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Geomorphology and weathering characteristics of erratic boulder trains on Tierra del Fuego, southernmost South America : implications for dating of glacial deposits.

Darvill, Christopher M. and Bentley, Michael J. and Stokes, Chris R. (2015) 'Geomorphology and weathering characteristics of erratic boulder trains on Tierra del Fuego, southernmost South America : implications for dating of glacial deposits.', Geomorphology., 228 . pp. 382-397.

Abstract

Erratic boulder trains (EBTs) are a useful glacial geomorphological feature because they reveal former ice flow trajectories and can be targeted for cosmogenic nuclide exposure dating. However, understanding how they are transported and deposited is important because this has implications for palaeoglaciological reconstructions and the pre-exposure and/or erosion of the boulders. In this study, we review previous work on EBTs, which indicates that they may form subglacially or supraglacially but that large angular boulders transported long distances generally reflect supraglacial transport. We then report detailed observations of EBTs from Tierra del Fuego, southernmost South America, where their characteristics provide a useful framework for the interpretation of previously published cosmogenic nuclide exposure dates. We present the first comprehensive map of the EBTs and analyse their spatial distribution, size, and physical appearance. Results suggest that they were produced by one or more supraglacial rock avalanches in the Cordillera Darwin and were then transported supraglacially for 100s of kilometres before being deposited. Rock surface weathering analysis shows no significant difference in the weathering characteristics of a sequence of EBTs, previously hypothesized to be of significantly different age (i.e., different glacial cycles). We interpret this to indicate that the EBTs are much closer in age than previous work has implied. This emphasises the importance of understanding EBT formation when using them for cosmogenic nuclide exposure dating.

Item Type:Article
Keywords:Erratic boulder train, Supraglacial, Subglacial, Rock avalanche, Weathering, Cosmogenic nuclide exposure dating.
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1016/j.geomorph.2014.09.017
Publisher statement:© 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).
Date accepted:No date available
Date deposited:03 October 2014
Date of first online publication:January 2015
Date first made open access:No date available

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