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Добірка наукової літератури з теми "Subglacial bedforms"

Автор: Grafiati
Опубліковано: 10 грудня 2022
Оновлено: 28 січня 2023

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Статті в журналах з теми "Subglacial bedforms"

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Vérité, Jean, Édouard Ravier, Olivier Bourgeois, Stéphane Pochat, Thomas Lelandais, Régis Mourgues, Christopher D. Clark, Paul Bessin, David Peigné, and Nigel Atkinson. "Formation of ribbed bedforms below shear margins and lobes of palaeo-ice streams." Cryosphere 15, no. 6 (June 28, 2021): 2889–916. http://dx.doi.org/10.5194/tc-15-2889-2021.

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Abstract. Conceptual ice stream land systems derived from geomorphological and sedimentological observations provide constraints on ice–meltwater–till–bedrock interactions on palaeo-ice stream beds. Within these land systems, the spatial distribution and formation processes of ribbed bedforms remain unclear. We explore the conditions under which these bedforms may develop and their spatial organization with (i) an experimental model that reproduces the dynamics of ice streams and subglacial land systems and (ii) an analysis of the distribution of ribbed bedforms on selected examples of palaeo-ice stream beds of the Laurentide Ice Sheet. We find that a specific kind of ribbed bedform can develop subglacially through soft-bed deformation, where the ice flow undergoes lateral or longitudinal velocity gradients and the ice–bed interface is unlubricated; oblique ribbed bedforms develop beneath lateral shear margins, whereas transverse ribbed bedforms develop below frontal lobes. We infer that (i) ribbed bedforms strike orthogonally to the compressing axis of the horizontal strain ellipse of the ice surface and (ii) their development reveals distinctive types of subglacial drainage patterns: linked cavities below lateral shear margins and efficient meltwater channels below frontal lobes. These ribbed bedforms may act as convenient geomorphic markers to reconstruct lateral and frontal margins, constrain ice flow dynamics, and infer meltwater drainage characteristics of palaeo-ice streams.
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Knight, Jasper, G. McCarron Stephen, and A. Marshall McCabe. "Landform modification by palaeo-ice streams in east-central Ireland." Annals of Glaciology 28 (1999): 161–67. http://dx.doi.org/10.3189/172756499781821616.

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AbstractIn eastern Ireland, subglacial bedforms including drumlins and Rogen moraines were modified by headward erosion along two ice streams which had overlapping flow tracks. The ice streams, which had tidewater termini, are dated by geochronometric and morphostratigraphic methods to <15.014 C kyr BP (Castleblaney ice stream) and ~13.814C kyr BP (Armagh ice stream). Bedforms along ice-stream tracks show a morphological continuum which reflects a down-ice increase in the degree of modification by ice-stream activity (i.e. resulting in unmodified →remoulded/overprinted →crosscut →streamlined bedforms). The down-ice changes in bedform types are inferred to relate to changes in subglacial drainage and sediment-transport mechanisms. Bedform and sedimentary evidence suggest that discrete subglacial meltwater channels which developed up- ice changed in a down-ice direction to unchannelized flows which deepened towards the ice margin. Meltwater release from subglacial cavities, and produced by strain heating at sheared ice-stream margins, probably helped support ice-stream flow, which ended as the volume of subglacial meltwater discharge decreased. Dated millennial-scale cycles of ice activity may be related to instability at tidewater margins, followed by complex thermal and hydraulic responses within the ice mass.
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Menzies, J., and J. Rose. "Subglacial bedforms—an introduction." Sedimentary Geology 62, no. 2-4 (May 1989): 117–22. http://dx.doi.org/10.1016/0037-0738(89)90111-5.

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4

Riverman, Kiya L., Sridhar Anandakrishnan, Richard B. Alley, Nicholas Holschuh, Christine F. Dow, Atsuhiro Muto, Byron R. Parizek, Knut Christianson, and Leo E. Peters. "Wet subglacial bedforms of the NE Greenland Ice Stream shear margins." Annals of Glaciology 60, no. 80 (December 2019): 91–99. http://dx.doi.org/10.1017/aog.2019.43.

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AbstractWe describe elongate, wet, subglacial bedforms in the shear margins of the NE Greenland Ice Stream and place some constraints on their formation. Lateral shear margin moraines have been observed across the previously glaciated landscape, but little is known about the ice-flow conditions necessary to form these bedforms. Here we describe in situ sediment bedforms under the NE Greenland Ice Stream shear margins that are observed in active-source seismic and ground-penetrating radar surveys. We find bedforms in the shear margins that are ~500 m wide, ~50 m tall, and elongated nearly parallel to ice-flow, including what we believe to be the first subglacial observation of a shear margin moraine. Acoustic impedance analysis of the bedforms shows that they are composed of unconsolidated, deformable, water-saturated till. We use these geophysical observations to place constraints on the possible formation mechanism of these subglacial features.
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Shaw, John. "The meltwater hypothesis for subglacial bedforms." Quaternary International 90, no. 1 (April 2002): 5–22. http://dx.doi.org/10.1016/s1040-6182(01)00089-1.

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Greenwood, Sarah L., and Chris D. Clark. "Subglacial bedforms of the Irish Ice Sheet." Journal of Maps 4, no. 1 (January 2008): 332–57. http://dx.doi.org/10.4113/jom.2008.1030.

