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Proglacial areas in the European Alps and other high-elevation mountains are currently undergoing rapid change due to global warming. Because of rising temperatures, glaciers and glacier forefields are subjected to increased melting and associated sediment export. This observation is increasingly important with respect to high-elevation geomorphological and ecological dynamics, emerging natural hazards and mitigation efforts, and hydropower plant management. It is therefore crucial to analyze the factors and feedback mechanisms governing sediment production, transport, and deposition in these rapidly changing areas. In this study, we investigated the sediment dynamics of a proglacial area located in the Eastern Italian Alps over the period 1969–2021 with the aims of: i) identifying the areas of sediment production; ii) quantifying volumes and rates of bedload sediment transport; and iii) determining the relative contribution of glacial export and fluvial erosion to the total sediment budget. We found that i) apart from glaciers, moraines and fluvial channels have been the most important sediment sources, albeit with substantial differences in terms of connectivity and thus supply rates; ii) the volumes and rates of sediment erosion varied by one order of magnitude (between tens and hundreds of mm per year), and were generally higher along the channel network; and iii) for a relatively shorter time interval between 2005 and 2021, the relative contribution of glacial bedload input with respect to the total sediment budget ranged between 34 % and 37 %, whereas 45 % to 59 % was derived from lateral fluvial erosion. Only a relatively small sediment volume was generated by net channel bed incision. These results imply that most of the sediment released from the proglacial area of the Sulden glacier is progressively transferred to the downstream sector of the channel network, with volumes that range between 931 and 1017 tons yr−1 km−2. These values are in the typical range of sediment export volumes from glaciated basins and highlight the high dynamicity of this region of the Alps. In general, our results confirm the complexity – in terms of spatial and temporal variability – of Alpine proglacial systems and highlight the need to systematically study these areas on a wide spatial and temporal scale, since the information provided by single locations or individual sectors of the sediment cascade, may not be adequate for understanding the dynamics acting in the entire proglacial regions. [Display omitted] • Proglacial areas change rapidly and supply sediment to the downstream valleys. • Moraines and channels are the most important sediment sources. • Glacial and fluvial erosion contribute between 35 % and 50 % to the sediment budget. • The proglacial area of the Sulden glacier is dominated by sediment transport. • In the Sulden region, sediment export may increase in the near future. [ABSTRACT FROM AUTHOR]

A digital database for submarine glacial landforms and sediments formed in the Arctic during and since the Last Glacial Maximum was created in order to facilitate and underpin new research on palaeo‐ice sheets and tidewater glacier dynamics. The glacimarine database (GlaciDat) documents and standardises evidence of previous glacial activity as visible on the contemporary seafloor of fjords and continental shelves around Svalbard, Greenland, Alaska, northern Russia and north of 66°30′N in Canada and Norway. An extensive literature search was conducted to create GlaciDat, which compiles nearly 60 000 individual submarine landforms, more than 1000 sediment cores and 232 radiocarbon dates. Glacial landforms included are cross‐shelf troughs, trough‐mouth fans, grounding‐zone wedges, lateral moraines, overridden moraines, (mega‐scale) glacial lineations, drumlins, crag‐and‐tails, medial moraines, terminal moraines, debris‐flow lobes (including glacier‐contact fans), recessional moraines, De Geer moraines, crevasse‐fill ridges, eskers, hill‐hole pairs, crescentic scours, and submarine channels. They were digitised as point, line and polygon features alongside a list of their individual characteristics. Sediment core locations are attributed with a description of the sampled lithofacies and sedimentation rates where available. Landforms and sediments have been standardised according to predefined nomenclatures to make the glacial evidence as consistent as possible. Marine radiocarbon dates were included when thought to be relevant for constraining the timing of large‐scale palaeo‐ice dynamics. Outlines of bathymetric data sets, which have previously been used for glacial geomorphological mapping, were also included to give an overview of already investigated research areas. GlaciDat is available for download (https://doi.pangaea.de/10.1594/PANGAEA.937782) and will aid researchers in the reconstruction of past ice dynamics and the interpretation of Arctic glacial landform–sediment assemblages. Moreover, as well as providing a comprehensive bibliography on Arctic glacial geomorphological and sedimentological research, it is intended to serve as a basis for future modelling of Arctic glacier and ice‐sheet dynamics. [ABSTRACT FROM AUTHOR]

