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Lookup NU author(s): Dr Matthew Burke, Professor Andrew RussellORCiD
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Eskers have been used to infer the dynamics and palaeohydrology of large ice sheets yet there are few suitable contemporary analogues for esker sedimentation during Quaternary glaciations. Consequently, depositional models are based upon morphological and sedimentological studies of palaeo-eskers, which have poorly constrained depositional timescales. We identify the controls on the large-scale sedimentary architecture of a large (>700 m long,<30 m high)esker deposited during a single, high-magnitude jökulhlaup at Skeiðarárjökull, Iceland. Over 3.8 km of ground-penetrating radar (GPR) line were collected (in 2006 & 2007) as grids on all workable areas of the esker and associated supraglacial ice-walled canyon-fill sediment. Six main radar facies were identified: 1) discontinuous, undular reflections, interpreted as trough-cross strata, associated with the development of antidune sequences;2)sub-horizontal reflections(dip<10°),associated with deposition of upper stage gravel plane beds;3)moderate to high-angle (>10 °) inclined reflections, dipping upstream, interpreted as backset accretion associated with large-scale bedform development; 4)high-angle (>15 °)inclined reflections, dipping downstream, interpreted as foreset accretion associated with large-scale bedform progradation;5)point source reflectors, interpreted as zones of boulder clustering; and 6)zones of enhanced attenuation, bounded on the upper surface by a continuous reflection sub-parallel to the ground surface, interpreted as buried ice associated with the conduit/channel base. These data suggest that deposition took place within a non-uniform englacial conduit, which has resulted in major proximal-distal variations in sedimentary architecture. The complexities observed are a direct consequence of both variations in sediment supply and within-event evolution of conduit geometry. This has produced a greater complexity than previously anticipated for a single event. This study provides the first detailed insight into the large-scale sedimentary architecture of a single event jökulhlaup esker, providing a contemporary analogue for esker deposition during Quaternary glaciations.
Author(s): Burke MJ, Woodward J, Russell AJ, Fleisher PJ, Bailey PK
Publication type: Article
Publication status: Published
Journal: Quaternary Science Reviews
Year: 2008
Volume: 27
Issue: 19-20
Pages: 1829-1847
ISSN (print): 0277-3791
ISSN (electronic): 1873-457X
Publisher: Pergamon
URL: http://dx.doi.org/10.1016/j.quascirev.2008.06.012
DOI: 10.1016/j.quascirev.2008.06.012
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