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TitleGlacial erosional footprint of a migrating Laurentide Ice Sheet ice-divide in northeastern Quebec through 10Be and remote sensing analysis
AuthorRice, JORCID logo; Ross, M; Paulen, RORCID logo; Kelley, S; Briner, J
SourceGAC-MAC-IAH 2019: where geosciences converge/AGC-AMC-AIH 2019 : où les géosciences convergent; GAC-MAC-IAH Joint Meeting, Abstract volume vol. 42, 2019 p. 164-165 Open Access logo Open Access
LinksOnline - En ligne (complete volume, volume complet, PDF, 6.08 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20180444
PublisherGeological Association of Canada
MeetingGAC-MAC-IAH 2019 / AGC-AMC-AIH 2019; Québec, QC; CA; May 12-15, 2019
Mediaon-line; digital
File formatpdf (Adobe® Reader®)
NTS23P/13; 23P/14; 23P/15; 23P/16
Lat/Long WENS -66.0000 -64.0000 56.0000 55.5000
Subjectssurficial geology/geomorphology; geochemistry; geophysics; Nature and Environment; Science and Technology; glacial erosion; beryllium geochemistry; remote sensing; satellite imagery; glacial history; glaciation; ice flow; models; glacial landforms; surface waters; lakes; thermal analyses; Laurentide Ice Sheet; Quebec-Labrador Ice Dome; Ungava Ice Stream; ice divides; ice streams; ice-flow directions; Phanerozoic; Cenozoic; Quaternary
ProgramGEM2: Geo-mapping for Energy and Minerals Hudson/Ungava, Northeastern Quebec-Labrador, surficial geology
Released2019 05 01
AbstractComplex ice-flow records are documented for major ice-divide regions of the Laurentide Ice Sheet, including areas where previous empirical work and numerical models predicted a low probability of warm-based subglacial conditions and concomitant low-erosion during the last glaciation. This suggests there are important unanswered questions regarding the long-term glacial dynamics and subglacial thermal regime surrounding these ice-divide regions. In this study, we analyze the subglacial erosional record across an ice-divide region (~ 7000 km2) associated with migration of the Quebec-Labrador Ice Dome in central-northeastern Quebec using spatial analysis and field-based methods to gain insights into subglacial erosional patterns and erosional vigour. Subglacial erosional proxies (e.g. glacially streamlined landform abundance and elongation, and lake density) were mapped and spatially quantified to create an erosional index. In addition, cosmogenic 10Be abundances were measured in bedrock and till samples to estimate the degree of inheritance across the study area. From our analysis, six distinct zones of relative subglacial erosion were identified, with a large low-erosion region in the central-upland transitioning to higher-erosional zones near the northern corners of the study area. We interpret these results as indicative of polythermal conditions that shifted spatially under the influence of a migrating ice divide, which itself occurred in response to differential drawdown and changes in the Ungava Ice Stream dynamics and configuration. The net effect of these shifting conditions is a fragmented landscape comprised of distinctive pieces resulting from differential erosion relating to the local ice flow history. This work also brings new evidence of subglacial erosion within just a few kilometres from the inferred coeval position of the ice divide. Our results thus provide evidence for warm-based subglacial conditions underneath a saddle of the Quebec-Labrador Dome for at least part of the last glaciation that has yet to be captured by ice-sheet numerical models.
Summary(Plain Language Summary, not published)
This presentation is a contribution to the GEM-2 funded PhD thesis undertaken by Jessey Rice (University of Waterloo). It examines the net effect of erosion of the landscale, as a proxy to glacial erosional vigour.

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