Meltwater Channels Research Articles

Revision of the NW Laurentide Ice Sheet: implications for paleoclimate, the northeast extremity of Beringia, and Arctic Ocean sedimentation

For the past half-century, reconstructions of North American ice cover during the Last Glacial Maximum have shown ice-free land distal to the Laurentide Ice Sheet, primarily on Melville and Banks islands in the western Canadian Arctic Archipelago. Both islands reputedly preserve at the surface multiple Laurentide till sheets, together with associated marine and lacustrine deposits, recording as many as three pre-Late Wisconsinan glaciations. The northwest corner of Banks Island was purportedly never glaciated and is trimmed by the oldest and most extensive glaciation (Banks Glaciation) considered to be of Matuyama age (>780 ka BP). Inside the limit of Banks Glaciation, younger till sheets are ascribed to the Thomsen Glaciation (pre-Sangamonian) and the Amundsen Glaciation (Early Wisconsinan Stade). The view that the western Canadian Arctic Archipelago remained largely ice-free during the Late Wisconsinan is reinforced by a recent report of two woolly mammoth fragments collected on Banks and Melville islands, both dated to ∼22 ka BP. These dates imply that these islands constitute the northeast extremity of Beringia. A fundamental revision of this model is now warranted based on widespread fieldwork across the adjacent coastlines of Banks and Melville islands, including new dating of glacial and marine landforms and sediments. On Dundas Peninsula, southern Melville Island, AMS 14C dates on ice-transported marine molluscs within the most extensive Laurentide till yield ages of 25–49 ka BP. These dates require that Late Wisconsinan ice advanced northwestward from Visount Melville Sound, excavating fauna spanning Marine Isotope Stage 3. Laurentide ice that crossed Dundas Peninsula (300 m asl) coalesced with Melville Island ice occupying Liddon Gulf. Coalescent Laurentide and Melville ice continued to advance westward through M'Clure Strait depositing granite erratics at ≥235 m asl that require grounded ice in M'Clure Strait, as do streamlined bedforms on the channel floor. Deglaciation is recorded by widespread meltwater channels that show both the initial separation of Laurentide and Melvile ice, and the successive retreat of Laurentide ice southward across Dundas Peninsula into Viscount Melville Sound. Sedimentation from these channels deposited deltas marking deglacial marine limit. Forty dates on shells collected from associated glaciomarine rhythmites record near-synchronous ice retreat from M'Clure Strait and Dundas Peninsula to north-central Victoria Island ∼11.5 ka BP. Along the adjacent coast of Banks Island, deglacial shorelines also record the retreat of Laurentide ice both eastward through M'Clure Strait and southward into the island's interior. The elevation and age (∼11.5 ka BP) of deglacial marine limit there is fully compatible with the record of ice retreat on Melville Island. The last retreat of ice from Mercy Bay (northern Banks Island), previously assigned to northward retreat into M'Clure Strait during the Early Wisconsinan, is contradicted by geomorphic evidence for southward retreat into the island's interior during the Late Wisconsinan. This revision of the pattern and age of ice retreat across northern Banks Island results in a significant simplification of the previous Quaternary model. Our observations support the amalgamation of multiple till sheets – previously assigned to at least three pre-Late Wisconsinan glaciations – into the Late Wisconsinan. This revision also removes their formally named marine transgressions and proglacial lakes for which evidence is lacking. Erratics were also widely observed armouring meltwater channels originating on the previously proposed never-glaciated landscape. An extensive Late Wisconsinan Laurentide Ice Sheet across the western Canadian Arctic is compatible with similar evidence for extensive Laurentide ice entering the Richardson Mountains (Yukon) farther south and with the Innuitian Ice Sheet to the north. Widespread Late Wisconsinan ice, in a region previously thought to be too arid to sustain it, has important implications for paleoclimate, ice sheet modelling, Arctic Ocean ice and sediment delivery, and clarifying the northeast limit of Beringia.

