Lateral Moraines Research Articles

Luminescence chronology and climatic implication of the late quaternary glaciation in the Nubra valley, Karakoram Himalaya, India

The present study investigates moraines, outwash gravel terraces, relict lake deposits and alluvial fans to reconstruct the pattern of glacier advances and associated climate variability in the Nubra Valley, Karakoram Himalaya, India. Optical chronologies obtained on stratigraphically constrained lateral moraines indicate that the oldest preserved record of glacier advance (Tirith-II) is dated to 60.4 ± 5.2 ka and corresponds to Marine Isotopic Stage-4 (MIS-4). During MIS-4, the Nubra valley was occupied by ~700 m thick ice cover that extended beyond the Nubra-Shyok confluence. It was followed by pulsating decrease in the ice-volume (vertical shrinking) with an insignificant lateral recession that continued until around 42.0 ± 3.0 ka (mid- MIS-3). The second major glacial advance (Tirith-I) is dated to 30 ± 2.5 ka (beginning of MIS-2) when the Siachen glacier reached up to the Nubra-Shyok confluence albeit, with lesser ice thickness (~300 m). The Tirith-I glacier advance continued to occupy the entire Nubra valley until around 18.2 ± 1.8 ka (Last Glacial Maximum). A deglaciation followed after 15.8 ± 1.6 ka and continued until the early Holocene (10.3 ± 1.3 ka). The third minor glacial advance-Siachen Glacial Advance (SGA) is dated to the mid-Holocene (6.8 ± 1.0/7.2 ± 1.4 ka) when the glacier extended below the Siachen glacier snout, whereas the youngest glacial expansion reached a few hundred meters below the present day snout and is dated between 1.0 ± 0.4 ka and 0.5 ± 0.2 ka.The study suggests that glacier advances were driven by a decrease in temperature with corresponding increase in the moisture contribution due to the enhanced mid-latitude westerlies during MIS-4, MIS-2, and the mid-Holocene. Within the age uncertainty, it can be suggested that the snout-proximal recessional moraines indicate marginal glacier expansion during the Little Ice Age (LIA). Following this, the glacier receded to its present position and seems to have stabilized since then. Unlike other Himalayan glaciers, the Siachen glacier does not show any alarming retreat after the LIA and is in conformity with recent observations suggesting that the glaciers in Karakoram region are either marginally advancing or stand still.

Valley glaciers persisted in the Lake District, north‐west England, until ∼16–15 ka as revealed by terrestrial cosmogenic nuclide (10Be) dating: a response to Heinrich event 1?

ABSTRACTThe Lake District of north‐west England acted as an independent centre of ice dispersal within the more extensive British–Irish Ice Sheet (BIIS) during the Last Glacial Maximum, but relatively little is known about the pattern and timing of glacier retreat. Four new terrestrial cosmogenic nuclide (10Be) surface exposure ages from boulders from a lateral moraine in the Duddon valley, south‐west Lake District, have yielded internally consistent ages with uncertainty‐weighted means of 16.51 ± 0.78 ka (using the Loch Lomond production rate with Lm scaling and 1 mm ka−1 erosion rate) and 16.15 ± 1.30 ka (using CRONUScalc with SA scaling and 1 mm ka−1 erosion rate). It is inferred that glacier retreat from the moraine occurred in the interval ∼16.5–16.1 ka but that a valley glacier continued to exist, probably until ∼15 ka. The Duddon valley ages agree with other surface exposure ages from Wasdale, Watendlath and the Shap fells, together demonstrating that glacier ice was still widespread in the Lake District at ∼17–15 ka. There is also consistency with ages from other sectors of the BIIS that are considered to have responded to North Atlantic Heinrich event 1.

