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Polyphase structural evolution of a fine-grained, fold-dominated end moraine, Bruarjokull surge-type glacier, Iceland

Benediktsson, Ivar Örn LU (2012) In Jökull: Journal of the Glaciological and Geological Societies of Iceland 62. p.167-184
Abstract
The glaciotectonic architecture and structural evolution of a fine-grained end moraine formed by the 1890 glacier surge of Bruarjokull is described from four excavated cross-sections. The end moraine ridge is a morphological expression of a marginal sedimentary wedge formed during the last days of the surge. The actual end-moraine ridge was formed on the last day of the 1890 surge when the glacier became coupled to the bed and ploughed into the reverse slope of the marginal sediment wedge. Ductile deformation, favoured by high porewater pressure, dominated the construction of the end moraine while brittle deformation was induced when porewater pressure decreased, particularly at the end of the surge. Thus, the deformation was polyphase,... (More)
The glaciotectonic architecture and structural evolution of a fine-grained end moraine formed by the 1890 glacier surge of Bruarjokull is described from four excavated cross-sections. The end moraine ridge is a morphological expression of a marginal sedimentary wedge formed during the last days of the surge. The actual end-moraine ridge was formed on the last day of the 1890 surge when the glacier became coupled to the bed and ploughed into the reverse slope of the marginal sediment wedge. Ductile deformation, favoured by high porewater pressure, dominated the construction of the end moraine while brittle deformation was induced when porewater pressure decreased, particularly at the end of the surge. Thus, the deformation was polyphase, developing from open folding to multiple overfolding when porewater pressure was high and finally to overthrusting, faulting and shearing at the very end of the surge when porewater pressure dropped severely upon porewater blow-out in front of the moraine. This structural continuum is exhibited by the four cross-sections. The glaciotectonic stress was absorbed within a relatively narrow zone due to high friction along a basal decollement. A new model illustrates the structural evolution of a fine-grained, fold-dominated end moraine and may serve as an analogue to similar end moraines in modern and Pleistocene environments. (Less)
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organization
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Contribution to journal
publication status
published
subject
in
Jökull: Journal of the Glaciological and Geological Societies of Iceland
volume
62
pages
167 - 184
publisher
Jöklarannsóknafélag Íslands
external identifiers
  • wos:000318580900012
ISSN
0449-0576
language
English
LU publication?
yes
id
73041de9-b78a-4a19-a294-020fbd7090e3 (old id 3935710)
date added to LUP
2013-07-15 10:06:59
date last changed
2016-04-16 02:27:15
@article{73041de9-b78a-4a19-a294-020fbd7090e3,
  abstract     = {The glaciotectonic architecture and structural evolution of a fine-grained end moraine formed by the 1890 glacier surge of Bruarjokull is described from four excavated cross-sections. The end moraine ridge is a morphological expression of a marginal sedimentary wedge formed during the last days of the surge. The actual end-moraine ridge was formed on the last day of the 1890 surge when the glacier became coupled to the bed and ploughed into the reverse slope of the marginal sediment wedge. Ductile deformation, favoured by high porewater pressure, dominated the construction of the end moraine while brittle deformation was induced when porewater pressure decreased, particularly at the end of the surge. Thus, the deformation was polyphase, developing from open folding to multiple overfolding when porewater pressure was high and finally to overthrusting, faulting and shearing at the very end of the surge when porewater pressure dropped severely upon porewater blow-out in front of the moraine. This structural continuum is exhibited by the four cross-sections. The glaciotectonic stress was absorbed within a relatively narrow zone due to high friction along a basal decollement. A new model illustrates the structural evolution of a fine-grained, fold-dominated end moraine and may serve as an analogue to similar end moraines in modern and Pleistocene environments.},
  author       = {Benediktsson, Ivar Örn},
  issn         = {0449-0576},
  language     = {eng},
  pages        = {167--184},
  publisher    = {Jöklarannsóknafélag Íslands},
  series       = {Jökull: Journal of the Glaciological and Geological Societies of Iceland},
  title        = {Polyphase structural evolution of a fine-grained, fold-dominated end moraine, Bruarjokull surge-type glacier, Iceland},
  volume       = {62},
  year         = {2012},
}