Erratum: Laurentide subglacial outburst floods: landform evidence from digital elevation models

Shaw, John; Rains, Bruce; Eyton, Ronald; Weissling, Lee

doi:10.1139/e17-060

Cited by 13 publications

(19 citation statements)

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“…12; Shetsen, 1987Shetsen, , 1990Rains et al, 1993;Shaw et al, 1996;Munro and Shaw, 1997;Munro-Stasiuk and Sjogren, 2006;Evans et al, 2008). Surficial sediment thickness in hummocky terrain is about 10-15 m, much thicker than in flow paths where bedrock is exposed over much of their extent (Shetsen, 1987(Shetsen, , 1990Rains et al, 1993).…”

Section: Hummocky Terrain Tracts and Flow Paths: Landform And Sedimentmentioning

confidence: 99%

In defence of the meltwater (megaflood) hypothesis for the formation of subglacial bedform fields

Shaw

2009

J Quaternary Science

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Shaw, J. 2010. In defence of the meltwater (megaflood) hypothesis for the formation of subglacial bedform fields.ABSTRACT: Characteristics of large-scale fluting and hummocky terrain on the Canadian Prairies test glacial and meltwater hypotheses for landform genesis. These tests defend the meltwater model. Neither sedimentary nor glaciotectonic processes can fully explain such erosional landforms. Province-scale flow paths, which mark palaeo-ice streams and subglacial flood routes, contain large-scale fluting with flanking hummock terrain. Antecedent relief causes these paths to differ from other flood landscapes such as the Scablands. Proponents of the glacial hypothesis use an invalid analogy between Icelandic and Prairie landsystems. They suggest that groove-ploughing formed largescale fluting, and that ice pushing created hummocky terrain. However, landform location, form, and extent, surface lags, truncated architecture, and landform associations favour the meltwater hypothesis. A simple thought experiment and clear understanding of the principle of least number of assumptions answer the criticisms that meltwater forms cannot cross-cut and that the meltwater hypothesis disregards proper hypothesis testing. An example of cross-cutting erosional marks supports this theory. No narrow tract of smoothed terrain with fluting terminates at the glacially thrust Neutral Hills, negating an important point in the glacial hypothesis. While neither the glacial hypothesis nor postglacial winnowing explain boulder and cobble lags with percussion marks, meltwater processes explain them well.

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Section: Hummocky Terrain Tracts and Flow Paths: Landform And Sedimentmentioning

confidence: 99%

In defence of the meltwater (megaflood) hypothesis for the formation of subglacial bedform fields

Shaw

2009

J Quaternary Science

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“…Jö kulhlaups drain onto gently sloping outwash plains, commonly called sandurs, which have been built-up by deposition of suspended load and bed load from proglacial drainage rivers. The catastrophic floods can sculpt [Kor and Cowell, 1998] and scour bedrock, add sediment to the sandur [Maizels, 1989a[Maizels, , 1989b[Maizels, , 1993, deposit icebergs that later melt and form kettles [Tómasson, 1996], create drumlins [e.g., Kor and Cowell, 1998;Shaw et al, 1996] carve new channels, and create various flood morphologies [e.g., Rains et al, 1993]. As with any stream, the effect of the jökulhlaups on the surrounding plains depends on the severity of the flood itself, on the sediment load, etc.…”

Section: Outflow Of Meltwatermentioning

confidence: 99%

Chasma Boreale, Mars: Topographic characterization from Mars Orbiter Laser Altimeter data and implications for mechanisms of formation

