| DOI: | 10.1016/j.quascirev.2014.03.013
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| Scopus记录号: | 2-s2.0-84900789425
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| 论文题名: | Quaternary evolution of glaciated gneiss terrains: Pre-glacial weathering vs. glacial erosion |
| 作者: | Krabbendam M.; Bradwell T.
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| 刊名: | Quaternary Science Reviews
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| ISSN: | 2773791
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| 出版年: | 2014
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| 卷: | 95 | | 起始页码: | 20
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| 结束页码: | 42
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| 语种: | 英语
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| 英文关键词: | Fracture zone
; Glacial erosion
; Joint
; Saprolite
; Shield terrain
; Subglacial roughness
; Weathering
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| Scopus关键词: | Erosion
; Glacial geology
; Glaciers
; Joints (structural components)
; Landforms
; Lithology
; Rocks
; Tectonics
; Bedrock structures
; Chemical weathering
; Deep-fracture zones
; Fracture zone
; Glacial erosion
; Quaternary evolution
; Saprolite
; Shield terrain
; Weathering
; bedrock
; chemical weathering
; fracture zone
; geomorphology
; glacial erosion
; glacial-interglacial cycle
; gneiss
; ice sheet
; ice stream
; joint
; lithology
; peneplain
; Pleistocene
; saprolite
; scour
; shield
; terrain
; wind erosion
; Namaqualand
; Scotland
; United Kingdom
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| 英文摘要: | Vast areas previously covered by Pleistocene ice sheets consist of rugged bedrock-dominated terrain of innumerable knolls and lake-filled rock basins - the 'cnoc-and-lochan' landscape or 'landscape of areal scour'. These landscapes typically form on gneissose or granitic lithologies and are interpreted (1) either to be the result of strong and widespread glacial erosion over numerous glacial cycles; or (2) formed by stripping of a saprolitic weathering mantle from an older, deeply weathered landscape. We analyse bedrock structure, erosional landforms and weathering remnants and within the 'cnoc-and-lochan' gneiss terrain of a rough peneplain in NW Scotland and compare this with a geomorphologically similar gneiss terrain in a non-glacial, arid setting (Namaqualand, South Africa). We find that the topography of the gneiss landscapes in NW Scotland and Namaqualand closely follows the old bedrock-saprolite contact (weathering front). The roughness of the weathering front is caused by deep fracture zones providing a highly irregular surface area for weathering to proceed. The weathering front represents a significant change in bedrock physical properties. Glacial erosion (and aeolian erosion in Namaqualand) is an efficient way of stripping saprolite, but is far less effective in eroding hard, unweathered bedrock. Significant glacial erosion of hard gneiss probably only occurs beneath palaeo-ice streams. We conclude that the rough topography of glaciated 'cnoc-and-lochan' gneiss terrains is formed by a multistage process:. 1) Long-term, pre-glacial chemical weathering, forming deep saprolite with an irregular weathering front;. 2) Stripping of weak saprolite by glacial erosion during the first glaciation(s), resulting in a rough land surface, broadly conforming to the pre-existing weathering front ('etch surface');. 3) Further modification of exposed hard bedrock by glacial erosion. In most areas, glacial erosion is limited, but can be significant beneath palaeo-ice stream. The roughness of glaciated gneiss terrains is crucial for modelling of the glacial dynamics of present-day ice sheets. This roughness is shown here to depend on the intensity of pre-glacial weathering as well as glacial erosion during successive glaciations. © 2014 Natural Environment Research Council. |
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| 资源类型: | 期刊论文
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| 标识符: | http://119.78.100.158/handle/2HF3EXSE/60247
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| Appears in Collections: | 过去全球变化的重建
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作者单位: | British Geological Survey, Murchison House, Edinburgh EH6 3LA, United Kingdom
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| Recommended Citation: | |
Krabbendam M.,Bradwell T.. Quaternary evolution of glaciated gneiss terrains: Pre-glacial weathering vs. glacial erosion[J]. Quaternary Science Reviews,2014-01-01,95
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