Ice Sheet

Our maps show seven different landsystems (Fig. 6.6). We restrict our discussion here to the four landsystems that we believe are linked to bed conditions and glacier dynamics during the LGM No data -100 ft. I 100-200 ft. I 200-400 ft. No data -100 ft. I 100-200 ft. I 200-400 ft. Figure 6.4 Four of the nine input data themes used in creating the landsystem maps. A) Distribution of drumlins. B) Eskers and other ice-contact deposits. C) Glacial sediment thickness from Soller and Packard (1998)....

Conclusion

The ability to identify former surging glaciers is crucial for reconstruction and interpretation of the dynamics of former ice sheets. However, no individual landform, except probably concertina eskers which are difficult to identify in the ancient landform record, can be unequivocally labelled as the product of glacier surging. The surging glacier landsystem presented in this chapter combines observations on the geomorphology, sedimentology and glaciology of surging glaciers in Iceland,...

Proglacial Aeolian Landsystems

Supraglacial debris or morainic, glacilacustrine and glacifluvial sediments may be rich in silt and fine-grained sand. Aeolian processes easily deflate the fine-grained material within these deposits and complex suites of glacioaeolian landforms are present within many valley glacial environments (Derbyshire and Owen, 1996). Patterns of sediment transport are strongly influenced by local wind systems, including katabatic, anabatic and fohn winds. In some regions such as the Himalaya in northern...

Paraglacial Landsystems

The term 'landsystem' is generally employed to decribe a large-scale grouping of landforms and related sediment facies that characterize a particular geomorphic context or environment (Eyles, Figure 17.3 Effects of extrinsic perturbations on the exhaustion model of paraglacial sediment release. Factors that may trigger a rejuvenated paraglacial response (during the initial period of paraglacial activity) or a renewed paraglacial response (after the initial period of paraglacial activity)...

Discussion And Conclusion

We have reviewed the broader aspects of ice-marginal landform distribution in the continuous permafrost zone of northern Canada. The environment places constraints on possible basal ice thermal conditions in glacier marginal and sub-marginal zones throughout glacial cycles. Ice caps necessarily nucleated and expanded on pre-existing permafrost. The permafrost then either survived throughout the glacial cycle or reformed upon or prior to deglaciation. Ice-marginal landforms and bedforms in this...

The Sedimentary Record of Large Proglacial Lakes

Transport Clayey Till

As glaciers melted, they relinquished their load of sediment. The hydrology and sediment transport in glacial rivers and lakes have been studied by many (e.g. Church and Gilbert, 1975 Figure 14.2 Examples of water level changes in a basin (levels 1, 2, 3, and 4 in bathtubs) undergoing differential isostatic rebound, where the outlet is in the southern end (S), northern end (N), and in the middle of the basin. A) Outlet at southern end. Lake regresses throughout basin and blanket of sand may be...

Towards a Depositional Model

Our knowledge of polar continental landform and sediment assemblages is incomplete. Consequently a comprehensive depositional model cannot yet be assembled. However, several elements of a model can be identified. 1. Relatively low volumes of sediment are produced by polar glaciers. Consequently landform and sediment assemblages have modest volumes and the preservation potential of ice-contact landforms is low. 2. A variety of constructional moraines form at stable ice-margins. The most common...

Geomorphology and Depositional Systems

The external forces on fjord landsystems described above tend to act over periods of several thousand to tens of thousands of years, but they remain significant when trying to understand the system over full glacial periods. Over the shorter term, local processes are the significant factors in generating a fjord landsystem record. Here we will discuss the major processes that go to producing different depositional systems, geomorphological units and allostratigraphic units within fjords, and...

Overlaps with other Glacigenic Landsystems

Important questions are how unique is the sub-polar glacier landsystem and to what extent can it be differentiated from other terrestrial and subaquatic glacigenic landsystems This is important for understanding the nature of glaciers and ice sheets in the geological record, particularly in terms of their basal thermal regime and, hence, past climate. The sub-polar glacier landsystem contains elements that are common to several other landsystems discussed in this book. Thrust-block moraines...

Area Altitude Relationship for Plateau Icefields

Plateau Margin Retreat

Many reconstructions of glaciation in mountain regions have ignored the potential impact of plateaux on glacier mass balance, probably due to the fact that early research focused largely on alpine regions. However, the general controls on plateau icefield existence were established by Manley (1955, 1959). He suggested that the larger the breadth of a glacier summit, perpendicular to the prevailing accumulation season wind, the closer to the regional snow firn line an ice cover can be sustained....

