globalchange  > 过去全球变化的重建
DOI: 10.1016/j.quascirev.2016.07.008
Scopus记录号: 2-s2.0-84982683722
论文题名:
Origin of the active drumlin field at Múlajökull, Iceland: New insights from till shear and consolidation patterns
作者: McCracken R.G.; Iverson N.R.; Benediktsson Í.Ö.; Schomacker A.; Zoet L.K.; Johnson M.D.; Hooyer T.S.; Ingólfsson Ó.
刊名: Quaternary Science Reviews
ISSN: 2773791
出版年: 2016
卷: 148
起始页码: 243
结束页码: 260
语种: 英语
英文关键词: Consolidation ; Drumlin ; Fabric ; Glacier ; Múlajökull ; Till
Scopus关键词: Consolidation ; Deposition ; Erosion ; Fabrics ; Glaciers ; Magnetic anisotropy ; Magnetic susceptibility ; Stratigraphy ; Anisotropy of magnetic susceptibility ; Consolidation tests ; Drumlin ; Effective stress ; Glacier forefield ; Longitudinal compression ; Subglacial channels ; Till ; Landforms ; aggradation ; azimuth ; consolidation ; deformation ; drumlin ; effective stress ; glacier surge ; lidar ; magnetic anisotropy ; relief ; sediment transport ; shear ; subglacial deposit ; till ; turbulent flow ; Iceland ; Mulajokull
英文摘要: Stratigraphic and morphologic data previously collected from the forefield of Múlajökull, Iceland, suggest that its recent surge cycles are responsible for the formation of drumlins there and that their relief reflects both deposition on drumlins and erosion between them. We have tested these ideas and aspects of leading models of drumlin formation by studying past patterns of bed deformation and effective stress in basal tills of the glacier's forefield. Patterns of till strain indicated by the anisotropy of magnetic susceptibility (AMS) of ∼2300 intact till samples indicate that till was deposited during shear deformation, with shearing azimuths and planes that conform to the drumlin morphology. Thus, till deposition occurred as drumlins grew, in agreement with LiDAR data indicating that the degree of aggradation of the glacier forefield is largest in areas subjected to the most surges. Previously described unconformities on the drumlin flanks, however, indicate that drumlin relief at Múlajökull has resulted, in part, from erosion. Given that the last surge deposited a till layer both on and between drumlins, a reasonable hypothesis is that erosion between drumlins occurred during normal (quiescent) flow of the glacier between surges. Densities of till samples, analyzed in conjunction with laboratory consolidation tests, indicate that effective stresses on the bed during such periods were on the order of 100 kPa larger between drumlins than within them, an observation consistent with subglacial channels at low water pressure occupying interdrumlin areas. Transport of sediment by turbulent flow in these channels or high effective stress adjacent to them causing enhanced till entrainment in ice or increased depths of bed deformation would promote the sediment flux divergence necessary to erode areas between drumlins. The observation that effective stresses were higher between drumlins than within them is the opposite of that presumed in leading models of drumlin formation. Moreover, the lack of AMS-fabric evidence of longitudinal compression in drumlin tills does not support some models of drumlin formation that invoke negative till-flux gradients in a deforming bed. © 2016 Elsevier Ltd
资助项目: We thank J. Amato, J. Esler, J. Friðriksson, G. Gadd, M. Harbury, L. Ives, S. Jónsson, E. Joynt, I. McBrearty, J. Schneider, C. Thomsen, and S. Tomer, for their assistance in the field. We also thank M. Bennett, T. Fisher, and the anonymous reviewer whose thoughtful comments helped to improve the paper. This work was supported by grants from the US National Science Foundation (grant EAR-1225812), the Geological Society of America Graduate Student Research Grants, The Carlsberg Foundation (grants 2008-01-0376 and 2009-01-0069), The Landsvirkjun Energy Research Fund, The University of Iceland Research Fund, the Icelandic Research Fund RANNÍS (grant 110237023), and the Royal Physiographic Society in Lund.
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/59483
Appears in Collections:过去全球变化的重建

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作者单位: Department of Geological and Atmospheric Sciences, Iowa State University, 253 Science I, 2237 Osborn Drive, Ames, IA, United States; Institute of Earth Sciences, University of Iceland, Askja, Sturlugata 7, Reykjavík, Iceland; Department of Geology, UiT the Arctic University of Norway, Postboks 6050 Langnes, Tromsø, Norway; Department of Geoscience, University of Wisconsin-Madison, Weeks Hall, 1215 West Dayton Street, Madison, WI, United States; Department of Earth Sciences, University of Gothenburg, Box 46, Göteborg, Sweden; Department of Geosciences, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, WI, United States; The University Centre in Svalbard (UNIS), P.O. Box 156, Longyearbyen, Norway

Recommended Citation:
McCracken R.G.,Iverson N.R.,Benediktsson Í.Ö.,et al. Origin of the active drumlin field at Múlajökull, Iceland: New insights from till shear and consolidation patterns[J]. Quaternary Science Reviews,2016-01-01,148
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