Magnetic fabrics in the basal ice of a surge-type glacier

Anisotropy of magnetic susceptibility (AMS) has been shown to provide specific useful information regarding the kinematics of deformation within subglacially deformed sediments. Here we present results from debris‐rich basal glacier ice to examine deformation associated with glacier motion. Basal ic...

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Bibliographic Details
Published in:Journal of geophysical research. Earth surface 2013-12, Vol.118 (4), p.2263-2278
Main Authors: Fleming, Edward J., Lovell, Harold, Stevenson, Carl T. E., Petronis, Michael S., Benn, Douglas I., Hambrey, Michael J., Fairchild, Ian J.
Format: Article
Language:English
Subjects:
Alignment
Anisotropy
basal ice
Deformation
Earth sciences
Earth, ocean, space
Exact sciences and technology
External geophysics
Fabrics
Geophysics
Geophysics: general, magnetic, electric and thermic methods and properties
Glacial drift
Glaciers
Ice
Internal geophysics
Kinematics
Low temperature
magnetic anisotropy
Magnetic permeability
Magnetism
Marine and continental quaternary
Sediments
Snow. Ice. Glaciers
strain
structural glaciology
Surficial geology
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Summary:Anisotropy of magnetic susceptibility (AMS) has been shown to provide specific useful information regarding the kinematics of deformation within subglacially deformed sediments. Here we present results from debris‐rich basal glacier ice to examine deformation associated with glacier motion. Basal ice samples were collected from Tunabreen, a polythermal surge‐type glacier in Svalbard. The magnetic fabrics recorded show strong correlation with structures within the ice, such as sheath folds and macroscopic stretching lineations. Thermomagnetic, low‐temperature susceptibility, varying field susceptibility, and isothermal remanent magnetism acquisition experiments reveal that the debris‐rich basal ice samples have a susceptibility and anisotropy dominated by paramagnetic phases within the detrital sediment. Sediment grains entrained within the basal ice are inferred to have rotated into a preferential alignment during deformation associated with flow of the glacier. An up‐glacier directed plunge of magnetic lineations and subtle deviation from bulk glacier flow at the margins highlight the importance of noncoaxial strain during surge propagation. The results suggest that AMS can be used as an ice petrofabric indicator for investigations of glacier deformation and interactions with the bed. Key Points Fabrics in basal ice are measured through the novel use of AMS AMS fabrics reflect the preferential alignment of detrital mineral grains AMS analysis reveals the kinematics of basal ice deformation
ISSN:2169-9003
2169-9011
DOI:10.1002/jgrf.20144