The accelerated melting of ice on the Antarctic Peninsula and islands in the sub-Antarctic suggests that the cryosphere is edging towards an irreversible tipping point. How unusual is this trend of ice loss within the frame of natural variability, and to what extent can it be explained by underlying climate dynamics? Here, we present new high-resolution reconstructions of long-term changes in the extents of three glaciers on the island of South Georgia (54°S, 36°W), combining detailed analyses of glacial-derived sediments deposited in distal glacier-fed lakes and cosmogenic exposure dating of moraines. We document that the glaciers of South Georgia have gradually retracted since the Antarctic cold reversal (ACR, 14.5–12.8 ka), culminating in the disappearance of at least one of the reconstructed glaciers. The glacier retreat pattern observed in South Georgia suggests a persistent link to summer insolation at 55°S, which intensified during the period from the ACR to approximately 2 ka. It also reveals multi-decadal to centennial climate shifts superimposed on this long-term trend that have resulted in at least nine glacier readvances during the last 10.5 ka. Accompanying meridional changes in the Southern Hemisphere westerlies and their interconnection with local topography may explain these glacier readvances. [ABSTRACT FROM AUTHOR]

The recently-advancing Taku Glacier is excavating subglacial sediments at high rates over multi-decadal timescales. However, sediment redistribution over shorter timescales remains unquantified. We use a variety of methods to study subglacial and proglacial sediment redistribution on decadal, seasonal, and daily timescales to gain insight into sub- and proglacial landscape formation. Both excavation and deposition were observed from 2003 to 2015 (2.8 ± 0.9 m a−1 to +2.9 ± 0.9 m a−1). The observed patterns imply that a subglacial conduit has occupied the same site over the past decade. Outwash fans on the subaerial end moraine experience fluvial sediment reworking almost year-round, with net sediment gain in winter and net sediment loss in summer, and an overall mass gain between 2005 and 2015. We estimate that tens of meters of sediment still underlie the glacier terminus, sediments which can be remobilized during future activity. However, imminent retreat from the proglacial moraine will limit its sediment supply, leaving the moraine vulnerable to erosion by bordering rivers. Retreat into an over-deepened basin will leave the glacier vulnerable to increased frontal ablation and accelerating retreat. [ABSTRACT FROM AUTHOR]

The submarine landforms and shallow sediment record are presented from Hambergbukta, southeastern Spitsbergen using swath‐bathymetric, subbottom acoustic, and sediment core data. The mapped landforms include large terminal and end‐moraines with associated debrisflow aprons on their distal flanks, drumlinized till surface, glacial lineations, medial and retreat moraines, crevasse squeeze ridge networks, eskers, as well as iceberg‐produced terraces and plough‐marks. Analysis of the landforms and landform assemblages in combination with the sediment core data and aerial imagery studies reveal a complex and dynamic glacial history of Hambergbukta. We present a detailed history of Hambergbreen glacier indicating two previously unknown surges as well as new details on the nature of the subsequent ice‐margin retreat. The results from two gravity cores combined with the shallow acoustic stratigraphy and high‐resolution bathymetry suggest that the c. AD 1900 surge was less extensive than previously thought and the retreat was most likely rapid after the c. AD 1900 and 1957 surges of the Hambergbreen. Mixed benthic foraminifera collected from the outer fjord basin date to 2456 cal. a BP, suggesting older sediments were re‐worked by the c. AD 1900 surge. This highlights the importance of exercising caution when using foraminifers for dating surge events in fjord basins enclosed by prominent end‐moraines. [ABSTRACT FROM AUTHOR]

The Ziegler Reservoir fossil site near Snowmass Village, Colorado, provides a rare opportunity to examine environmental conditions in the Rocky Mountains during marine isotope stage (MIS) 4 (71–57 ka). Although recognized as a global-scale cold event, MIS 4 is typically absent from Rocky Mountain glacial chronologies because the geologic evidence was covered or destroyed during the subsequent, and more extensive, MIS 2 (Pinedale; 29–14 ka) glaciation. Ziegler Reservoir lies beyond the Pinedale glacial extent, which allowed for the preservation of a long-lived sequence of eolian sediments deposited in a lacustrine environment that spans from late MIS 6 (ca. 140 ka) through early MIS 3 (ca. 55 ka). Sediments dating to MIS 4 exhibit a significant increase in clay-sized particles, suggesting that the source areas, most likely nearby glacio-fluvial deposits, were enriched with fine-grained material at that time. We hypothesize that the elevated clay content was the result of rock flour production by nearby valley glaciers that were active in the Rocky Mountains during MIS 4. The results of our study illustrate how recognizing indirect evidence of glacial activity can result in a more complete record of past climate conditions than what could be achieved by the study of moraines alone. [ABSTRACT FROM AUTHOR]

