| Titre | Searching for Ontario's 'missing' ice streams |
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| Auteur | Mulligan, R ;
Marich, A; Paulen, R |
| Source | GAC®-MAC 2021, London, Canada: Exploring Geosciences Through Time and Space/GAC®-MAC 2021, London, Canada : Explorer les géosciences à travers le temps et l'espace; L'Association géologique du
Canada-L'Association minéralogique du Canada, Réunion annuelle conjointe, Recueil des résumés vol. 44, 2021 p. 230  Accès ouvert |
| Liens | Online - En ligne (complete
volume - volume complet, PDF, 2.45 MB)
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| Image |  |
| Année | 2021 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20210299 |
| Éditeur | Association géologique du Canada |
| Réunion | Geological Association of Canada-Mineralogical Association of Canada Joint Annual Meeting 2021; London, ON; CA; Novembre 1-5, 2021 |
| Document | publication en série |
| Lang. | anglais |
| Media | numérique; en ligne |
| Formats | pdf |
| Province | Ontario |
| SNRC | 31B; 31C; 31D; 31E; 31F; 31G; 31K; 31L; 31M; 32D; 32E; 32L; 32M; 40; 41; 42; 43; 44D; 52; 53A; 53B; 53C; 53D; 53F; 53G; 53H; 53I; 53J; 53K; 53O; 53P; 54A; 54B |
| Lat/Long OENS | -95.2500 -74.0000 57.0000 41.5000 |
| Sujets | antecedents glaciaires; glaciation; écoulement glaciaire; déglaciation; erosion glaciaire; transport des sediments; dispersion des sédiments; antecedents de sedimentation; marges glaciaires; dépôts
glaciaires; topographie glaciaire; elements glaciaires; tills; moraines; linéations; affouillements glaciaires; lacs proglaciaires; établissement de modèles; effets climatiques; topographie; configurations lit; Calotte glaciaire Laurentide; Bouclier
Canadien; courants glaciaires; directions d'écoulement glaciaire; Données numériques d'élévation; géologie des dépôts meubles/géomorphologie; Nature et environnement; Sciences et technologie; Phanérozoïque; Cénozoïque; Quaternaire |
| Programme | GEM-GéoNord : La géocartographie de l'énergie et des minéraux Coordination du programme GEM |
| Diffusé | 2021 11 01 |
| Résumé | (disponible en anglais seulement)
The advance and retreat of the Laurentide Ice Sheet (LIS) across Ontario extensively modified the landscape through erosion of bedrock and pre-existing
sediment, and deposition of thick sediment sequences along the margins of ice lobes during deglaciation. The recent release of high-resolution (<2 m) LiDAR and other digital terrain data for large areas of Ontario enables improved mapping of glacial
landforms at regional scales. Increasingly, over the last decade, the existence - and influence - of paleo-ice streams on the landscape has been recognized. Mega-scale glacial lineations (MSGL), a landform assemblage diagnostic of paleo-ice streams,
can be difficult to identify from the ground, but are readily visible on these high resolution digital elevation model datasets and hold significant implications for paleoglaciological reconstructions. Developing an understanding of the onset,
evolution, timing, and interactions between paleo-ice streams and their beds is critical to understanding ice sheet evolution and provides important constraint to models of ice sheet response to climate changes. As glacial morphotypes, MSGL in
Ontario occur in clusters, in areas mapped as coarse-grained till in Canadian Shield terrain, as isolated till mounds surrounded by streamlined bedrock, and in larger swarms in thicker (>40 m) unconsolidated sediment zones. Commonly, larger clusters
of MSGL occur within or along the margins of large topographic lowlands, and in many cases, MSGL long-axes are parallel to the lows, or diverge from or converge towards the central portions of low-lying terrain. The downflow extents of numerous
clusters are commonly marked by large moraine complexes, representing clear flow sets. Within each flowset, a wide variety of sediment-cored, mixed, and bedrock-cored bedforms exist. Low-relief (<6 m high) MSGL are also observed across regional
bedrock highs separating lowland flowsets. Small (<3 m high) recessional moraines overlie the MSGL across portions of the exposed beds. Large areas of iceberg scouring are observed downflow of the MSGL clusters in areas inundated by proglacial lakes
during deglaciation. The abundance of MSGL suggest a larger proportion of the LIS margin developed ice streams than previously recognized, particularly in hard-bedded Canadian Shield areas. MSGL distribution and relationships with local to regional
topography and antecedent bedforms suggest several ice streams were initiated within topographic lows as the ice sheet thinned during deglaciation. Ice stream propagation was likely enhanced in many areas due to the existence of deep proglacial lakes
fronting the ice margin. Future work involves field-mapping the surficial geology of several parts of the exposed beds of these inferred paleo-ice streams to refine understanding of sediment-landform assemblages and collect samples to improve
knowledge on the timing of ice stream activity in the region. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Ce travail est un processus continu de réexamen de divers paysages glaciaires du Bouclier canadien, à l'aide de données LiDAR accessibles au
public, afin d'augmenter notre connaissance de la dernière glaciation de l'Amérique du Nord. Ces nouvelles données d'altitude numériques à plus haute résolution révèlent des informations supplémentaires qui ne sont pas historiquement documentées ou
observées à partir de photographies aériennes plus anciennes. |
| GEOSCAN ID | 329193 |
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