| Titre | Evidence from geomorphological mapping and terrestrial cosmogenic nuclides for relict glacial terrains preserved under the Keewatin Ice Divide, Nunavut, Canada |
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| Auteur | McMartin, I ;
Campbell, J E; Godbout, P -M; Gosse, J C; Tremblay, T |
| Source | Geological Association of Canada, Program and Abstracts vol. 45, 2022 p. 155 |
| Liens | Online - En ligne
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| Image |  |
| Année | 2022 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20210663 |
| Éditeur | Association géologique du Canada |
| Réunion | GAC-MAC-IAH-CNC-CSPG Joint Meeting; Halifax; CA; mai 15-18, 2022 |
| Document | publication en série |
| Lang. | anglais |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Nunavut |
| SNRC | 55; 65; 56; 66 |
| Lat/Long OENS | -104.0000 -88.0000 68.0000 60.0000 |
| Sujets | elements glaciaires; morphologie de la glace; glace; techniques de cartographie; erosion glaciaire; Glacier de Keewatin ; géologie générale; Sciences et technologie |
| Programme | GEM-GéoNord : La géocartographie de l'énergie et des minéraux Coordination du programme GEM |
| Diffusé | 2022 05 15 |
| Résumé | (disponible en anglais seulement)
Relict glacial terrains were recently identified in large areas formerly covered by the northern portion of the Keewatin Ice Divide in the Kivalliq Region of
Nunavut west of Hudson Bay, Canada. A gradual transition in the preservation of these relict terrains, based on geomorphology, elevation, drainage network, lake density, weathering, and terrestrial cosmogenic nuclide (TCN) abundances in bedrock,
till, and boulder samples, is linked to differential glacial erosion. The unprecedented and comprehensive documentation of these preserved landscapes in central mainland Nunavut is based on the mapping of glacigenic features using high-resolution
imagery (ArcticDEM and Landsat 8), ground-based observations, and surface materials composition. Between Baker Lake and Repulse Bay, extensive areas of uplands form a continuum ranging from weathered bedrock, blockfields, and diamictons with little
to no evidence of glacial erosion to terrains with moderate glacial erosion, rare streamlined landforms, ice-marginal channels and discontinuous eskers. High proportions of secondary clay minerals and amorphous Fe-oxides in the clay fraction of the
most weathered diamictons are observed. In contrast, along and on either side of the ice divide zone between Baker Lake and the Manitoba border to the south, warm-based assemblages of glacial features, thick glacial deposits, and palimpsest glacial
landscapes reflect mobile outflow centres during the last glacial cycle(s). Our mapping and classification of these land systems is supported by relative TCN abundances. Paired 10Be and 26Al abundances are relatively high in relict terrains where
apparent 10Be ages of surface bedrock vary from 21.9 ± 0.5 ka to 61.9 ± 1.2 ka (n = 10; LSDn Age ± 1s int). These apparent ages reflect the persistence of cosmogenic nuclides formed during prolonged exposure prior to burial and preserved through
incomplete erosion under a variably cold-based ice divide and suggest that the uplands in the north have largely escaped the effects of the last glaciation(s). The presence of rare glacial erratics over the weathered bedrock suggests full glacial
coverage with sporadic warm-based conditions. South of Baker Lake, five apparent 10Be ages on bedrock varying between 6.9 ± 0.5 ka and 9.0 ± 0.6 ka indicate no exposure inheritance or burial. The exposure ages, however, generally suggest that
deglaciation occurred at least 1 kyr earlier than radiocarbon-based reconstructions. All these characteristics can help to evaluate the significance of inheritance for glacial erosion and to understand differences in the composition and provenance of
surface materials between the fully cold-based relict landscapes and the adjacent fully warm-based glacial terrains. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Ce résumé, qui sera présenté à la réunion annuelle de l'Association géologique du Canada, fait état de terrains anciens au Nunavut continental
préservés de l'érosion glaciaire au coeur de la calotte glaciaire Laurentidienne et datant d'une époque antérieure à la dernière glaciation (>75 000 ans). Les interprétations sont basées sur la cartographie détaillée des formes glaciaires à l'aide
d'images à haute résolution et de techniques de datation innovantes utilisées lors des activités GEM-2 Rae Synthesis of Glacial History and Dynamics et GEM-GeoNorth Hudson Glacial Records. Les travaux ont été entrepris pour fournir de nouvelles
connaissances géologiques sur la nature des terrains glaciaires et sont importants pour l'exploration minérale qui utilise la provenance des sédiments glaciaires afin d'évaluer comment la composition des matériaux de surface peut varier entre les
paysages reliques et les terrains plus jeunes affectés par la dernière glaciation. Les résultats appuieront les prises de décisions éclairées en matière d'exploration des ressources et de gestion de l'utilisation des terres. |
| GEOSCAN ID | 329634 |
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