Late Quaternary glaciation in the Hebrides sector of the continental shelf: Was St Kilda overrun by the British-Irish Ice Sheet?
Until recently, the British-Irish Ice Sheet (BIIS) was thought to have reached no farther than a mid-continental shelf position in the Hebrides Sector, NW Britain, during the last glaciation (traditional model). However, recent discovery of widespread shelf-edge moraines in this sector has led to a...
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2014
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ftunivzuerich:oai:www.zora.uzh.ch:104492 2024-10-13T14:08:05+00:00 Late Quaternary glaciation in the Hebrides sector of the continental shelf: Was St Kilda overrun by the British-Irish Ice Sheet? Hiemstra, John F Shakesby, Richard A Vieli, Andreas 2014 application/pdf https://www.zora.uzh.ch/id/eprint/104492/ https://www.zora.uzh.ch/id/eprint/104492/1/2014_HiemstraVieliBoreas2014.pdf https://doi.org/10.5167/uzh-104492 https://doi.org/10.1111/bor.12097 eng eng Wiley-Blackwell Publishing, Inc. https://www.zora.uzh.ch/id/eprint/104492/1/2014_HiemstraVieliBoreas2014.pdf doi:10.5167/uzh-104492 doi:10.1111/bor.12097 urn:issn:0300-9483 info:eu-repo/semantics/closedAccess Hiemstra, John F; Shakesby, Richard A; Vieli, Andreas (2014). Late Quaternary glaciation in the Hebrides sector of the continental shelf: Was St Kilda overrun by the British-Irish Ice Sheet? Boreas, 44(1):178-196. Institute of Geography 910 Geography & travel Journal Article PeerReviewed info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion 2014 ftunivzuerich https://doi.org/10.5167/uzh-10449210.1111/bor.12097 2024-09-18T00:49:47Z Until recently, the British-Irish Ice Sheet (BIIS) was thought to have reached no farther than a mid-continental shelf position in the Hebrides Sector, NW Britain, during the last glaciation (traditional model). However, recent discovery of widespread shelf-edge moraines in this sector has led to a suggestion of much more extensive ice (Atlantic Shelf model). The position of the St Kilda archipelago, approximately mid-way between the Outer Hebrides and the continental shelf edge, makes it ideal as an onshore location to test which of the two competing models is more viable. To this end, we (i) reassessed the characteristics, stratigraphy and morphology of the Quaternary sediments exposed on the largest island (Hirta), and (ii) applied time-dependent 2D numerical modelling of possible glacier formation on Hirta. Instead of three glaciations (as previously suggested), we identified evidence of only two, including one of entirely local derivation. The numerical model supports the view that this glaciation was in the form of two short glaciers occupying the two valleys that dominate Hirta. The good state of preservation of the glacial sediments and associated moraine of this local glaciation indicate relatively recent formation. In view of the low inferred equilibrium line altitude of the glacier associated with the best morphological evidence (∼120 m), considerable thickness of slope deposits outside the glacial limits and evidence of only one rather than two tills, a Late Devensian rather than Younger Dryas age is preferred for this glaciation. Re-examination of the submarine moraine pattern from available bathymetry suggests that the ice sheet was forced to flow around St Kilda, implying that the ice was of insufficient thickness to overrun the islands. Accepting this leaves open the possibility that a St Kilda nunatak supported local ice while the ice sheet extended to the continental shelf edge. Article in Journal/Newspaper Ice Sheet University of Zurich (UZH): ZORA (Zurich Open Repository and Archive |
institution |
Open Polar |
collection |
University of Zurich (UZH): ZORA (Zurich Open Repository and Archive |
op_collection_id |
ftunivzuerich |
language |
English |
topic |
Institute of Geography 910 Geography & travel |
spellingShingle |
