Terminal zone glacial sediment transfer at a temperate overdeepened glacier system

QUATERNARY SCIENCE REVIEWS

卷:180

Article

Swift, D. A.¹  Cook, S. J.²  Graham, D. J.³  Midgley, N. G.⁴  Fallick, A. E.⁵  Storrar, R.⁶  Rodrigo, M. Toubes⁷  Evans, D. J. A.⁸ 

[1] Univ Sheffield, Dept Geog, Winter St, Sheffield S10 2TN, S Yorkshire, England

[2] Univ Dundee, Sch Social Sci, Geog, Dundee DD1 4HN, Scotland

[3] Loughborough Univ, Dept Geog, Polar & Alpine Res Ctr, Loughborough LE11 3TU, Leics, England

[4] Nottingham Trent Univ, Sch Anim Rural & Environm Sci, Nottingham NG25 0QF, Notts, England

[5] Scottish Univ, Environm Res Ctr, Glasgow G75 0QF, Lanark, Scotland

[6] Sheffield Hallam Univ, Dept Nat & Built Environm, Howard St, Sheffield S1 1WB, S Yorkshire, England

[7] Manchester Metropolitan Univ, Sch Sci & Environm, Manchester M1 SGD, Lancs, England

[8] Univ Durham, Dept Geog, South Rd, Durham DH1 3LE, England

关键词: Present;    Quaternary;    Glaciation;    Glaciology;    Europe;    Geomorphology;    Glacial;    Sediment transport;    Glacial erosion;    Glacial hydrology;   

DOI  :  10.1016/j.quascirev.2017.11.027

来源: Elsevier

【 摘 要 】

Continuity of sediment transfer through glacial systems is essential to maintain subglacial bedrock erosion, yet transfer at temperate glaciers with overdeepened beds, where subglacial fluvial sediment transport should be greatly limited by adverse slopes, remains poorly understood. Complex multiple transfer processes in temperate overdeepened systems has been indicated by the presence of large frontal moraine systems, supraglacial debris of mixed transport origin, thick basal ice sequences, and englacial thrusts and eskers. At Svinafellsjokull, thrusts comprising decimetre-thick debris-rich bands of stratified facies ice of basal origin, with a coarser size distribution and higher clast content than that observed in basal ice layers, contribute substantially to the transfer of subglacial material in the terminal zone. Entrainment and transfer of material occurs by simple shear along the upper surface of bands and by strain-induced deformation of stratified and firnified glacier ice below. Thrust material includes rounded and well-rounded clasts that are also striated, indicating that fluvial bedload is deposited as subglacial channels approach the overdeepening and then entrained along thrusts. Substantial transfer also occurs within basal ice, with facies type and debris content dependent on the hydrological connectedness of the adverse slope. A process model of transfer at glaciers with terminal overdeepenings is proposed, in which the geometry of the overdeepening influences spatial patterns of ice deformation, hydrology, and basal ice formation. We conclude that the significance of thrusting in maintaining sediment transfer continuity has likely been overlooked by glacier sediment budgets and glacial landscape evolution studies. (C) 2017 The Authors. Published by Elsevier Ltd.

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