Assessing subglacial processes from diatom fragmentation patterns
Assessing subglacial processes from diatom fragmentation patterns
复制标题
从硅藻破碎模式评估冰下过程
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
T. Hooyer
中科院分区：
文献类型：
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作者：
R. Scherer;C. Sjunneskog;N. Iverson;T. Hooyer
重建过去冰盖的规模和冰川风格需要解释复杂的冰川沉积相。我们使用硅藻，南极大陆架沉积物的主要组成部分，推断这些存款的物理条件下，侵位。硅藻破碎的程度和不同地层年龄的硅藻在冰川沉积物中的存在提供了定性测量冰川混合和运输的手段。在这里，我们报告了一个实验校准的硅藻破碎指数，提供了一个简单而客观的方法，评估海洋冰川沉积沉积物的亚剪切的程度。通过使用一个环剪切装置，使硅藻沉积物的应力与罗斯冰流下的应力相当，我们定量评估了硅藻粉碎模式，导致压实和渐进的剪切应力。细长的羽状硅藻被发现打破不成比例的盘状中心硅藻受到剪切应力时，因此，一个简单的比例未破碎的中心羽状硅藻提供了一个可靠的衡量过去的剪切。环剪切结果与一套先前分析的沉积物，代表了各种冰川，冰川海洋，和半远洋设置的罗斯海和冰下罗斯湾的比较表明，该指数可以用来估计相对冰下应力在这种设置。
Reconstructing the size and glacial style of past ice-sheet advances requires interpreting complex glacial sedimentary facies. We use diatoms, a major component of Antarctic continental shelf deposits, to infer the physical conditions under which these deposits were emplaced. The degree of diatom fragmentation and the presence of diatoms of varying stratigraphic age in glacial sediments provide means to qualitatively gauge glacial mixing and transport. Here we report an experimentally calibrated index of diatom fragmentation that provides a simple but objective method of assessing the degree of subshearing imparted on marine glacial sedimentary deposits. By using a ring-shear device to subject diatomaceous sediment to stresses comparable to those beneath the Ross ice streams, we quantitatively assess patterns of diatom comminution resulting from compaction and from progressive shear stress. Elongate pennate diatoms are found to break disproportionately to discoid centric diatoms when subjected to shear stress; thus, a simple ratio of unbroken centric to pennate diatoms provides a reliable gauge of past shearing. Comparison of ring-shear results with a suite of previously analyzed sediments that represent a variety of glacial, glacial-marine, and hemipelagic settings of the Ross Sea and subglacial Ross Embayment demonstrates that this index can be employed for estimating relative subglacial stresses in this setting.