ドラムリンの成因と氷床底環境-氷底堆積物の変形か氷底水流か- The Problem of Drumlin Formation, and Glacial Geological Reconstruction of Sub-ice-sheet Environments : Deformation of Subglacial Sediments or Subglacial Floods?

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Geomorphological and sedimentological processes beneath modern glaciers and ice sheet s have not been observed directly and are poorly understood. On the contrary, abundant glacial landscapes can be observed, which provide us with evidence about processes underway at the beds of the past ice sheets. Consequently, careful studies of glacial landforms and sediments provide a wealth of information of these processes.<BR>During the last decade, there have been various debates regarding subglacial landforms and their formation processes: drumlins is a major issue, and no satisfactorye xplanation of their mode of formation has yet been obtained. By overviewing recent research on the drumlin problem, this article attempts to draw attention to the major concepts and controversies behind the formation of subglacial landform, together with new developments in understanding the subglacial environment. The most recent explanations for drumlin formation have been examined in the light of our knowledge of the subglacial environment. In particular, J. Shaw and his co-workers draw attention to the significance and the implication of subglacial meltwater processes. They suggested that large-scale meltwater floods were responsible for the formation of some drumlins. Later, erosional drumlins, bedrock erosional marks, tunnel channels, and Rogen moraine were added to the forms resulting from catastrophic floods. Conversely, G.S. Boulton developed a semi-quantitative flow model for the deformation of rapidly deforming soft sediments (A-horizon) on the basis of field observations.<BR>The drumlin problem stands as a conspicuous instance of how much there is still to understand about the interplay of glacier motion, sediments, topography, and subglacial environmental conditions. It is thus emphasized that accumrate explanations of the complexities of subglacial environments are necessary to understand subglacial landform development, sediment deposition, and other geomorphic processes at the ice/bed interface, together with extraglacial effects of ice sheet dynamics on fluvial systems, marine sedimentation, ocean currents, and climate.

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各種コード

  • NII論文ID(NAID)
    10002238300
  • NII書誌ID(NCID)
    AN00322536
  • 本文言語コード
    JPN
  • 資料種別
    REV
  • ISSN
    0022135X
  • NDL 記事登録ID
    4548259
  • NDL 雑誌分類
    ZM41(科学技術--地球科学)
  • NDL 請求記号
    Z15-169
  • データ提供元
    CJP書誌  CJP引用  NDL  NII-ELS  J-STAGE 
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