The character, structure and origin of the basal ice layer of a surge-type glacier
Abstract The basal ice layer of surge-type Variegated Glacier, Alaska, appears to have formed by a combination of (i) open-system freezing of subglacial meltwaters over both rigid and unconsolidated substrates; (ii) apron over-riding during surge-induced glacier advance; (iii) incorporation of glaci...
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Cambridge University Press (CUP)
1994
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Online Access: | http://dx.doi.org/10.1017/s0022143000007413 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000007413 |
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crcambridgeupr:10.1017/s0022143000007413 2024-09-15T18:07:32+00:00 The character, structure and origin of the basal ice layer of a surge-type glacier Sharp, Martin Jouzel, Jean Hubbard, Bryn Lawson, Wendy 1994 http://dx.doi.org/10.1017/s0022143000007413 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000007413 en eng Cambridge University Press (CUP) Journal of Glaciology volume 40, issue 135, page 327-340 ISSN 0022-1430 1727-5652 journal-article 1994 crcambridgeupr https://doi.org/10.1017/s0022143000007413 2024-07-31T04:04:04Z Abstract The basal ice layer of surge-type Variegated Glacier, Alaska, appears to have formed by a combination of (i) open-system freezing of subglacial meltwaters over both rigid and unconsolidated substrates; (ii) apron over-riding during surge-induced glacier advance; (iii) incorporation of glacier ice by recumbent folding, thrust-faulting and nappe over-riding during down-glacier propagation of a surge front; and (iv) post-formational metamorphism involving recrystallization, partial internal melting and squeezing out of meltwaters and dissolved gases. Structural evidence and the characteristics of debris entrained in ice facies formed by basal freezing suggest that the layer includes a lower element formed under surge conditions and an upper element formed during the quiescent phase of a surge cycle. The lower element is depleted in comminution products and enriched in medium gravel, while the upper element contains comminution products but virtually no medium gravel. This distinction is attributed to the efficiency of bedrock fracture and meltwater flushing of comminution products under surge conditions. The basal ice layer thickens from <1 m to >13 m down-glacier in a manner consistent with the magnitude of horizontal shortening induced by the 1982–83 surge. Thickening is largely tectonic in origin, and the style and intensity of folding and thrust faulting change down-glacier as the magnitude of horizontal shortening increases. Tectonic processes associated with the down-glacier propagation of surge fronts therefore appear to be capable of creating thick basal ice layers which allow extensive supraglacial sedimentation of subglacially derived debris. Article in Journal/Newspaper glacier Journal of Glaciology Alaska Cambridge University Press Journal of Glaciology 40 135 327 340 |
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Open Polar |
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Cambridge University Press |
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crcambridgeupr |
language |
English |
description |
Abstract The basal ice layer of surge-type Variegated Glacier, Alaska, appears to have formed by a combination of (i) open-system freezing of subglacial meltwaters over both rigid and unconsolidated substrates; (ii) apron over-riding during surge-induced glacier advance; (iii) incorporation of glacier ice by recumbent folding, thrust-faulting and nappe over-riding during down-glacier propagation of a surge front; and (iv) post-formational metamorphism involving recrystallization, partial internal melting and squeezing out of meltwaters and dissolved gases. Structural evidence and the characteristics of debris entrained in ice facies formed by basal freezing suggest that the layer includes a lower element formed under surge conditions and an upper element formed during the quiescent phase of a surge cycle. The lower element is depleted in comminution products and enriched in medium gravel, while the upper element contains comminution products but virtually no medium gravel. This distinction is attributed to the efficiency of bedrock fracture and meltwater flushing of comminution products under surge conditions. The basal ice layer thickens from <1 m to >13 m down-glacier in a manner consistent with the magnitude of horizontal shortening induced by the 1982–83 surge. Thickening is largely tectonic in origin, and the style and intensity of folding and thrust faulting change down-glacier as the magnitude of horizontal shortening increases. Tectonic processes associated with the down-glacier propagation of surge fronts therefore appear to be capable of creating thick basal ice layers which allow extensive supraglacial sedimentation of subglacially derived debris. |
format |
Article in Journal/Newspaper |
author |
Sharp, Martin Jouzel, Jean Hubbard, Bryn Lawson, Wendy |
spellingShingle |
Sharp, Martin Jouzel, Jean Hubbard, Bryn Lawson, Wendy The character, structure and origin of the basal ice layer of a surge-type glacier |
author_facet |
Sharp, Martin Jouzel, Jean Hubbard, Bryn Lawson, Wendy |
author_sort |
Sharp, Martin |
title |
The character, structure and origin of the basal ice layer of a surge-type glacier |
title_short |
The character, structure and origin of the basal ice layer of a surge-type glacier |
title_full |
The character, structure and origin of the basal ice layer of a surge-type glacier |
title_fullStr |
The character, structure and origin of the basal ice layer of a surge-type glacier |
title_full_unstemmed |
The character, structure and origin of the basal ice layer of a surge-type glacier |
title_sort |
character, structure and origin of the basal ice layer of a surge-type glacier |
publisher |
Cambridge University Press (CUP) |
publishDate |
1994 |
url |
http://dx.doi.org/10.1017/s0022143000007413 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000007413 |
genre |
glacier Journal of Glaciology Alaska |
genre_facet |
glacier Journal of Glaciology Alaska |
op_source |
Journal of Glaciology volume 40, issue 135, page 327-340 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000007413 |
container_title |
Journal of Glaciology |
container_volume |
40 |
container_issue |
135 |
container_start_page |
327 |
op_container_end_page |
340 |
_version_ |
1810444925958881280 |