Cryptic post-depositional reworking in aeolian sediments revealed by the anisotropy of magnetic susceptibility
Cryptic post-depositional reworking in aeolian sediments revealed by the anisotropy of magnetic susceptibility
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DOI：
10.1016/j.epsl.2004.05.029
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发表时间：
2004-08
影响因子：
5.3
通讯作者：
Subir K. Banerjee
中科院分区：
文献类型：
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作者：
Subir K. Banerjee
我们的磁化率各向异性（AMS）调查的金山台阶（GHS 2）和中途之家（HH 3）黄土和古土壤剖面在阿拉斯加中部证实，沉积后改造黄土在金山台阶已经发生，更重要的是，确定了改造的深度间隔。在GHS 2中，7.80 m深度以下的黄土大部分已被改造。如文献所述，中途宿舍场地的黄土主要是未受扰动的风成存款。然而，我们已经确定了HH3中已返工的两个间隔。我们推断，从深度变化的AMS取向分布在GHS 2的永久冻土的存在下，在过去的主导活动机制产生所观察到的变形。多年冻土黄土表现为（1）不透水层集中和沟流，最有可能是地下水，（2）作为刚体进行旋转和横向平移。一个现代的模拟集中流动的不透水层被确定在HH3。
Our anisotropy of magnetic susceptibility (AMS) investigation of the Gold Hill Steps (GHS2) and Halfway House (HH3) loess and paleosol profiles in central Alaska confirms that post-depositional reworking of loess at Gold Hill Steps has taken place and, of greater importance, identifies the reworked depth intervals. In GHS2, the majority of the loess below 7.80 m depth has been reworked. The loess at the Halfway House site is, as stated in the literature, a predominantly undisturbed aeolian deposit. However, we have identified two intervals that have been reworked in HH3. We infer from the depth variation of the AMS orientation distribution at GHS2 that the presence of permafrost in the past was the dominant active mechanism producing the observed deformations. Permafrost loess behaved (1) as impermeable layers focusing and channeling flow, most likely that of groundwater, and (2) as rigid bodies undergoing rotations and lateral translations. A modern analogue of focused flow by an impermeable layer is identified at HH3.