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TitleGlacial dispersal from a migrating Laurentide Ice Sheet ice divide in northeastern Quebec
AuthorRice, JORCID logo; Campbell, H; Ross, MORCID logo; Paulen, RORCID logo; McClenaghan, BORCID logo
SourceGAC®-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; Geological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 44, 2021 p. 266 Open Access logo Open Access
LinksOnline - En ligne (complete volume - volume complet, PDF, 2.45 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20200640
PublisherGeological Association of Canada
MeetingGAC-MAC 2021: Geological Association of Canada-Mineralogical Association of Canada Joint Annual Meeting 2021; London, ON; CA; November 1-5, 2021
Mediadigital; on-line
File formatpdf
NTS23P/13; 23P/14; 23P/15; 23P/16
Lat/Long WENS -66.0000 -64.0000 56.0000 55.5000
Subjectssurficial geology/geomorphology; geochemistry; mineralogy; economic geology; Science and Technology; Nature and Environment; glacial history; glaciation; ice flow; glacial erosion; sediment transport; sediment dispersal; models; glaciology; glacial deposits; tills; clasts; pebble lithology; bedrock geology; lithology; orthopyroxene; depositional history; mineral exploration; exploration methods; Laurentide Ice Sheet; Labrador Trough; Ancestral Labrador Ice Divide; De Pas Batholith; Cabot Lake Ice Stream; Ungava Bay Ice Stream; ice divides; ice-flow directions; ice streams; Phanerozoic; Cenozoic; Quaternary; Precambrian
ProgramGEM2: Geo-mapping for Energy and Minerals Hudson/Ungava, Northeastern Quebec-Labrador, surficial geology
Released2021 11 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 indicate a low probability of warm-based subglacial conditions and concomitant low-erosion rates during the last glaciation. Growing evidence of widespread, shifting subglacial warm-based erosion demonstrates that these inner-ice sheet regions had dynamic polythermal subglacial conditions. However, the effect of a polythermal regime under migrating ice divides on subglacial sediment production and dispersal is poorly documented. Here we reconstruct the evolution of glacial sediment dispersal across a large area (~ 20 000 km²) in northeastern Quebec where the ice flow history, including an ice-divide migration, is well constrained. Dispersal patterns are assessed using geochemistry, indicator mineral, clast lithology data, and principal component analysis of till matrix geochemistry. Our results first improve the characterization of the Labrador Trough iron formation clast dispersal, which now extends to the northeast up to 120 km from its source. This relatively long northeast dispersal pattern, which is correlated to the oldest ice-flow phase characterized by wide-spread, warm-based subglacial conditions, formed prior to the development of the regional Ancestral Labrador ice divide. Results also show that this regional pattern is overprinted by several shorter but more complex dispersal patterns (e.g. amoeboid shapes), such as the dispersal of orthopyroxene grains from the western half of the De Pas Batholith in the centre of the study area in multiple directions. These modified dispersal patterns are greatest in the directions of the Cabot Lake and Ungava Bay ice streams which influenced ice flow within the study area. This suggests that the ice flow phases that followed the regional northeast ice flow phase strongly modified and/or overprinted pre-existing patterns due to ice divide formation and migration, as well as due to the development of late glacial ice streams. This work brings new evidence for warm-based subglacial erosion, transport, and deposition in relatively close proximity to a contemporaneous ice divide, a situation that has yet to be captured by ice sheet models. These findings also provide important insights for future mineral exploration programs within inner ice sheet regions.
Summary(Plain Language Summary, not published)
This work focuses on glacial sediment dispersal patterns by looking at the abundances of different rocks, minerals, and elements from samples collected in northeastern Quebec. This region is of particular importance as it was within the innermost regions of the Laurentide Ice Sheet during the last ice age. These results will provide important information on how these large ice sheets behaved at their cores and will provide useful information for ice-sheet models and for mineral exploration within these regions.

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