And Lakes

Features Strain Sedimentary

Meltwater plays an important role in ice-marginal landsystems. Where a glacial margin stagnates, sediment accumulates in the form of outwash fans (sandur) and glacifluvial deltas. A new advance may incorporate these sediment bodies into thrust moraines. Lakes form where glacial advances block ice-marginal valleys. These lakes may cause permafrost to decay over large areas, thus generating an important morphodynamic control on glacial advances. The area covered by the Rehburg advance during the...

Ancient Records of Active Temperate Glacier margins

As active temperate glaciers provide us with a clear impression of their former passage, their impacts on ancient glaciated terrains should be identifiable. One excellent example in western Subglacial deposition Subglacial erosion Subglacial deposition Subglacial erosion Canada has been identified by Evans et al. (1999a). In an extensive area deglaciated by the westernmost ice lobe of the southwest Laurentide Ice Sheet, between Calgary and Granum, Alberta, numerous closely spaced, low-amplitude...

Ijq

Figure 2.1 1 Details of subglacial sediment sequences at the margins of Icelandic glaciers showing typical vertical transitions from glacitectonized stratified sediments to overlying tills. A) Composite stratigraphic log from Skalafellsjokull showing various lithofacies and interpreted relative strain curve (from Evans, 2000a). B) Vertical profile log of section on the south shore of BreiSarlon on the BreiSamerkurjokull foreland showing a till with a possible A and B horizon superimposed on the...

Impact Of Plateau Ice On Reconstructed Equilibrium Line Altitudes

Once the presence of glaciers has been confirmed by the application of a landsystems approach, palaeo-climate reconstructions can be undertaken based upon the limits and interpreted dynamics of the glacier coverage. Where plateau icefields existed but left little or no evidence of their presence they have often been ignored and reconstructions have been confined to valley glaciers only (e.g. Sissons, 1980 Ballantyne, 1990). In the following subsections the potential impact of overlooking...

Glacial Landsystems

Drumlin Formation

Mapping in glaciated terrains traditionally involved the grouping of landforms according to common origin and age. An excellent early example of this approach is that of Speight (1963) in the Lake Pukaki area of South Island, New Zealand. Suites of glacial features grouped as 'landform associations' essentially constituted inset sequences of glaciated valley landsystems (see below). The linking of process and form over a large area of diverse glacial landforms was pioneered by Clayton and Moran...

Application of Landsystem Models

Hypothesized palaeo-ice streams from the major ice sheets have been reviewed (Stokes and Clark, 2001), and elements of the criteria and landsystems models above are inherent to many of the arguments that authors have used for demonstrating the existence of ice streams. From the above consideration of marine and terrestrial ice streams, and those that leave a rubber-stamped or smudged imprint, we construct four landsystem models that we expect ice streams may leave behind as evidence (Fig....

R i i i r

Downwasting glacier surface AD 1945-1978 Figure 17.4 A) Cross-section through a rockslide initiated by recent downwastage of the Maud glacier in New Zealand (adapted from McSaveney, 1993). B) Cross-section through a rock slope failure initiated by downwastage of an outlet glacier of the Myrdalsjokull ice cap, southern Iceland (adapted from Sigurdsson and Williams, 1991). assumptions the overall probability of failure within a given area diminishes exponentially with time elapsed since...

Contents

Chapter 1 Introduction to glacial landsystems 1 1.3 Aims and Scope of this Book 10 Chapter 2 Ice-Marginal Terrestrial Landsystems Active 2.2 Landform-Sediment Assemblages in Active Temperate 2.3 Ancient Records of Active Temperate Glacier Margins 35 Chapter 3 Ice-Marginal Terrestrial Landsystems Sub-Polar Glacier Margins of the Canadian and Greenland High Arctic 44 Colm 0 Cofaigh, David JA. Evans and John England 3.2 Sub-Polar Glaciers in the Canadian and Greenland 3.3 Glacial Geology and...

Classification

1977 Aerial Photograph Hummocks

Figure 6.5 Flow-chart showing the classification methods used to create the landsystem maps (see Fig. 6.6). Input layers on the left were classified into the seven landsystems shown on the right. The order and type of classification are shown in the middle. The numbers show the order in which the classification was carried out. Classification was done by using a series of structured-query-language commands on the database tables. Figure 6.5 Flow-chart showing the classification methods used to...

