Sedimentology and architecture of ice stream beds

冰河床的沉积学和结构

• 批准号: RGPIN-2020-07149
• 负责人: Eyles, Nicholas
• 金额: $ 3.13万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=762165
• 关键词: Sedimentology; architecture; ice; stream; beds

Canada was covered by large ice sheets many times in the last 2.5 million years leaving a diverse heritage of glacial landforms and landscapes which are still not well understood or mapped. The discipline of glacial geology has been re-energized by the finding that ice sheets (modern and ancient) were not slow-flowing domes with steady-state ice flow velocities throughout, but instead contained many fast-flowing ice streams which are corridors of ice as much as 1000 km long and 150 km wide with velocities as high as 10 km a year. This discovery poses new questions about the origins of glaciated landscapes and sediments in North America and elsewhere and has important applied significance yet to be fully evaluated by research on the appropriate ice sheet-wide scale. More than 300 former ice streams within the last Laurentide and Cordilleran ice sheets in North America and in Scandinavia left many millions of streamlined landforms on their beds (drumlins, megascale glacial lineations) composed of either sediment (a soft bed of sediment) or rock (a hard bed e.g., Canadian Shield) or combinations of the two. To date there is no consensus on the origin(s) of these landforms. Detailed mapping is now attainable for the first time, using innovative machine learning techniques developed by the proponent and his group to analyse very large digital data sets (e.g., 35 Tb) of high-resolution imagery such as LiDAR. This reveals hitherto unseen detail that shows that drumlins and MSGLs comprise a bedform continuum and evolve as the ice sheet engineers its bed to lower frictional drag and flow faster. Research will be informed by relevant modelling of how man-made surfaces evolve under friction and by studies of streamlined surfaces on faults and large landslides where analogous bedforms are developed on various scales. At the conclusion of the project we will have accurately mapped ice stream beds  in North America and in Finland at a scale and level of detail hitherto unachievable, and established formative sedimentological models for the evolution and subsurface geology of streamlined bedforms. This information is required by ice sheet modelers, glaciologists working on modern ice streams (where their beds are inaccessible) and the mineral exploration industry requiring information on the erosion and transport of mineralized debris under ice streams, and by groundwater resource managers in densely-populated urban areas in Canada that are built on former beds of paleo-ice streams. The proposed research will generate insights into subglacial processes and debris fluxes below large continental ice sheets and will train highly-qualified students for industry and academia in machine learning and the spatial analysis of high-resolution topographic data sets that are now becoming increasingly available. The long term objective is a new Glacial Map of Canada to replace that which was last completed 50 years ago using low resolution air photographs.

在过去的250万年里，加拿大多次被大冰原覆盖，留下了各种各样的冰川地貌和景观遗产，这些遗产至今仍未被很好地理解或绘制出来。冰原（现代的和古代的）不是缓慢流动的圆顶，整个冰流速度稳定，而是包含许多快速流动的冰流，这些冰流是长达1000公里，150公里宽，速度高达每年10公里的冰走廊，这一发现使冰川地质学的学科重新活跃起来。这一发现对北美和其他地区冰川景观和沉积物的起源提出了新的问题，并具有重要的应用意义，有待在适当的冰盖范围内的研究进行充分评估。在北美洲和斯堪的那维亚，在最后的劳伦泰德冰原和科迪勒兰冰原中，有300多条冰流在它们的床上留下了数百万条流线型地貌（drumlins，巨型冰川线），它们由沉积物（沉积物的软床）或岩石（硬床，如加拿大地盾）或两者的组合组成。到目前为止，对这些地貌的起源还没有达成一致意见。现在，通过使用支持者及其团队开发的创新机器学习技术来分析激光雷达等高分辨率图像的大型数字数据集（例如35tb），首次可以实现详细的地图绘制。这揭示了迄今为止未见的细节，表明鼓状体和MSGLs组成了一个床状连续体，并随着冰盖对其床的改造而演变，以降低摩擦阻力，加快流动。关于人造表面在摩擦下如何演变的相关模型，以及对断层和大型滑坡上的流线型表面的研究，将为研究提供信息，在这些地方，类似的河床在不同尺度上形成。在项目结束时，我们将以迄今为止无法实现的规模和细节水平准确绘制北美和芬兰的冰河床，并建立流线型河床演化和地下地质的形成性沉积学模型。冰盖建模者、研究现代冰流的冰川学家（他们的床是无法到达的）、需要冰流下矿化碎片侵蚀和运输信息的矿产勘探行业，以及加拿大人口稠密的城市地区的地下水资源管理人员都需要这些信息，这些城市地区建在以前的古冰流床上。拟议的研究将深入了解大型大陆冰盖下的冰下过程和碎屑通量，并将为工业界和学术界培养机器学习和高分辨率地形数据集空间分析方面的高素质学生，这些数据集现在越来越多。长期目标是绘制新的加拿大冰川地图，以取代50年前使用低分辨率航空照片完成的冰川地图。