Structure and rhythmic pattern of glaciofluvial deposits north of Lake Vänern, south-central Sweden

The glaciofluvial deposits of the Vanern plain, Värmland, form esker systems and trains. Esker trains are defined as series of short eskers, kames and other glaciofluvial deposits. Trains spreading fanlike from the same area are combined into esker systems. Some individual deposits are described. The general pattern differs from the long, coherent eskers typical of eastern Sweden. A rhythmic pattern of depositional units in the esker trains is found to correspond to a 10 to 11 yr cycle, possibly representing the sunspot cycle. Zones of alternating faster and slower retreat of the ice margin are identified. Two lines of slower retreat, the Karlstad and Fryken lines, correspond to the Norwegian Ski line, dated at 10 000 BP (conventional radiocarbon years) and to a slightly younger line. The spacing of the esker trains is controlled by topography in the north, but by basal ice melting, which controlled their flow and spacing on the Ratter terrain in the south.     

Subglacial drainage by groundwater-channel coupling,and the origin of esker systems: Part 1—glaciological observations

OverallThis work is presented in two parts. Part I presents observations on the coupling between subglacial channel flow and groundwater flow in determining subglacial hydraulic regime and creating eskers from an Icelandic glacier that is suggested as an analogue for many parts of Pleistocene ice sheets. Part II develops a theory of perennial subglacial stream flow and the origin of esker systems, and models the evolution of the subglacial stream system and associated groundwater flow in a glacier of the type described in Part I. It is suggested that groundwater flow may be the predominant mechanism whereby meltwater at the glacier bed finds its way to the major subglacial streams that discharge water to glacier margins.Part IBoreholes drilled through an Icelandic glacier into an underlying till and aquifer system have been used to measure variations in head in the vicinity of a perennial subglacial stream tunnel during late summer and early winter. They reveal a subglacial groundwater catchment that is drained by a subglacial stream along its axis. The stream tunnel is characterised by low water pressures, and acts as a drain for the groundwater catchment, so that groundwater flow is predominantly transverse to ice flow, towards the channel.These perennial streams flow both in summer and winter. Their portals have lain along the same axes for the 5 km of retreat that has occurred since the end of the Little Ice Age, 100 years ago, suggesting that the groundwater catchments have been relatively stable for at least this period. In the winter season, stream discharges are largely derived from basal melting, but during summer, water derived from the glacier surface finds its way, via fractures and moulins, to the glacier bed, where it dominates the meltwater flux. Additional subglacial streams are created in summer to help drain this greater flux from beneath the glacier, through poorly integrated and unstable networks. Summer streams cease to flow during winter and tend not to form in the same places in the following summer. Perennial streams are the stable component of the system and are the main sources of extensive esker systems.Strong flow of groundwater towards low-pressure areas along channels and the ice margin is a source of major upwelling that can produce sediment liquefaction and instability. A theory is developed to show how this could have a major effect on subglacial sedimentary processes.     

Deglaciation pattern indicated by the ice-margin formations in Northern Karelia, eastern Finland

A map has been reconstructed representing the large-scale glacial and glaciofluvial morphology of Northern Karelia and the adjacent area of Soviet Karelia. Observations have been made on the directions of glacial striae and on the distribution of sub-aquatic and supra-aquatic terrain in order to obtain a consistent picture of the course of deglaciation in the area and the factors affecting it. The map indicates that the behaviour of the glacier during the deglaciation was largely governed by the distribution of sub-aquatic and supra-aquatic areas. The marginal zone of the ice sheet was divided into two large lobes in this area. The Finnish Lake District Lobe terminated mostly in water, giving rise to massive glaciofluvial accumulations, while the North Karelian Lobe flowed on the land above the highest shore levels, pushing up several more or less discontinuous narrow end-moraine ridges. Relatively large glaciofluvial deposits were also formed in the supra-aquatic area in places where the ice margin terminated in a local ice-dammed lake. It is evident that the Salpausselkä I and II end-moraines extend as continuous formations only to the zone where the former ice margin rose onto dry land during the deglaciation phase. The spatial and temporal differences in the glacial dynamics and differing depositional environments gave rise to the complex glacial morphology of Northern Karelia.     