Introduction

Lithuania Last Glacial Margin

Bands and tracts of hummocks commonly mark the former margins of the great ice sheets that covered Europe and North America during the Late Pleistocene. These landforms are best explained as forming by the collapse of abundant supraglacial debris during the melting of stagnant glacier ice, and hence are said to make up the supraglacial landsystem. It is also possible that subglacial squeezing of soft till contributes to landform development, and, in that case, this landsystem may be better...

Paraglacial Sedimentation In Lakes

During deglaciation, many lakes experience an upwards depositional succession from proximal, ice-contact sediment accumulation, to ice-distal sedimentation, to paraglacial sedimentation (e.g. van Husen, 1979 Eberle, 1987 M ller, 1999). Proximal glacilacustrine sedimentation is characterized by the formation of ice-contact deltas, subaqueous fans and moraines, submerged ramps produced by subaqueous mass movement and rhythmic laminated bottom sediments (Ashley, 1995). Distal glacilacustrine...

James T Teller

Whenever glaciers impede drainage, topographic closure may occur, resulting in the ponding ofrunoff. The term 'proglacial lake' has been used for lakes that owe their existence to the presence of a confining glacier margin (ice-marginal lakes), and for lakes that were strongly influenced by glacial meltwater, but which lay in a closed depression not directly in contact with the ice. In some ways this distinction is academic, and it is also arbitrary as to when a meltwater-fed lake not bounded...

C2S e

Figure 2.4 The main modes of push moraine formation. A) Subglacial deformation and ice-marginal squeezing. (After Price, 1970 Sharp, 1984 Johnson and Hansel, 1999). The subglacial deforming layer is extruded or squeezed out at the glacier margin as depicted by the arrow. B) 'Double-layer annual melt-out' model of Matthews et al. (1995). Although the example shows the production of a large moraine by a stationary glacier snout, individual recessional moraines could also be produced in this way....

Frederik M Van der Wateren

During the Middle and Late Pleistocene, the Scandinavian Ice Sheets repeatedly covered the northern half of The Netherlands and Germany, most of Poland, Estonia, Latvia, Lithuania and Belarus, a small part in the north of the Czech Republic and the northern parts of Ukraine and Russia (Fig. 8.1). This chapter focuses on the southern part of the area glaciated by the Scandinavian Ice Sheets, between 49 N and 60 N, 3 E and 30 E. The landscapes left behind by the Southern Scandinavian Ice Sheets...

A

Glacier Diagram With Moraine And Drumlin

Their crenulate, lobate or saw-tooth plan-forms mimic the indentations of the snout margin produced by the melting back of longitudinal crevasses (Price, 1970 Matthews et al., 1979). At some locations push moraines may be coalescent or partially superimposed, indicating that one winter readvance was more extensive than that of the previous year. A stationary glacier snout may construct larger and more complex moraine ridges in this fashion (Kr ger, 1985, 1993). The local characteristics of push...

The Plateau Icefield Landsystem

This section integrates information from contemporary environments in the Canadian Arctic, north Norway and Iceland and provides the main criteria for identifying the former existence of plateau icefields in deglaciated landscapes. As mentioned above, glacierization may be experienced at both a smaller, local scale and at a larger, continental scale. If affected by both, the plateau icefield landsystem may comprise a composite signature. It is climate reconstructions of the smaller, local scale...

Ice Contact Landforms and Sediments

Three types of well-preserved ridges can be recognized at the ice edge in East Antarctic oases inner moraines, ice-contact fans screes and thrust-block moraines. Inner moraines form at the margin of the ice sheet where basal debris crops out and accumulates on the ice surface. Beyond the present ice margins older inner moraines often form prominent end moraines. Where an ice core remains in these moraines exposures reveal large recumbent folds with an amplitude of up to 6 m and numerous smaller...

Paraglacial Landsystems And Postglacial Landscape Change

Www Paraglacial Processes And Landforms

Subdivision of paraglacial landscape response into six landsystems (rock-slope, drift-slope, glacier foreland, alluvial, lacustrine and coastal) provides a useful context for analysis of process-landform-sediment relationships. This approach, however, fails to highlight the links between individual landsystems. Ballantyne (2002b) has suggested that this may be achieved by representing paraglacial response as an interrupted sediment cascade with four primary sediment sources (rockwalls,...

