Fabric characteristics of subaerial slope deposits

Authors

  • PASCAL BERTRAN,

    1. Institut du Quatenaire, UMR 9933 CNRS-Université de Bordeaux I, Bâtiment de Géologie, Avenue des facultés, F-33405 Talence, France
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  • BERNARD HÉTU,

    1. Module de Géographie, Université de Québec à Rimouski, 300 allée des Ursulines, Rimouski, Québec G5L 3A1, Canada
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  • JEAN-PIERRE TEXIER,

    1. Institut du Quatenaire, UMR 9933 CNRS-Université de Bordeaux I, Bâtiment de Géologie, Avenue des facultés, F-33405 Talence, France
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  • HENK VAN STEIJN

    1. The Netherlands Centre for Geo-ecological Research, Faculty of Geographical Sciences, Utrecht University, PO Box 80.115, NL-3508 TC Utrecht, The Netherlands
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ABSTRACT

The clast fabrics of certain types of terrestrial slope deposits are reviewed and compared, including the deposits of rockfalls, solifluction, debris flows, dry grain flows, frost-coated clast flows and run-off. The analysis is based on modern deposits in active environments. The study shows that fabric characteristics allow discrimination between ‘collective’and individual movement of rock particles. The individual particle movement generally results in a random clast orientation, whereas the processes of ‘collective’movement typically create distinct preferred orientations. The highest fabric strengths together with low values of spherical variance are found in solifluction deposits. A survey of Pleistocene slope deposits indicates, however, that clast fabric has to be used with caution in the identification of past slope dynamics, because significant post-depositional changes may occur during ageing and burial of deposits. The diagnostic significance of fabric characteristics may also be low due to the overlap of the statistical values that typify different processes.

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