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Debris entrainment by basal freeze-on and thrusting during the 1995-1998 surge of Kuannersuit Glacier on Disko Island, west Greenland

Larsen, Nicolaj Krog LU ; Kronborg, Christian; Yde, Jacob C. and Knudsen, Niels Tvis (2010) In Earth Surface Processes and Landforms 35(5). p.561-574
Abstract
Kuannersuit Glacier, a valley glacier on Disko Island in west Greenland, experienced a major surge from 1995 to 1998 where the glacier advanced 10.5 km and produced a similar to 65 m thick stacked sequence of debris-rich basal ice and meteoric glacier ice. The aim of this study is to describe the tectonic evolution of large englacial thrusts and the processes of basal ice formation using a multiproxy approach including structural glaciology, stable isotope composition (delta O-18 and delta D), sedimentology and ground-penetrating radar. We argue that the major debris layers that can be traced in the terminal zone represent englacial thrusts that were formed early during the surge. Thrust overthrow was at least 200-300 m and this lead to a... (More)
Kuannersuit Glacier, a valley glacier on Disko Island in west Greenland, experienced a major surge from 1995 to 1998 where the glacier advanced 10.5 km and produced a similar to 65 m thick stacked sequence of debris-rich basal ice and meteoric glacier ice. The aim of this study is to describe the tectonic evolution of large englacial thrusts and the processes of basal ice formation using a multiproxy approach including structural glaciology, stable isotope composition (delta O-18 and delta D), sedimentology and ground-penetrating radar. We argue that the major debris layers that can be traced in the terminal zone represent englacial thrusts that were formed early during the surge. Thrust overthrow was at least 200-300 m and this lead to a 30 m thick repetition of basal ice at the ice margin. It is assumed that the englacial thrusting was initiated at the transition between warm ice from the interior and the cold snout. The basal debris-rich ice was mainly formed after the thrusting phase. Two sub-facies of stratified basal ice have been identified; a lower massive ice facies (S-M) composed of frozen diamict enriched with heavy stable isotopes overlain by laminated ice facies (S-L) consisting of millimetre thick lamina of alternating debris-poor and debris-rich ice. We interpret the stratified basal ice as a continuum formed mainly by freeze-on processes and localized regelation. First laminated basal ice is formed and as meltwater is depleted more sediment is entrained and finally the glacier freezes to the base and massive diamict is frozen-on. The increased ability to entrain sediments may partly be associated with higher basal freezing rates enhanced by loss of frictional heat from cessation of fast flow and conductive cooling through a thin heavily crevassed ice during the final phase of the glacier surge. The dispersed basal ice facies (D) was mainly formed by secondary processes where fine-grained sediment is mobilized in the vein system of ice. Our results have important implications for understanding the significance of basal ice formation and englacial thrusting beneath fast-flowing glaciers and it provides new information about the development of landforms during a glacier surge. Copyright (C) 2010 John Wiley & Sons, Ltd. (Less)
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author
organization
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type
Contribution to journal
publication status
published
subject
keywords
englacial, surge glacier, basal debris-rich ice, debris entrainment, thrusting, ice dynamics
in
Earth Surface Processes and Landforms
volume
35
issue
5
pages
561 - 574
publisher
John Wiley & Sons
external identifiers
  • wos:000277695000006
  • scopus:77951044545
ISSN
0197-9337
DOI
10.1002/esp.1945
language
English
LU publication?
yes
id
309613f9-2bed-40d1-bbb0-cf0ad12a7877 (old id 1617923)
date added to LUP
2010-06-21 08:58:35
date last changed
2018-05-29 11:07:28
@article{309613f9-2bed-40d1-bbb0-cf0ad12a7877,
  abstract     = {Kuannersuit Glacier, a valley glacier on Disko Island in west Greenland, experienced a major surge from 1995 to 1998 where the glacier advanced 10.5 km and produced a similar to 65 m thick stacked sequence of debris-rich basal ice and meteoric glacier ice. The aim of this study is to describe the tectonic evolution of large englacial thrusts and the processes of basal ice formation using a multiproxy approach including structural glaciology, stable isotope composition (delta O-18 and delta D), sedimentology and ground-penetrating radar. We argue that the major debris layers that can be traced in the terminal zone represent englacial thrusts that were formed early during the surge. Thrust overthrow was at least 200-300 m and this lead to a 30 m thick repetition of basal ice at the ice margin. It is assumed that the englacial thrusting was initiated at the transition between warm ice from the interior and the cold snout. The basal debris-rich ice was mainly formed after the thrusting phase. Two sub-facies of stratified basal ice have been identified; a lower massive ice facies (S-M) composed of frozen diamict enriched with heavy stable isotopes overlain by laminated ice facies (S-L) consisting of millimetre thick lamina of alternating debris-poor and debris-rich ice. We interpret the stratified basal ice as a continuum formed mainly by freeze-on processes and localized regelation. First laminated basal ice is formed and as meltwater is depleted more sediment is entrained and finally the glacier freezes to the base and massive diamict is frozen-on. The increased ability to entrain sediments may partly be associated with higher basal freezing rates enhanced by loss of frictional heat from cessation of fast flow and conductive cooling through a thin heavily crevassed ice during the final phase of the glacier surge. The dispersed basal ice facies (D) was mainly formed by secondary processes where fine-grained sediment is mobilized in the vein system of ice. Our results have important implications for understanding the significance of basal ice formation and englacial thrusting beneath fast-flowing glaciers and it provides new information about the development of landforms during a glacier surge. Copyright (C) 2010 John Wiley & Sons, Ltd.},
  author       = {Larsen, Nicolaj Krog and Kronborg, Christian and Yde, Jacob C. and Knudsen, Niels Tvis},
  issn         = {0197-9337},
  keyword      = {englacial,surge glacier,basal debris-rich ice,debris entrainment,thrusting,ice dynamics},
  language     = {eng},
  number       = {5},
  pages        = {561--574},
  publisher    = {John Wiley & Sons},
  series       = {Earth Surface Processes and Landforms},
  title        = {Debris entrainment by basal freeze-on and thrusting during the 1995-1998 surge of Kuannersuit Glacier on Disko Island, west Greenland},
  url          = {http://dx.doi.org/10.1002/esp.1945},
  volume       = {35},
  year         = {2010},
}