Brittle Shear Zone Structures

Shear zones in unlithified sediments rarely contain either only brittle- or only ductile-style deformations, usually the two are associated. Clay, which typically deforms in a ductile way, is sometimes cut by brittle structures due to strain hardening associated with loss of pore water. This association of brittle structures and ductile structures is illustrated by a shear zone beneath one of the nappes in the Dammer Berge thrust moraine (style D Van der Wateren, 1995). The sands and gravels of...

Regional Geology and Glacial Landsystems

The Scandinavian shield (Fig. 8.2), the core region of the Fennoscandian Ice Sheets, consists of Precambrian and Early Palaeozoic metamorphic and intrusive rocks (the same rocks that are found as erratics in all Pleistocene tills). These are covered at most with a sparse cover of Quaternary sediments. The Southern Scandinavian Ice Sheets covered areas almost completely underlain by large sedimentary basins. These basins separate the Scandinavian craton from the Variscan and Alpine orogens in...

S 10 Glaciated Valley Landsystems Synthesis

The wide variety of landforms and landform associations found in glaciated valleys reflects several interrelated controls. The most important identified in this Chapter are 1. topography, itself a function of tectonic and denudational history 2. debris supply to glacier surfaces, in particular the relative supply of debris and snow ice, which determines where glaciers will lie on the clean glacier debris-covered glacier rock glacier continuum, and 3. efficiency of sediment transport from the...

Qih

August post-ablation surface, sharp channels and grainy surface August post-ablation surface, sharp channels and grainy surface June pre-ablation surface, smooth ridqes snow fill, and glossy sublimation surflce' Dirty yellow ice Calved ice blocks -Summer stream Winter's drift accumulation Dirty yellow ice Calved ice blocks -Summer stream Winter's drift accumulation Increasing prism gf stagnant ice J Growing snowdrift J Figure 3.2 The evolution of the marginal profile of the Greenland Ice Sheet...

Characteristics of Existing Ice Streams

Ice Streams

Retaining Paterson's (1994) broad definition of ice streams as spatially restricted fast flow surrounded by slower moving ice, then there seem to be two main breeds of ice stream. 'Topographic ice streams' are fixed in position, their location predetermined by bedrock troughs through which they flow. In comparison with others they have higher surface slopes and driving stresses (typically 50 200 kPa), higher basal shear stresses and attain higher velocities. A classic example is Jakobshavns...

Landsystem Model for Palaeo Ice Streams

It would be highly unlikely that all of the geomorphological criteria should be found in one location, produced by a single ice stream. This is because not all ice streams will leave a complete geomorphological signature and because preservation and modification often obscure the complete picture. However, the criteria outlined above can be thought of as comprising a characteristic 'landsystem' produced by a former ice stream. This illustrates the perfect, or unaltered, geomorphological...

Paraglacial Driftmantled Slope Landsystems

Retreat of glacier ice in mountain areas often exposes valley-side slopes mantled by thick glacigenic deposits, usually composed of stacked lateral moraines (Mattson and Gardner, 1991 Ballantyne and Benn, 1994, 1996). Such deposits are susceptible to erosion by translational slope failure (slumping), debris flow, snow avalanches, streamflow and surface wash. These processes may completely rework drift-mantled slopes within a few decades or centuries, forming a paraglacial landsystem of...

Physical Setting and Timing of Glaciation

Ice advanced into the northern USA after 26,000 14C years BP, yet the LGM extent was reached at different times in different places (Mickelson et al., 1983). Lobes in the Great Lakes and New England regions reached their maximum before 21,000 14C years BP. Rapid decay of the ice sheet began after 14,500 14C years BP. Although lobes to the west of the Great Lakes also advanced before 21,000 14C years BP, they reached their maximum extent at about 14,000 14C years BP, out of phase with the rest...

Subpolar Glaciers in the Canadian and Greenland High Arctic

Due to the severity of the regional climate, much of the glacier ice in the Canadian and Greenland high arctic is below the pressure melting point, particularly where mean annual air temperatures and glacier thickness are low (Koerner, 1989). In the northern part of the region, this results in some glaciers terminating in the sea as ice shelves (Koenig et al., 1952 Hattersley-Smith, 1957 Crary, 1958, 1960 Dunbar, 1978 Jeffries, 1987 Lemmen et al., 1988 Higgins, 1989 Weidick, 1995). Because...

