Medial Moraines Research Articles

The distribution and flow characteristics of surge-type glaciers in the Canadian High Arctic

AbstractA systematic review of 1959/60 aerial photography, and 1999/2000 Landsat 7 imagery, has identified 51 surge-type polythermal glaciers in the Canadian High Arctic. These were identified from the presence of features such as looped medial moraines, intense folding visible at the surface, rapid terminus advance, heavy surface crevassing, and high surface velocities. These observations suggest that surging glaciers are much more common than previously believed in the Canadian High Arctic, where only six surge-type glaciers have previously been described. Of the 51 surge-type glaciers identified in this study, 15 were observed in the active phase in the 1959/60 and/or 1999/2000 imagery. The most dramatic advances have occurred on western Axel Heiberg Island, where Iceberg,“Good Friday Bay” and Airdrop Glaciers have all advanced by 4–7 km between1959 and 1999. For glaciers with repeat Landsat 7 coverage from 1999 and 2000, image correlation software was used to determine the magnitude and spatial distribution of surge velocities. For example,“Mittie” Glacier on Manson Icefield was moving at a rate of up to 1 kma–over a distance of at least 25 km back from its terminus. The terminus of this glacier has advanced by at least 4 km since 1959, and the glacier was observed to be heavily crevassed during overflights in April 2000, with clear signs of surface lowering of 10–25 m indicated by a strandline.

Utilization of 6 × 6 cm format vertical aerial photographs for repetitive mapping of surface morphology and measurement of flow velocities of a small glacier in a remote area: Glaciar Soler, Hielo Patagónico Norte, Chile

AbstractUsing vertical aerial photographs taken manually with a 6 × 6 cm format camera in 1984, 1986 and 1999, the surface morphology of the ablation area of Glaciar Soler, Hielo Patagónico Norte (northern Patagonia icefield), Chile, was studied. Glaciar Soler has an area of 50.9 km2; the ablation area below the icefall is about 7 km long and 2 km wide. An uncontrolled aerial-photographic mosaic for the area below the icefall was assembled from 40–60 aerial photographs, on which the surface morphology was mapped from interpretation of stereo pairs of the enlarged photographs (scales of 1:4500 to 1: 8000). Themapped features include debris-free and debris-covered ices, ogive bands and waves, crevasses, supraglacial streams, moulins, medial moraines, troughs and grooves. A total of 32–34 pairs of ogive bands were recognized, from which an average flow velocity of about 160 m a–1 was deduced. The spacing of a pair of light and dark ogive bands indicates that the flow velocity ranges from about 350 ma–1 near the icefall to some 100 ma–1 near the snout. Comparison of the field-measured data with the ogive spacing indicates that the seasonal variation in flow velocity of Glaciar Soler is very large, probably because of variation in the amount of basal sliding.

Evidence for restricted ice extent during the last glacial maximum in the Koryak Mountains of Chukotka, far eastern Russia

Field evidence in the Koryak Mountains‐ Lake Mainitz region of far eastern Russia supports three Pleistocene glacial advances. The early Wisconsinan and pre-Wisconsinan glaciations are represented by broad lobate moraines extending as much as 30 km north of the Koryak Mountains. Field evidence demonstrates that the terminal, lateral, and medial moraines, as well as meltwater channels, dead ice topography, kettles, and outwash plains mark the extent of ice during the last glacial maximum (LGM), during which glaciers reached no more than 20 km beyond their present limits. Those emanating from the southern Koryak Mountains may have reached the Bering Sea. Numerical and relative dating techniques support these results and test the theoretical models of the LGM in western Beringia. Erratics on moraines and glaciofluvial terraces, common to all valleys at 13‐13.8 m above river level, yield 36 Cl exposure ages ranging from 10.08 to 25.78 ka. The Koryak Mountains‐Lake Mainitz record of glaciation is spatially and temporally consistent with the glaciation pattern across central Beringia found in other terrestrial and marine records. Glacier growth in the Koryak Mountains was sustained by possible increased summer sea surface temperatures and precipitation in the northwest Pacific region. Evidence from the northern Koryak Mountains (lat 64°N, long 177°E) indicates that the extent of ice in western Beringia was limited to mountain and valley glaciers during the LGM. This fieldbased research contradicts M.G. Grosswald’s theoretical Beringian ice sheet hypothesis.