Origin and significance of lateral meltwater channels formed along a temperate glacier margin, Glacier Bay, Alaska

Pleistocene lateral meltwater channels are commonly used as evidence of cold‐based or polythermal ice. However, lateral meltwater channel formation has been observed for >40 years along the margins of a rapidly thinning temperate glacier in Glacier Bay, Alaska. Flights of nested linear lateral meltwater channels and in‐and‐out channels have formed on the sides of emerging nunataks. Nested channels at Burroughs Glacier are up to 200 m long; they are good proxies for the slope of the ice margin along the land surface and are terminated by subglacial chutes. A perched water table associated with precipitation and high ablation rates in the temperate ice causes surface meltwater to flow toward the margin above less permeable ice. The water flows along the margin and erodes lateral meltwater channels until a subglacial chute carries the water into the subglacial water system. Rates of channel formation range from 0 to 8 channels/year. Spacing and rates of channel formation are controlled by the land‐surface slope, ablation rate, erodibility of the substrate and stream discharge. Because lateral meltwater channels have been observed forming along a temperate glacier margin, care must be exercised when using the presence of lateral meltwater channels as definitive evidence of cold‐based or polythermal ice.

The sediment infill of subglacial meltwater channels on the West Antarctic continental shelf

Subglacial meltwater plays a significant yet poorly understood role in the dynamics of the Antarctic ice sheets. Here we present new swath bathymetry from the western Amundsen Sea Embayment, West Antarctica, showing meltwater channels eroded into acoustic basement. Their morphological characteristics and size are consistent with incision by subglacial meltwater. To understand how and when these channels formed we have investigated the infill of three channels. Diamictons deposited beneath or proximal to an expanded grounded West Antarctic Ice Sheet are present in two of the channels and these are overlain by glaciomarine sediments deposited after deglaciation. The sediment core from the third channel recovered a turbidite sequence also deposited after the last deglaciation. The presence of deformation till at one core site and the absence of typical meltwater deposits (e.g., sorted sands and gravels) in all three cores suggest that channel incision pre-dates overriding by fast flowing grounded ice during the last glacial period. Given the overall scale of the channels and their incision into bedrock, it is likely that the channels formed over multiple glaciations, possibly since the Miocene, and have been reoccupied on several occasions. This also implies that the channels have survived numerous advances and retreats of grounded ice.

A geomorphological overview of glacial landforms on the Icelandic continental shelf

Please click here to download the map associated with this article. The availability of a bathymetric database that covers about 80% of the Icelandic shelf has made it possible to produce a geomorphological map of the glacial landforms. The digital elevation model of the bathymetry was analyzed as a series of shaded relief images. Trough edges, bulging trough mouths, moraines, eskers, melt water channels, streamlined bedrock and streamlined drift, mostly hitherto unmapped, distributed all around the island have been identified. Moraines are found on the shelf, within troughs and inside fjords. Streamlined landforms are always confined to the bottom of troughs. Troughs appear to have been cut by ice streams draining an ice sheet that likely covered the entire shelf. At the shelf break, most troughs terminate with contours that bulge in a convex-outwards fashion. This suggests that an ice stream eroded, transported and finally deposited large amounts of sediment at the trough mouth. Overall, the glacial morphology of the shelf highlights a radial pattern that indicates a main ice divide near the centre of Iceland.

Using multi-beam RADARSAT-1 imagery to augment mapping surficial geology in northwest Alberta, Canada