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Rea, Brice R., David J. A. Evans, Tom S. Dixon, and W. Brian Whalley. "Contemporaneous, localized, basal ice-flow variations: implications for bedrock erosion and the origin of p-forms." Journal of Glaciology 46, no. 154 (2000): 470–76. http://dx.doi.org/10.3189/172756500781833197.

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AbstractA detailed study of a proglacial bedrock site and a subglacial cavity of an outlet of Øksfjordjøkelen, Norway, is presented together with observations from the foreland of Konowbreen, Spitsbergen. Striation directions and subglacial observations indicate that local ice-flow paths were highly variable, deviating at angles of approximately 90° from the main ice-flow direction. Stepped bedrock topography appears conducive to the production of highly variable ice-flow paths, because the high bed roughness creates a locally variable stress regime within the ice, including low-pressure, lee-side areas into which ice can flow. If ice flow is sustained along a specific path and the ice contains debris, then abrasion should produce an erosional bedform. Models are proposed whereby locally variable ice-flow patterns could produce erosional bedforms, which would be described as p-forms, purely through mechanical abrasion.
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STOKES, CHRIS R., MARTIN MARGOLD, and TIMOTHY T. CREYTS. "Ribbed bedforms on palaeo-ice stream beds resemble regular patterns of basal shear stress (‘traction ribs’) inferred from modern ice streams." Journal of Glaciology 62, no. 234 (May 10, 2016): 696–713. http://dx.doi.org/10.1017/jog.2016.63.

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Анотація:
Rapidly-flowing ice streams are an important mechanism through which ice sheets lose mass, and much work has been focussed on elucidating the processes that increase or decrease their velocity. Recent work using standard inverse methods has inferred previously-unrecognised regular patterns of high basal shear stress (‘sticky spots’ >200 kPa) beneath a number of ice streams in Antarctica and Greenland, termed ‘traction ribs’. They appear at a scale intermediate between smaller ribbed moraines and much larger mega-ribs observed on palaeo-ice sheet beds, but it is unclear whether they have a topographic expression at the bed. Here, we report observations of rib-like bedforms from DEMs along palaeo-ice stream beds in western Canada that resemble both the pattern and dimensions of traction ribs. Their identification suggests that traction ribs may have a topographic expression that lies between, and partly overlaps with, ribbed moraines and much larger mega-ribs. These intermediate-sized bedforms support the notion of a ribbed bedform continuum. Their formation remains conjectural, but our observations from palaeo-ice streams, coupled with those from modern ice masses, suggest they are related to wave-like instabilities occurring in the coupled flow of ice and till and modulated by subglacial meltwater drainage. Their form and pattern may also involve glaciotectonism of subglacial sediments.
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Baltrūnas, Valentinas, Richard I. Waller, Vaidotas Kazakauskas, Stasys Paškauskas, and Valentas Katinas. "A comparative case study of subglacial bedforms in northern Lithuania and south-eastern Iceland." Baltica 27, no. 2 (February 20, 2014): 75–92. http://dx.doi.org/10.5200/baltica.2014.27.18.

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This paper aims to compare the dynamics of the subglacial environment as determined by an analysis of the structure and sedimentology of both Pleistocene and modern glacial deposits. Investigations focused on subglacial sediments in areas of streamlined relief in northern Lithuania (Ruopiškiai megascale subglacial lineations - MSGL) and south-eastern Iceland (drumlinised terrain exposed by the recent retreat of Skeiðarárjökull glacier). Sedimentological analyses involved granulometry, till macrofabrics, and the anisotropy of magnetic susceptibility (AMS) of micro-clasts. Comparative investigations of subglacial bedforms exposed at Ruopiškiai and Skeiðarárjökull highlighted differences in their formation and post-genetic transformation. In both cases, their initiation was associated with ice advance and subglacial sediment deformation. However, subsequent dynamics were different.
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Hillier, J. K., M. J. Smith, C. D. Clark, C. R. Stokes, and M. Spagnolo. "Subglacial bedforms reveal an exponential size–frequency distribution." Geomorphology 190 (May 2013): 82–91. http://dx.doi.org/10.1016/j.geomorph.2013.02.017.

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Частини книг з теми "Subglacial bedforms"

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O’Brien, P. E., G. Leitchenkov, and P. T. Harris. "Iceberg Plough Marks, Subglacial Bedforms and Grounding Zone Moraines in Prydz Bay Antarctica." In Glaciated Continental Margins, 228–31. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5820-6_81.

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Тези доповідей конференцій з теми "Subglacial bedforms"

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Ruscica, Phillip, Nick Eyles, Shane Sookhan, and Syed Bukhari. "EROSIONALLY-STREAMLINED SUBGLACIAL BEDFORMS, AND ICE MARGINAL PRESSED MORAINES ON THE BED OF A PALEO ICE STREAM: GREEN BAY LOBE, WISCONSIN USA: LIDAR MAPPING OF A SOFT-BED ICE STREAM LANDSYSTEM." In GSA 2020 Connects Online. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020am-359117.

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Звіти організацій з теми "Subglacial bedforms"

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Eyles, N., R. P. M. Mulligan, R. C. Paulen, and S. Sookhan. Subglacial bedforms in southern Ontario - from flood paths to flow sets: CANQUA/AMQUA 2018 post-conference field trip. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2018. http://dx.doi.org/10.4095/313040.

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