Collaborative Research: Subglacial Deforming Beds as Erosive and Sedimentary Agents: An Experimental Study of Particle Comminution and Rock Erosion

合作研究：冰下变形床作为侵蚀剂和沉积剂：颗粒粉碎和岩石侵蚀的实验研究

• 批准号: 9805083
• 负责人: Barclay Kamb
• 金额: $ 0.6万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-02-01 至 2001-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9805083&HistoricalAwards=false
• 关键词: Collaborative; Research; Subglacial; Deforming; Beds

9805083KambSubglacial sediment deformation is becoming increasingly accepted as the new, distinct, and perhaps even predominant mechanism of fast ice flow and till generation. By this mechanism, extensive layers of till may be generated, transported at fast rates, and deposited entirely subglacially. At present, two fundamental assumptions are made in the deforming-bed models of ice flow and till generation: (1) that these rapidly deforming beds erode underlying bedrock efficiently enough to sustain the required high sediment fluxes; and (2) that they can produce the evidence of debris comminution which is commonly observed in tills. Results of observational and experimental investigations of the till from beneath Ice Stream B. West Antarctica suggest that these assumptions changes significantly the presently existing understanding of deforming beds. However, it is not clear whether the observations from Ice Stream B till can be extrapolated to other subglacial environments. A series of experiments is proposed here to study the rates of particle comminution and bedrock erosion by shearing till. In these experiments, an existing ring shear device will be used to shear six different types of till to large strains (~100,000) under effective normal stresses which are applicable to the deforming-bed model (6 kPa N 100 kPa). Comparison of pre-shear and post-shear granulometry, composition of clay-size fraction, as well as sand grain shape and micromorphology will determine the extent of particle comminution. The rate of rock erosion will be measured on rock plates of common lithologies mounted in the ring shear device. The results will be used to test the general validity of the assumptions (1) and (2). The collected data will provide an experimental basis for quantitative formulations of erosion and comminution that can be used in future modeling of deforming beds. Finally, these experiments have the potential to yield solid sedimentological criteria for testing whether a given till may or many not have been generated fully by subglacial deformation.

9805083 KambSubglacial沉积物变形越来越被接受为快速冰流和冰碛物生成的新的，独特的，甚至可能是主要的机制。 通过这种机制，可以产生大面积的冰碛层，并以快速的速度搬运，然后完全沉积在冰下。 目前，在冰流和冰碛物生成的变形床模型中有两个基本假设：（1）这些快速变形的床足以有效地侵蚀下伏基岩，以维持所需的高沉积物通量;（2）它们可以产生冰碛物中常见的碎屑粉碎证据。 冰流B下冰碛物的观测和实验研究结果。西南极洲表明，这些假设大大改变了目前现有的认识变形床。 然而，目前尚不清楚冰流B的观测结果是否可以外推到其他冰下环境。 本文通过一系列的试验研究了切土作用下的颗粒破碎率和基岩侵蚀率。 在这些实验中，将使用现有的环形剪切装置在适用于变形床模型（6 kPa N 100 kPa）的有效正应力下将六种不同类型的冰碛物剪切至大应变（~ 100，000）。 剪切前和剪切后的粒度分析、粘土粒级组成以及砂粒形状和微形态的比较将确定颗粒粉碎的程度。 岩石侵蚀速率将在安装在环形剪切装置中的普通岩性的岩石板上测量。 结果将用于检验假设（1）和（2）的一般有效性。 所收集的数据将提供一个实验基础的侵蚀和粉碎，可用于未来的变形床建模的定量配方。 最后，这些实验有可能产生坚实的沉积学标准，用于测试一个给定的冰碛物是否完全由冰下变形产生。