This paper evaluates the applicability of multi-beam RADARSAT-1 satellite imagery for mapping surficial sediments in northwest Alberta, Canada, using simple arithmetic algorithms. The goal is to make the RADARSAT-1 imagery acquired by the Alberta Geological Survey (AGS) usable to common users who have no access to complex image classification software and (or) expertise. Unlike the Canadian Shield, northern Alberta is mantled with much thicker glacial deposits that are covered by the Northern Boreal Forest. This limits the use of conventional image classification techniques, as there is not a one-to-one relationship between vegetation and the underlying surficial sediments. The RADARSAT-1 data utilized consists of RADARSAT-1 imagery acquired using Standard Beam 1 and 7 in both ascending and descending passes. Moisture and surface roughness information can be extracted by applying algorithms that calculate the differences between images acquired from different incidence angles and look directions (ascending versus descending looks). The image created using different incidence angles highlights flat surfaces, including wetlands, agricultural areas, and forest fire scars. The image generated using opposing look directions enhances geomorphologic features, including ice flow features, meltwater channels, till hummocks, and sand dune ridges. In addition, the enhanced RADARSAT-1 imagery (includes integration of topographic information provided by a digital elevation model (DEM)) provides an additional level of confidence to the air photo interpretation conducted in regions with little or no ground access and also provides a regional perspective on large-scale subtle surface morphological elements (e.g., ice flow patterns) that might be overlooked in individual aerial photographs.

Seafloor glacial features reveal the extent and decay of the last British Ice Sheet, east of Scotland

AbstractThree‐dimensional (3D) seismic datasets, 2D seismic reflection profiles and shallow cores provide insights into the geometry and composition of glacial features on the continental shelf, offshore eastern Scotland (58° N, 1–2° W). The relic features are related to the activity of the last British Ice Sheet (BIS) in the Outer Moray Firth. A landsystem assemblage consisting of four types of subglacial and ice marginal morphology is mapped at the seafloor. The assemblage comprises: (i) large seabed banks (interpreted as end moraines), coeval with the Bosies Bank moraine; (ii) morainic ridges (hummocky, push and end moraine) formed beneath, and at the margins of the ice sheet; (iii) an incised valley (a subglacial meltwater channel), recording meltwater drainage beneath former ice sheets; and (iv) elongate ridges and grooves (subglacial bedforms) overprinted by transverse ridges (grounding line moraines). The bedforms suggest that fast‐flowing grounded ice advanced eastward of the previously proposed terminus of the offshore Late Weichselian BIS, increasing the size and extent of the ice sheet beyond traditional limits. Complex moraine formation at the margins of less active ice characterised subsequent retreat, with periodic stillstands and readvances. Observations are consistent with interpretations of a dynamic and oscillating ice margin during BIS deglaciation, and with an extensive ice sheet in the North Sea basin at the Last Glacial Maximum. Final ice margin retreat was rapid, manifested in stagnant ice topography, which aided preservation of the landsystem record. Copyright © 2008 John Wiley & Sons, Ltd.

Early pliocene expansion of the east antarctic ice sheet, upper wright valley, antarctica

.Whereas the glacial geomorphology of lower and central Wright Valley is reasonably well understood, the upper valley region, including the North and South Forks and the Dais, has received little attention. Our studies suggest that a wet‐based glacier overrode the area and deposited what has been mapped elsewhere as the Peleus till. While we did not observe this silt‐rich till in the Labyrinth, it occurs on the Dais and in protected areas of the North and South Forks. Most importantly, our findings imply that the Wright Upper Glacier, an outlet glacier of the East Antarctic Ice Sheet, deposited lateral moraines and lateral‐moraine segments along the north and south walls of both the North and South Forks following deposition of the Peleus till. We argue that this drift is correlative with Taylor IVa drift in central Taylor Valley and Alpine III drift in central Wright Valley, based on landscape features, surface‐boulder weathering, soil development, and stratigraphy. The presence of meltwater channels, outwash, kame moraines, esker‐like features, and kames suggests that ice‐marginal or supraglacial water may have accompanied this glaciation.

Landform assemblages produced by the Laurentide Ice Sheet in northeastern British Columbia and adjacent Northwest Territories — constraints on glacial lakes and patterns of ice retreatThis article is one of a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.