Neoglacial (<3000 years) till and flutes at Saskatchewan Glacier,Canadian Rocky Mountains,formed by subglacial deformation of a soft bed

Understanding the processes that deposit till below modern glaciers provides fundamental information for interpreting ancient subglacial deposits. A process‐deposit‐landform model is developed for the till bed of Saskatchewan Glacier in the Canadian Rocky Mountains. The glacier is predominantly hard bedded in its upper reaches and flows through a deep valley carved into resistant Palaeozoic carbonates but the ice margin rests on a thick (<6 m) soft bed of silt‐rich deformation till that has been exposed as the glacier retreats from its Little Ice Age limit reached in 1854. In situ tree stumps rooted in a palaeosol under the till are dated between ca 2900 and 2700 yr bp and record initial glacier expansion during the Neoglacial. Sedimentological and stratigraphic observations underscore the importance of subglacial deformation of glaciofluvial outwash deposited in front of the advancing glacier and mixing with glaciolacustrine carbonate‐rich silt to form a soft bed. The exposed till plain has a rolling drumlinoid topography inherited from overridden end moraines and is corrugated by more than 400 longitudinal flute ridges which record deformation of the soft bed and fall into three genetically related types: those developed in propagating incipient cavities in the lee of large subglacial boulders embedded in deformation till, and those lacking any originating boulder and formed by pressing of wet till up into radial crevasses under stagnant ice. A third type consists of U‐shaped flutes akin to barchan dunes; these wrap around large boulders at the downglacier ends of longitudinal scours formed by the bulldozing of boulders by the ice front during brief winter readvances across soft till. Pervasive subglacial deformation during glacier expansion was probably facilitated by large boulders rotating within the soft bed (‘glacioturbation’).     

Sedimentary facies and landform genesis at a temperate outlet glacier: Soler Glacier, North Patagonian Icefield

This paper focuses on the structural glaciology, dynamics, debris transport paths and sedimentology of the forefield of Soler Glacier, a temperate outlet glacier of the North Patagonian Icefield in southern Chile. The glacier is fed by an icefall from the icefield and by snow and ice avalanches from surrounding mountain slopes. The dominant structures in the glacier are ogives, crevasses and crevasse traces. Thrusts and recumbent folds are developed where the glacier encounters a reverse slope, elevating basal and englacial material to the ice surface. Other debris sources for the glacier include avalanche and rockfall material, some of which is ingested in marginal crevasses. Debris incorporated in the ice and on its surface controls both the distribution of sedimentary facies on the forefield and moraine ridge morphology. Lithofacies in moraine ridges on the glacier forefield include large isolated boulders, diamictons, gravel, sand and fine-grained facies. In relative abundance terms, the dominant lithofacies and their interpretation are sandy boulder gravel (ice-marginal), sandy gravel (glaciofluvial), angular gravel (supraglacial) and diamicton (basal glacial). Proglacial water bodies are currently developing between the receding glacier and its frontal and lateral moraines. The presence of folded sand and laminites in moraine ridges in front of the glacier suggests that, during a previous advance, Soler Glacier over-rode a former proglacial lake, reworking lacustrine deposits. Post-depositional modification of the landform/sediment assemblage includes melting of the ice-core beneath the sediment cover, redistribution of finer material across the proglacial area by aeolian processes and fluvial reworking. Overall, the preservation potential of this landform/sediment assemblage is high on the centennial to millennial timescale.     