Last Glacial Maximum and Lateglacial in the Polish High Tatra Mountains - Revised deglaciation chronology based on the 10Be exposure age dating

Deglaciation chronology of the Polish High Tatra Mountains has been reconstructed based on 10Be exposure age dating. Fifty-seven rock samples were collected from boulders located on the terminal and lateral moraines that limit the horizontal extent of the LGM and the Lateglacial glaciers in the Biała Woda and Sucha Woda catchments. The uncertainty-weighted mean age of 21.5 ± 2.5 ka obtained for the maximum terminal moraine in the Sucha Woda Valley indicates that the oldest preserved moraines were formed during the global LGM. The age population ranges between 15.1 ± 1.0 and 28.3 ± 2.0 ka, and suggests that glaciers reached their maximum position (LGM I) as early as 28–25 ka and the final stabilization of the form occurred much later possibly after melting of buried dead ice. The younger glacial oscillation (LGM II) occurred no later than 20.5 ka and is represented by well-preserved termino-lateral moraine systems in the Pańszczyca Valley. The first Lateglacial stage (LG1) in the study area is documented in the Rybi Potok Valley at the RP1 moraine (1300 m a.s.l.), which was stable at around 16.6 ± 0.3 ka. The younger LG2 stage has no defined absolute age, however, it is constrained between 16.5 and 15.5 ka by the timing of the LG3 stage. This cold event is represented by well-formed moraines in the Roztoka/Pięć Stawów Polskich, Rybi Potok and Pańszczyca valleys of which exposure age indicates their deposition between 15.0 ± 0.5 and 15.6 ± 0.1 ka. The LG1, LG2 and LG3 stages likely occurred during the Oldest Dryas cold stage (Greenland Stadial 2.1a) related to the North Atlantic cooling Heinrich Event 1. The youngest glacial oscillation is evidenced by moraines in the Pusta and Pańszczyca valleys. These moraines are composed of very large granitic blocks of which exposure ages often exhibit isotope inheritance. This is reflected by the youngest P3 moraine in the Pańszczyca Valley with a mean age of deposition close to the LGM. The R4 moraine system in the Pusta Valley, however, indicates two oscillations phases that occurred at around 13 ka and correlates well with the timing of RP5 moraine formation in the Za Mnichem Valley. The LG4 stage is related to the climate cooling during the Younger Dryas (Greenland Stadial 1).LGM ELAs reconstructed for the Biała Woda and Sucha Woda/Pańszczyca glaciers were located at 1460–1480 m a.s.l. During the Oldest Dryas stages, the ELA in the High Tatras rose from 1600 to 1650 m a.s.l. in the Rybi Potok Valley and from 1700 to 1800 m a.s.l. in the Roztoka/Pięć Stawów Polskich Valley. The Younger Dryas ELA, depending on glacier's exposition, was located between 1950 and 2000 m a.s.l. Climate modelling results show that the LGM glaciers (maximum advance) could have advanced in the High Tatras when the mean annual temperature was lower than today by 11–12 °C and precipitation was reduced by 40–60%. During the Lateglacial stages the temperature decrease in the study area changed from 10 °C during the Oldest Dryas to 6 °C during the Younger Dryas and precipitation lowering decreased from −50% to −30% or even −10%, respectively compare to modern conditions.

Evidence for slow late-glacial ice retreat in the upper Rangitata Valley, South Island, New Zealand

A suite of cosmogenic radionuclide ages taken from boulders on lateral and latero-terminal moraines in the Rangitata Valley, eastern South Island, New Zealand demonstrates that relatively thick ice occupied valley reaches inland of the Rangitata Gorge until c. 21 ka. Thereafter ice began to thin, and by c. 17 ka it had retreated 33 km up-valley of the Rangitata Gorge to the Butler-Brabazon Downs, a structurally created basin in the upper Rangitata Valley. Despite its magnitude, this retreat represents a minor ice volume reduction from 21 ka to 17 ka, and numerous lateral moraines preserved suggest a relatively gradual retreat over that 4 ka period. In contrast to records from adjacent valleys, there is no evidence for an ice-collapse at c. 18 ka. We argue that the Rangitata record constitutes a more direct record of glacial response to deglacial climate than other records where glacial dynamics were influenced by proglacial lake development, such as the Rakaia Valley to the North and the major valleys in the Mackenzie Basin to the south-west. Our data supports the concept of a gradual warming during the early deglaciation in the South Island New Zealand.