A model of ablation-dominated medial moraines and the generation of debris-mantled glacier snouts

AbstractMedial moraines form striking dark stripes that widen non-linearly, steepen laterally and increase in relief down-glacier from the equilibrium line. Coalescence of these low-ablation-rate features can feed back strongly on the mass balance of a glacier snout. Ablation-dominated medial moraines originate from debris delivered to glacier margins, producing a debris-rich septum between tributary streams of ice below their confluence. Emergence of this ice below the equilibrium line delivers debris to the glacier surface, which then moves down local slopes of evolving morainal topography. A quantitative description of moraine evolution requires specification of the debris concentration field within the glacier, treatment of the melt-rate dependence on debris thickness, and characterization of processes that transport debris once it emerges onto the ice surface. Debris concentration at glacier tributary junctions scales with the erosion rates and the lengths of the tributary-valley walls, and inversely with the tributary ice speeds. Melt rate is damped exponentially by debris, with a ∼10 cm decay scale. Debris flux across the glacier surface scales with the product of debris thickness and local slope. Analytical and numerical results show that medial moraines should develop cross-glacier profiles with parabolic crests and linear slopes, and should widen with age and hence distance down-glacier. Debris should be both thin and uniform over the moraine. Observed faster-than-linear growth of moraine widths with distance reflects the increasing ablation rate down-glacier. Increase in medial moraine cover reduces the local average ablation rate, allowing the glacier to extend further down-valley than meteorology alone would suggest. This feedback is especially effective when moraines merge.

A three-dimensional numerical model of the confluence area of Unteraargletscher, Bernese Alps, Switzerland

AbstractWith the use of a numerical three-dimensional (3-D) model the flow dynamics of the confluence area of Unteraargletscher, Bernese Alps, Switzerland, are studied. Previous predictions, based on conceptual two-dimensional models, about flow characteristics at confluence areas are tested against results from the fully 3-D model. Measured winter velocities are used for model verification. Despite some consistent systematic differences, good overall agreement between measured and calculated surface velocities is obtained. The calculated vertical strain-rate variation with depth is in good agreement with available measurements from boreholes. The ice is found to be almost three times stiffer than standard estimates of rheological parameters for glacier ice would predict. The model predicts a complicated yet realistic pattern of vertical velocity variation along the surface. The most noticeable features of the vertical velocity distribution across the surface are listed, and their relation to topographic surface undulations and the overall dynamics of the confluence discussed. In accordance with previous results from analytical models, a strongly localized surface trough and a concomitant negative (downward orientation) vertical velocity anomaly develop at the junction point. Although depth-integrated strain rates are positive (extension), the basal layer is compressed vertically. The ice-cored medial moraine is formed by differential ablation. The flow mechanics of the confluence area play only an indirect role, by enabling transfer of debris-covered marginal ice towards the confluence center. In the absence of differential ablation, an elongated surface depression would be formed in the down-glacier direction from the junction point instead of an elevated ice-cored medial moraine.

Debris entrainment and transfer in polythermal valley glaciers

AbstractModes of debris entrainment and subsequent transfer in seven “normal” and five surge-type glaciers in Svalbard (76–79° N) are outlined in the context of the structural evolution of a glacier as the ice deforms during flow. Three main modes of entrainment and transfer are inferred from structural and sedimentological observations: (i) The incorporation of angular rockfall material within the stratified sequence of snow/firn/superimposed ice. This debris takes an englacial path through the glacier, becoming folded. At the margins and at the boundaries of flow units the stratified ice including debris is strongly folded, so that near the snout the debris emerges at the surface on the hinges and limbs of the folds, producing medial moraines which merge towards the snout. The resulting lines of debris are transmitted to the proglacial area in the form of regular trains of angular debris. (ii) Incorporation of debris of both supraglacial and basal character within longitudinal foliation. This is particularly evident at the surface of the glacier at the margins or at flow unit boundaries. It can be sometimes demonstrated that foliation is a product of strong folding, since it usually has an axial planar relationship with folded stratification. Foliation-parallel debris thus represents a more advanced stage of deformation than in (i). Although the presence of basal debris is problematic, it is proposed that this material is tightly folded ice derived from the bed in the manner of disharmonie folding. The readily deformed subglacial sediment or bedrock surface represents the plane of décollement. (iii) Thrusting, whereby debris-rich basal ice (including regelation ice) and subglacial sediments are uplifted into an englacial position, sometimes emerging at the ice surface. This material is much more variable in character than that derived from rockfalls, and reflects the substrate lithologies; diamicton with striated clasts and sandy gravels are the most common facies represented. Thrusting is a dynamic process, and in polythermal glaciers is probably linked mainly to the transition from sliding to frozen bed conditions. It is not therefore a solely ice-marginal or proglacial process.

