| Title | A quasi-annual record of time-transgressive esker formation: implications for ice-sheet reconstruction and subglacial hydrology |
| Associated Data | https://doi.org/10.15131/shef.data.12315221 |
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| Author | Livingstone, S J ;
Lewington, E L M; Clark, C D; Storrar, R D; Sole, A J; McMartin, I; Dewald, N; Ng, F |
| Source | The Cryosphere vol. 14, issue 6, 2020 p. 1989-2004, https://doi.org/10.5194/tc-14-1989-2020  Open Access |
| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20200288 |
| Publisher | Copernicus |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf; html |
| Province | Nunavut |
| NTS | 55E; 55F; 55J; 55K; 55L; 55M; 55N; 55O; 55P; 56A; 56B; 56C; 56G; 65I |
| Area | Chesterfield Inlet; Hudson Bay |
| Lat/Long WENS | -97.0000 -88.0000 65.5000 61.2500 |
| Subjects | surficial geology/geomorphology; sedimentology; Nature and Environment; Science and Technology; depositional environment; ice sheets; glacial history; deglaciation; ice margins; ice retreat;
paleodrainage; sediment dispersal; glacial landforms; eskers; moraines; moraine, de geer; modelling; models; topography; drainage systems; Laurentide Ice Sheet; Keewatin Ice Divide; ArcticDEM; moraine ridges; glaciofluvial sediments; Digital
elevation data; esker ridges; Phanerozoic; Cenozoic; Quaternary |
| Illustrations | location maps; geoscientific sketch maps; histograms; plots; digital elevation models; schematic representations; satellite images; profiles |
| Program | GEM2: Geo-mapping for Energy and Minerals Rae Province, Synthesis of glacial history |
| Released | 2020 06 18 |
| Abstract | We identify and map chains of esker beads (series of aligned mounds) up to 15 m high and on average ~65 m wide in central Nunavut, Canada, from the high-resolution (2 m) ArcticDEM. Based on the close
1:1 association with regularly spaced, sharp-crested ridges interpreted as De Geer moraines, we interpret the esker beads to be quasi-annual ice-marginal deposits formed time-transgressively at the mouth of subglacial conduits during deglaciation.
Esker beads therefore preserve a high-resolution record of ice-margin retreat and subglacial hydrology. The well-organised beaded esker network implies that subglacial channelised drainage was relatively fixed in space and through time. Downstream
esker bead spacing constrains the typical pace of deglaciation in central Nunavut between 8.1 and 6.8 cal kyr BP to 165-370 m/yr, although with short periods of more rapid retreat (> 400 m/yr). Under our time-transgressive interpretation, the lateral
spacing of the observed eskers provides a true measure of subglacial conduit spacing for testing mathematical models of subglacial hydrology. Esker beads also record the volume of sediment deposited from conduits in each melt season, thus providing a
minimum bound on annual sediment fluxes, which is in the range of 103-104 m3/yr in each 6-10 km wide subglacial conduit catchment. 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, is that eskers in general record a composite signature of ice-marginal drainage rather than a temporal snapshot of ice-sheet-wide
subglacial 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 the high-resolution ArcticDEM across a large area of central Nunavut, NW of Hudson Bay. This externally funded project benefited from the contribution of the Geological Survey of Canada
co-author who provided and synthesized field information and expert knowledge collected as part of the GEM2 Rae Glacial Synthesis project. |
| GEOSCAN ID | 326889 |
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