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: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=741627
• 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，加拿大多次被大冰盖覆盖，留下了多样化的冰川地貌和景观遗产，这些遗产仍然没有得到很好的理解或绘制。冰川地质学的发现重新激发了冰川地质学的活力，因为冰盖(现代和古代)不是缓慢流动的穹顶，整个冰川的流动速度稳定，而是包含许多快速流动的冰流，这些冰流是长达1000公里、宽150公里的冰的走廊，速度高达每年10公里。这一发现对北美和其他地区的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，尚未通过适当的冰盖范围范围的研究来充分评估。在北美和斯堪的纳维亚半岛的最后一次劳伦蒂德和科迪勒冰盖中，300多条以前的冰流在它们的床上留下了数以百万计的流线型地貌(鼓形、巨型冰川线条)，由沉积物(软沉积物床)或岩石(硬床，如加拿大盾)或两者的组合组成。到目前为止，对于这些地貌的起源(S)还没有达成共识。现在第一次可以绘制详细的地图，通过使用倡导者及其小组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非常大的数字数据集(例如35TB)。这揭示了迄今为止未曾见过的细节，表明鼓声和MSGL组成了一个床形连续体，并随着冰盖设计其床层以降低摩擦阻力和更快地流动而演变。研究将从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山体滑坡上流线型表面的研究中获得信息，在这些研究中，在不同规模上开发了类似的床型。在项目结束时，我们将以迄今无法实现的比例和详细程度准确绘制北美和芬兰的冰川床图，并为流线型河床的演化和地下地质建立形成沉积学模型。冰盖模型师、研究现代冰川的冰川学家(他们的冰床无法进入)和矿产勘探行业需要有关冰川下矿化碎片的侵蚀和运输的信息，加拿大人口稠密的城市地区的地下水资源管理人员需要这些信息，这些地区建立在以前的古冰川床上。拟议的研究将使人们深入了解大型大陆冰盖下的冰下过程和碎片通量，并将为工业界和学术界培养高素质的学生，学习机器学习和高分辨率地形数据集的空间分析，这些数据集现在变得越来越可用。长期目标是制作一张新的加拿大冰川地图，以取代50年前最后一次使用低分辨率航空照片完成的地图。