Interlobate esker architecture and related hydrogeological features derived from a combination of high-resolution reflection seismics and refraction tomography,Virttaankangas, southwest Finland

A novel high-resolution (2–4 m source and receiver spacing) reflection and refraction seismic survey was carried out for aquifer characterization and to confirm the existing depositional model of the interlobate esker of Virttaankangas, which is part of the Säkylänharju-Virttaankangas glaciofluvial esker-chain complex in southwest Finland. The interlobate esker complex hosting the managed aquifer recharge (MAR) plant is the source of the entire water supply for the city of Turku and its surrounding municipalities. An accurate delineation of the aquifer is therefore critical for long-term MAR planning and sustainable use of the esker resources. Moreover, an additional target was to resolve the poorly known stratigraphy of the 70–100-m-thick glacial deposits overlying a zone of fractured bedrock. Bedrock surface as well as fracture zones were confirmed through combined reflection seismic and refraction tomography results and further validated against existing borehole information. The high-resolution seismic data proved successful in accurately delineating the esker cores and revealing complex stratigraphy from fan lobes to kettle holes, providing valuable information for potential new pumping wells. This study illustrates the potential of geophysical methods for fast and cost-effective esker studies, in particular the digital-based landstreamer and its combination with geophone-based wireless recorders, where the cover sediments are reasonably thick.

     

Sediment‐rich meltwater plumes and ice‐proximal fans at the margins of modern and ancient tidewater glaciers: Observations and modelling

Turbid meltwater plumes and ice‐proximal fans occur where subglacial streams reach the grounded marine margins of modern and ancient tidewater glaciers. However, the spacing and temporal stability of these subglacial channels is poorly understood. This has significant implications for understanding the geometry and distribution of Quaternary and ancient ice‐proximal fans that can form important aquifers and hydrocarbon reservoirs. Remote‐sensing and numerical‐modelling techniques are applied to the 200 km long marine margin of a Svalbard ice cap, Austfonna, to quantify turbid meltwater‐plume distribution and predict its temporal stability. Results are combined with observations from geophysical data close to the modern ice front to refine existing depositional models for ice‐proximal fans. Plumes are spaced ca 3 km apart and their distribution along the ice front is stable over decades. Numerical modelling also predicts the drainage pattern and meltwater discharge beneath the ice cap; modelled water‐routing patterns are in reasonable agreement with satellite‐mapped plume locations. However, glacial retreat of several kilometres over the past 40 years has limited build‐up of significant ice‐proximal fans. A single fan and moraine ridge is noted from marine‐geophysical surveys. Closer to the ice front there are smaller recessional moraines and polygonal sediment lobes but no identifiable fans. Schematic models of ice‐proximal deposits represent varying glacier‐terminus stability: (i) stable terminus where meltwater sedimentation produces an ice‐proximal fan; (ii) quasi‐stable terminus, where glacier readvance pushes or thrusts up ice‐proximal deposits into a morainal bank; and (iii) retreating terminus, with short still‐stands, allowing only small sediment lobes to build up at melt‐stream portals. These modern investigations are complemented with outcrop and subsurface observations and numerical modelling of an ancient, Ordovician glacial system. Thick turbidite successions and large fans in the Late Ordovician suggest either high‐magnitude events or sustained high discharge, consistent with a relatively mild palaeo‐glacial setting for the former North African ice sheet.     

Moraine development at a small High‐Arctic valley glacier: Rieperbreen,Svalbard

Ice‐cored lateral and frontal moraine complexes, formed at the margin of the small, land‐based Rieperbreen glacier, central Svalbard, have been investigated through field observations and interpretations of aerial photographs (1936, 1961 and 1990). The main focus has been on the stratigraphical and dynamic development of these moraines as well as the disintegration processes. The glacier has been wasting down since the ‘Little Ice Age’ (LIA) maximum, and between 1936 and 1990 the glacier surface was lowered by 50–60 m and the front retreated by approximately 900 m. As the glacier wasted, three moraine ridges developed at the front, mainly as melting out of sediments from debris‐rich foliation and debris‐bands formed when the glacier was polythermal, probably during the LIA maximum. The disintegration of the moraines is dominated by wastage of buried ice, sediment gravity‐flows, meltwater activity and some frost weathering. A transverse glacier profile with a northward sloping surface has developed owing to the higher insolation along the south‐facing ice margin. This asymmetric geometry also strongly affects the supraglacial drainage pattern. Lateral moraines have formed along both sides of the glacier, although the insolation aspect of the glacier has resulted in the development of a moraine 60 m high along its northern margin. Copyright © 2001 John Wiley & Sons, Ltd.     

