| Titre | Reconstructing the Quebec-Labrador sector of the Laurentide Ice Sheet from new surficial geology maps, till provenance, and detrital 10Be data |
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| Auteur | Rice, J M ; Ross,
M A; Paulen, R C |
| Source | Program and abstracts, 47th Annual International Arctic Workshop; 2017 p. 126-127  Accès ouvert |
| Liens | Online - En ligne (Complete volume, Volume complet, PDF, 10.3 MB)
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| Image |  |
| Année | 2017 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20170006 |
| Éditeur | ARCUS (Arctic Research Consortium of the United States |
| Réunion | 47th International Arctic Workshop; Buffalo, NY; US; mars 23-25, 2017 |
| Document | livre |
| Lang. | anglais |
| Media | en ligne; numérique |
| Formats | pdf |
| Programme | GEM2 : La géocartographie de l'énergie et des minéraux Nord-est du Québec-Labrador, géologie des dépôts meubles de la région
d'Hudson/Ungava |
| Diffusé | 2017 03 01 |
| Résumé | (disponible en anglais seulement)
Throughout the last glaciation, northeastern North America was covered by the Quebec-Labrador sector of the Laurentide Ice Sheet (LIS); a dynamic ice-dispersal
center which persisted until the final stages of the LIS, when it became one of the last remnants of continental ice to disappear around 6.5 ka (Occhietti et al., 2011). Therefore, the Quebec-Labrador sector had an important influence on the late
Pleistocene climate, specifically through its rapid release of ice and ice-dammed proglacial lakes into Ungava Bay and the North Atlantic. However, detail regarding the inception, migration, and disappearance of this ice center and its importance in
glacial lake drainage is poorly understood. Understanding of the resultant glacial landscape within the George Plateau of the Canadian Shield is further complicated by the lack of Quaternary stratigraphy and preserved organic material suitable for
radiocarbon dating, which could be used to constrain ice marginal retreat. A comprehensive understanding of the evolution of the Quebec-Labrador ice center could provide an important historical analogue when forecasting future long-term changes to
current large scale continental ice sheets. Specifically, what role did the Quebec-Labrador ice sheet play in iceberg discharge through Ungava Bay into the Hudson Strait, and what is the record of proglacial lake drainage into the North Atlantic
during deglaciation.
To fully understand the evolution of the Quebec-Labrador ice sector, regional surficial mapping at the previously interpreted geographical location of the ice center was undertaken. Till samples collected from this region were
analyzed for clast provenance, indicator mineral content, and geochemical abundances to obtain insights into glacial sediment dispersal patterns, resulting from changing ice flow and basal thermal regimes. Ice flow azimuths and relative chronology
were established through large scale (oriented landforms) and outcrop scale ice flow indicator measurements. To constrain the deglacial phase of the ice sheet, four samples were collected for optically stimulated luminescence (OSL) dating of
proglacial lacustrine beaches and twelve samples collected for 10Be surface exposure dating from glacially eroded bedrock and erratics. An additional ten till samples were collected for 10Be inventory to test the erosional vigor associated with
subglacial conditions that should exist under our hypothesized subglacial conditions, following methodology established by Staiger et al. (2006) and Ross et al. (2015). The calculated 10Be abundances will be used as a quantitative test to assess the
subglacial regime within, as previous studies have indicated correlations between regions of little glacial erosion with higher abundances of 10Be, reflecting high preglacial inheritance, and regions of high glacial erosion with low abundances of
10Be (Ross et al., 2015). Our work has established a minimum of four glacial ice flows: 1) northeast across the entire study area, with ice-flow originating in the Quebec highlands (Veillette et al.1999), 2) a radial flow from the buildup of the
Quebec-Labrador sector of the LIS, 3) radial flow following a dynamic westward adjustment of the dispersal center including the ice stream corridors established during deglaciation, and 4) deglacial flow with local topographic controls. Preliminary
10Be abundance results from till samples suggest a change from more sluggish colder based ice in the east to warmer, more highly erosive ice in the west. These results provide insights into the subglacial conditions related to the landscape
evolution, as well as generate empirical based data that could be used to constrain glacial/climate models (cf. Stokes et al., 2015). With empirical based data to better confine such models, an improved conceptual understanding of how this large ice
mass behaved during deglaciation, its effects on proglacial lake draining, and how it fed ice calving margins can be more accurately understood. From this framework, an increased understanding of how large ice evolve, migrate, and demise will be
developed. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Une affiche présente des résultats préliminaires de la thèse de doctorat financée par GEM2 de Jessey Rice, dans le cadre de l'activité de
cartographie de surface de la zone noyau. Cette affiche met en évidence trois saisons de travail sur le terrain et présente certaines des données préliminaires issues des échantillons de surface. L'intention est de présenter cette recherche financée
par GEM2 à des pairs qui mènent des recherches dans l'Arctique. |
| GEOSCAN ID | 300261 |
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