Previous studies of push moraines have concluded that structural architecture is controlled by a combination of stress exerted by flowing ice and the rheology of the deforming sediment. However, the relationship between deformation processes and the thermal/hydrologic conditions within the sediment remains ambiguous. Using a combination of surface mapping, logging exposures and ground penetrating radar we examine the relationships between surface morphology, material properties and development of deformation structures in deeply frozen sediment that has been deformed by Joyce Glacier, a cold‐based glacier in the McMurdo Dry Valleys. The structural architecture of the push moraines is characterized by a combination of brittle and ductile deformation structures that have produced a structurally complex pattern of thrust faults, low angle listric thrusts and recumbent folds that extend 400 m beyond the glacier margin. Deformation is ductile where the ice concentration exceeds c. 65% volume and predominantly brittle where the ice concentration is less than c. 65%. The change in rheology reflects transition in behaviour from the material having a predominantly frictional character when the ice is limited to pore spaces to a non‐frictional character in which strength is primarily determined by the cohesive strength of the ice. This work shows that glaciotectonic deformation can occur in deeply frozen permafrost where there is no liquid pore water. We conclude that the presence of liquid porewater is not a necessary condition for the development of glaciotectonic deformation or for the formation of push moraines. © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We describe elongate, wet, subglacial bedforms in the shear margins of the NE Greenland Ice Stream and place some constraints on their formation. Lateral shear margin moraines have been observed across the previously glaciated landscape, but little is known about the ice-flow conditions necessary to form these bedforms. Here we describe in situ sediment bedforms under the NE Greenland Ice Stream shear margins that are observed in active-source seismic and ground-penetrating radar surveys. We find bedforms in the shear margins that are ~500 m wide, ~50 m tall, and elongated nearly parallel to ice-flow, including what we believe to be the first subglacial observation of a shear margin moraine. Acoustic impedance analysis of the bedforms shows that they are composed of unconsolidated, deformable, water-saturated till. We use these geophysical observations to place constraints on the possible formation mechanism of these subglacial features. [ABSTRACT FROM AUTHOR]

Interpreting the relationships among the internal processes of glaciers and their mesoscale structural products has been a long‐standing challenge for glaciologists. Trapridge Glacier is a small polythermal surge‐type valley glacier that has been studied for 40 years. It offers an opportunity to investigate the structural evolution of a glacier through a series of surges and to apply novel modeling approaches to gain physical insight as to how different structures are formed. Following the glacier's most recent slow surge, the structural attributes were documented, with emphasis on their three‐dimensional geometry and sequential development: ice stratification (S0), longitudinal foliation (S1), and associated medial moraine, folding of stratification (F1), transverse foliation (S2), thrusts (S3), and recumbent folds (F3), fractures (surface crevassing and crevasse traces; S4). Efforts to represent these structures using models of glacier flow dynamics remain at an early stage but provide informative tests of model skill and of current understanding of the processes that control structure generation. Using field interpretations as a guide to the relevant processes of formation, structures on Trapridge Glacier are compared with computer‐simulated structures for the same glacier. Modeling achieved the greatest success in simulating moraine patterns, ice stratification, longitudinal foliation, and the downglacier decrease in the density of surface crevasse traces. The least successful effort was to simulate the orientation of crevasse traces. Plain Language Summary: A surge is a short‐lived event during which a glacier flows considerably faster than normal. The switch from slow to fast flow is related to ice instability, resulting from changing hydrology and sediment characteristics at the glacier bed. Building on half a century of field investigations on Trapridge Glacier in the St Elias Mountains (Yukon), we use archived and contemporary field data to investigate and model numerically the structural evolution of the glacier through its most recent full, but unusually slow, surge cycle that ended in 2005. After documenting the initial layering in the glacier (stratification), both ductile structures (stratification, foliation, folds) and brittle structures (crevasses, thrusts, and other fractures) were measured and their order of formation recorded. Using the data collected, the authors were able to simulate the development of these structures using newly derived models of the dynamics of glacier flow (Part 1). Modeling the structures observed in the field then underpinned the development of generic models for broadly similar glaciers (Part 2). The work offers new insight concerning the structural evolution of glaciers generally, notably how the various structures are formed and modified in response to changing stress and strain conditions. Key Points: The formation and evolution of structures in a polythermal surging glacier have been subjected to combined field and modeling analysisThe model‐calculated deformation gradient reveals how total strain influences the development of longitudinal foliation in glaciersCrack modeling yields an explanation for the observed downglacier decrease in fracture density at the glacier surface [ABSTRACT FROM AUTHOR]

