Sedimentary signatures of basal ice formation and their preservation in ice-marginal sediments

COOK, S.J., GRAHAM, D.J., SWIFT, D.A. and MIDGLEY, N.G., 2011. Sedimentary signatures of basal ice formation and their preservation in ice-marginal sediments. Geomorphology, 25 (1), pp. 122-131.

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Abstract

Reconstruction of subglacial processes from sedimentological evidence is central to our understanding of glaciological conditions beneath former ice masses. At Svinafellsjbkull, southeast Iceland, we assess the extent to which two different processes of basal ice formation (regelation and glaciohydraulic supercooling) can be identified from ice-marginal sediments. Our results indicate that the sedimentary characteristics of deposits produced by these two processes can be distinguished from one another and that it may be possible to recognise evidence of these processes in Quaternary sediments and to reconstruct their spatial pervasiveness. Sediments derived from the melting of regelation basal ice have (i) a massive structure; (ii) a sediment matrix (0 to 10Ф) dominated by coarse sand; and (iii) a higher proportion of angular clasts than supercool basal ice and associated sediments. Sediments derived from "supercool" basal ice (i) can be either massive or layered; (ii) tend to have a silt-dominated matrix; and (iii) contain a slightly higher proportion of rounded and well-rounded clasts than 1 regelation basal ice and sediments. Previous studies indicate that the dominance of silt within supercool basal ice may be unique to this process, and hence, supercooling should leave a readily recognisable signature in the sedimentary record. Our results from Svínafellsjökull lend support to that idea, although we suggest that further work is required to assess whether silt dominance is a process signature diagnostic of supercooling, and in particular, the extent to which subglacial sediment supply determines the sedimentary character of basal ice fades and associated sediments.

Item Type: Journal article
Publication Title: Geomorphology
Creators: Cook, S.J., Graham, D.J., Swift, D.A. and Midgley, N.G.
Publisher: Elsevier
Date: 2011
Volume: 25
Number: 1
Identifiers:
NumberType
10.1016/j.geomorph.2010.08.018DOI
Divisions: Schools > School of Animal, Rural and Environmental Sciences
Depositing User: EPrints Services
Date Added: 09 Oct 2015 10:08
Last Modified: 09 Jun 2017 13:20
URI: http://irep.ntu.ac.uk/id/eprint/8430

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