All available data on suspended sediment concentration and sediment discharge for Central Asian rivers have been used to estimate the small-grained sediment discharge from glaciated areas. Glacial streams discharge the bulk of suspended material during the period of intensive melting (July to September). There is a good exponential relationship between the suspended sediment concentration (or sediment discharge) and air temperature over glaciers. The area of the largest glacier in the watershed is another factor influencing the silt content and sediment run-off. Its contribution is smaller than that of air temperature. Yearly sediment run-off for glacial rivers in the Pamir and Tien Shan has been computed. Highest values are from the Pamir with many rivers yielding 3000 tonnes km–2 (11 200 tonnes km–2 for the Vukhsh river). The highest run-off in Tien Shan is 2 000 tonnes km–2 for the Chatkal river.

The development of medial moraines on the Glacier de Tsidjiore Nouve is related to numerous englacial debris layers of limited dimensions, which are exposed at the glacier surface below the Pigne d’Arolla ice fall. Previous research has suggested that such layers result either from high-level transport of debris, derived from rock weathering and/or glacial erosion in the accumulation zone, or from shearing up of subglacial debris owing to intense compressive stresses in the glacier. The morphology of the debris layers is investigated in the field, and samples are subjected to particle-size analysis. It is concluded that constituent debris is derived largely from exposed faces of rock between the upper and lower firn basins, but that a subglacial component is present. Entry of the debris into the glacier is possibly by way of crevasses on the lower firn basin.

Field experiments have shown that unlithified sediments beneath a glacier may undergo strong shear deformation in response to the movement of the overlying glacier, and that much of the forward movement of the glacier may be contributed by this mechanism. Mathematical analysis of the physics of this process suggests that it can be very important in glaciers underlain by deformable sediments

Two- and three-dimensional patterns of subglacial sediment deformation are analysed in response to both irregularities on a sub-sediment rock bed and grain-size inhomogeneities within the sediment itself. The results of a modeling exercise show that drumlin fields may develop from subglacial deformation and that the form and size of the drumlin depend primarily on ice velocity, effective stress, sediment strength properties, and time.

Characteristic structures are described which are believed to reflect this process, and allow it to be recognized in areas of Quaternary glaciation.

Subglacial sediment deformation has an important effect on glacier dynamics, and icesheet reconstructions using this as a boundary condition are presented for the Laurentide and European ice sheets at 20 ka BP.

Recent work by Clapperton (1975) proposes that the rapid rates of advance experienced by glaciers which surge may lead to enhanced debris incorporation, increased compressive flow near the glacier snout at the point of maximum extension, and to the upward translation and vertical stacking of debris near the glacier snout and margin. Five glaciers in Spitsbergen (Battyebreen, Holmströmbreen, Lisbetbreen, Vonbreen, Elnabreen) display morphological features which are widely accepted as being diagnostic of surging glaciers.

Results of detailed observations regarding the nature, distribution, melt-out, and reworking of englacial debris at Battyebreen are presented. Basally derived till is brought to the surface of the glacier in narrow lateral and terminal belts, no more than 100 m wide. Within this zone, (i.e. up-valley from the snout and towards the valley centre) the ice is debris-free with the exception of small amounts of en-glacial debris which form the core of lobate medial moraines. Differential ablation of debris-free and debris-rich ice leads to the production of a topographic basin within which melt-out and reworking processes occupy restricted locations, as follows. Immediately inside the encircling melt-out till, a zone of flow tills is found. Melt streams are located at the foot of, the flow till-mantled slope, producing narrow (150 m wide) outwash trains, which merge into deltas. The central area of the topographic basin is occupied by a supraglacial lake.

Observations of the remaining four locations confirm that other glaciers in the vicinity, which display similar characteristics associated with surging, are developing a stagnant-ice zone of identical appearance. The pattern of processes observed at Battyebreen is thus repeated at each site.

A simple model of depositional landscape development is proposed for surging valley glaciers in a sub-polar environment.