The mesoscale structures of a glacier express the history of flow, temperature, and stress. Thus, in principle, numerical ice dynamics models have sufficient physics to examine the formation and transport of these structures. In this study we use a vertically integrated thermomechanical ice dynamics model to simulate the temporally evolving patterns of surficial moraine, stratification, foliation, and folding of glacier ice, and the density and orientation of traces of former crevasses. The modeled glaciers are simplified versions of Trapridge Glacier in northwest Canada that allow diagnostic modeling of influences on glacier structure and help to clarify the physics and numerics. In the model, surges occur every 50 years in response to a prescribed cyclic change in bed friction. Medial moraine patterns are simulated by tracking the englacial and supraglacial trajectory of debris injected at fixed points in the accumulation region. Stratification is assumed to be associated with isochronal surfaces, and vertical foliation is explained in terms of horizontal flattening of strain ellipsoids. Crevasses form when and where the intensity of tensile stress exceeds a prescribed threshold; crack damage is cumulative so that crevasse traces observed at sampling sites are a superposition of the damage accumulated en route. Folding is parameterized but not resolved. By evaluating the deformation gradient tensor along ice particle trajectories and applying the polar decomposition to this tensor, we isolate the cumulative effects of rotation and stretching by ice flow and calculate strain ellipsoids as well as other practical indicators of deformation. Plain Language Summary: A surge is a short‐lived event during which a glacier flows considerably faster than normal. The switch from slow to fast flow is related to ice instability, resulting from changing hydrology and sediment characteristics at the glacier bed. Building on half‐a‐century of field investigations on Trapridge Glacier in the St. Elias Mountains (Yukon), we use archived and contemporary field data to investigate and model numerically the structural evolution of the glacier through its most recent full, but unusually slow, surge cycle that ended in 2005. After documenting the initial layering in the glacier (stratification), both ductile structures (stratification, foliation, and folds) and brittle structures (crevasses, thrusts, and other fractures) were measured and their order of formation recorded. Using the data collected, the authors were able to simulate the development of these structures using newly derived models of the dynamics of glacier flow (Part 1). Modeling the structures observed in the field then underpinned the development of generic models for broadly similar glaciers (Part 2). The work offers new insight concerning the structural evolution of glaciers generally, notably how the various structures are formed and modified in response to changing stress and strain conditions. Key Points: Ice dynamics models have sufficient physics to explain many of the structural features of surging and nonsurging glaciersModel calculations of the deformation gradient indicate that convergent ice flow favors development of longitudinal foliation structuresThe propensity for folding can be parameterized using scalar invariants of a rank 3 tensor derived from the deformation gradient [ABSTRACT FROM AUTHOR]

A prominent thrust‐moraine system formed in the inner van Mijenfjorden, Svalbard, during a surge event in a tributary fjord, creating a large temporary lake. Based on geomorphological, sedimentological, stratigraphical and chronological data, the lake began to form shortly after 648–551 cal. a BP. At its maximum, the lake covered an estimated area of 77 km2 with a water volume of 1.2 km3. Lake sediment up to 80 cm thick was rapidly deposited on top of terrestrial and marine sediments. At its maximum extent, the short‐lived lake was the largest of any known Holocene lake in Svalbard. Modern river discharge would fill the lake to its highest shoreline at 23 m a.s.l. in only one season. Drainage was stepwise, as evidenced by four shorelines and abandoned drainage channels. This study has taken advantage of a unique suite of data available for such an ice‐dammed lake. The results demonstrate the power of a multidisciplinary approach for recognizing lake events in the geological record, which is essential given the low preservation potential of such sediments. [ABSTRACT FROM AUTHOR]