Glaciolacustrine deposits formed in an ice-dammed tributary valley in the south-central Pyrenees: New evidence for late Pleistocene climate

Combined geomorphic features, stratigraphic characteristics and sedimentologic interpretation, coupled with optically stimulated luminescence (OSL) dates, of a glacio-fluvio-lacustrine sequence (Linás de Broto, northern Spain) provide new information to understand the palaeoenvironmental significance of dynamics of glacier systems in the south-central Pyrenees during the Last Glacial Cycle (≈130 ka to 14 ka). The Linás de Broto depositional system consisted of a proglacial lake fed primarily by meltwater streams emanating from the small Sorrosal glacier and dammed by a lateral moraine of the Ara trunk glacier. The resulting glacio-fluvio-lacustrine sequence, around 55 m thick, is divided into five lithological units consisting of braided fluvial (gravel deposits), lake margin (gravel and sand deltaic deposits) and distal lake (silt and clay laminites) facies associations. Evolution of the depositional environment reflects three phases of progradation of a high-energy braided fluvial system separated by two phases of rapid expansion of the lake. Fluvial progradation occurred during short periods of ice melting. Lake expansion concurred with ice-dam growth of the trunk glacier. The first lake expansion occurred over a time range between 55 ± 9 ka and 49 ± 11 ka, and is consistent with the age of the Viu lateral moraine (49 ± 8 ka), which marks the maximum areal extent of the Ara glacier during the Last Glacial Cycle. These dates confirm that the maximum areal extent of the glacier occurred during Marine Isotope Stages 4 and 3 in the south-central Pyrenees, thus before the Last Glacial Maximum. The evolution of the Linás de Broto depositional system during this maximum glacier extent was modulated by climate oscillations in the northern Iberian Peninsula, probably related to latitudinal shifts of the atmospheric circulation in the southern North-Atlantic Ocean, and variations in summer insolation intensity.

Computing spatially distributed sediment delivery ratios: inferring functional sediment connectivity from repeat high‐resolution digital elevation models

AbstractHigh‐resolution digital elevation models (DEMs) from repeat LiDAR (light detection and ranging) or SfM (structure from motion) surveys have become an important tool in process geomorphology. The spatial pattern of negative and positive changes of surface elevation on raster DEMs of difference (DoD) can be interpreted in terms of geomorphic processes, and has been used for morphological budgeting. We show how the application of flow routing algorithms and flow accumulation opens new opportunities for the analysis of DoD. By accumulating the values of the DoD along downslope flowpaths delineated on a DEM, these algorithms lend themselves to computing the net balance, i.e. sediment yield (SY), for the contributing area of each cell. Doing the same for the negative subset of the DoD yields a minimum estimate of erosion (E) within the contributing area. The division of SY by E yields (a maximum estimate of) the sediment delivery ratio (SDR), that is the proportion of material eroded within the contributing area of each cell that has been exported from that area. The resulting SDR is a spatially distributed measure of functional sediment connectivity. In this letter, we develop the computationally simple approach by means of an example DoD from a lateral moraine section in the Upper Kaunertal Valley, Austrian Central Alps. We also discuss advantages, assumptions and limitations, and outline potential applications to connectivity research using field‐, laboratory‐, and model‐based DoD. Copyright © 2018 John Wiley & Sons, Ltd.

Nonlocal Sediment Transport on Steep Lateral Moraines, Eastern Sierra Nevada, California, USA

Recent work has highlighted the significance of long‐distance particle motions in hillslope sediment transport. Such motions imply that the flux at a given hillslope position is appropriately described as a weighted function of surrounding conditions that influence motions reaching the given position. Although the idea of nonlocal sediment transport is well grounded in theory, limited field evidence has been provided. We test local and nonlocal formulations of the flux and compare their ability to reproduce land surface profiles of steep moraines in California. We show that nonlocal and nonlinear models better reproduce evolved land surface profiles, notably the amount of lowering and concavity near the moraine crest and the lengthening and straightening of the depositional apron. The analysis provides the first estimates of key parameters that set sediment entrainment rates and travel distances in nonlocal formulations and highlights the importance of correctly specifying the entrainment rate when modeling land surface evolution. Moraine evolution associated with nonlocal and nonlinear transport formulations, when described in terms of the evolution of the Fourier transform of the moraine surface, displays a distinct behavior involving growth of certain wave numbers, in contrast to the decay of all wave numbers associated with linear transport. Nonlinear and nonlocal formulations share key mathematical elements yielding a nonlinear relation between the flux and the land surface slope.