Debris entrainment and transfer in polythermal valley glaciers

AbstractModes of debris entrainment and subsequent transfer in seven “normal” and five surge-type glaciers in Svalbard (76–79° N) are outlined in the context of the structural evolution of a glacier as the ice deforms during flow. Three main modes of entrainment and transfer are inferred from structural and sedimentological observations: (i) The incorporation of angular rockfall material within the stratified sequence of snow/firn/superimposed ice. This debris takes an englacial path through the glacier, becoming folded. At the margins and at the boundaries of flow units the stratified ice including debris is strongly folded, so that near the snout the debris emerges at the surface on the hinges and limbs of the folds, producing medial moraines which merge towards the snout. The resulting lines of debris are transmitted to the proglacial area in the form of regular trains of angular debris. (ii) Incorporation of debris of both supraglacial and basal character within longitudinal foliation. This is particularly evident at the surface of the glacier at the margins or at flow unit boundaries. It can be sometimes demonstrated that foliation is a product of strong folding, since it usually has an axial planar relationship with folded stratification. Foliation-parallel debris thus represents a more advanced stage of deformation than in (i). Although the presence of basal debris is problematic, it is proposed that this material is tightly folded ice derived from the bed in the manner of disharmonie folding. The readily deformed subglacial sediment or bedrock surface represents the plane of décollement. (iii) Thrusting, whereby debris-rich basal ice (including regelation ice) and subglacial sediments are uplifted into an englacial position, sometimes emerging at the ice surface. This material is much more variable in character than that derived from rockfalls, and reflects the substrate lithologies; diamicton with striated clasts and sandy gravels are the most common facies represented. Thrusting is a dynamic process, and in polythermal glaciers is probably linked mainly to the transition from sliding to frozen bed conditions. It is not therefore a solely ice-marginal or proglacial process.

A three-dimensional numerical model of the confluence area of Unteraargletscher, Bernese Alps, Switzerland

AbstractWith the use of a numerical three-dimensional (3-D) model the flow dynamics of the confluence area of Unteraargletscher, Bernese Alps, Switzerland, are studied. Previous predictions, based on conceptual two-dimensional models, about flow characteristics at confluence areas are tested against results from the fully 3-D model. Measured winter velocities are used for model verification. Despite some consistent systematic differences, good overall agreement between measured and calculated surface velocities is obtained. The calculated vertical strain-rate variation with depth is in good agreement with available measurements from boreholes. The ice is found to be almost three times stiffer than standard estimates of rheological parameters for glacier ice would predict. The model predicts a complicated yet realistic pattern of vertical velocity variation along the surface. The most noticeable features of the vertical velocity distribution across the surface are listed, and their relation to topographic surface undulations and the overall dynamics of the confluence discussed. In accordance with previous results from analytical models, a strongly localized surface trough and a concomitant negative (downward orientation) vertical velocity anomaly develop at the junction point. Although depth-integrated strain rates are positive (extension), the basal layer is compressed vertically. The ice-cored medial moraine is formed by differential ablation. The flow mechanics of the confluence area play only an indirect role, by enabling transfer of debris-covered marginal ice towards the confluence center. In the absence of differential ablation, an elongated surface depression would be formed in the down-glacier direction from the junction point instead of an elevated ice-cored medial moraine.

A three-dimensional numerical model of the confluence area of Unteraargletscher, Bernese Alps, Switzerland

AbstractWith the use of a numerical three-dimensional (3-D) model the flow dynamics of the confluence area of Unteraargletscher, Bernese Alps, Switzerland, are studied. Previous predictions, based on conceptual two-dimensional models, about flow characteristics at confluence areas are tested against results from the fully 3-D model. Measured winter velocities are used for model verification. Despite some consistent systematic differences, good overall agreement between measured and calculated surface velocities is obtained. The calculated vertical strain-rate variation with depth is in good agreement with available measurements from boreholes. The ice is found to be almost three times stiffer than standard estimates of rheological parameters for glacier ice would predict. The model predicts a complicated yet realistic pattern of vertical velocity variation along the surface. The most noticeable features of the vertical velocity distribution across the surface are listed, and their relation to topographic surface undulations and the overall dynamics of the confluence discussed. In accordance with previous results from analytical models, a strongly localized surface trough and a concomitant negative (downward orientation) vertical velocity anomaly develop at the junction point. Although depth-integrated strain rates are positive (extension), the basal layer is compressed vertically. The ice-cored medial moraine is formed by differential ablation. The flow mechanics of the confluence area play only an indirect role, by enabling transfer of debris-covered marginal ice towards the confluence center. In the absence of differential ablation, an elongated surface depression would be formed in the down-glacier direction from the junction point instead of an elevated ice-cored medial moraine.