The Region And Its General Glacial Landscapes

The region is physiographically varied, ranging from the upland and lowland tundra on the Barren Grounds of the Arctic mainland west of Hudson Bay to the channels and islands of the Canadian Arctic Archipelago. Most of the region comprises undulatory plateaux and intervening wide valleys or lowlands, but extensively glaciated fretted mountains extend along the eastern margin of the region from Axel Heiberg and Ellesmere islands south to the Torngat Mountains of Labrador (Bird, 1967 Bostock,...

Paraglacial Alluvial Landsystems

Model River Incision

Paraglacial alluvial landsystems comprise three main categories of landform, namely debris cones, alluvial fans and valley fills. All three may be regarded as paraglacial sediment stores that form within a few centuries or millennia after deglaciation but which frequently experience later fluvial erosion due to decreased sediment supply and or base-level lowering. Research on recently deglaciated terrain has shown that small and intermediate-sized debris cones and alluvial fans may form,...

Glacitectonic Styles

The discussion by Hart et al. (1996, 1997) and Piotrowski et al. (1997) is a clear illustration of how different interpretations of sedimentary structures, and whether or not they have been significantly deformed by subglacial shearing, may lead to widely disparate interpretations of glacial landsystems. The reconstruction of the dynamics of former ice sheets requires that it can be determined whether sediments have either been sheared by overriding ice, or deposited by lodgement or subglacial...

The Supraglacial Landsystem Model

Eskers Diagram

The landforms described above result as stagnant ice, covered with supraglacial debris, slowly melts. In the lowland-terrain setting, supraglacial debris is derived initially from the base of the ice subglacial or basal-ice debris is moved upwards to englacial positions and, eventually, Figure 10.14 A dump ridge and an associated ice-marginal band of hummocky topography in central Minnesota. A) Figure of a portion of the Spider Lake and Bungo Creek, Minnesota 7.5' topographic quadrangles,...

B

Figure 2.12 Landforms produced in association with ice-margin parallel outwash tracts. A) High-elevation kame terraces and lower ice-margin parallel outwash tracts at the northern margin of Sandfellsjokull, Iceland. B) Push moraines composed of gravels derived from ice-contact outwash on the foreland of Heinabergsjokull, Iceland. evident in the proglacial area of BreiSamerkurjokull. This indicates that they are relatively stable forms that become adourned with subglacial features (drumlins and...

Discussion

We hypothesize that the types of landforms and sediments within a particular region are the result of how the ice sheet responded to the fundamental influences of climate, bed geology and topography. These influences were filtered in a non-linear manner by the ice sheet. The combination of these factors produced different dynamic behaviours of the ice-sheet margin and different depositional environments in various regions of northern USA. Below we discuss the influence of each factor on glacier...

Changes in Landsystem Distribution over Space and Time

Glacial landsystems change over space and time due to climate change. The Ben Ohau Range (New Zealand) demonstrates the response of a range of glaciated valley landsystems as glacier equilibrium altitudes (ELAs) have risen since Late Glacial time (Brazier et al., 1998). A steep precipitation gradient allows a variety of forms associated with humid and arid climates to have developed in close proximity. It is possible to see how landsystems within individual catchments have evolved as debris...

Ice Margins in Low Relief Landscapes

In East Antarctica the majority of the ice margin terminates in the sea. Relatively small parts of the ice margin terminate on land in small coastal oases. The largest oases in East Antarctica are the Vestfold Hills and Bunger Hills (Fig. 5.1). Recent investigations of the Quaternary history of these areas has suggested that the ice margin during the last glacial maximum was thinner and less extensive than previously thought (Colhoun et al., 1992) and that deglaciation was almost complete by...

Rock Glaciers

Adverse Slope Profile

Rock glaciers are tongue-like or lobate masses of ice and coarse debris that flow downslope by internal deformation. They commonly have ridges, furrows and sometimes lobes on their surfaces, and have steep fronts down which debris collapses and is then over-ridden by the advancing mass (Washburn, 1979 Ballantyne and Harris, 1994). A wide range of models has been proposed to Figure 15.16 Deposition of the medial moraine of the Haut Glacier d'Arolla by slow terminus retreat, giving juxtaposition...

Glacier Forelands

Glacier retreat exposes unvegetated valley-floor deposits that undergo paraglacial modification by mass movement, frost sorting, wind and running water, resulting in changes to both the Figure 17.8 Section through drift-mantled slopes, Fabergst0lsbreen, Norway. The upper massive clast-supported diamicton represents deposition by the glacier during the Little Ice Age. The underlying crudely-stratified diamicton consists of early Holocene paraglacial debris-flow deposits. The erosional contact...

