Using digital mapping and cosmogenic 10Be to assess glacial landscape modification in west-central Keewatin, Arctic Canada

The west-central Keewatin region of northern Canada preserves a rich record of former ice sheets and their impact on the landscape. The diverse assemblage of glacial landforms in the region reflects spatial variations in glacial modification driven by changes in basal thermal regime, subglacial hydrology, and ice-flow dynamics, all of which are key to reconstructing the history and behaviour of palaeo-ice sheets. Resolving how these landforms relate to changes in basal regime and glacial modification requires integrated datasets such as geomorphological mapping and to provide the robust reconstructions needed for climate and ice-sheet models.

Our work aims to provide both a qualitative and quantitative assessment of glacial landscape modification in the west-central Keewatin region of the Northwest Territories and mainland Nunavut using two independent proxies: geomorphic mapping and cosmogenic nuclide concentrations. We used the ArcticDEM and Landsat 8 imagery to remotely map This new inventory of landforms, integrated with existing mapping, provides a qualitative assessment of glacial landsystems and landscape modification across the Keewatin region. As a quantitative proxy for glacial modification from the last glacial period(s), we collected 10 bedrock and 7 boulder samples for cosmogenic ¹⁰Be measurement along a north-south transect east of Dubawnt Lake, Nunavut. The sample transect was informed by glacial geomorphic mapping and was selected to test field-based predictions of the degree of landscape modification from the previous glaciation(s). The northern portion of the transect contains high concentrations of streamlined landforms associated with the onset zone of the Dubawnt Ice stream, inferred to be a region of high glacial modification. In contrast, the southern end of the transect contains lower concentrations of streamlined features, flow sets with contrasting orientations, and cross-cutting striations, suggesting a higher degree of landscape preservation during the last glaciation(s). Preliminary ¹⁰Be results broadly confirm our initial assessment of glacial modification along our transect, revealing slightly higher concentrations of ¹⁰Be in the south (less modification) and decreasing ¹⁰Be concentrations towards the north (more modification). Both bedrock and boulder samples follow this trend, however, our results show that in both low- and high-modification landsystems, some samples retain significant nuclide inheritance, including some boulders which suggests transport from a less modified landscape. Combining qualitative and quantitative approaches to evaluate glacial modification associated with specific landform assemblages informs our understanding of the basal thermal conditions of palaeo-ice sheets, the distribution of which informs our understanding of ice sheet evolution through space and time. Furthermore, the identification of streamlined features into palaeo-flow sets supports potential mineral exploration by helping to determine glacial transport directions and dispersal patterns. However, our results show the concentrations of cosmogenic nuclides vary within individual landsystems, suggesting that glacial modification varied through time and can be influenced by multiple factors (e.g., subglacial thermal conditions, topography, glacio-isostatic adjustment, lake development) that remain to be quantified.