The Laurentide Ice Sheet reached the Canadian Cordillera during the last glacial maximum in northeastern British Columbia and adjacent Northwest Territories and all regional drainage to unglaciated areas in the north was dammed by the ice. Converging ice-flow patterns near the mountain front suggest that the Laurentide Ice Sheet likely coalesced with the Cordilleran Ice Sheet during the last glaciation. With deglaciation, the ice masses separated, but earlier ice retreat in the south meant that meltwater pooled between the mountain front and the Laurentide margin. The level of the flooding was controlled by persistent ice cover on the southern Franklin Mountains. Glacial Lake Liard formed when the Laurentide Ice Sheet retreated east of the southern Liard Range and, at its maximum extent, may have impounded water at least as far south as the Fort Nelson River. Deglaciation of the plains was marked by local variations in ice flow caused by a thin ice sheet becoming more affected by the topography and forming lobes in places. These lobes caused diversions in local drainage readily traced by abandoned meltwater channels. Radiocarbon ages from adjacent areas suggest the relative chronology of deglaciation presented here occurred between 13 and 11 ka BP.

Quaternary geology of part of the Kale Water catchment, Western Cheviot Hills, southern Scotland

Synopsis This study reports on a survey of the middle part of the Kale Water, one of the western Cheviot catchments. Field mapping has revealed the presence of weathered andesite bedrock on many hillslopes. Conversely, evidence for glaciation is limited and restricted to a few exposures of till and meltwater channels suggesting that the last (Late Devensian) ice sheet in this area was cold-based, creating a frozen patch that lay to the east of a thermal boundary related to the Tweed ice stream. A well developed solifluction sheet is found on the lower valley slopes, indicating remobilization of former glacial sediments under periglacial conditions when head formed on the upper slopes. A particular feature is the presence of stratified fine gravels forming an upper lithofacies on many hillslopes which appear to be due to reworking of weathered material. Although there has been no dating of these sediments, it is suggested that the upper part of the sequence dates from Late Devensian deglaciation with the soliflucted sediments related to periglacial processes and paraglacial adjustment in association with permafrost degradation at the end of the Dimlington Stadial, and the stratified gravels related to fluvio-nivational processes associated with snowmelt during the subsequent Loch Lomond Stadial.

Advance of alpine glaciers during final retreat of the Cordilleran ice sheet in the Finlay River area, northern British Columbia, Canada

Sharp-crested moraines, up to 120 m high and 9 km beyond Little Ice Age glacier limits, record a late Pleistocene advance of alpine glaciers in the Finlay River area in northern British Columbia. The moraines are regional in extent and record climatic deterioration near the end of the last glaciation. Several lateral moraines are crosscut by meltwater channels that record downwasting of trunk valley ice of the northern Cordilleran ice sheet. Other lateral moraines merge with ice-stagnation deposits in trunk valleys. These relationships confirm the interaction of advancing alpine glaciers with the regionally decaying Cordilleran ice sheet and verify a late-glacial age for the moraines. Sediment cores were collected from eight lakes dammed by the moraines. Two tephras occur in basal sediments of five lakes, demonstrating that the moraines are the same age. Plant macrofossils from sediment cores provide a minimum limiting age of 10,550–10,250 cal yr BP (9230 ± 50 14C yr BP) for abandonment of the moraines. The advance that left the moraines may date to the Younger Dryas period. The Finlay moraines demonstrate that the timing and style of regional deglaciation was important in determining the magnitude of late-glacial glacier advances.

The glacial geomorphology and Pleistocene history of South America between 38°S and 56°S