Iceand Moraine Dammed Lakes

Sedimentation Within Glacial Lakes

Temporary lakes dammed by either glacier ice or moraines are common features of mountain environments, and are formed in four main situations (Yamada, 1998 Clague and Evans, 2000) 1. where a glacier emanating from a side-valley blocks the drainage of the trunk valley 2. where a glacier in a trunk valley blocks drainage from side valleys 3. at the junction between two valley glaciers, and 4. behind lateral-frontal moraines and outwash heads. Cases (1), (2) and (3) form during glacier advance,...

Paraglacial Coastal Landsystems

The concept of paraglacial coasts is dominated by the progressive release of a vast store of in situ and fluvially reworked glacigenic sediment into the nearshore and offshore sediment budget. This happens in two ways. First, the supply of reworked glacigenic sediment by rivers enhances sediment influx in estuarine and fjord-head locations. Second, where glacigenic sediments crop out in the littoral zone they are eroded directly by waves and tidal currents, introducing reworked sediment that...

Sedimentary Processes and External Forces

Sedimentary Process

Fjords are complex systems influenced by a wide range of processes, those processes interacting to produce positive and negative feedbacks on each other and controlling depositional systems. The major processes include glacial, fluvial, oceanic, iceberg, sea ice, aeolian, subaerial mass flow and Meltwater stream with high concentration of suspended matter Homogeneous mud with scattered ice-rafted pebbles, and organic varves Laminated mud sand deposited from the meltwater stream Meltwater stream...

Conclusions

Mapping glacitectonic styles is a powerful way to reconstruct former ice sheets and to identify the glaciological conditions existing at the time, if the following reservations are made. Not all thrust moraines are equally useful for a reconstruction of ice-sheet margins (Van der Wateren, 1995). If the subsurface geology is the main factor controlling the position of a line of thrust moraines, individual ridges do not have to be synchronous and the use of this line for an ice sheet Figure 8.21...

Glacial Landscape Zones

Glaciated landscapes are systematically ordered in a north to south progression, from simple to complex in terms of landscape alteration. The 'complex' southern landscape is the one that will be most familiar to geologists working south of the permafrost limit. In the far north, lateral meltwater channels cut into terrain that either lacks other forms of glacial modification or is weakly glacially scoured and bears a thin till cover with sparse, faint flutings. Moraines are rare but include...

Glacial History

Northwest Europe contains evidence of continental glaciation from the latest three cold stages, the Elsterian (Marine Oxygen Isotope Stages 14 and 12), Saalian (Stages 8 and 6) and Weichselian (Stages 4 and 2) (Bowen et al., 1986 Sibrava, 1986 Ehlers, 1996). The landscapes produced during these three cold stages differ markedly 1. The Elsterian glaciation is characterized by extensive systems of very deep (up to 400 m) tunnel valleys. They form an anastomosing pattern of generally overdeepened...

Significance of Palaeo Ice Streams

9.2.1 Palaeo-Ice Streams and Ice-Sheet Reconstructions The large flux within ice streams has a profound effect on ice sheet configurations, including drainage basin and ice divide locations, and local and regional ice sheet topography. This is demonstrated by the effect that ice streams have on the mass balance, flow configuration and ice Figure 9.1 An Antarctic ice stream (Byrd Glacier) viewed from a satellite image. Flow is towards the top of the image. Note the upstream convergence of flow...

Hypotheses of Palaeo Ice Stream Locations

As early as 1981, Denton and Hughes (1981) recognized the role ice streams likely played in the dynamics of former ice sheets and presented a hypothetical map of potential ice-stream locations (Fig. 9.2). These were predicted on the basis of obvious topographic troughs and on ice-sheet geometry. The map is highly speculative, as at the time there was little or no evidence for ice-stream existence, but it made the point that ice streams probably existed and significantly affected the topography,...

Summary of the Landsystems Model for Surging Glaciers

It has been demonstrated above that no single landform can be used to identify palaeo-glacier surging in the landform record. However, landform-sediment assemblages on the forelands of contemporary surging glaciers provide powerful diagnostic criteria for the recognition of surge imprints on the landscape (Figs. 11.15 and 11.16). Based upon a combination of observations from contemporary surging glacier margins, specifically Bruarjokull and Eyjabakkajokull, Iceland (Evans et al., 1999b Evans...