Ice-marginal characteristics of Fridtjovbreen (Svalbard) during its recent surge

Fridtjovbreen is an actively surging tidewater glacier in western Spitsbergen, Svalbard. This paper presents observations made at the western flank of the glacier in July 1997, when the glacier front was still advancing rapidly and was characterised by steep lateral ice cliffs. The geomorphological consequences of the surge include the formation of push moraines from toppled ice blocks along this ice cliff and the development of debris-rich thrusts. There is also evidence of glaciotectonic deformation within deformed debris-rich thrusts. Thrusts are restricted to the lateral margins and are not seen in the terminal calving cliff. On its western flank, Fridtjovbreen is over-riding Sagabreen, a small-tributary glacier. Large facies variations in this area are a result of recycling by Fridtjovbreen of material originally transported as medial moraines on Sagabreen. There are few observations of landform development at actively surging glaciers in Svalbard. The Fridtjovbreen descriptions provide documentation for post-surge landform development. More observations are required at the margins of actively surging glaciers to determine how representative Fridtjovbreen is of a surge event.

Glaciers receive a surge of attention in the Karakoram Himalaya

Between 1994 and 1996 catastrophic movement of the 15.5‐km‐long Chiring Glacier transferred 1‐1.5 km3 of ice from its upper two thirds to its lower third, and into the main Panmah Glacier of which it is a tributary. By October 1996, a lobe of Chiring ice some 3.2 km2 in area had entered and compressed the main glacier, which was severely disturbed for 3 km above and 5 km below the junction of the glaciers (Figure 1). Ice streams and medial moraines were pushed into a series of looped or “tear‐drop” forms, well‐known in the surging glaciers. Despite an observational record back to 1856, it was not previously realized that changes in the glacier involve surging.

Structural evolution of Variegated Glacier, Alaska, U.S.A., since 1948

AbstractАn excellent photographic database, comprising 12 sets of vertical aerial photographs taken between 1948 and 1993, has enabled the structural glaciology of surge-type Variegated Glacier, Alaska, U.S.A., tо be analyzed for a period that spans two surge cycles and includes the effects of three surges. The glacier-wide patterns of crevasse development at the end of each of these surges, which occurred in 1947–48, 1964–65 and 1982–83, were remarkably similar, despite differences in surge intensities and extents. At the end of each surge a three-fold longitudinal zonation of crevasse orientation characterised that part of the glacier that had been affected by surge activity. This zonation comprises: (i) transverse crevasses in a narrow upper zone, (ii) superimposed longitudinal and transverse crevasses in an extensive middle zone, and (iii) longitudinal crevasses in a narrow lower zone. The main difference between patterns produced by successive surges was small variations in the extent оf the three zones. During quiescence, the most intense crevasse development occurs in the upper glacier in the latter part of quiescence, and is a function of increasingly steep down-glacier velocity gradients developing in the buildup to the impending surge. Some crevassing also develops in the central part of the glacier in mid-quiescence that is not related to the surge nature of the glacier, but to normal flow processes over bedrock. There is no structural evidence to indicate that any of the tributaries of Variegated Glacier surge. This observation suggests that the bulb-like loops in the medial moraines at Variegated Glacier form during quiescence as a result of the steady flow of the tributaries into the stagnant trunk glacier, rather than as a result of tributary surges.

