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| Titel |
Origin and significance of dispersed facies basal ice: Svínafellsjökull, Iceland |
| VerfasserIn |
Simon Cook, Darrel Swift, David Graham, Nicholas Midgley |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039663
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| Zusammenfassung |
| Dispersed facies basal ice (massive ice with dispersed debris aggregates) outcrops at the
margins of many ice masses and is important to glaciologists because of the information it
provides about the nature of subglacial conditions and processes in the deep interior of
glaciers and ice sheets. There has been little agreement, however, about how it forms with
possible mechanisms including regelation and water flow through the intercrystalline vein
network, strain-induced metamorphism of firnified glacier ice, shearing of basal debris-rich
ice, freeze-on of subglacial water, and incorporation of surface debris into glacier ice. We test
these established hypotheses at the temperate glacier Svínafellsjökull, southeast Iceland, and
show that none fully account for dispersed facies characteristics here. From analysis of
physical, sedimentological and stable isotope (δ18O and δD) characteristics we suggest
that dispersed facies forms from a combination of regelation and strain-induced
metamorphism of debris-laden ice originally entrained by tectonic processes at the base of
an icefall. We suggest that a terminal overdeepening may serve to further thicken
dispersed facies as the glacier flows against a prominent reverse bedslope. There
may also be a lack of subglacial drainage across the overdeepening which further
allows dispersed facies to survive in thicknesses up to ~20m despite the temperate
location. Our results demonstrate that, despite its low sediment content (~1.6%),
the thick layer of dispersed facies contributes a higher annual sediment flux than
other more debris-rich basal ice types. Hence dispersed facies and the processes
that create it should not be overlooked in assessments of glacial sediment budgets. |
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