This paper presents new mapping of the glacial geomorphology of southern South America between latitudes 38°S and 56°S, approximately the area covered by the former Patagonian Ice Sheets. Glacial geomorphological features, including glacial lineations, moraines, meltwater channels, trimlines, sandur and cirques, were mapped from remotely sensed images (Landsat 7 ETM+, pan-sharpened Landsat 7 and ASTER). The landform record indicates that the Patagonian Ice Sheets consisted of 66 main outlet glaciers, together with numerous local cirque glaciers and independent ice domes in the surrounding mountains. In the northern part of the mapped area, in the Chilean Lake District (38–42°S), large piedmont glaciers developed on the western side of the Andes and the maximum positions of these outlet glaciers are, in general, marked by arcuate terminal moraines. To the east of the Andes between 38°S and 42°S, outlet glaciers were more restricted in extent and formed “alpine-style” valley glaciers. Along the eastern flank of the Andes south of ∼45°S a series of large fast-flowing outlet glaciers drained the ice sheet. The location of these outlet glaciers was topographically controlled and there was limited scope for interactions between individual lobes. West of the Andes at this latitude, there is geomorphological evidence for an independent ice cap close to sea level on the Taitao Peninsula. The age of this ice cap is unclear but it may represent evidence of glacier growth during the Antarctic Cold Reversal and/or Younger Dryas Chronozone. Maximum glacier positions are difficult to determine along much of the western side of the Andes south of 42°S because of the limited land there, and it is assumed that most of these glaciers had marine termini. In the south-east of the mapped area, in the Fuegan Andes (Cordillera Darwin), the landform record provides evidence of ice-sheet initiation. By adding published dates for glacier advances from the literature we present maps of pre-Last Glacial Maximum (LGM) glacier extent, LGM extent and the positions of other large mapped moraines younger than LGM in age. A number of large moraines occur within the known LGM limits. The age of these moraines is unknown but, since many of them lie well outside the established maximum Neoglacial positions, the possibility that they reflect a return to glacial climates during the Younger Dryas Chronozone or Antarctic Cold Reversal cannot be discounted.

Glacial geomorphology of the central sector of the last British-Irish Ice Sheet

Please click here to download the map associated with this article. We here present a glacial geomorphological map covering 11,800 km2, at a scale of 1:550,000, of the central sector of the last (Main Late Devensian) British-Irish Ice Sheet. The map is based on the 5 m resolution NEXTMap dataset. Six landform types have been mapped; subglacial lineations, hummocky terrain, ribbed moraine, meltwater channels, eskers and glaciofluvial sediment accumulations. The subglacial lineations have been further sub-divided into a series of ‘flow sets’ based on their morphology, conformity and length. Over 9,000 individual landforms have been identified within the study area, concentrated predominantly in the lowlands of the Vale of Eden, Solway and over the Tyne and Stainmore Gaps. A palimpsest geomorphic signature characterised by cross-cutting flow-sets is interpreted as evidence that dynamic, multiphase ice flow occurred throughout the Main Late Devensian (marine isotope stage 2) in response to migrating ice dispersal centres and ice divides. A relative chronology has been constructed and interpreted, based on the complex, cross-cutting flow signatures displayed throughout the region.

The Glacial Map of southern South America

Please click here to download the map associated with this article. This paper describes The Glacial Map of southern South America. This is a new map of the glacial geomorphology of southern South America between latitudes 38°S and 56°S, approximately the area covered by the former Patagonian Ice Sheets. The map was compiled from interpretation of remotely sensed images (Landsat 7 ETM+, pan-sharpened Landsat 7 and ASTER scenes). The mapped geomorphological features include terminal moraines, glacial lineations, ribbed moraine, glacier debris stripes, trimlines, empty cirques, plateau edge, volcanoes, meltwater channels, deltas, glacial lake shorelines, alluvial fans, sandar, and glacial lake outburst ood tracks. The map also indicates the current extent of major icefields and glaciers in the area, as well as other topographic features such as lakes, rivers, shorelines, deltas, plateau surfaces and volcanoes. We briey describe the most commonly occurring glacial landforms and provide an overview of their distribution within the mapped area.

A geomorphological map of Cadair Idris, Wales

Please click here to download the map associated with this article. This paper presents a new 1:10 000 scale geomorphological map of Cadair Idris, Wales. The geomorphology was mapped by the interpretation of colour aerial photographs (scale 1:10 000) and field investigations of landform/sediment associations. Digital Elevation Models (horizontal resolution 5 m, vertical resolution 1 m) sourced from NEXTMap Britain were used to supplement the geomorphological mapping, signi-cantly enhancing the ability to observe and identify landforms, bedrock structure and landscape composition. The geomorphological map shows the spatial distribution of glacial, periglacial and postglacial landforms such as cirques, end moraines, glacial striations, block fields, tors, meltwater channels, scree slopes and alluvial fans. Some of these features have not previously been identified, such as recessional moraines. The mapped landforms are used to make inferences about the glacial history of the area and will thereby give insight into the palaeoglaciology of the central Welsh uplands. The geomorphological mapping will also be used as basis for geoconservation planning by the Countryside Council for Wales and the Welsh Regionally Important Geological/Geomorphological Sites groups.