On the sensitivity of Holocene talus-derived rock glaciers to climate change in the Ben Ohau Range,New Zealand

The morphology and surface ages of talus-derived rock glaciers are investigated to establish the timing of rock glacier formation in the central Southern Alps. Samples of rock weathering rinds show that all rock glaciers studied were formed during the Neoglacial period, but differences exist between sites in the number of new rock glacier lobes formed by Holocene climatic fluctuations. A qualitative conceptual model is proposed to explain rock glacier formation in terms of two thresholds. An external threshold relates to the presence of a cool climate capable of allowing internal ice to form within talus slopes. An internal threshold relates to the presence of sufficiently thick talus at a site to generate a shear stress capable of overcoming internal friction within the talus/ice mass. The model produces a non-steady-state response to explain why unmodified talus, single-lobed and double-lobed rock glaciers developed at adjacent sites under the same climatic regime. Individual landforms have different sensitivities to formation, which depend partly on the previous history of talus accumulation and rock glacier activity at a site. The model demonstrates how successive cool climate periods may be fully represented by rock glacier lobes at sensitive sites but under-represented at insensitive sites. Sensitivity (and therefore climatic representativeness) is favoured by high rates of debris supply. By implication, the timing of formation of rock glacier lobes in regions of prolonged cool climate and low debris production is less likely to correspond to the timing of climatic cooling and more likely to follow the ‘rules’ of deterministic chaos.     

Formation and disintegration of a high-arctic ice-cored moraine complex, Scott Turnerbreen, Svalbard

Englacial debris structures, morphology and sediment distribution at the frontal part and at the proglacial area of the Scott Turnerbreen glacier have been studied through fieldwork and aerial photograph interpretation. The main emphasis has been on processes controlling the morphological development of the proglacial area. Three types of supraglacial ridges have been related to different types of englacial debris bands. We suggest that the sediments were transported in thrusts, along flow lines and in englacial meltwater channels prior to, and during a surge in, the 1930s, before the glacier turned cold. Melting-out of englacial debris and debris that flows down the glacier front has formed an isolating debris cover on the glacier surface, preventing further melting. As the glacier wasted, the stagnant, debris-covered front became separated from the glacier and formed icecored moraine ridges. Three moraine ridges were formed outside the present ice-front. The further glacier wastage formed a low-relief proglacial area with debris-flow deposits resting directly on glacier ice. Melting of this buried ice initiated a second phase of slides and debris flows with a flow direction independent of the present glacier surface. The rapid disintegration of the proglacial morphology is mainly caused by slides and stream erosion that uncover buried ice and often cause sediments to be transported into the main river and out of the proglacial area. Inactive stream channels are probably one of the morphological elements that have the best potential for preservation in a wasting ice-cored moraine complex and may indicate former ice-front positions.     

The ice lobes of the Scandinavian ice sheet during the deglaciation in Finland.

On the basis of glacial landforms interpreted by means of Landsat satellite imagery and ice-flow data obtained by other methods, the Scandinavian ice sheet has been observed to have divided at the deglaciation stage into several ice lobes. The ice lobes were more active parts of the uniform ice sheet. They represent parts that had bordered on each other in different directions or on more passive portions of the ice. The reasons for the appearance of separate ice lobes were evidently the Fennoscandian topography, the location of accumulation areas, and regional differences in the amounts of ice generated. In the boundary zones of the different ice lobes, there occur exceptionally large glaciofluvial forms and moraines (interlobate complexes). An area of passive ice was often between ice lobes, and in such areas there occur no noteworthy eskers, marginal formations or streamlined forms. In the part of Finland located on the southern side of the Arctic Circle, six different ice lobes and four major areas of passive ice are interpreted to have existed.     

