| Titre | LiDAR-based semi-automated mapping of drumlins and mega-scale glacial lineations of the Green Bay Lobe, Wisconsin, USA: ice sheet beds as glaciotribological systems |
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| Auteur | Eyles, N; Bukhari, S; Sookhan, S; Ruscica, P; Paulen, R C |
| Source | Earth Surface Processes and Landforms 2022 p. 1-65, https://doi.org/10.1002/esp.5486  Accès ouvert |
| Image |  |
| Année | 2022 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20210662 |
| Éditeur | John Wiley & Sons on behalf of the British Society for Geomorphology |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1002/esp.5486 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Région | Wisconsin |
| Lat/Long OENS | -92.5308 -79.1628 49.6225 39.2806 |
| Sujets | l'apprentissage machine; Sciences et technologie; Nature et environnement |
| Illustrations | cartes de localisation; diagrammes; représentations graphiques combinées |
| Programme | GEM-GéoNord : La géocartographie de l'énergie et des minéraux Coordination du programme GEM |
| Diffusé | 2022 09 15 |
| Résumé | (disponible en anglais seulement)
A machine learning methodology for processing and visualizing high resolution LiDAR digital data is used to map drumlins and mega-scale glacial lineations
(MSGLs) on the bed of the Late Wisconsin Green Bay Lobe in Wisconsin, USA which exhibited surge-like behaviour during deglaciation. Previous work has shown that streamlined bedforms are the product of erosional streamlining of pre-existing sediment.
Analysis of bedform height and elongation ratio using Curvature-based Relief Separation (CBRS) and K-means clustering of 32,003 bedforms reveals a continuum of six morphotypes ranging from drumlins, through 'channeled' more elongated multi-crested
drumlins, to MSGLs. Further statistical analysis shows morphotypes cluster into six types of streamlined surfaces (S1-S6) recording progressive elimination of an antecedent overridden topography to produce a smoother bed. Initial, relatively high
relief drumlinized surfaces (S1, S2) occur around the slower flowing lateral flanks of the lobe where a pre-existing hummocky morainal topography was only partially modified by subglacial erosion. More streamlined surfaces (S3, S4) dominated by
multi-crested more elongate drumlins of reduced relief amplitude, are transitional to flow sets of MSGL-dominated surfaces (S5, S6) indicative of much faster flowing ice streaming along the lobe's axis. Estimates of basal drag based on roughness
calculations for each surface type, identify a 61% reduction in frictional retardation from poorly-streamlined surfaces S1 and S2 to MSGL-dominated surfaces S5 and S6 with a step-like reduction between drumlins and channeled drumlins (S3, S4)
possibly recording the rapid onset of fast flow. Subglacial streamlining is argued to be accomplished by a thin (< 1 m) 'third layer' of deforming subglacial debris between ice and its bed which functioned as an erodent layer. A thin (< 3 m) till
cap, formed by aggradation of deforming debris, rests unconformably on heterogenous core sediments. Streamlined subglacial surfaces are comparable to the 'functional' surfaces resulting from erosion by a 'third layer' of wear debris in engineering
tribological systems, and also, by gouge on faults. Pleistocene ice sheets expanded over pre-existing landsystems pointing to the broader relevance of the methodology and findings reported here. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Le traitement et la visualisation de données topographiques numériques LiDAR haute résolution à l'aide d'une méthodologie d'apprentissage
automatique nouvellement développée sont utilisés pour cartographier les drumlins et les linéations glaciaires à grande échelle. Cela enregistre l'érosion progressive des sédiments proglaciaires préexistants alors que la calotte glaciaire sculpte son
lit pour réduire la traînée de friction au fil du temps, transformant les drumlins en linéations glaciaires à grande échelle. |
| GEOSCAN ID | 329631 |
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