Glacial geomorphology of the Bayan Har sector of the NE Tibetan Plateau

Please click here to download the map associated with this article. We here present a detailed glacial geomorphological map covering 136,500 km2 of the Bayan Har sector of the northeastern Tibetan Plateau—an area previously suggested to have nourished the most extensive Quaternary glaciers of the Tibetan Plateau. The map, presented at a scale of 1:650,000, is based on remote sensing of a 90 m SRTM digital elevation model and 15/30 m Landsat ETM+ satellite imagery. Seven landform types have been mapped; glacial valleys, glacial troughs, glacial lineations, marginal moraines, marginal moraine remnants, meltwater channels and hummocky terrain. A large number of glacial landforms exist, concentrated around mountain blocks protruding above the surrounding plateau area, testifying to former glacial activity. In contrast, large plateau areas of lower altitude lack glacial landforms. The mapped glacial geomorphology indicates multiple former glacial advances primarily by valley and piedmont glaciers, but lends no support to the hypothesis of ice sheet scale glaciation in the area. The presented glacial geomorphological map demonstrates the usefulness of remote sensing techniques for mapping the glacial geomorphology of the Tibetan Plateau, and it will be used for reconstructing the paleoglaciology of the Bayan Har sector of the northeastern Tibetan Plateau.

Landscape and sediment processes in a proglacial valley, the Mittivakkat Glacier area, Southeast Greenland

Geografisk Tidsskrift, Danish Journal of Geography 108(1):97–110, 2008 During the Little Ice Age (LIA), the present proglacial Mittivakkat Valley, stretching 1.5 km ENE-WSW from the terminus of the Mittivakkat Glacier tongue to a delta terminating in the Sermilik Fjord, Southeast Greenland, was transgressed by the glacier as indicated by a terminal moraine near the valley mouth. The first recordings of the glacier terminus in 1933 show a frontal retreat of about 300 m since the Little Ice Age (LIA). Since then, the glacier has retreated another 1200 m leaving a valley train characterized by steep slopes flanking a 150–300 m wide flat-bottomed, sediment-floored trough. The larger part of the valley is floored by fluvial sediments and shows a typical valley sandur stream, the Mittivakkat stream, with one or two main water-channels, which branches out in a braided stream system with numerous intervening channel bars. In the outer part of the valley train, the Mittivakkat stream is erosive and divides around remnants of ground moraine, end-moraines, and outwash with abandoned meltwater channels. In this area some bank erosion is seen, but rejuvenation of older stream channels takes place during spring time when snowbridges cover the recent outlet and force the meltwater to follow the older channels at a higher level. Most recently, the seaward side of the outermost end-moraine ridge has been eroded by the sea, probably because the delta area is degrading. This could be a result of a decreased delivery of glaciofluvial sediments, due to the sink effect of the proglacial valley, but also because of less sea ice during summer periods and a more recent shift in wind directions during open water periods towards south and west. Geoelectric measurements (Schlumberger) along a number of traverses show sediment thicknesses in the valley trough of 6–23 m, which suggest that 2.2 x 106 m3 of sediment has been deposited in the valley. The estimated volume of glaciofluvial sediments deposited in the valley and delta is 9.9 x 106 m3. Recent sediment transport from the glacier basin of 18.4 km2 through the Mittivakkat Valley to the Sermilik Fjord at the mouth of the valley has been monitored. The annual average is around 7,000 m−3. The investigations confirm that a slight net deposition takes place in the upper part of the valley, showing that the proglacial valley will trap more of the sediment released by glacial erosion if the Mittivakkat Glacier continues to retreat. Thus, the investigation demonstrates the close interaction between the different morphological zones in a proglacial sediment transport system.

