Glacier-Permafrost interactions, debris transfer mechanisms and the development of distinctive sediment-landform associations in a High Arctic glacial environment: the case of Fountain Glacier, Bylot Island, Nunavut, Canada

Waller, R.I.; Hambrey, M.J.; Moorman, B.J.

Abstract

Detailed investigations of the sediment-landform associations being actively created in modern-day periglacial environments provide the opportunity to constrain the linkages between process and form that underpin palaeoenvironmental reconstructions. Glacial geomorphologists have commonly assumed that cold-based and polythermal glaciers underlain by permafrost are slow moving, geomorphologically inactive and therefore of limited research interest. However, recent research in both modern and ancient periglacial environments has illustrated the ability of glaciers and permafrost to couple and interact, leading to the operation of distinctive processes and the development of distinctive sediment-landform associations. Despite this, our knowledge and understanding of the mechanisms of debris transfer, the characteristics of the associated sediments and the diversity of geomorphic features associated with High Arctic glacial environments remain limited. This research describes the distinctive landforms, lithofacies and sediment-landform associations characteristic of an Arctic outlet glacier on Bylot Island in the Canadian High Arctic. The island features a mountainous central icefield from which a series of outlet-glaciers flow towards the coastal lowlands. With a mean annual air temperature of approximately -15°C, these glaciers terminate in an area of continuous permafrost estimated to be between 200-400 m in thickness. As such it constitutes an ideal location in which to examine the geomorphic processes and products associated with glacier-permafrost interactions. The observations reported were made primarily at the margin and foreland of Fountain Glacier, a polythermal glacier 16 km in length associated with a core of warm ice covered by a layer of cold ice that extends to the glacier margins. Field observation and mapping showed the glacier margin to be characterised by a distinctive landform assemblage comprising boulder-dominated surfaces and moraine ridges (a number of which were ice-cored), areas of heavily weathered and shattered bedrock, incised lateral meltwater channels, outwash braidplains and large proglacial icings (Aufeis) (figure 1). In addition to these newly created landforms, recession of part of the margin has revealed an intact tundra surface complete with biologically-viable vegetation that showed little if any glacial modification associated with its inundation during the Little Ice Age. Significant glacial sediment transfer occurred through a prominent debris-rich basal ice layer dominated by sub-angular and angular material of up to boulder size. The basal ice layer and ice margin as a whole displayed extensive evidence of glaciotectonic deformation intimately associated with the structural glaciology of the glacier as a whole. Thrusting was observed to elevate basal material from the basal ice to the glacier surface where the material contributed to a supraglacial sediment flux. Fluvial sediment transfer was associated primarily with a series of ice-marginal meltwater systems producing the only lithofacies with a significant percentage of rounded clasts. The glacial sediment-landform association at Fountain Glacier displays a number of distinctive elements illustrative of the specific geomorphic processes active in this environment. Bedrock shattering is predominant with there being little evidence of glacial abrasion, thereby leading to the development of glacigenic lithofacies with a surprising degree of angularity. In spite of the cold climatic conditions and limited meltwater production, fluvial processes remain important geomorphologically, leading to the erosion of lateral meltwater channels, the deposition of small outwash surfaces and the generation of large proglacial icings. The most enigmatic element however relates not to the new features being actively created but to the ability of the glacier to preserve delicate vegetated tundra surfaces during ice advance. The close proximity of these intact surfaces with more heavily modified areas suggests a spatial variability in process that merits further investigation and explanation.

Citation

Waller, R., Hambrey, M., & Moorman, B. (2016). Glacier-Permafrost interactions, debris transfer mechanisms and the development of distinctive sediment-landform associations in a High Arctic glacial environment: the case of Fountain Glacier, Bylot Island, Nunavut, Canada. In XI. International Conference On Permafrost – Book of Abstracts, 20 – 24 June 2016, Potsdam, Germany (106-107). https://doi.org/10.2312/GFZ.LIS.2016.001

• Conference Name: XI. International Conference on Permafrost
• Conference Location: Potsdam, Germany
• Start Date: Jun 20, 2016
• End Date: Jun 24, 2016
• Publication Date: Jun 20, 2016
• Pages: 106-107
• Series Title: XI. International Conference on Permafrost
• Book Title: XI. International Conference On Permafrost – Book of Abstracts, 20 – 24 June 2016, Potsdam, Germany
• DOI: https://doi.org/10.2312/GFZ.LIS.2016.001
• Publisher URL: https://media.gfz-potsdam.de/bib/ICOP/ICOP_2016_Book_of_Abstracts.pdf