Boudinage: A Source Of Stratigraphic Disturbance In Glacial Ice In Central Greenland
Boudinage: A Source Of Stratigraphic Disturbance In Glacial Ice In Central Greenland
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布迪纳奇：格陵兰中部冰川地层扰动的来源
DOI：
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发表时间：
1990
影响因子：
3.4
通讯作者：
E. Waddington
中科院分区：
文献类型：
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作者：
J. Cunningham;E. Waddington
摘要回顾了分层流体界面稳定性的流体动力学模型。该模型预测，不规则性的边界上的刚性层，嵌入在一个软矩阵，是不稳定的纯剪切流，当压缩是正常的层。在这样一个层上的扰动可以生长形成对称的捏涨结构，称为石香肠。该模型预测的初始扰动增长率的边界上的间冰期冰层。我们发现，在冰鸿沟，不规则的桑格蒙层边界不会运动学衰减，因为层变薄。冰元素建模是用来确定应变历史的Sangamon冰下的分水岭首脑会议，格陵兰岛。这段历史表明，在过去的9万年里，相对于地层厚度，边界的不规则性至少增加了26倍。其结果可能是严重的扭曲或切断层。穿透冰层的岩心孔可能会发现异常厚或薄的冰柱，从而导致错误的环境和气候解释。无线电回声探测可用于寻找石香肠带，取芯时应避免石香肠带。初始扰动可能来自质量平衡的空间变化或瞬态流场。
Abstract A hydrodynamic model of interface stability in a stratified fluid is reviewed. The model predicts that irregularities on the boundaries of a stiff layer, embedded in a soft matrix, are unstable in pure shearing flow, when compression is normal to the layer. Perturbations on such a layer can grow to form symmetric pinch-and-swell structures called boudins. The model predicts initial perturbation growth rates on the boundaries of an interglacial period ice layer. We find that, beneath an ice divide, irregularities on the Sangamon layer boundaries will not kinematically decay, as the layer thins. Finite-element modelling is used to determine the strain history of Sangamon ice beneath the divide at Summit, Greenland. That history suggests boundary irregularities have grown, relative to layer thickness, at least 26 fold over the past 90000 years. The result may be severe distortion or severing of the layer. Core holes penetrating the layer may recover anomalously thick or thin columns of ice resulting in erroneous environmental and climatic interpretations. Radio echo-sounding may be useful in searching for zones of boudinage, which should be avoided when coring. Initial perturbations might arise from mass-balance spatial variations or from transient flow fields.