A number of moraine-covered ice hills 1 to 2 m in height, 3 to 5 m in major axis, and 2 to 3 m in minor axis (referred to as moraine-hills for convenience) were found sporadically on the ice surface near the terminal margin of the lobe of McCall Glacier, a subpolar glacier in Arctic Alaska, during our observations made in the summers and early falls of 1971 and 1972. The thickness of a moraine layer covering an ice hill was of the order of 0.3 to 0.5 m; the moraine was mostly composed of sand and silt with a small amount of rounded pebbles.

More than ten conformal arc-shaped thrust faults. convex down-glacier. with an interval from 20 to 30 m were also found on the ice surface. 150 to 300 m away from the terminus of the glacier. It was noted that these thrust faults were associated with the moraine-hills; hence, all the moraine-hills found in the area were located along the thrust faults. This strongly suggests that these moraines had been transported by shear action along thrust planes in the ice body from the bed to the upper surface of the glacier.

Crossing the thrust faults, a supraglacial stream 3 to 5 m in depth had formed, in which melt water from the ablation area was flowing. On the vertical wall of the stream. a large number of inclined dense dirt layers were observed along shear planes; they were parallel to one another and from 50 to 100 mm apart. Blocks of dirt ice samples were cut out from the wall of the stream so that the fine structure and texture of the dirt ice could be investigated in detail; the inner moraines contained in them were also collected for microscopic examinations. The results showed that the moraines were mostly composed of sand and silt. It is, therefore, most unlikely that such fine particles were formed by scraping of rocks from the glacier bed, because rounded sand and silt are usually formed by grinding action in a turbulent stream flow. Hence, it may be assumed that they have been formed in a subglacial stream.

Meanwhile. an ice tunnel was found extending deep into the glacier from the terminus along the bed of the glacier, in which a subglacial stream was running. The water flow of the stream decreases markedly with the onset of winter, giving access to the inside of the tunnel, so areconnaissance was made inside the tunnel near the entrance in the autumn of 1971. Deposits on the bed of the glacier and the stream were examined, and it was found that large amounts of sand and silt existed among rounded-shaped rocks on the greatly smoothed surface of the bed. The sand and silt must be the origin of the inner moraines found along the thrust planes and of the moraine layers covering the ice hills on the glacier surface.

There has been much argument by earlier workers about the mechanism of formation of inner moraines near the edge of a cold ice cap. Theories and models such as a shear hypothesis(Chamberlin and Salisbury 1904:chapter 5) and a freezing model (Weertman 1961) have been proposed, but no definite conclusion has been reached.

A series of simulation experiments were conducted in a cold laboratory in order to study the mechanism of formation of inner moraines in a glacier. To simulate a glacier, ice was confined between two parallel solid planes inclined at a small angle, the top surface being smooth and the bottom surface irregular with various protuberances. A small amount of sand was placed at the interface between the bottom surface and the ice. and pressure was applied to the ice along the inclination perpendicular to the parallel line of the two planes. Movements of sand particles accompanying the ice flow over the uneven bottom surface were observed at 0˚C under a microscope; 16 mm time‐lapse motion pictures were also táken for observation of detailed processes in which sand particles were picked up into the body of ice and inner moraine layers were formed. The observations disclosed that sand párticles were carried into the body of the ice at the top of a protuberance to form moraine layers and were further transported obliquely upward by shear action along shear plaries.

Glaciomarine sediments (GMS) comprise detrital, biogenic, and authigenic materials of two principal facies: laminated deposits and massive aqueous till. The processes governing sedimentation of the ice-rafted debris (IRD) component of GMS are investigated in the marine zone around Antarctica. Four controlling factors are identified: nature and disposition of sediments at the grounding line, transition from grounded to floating ice (ice shelves, outlet glaciers, and ice cliffs), processes of under-side melting and freezing of these ice masses, and, finally, mechanisms of iceberg calving, fragmentation, and melt-release of debris in the open ocean. Modelling studies of Brunt and Ross ice shelves suggest two main conclusions. (1) Ice shelves are of major importance for sedimentation on the continental shelf. Bulk •debris release occurs within the grounding-line zone which may frequently oscillate, producing pronounced diachronism. Bottom melting removes all debris prior to calving at the ice front so that ice shelves do not play a part in deposition in the open ocean. (2) Outlet glaciers, in contrast, have high sediment content, calve rapidly, and produce debris-rich icebergs which contribute the major portion of IRD in the ocean.