The glaciated valley landsystem of Morsárjökull, southeast Iceland

ABSTRACTA 1:4470 map of the Morsárjökull foreland, southern Iceland shows the spatial distribution of post Little Ice Age glacial sediment–landform associations pertaining to the operation of a typical active temperate outlet glacier of the south Vatnajökull ice cap. The map depicts an exemplar for the debris-charged glaciated valley landsystem, with characteristics further indicative of ‘uncovered alpine glaciers’, such as the uneven distribution of moraine volume, the localized appearance of a fluted subglacial bed and within-valley lateral moraine asymmetry. Such glaciers are characterized by strong glacier-climate coupling, because temporally and spatially sporadic rock avalanche-type medial moraines can only locally retard ablation. This morainic debris also has a short residence time in the glacier system due to its strong coupling with the proglacial fluvial system and resulting in efficient sediment transfer. Areas of more substantial latero-frontal moraine document phases of rock slope failure onto the snout and the passage of the debris to the ice margin.

Re‐evaluation of MIS 3 glaciation using cosmogenic radionuclide and single grain luminescence ages, Kanas Valley, Chinese Altai

ABSTRACTPrevious investigations observed a period of major glacial advances in Central Asia during marine oxygen isotope stage (MIS) 3 (57–29 ka), out of phase with global ice volume records. We have re‐examined the Kanas moraine complex in the Altai Mountains of Central Asia, where an MIS 3 glaciation had been previously inferred. New and consistent cosmogenic exposure and single‐grain luminescence ages indicate that the Kanas complex was formed during MIS 2 (29–12 ka), which brings its timing in line with the global ice volume record. We also identified a lateral moraine from a more extensive ice extent that dates to late MIS 5/MIS 4. To place our results in a wider contextual framework, we review the chronologies of another 26 proposed major MIS 3 glacial advances in Central Asia. For most of these sites, we find that the chronological data do not provide an unequivocal case for MIS 3 glaciation.

Ice-dammed lateral lake and epishelf lake insights into Holocene dynamics of Marguerite Trough Ice Stream and George VI Ice Shelf, Alexander Island, Antarctic Peninsula

We present new data regarding the past dynamics of Marguerite Trough Ice Stream, George VI Ice Shelf and valley glaciers from Ablation Point Massif on Alexander Island, Antarctic Peninsula. This ice-free oasis preserves a geological record of ice stream lateral moraines, ice-dammed lakes, ice-shelf moraines and valley glacier moraines, which we dated using cosmogenic nuclide ages. We provide one of the first detailed sediment-landform assemblage descriptions of epishelf lake shorelines. Marguerite Trough Ice Stream imprinted lateral moraines against eastern Alexander Island at 120 m at Ablation Point Massif. During deglaciation, lateral lakes formed in the Ablation and Moutonnée valleys, dammed against the ice stream in George VI Sound. Exposure ages from boulders on these shorelines yielded ages of 13.9 to 9.7 ka. Following recession of the ice stream, George VI Ice Shelf formed in George VI Sound. An epishelf lake formed at 15–20 m asl in Ablation and Moutonnée valleys, dated from 9.4 to 4.6 ka, suggesting that the lake was stable and persistent for some 5000 years. Lake-level lowering occurred after this, with the lake level at 12 m at 3.1 ± 0.4 ka and at 5 m asl today. A readvance of the valley glaciers on Alexander Island at 4.4 ± 0.7 ka is recorded by valley glacier moraines overlying epishelf lake sediments. We speculate that the glacier readvance, which occurred during a period of warmth, may have been caused by a dynamic response of the glaciers to a lowering in surface elevation of George VI Ice Shelf.