Structural evolution of Variegated Glacier, Alaska, U.S.A., since 1948

AbstractАn excellent photographic database, comprising 12 sets of vertical aerial photographs taken between 1948 and 1993, has enabled the structural glaciology of surge-type Variegated Glacier, Alaska, U.S.A., tо be analyzed for a period that spans two surge cycles and includes the effects of three surges. The glacier-wide patterns of crevasse development at the end of each of these surges, which occurred in 1947–48, 1964–65 and 1982–83, were remarkably similar, despite differences in surge intensities and extents. At the end of each surge a three-fold longitudinal zonation of crevasse orientation characterised that part of the glacier that had been affected by surge activity. This zonation comprises: (i) transverse crevasses in a narrow upper zone, (ii) superimposed longitudinal and transverse crevasses in an extensive middle zone, and (iii) longitudinal crevasses in a narrow lower zone. The main difference between patterns produced by successive surges was small variations in the extent оf the three zones. During quiescence, the most intense crevasse development occurs in the upper glacier in the latter part of quiescence, and is a function of increasingly steep down-glacier velocity gradients developing in the buildup to the impending surge. Some crevassing also develops in the central part of the glacier in mid-quiescence that is not related to the surge nature of the glacier, but to normal flow processes over bedrock. There is no structural evidence to indicate that any of the tributaries of Variegated Glacier surge. This observation suggests that the bulb-like loops in the medial moraines at Variegated Glacier form during quiescence as a result of the steady flow of the tributaries into the stagnant trunk glacier, rather than as a result of tributary surges.

The thermal regime of sub-polar glaciers mapped by multi-frequency radio-echo sounding

AbstractRadio-echo soundings provide an effective tool for mapping the thermal regimes of polythermal glaciers on a regional scale. Radar signals of 320–370 MHz penetrate ice at sub-freezing temperatures but are reflected from the top of layers of ice which are at the melting point and contain water. Radar signals of 5–20 MHz, on the other hand, see through both the cold and the temperate ice down to the glacier bed. Radio-echo soundings at these frequencies have been used to investigate the thermal regimes of four polythermal glaciers in Svalbard: Kongsvegen, Uvérsbreen, Midre Lovénbreen and Austre Brøggerbreen. In the ablation area of Kongsvegen, a cold surface layer (50–160 m thick) was underlain by a warm basal layer which is advected from the temperate accumulation area. The surface ablation of this cold layer may be compensated by freezing at its lower cold-temperate interface. This requires that the free water content in the ice at the freezing interface is about 1 % of the volume. The cold surface layer is thicker beneath medial moraines and where cold-based hanging glaciers enter the main ice stream. On Uvérsbreen the thermal regime was similar to that of Kongsvegen. A temperate hole was found in the otherwise cold surface layer of the ablation area in a surface depression between Kongsvegen and Uvérsbreen where meltwater accumulates during the summer (near the subglacial lake Setevatnet, 250 m a.s.l.). Lovénbreen w as frozen to the bed at the snout and along all the mountain slopes but beneath the central part of the glacier a warm basal layer (up to 50 m thick) was fed by temperate ice from two cirques. On Austre Brøggerbreen, a temperate basal layer was not detected by radio-echo soundings but the basal ice was observed to be at the melting point in two boreholes.

The thermal regime of sub-polar glaciers mapped by multi-frequency radio-echo sounding

AbstractRadio-echo soundings provide an effective tool for mapping the thermal regimes of polythermal glaciers on a regional scale. Radar signals of 320–370 MHz penetrate ice at sub-freezing temperatures but are reflected from the top of layers of ice which are at the melting point and contain water. Radar signals of 5–20 MHz, on the other hand, see through both the cold and the temperate ice down to the glacier bed. Radio-echo soundings at these frequencies have been used to investigate the thermal regimes of four polythermal glaciers in Svalbard: Kongsvegen, Uvérsbreen, Midre Lovénbreen and Austre Brøggerbreen. In the ablation area of Kongsvegen, a cold surface layer (50–160 m thick) was underlain by a warm basal layer which is advected from the temperate accumulation area. The surface ablation of this cold layer may be compensated by freezing at its lower cold-temperate interface. This requires that the free water content in the ice at the freezing interface is about 1 % of the volume. The cold surface layer is thicker beneath medial moraines and where cold-based hanging glaciers enter the main ice stream. On Uvérsbreen the thermal regime was similar to that of Kongsvegen. A temperate hole was found in the otherwise cold surface layer of the ablation area in a surface depression between Kongsvegen and Uvérsbreen where meltwater accumulates during the summer (near the subglacial lake Setevatnet, 250 m a.s.l.). Lovénbreen w as frozen to the bed at the snout and along all the mountain slopes but beneath the central part of the glacier a warm basal layer (up to 50 m thick) was fed by temperate ice from two cirques. On Austre Brøggerbreen, a temperate basal layer was not detected by radio-echo soundings but the basal ice was observed to be at the melting point in two boreholes.

