A conceptual model of valley incision, planation and terrace formation during cold and arid permafrost conditions of Pleistocene southern England

Murton, Julian B and Belshaw, Roger K (2011) A conceptual model of valley incision, planation and terrace formation during cold and arid permafrost conditions of Pleistocene southern England. Quaternary Research, 75 (2). pp. 385-394. ISSN 0033-5894

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Abstract

Staircases of gravelly river terrace deposits in southern England occupy valleys typically underlain by frostsusceptible and brecciated bedrocks. The valleys developed during the Quaternary by alternating episodes of (1) brecciation, incision and planation through the bedrock, forming wide low-relief erosion surfaces; and (2)aggradation in braidplains of gravel a few meters thick that bury the erosion surfaces. A conceptual model to account for some of the terraces proposes that brecciation resulted from ice segregation in the ice-rich layer in the upper meters of Pleistocene permafrost, making them vulnerable to fluvial thermal erosion and therefore predisposing the bedrock to planation. The low gradients of the valleys were adjusted such that rivers transferred fine materials out of the basins but lacked the competence to remove gravel, which therefore accumulated within floodplains. The model challenges the prevailing view of incision during climate transitions. It attributes incision and planation to very cold and arid permafrost conditions, when rivers had limited discharges and hillslopes supplied limited volumes of stony debris into valley bottoms.

Item Type: Article
Schools and Departments: School of Global Studies > Geography
Depositing User: Julian Murton
Date Deposited: 06 Feb 2012 15:22
Last Modified: 04 Apr 2012 13:38
URI: http://sro.sussex.ac.uk/id/eprint/11938
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