Cordilleran Ice Sheet lobal interactions and glaciotectonic superposition through stadial maxima along a mountain front in southwestern British Columbia, Canada

Glaciotectonic structures in subglacial till and substrate, as well as stone fabric, provenance and surface features in till, indicate that complex interactions of late Wisconsinan glacial lobes occurred along a mountain front in the western Fraser Lowland of southwestern British Columbia. Tills of this study represent subglacial deposition through the maxima of two stades in the Fraser Glaciation, the Coquitlam and the Vashon. Through each stadial maximum, temperate glacial ice was grounded and commonly overrode proglacial outwash while superimposing deformations in subglacial till during three phases: (1) pre-maximum glacier flow down valleys and into lowland piedmont ice, (2) coalescent piedmont ice during stadial maxima when flow was westward along the mountain front and across valley mouths, and (3) post-maximum glacier flow down valleys into lowland piedmont ice but prior to general deglaciation. Valley glaciers appear to have shifted flow directions during phases 1 and 3. During stadial maxima (phase 2), Fraser Lowland piedmont ice may have been part of an outlet glacier-ice stream complex that terminated in salt water over the continental shelf.     

Subglacial drainage by groundwater–channel coupling,and the origin of esker systems: part II—theory and simulation of a modern system

The observations from Breidamerkurjökull reported in Part I are used as a basis for a theory of coupled channel/groundwater flow that suggests that the large scale geometry of the hydraulic system self-organises as a consequence of coupling between groundwater and channel flow. The pattern of channel/esker distribution is largely determined by winter conditions and the sedimentary characteristics of eskers are largely determined by summer conditions, when large discharges of surface meltwater penetrate to the bed in the terminal zone. A simulation model is developed to explore evolution of the channel/groundwater system during a period of glacier growth. It suggests that as the glacier grows, channel/esker frequencies will increase as will the proportion of the melt flux discharged by channel flow, that groundwater impacts can extend to depth, that low water-pressure bulbs will extend downwards beneath channels, that groundwater upwelling towards channels are strong enough to create widespread conditions for liquefaction and that pressure shocks can occur as the channel system reorganises itself.     

Recent,very rapid retreat of a temperate glacier in SE Iceland

Iceland's glaciers are particularly sensitive to climate change, and their margins respond to trends in air temperature. Most Icelandic glaciers have been in retreat since c. 1990, and almost all since 1995. Using ice‐front measurements, photographic and geomorphological evidence, we examined the record of ice‐front fluctuations of Virkisjökull–Falljökull, a steep high‐mass‐turnover outlet glacier in maritime SE Iceland, in order to place recent changes in a longer‐term (80‐year) context. Detailed geomorphological mapping identifies two suites of annual push moraines: one suite formed between c. 1935 and 1945, supported by lichenometric dating; the other between 1990 and 2004. Using moraine spacing as a proxy for ice‐front retreat rates, we show that average retreat rates during the 1930s and 1940s (28 m a^?1) were twice as high as during the period from 1990 to 2004 (14 m a^?1). Furthermore, we show that both suites of annual moraines are associated with above‐average summer temperatures. Since 2005, however, retreat rates have increased considerably – averaging 35 m a^?1 – with the last 5 years representing the greatest amount of ice‐front retreat (～190 m) in any 5‐year period since measurements began in 1932. We propose that this recent, rapid, ice‐front retreat and thinning in a decade of unusually warm summers has resulted in a glaciological threshold being breached, with subsequent large‐scale stagnation of the glacier terminus (i.e. no forward movement) and the cessation of annual push‐moraine formation. Breaching this threshold has, we suggest, caused further very rapid non‐uniform retreat and downwasting since 2005 via a system feedback between surface melting, glacier thinning, decreased driving stress and decreased forward motion.     

Origin of Pleistocene outwash plains in various topographic settings, southern Poland