Impact of impurities and cryoconite on the optical properties of the Morteratsch Glacier (Swiss Alps)

Abstract. The amount of reflected energy by snow and ice plays a fundamental role in their melting processes. Different non-ice materials (carbonaceous particles, mineral dust (MD), microorganisms, algae, etc.) can decrease the reflectance of snow and ice promoting the melt. The object of this paper is to assess the capability of field and satellite (EO-1 Hyperion) hyperspectral data to characterize the impact of light-absorbing impurities (LAIs) on the surface reflectance of ice and snow of the Vadret da Morteratsch, a large valley glacier in the Swiss Alps. The spatial distribution of both narrow-band and broad-band indices derived from Hyperion was analyzed in relation to ice and snow impurities. In situ and laboratory reflectance spectra were acquired to characterize the optical properties of ice and cryoconite samples. The concentrations of elemental carbon (EC), organic carbon (OC) and levoglucosan were also determined to characterize the impurities found in cryoconite. Multi-wavelength absorbance spectra were measured to compare the optical properties of cryoconite samples and local moraine sediments. In situ reflectance spectra showed that the presence of impurities reduced ice reflectance in visible wavelengths by 80–90 %. Satellite data also showed the outcropping of dust during the melting season in the upper parts of the glacier, revealing that seasonal input of atmospheric dust can decrease the reflectance also in the accumulation zone of the glacier. The presence of EC and OC in cryoconite samples suggests a relevant role of carbonaceous and organic material in the darkening of the ablation zone. This darkening effect is added to that caused by fine debris from lateral moraines, which is assumed to represent a large fraction of cryoconite. Possible input of anthropogenic activity cannot be excluded and further research is needed to assess the role of human activities in the darkening process of glaciers observed in recent years.

Reconstruction and paleoclimatic significance of late Quaternary glaciers in the Tararua Range, North Island, New Zealand

Reconstructed mountain glaciers are routinely used as a proxy for climate in the search for evidence of interhemispheric climate fluctuations during the Quaternary. In New Zealand, valley glaciers at the Last Glacial Maximum (LGM) extended from an ice sheet centred on New Zealand's Southern Alps to below present-day sea level. In contrast, evidence of LGM glacial activity on the North Island is rare. Here, a glacioclimatic reconstruction is presented of two former glaciers in the Tararua Range (41°S) in the southern North Island. At Mt. Aston, an isolated cirque basin contains landform evidence of a marginal niche glacier. At Park Valley, the lateral moraine of a larger cirque glacier has yielded published cosmogenic isotope ages. The paleoglacier reconstruction shows that paleoequilibrium line altitudes increased northwards across New Zealand during the local LGM. Hence, at this latitude only topography >1200 m above present day sea-level was of sufficient elevation to allow small glaciers to form. The Mt Aston glacier covered only 0.18 km2 with an equilibrium line altitude (ELA) of c. 1287 m above present sea level. A mean ELA glacier thickness of c. 25 m gives a basal shear stress at the ELA of c. 100 kPa−1, with a mean summer (December, January, February, DJF) temperature at the ELA of no lower than 5.5 °C below present, below which precipitation would have been insufficient to support the reconstructed glacier. Implied LGM paleo-temperatures from both the ELA reconstruction and the glaciological reconstruction broadly accord with other paleo-temperature proxies from the North Island. Park Valley glacier covered c. 0.45 km2 with an ELA of c. 1270 m and a mean ELA basal shear stress of 65 kPa. Its balance discharge was 9 × greater than at Mt Aston. It appears to have been glaciologically viable across a wide range of paleotemperatures: thus, the more marginal glacier is a more useful paleoclimatic indicator because it places a maximum limit on LGM temperature depression, which the larger glacier does not. ELAs of both glaciers closely approximate the regional LGM ELA trend surface. The paleo-glacier reconstructions imply that together with temperature driving LGM paleo-ELA depression, changes in south-westerly airflow over New Zealand, bringing moisture-laden but cool air, maximized snowfall and minimised winter melt. The corollary is that patterns of Quaternary glacier fluctuations may be interpreted as responses, at least in-part, to precipitation-driven changes, and secondly, North Island glaciation was probably more extensive than previously assumed.

Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene

Glacial retreat from the North Cascade Range after the Last Glacial Maximum (LGM) at approximately 21 ka until the end of the Pleistocene at 11.6 ka was complex and included both continental and alpine glaciers. Alpine valley glaciers reached their maximum extent before 21.4 ka, then underwent a punctuated retreat to valley heads. In the south, beyond the reach of ice sheet glaciation, several end moraines were deposited after the LGM. Moraines marking a re-advance of alpine glaciers to <5 km below modern glaciers were deposited from 13.7 to 11.6 ka.The Cordilleran Ice Sheet flowed south from near 52° north latitude in British Columbia into the North Cascades. At its maximum size the ice sheet covered more than 500 km2 and had a surface elevation of 2200 m in upper Skagit valley. Deglaciation commenced about 16 ka by frontal retreat of ice flanking the mountains. Surface lowering eventually exposed regional hydrologic divides and stranded ice masses more than 1000 m thick in valleys. Isolated fragments of the ice sheet disintegrated rapidly from 14.5 to 13.5 ka, with the pattern of deglaciation in each valley controlled by valley orientation, topography, and climate. Like alpine glaciers to the south, retreat of the ice sheet remnants was slowed by millennial scale climate fluctuations that produced at least one large recessional moraine, and multiple lateral moraines and kame terraces from elevations of 200-1400 m in most valleys. Large volumes of glacial meltwater flowed through the North Cascades and was concentrated in the Skagit and Methow rivers. Outburst floods from deep proglacial lakes spilled across divides and down steep canyons, depositing coarse gravel terraces and alluvial fans at valley junctions.Climate at the LGM was characterized by a mean summer temperature 6 to 7 ºC cooler than today, and 40% lower mean annual precipitation. Persistence of this climate for thousands of years before the LGM caused a 750-1000 m decrease in alpine glacier equilibrium line altitudes (ELA). In the southern North Cascades at 16 ka, glacial ELAs were 500-700 m lower than today, and during advances from 13.7 to 11.6 ka alpine glacier ELAs were 200-400 m lower.

Late glacial and post-glacial deposits of the Navamuño peatbog (Iberian Central System): Chronology and paleoenvironmental implications

The Navamuño peatbog (Sierra de Béjar, western Spain) is a ∼14 ha pseudo-endorheic depression with boundaries defined by a lateral moraine of the Cuerpo de Hombre paleoglacier and fault-line scarps on granite bedrock. The stratigraphy of the Navamuño peatbog system is characterized here using borehole data to a depth of 20 m. An integrated interpretation from direct-push coring, dynamic probing boreholes and handheld auger drillings advances our knowledge of the Navamuño polygenetic infill. Correlating this data with those obtained in other studies of the chronology and evolutionary sequence of the Cuerpo de Hombre paleoglacier has enabled us to establish the sequence of the hydrological system in the Navamuño depression. During the Late Pleistocene (MIS2), the depression was dammed by the Cuerpo de Hombre glacier and fed by its lateral meltwaters, and was filled with glaciolacustrine deposits. The onset of the Holocene in Navamuño is linked to a flat, fluviotorrential plain with episodes of local shallow pond/peat bog sedimentation. This evolutionary sequence is congruent with the age model obtained from available radiocarbon dating, obtaining 19 ages from ∼800 cal yr BP (at depth 1.11 m) to ∼16800 cal yr BP (at depth 15.90–16.0 m). Finally, the sedimentary record enabled interpretation of the environmental changes occurring in this zone during the late glacial (from the Older Dryas to the Younger Dryas) and postglacial (Holocene) stages, placing them within the paleoclimatic context of the Iberian Peninsula and Mediterranean regions.

