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Subglacial cominution in the deforming bed: inferences from SEM analysis

Rose, Kathryn C. and Hart, Jane K. (2008) Subglacial cominution in the deforming bed: inferences from SEM analysis Sedimentary Geology, 203, (1-2), pp. 87-97. (doi:10.1016/j.sedgeo.2007.11.003).

Record type: Article

Abstract

This study investigates the variations in erosional processes beneath Briksdalsbreen; a Norwegian valley glacier, with a thin coarse grained deforming bed. The subglacial zone was investigated in situ, close to the central glacial flow line (Site A) and close to the valley wall (Site B), via boreholes. The till was collected using two different sediment samplers and the bed was examined using a borehole video camera. In order to evaluate how representative borehole sampling was of the subglacial environment, the results from in situ subglacial samples were compared with random samples taken from an exposed subglacial surface in the glacier foreland, as well as a sample taken from the site after glacier retreat. The results indicated that the texture of the exposed subglacial surface was similar to in situ samples from subglacial Site B (close to the valley wall), and that the samples collected with the ‘small’ sediment sampler had the closest fit. SEM analysis revealed eroded quartz grains at both sites as a result of rotation (abrasion) and fracture. The samples from close to the valley wall were very poorly sorted, with evidence for rounding and preservation of pre-weathered surfaces, which suggest that a relatively simple pattern of erosion from crushing to rotation dominated. However, the till from the centre of the glacier was better sorted, more angular, and with few pre-weathered surfaces. We suggest that this results from a more complex glacial erosional history associated with greater strain and longer residence time within the deforming layer. When compared with other deformation tills, it was confirmed that there is a relationship between grain size and erosional style. Clay-rich tills show little comminution, fine sand-rich tills generate a significant silt component, whilst the coarse sand-rich tills at Briksdalsbreen showed complex deformational styles but no significant silt component.

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More information

Published date: 10 January 2008
Keywords: till sedimentology, borehole studies, SEM, subglacial erosion

Identifiers

Local EPrints ID: 56921
URI: http://eprints.soton.ac.uk/id/eprint/56921
ISSN: 0037-0738
PURE UUID: b0df8552-4a9c-4a5a-ac08-9ba936e7f5d1
ORCID for Jane K. Hart: ORCID iD orcid.org/0000-0002-2348-3944

Catalogue record

Date deposited: 18 Aug 2008
Last modified: 17 Jul 2017 14:30

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Contributors

Author: Kathryn C. Rose
Author: Jane K. Hart ORCID iD

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