_end_page |
1177 |
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