Institute of Geography 910 Geography & travel Hiemstra, John F Shakesby, Richard A Vieli, Andreas Late Quaternary glaciation in the Hebrides sector of the continental shelf: Was St Kilda overrun by the British-Irish Ice Sheet? |
topic_facet |
Institute of Geography 910 Geography & travel |
description |
Until recently, the British-Irish Ice Sheet (BIIS) was thought to have reached no farther than a mid-continental shelf position in the Hebrides Sector, NW Britain, during the last glaciation (traditional model). However, recent discovery of widespread shelf-edge moraines in this sector has led to a suggestion of much more extensive ice (Atlantic Shelf model). The position of the St Kilda archipelago, approximately mid-way between the Outer Hebrides and the continental shelf edge, makes it ideal as an onshore location to test which of the two competing models is more viable. To this end, we (i) reassessed the characteristics, stratigraphy and morphology of the Quaternary sediments exposed on the largest island (Hirta), and (ii) applied time-dependent 2D numerical modelling of possible glacier formation on Hirta. Instead of three glaciations (as previously suggested), we identified evidence of only two, including one of entirely local derivation. The numerical model supports the view that this glaciation was in the form of two short glaciers occupying the two valleys that dominate Hirta. The good state of preservation of the glacial sediments and associated moraine of this local glaciation indicate relatively recent formation. In view of the low inferred equilibrium line altitude of the glacier associated with the best morphological evidence (∼120 m), considerable thickness of slope deposits outside the glacial limits and evidence of only one rather than two tills, a Late Devensian rather than Younger Dryas age is preferred for this glaciation. Re-examination of the submarine moraine pattern from available bathymetry suggests that the ice sheet was forced to flow around St Kilda, implying that the ice was of insufficient thickness to overrun the islands. Accepting this leaves open the possibility that a St Kilda nunatak supported local ice while the ice sheet extended to the continental shelf edge. |
format |
Article in Journal/Newspaper |
author |
Hiemstra, John F Shakesby, Richard A Vieli, Andreas |
author_facet |
Hiemstra, John F Shakesby, Richard A Vieli, Andreas |
author_sort |
Hiemstra, John F |
title |
Late Quaternary glaciation in the Hebrides sector of the continental shelf: Was St Kilda overrun by the British-Irish Ice Sheet? |
title_short |
Late Quaternary glaciation in the Hebrides sector of the continental shelf: Was St Kilda overrun by the British-Irish Ice Sheet? |
title_full |
Late Quaternary glaciation in the Hebrides sector of the continental shelf: Was St Kilda overrun by the British-Irish Ice Sheet? |
title_fullStr |
Late Quaternary glaciation in the Hebrides sector of the continental shelf: Was St Kilda overrun by the British-Irish Ice Sheet? |
title_full_unstemmed |
Late Quaternary glaciation in the Hebrides sector of the continental shelf: Was St Kilda overrun by the British-Irish Ice Sheet? |
title_sort |
late quaternary glaciation in the hebrides sector of the continental shelf: was st kilda overrun by the british-irish ice sheet? |
publisher |
Wiley-Blackwell Publishing, Inc. |
publishDate |
2014 |
url |
https://www.zora.uzh.ch/id/eprint/104492/ https://www.zora.uzh.ch/id/eprint/104492/1/2014_HiemstraVieliBoreas2014.pdf https://doi.org/10.5167/uzh-104492 https://doi.org/10.1111/bor.12097 |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_source |
Hiemstra, John F; Shakesby, Richard A; Vieli, Andreas (2014). Late Quaternary glaciation in the Hebrides sector of the continental shelf: Was St Kilda overrun by the British-Irish Ice Sheet? Boreas, 44(1):178-196. |
op_relation |
https://www.zora.uzh.ch/id/eprint/104492/1/2014_HiemstraVieliBoreas2014.pdf doi:10.5167/uzh-104492 doi:10.1111/bor.12097 urn:issn:0300-9483 |
op_rights |
info:eu-repo/semantics/closedAccess |
op_doi |
https://doi.org/10.5167/uzh-10449210.1111/bor.12097 |
_version_ |
1812814684859924480 |