Soil and landform interplay in the dry valley of Edson Hills, Ellsworth Mountains, continental Antarctica

The main relief units from the dry valley of Edson Hills, Ellsworth Mountains, Antarctica (79°49′12.4″/83°40′16.1″), were assessed, emphasizing the analysis of soil and landform interplay. Soil morphological, physical, and chemical properties; salinity; surface boulder weathering (frequency and feature); classification; and weathering stages were analyzed. Three distinct landforms summarize the geomorphology of the dry valley of Edson Hills, Ellsworth Mountains: (i) periglacial features like slightly creeping debris-mantled slopes, steep debris-mantled slopes, patterned grounds, and thermokarst; (ii) glacial features like hummocky moraines, lateral moraines (supraglacial), lakes, kettle hole (proglacial), cirques infill (subglacial), horn, and arête (erosional glacial); and (iii) nonglacial features like scree slopes and talus deposits. All these glacial and periglacial features are related to the West Antarctica ice sheet variations. Soils in the dry valley of Edson Hills are pedologically poorly developed. However, the degree of development in soils associated with patterned ground and moraine systems is remarkable. All soils present desert pavement owing to the action of severe aeolian erosion. In addition, soils accumulate salts depending on the local drainage conditions. The most expressive soil classes among the studied soils were Typic Haploturbel and Typic Anhyorthel, especially because of: (i) a general trend of ice-cemented permafrost occurrence in lower portions of the landscape, particularly in the patterned ground area and in the hummocky moraine; and (ii) the presence of dry permafrost in higher positions of the landscape, in relief units such as in debris-mantled slopes and talus deposits. Thus, a close relationship among soil characteristics and landforms were observed in the dry valley of Edson Hills.

Glacial geomorphology of the Brabazon & Butler Downs, Rangitata Valley, South Island, New Zealand

ABSTRACTThe inland valleys of New Zealand’s South Island were heavily glaciated during the last glacial cycle. Subsequent fluvial incision has eroded out glacial deposits from the valleys in many locations, making it difficult to reconstruct glacial dynamics and chronology. The Brabazon and Butler Downs lie in a fault-controlled intra-montaine basin that has been largely protected from fluvial erosion and the area contains extensive evidence for multiple glacial margins. This paper presents a detailed glacial geomorphology map of the Brabazon and Butler Downs at a scale of 1:20,000. Glacial landforms have been mapped and subdivided into three main zones: an upper zone distinguished by a flight of kame terraces, a middle zone containing kettles and meltwater channels, and a lower zone of lateral moraines. The new map provides insight into former glacial environments in the region and provides a related framework for future paleoclimate reconstructions.

Glacial-geomorphic study of the Thajwas glacier valley, Kashmir Himalayas, India

Glacial-geomorphic studies provide vital information to make inferences about the effect of glacial advance and retreat on the geomorphology of an area. In the present study, glacial-geomorphic landforms of the Thajwas glacial valley in the upper reaches of the Indus, Kashmir Himalayas were mapped using geospatial technology validated with GPS-based field observations and ground photography. The glacial-geomorphic landforms were digitized using ASTER DEM (30 m resolution), Landsat ETM+ satellite imagery (30 m resolution) and Google Earth (1 m resolution) data. Results showed that Google Earth imagery, supported by field validation, is very useful for the interpretation of glacial-geomorphic landscapes and relief features at micro- and meso-scales. However, morphometric characteristics of landforms are best obtained using DEM overlaid onto the Landsat ETM+ satellite data. Glaciers in the valley are presently confined along the south and southwestern slopes. However, the significant role played by glaciers in shaping the geomorphic landforms and their subsequent preservation within the scenic landscape under the Late Quaternary climatic conditions are remarkably evident. The glacial-geomorphic landforms, especially terminal moraine, glacial trough and cirques observed in the valley aided the reconstruction of palaeo-glacial setting of the area. Morphology, shape and location of terminal and lateral moraine ridges were used to establish the palaeo-glacial extents, glacial volume and the number of glacial advances of the Thajwas glacier. The maximum elevation of the lateral moraines was used to define the former Equilibrium-Line Altitude (ELA). The greater rock excavation to form a large valley during the last glacial maximum might have induced isostatic rock uplift/exhumation in the glacier source area. It is observed that the concomitant retreat of the north-facing glacial cirques has played an important role in expanding the glacial valley and limiting the topographic relief.