Flow regime of the Lambert Glacier-Amery Ice Shelf system, Antarctica: structural evidence from Landsat imagery

High-resolution visible and near-infrared satellite imagery provides a means of investigating the structural glaciology, and in turn the dynamics, of large ice masses. The Lambert Glacier-Amery Ice Shelf system is one of the largest ice drainage basins in Antarctica and has previously yielded conflicting evidence concerning its dynamic behaviour: either that the system has a propensity for surging or that it has a constant flow regime. Digital manipulation of Landsat imagery allows analysis of the structure of the glacier system, showing longitudinal foliation, medial moraines and crevasse patterns that provide no evidence of surging behavior during the residence time of ice in the glacier system.

Flow regime of the Lambert Glacier-Amery Ice Shelf system, Antarctica: structural evidence from Landsat imagery

High-resolution visible and near-infrared satellite imagery provides a means of investigating the structural glaciology, and in turn the dynamics, of large ice masses. The Lambert Glacier-Amery Ice Shelf system is one of the largest ice drainage basins in Antarctica and has previously yielded conflicting evidence concerning its dynamic behaviour: either that the system has a propensity for surging or that it has a constant flow regime. Digital manipulation of Landsat imagery allows analysis of the structure of the glacier system, showing longitudinal foliation, medial moraines and crevasse patterns that provide no evidence of surging behavior during the residence time of ice in the glacier system.

Flow regime of the Lambert Glacier-Amery Ice Shelf system, Antarctica: structural evidence from Landsat imagery

High-resolution visible and near-infrared satellite imagery provides a means of investigating the structural glaciology, and in turn the dynamics, of large ice masses. The Lambert Glacier-Amery Ice Shelf system is one of the largest ice drainage basins in Antarctica and has previously yielded conflicting evidence concerning its dynamic behaviour: either that the system has a propensity for surging or that it has a constant flow regime. Digital manipulation of Landsat imagery allows analysis of the structure of the glacier system, showing longitudinal foliation, medial moraines and crevasse patterns that provide no evidence of surging behavior during the residence time of ice in the glacier system.

Debris in tills and moraines as a source of glaciological and palaeoenvironmental information: methodology and applications in the Caucasus

In the central Caucasus, the analysis of sedimentological data has revealed reliable diagnostic criteria for the identification of debris originating from different sources and transported under different glaciodynamic environments. In particular, the sharp contrast between debris transported supraglacially and by basal transport has been recognized. Fundamentally different pathways are followed by the debris transported from the surrounding slopes and from the glacier bed. Investigation of glacial deposits, represented by terminal, lateral and medial moraines, has revealed the prevalence of rock fragments derived from the interaction of glaciers with their beds. Temperate glaciers bring about considerable erosion of their beds, a conclusion that challenges concepts that emphasize the relief- preserving influence of such glaciers. It has also proved possible to determine the location of the zone of greatest erosion beneath the recent Caucasian glaciers and to determine its dynamics during the various stages of the Holocene.

A geochemical sampling technique for use in areas of active alpine glaciation: an application from the central Alaska Range

In mountainous regions containing extensive glacier systems there is a lack of suitable material for conventional geochemical sampling. As a result, in most geochemical sampling programs a few stream-sediment samples collected at, or near, the terminus of valley glaciers are used to evaluate the mineral potential of the glaciated area. We have developed and tested a technique which utilizes the medial moraines of valley glaciers for systematic geochemical exploration of the glacial catchment area. Moraine sampling provides geochemical information that is site-specific in that geochemical anomalies can be traced directly up-ice to bedrock sources. Traverses were made across the Trident and Susitna glaciers in the central Alaska Range where fine-grained (clay to sand size) samples were collected from each medial moraine. These samples were prepared and chemically analyzed to determine the concentration of specific elements. Fifty pebbles were collected at each moraine for archival purposes and for subsequent lithologic identification. Additionally, fifty cobbles and fifty boulders were examined and described at each sample site to determine the nature and abundance of lithologies present in the catchment area, the extent and nature of visible mineralization, the presence and intensity of hydrothermal alteration and the existence of veins, dikes and other minor structural features. Results from the central Alaska Range have delineated four distinct multi-element anomalies which are a response to potential mineralization up-ice from the medial moraine traverse. By integrating the lithologic, mineralogical and geochemical data the probable geological setting of the geochemical anomalies is determined.