Fishbaugh

2002

J. Geophys. Res.

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[1] Chasma Boreale, a large reentrant in the north polar cap of Mars, is distinct in scale, detailed topography, and orientation from the spiraling troughs that characterize the majority of the polar cap. We use new, high-resolution Mars Orbiter Laser Altimeter (MOLA) data and Mars Orbiter Camera (MOC) and Viking images of the chasma region to assess hypotheses of origin of Chasma Boreale. These hypotheses include formation by glacial flow and ablation, by eolian processes (such as katabatic winds) and sublimation, by outflow of meltwater, or by a combination of two or more of these processes. We find that these new data support initial formation by outflow of meltwater with later modification by katabatic winds and sublimation. On the basis of our analysis we suggest a possible scenario in which outflow has occurred in several stages. The outflow appears to have begun near an enclosed depression at the head of the chasma; meltwater migrated within and below the ice down the regional slope and eventually broke out to the surface. Removal of material by melting caused subsidence and erosion of the polar deposits forming the chasma, which has subsequently undergone modification by eolian and sublimation processes. The outflow deposited most of its sediment in the form of a lobe that stratigraphically overlies the polygonal plains mapped at the mouth of the chasma and scoured some of the circumpolar sediment mantle in the surrounding region. The lowest portions of the North Polar Basin received the rest of the sediment as a deposit a few meters thick. MOLA data also reveal evidence for similar events of smaller magnitude elsewhere on the margins of the polar cap.

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“…They are inferred to have been prominent features of the Laurentide Ice Sheet, playing a vital role in its flow dynamics and mass balance (Marshall et al 1996), and serving as important agents of glacial dispersal and till formation. Their distribution reflects bed topography, subglacial sediment properties, and subglacial thermal and hydrological regimes (Boulton 1996a, b;Marshall et al 1996;Shaw et al 1996).…”

Section: Ice Sheet Modelsmentioning

confidence: 99%

“…Largescale, catastrophic subglacial meltwater floods have been interpreted to have formed significant parts of the landform record attributed to ice (Shaw 1990;Shaw et al 1996). Meltwater features include varied erosional marks and forms developed in bedrock (e.g.…”

Section: Glacial Erosionmentioning

confidence: 99%

A Quaternary geological perpective on geochemical exploration in glaciated terrain

Klassen

2001

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The application of Quaternary geology and glacial sedimentology is given as a broad guide for geochemical exploration in glaciated terrain. Predictive models of glacial dispersal provide an important basis for tailoring drift prospecting methods to suit regional variations in ice flow history and dynamics. The models relate compositional variations in glacial dispersal trains to ice flow direction, glacial history and subglacial processes. They are continually refined with reference to the geological and physical properties of the ice bed; new empirical field evidence constraining particle trajectories; and knowledge of subglacial processes affecting glacial erosion, transport and deposition. Transport at the ice bed leads to an exponential decrease in indicator concentrations with increasing distance of glacial transport, whereas linear decrease is associated with englacial transport, and may be characteristic of ice streams. The partitioning of rock and mineral fragments through subglacial comminution leads to compositional differences among size fractions that can reflect intensity of subglacial process, distance of transport, and provenance; hence, the choice of size fraction is important to drift prospecting by geochemical methods.Drift prospecting is based on the premise that lithological, mineralogical or geochemical indicators of economic mineralization can be traced in glacial deposits to locate their bedrock source. Of the varied types of glacial sediment, till is most directly related to bedrock composition and has been successfully used as a sample medium for mineral exploration. Till is mechanically derived from bedrock and preglacial sediments along the path of ice flow, and modified by glacial processes of erosion, transport and deposition. Till geochemistry is determined by its constituent rock fragments and mineral grains, including both common rockforming minerals and economic indicators such as sulphides. Hence, in glaciated terrain the practice of geochemical exploration is firmly linked to our understanding of clastic sedimentology and glacial process. As such,

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Erratum: Laurentide subglacial outburst floods: landform evidence from digital elevation models

Cited by 13 publications

References 0 publications

In defence of the meltwater (megaflood) hypothesis for the formation of subglacial bedform fields

In defence of the meltwater (megaflood) hypothesis for the formation of subglacial bedform fields

Chasma Boreale, Mars: Topographic characterization from Mars Orbiter Laser Altimeter data and implications for mechanisms of formation

A Quaternary geological perpective on geochemical exploration in glaciated terrain

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