The structural glaciology of Kongsvegen, Svalbard, and its role in landform genesis

Glasser, Neil F.; Hambrey, Michael J.; Crawford, Kevin; Bennett, Matthew R.; Huddart, David

doi:10.1017/s0022143000002422

Cited by 67 publications

(85 citation statements)

References 23 publications

(5 reference statements)

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“…This material is then exposed during the quiescent phase as characteristic landformsediment assemblages or surge landsystems [cf., Rea, 1999, 2005]. Sediment is also exposed within the ice as englacial debris inclusions or bands [e.g., Glasser et al, 1998;Woodward et al, 2002], hereafter referred to as debris-rich englacial structures. Better understanding of the links between surging, debris entrainment, and geomorphology is important as it can help to provide an insight into processes acting at the bed [Christoffersen et al, 2005;Larsen et al, 2006].…”

Section: Introductionmentioning

confidence: 99%

“…Two main mechanisms have been proposed for the origin of upglacier-dipping structures: (1) debris-bearing thrust faults originating from the bed in a zone of longitudinal compression [e.g., Hambrey and Dowdeswell, 1997;Glasser et al, 1998;Lønne, 2006;Larsen et al, 2010] and (2) the deformation of structures initially formed as vertical crevasse squeezes, which are then reoriented in a down-ice direction during quiescent phase ice flow. This forms a favorably inclined slip plane along which thrust-style displacement (TSD) can occur during a subsequent surge Woodward et al, 2002;Rea and Evans, 2011].…”

Section: Introductionmentioning

confidence: 99%

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Debris entrainment and landform genesis during tidewater glacier surges

et al. 2015

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The englacial entrainment of basal debris during surges presents an opportunity to investigate processes acting at the glacier bed. The subsequent melt-out of debris-rich englacial structures during the quiescent phase produces geometrical ridge networks on glacier forelands that are diagnostic of surge activity. We investigate the link between debris entrainment and proglacial geomorphology by analyzing basal ice, englacial structures, and ridge networks exposed at the margins of Tunabreen, a tidewater surge-type glacier in Svalbard. The basal ice facies display clear evidence for brittle and ductile tectonic deformation, resulting in overall thickening of the basal ice sequence. The formation of debris-poor dispersed facies ice is the result of strain-induced metamorphism of meteoric ice near the bed. Debris-rich englacial structures display a variety of characteristics and morphologies and are interpreted to represent the incorporation and elevation of subglacial till via the squeezing of till into basal crevasses and hydrofracture exploitation of thrust faults, reoriented crevasse squeezes, and preexisting fractures. These structures are observed to melt-out and form embryonic geometrical ridge networks at the base of a terrestrially grounded ice cliff. Ridge networks are also located at the terrestrial margins of Tunabreen, neighboring Von Postbreen, and in a submarine position within Tempelfjorden. Analysis of network characteristics allows these ridges to be linked to different formational mechanisms of their parent debris-rich englacial structures. This in turn provides an insight into variations in the dominant tectonic stress regimes acting across the glacier during surges.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Debris entrainment and landform genesis during tidewater glacier surges

et al. 2015

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“…The entrainment of debris at glacier beds, and its subsequent transport, also provides an important supply of material to the margins. Such entrainment, elevation, and transport is likely to be most effective under warm-based conditions, which facilitate the development of debris-rich basal ice sequences (Sharp et al, 1994;Knight, 1997), debris-rich shear planes (Glasser et al, 1998), and injections of debris into basal crevasses (Rea and Evans, 2011). It is suggested that the entrainment of subglacial debris is particularly efficient on the adverse slopes of overdeepenings, where supercooling processes result in the formation of debris-rich basal ice (Cook et al, 2010) and debris is entrained and elevated via shear planes (Swift et al, 2002).…”