The style of Pleistocene outwash sedimentation in the foreland of the central European Mountains (the Carpathians and Sudetes) was controlled to a large extent by the topography. The deposits of three outwash plains formed in various morphological situations in front of the Upper Odra Lobe during the Odranian glaciation (older Saalian) are described here to show the conditions of their development and to reveal the relation between outwash plain sedimentology and proglacial topography. One outwash plain was formed between the mountain front and the ice-sheet margin, which advanced into the zone of fore-mountain alluvial fans. This outwash, deposited parallel to the ice margin, was under the considerable influence of extraglacial rivers flowing from the mountains. The second outwash was deposited in a small valley dipping away from the ice sheet and successively buried by glaciofluvial sediments. It evolved from a narrow valley sandur to an unconfined outwash plain. The third one was formed in a relatively broad, dammed valley dipping towards the ice sheet, where proglacial lake base level controlled the pattern of outwash channels as well as the character of the sedimentation. The studied outwash plains have different sedimentary successions. Their sedimentary profiles differ from each other even in the neighbouring valleys, indicating that distinct depositional conditions existed at the same time in closely spaced areas. It is suggested that the glaciomarginal deposition was controlled mostly by the orientation of the valleys and the inter-valley areas relative to the ice-sheet front. Size and morphology of valleys and interfluves were also important. Depending on their orientation, the outwash plains were fed by meltwaters in various ways; the dip of their surfaces was markedly different and the dynamics of the proglacial river systems were diverse.     

New evidence of the total glaciation of the Isla Grande de Tierra Del Fuego

The stratigraphy and preliminary interpretation of a new locality with glacial deposits in a previously interpreted ice-free area in Tierra del Fuego are presented. These deposits consist of basal proglacial gravels (at least 4–5 m thick) covered by the Drift Cabo Campo del Medio. The drift consists of a lower, 2 m thick, lodgment till and a upper, 7 m thick, glaciotectonized composite till, reflecting basal glacier shearing and upthrusting of glaciofluvial deposits and lodgment till, with superimposed deformation by gelifluction. These two main drift packages are interpreted as ground moraines, reflecting two corresponding glacial advances with an intervening recess of the glacier front. The altitude of the Drift Campo del Medio, well above younger fluvioglacial deposits related to the Last Glaciation, the degree of erosional modifications, and its external position, to the NE of the Last Glaciation moraine system, are evidence suggesting that the Drift Cabo Campo del Medio was related to a glaciation older than the Penultimate Glaciation. The finding of this locality sheds new light on the old controversy of total vs partial ice coverage of the island.     

Variations in esker morphology and internal architecture record time-transgressive deposition during ice margin retreat in Northern Ireland

The architecture and evolution of the subglacial hydrological system plays a key role in modulating ice flow. Eskers provide an opportunity to understand subglacial hydrology at a broader perspective than contemporary studies. Recent research has established a morphogenetic classification for eskers, but these studies have been limited to topographically simple regions of a single ice sheet. We present an updated map of esker distribution in Northern Ireland based on 5-m resolution elevation data. We also present a high-resolution map of the glacial geomorphology of SW Northern Ireland, based on ~ 0.4-m resolution elevation data. Ground Penetrating Radar data from four sites along the > 20-km long Evishanoran Esker system in central Northern Ireland are combined with geomorphological observations to provide insight into depositional processes and controls on esker formation. Esker architecture indicates two styles of deposition, including an initial high energy flow event in a subglacial conduit and delta foreset deposition close to the ice sheet margin during ice margin retreat. These delta foreset deposits can be used to reconstruct former ice margins. We identify that local topographic complexity and geological structures (e.g., faults) are important controls on esker formation. The broad-scale esker architecture remains the same despite variable esker planform morphology, suggesting hydrological conditions alone cannot explain esker morphology. This study provides further evidence that morphogenetic relationships cannot be based solely on remote sensing data and must be supported by robust field observations, especially where post-glacial processes may distort esker morphology (e.g., peat infilling).     

