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TitleA quasi-annual record of time-transgressive esker formation
AuthorLivingstone, S J; Lewington, E L M; Clark, C D; Storrar, R D; Sole, A J; McMartin, IORCID logo; Ng, F
SourceAbstract book, PALEOARC 2021, 2nd International Conference on 'Processes and Palaeo-environmental changes in the Arctic: from past to present'; by Società Geologica Italiana; 2021 p. 57, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20200772
PublisherSocietà Geologica Italiana (Rome, Italy)
MeetingPALEOARC 2021, 2nd International Conference on 'Processes and Palaeo-environmental changes in the Arctic: from past to present'; Pisa; IT; May 24-28, 2021
Mediaon-line; digital
File formatpdf
NTS55E; 55F; 55J; 55K; 55L; 55M; 55N; 55O; 55P; 56A; 56B; 56C; 56G; 65I
AreaChesterfield Inlet; Hudson Bay
Lat/Long WENS -97.0000 -88.0000 65.5000 61.2500
Subjectssurficial geology/geomorphology; sedimentology; Nature and Environment; Science and Technology; depositional environment; glacial history; deglaciation; ice margins; ice retreat; paleodrainage; sediment dispersal; glacial landforms; eskers; moraines; moraine, de geer; Laurentide Ice Sheet; moraine ridges; glaciofluvial sediments; Phanerozoic; Cenozoic; Quaternary
ProgramGEM2: Geo-mapping for Energy and Minerals Rae Province, Synthesis of glacial history
Released2021 05 21
AbstractEskers are traditionally identified as slightly sinuous ridges of glaciofluvial sand and gravel deposited in subglacial, englacial or supraglacial drainage channels, and are common in formerly glaciated regions (Storrar et al., 2014). But despite being widely used to infer properties of the subglacial channelised drainage system and to reconstruct and constrain ice-retreat histories, it is not known whether eskers form synchronously in long conduits (Brennand, 1994) or if they represent a time-transgressive deglacial signature of deposition along drainage pathways (De Geer et al., 1910; Mäkinen, 2003). Here we present new geomorphological mapping of beaded eskers (series of aligned sediment mounds) in Keewatin, Canada. Esker beads frequently show a close 1:1 association with De Geer moraine (i.e., each bead is associated with a corresponding ridge) and are therefore interpreted to be quasi-annual ice-marginal deposits formed time-transgressively at the mouth of subglacial conduits during deglaciation (Livingstone et al., 2020). Under our time-transgressive interpretation, esker bead spacing constrains the typical pace of deglaciation in central Nunavut, and provides a minimum bound on annual sediment fluxes. We suggest that the prevalence of esker beads across this predominantly marine-terminating sector of the Laurentide Ice Sheet is a result of sediment fluxes that were unable to backfill conduits at a rate faster than ice-margin retreat. Conversely, we hypothesise that esker ridges form when sediment backfilling of the subglacial conduit outpaced retreat, resulting in headward esker growth close to but behind the margin. The implication, in accordance with recent modelling results (e.g., Hewitt & Creyts, 2019), is that eskers in general record a composite signature of ice marginal drainage.
Summary(Plain Language Summary, not published)
The distribution and network geometry of eskers are used to reconstruct past ice sheet retreat patterns. However uncertainty remains about their timing and duration, i.e. whether they reflect an extensive synchronous drainage system under ice sheets, or record the ice margin chronology as it retreated. To answer this question, university and government researchers from UK and Canada have mapped nearly 10,000 esker segments and associated morainic ridges from high-resolution ArcticDEM across a large area of central Nunavut, NW of Hudson Bay. The oral presentation will summarize a recent paper on the results of this work at an online conference. PaleoArc is an international network research program aiming to further understand past and present environmental changes and processes in the Arctic.

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