The recent deglaciation of Kolahoi valley in Kashmir Himalaya, India in response to the changing climate

In the present study, the retreat of Kolahoi glacier was mapped from the satellite observations and historical maps supplemented by the extensive field observations to understand the recent deglaciation of the Kolahoi valley, Kashmir Himalaya, India. The glacier has retreated by 2.85km during the last 157years from 1857 to 2014 with an average retreat of about 18.2myear−1; however, the glacier snout has shown higher recession during the last decade. The geomorphological evidence reveals glaciation of the Kolahoi valley during the Quaternary. These evidences include glacial till at Pahalgam and Aru besides terminal and lateral moraines at Lidderwat, Satlanjan and Kolahoi Gunj in the Kolahoi valley. The glacier has shrunk by 2.81km2 during the last 51years (1962–2013) losing an ice volume of 0.30km3. The observed glacier changes were correlated with the climate data from PMIP3-CMIP5 models. The temperatures are predicted to increase almost ten times more than that observed during the Last Glacial Maximum (LGM). The future temperature is predicted to rise between 0.18°C and 0.61°C per decade under RCP 2.6 and RCP 8.5 respectively. The projected rise in the temperature, if realized, will have an adverse effect on the glaciers and would, in all likelihood, adversely affect the water availability for various sectors in the region.

East Antarctic ice sheet stability recorded in a high-elevation ice-cored moraine

Till in an extensive blue ice moraine in the central Transantarctic Mountains at Mt. Achernar shows relatively continuous deposition by East Antarctic derived ice throughout the last glacial cycle. The most recently exposed material along the active margin of the Law Glacier (Zone 1) has hummocky topography that transitions into to a relatively flat region (Zone 2), followed by a series of ∼2 m high continuous, parallel/sub-parallel ridges and troughs (Zones 3–5). The entire moraine is ice-cored. Past surface changes of <40 m are indicated by a lateral moraine at the base of Mt. Achernar and substantial topographic relief across Zone 3.Pebble lithology and detrital zircon geochronology were analyzed on samples along a 6.5 km transect across the moraine which formed from sub- and englacial debris. Beacon and Ferrar Supergroup rocks comprise most rock types on the moraine surface. Overall, pebbles in Zones 1, 4 and 5 are dominated by igneous rocks of the Ferrar dolerite, whereas Zones 2 and 3 have ∼40% more Beacon Supergroup sedimentary rocks. Zone 4 is characterized by distinctly colored lithologic bands, 5–20 m wide, that alternate between dominant Beacon and Ferrar rock types. When combined with surface exposure ages, we conclude that Zones 2 and 3 contain sediment accumulated through the last glacial maximum (LGM). In contrast to pebble data, the U-Pb zircon data from till across all zones show little variability and are consistent with a Beacon Supergroup source, as samples show significant populations from the Proterozoic, ∼550–600 Ma and ∼950–1270 Ma, as well as the late Archean ∼2700–2770 Ma. The Mackellar, Fairchild, and lower Buckley Formations are interpreted as dominant sources of the detrital zircons. The zircon data lack the spatio-temporal variability indicated by the pebble fraction because the local Ferrar dolerite is not zircon bearing, highlighting the broader importance of using multiple techniques when interpreting provenance changes over time.Rather than reflecting major changes in ice flow path over time, the provenance changes are interpreted to indicate relative stability of the East Antarctic ice sheet, as the Law Glacier tapped into and eroded successively lower stratigraphic units of the Beacon Supergroup. This has important implications for interpreting offshore provenance records.

A Birds Eye View of Debris-Avalanche on Miyar Glacier, Chenab Basin, India

The importance of mass wasting in glacier environments and its impacts on glacier dynamics is not fully understood. This is the first occurrence of a debris avalanche event onto a Himalayan glacier through satellite data analysis. The analysis of various factors indicates the slide was a climate-driven hill-slope event activated in 2009 masking the Miyar glacier surface up to ~1.5% including its both lateral moraines and medial moraines. Due to this addition the glacier had neither advance nor retreat from 2009 to 2014. Eventually the debris will contribute to the supraglacial and englacial debris of the glacier. This showcases the way of mass wasting an important contribution to the debris budget of the Himalayan glaciers.