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

Edward J. Fleming, Harold Lovell, Carl T. E. Stevenson, Michael S. Petronis, Douglas I. Benn, Michael J. Hambrey, Ian J. Fairchild

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    Abstract

    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.
    Original languageEnglish
    Pages (from-to)2263-2278
    Number of pages16
    JournalJournal of Geophysical Research: Earth Surface
    Volume118
    Issue number4
    DOIs
    Publication statusPublished - Dec 2013

    Keywords

    • basal ice
    • magnetic anisotropy
    • structural glaciology
    • deformation
    • strain

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