Till stratigraphy and sedimentology at the margins of terrestrially terminating ice streams: case study of the western Canadian prairies and high plains

Evans, David J. A.; Hiemstra, John F.; Boston, Clare M.; Leighton, Iain; Cofaigh, Colm Ó; Rea, Brice R.

doi:10.1016/j.quascirev.2012.04.028

Cited by 44 publications

(61 citation statements)

References 73 publications

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“…This should help differentiate surge-type behaviour from ice streaming, but we note that some modern ice streams have been suggested to stagnate and reactivate (Bougamont et al, 2003;Hulbe and Fahnestock, 2007). This has also been suggested in the palaeo-record ) and some have even used the term 'surging ice streams' (Evans et al, , 2012. In summary, we adhere to the simple definition of an ice stream as an abrupt spatial transition in flow, but place no constraints on the duration of flow.…”

Section: Historical Perspective On Ice Streams In the Lismentioning

confidence: 89%

“…This definition encompasses spatial transitions where an ice stream bordered by slower moving ice may then feed into an outlet glacier sensu stricto, which is bordered by rock-walls. However, it ignores the temporal aspect of the rapid ice flow, which has caused some confusion and conflation of ideas in the literature, especially in relation to land-terminating (terrestrial) ice streams, where the term is often used interchangeably with surging Patterson, 1997;Jennings, 2006;Evans et al, 2012). Generally, ice streaming is used to describe a sustained period of fast flow (decades to millennia), whereas surge-type glaciers exhibit a cycle of fast flow (typically years), followed by a quiescent phase that is of much longer duration (typically decades; Raymond, 1987).…”

Section: Historical Perspective On Ice Streams In the Lismentioning

confidence: 99%

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Ice streams in the Laurentide Ice Sheet: Identification, characteristics and comparison to modern ice sheets

Margold

Stokes

Clark

2015

Earth-Science Reviews

219

222

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This paper presents a comprehensive review and synthesis of ice streams in the Laurentide Ice Sheet (LIS) based on a new mapping inventory that includes previously hypothesised ice streams and includes a concerted effort to search for others from across the entire ice sheet bed. The inventory includes 117 ice streams, which have been identified based on a variety of evidence including their bedform imprint, large-scale geomorphology/ topography, till properties, and ice rafted debris in ocean sediment records. Despite uncertainty in identifying ice streams in hard bedrock areas, it is unlikely that any major ice streams have been missed. During the Last Glacial Maximum, Laurentide ice streams formed a drainage pattern that bears close resemblance to the present day velocity patterns in modern ice sheets. Large ice streams had extensive onset zones and were fed by multiple tributaries and, where ice drained through regions of high relief, the spacing of ice streams shows a degree of spatial self-organisation which has hitherto not been recognised. Topography exerted a primary control on the location of ice streams, but there were large areas along the western and southern margin of the ice sheet where the bed was composed of weaker sedimentary bedrock, and where networks of ice streams switched direction repeatedly and probably over short time scales. As the ice sheet retreated onto its low relief interior, several ice streams show no correspondence with topography or underlying geology, perhaps facilitated by localised build-up of pressurised subglacial meltwater. They differed from most other ice stream tracks in having much lower length-to-width ratios and have no modern analogues. There have been very few attempts to date the initiation and cessation of ice streams, but it is clear that ice streams switched on and off during deglaciation, rather than maintaining the same trajectory as the ice margin retreated. We provide a first order estimate of changes in ice stream activity during deglaciation and show that around 30% of the margin was drained by ice streams at the LGM (similar to that for present day Antarctic ice sheets), but this decreases to 15% and 12% at 12 cal ka BP and 10 cal ka BP, respectively. The extent to which these changes in the ice stream drainage network represent a simple and predictable readjustment to a changing mass balance driven by climate, or internal ice dynamical feedbacks unrelated to climate (or both) is largely unknown and represents a key area for future work to address.

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Section: Historical Perspective On Ice Streams In the Lismentioning

confidence: 89%

Section: Historical Perspective On Ice Streams In the Lismentioning

confidence: 99%

Ice streams in the Laurentide Ice Sheet: Identification, characteristics and comparison to modern ice sheets

Margold

Stokes

Clark

2015

Earth-Science Reviews

219

222

View full text Add to dashboard Cite

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“…The relative paucity of glacifluvial deposits and sparsity of obvious straight-limbed esker ridges within the CSR corridor indicates that glacifluvial infilling, akin to either the zig-zag esker development in heavily crevassed surging glaciers Rea, 1999, 2003) or the pressurized ice tunnels and hydrofracture fill eskers of subpolar glaciers (Evans et al, 2012), was subordinate to subglacial till squeezing in terms of landform generation. However, preservation potential might be significant here.…”

Section: Interpretation Of the Saskatchewan Csr Corridormentioning

confidence: 99%

Crevasse-squeeze ridge corridors: Diagnostic features of late-stage palaeo-ice stream activity

2016

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“…Proglacial lakes and ice instability are well documented in other regions, where changes in porewater pressure and increased calving are thought to relate to surges or ice streaming (e.g. Sharpe and Cowan, 1990;Stokes and Clark, 2004;Evans et al, 2012). Additionally, proglacial lakes can enhance melting leading to further glacier mass loss and increasing the flux of meltwater (Carrivick and Tweed, 2013).…”

Section: Stage 2 -Flow Towards the Mountains And Deglaciationmentioning

confidence: 99%

“…During deglaciation, proglacial lakes formed along with the progressive latitudinal desuturing of ice sheet margins along the Rocky Mountain Front (St-Onge, 1972;Mathews, 1980;Dyke, 2004;Fenton et al, 2013). These proglacial lakes temporarily stored and released water, and potentially affected glaciodynamics by triggering rapid ice flow due to bed lubrication and increased calving and drawdown (Evans, 2000;Stokes and Clark, 2004;Evans et al, 2012;Carrivick and Tweed, 2013).…”

Section: Introductionmentioning

confidence: 99%

Reconstructing the confluence zone between Laurentide and Cordilleran ice sheets along the Rocky Mountain Foothills, south‐west Alberta

Utting

Atkinson

Pawley

et al. 2016

J Quaternary Science

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Landform mapping near the Athabasca valley was fundamental to determining whether or not the Late Wisconsinan Laurentide and Cordilleran Ice Sheets coalesced. In this paper we examine the detailed landform record using new LiDAR digital elevation and hillshade models of the area of confluence and eventual desuturing of these ice sheets. This work reveals an earlier more extensive Cordilleran advance prior to coalescence with the LIS. When the ice sheets coalesced, the flow pattern is dominated by ice flow along the mountain front, with Cordilleran ice flowing out of major trunk valleys but Laurentide ice flowing into the Foothills up smaller valleys. This flow pattern implies that when the ice sheets coalesced the CIS was already waning, or at least was not at its maximum. Deglaciation was interrupted by several re-advances, likely related to the destabilizing effect of proglacial lakes along the ice margin.

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Till stratigraphy and sedimentology at the margins of terrestrially terminating ice streams: case study of the western Canadian prairies and high plains

Cited by 44 publications

References 73 publications

Ice streams in the Laurentide Ice Sheet: Identification, characteristics and comparison to modern ice sheets

Ice streams in the Laurentide Ice Sheet: Identification, characteristics and comparison to modern ice sheets

Crevasse-squeeze ridge corridors: Diagnostic features of late-stage palaeo-ice stream activity

Reconstructing the confluence zone between Laurentide and Cordilleran ice sheets along the Rocky Mountain Foothills, south‐west Alberta

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