Section: Supply Of Debris To Glacier Marginsmentioning

confidence: 99%

A review of topographic controls on moraine distribution

2014

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Ice-marginal moraines are often used to reconstruct the dimensions of former ice masses, which are then used as proxies for palaeoclimate. This approach relies on the assumption that the distribution of moraines in the modern landscape is an accurate reflection of former ice margin positions during climatically controlled periods of ice margin stability. However, the validity of this assumption is open to question, as a number of additional, nonclimatic factors are known to influence moraine distribution. This review considers the role played by topography in this process, with specific focus on moraine formation, preservation, and ease of identification (topoclimatic controls are not considered). Published literature indicates that the importance of topography in regulating moraine distribution varies spatially, temporally, and as a function of the ice mass type responsible for moraine deposition. In particular, in the case of ice sheets and ice caps ( > 1000 km 2 ), one potentially important topographic control on where in a landscape moraines are deposited is erosional feedback, whereby subglacial erosion causes ice masses to become less extensive over successive glacial cycles. For the marine-terminating outlets of such ice masses, fjord geometry also exerts a strong control on where moraines are deposited, promoting their deposition in proximity to valley narrowings, bends, bifurcations, where basins are shallow, and/or in the vicinity of topographic bumps. Moraines formed at the margins of ice sheets and ice caps are likely to be large and readily identifiable in the modern landscape. In the case of icefields and valley glaciers (10-1000 km 2 ), erosional feedback may well play some role in regulating where moraines are deposited, but other factors, including variations in accumulation area topography and the propensity for moraines to form at topographic pinning points, are also likely to be important. This is particularly relevant where land-terminating glaciers extend into piedmont zones (unconfined plains, adjacent to mountain ranges) where large and readily identifiable moraines can be deposited. In the case of cirque glaciers (< 10 km 2 ), erosional feedback is less important, but factors such as topographic controls on the accumulation of redistributed snow and ice and the availability of surface debris, regulate glacier dimensions and thereby determine where moraines are deposited. In such cases, moraines are likely to be small and particularly susceptible to post-depositional modification, sometimes making them difficult to identify in the modern landscape. Based on this review, we suggest that, despite often being difficult to identify, quantify, and mitigate, topographic controls on moraine distribution should be explicitly considered when reconstructing the dimensions of palaeoglaciers and that moraines should be judiciously chosen before being used as indirect proxies for palaeoclimate (i.e., palaeoclimatic inferences should only be drawn from moraines when topographic controls on mora...

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“…Material released from this folded ice can be observed on the ice surface as a medial moraine set, that is subparallel to ice fl ow. Secondly, fractures transverse to the ice fl ow are connected mostly with trusting and shearing processes Glasser et al, 1998) and compressive ice fl ow. This compression is typical for the snout part and for the zone between warmer and colder part of a glacier -in case of polythermal valley glaciers (Lucas, 2005).…”

Section: Introductionmentioning

confidence: 99%

“…The role of ice structure in landforms development has been slightly studied (Boulton, 1967(Boulton, , 1972Hambrey et al 1997Hambrey et al , 1999Glasser et al, 1998;Lucas, 2005;Graham et al, 2007;Lucas, 2007) and some papers only mention this problem (e.g. Lyså & Lønne, 2001).…”

Section: Introductionmentioning

confidence: 99%

Glacier ice structures influence on moraines developement (Hørbye glacier, Central Spitsbergen)

Szuman

Kasprzak

2010

Quaestiones Geographicae

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ABSTRACT. Geomorphological and basic sedimentological investigation of controlled moraine system was carried out at the ice surface and within the moraine complex zone of the Hørbye glacier (Central Spitsbergen). The Hørbye glacier creates controlled moraine chains regarding transversal fractures and longitudinal foliation. The forms parallel to the ice fl ow direction are represented by medial moraines, whereas transversal ones by thrustmoraines. Both arrangements are clearly visible. However, thrust and shear planes are more effective in creating forms, both on the ice surface and in the moraine complex. The longitudinal landforms are less distinct, moreover they are coarser-grained and worse rounded, in contrast to the material from shear and thrust plains which is fi ner and better rounded. The study area can be divided into three subzones: clean ice surface, debris covered ice fractures and moraine complex. The outer and inner sandur plain were not taken under consideration. It is suggested that present arrangement of both thrust or shear plains and longitudinal foliation controls formation of foreland relief. This hypothesis has a particular sense in understanding construction of modern sedimentary basins as well as the mechanism of terminoglacial relief formation with regend to ice structure.

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The structural glaciology of Kongsvegen, Svalbard, and its role in landform genesis

Cited by 67 publications

References 23 publications

Debris entrainment and landform genesis during tidewater glacier surges

Debris entrainment and landform genesis during tidewater glacier surges

A review of topographic controls on moraine distribution

Glacier ice structures influence on moraines developement (Hørbye glacier, Central Spitsbergen)

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