Present-day sedimentary environments in the eastern Weddell Sea confirm low clastic sediment input from wide (> 100 km) ice shelves. Mainly bioclastic sediments are formed in situ on the inner and shallow central-shelf areas (250 to 350 m water depth), with sedimentation rates probably < 0.01 m ka−3. Ice-rafted debris (IRD) is mainly deposited on the outer shelf and upper continental slope, with a sedimentation rate of 0.02 to 0.07 m ka−3. The coarse-grained texture of these deposits is caused by removal of finer grades in suspension during settling of IRD sediments. Overconsolidated till was deposited < 31 ka BP during expansion of grounded ice to the shelf break. Subsequent eustatic rise caused grounded ice to float. Frozen-on sediments melted out of the base of the ice, depositing soft pebbly mud above the till. Marine conditions similar to present-day conditions were found for the interval 30 to 40 ka BP.

IRD variation is an indicator of ice-shelf coverage and changes in relative sea-level, and is, in low latitudes, probably inversely related to the degree of ice cover.

Sampling of sediment from the fjord floor in front of tidewater glaciers in Glacier Bay, Alaska, has provided information about processes in this restricted glacimarine (Dreimanis 1979) setting. Sediment sampling, in conjunction with oceanographic and glacial dynamics data, has also enabled the discrimination of sediment types and their facies associations. Deposits are strongly controlled by: sea-water characteristics, position and sediment discharge of melt-water streams, iceberg calving, and rate of glacierfront retreat.

Five distinct facies associations have been found to reflect glacier-fjord regimes. The facies associations and ice-fjord conditions responsible for them form the basis for constructing a preliminary model for glacimarine sedimentation by tidewater glaciers. The model can be used to predict (i) rapid retreat of an actively calving ice front, (ii) slow retreat or stabilization of a calving ice front at a channel constriction, (iii) stabilization of a melting (very rarely calving) ice front when the glacier base is near tidewater elevation, and (iv) large outwash delta progradation into a fjord when the ice front retreats onto land. This model can be used to interpret facies associations found in a stratigraphic record.

The morphology, sediments, and processes associated with the construction of a moraine along the western margin of the ice shelf in George VI Sound, Antarctica, are discussed. The moraine occurs as a double ridge where the ice sheet grounds against promontories on Alexander Island and is approximately horizontal over a distance of 120 km. It consists of exotic rock debris carried into the ice shelf by Antarctic Peninsula glaciers and local rock debris derived from the grounding line on Alexander Island. As the coast steepens, so the proportion of exotic rocks increases. The transport of basal material from the peninsula implies that there can be little bottom melting beneath this part of the ice shelf. The moraine is modified by streams and marginal lakes which periodically drain into and through the ice shelf. Tidal lakes are impounded against the ice shelf in shallower embayments and consist of fresh water overlying sea-water. A conceptual model of the moraine is developed and may help to explain some features of puzzling horizontal moraines found in formerly glaciated areas.

Samples of glaciomarine sediments and suspended particulate matter filtered from sea-water were collected in the Weddell Sea during the Norwegian Antarctic Research Expedition (NARE) in 1978–79. Analyses have provided information on the textural and mineralogical composition of shelf sediments, on the nature of biogenic and inorganic suspended particulate matter, and on the total sediment transport to the shelf areas and further into the deeper waters (Orheim and Elverhøi 1981).

The shelf waters contain 0.1 to 1.2 g m–3 of suspended particulate matter, which is close to the range of 0.5 to 1.5 g m–3 reported for suspension concentrations in the oceans, but considerably lower than that found for some other glaciomarine environments such as the Bering Sea {up to 13-15 g m–3 (Lisitzin 1972)) and off Kongsbreen, Spitsbergen {up to 500 g m–3 (Elverhøi and others 1980)).