The facies complex of basal moraines with glaciodynamic structures (common basal moraines) dominates among deposits of the given genetic type. These moraines represent glacial diamictons of diverse structure and lithology. Some of their features are also typical of sediments of other genetic types. Therefore, a comprehensive study of glacial diamictons and their occurrence mode on the glacial bed (unconsolidated or consolidated) within large outcrops is methodically correct. Only such studies can unravel the wide range of specific features typical of common basal moraines. [ABSTRACT FROM AUTHOR]

The advance and retreat of ice lobe margins of the Laurentide Ice Sheet formed moraines that are a prevalent feature throughout southwestern Ontario. In contrast to the well-studied stratified moraine complexes, recessional and end moraines have largely been ignored in the context of hydrogeological studies. Recent urban growth has led to development pressures on these moraines and a need to better understand their hydrogeology. This study presents data sets from the Paris Moraine near Guelph, Ontario, to examine its geomorphology, internal composition, and the corresponding hydraulic properties of these ice-marginal features. The moraine's geomorphic elements were mapped using high-resolution Global Positioning System transects, aerial photograph analysis, and ground truthing. Nine continuous sediment cores were recovered to determine the nature and distribution of subsurface sedimentary units and their relation to the regional stratigraphic framework. Cores were described in detail using standard sedimentological techniques, and significant sediment heterogeneity was observed in cross sections. Grain-size analyses of over 150 samples provide site-specific estimates of saturated hydraulic conductivity. In addition, saturated hydraulic conductivity was measured on 104 samples using the falling head permeameter method. This study found that different scales of sediment heterogeneity occur across the moraine and the associated till plain and outwash. In contrast, the hydraulic conductivity varies much less. It is expected that certain sedimentary units at specific depths will impact groundwater flow at the centimetre to hundreds of metres scale, which is significant in environmental site assessments or for understanding contaminant hydrogeological problems. [ABSTRACT FROM AUTHOR]

Abstract: Kettle holes are glacially created ponds that form within landscape depressions and are numerous across young moraine landscapes. Kettle hole water budgets are based primarily on winter precipitation, and therefore, undergo pronounced short‐term changes in water level fluctuations. Little is known about kettle hole sediment biogeochemistry in NE Germany, especially with regards to hydroperiod. Our objective for this study was to link the abiotic influences demarked by the evaporative isotopic signal from kettle hole water and solute chemistry to sediment organic matter turnover imprinted in the sediment δ13C and δ15N isotopic values. From the 20 kettle holes we sampled, 19 of these completely dried out, but on different dates. This dynamic was partially explained by longitudinal and elevational changes over the catchment area illustrating regional controls of kettle hole water balance. At the scale of an individual kettle hole, we estimated evaporation explained up to 38% of water volume loss. The changes in water levels were weakly related to differences in surface sediment elemental N and C concentrations between kettle hole edge and centre positions. These dynamics were primarily driven by redox conditions, Ca2+, and several nutrient concentrations (dissolved organic carbon, total dissolved nitrogen, total dissolved P, and ammonium) in the water column. Although we did not detect differences in the surface sediment δ13C and δ15N values, the δ15N signature in relation to the C:N ratio highlights the advanced decomposition state of surface sediment OM in temporarily water filled kettle holes. [ABSTRACT FROM AUTHOR]

Medial moraines form important pathways for sediment transportation in valley glaciers. Despite the existence of well-defined medial moraines on several glaciers in the New Zealand Southern Alps, medial moraines there have hitherto escaped attention. The evolving morphology and debris content of medial moraines on Franz Josef Glacier and Fox Glacier on the western flank of the Southern Alps is the focus of this study. These temperate maritime glaciers exhibit accumulation zones of multiple basins that feed narrow tongues flowing down steep valleys and terminate ~ 400 m above sea level. The medial moraines at both glaciers become very prominent in the lower ablation zones, where the medial moraines widen, and develop steeper flanks coeval with an increase in relative relief. Medial moraine growth appears somewhat self-limiting in that relief and slope angle increase eventually lead to transport of debris away from the medial moraine by mass-movement-related processes. Despite similarities in overall morphologies, a key contrast in medial moraine formation exists between the two glaciers. At Fox Glacier, the medial moraine consists of angular rockfall-derived debris, folded to varying degrees along flow-parallel axes throughout the tongue. The debris originates above the ELA, coalesces at flow-unit boundaries, and takes a medium/high level transport pathway before subsequently emerging at point-sources aligned with gently dipping fold hinges near the snout. In contrast at Franz Josef Glacier, the medial moraine emerges farther down-glacier immediately below a prominent rock knob. Clasts show a mix of angular to rounded shapes representing high level transport and subglacially transported materials, the latter facies possibly also elevated by supraglacial routing of subglacial meltwater. Our observations confirm that a variety of different debris sources, transport pathways, and structural glaciological processes can interact to form medial moraines within New Zealand's Southern Alps. [ABSTRACT FROM AUTHOR]

