| Titre | Discriminating substrate geology and ice flow velocity controls on subglacial streamlined landforms and surfaces under a paleo ice stream in central Canada |
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| Auteur | Akçar, N ; Eyles,
N; Bukhari, S; Paulen, R C; Sookhan, S |
| Source | XXI INQUA Congress - Program with Abstracts; par INQUA; 2023 p. 1 |
| Image |  |
| Année | 2023 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20220416 |
| Éditeur | INQUA |
| Réunion | XXI INQUA Congress; Rome; IT; juillet 14-20, 2023 |
| Document | livre |
| Lang. | anglais |
| Media | papier; numérique; en ligne |
| Formats | pdf |
| Province | Ontario |
| Région | le sud de l'Ontario; Le Canada central |
| Sujets | écoulement glaciaire; Sciences et technologie; géologie générale |
| Programme | GEM-GéoNord : La géocartographie de l'énergie et des minéraux Coordination du programme GEM |
| Diffusé | 2023 07 14 |
| Résumé | (disponible en anglais seulement)
The Peterborough Drumlin Field (PDF: 5000 km2) in Southern Ontario, Central Canada contains some 3000 streamlined bedforms. LiDAR mapping and statistical
analyses show continuums between drumlins, grooved drumlins, and megascale glacial lineations, that previous work showed to be erosional in origin, cut below a soft-bedded terrestrial paleo ice stream flowing off the Algonquin Highlands south to the
interlobate Oak Ridges Moraine during the final stages of the last glaciation c. 12000 years before present. Using the curvature-based relief separation method for mapping the morphology of these bedforms we identified eight morphotypes and in
addition, six types of streamlined surfaces characterized by specific assemblages of morphotypes recording a progressive reduction of bed relief and roughness by subglacial erosion. Initial statistical analysis shows that more elongated morphotypes
and streamlined surfaces are grouped into distinct flow sets suggesting the primary importance of variation in flow velocity across the ice stream in shaping and smoothing the bed. This study tests this hypothesis by exploring the specific role of
substrate geology in bedform evolution established by observations and facies analysis of sediments exposed in numerous road cuts and quarries. This exercise confirms previous suggestions that bedform geology is unchanging and consists largely of an
older till (Northern Till) deposited during the Last Glacial Maximum of the Laurentide Ice Sheet which was subsequently eroded by faster flowing streaming ice during deglaciation leaving a thin upper till cap. Confirmation of the primacy of ice flow
velocity in controlling morphotypes and surfaces now allows glaciodynamic modeling and recognition of specific ice flow velocities from streamlined morphotypes and surfaces on ancient ice stream beds. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Ceci utilise des données LiDAR sur un grand champ de drumlins glaciaires pour discerner la rugosité de la surface, en tant que produit de
l'érosion glaciaire tardive et du lissage glaciaire du lit mou, qui à leur tour, fournissent une boucle de rétroaction pour le contrôle de la vitesse de la glace. |
| GEOSCAN ID | 331167 |
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