Suspended particles from the Weddell Sea have maximum sizes of 50 to 70 µm and mean diameters in the range of 10 to 20 µm. In contrast, the bottom sediments on the outer shelf are deficient in the corresponding fractions. This reflects that when floating Antarctic ice supplies material to the Weddell Sea, the coarser fragments (>20-70 µm) are deposited, while the medium silt and finer fractions go into suspension. Considering the suspended-load data and the bottom-current measurements on the shelf break, it is evident that in January 1979 an average of 8.6 × 104tonnes d–1 (or 32 × 106 tonnes a–l) of particulate matter was transported by the current from the central Weddell Sea to the South Atlantic deep water. Morphological (scanning electron microscopy) and chemical analyses show the suspended material to be dominated by silica organisms (diatoms), and also to contain clastic grains of phyllosilicates, feldspar, quartz, zircon, in a few cases Al- and Fe-hydroxides/oxides also; authigenic “Fe-sepiolite” and secondary gypsum.

Mineralogical analyses (X-ray diffraction) of the bottom sediments show the fine sand silt fractions to contain mainly clastic materials like illite, smectite-vermiculite, and quartz. Biogenic silica (cristobalite) and carbonate (Mg-calcite) as well as authigenic Fe-silicates (“Fe-sepiolite”) are also present.

In the marginal areas of the Pleistocene Scandinavian ice sheet in north Germany there are few signs of direct glacial erosion. Fine gravel analyses show that glacial reworking was not very important. This may be partly due to the fact that at least in the late phases of the glaciation the active parts of the ice sheet moved over dead ice and were not in direct contact with the underlying substratum. Buried tunnel valleys with a depth of more than 400m show that considerable erosion by sub glacial melt-water streams took place, at least during the Elsterian glaciation.

Recent stratigraphic studies have characterized the sequence and nature of tills deposited in Iowa and Illinois by Quaternary Laurentide ice sheets. Basal tills within the sequence are each dominated by matrix-size materials and exhibit uniform matrix properties over hundreds or thousands of square kilometers. This uniformity suggests that matrix-size materials were effectively mixed for each basal till. Three mixing processes seem probable: differential shear in debris-rich basal ice; continuous subglacial deformation of the till; and repeated erosion-transportation-deposition of matrix-size materials during recurrent regelation in the basal ice. Shearing and subglacial deformation appear to have been only locally important. Most of the mixing may have occurred during regelation. Particles on the bed may have been frozen into the basal ice during regelation freezing, and transported until deposited during subsequent pressure-melting on a down-glacier obstacle. During recurrent regelation on fine-grained beds such as occurred in this area, particles may have been subject to several periods of erosion-transportation deposition, and mixed through time over long transport distances. This mixing process was certainly not the only process taking place, but it appears to have been the dominant subglacial mixing process.

An erosion rate of 0.5 to 0.6 mm a−1 is deduced for a Younger Dryas cirque glacier. The erosion period of 700 a was determined from the laminated glaciolacustrine sediments in a small lake just outside the end moraine of the cirque and radiocarbon dates obtained below and above these sediments. The volume of eroded bedrock was calculated from measurements of the deposited sediments, of which the end moraine, the glaciofluvial delta, and the glaciolacustrine sediments are most important. With a constant erosion rate, the cirque could have formed in 83 to 125 000 a.

The influence of bedrock structures, especially joints, on the formation of roches moutonnées and different glacial abrasion forms on roches moutonnées were studied in the southwest archipelago of Finland.The size and form of roches moutonnées are closely connected with the frequency and state of joints in the bedrock. The fewer and smaller the joints are, the larger are the roches moutonnées that can be formed. Vertical joints in the direction of the ice movement form the weakest zones and determine the width of the roches moutonnées. Joints dipping against glacial movement determine the dip of the eroded rock surface. Horizontal joints provide a suitable base for large and gently-dipping roches moutonnées, which are normally lower than others with less frequent horizontal joints. Striae, friction cracks, facets, fracture lines, and plucked surfaces, and their positions on the surfaces of roches moutonnées, were observed. On the basis of these observations, a stereographic model of the distribution of different abrasion features on the surfaces of roches moutonnées was produced.

The recent topography of Kamchatka was formed by the joint activity of endogenic and exogenic processes among which glacial erosion and sedimentation played the most important role. Glacial erosion is exhibited to different degrees on old and young mountains. Corrie and corrie-valley glaciers are common to the oldest and strongly eroded early Pleistocene volcanoes. The flanks of Holocene volcanoes are only s1ightly affected by exogenic processes. As a result, ice caps and ice belts as well as crater glaciers are developed on them.