We present ∼100 cosmogenic surface exposure ages, including 75 new analyses, for a blue-ice moraine complex at Mt. Achernar, head of Law Glacier, in the central Transantarctic Mountains. The 10Be–3He–26Al ages along with previously-published boron concentrations chronicle past behavior of the East Antarctic Ice Sheet (EAIS) along the edge of the polar plateau since the sediments started to accumulate, around 0.5–1 Ma. Samples analyzed for 10Be from the Law Glacier surface record <100 years of exposure, indicating they likely have negligible inheritance when first exposed. The Law Glacier surface experienced relatively minor fluctuations in surface elevation throughout MIS 6 and 5, and likely during prior periods, as geomorphic features are intact and exposure ages are coherent on the moraine, ranging from ∼210 to ∼86 ka; respective means for MIS 5 till in two different areas are 106 ± 9.1 ka [n = 4 ages] and 106 ± 5.1 ka [n = 6]. Although we infer the Law Glacier has been relatively close to its current configuration generally since 0.5–1 Ma, disturbances to Achernar blue-ice moraine architecture seem apparent at times especially prior to the last two glacial cycles. The largest observed disturbance occurred when the nearby Lewis Cliffs Ice Tongue expanded either close to, or earlier than, 500-400 ka. A minimum ice thickness increase of 30 m is associated with the ∼20 ka blue-ice ridges, and a lateral moraine indicates the Law Glacier surface was ∼40–50 m higher at ∼9.2 ± 0.5 ka. Our findings support that lateral accretion over time formed the Mt. Achernar blue-ice moraine sequence, and by implication, other analogue Antarctic deposits. We interpret blue-ice moraines as representing, at times, relatively constant outlet glacier conditions and concur with prior studies that they reflect near-equilibrium forms. Blue-ice sediments are an underutilized and dateable paleoglaciologic and paleoclimate archive in Antarctica, including for former ice surface dynamics and possibly as a repository of old ice during periods such as MIS 5 and prior. • Paleoglaciology of the central East Antarctic Ice Sheet is revealed by blue-ice sediment. • We present ∼100 cosmogenic ages for a blue-ice moraine at Mt. Achernar, central Transantarctic Mountains. • The Law Glacier surface experienced relatively minor elevation changes during MIS 6 and 5, and possibly back to ∼0.5 Ma. • A lateral moraine indicates the Law Glacier surface was higher at ∼9.2 ± 0.5 ka. • Blue-ice sediments are an underutilized and dateable paleoglaciologic and paleoclimate archive. [ABSTRACT FROM AUTHOR]

ABSTRACT Optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) dating were applied to cave sediments that were protected from the Marine Isotope Stage 2 (MIS-2) advance of the Laurentide Ice Sheet (LIS) in the Champlain Valley of western Vermont. Evidence indicates that these sediments were derived from a subaerial landscape, requiring that the ice margin was north of the Champlain Valley when they were deposited. A basal sandy gravel was deposited during MIS-4 (∼68 ka), sand near the middle of the composite stratigraphy was deposited during MIS-3 (∼55 ka), and a layer of coarse sand in the stratigraphically highest position was deposited at the onset of MIS-2 (∼35 ka). The youngest age constrains advance of the LIS south of the international border early in MIS-2, and is combined with other available evidence to constrain ice advance rates over the 12 000 years leading up to the Last Glacial Maximum. Rates estimated from limiting ages were relatively slow (25 ma−1) as the ice ascended the adverse slope out of the St. Lawrence Lowland, increased as the margin advanced through the Champlain Valley, perhaps aided by subglacial bed deformation or ice streaming, and were fastest (∼100 ma−1) as the margin approached the terminal moraine position. [ABSTRACT FROM AUTHOR]