Formation of De Geer moraines and implications for deglaciation dynamics

De Geer moraines are very common in the Møre area, western Norway. These moraines occur below the marine limit and outside the Younger Dryas ice limit and occupy tributaries that connect the main fjords through the mountain passes. During deglaciation, ice in these tributaries flowed to the major ice streams. Sections across three De Geer moraines show that the ridges are composed of diamictons and fine-grained sediment, partly in stacked sequences. The diamicton units are interpreted as being composed of water-lain tills, lodgements tills and subaqueous flow deposits. The fine-grained sediment is though to have formed in a proglacial marine environment. Clast fabric of diamictons and deformation structures in underlying sands show that depositional directions for diamicton units and the direction of deformation for the sands is perpendicular to the ridge crests. Mainly based on this evidence, the ridges are thought to have formed by push at the glacier grounding line. The formation of transverse ridges (relative to ice flow) do occur in basal crevasses on modern glaciers, as do swarms of ridges along the front of retreating glaciers. The first mechanism of deposition does not seem to explain the ridges studied in the present paper and hence the importance of this process in the formation of De Geer moraines is questioned. The De Geer moraines were deposited by ice lobes advancing from one main fjord into another; therefore by studying the drainage pattern of the tributary lobes and their sequence of deglaciation, many features of the style of deglaciation of the ice sheet across the area can be determined. The northwestern part of the area was deglaciated earliest. After that, deglaciation proceeded to the southwest parallel to the coast. Subsequently the outer and the central part of Romsdalsfjorden were deglaciated causing ice to drain towards this fjord from both the north and south. The last fjord to be deglaciated was Storfjorden in the south.     

The Brampton kame belt and Pennine escarpment meltwater channel system (Cumbria, UK): Morphology, sedimentology and formation

The Brampton kame belt represents one of the largest glaciofluvial complexes within the UK. It is composed of an array of landform-sediment assemblages, associated with a suite of meltwater channels and situated within a palimpsest landscape of glacial features in the heart of one of the most dynamic parts of the British-Irish Ice Sheet. Glacial geomorphological mapping and sedimentological analysis have allowed a detailed reconstruction of both the morphological features and the temporal evolution of the Brampton kame belt, with processes informed by analogues from modern ice margins. The kame belt demonstrates the development of a complex glacier karst typified by the evolution of subglacial meltwater tunnels into an englacial and supraglacial meltwater system dominated by ice-walled lakes and migrating ice-contact drainage networks. Topographic inversion led to the extensive reworking of sediments, with vertical collapse and debris flows causing partial disintegration of the morphology. The resultant landform comprises a series of kettle holes, discontinuous ridges and flat-topped hills. The Pennine escarpment meltwater network, which fed the Brampton kame belt, is composed of an anastomosing subglacial channel system and flights of lateral channels. The Brampton kame belt is envisaged to have formed during the stagnation of ice in the lee of the Pennines as ice retreated westwards into the Solway Lowlands. The formation of the Brampton kame belt also has particular conceptual resonance in terms of constraining the nature of kame genesis, whereby an evolving glacier karst is a key mechanism in the spatial and temporal development of ice-contact sediment-landform associations.     

Drainage beneath ice sheets: groundwater–channel coupling,and the origin of esker systems from former ice sheets

The nature of the drainage system beneath ice sheets is crucial to their dynamic behaviour but remains problematic. An experimentally based theory of coupling between groundwater and major channel systems is applied to the esker systems in the area occupied the last ice sheet in Europe, which we regard as a fossil imprint of major longitudinal drainage channels. We conclude that the large-scale distribution and spacing of major eskers is consistent with the theory of groundwater control, in which esker spacing is partly controlled by the transmissivity of the bed.It is concluded that esker patterns reflect the large-scale organisation of the subglacial drainage pattern in which channel development is coupled to groundwater flow and to the ice sheet's dynamic regime. The theory is then used to deduce: basal meltwater recharge rates and their spatial variability from esker spacing in an area in which the ice sheet was actively streaming during its final retreat; patterns of palaeo-groundwater flow and head distribution; and the seasonally varying magnitude of discharge from stream tunnels at the retreating ice sheet margin. Major channel/esker systems appear to have been stable at least over several hundred of years during the retreat of the ice sheet, although major dynamic events are demonstrably associated with major shifts in the hydraulic regime.Modelling suggests: that glaciation can stimulate deep groundwater circulation cells that are spatially linked to channel locations, with groundwater flow predominantly transverse to ice flow; that the circulation pattern has the potential to create large-scale anomalies in groundwater chemistry; and that the spacing of channels will change through the glacial cycle, influencing water pressures in stream tunnels, subglacial hydraulic gradients and effective pressure. If the latter is reduced sufficiently, it could trigger enhanced bed deformation, thus coupling drainage to ice sheet movement. It suggests the possibility of distinctive phases of sediment deformation and drumlin mobilisation during a glacial cycle.