During earlier glaciations, the influence of volcanism on glaciers and frozen strata caused the specific conditions for sub-ice eruptions, as a result of which strata of welded tuffs and pumices, and thick strata of fragmented material were formed. Recent and older glaciers in regions of active volcanism are covered by large amounts of pyroclastic material. During intense melting of glacier ice in these regions, thick fields of morainic deposits were formed. Similar conditions are found in Iceland, as describeo by (Thorarinsson 1958, Thorarinsson 1974), among others.

Highly-weathered Pre-Cambrian bedrock has been reported from scattered localities across Arctic Canada during the past decade. As part of a study on weathering processes under arid conditions, field studies are reported on-similar terrain in the Alexandra Fjord-Cape Herschel area of east-central Ellesmere Island. Features examined and sampled in both near-coastal and upland positions include grus, tor-like forms, weathering pits, and tafoni. Factors influencing their development and preservation are reviewed. Particular emphasis is placed on the influence of bedrock lithology and mineralogy (in this case, hornblende content) on the intensity of physical disintegration under cold arid conditions. Chemical analyses and petrographic data are presented in support of this observation. Preservation of certain remnant weathering features in upland summit areas under cold-based glacial ice is postulated.

The Tiskilwa Till Member of the Wedron Formation represents deposition by basal melt-outin the marginal area of the Laurentide ice sheetduring the Woodfordian (late-Wisconsinan) in Illinois. Distinctive characteristics include: a very thick, homogeneous till; relatively little ablation till; red color; sandy texture; illite content that is relatively low withrespect to other Woodfordian tills; and the presence of discontinuous basal zones of differing composition.

Erosion and entrainment of debris from both distant and local source areas are evident in the Tiskilwa Jill. Basal thermal regime is suggested as a major controlling factor on the location of the zones of entrainment. The debris was homogenized en route to the margin and eventually was deposited as basal melt-out till near the margin. Deposition occurred within an interval of 6 ka or more during the first half of the Woodfordian.

Previous work on drumlin genesis considers the problem at the ice-rock interface and ignores the environmental significance of inter-drumlin sediments and superimposed landform associations. Present work by the author examines two drumlin fields in south-central Ulster, Northern Ireland, and proposes a mechanism of drumlin formation which is time-dependent and results from changes of thermal regime through time.

Drumlin exposures in south-central Ulster reveal a particular facies association in drumlin tills showing considerable lithological variation; striae, roches moutonnées, and basal lodgement till beneath drumlins indicate an event early in the last glaciation characterized by a temperate thermal regime. This association is overlain by a basal melt-out till, characterized by striated clasts and containing numerous pockets of stratified sediment. The melt-out till is related to changes in provenance of erratics in the till, associated with a shift in the centre of ice accumulation during the course of glaciation.

The stratigraphy suggests that a considerable amount of drift was formed prior to drumlin formation and that a change of thermal state may have characterized the shift in the ice accumulation zone. This change is also suggested by evidence of high-level melt-water transport in the Sperrin Mountains, indicating a sub-polar or sub-temperate thermal regime existing in the early part of the late Weichselian deglaciation.

A model based on thermal convection theory of polar ice sheets (Hughes 1976) is proposed in an attempt to relate the juxtaposition of drumlins and glaciofluvial assemblages in southcentral Ulster. In an ice accumulation zone, as characterized this area during the late Weichselian glacial maximum, advection is generally absent and convection is the dominant flow in the ice sheet. In this environment motive ice may develop in the basal zone, resulting from vertical buoyancy stresses acting downward on a column in the ice sheet. This flow environment may coexist within an ice sheet which is "stagnant" and perhaps subject to supraglacial insolation melting, depending on the overall climatic regime. If convection is dominant, it may create areas of basal compression and tension, acting to establish co-existing zones of "hot" and "cold" ice; hot-ice zones are subject to basal erosion, leading to migration of subglacial sediments to points of englacial storage above the density inversion layer. Cold-ice zones act to protect underlying sediments and result in isolation of drift nuclei, protection being afforded by the yield strength of frozen drift being greater than either debris-laden or clean ice.