Ductile Shear Zone Structures

A deformation till at Gliedenberg, Dammer Berge, Germany (Fig. 8.12) is a clear illustration of how subglacial shearing of sediments may produce a laminated till and ultimately a massive diamicton within just 100 m. This process is similar to the one described by Hart and Boulton (1991). The Dammer Berge (Van der Wateren, 1987, 1995) are a thrust moraine formed during the Drenthe advance of the Saalian glaciation. They were overridden when the ice expanded to the Saalian limit, 100 km further...

Geomorphology and Sedimentology of Receding Svalbard Glaciers

Modern glaciers in Svalbard are invariably associated with large end-moraine complexes formed during the Neoglacial maximum in the late nineteenth or early twentieth century (Fig. 4.7). Some glaciers have receded 1 2 km from these complexes, leaving smaller moraine systems in the intervening zone. Some authors have referred to these moraine complexes as 'push moraines' (e.g. Croot, 1988a Hagen, 1987, 1988 Van der Wateren, 1995 Boulton et al., 1996, 1999) although not all Svalbard moraine...

Glacial Geology and Geomorphology

Some of the most impressive landforms produced at the margins of sub-polar glaciers of the Canadian and Greenland high arctic are thrust-block moraines or composite ridges (Fig. 3.5) (Kalin, 1971 Evans, 1989b Evans and England, 1991 Lemmen, et al. 1991 Lehmann, 1992). These landforms are constructed by proglacial glacitectonic disturbance of glacilacustrine, raised glacimarine or glacifluvial sediments on valley floors where the compressive stresses in the glacier snout are transmitted to...

The Continental Shelf System

12.1.1 Diamicton Formation on Continental Shelves The most widespread sediments on glaciated continental shelves (Fig. 12.1) are diamictons. There has been, and still is, much discussion on the origin of these diamictons. The correct Figure 12.1 World map showing continental margins that were glaciated once or several times during the Late Cenozoic. Figure 12.1 World map showing continental margins that were glaciated once or several times during the Late Cenozoic. interpretation of the...

Structural Style of Subglacial Shear Zones

Structures in the deforming bed are produced by progressive simple shear, disregarding relatively minor deviations from this ideal deformation model. This deformation history leads to a monoclinic symmetry in three dimensions (Passchier and Trouw, 1996). This shows in two-dimensional view (in the plane of shearing) as a typically asymmetric structural geometry, which is the most reliable indicator of tectonic movement and therefore ice movement direction. Structural styles of brittle and...

Geomorphological Criteria of Ice Stream Activity

Ice streams are discrete features within an ice sheet and so we may expect them to leave behind a unique suite of glacial landforms. By coupling the known characteristics of existing ice streams (outlined above) with traditional theories of glacial geomorphology, it is possible to predict several geomorphological products of palaeo-ice stream activity. While individual criteria are not Rose (1979) Shabtaie et al. (1987) Echelmeyer et al. (1994) Rose (1979) Shabtaie and Bentley (1987) Alley et...

The Continental Slope and Adjoining Deep Sea System

Bathymetry Moraine Continental Shelf

The main large-scale morphological elements on continental slopes are trough mouth fans, gullies and channels, and large submarine slide scars and corresponding accumulations (Fig. 12.8). Some gullies and channels may be formed directly in association with continental ice sheets (e.g. Vorren et al., 1998), but many of these and the slides do not. Thus, they will not be treated here. Here we will discuss the main glacigenic depo-centres on the continental slope, the trough mouth fans, and...

Sediment Transport Pathways

Picture Sediment Transport Paths

Transport routeways through valley glaciers are varied (Fig. 15.2). Boulton (1978) distinguished two main sediment transport pathways 1. active subglacial transport, and 2. passive supraglacial or englacial transport. Subglacial debris transport was termed active because sediment in the basal shear zone of glaciers is subjected to high inter-particle contact forces and consequently undergoes significant abrasion, fracture and comminution. Boulton (1978) argued that, in contrast, sediment in...

General Interpretation

The sequence outlined above reveals the following general trends 1. a north-to-south decrease in the importance of lateral meltwater erosion Figure 7.6 Low oblique aerial view of the Melville Moraine. The moraine has a gentle proximal and steep distal flank. It curves to the right into a valley where it has attached to it a gravel delta terrace marking relative sea level at time of formation, visible in the lower right corner with three snow banks on the delta riser. From the delta, the moraine...

