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The Athabasca fluting field, Alberta, Canada: implications for the formation of large-scale fluting (erosional lineations)

机译:加拿大艾伯塔省的阿萨巴斯卡长笛演奏场:对形成大型长笛演奏的影响(侵蚀线条)

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Current drumlin and fluting hypotheses, centred on processes of formation, erosion and deposition by subglacial deformation, accretion by lodgement, glacial erosion, and meltwater erosion and deposition, rarely receive comprehensive field testing. This paper documents the morphology, internal structure, and landscape associations of the Athabasca fluting field, Alberta, and discusses how well these characteristics are explained by postulated fluting forming processes. Fluting hypotheses are comprehensively tested by this approach and their rejection or acceptance are firmly based on field observation and knowledge of processes. Using multiple criteria, fluting is shown to be erosional and not to be a product of pervasive subglacial deformation or accretion by lodgement. Morphology, landscape associations, bed truncation, plus glaciofluvial lags and gravel on fluting ridges are inferred to support erosion by meltwater. Intact primary bedding, synsedimentary faults and injection structures very close to the landsurface, showing no sign of shear deformation, are used to reject erosion by subglacial deformation. Fluting is shown to be closely associated with tunnel channels and indicates that these channels were overtopped by broad hoods that formed the fluting field and eroded anabranching tracts over the length of the Alberta Plains. Prior to fluting formation, sequences with melt-out and lodgement till, conduit sediment and boulder lags record net deposition over an extended time period. Diapirism prior to fluting formation marks a period of extreme pressure gradients which are related to bed separation. Following fluting formation, there was only minimal landscape modification, dominated by glaciofluvial and glaciolacustrine deposition, not glacial processes. This progression is presented as evidence for two very different glacial regimes separated by a short period with diapirism and extensive landscape modification by meltwater erosion. We note that the study area was glaciated only once, during the Late Wisconsinian, and it follows that glacial sedimentation and landscape modification were confirmed to this single glacial episode. (C) 2000 Elsevier Science Ltd. All rights reserved. [References: 75]
机译:当前的鼓林和槽纹假说,主要集中在冰下变形引起的形成,侵蚀和沉积,沉积,冰川侵蚀以及熔体水的侵蚀和沉积形成的过程中,很少接受全面的现场测试。本文记录了艾伯塔省Athabasca笛子场的形态,内部结构和景观联系,并讨论了通过假想的笛子形成过程如何很好地解释这些特征。长笛假说已通过这种方法进行了全面测试,其否定或接受完全基于现场观察和过程知识。使用多个标准,表明槽纹是侵蚀性的,而不是普遍的冰川下变形或堆积引起的积积。可以推断出形态,景观联系,河床截断以及槽脊上的冰川河流滞后和砾石可支持融水侵蚀。完好的原生层理,同沉积断层和非常接近地表的注入结构(没有剪切变形的迹象)被用来抵抗冰下变形造成的侵蚀。凹槽与隧道通道紧密相关,表明这些通道被形成风笛区域的宽大罩盖覆盖,并侵蚀了亚伯大平原全长的分水岭。在形成槽纹之前,伴随着融化和沉积直到导管沉积物和巨石滞后的序列记录了较长时间的净沉积。沟槽形成之前的透水现象标志着一段与床层分离有关的极端压力梯度。在形成槽纹之后,仅有最小的景观变化,主要是冰川流和冰川湖沉积,而不是冰川过程。这种进展被证明是两个非常不同的冰川体系的证据,这些冰川体系在短时期内被底辟作用分隔开来,并因融化水侵蚀而广泛地改变了景观。我们注意到,在威斯康星州晚期期间,研究区仅被冰川化了一次,因此可以证实,对这一单个冰川事件而言,冰川沉积和景观变化都得到了证实。 (C)2000 Elsevier ScienceLtd。保留所有权利。 [参考:75]

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