First-order reconstructions of a Late Ordovician Saharan ice sheet

Synthesis of outcrop and subsurface sedimentological and geomorphological datasets across North Africa allows a tentative palaeo-glaciological model of the flow dynamics and recessional character of a 440 Ma old (Hirnantian) ice sheet to be proposed. A system of eight cross-shelf trough depocentres is identified from the Late Ordovician of the Sahara region. These are interpreted to have been carved and occupied by ice streams, providing evidence for widespread heterogeneous flow within the ice sheet. During retreat, two key geological features were produced: (1) laterally extensive, sinuous to linear piles of sediment dumped parallel to the ice margin; (2) large meltwater channels (tunnel valleys) cut near the grounding line.

Neubewertung der geomorphologischen Entwicklung der Umgebung des Rangsdorfer Sees

Abstract. In order to reassess the geomorphologic development of the Rangsdorf lake area a strategy combining the technical potentials of a GIS with geomorphologic fieldwork was developed. As a basis for the GIS-analysis topographic and geologic maps of different age were digitally processed. The main focus was on updating the Prussian Geological Maps from the 19th century. After the combination with a specially developed DEM, a preliminary model of the geomorphologic development was constructed: In Weichselian time subglacial meltwater deeply incised into a push-morainic area of Saalian age, creating a braided system of meltwater channels. In the course of the meltdown of the ice subaeric meltwater runoff and with it accumulational processes set in. Large masses of dead ice were buried especially within the overdeepened meltwater channels. Later, as the dead ice started to melt a broad lake system evolved. Dunes were formed in lateglacial time. The Holocene was dominated by accumulative processes which caused a relative levelling of the relief. In the course of the verification of that model by fieldwork it became clear that the Saalian formation is of even greater meaning than assumed before: Not only full forms but also channels originate from Saalian time. The predominance of glacially-erosive processes on the till plains and glacially-accumulative processes within the meltwater channels throughout the Weichselian Glaciation was supported by the field evidence.

Nature, Origin, and Age Relationships of Landscape Complexes in Southwestern Saskatchewan

Six landscape complexes are recognized in the Cypress Lake (72 F) and Wood Mountain (72 G) areas of southwestern Saskatchewan. The complexes are recognized by their geomorphology, geology, and processes of landscape formation. The relationships of these components are used to determine the relative ages of the complexes. The oldest complex designated “unglaciated bedrock terrain”, consists of mature landscapes developed in Late Cretaceous and Tertiary sediments. It was formed by fluvial and mass wasting processes under Late Tertiary arid to semi-arid climates. A rather similar complex, but with scattered drift residuals - chiefly glacial erratics, is called “bedrock terrain with residual drift”. This complex reflects similar Late Tertiary processes of landscape formation but was later affected by Pleistocene glaciation. A complex called “bedrock terrain and drift” resembles the older complexes except for a veneer of drift and local meltwater channels. Here, effects of the Late Wisconsinan glaciation are restricted to meltwater erosion, and the drift appears to predate this glaciation. The other three landscape complexes are: “first advance drift”, “interlobate drift” and “last advance drift”. These include terrain typical of the parts of the southern prairies covered by the Late Wisconsinan glacier.

Mass balance and dynamics of a valley glacier measured by high-resolution LiDAR

ABSTRACTThe changing surface geometry of the glacier Midre Lovénbreen on Svalbard was investigated using LiDAR data acquired on 9 August 2003 and again on 5 July 2005. The data were processed to generate Digital Elevation Models (DEMs) of unprecedentedly high spatial resolution (2 m) and accuracy (better than 0.15 m). Comparison of the two DEMs allowed the mass balance of the glacier to be determined as more negative than −0.62 m yr−1 water equivalent, about twice as negative as the value estimated from in situ measurements. Comparison of the DEMs also showed that the area of the glacier decreased by around 0.3%, and the position of its margin retreated by around 14 m, from 2003 to 2005. It was also possible to track the motion of fine-scale features in the surface geometry such as meltwater channels, and hence to determine the glacier's surface velocity, in some areas. Typical average speeds were around 1–2 cm per day.