Structural Glaciological Controls on Debris Entrainment and Transport

An understanding of structural glaciology and its role in controlling debris entrainment and transfer is essential to the interpretation of the landsystem developed at Svalbard glacier margins (Hambrey and Lawson, 2000). Debris entrainment in Svalbard glaciers takes place by a variety of mechanisms that can be linked to the evolution of ice structures (Hambrey et al., 1999). The most significant structures include stratification, folded stratification, foliation, the deformed basal ice zone,...

Landsystems of Glacial Deposition

Causses Preglacial Debris Flow

While clean and debris-covered glaciers show many similar features within their landsystems, they differ in the dominant processes operating at the ice margin and in the relative development of landforms (Figs 15.4 and 15.5). Figure. 15.4 A landsystem model for valley glaciers with relatively low supraglacial debris inputs. (From Benn and Evans, 1998). 1 Supraglacially entrained debris 2 Periglacial trimline above ice-scoured bedrock 3 Medial moraine 4 Fluted till surface 5 Paraglacial...

Ice Margins in High Relief Areas

The high-relief area that is described here is the McMurdo dry valleys, which are often called the McMurdo oasis. Glaciers of the McMurdo dry valleys can be divided into four groups outlet glaciers, ice shelves, piedmont glaciers and alpine glaciers. Ice from the East Antarctic ice sheet flows through the Transantarctic Mountains to form outlet glaciers, such as Ferrar and Mackay glaciers, which reach the coast and form small floating ice tongues. Other outlet glaciers, such as Taylor Glacier,...

Geomorphology and Sedimentology of Contemporary Surging Glaciers

Base Surge Deposit

This section provides details of the landform-sediment assemblages observed at contemporary surging glacier margins in Iceland, Svalbard, USA and Canada. Additionally, extensive reference is made to the 1982 83 surge of Variegated Glacier, Alaska, because it is the best documented and instrumented surge event. The time development of surging glacier geomorphology is best represented by the Icelandic examples due to the fact that the surges are historically documented by the local population...

Introduction and Rationale

The aim of this contribution is to describe the landform-sediment assemblages at the margins of polythermal glaciers in Svalbard and to present a landsystem model for terrestrially-based glaciers in this maritime high-arctic setting. The discussion is restricted principally to non-surge-type glaciers as the landform-sediment assemblages at surge-type glaciers are considered in a separate chapter (Evans and Rea, Chapter 11). The structural glaciological controls on landform development are...

Glacial Landsystems of the northern European Plains

The last section concluded that the palaeogeography and, more particularly, the distribution of ice-marginal drainage systems and ice-dammed lakes, is another strong controlling factor in the formation of thrust moraines. This section discusses three regions where these aspects combined in different ways with glacial dynamic influences. The first is an area in central Germany where the three Mid- and Late-Pleistocene glacial margins partly coincide in a small area on the north side of the...

Icemarginal Terrestrial Landsystems Active Temperate Glacier Margins

Temperate glacier margins are mainly wet-based for at least part of the year and are located in terrain that contains discontinuous or no permafrost. Such glaciers are considered as active when they are capable of forward momentum even during overall recession. This is manifest in the small winter readvances that characterize receding outlet glaciers in places like Iceland (e.g. Sharp, 1984 Boulton, 1986 Kr ger, 1995). Cold winter conditions result in the penetration of a seasonal cold wave...

Moraine Profiles

Englacial Moraines Diagram

Figure 15.9 The Batal Glacier in the Lahul Himalaya. A) View looking southwest at two large lateral moraines. B) Geomorphic map and profiles showing the main landform elements associated with this debris-covered glacier (Adapted after Benn & Owen, 2002). 15.5.2 Subglacial Sediments and Landforms Where valley glaciers carry relatively small amounts of supraglacial debris, subglacial landsystems may be well exposed on the depositional surface (Figs. 15.4 and 15.14). Indeed, the beds of former...

References

Classification and terminology of morainic landforms in Finland. Boreas, 6, 87-100. Aario, R., 1992. Puljo moraines and Sevetti moraines. In A.-M. Robertson, B. Ringberg, U. Miller and L. Brunnberg eds , Quaternary stratigraphy, glacial morphology and environmental changes. Sveriges Geologiska Unders kning, Series Ca 81, pp. 7-14. Aartolahti, T., 1974. Ring ridge hummocky moraines in northern Finland. Fennia, 134, 22. Aartolahti, T., 1975. Two glacial mound fields in northern...