If the model is tenable, it seems likely that drift nucleation in drumlin fields may have been accomplished before the drumlin formation or streamlining event. Vertical migration of subglacial materials also explains the similarity of sediment sources of glacigenic and glaciofluvial assemblages which occur in juxtaposition, and, without reduction in drumlin density. The sequence of events in south-central Ulster may be summarized as follows:

Radiocarbon dates of 13 000 a BP at the Cheboygan bryophyte bed in Michigan and 11 800 a BP at the Two Creeks site in Wisconsin bracket three ice advance/retreat cycles and one advance to the Two Creeks site of the Lake Michigan lobe. These advances are documented by individual till sheets separated by lacustrine fine sand and silt-clay units. The tills are distinguishable only by small differences in grain-size distribution and clay-mineral content. They probably reflect closely the composition of the sediment being deposited in the Lake Michigan basin between advances. Because of lack of exposure and probable erosion of pre-existing material by each successive ice advance, the maximum extent of retreat between the deposition of the tills cannot be documented. We can demonstrate, however, that a total of at least 850 and perhaps over 1 000 km of combined retreat and advance took place during this period of 1 200 a. This implies that the change in ice-margin position averaged 0.7 to 0.9 km a-1, a rate higher than most recorded on modern glaciers. Since this is an average rate over 1 200 a and encompasses several advances and retreats, the actual rate of change in ice-margin position must at times have been considerably more rapid.

There is very little evidence in the pollen record of climatic changes that would explain rapid advances and retreats of this magnitude. This observation has led to suggestions that late Wisconsin age advances in various parts of the Great Lakes were surges unrelated to climate change.

We suggest instead that the shape of the Lake Michigan basin, and the substantial changes in water level that might have occurred in it, could have greatly amplified the smaller fluctuations of the ice margin that have been documented across the eastern United States (presumably resulting from changes in mass balance), and so could have produced the rapid advances and retreats seen in the stratigraphic record.

The Lake Michigan basin consists of two deep areas with a high area in between. Present water depths are over 280 m in the northern basin, less than 60 m on the mid-lake high, and more than 160 m in the southern basin. All of the ice advances discussed above seem to have stopped either on the northern (up-stream) side or on the crest of the mid-lake high. Even conservative estimates of the amount of isostatic crustal depression at that time suggest that if water could drain into the eastern Great Lakes during retreat of the ice to the north end of the basin, lake level could have dropped as much as 220 m. Although there is no stratigraphic evidence that drainage out of the north end of the basin took place between these ice advances, there are valleys cut in drift and bedrock extending from the north basin eastward toward the Lake Huron basin. It is possible that these valleys formed during the rapid draining of the lake between ice advances. Whenever ice advanced, blocking the northern outlet, lake level rose back to the Glenwood level (which has well-developed beaches), and the lake drained through the Chicago outlet to the south.

Our model is as follows. Consider a grounded ice sheet filling the northern basin and terminating at an equilibrium position on the crest or up-stream side of the mid-lake high. The ice sheet would be unstable in that any initial retreat of the grounding line (i.e. the boundary between the grounded ice and either floating ice or open water) would accelerate as the grounding line moved northward into deeper water. Now let a general marginal retreat occur. Rapid retreat of the grounding line follows until the grounding line passes the northern lake outlet. The consequent large drop in lake level leads then to a readvance of the grounding line, re-blocking the outlet and causing the basin to refill with water. A new equilibrium position of the grounding line is established on the northern side of the basin. As the mass balance increases again, associated with a general marginal advance of the ice sheet, an ice shelf forms (if it was not already there) and grows southward until it grounds on the mid-lake high. That then causes the grounding line to advance rapidly to the position of the margin, whereupon the process is ready to repeat. Each advance would be smaller than the previous because rebound would be tilting the north end of the lake upward, shoaling the water and causing ice shelves to ground further north on the mid-lake high. In addition, the mass of ice to the north was probably shrinking.

Grain-size distribution and mineralogic characteristics of the tills along the Lake Michigan shoreline have been analyzed extensively. However, the existence of a floating ice shelf in the basin at various times during this period cannot, at present, be deduced from the sediment.