Micromorphological evidence for the role of pressurised water in the formation of large-scale thrust-block moraines in Melasveit, western Iceland
Abstract Pressurised meltwater has a major impact on ice dynamics, as well as on sedimentary and deformational processes occurring below/in front of glaciers and ice sheets, but its role in glaciotectonic processes is yet to be fully understood. This study explores micro- and macroscale structures d...
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crcambridgeupr:10.1017/qua.2019.48 2024-09-15T18:13:30+00:00 Micromorphological evidence for the role of pressurised water in the formation of large-scale thrust-block moraines in Melasveit, western Iceland Sigfúsdóttir, Thorbjörg Phillips, Emrys Benediktsson, Ívar Örn 2019 http://dx.doi.org/10.1017/qua.2019.48 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033589419000486 en eng Cambridge University Press (CUP) http://creativecommons.org/licenses/by/4.0/ Quaternary Research volume 93, page 88-109 ISSN 0033-5894 1096-0287 journal-article 2019 crcambridgeupr https://doi.org/10.1017/qua.2019.48 2024-07-31T04:03:58Z Abstract Pressurised meltwater has a major impact on ice dynamics, as well as on sedimentary and deformational processes occurring below/in front of glaciers and ice sheets, but its role in glaciotectonic processes is yet to be fully understood. This study explores micro- and macroscale structures developed within décollements in two thrust-block moraines of Late Weichselian age in Melasveit, western Iceland. The aim is to investigate how pressurised subglacial meltwater can aid the dislocation and transport of large, unfrozen and unlithified sediment blocks by glaciers. A detailed model is constructed for the development of the thrust-block moraines and the microscale processes occurring along their detachments during thrusting. The detachments are characterized by relatively thin zones of crosscutting hydrofractures, which reflect fluctuating water pressures during glaciotectonism. Little evidence of shearing is observed along the leading edges of the thrusts in both moraines. This is supported by high water pressures along the detachments and indicates that the thrust blocks were initially decoupled from the underlying deposits. As the thrust moraines evolved, an increased amount of shear occurred in between events of sediment liquefaction, hydrofracturing, and fluid escape. This was followed by progressive locking up of the detachments and eventual cessation in the accretion of the thrust blocks. Article in Journal/Newspaper Iceland Cambridge University Press Quaternary Research 93 88 109 |
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Open Polar |
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Cambridge University Press |
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crcambridgeupr |
language |
English |
description |
Abstract Pressurised meltwater has a major impact on ice dynamics, as well as on sedimentary and deformational processes occurring below/in front of glaciers and ice sheets, but its role in glaciotectonic processes is yet to be fully understood. This study explores micro- and macroscale structures developed within décollements in two thrust-block moraines of Late Weichselian age in Melasveit, western Iceland. The aim is to investigate how pressurised subglacial meltwater can aid the dislocation and transport of large, unfrozen and unlithified sediment blocks by glaciers. A detailed model is constructed for the development of the thrust-block moraines and the microscale processes occurring along their detachments during thrusting. The detachments are characterized by relatively thin zones of crosscutting hydrofractures, which reflect fluctuating water pressures during glaciotectonism. Little evidence of shearing is observed along the leading edges of the thrusts in both moraines. This is supported by high water pressures along the detachments and indicates that the thrust blocks were initially decoupled from the underlying deposits. As the thrust moraines evolved, an increased amount of shear occurred in between events of sediment liquefaction, hydrofracturing, and fluid escape. This was followed by progressive locking up of the detachments and eventual cessation in the accretion of the thrust blocks. |
format |
Article in Journal/Newspaper |
author |
Sigfúsdóttir, Thorbjörg Phillips, Emrys Benediktsson, Ívar Örn |
spellingShingle |
Sigfúsdóttir, Thorbjörg Phillips, Emrys Benediktsson, Ívar Örn Micromorphological evidence for the role of pressurised water in the formation of large-scale thrust-block moraines in Melasveit, western Iceland |
author_facet |
Sigfúsdóttir, Thorbjörg Phillips, Emrys Benediktsson, Ívar Örn |
author_sort |
Sigfúsdóttir, Thorbjörg |
title |
Micromorphological evidence for the role of pressurised water in the formation of large-scale thrust-block moraines in Melasveit, western Iceland |
title_short |
Micromorphological evidence for the role of pressurised water in the formation of large-scale thrust-block moraines in Melasveit, western Iceland |
title_full |
Micromorphological evidence for the role of pressurised water in the formation of large-scale thrust-block moraines in Melasveit, western Iceland |
title_fullStr |
Micromorphological evidence for the role of pressurised water in the formation of large-scale thrust-block moraines in Melasveit, western Iceland |
title_full_unstemmed |
Micromorphological evidence for the role of pressurised water in the formation of large-scale thrust-block moraines in Melasveit, western Iceland |
title_sort |
micromorphological evidence for the role of pressurised water in the formation of large-scale thrust-block moraines in melasveit, western iceland |
publisher |
Cambridge University Press (CUP) |
publishDate |
2019 |
url |
http://dx.doi.org/10.1017/qua.2019.48 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033589419000486 |
genre |
Iceland |
genre_facet |
Iceland |
op_source |
Quaternary Research volume 93, page 88-109 ISSN 0033-5894 1096-0287 |
op_rights |
http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1017/qua.2019.48 |
container_title |
Quaternary Research |
container_volume |
93 |
container_start_page |
88 |
op_container_end_page |
109 |
_version_ |
1810451274175348736 |