Poor bleaching is a significant problem for Optically Stimulated Luminescence (OSL) dating of glacial sediments. Five young glacial samples (including two modern analogues) from different depositional settings were collected beyond the Yingpu Glacier in the eastern Qinghai-Tibetan Plateau. De was determined using different OSL methods. The luminescence characteristics and dating results showed that the large aliquot quartz Blue Stimulated Luminescence (BSL) is more applicable than polymineral infrared stimulated luminescence (IRSL) method. Small aliquot quartz BSL results showed poor luminescence properties due to low luminescence sensitivity of quartz in this area. The dating results also indicated that glaciofluvial samples deposited close to ice margin (~40 m and ~700 m) and supraglacial debris dominated lateral moraine samples are relatively well-bleached, whereas samples from ground moraine and low terminal moraine were poorly bleached, probably due to containing subglacial and englacial debris. The residual doses of glaciofluvial and lateral moraine crest samples were below a few Gy and age overestimations were below a few hundred years. The ground moraine and low terminal moraine samples had residual doses as high as ~110 Gy, and ages were overestimated by ~15-17 ka. [ABSTRACT FROM AUTHOR]

A 74-meter Late Pleistocene to Holocene sedimentary sequence was recovered from southern Lake Vättern in the autumn of 2012. At ∼54 m below the lake floor, shear strength and high-resolution bulk density measurements suggest the presence of an unconformity in the varved proglacial clays. Incremental load consolidation tests reveal highly overconsolidated sediments below this level. Preconsolidation pressures for the underlying sediments are between 1250 and 2100 kPa, up to ∼1700 kPa more than the current in-situ effective stress. The highly overconsolidated sediments indicate either substantial erosion (the removal of 215–360 m of sediment), or consolidation under a large grounded ice mass sitting up to 230 m above paleo-lake level. Glaciotectonic deformation in underlying sediments supports the interpretation of a grounded ice mass. It is likely that this horizon is either contemporaneous with or older than the Levene moraine, formed between 13.4 and 13.8 ka. In the ∼30 m of overlying proglacial clays, there is no further evidence for grounded ice, indicating that any ice advance to southern Lake Vättern during the Younger Dryas would have been limited to an extremely thin ice tongue. [ABSTRACT FROM PUBLISHER]

Sedimentary variation within and between annual moraine ridges formed at Storbreen and Styggedalsbreen, Jotunheimen, during the 1980s and 1990s is investigated with a focus on processes and mechanisms of moraine-ridge formation. Tops and bottoms of sediment slabs, deposited either as single annual moraines or incorporated into composite moraine ridges formed of several annual increments, were analysed and compared with possible source sediments with a view to sediment fingerprinting. Clast roundness and shape indicated mainly subglacial sediment origins while textural variability was mainly inherited from proglacial sediment sources, and macrofabrics and micromorphological characteristics revealed overprinting by various glaciofluvial, glaciolacustrine and periglacial processes. The evidence suggests one dominant mechanism of moraine-ridge formation involving the annual freeze-on and subsequent melt-out of overridden proglacial sediment slabs. This mechanism provides the basis of a simple model encompassing both singular and composite annual moraine-ridge formation, which appears appropriate for temperate glacier snouts characterized by deep seasonally frozen ground, close to the lower altitudinal limit of the zone of alpine permafrost. [ABSTRACT FROM AUTHOR]

Geometric characteristics of the washboard moraines of the Des Moines Lobe (DML) of the Laurentide ice sheet agree with their proposed origin as crevasse-squeeze ridges, but study of their sediments is required to help further test this hypothesis. A 70-m-long, 3–5 m high section through a moraine ridge in central Iowa revealed till with irregular, isolated lenses of silt, sand, and gravel that dip to varying extents upglacier. The texture and density of the till are like those of the basal till of the DML studied elsewhere in Iowa, and preconsolidation pressures determined from tests on till and silt of the ridge indicate that it developed subglacially rather than at the glacier margin. Preconsolidation pressures additionally demonstrate that pore-water pressures in the bed supported most of the glacier's weight, which would have contributed to till mobility. Fabrics based on the anisotropy of magnetic susceptibility of 3125 intact till specimens collected at 125 locations in the section indicate two end-member states of strain that varied with location in the ridge and caused sediment mounding: simple shear that was directed downglacier along shear planes inclined upglacier, together with pure shear where an overlying crevasse allowed the sediment bed to extend upward and laterally. Meltwater that likely flowed along the crevasse deposited sorted sediments that were incorporated in till, deformed, and rotated. This positive test of the crevasse-squeeze hypothesis indicates that the DML was in longitudinal extension near its margin, reinforcing previous arguments that the lobe surged. The predominance of fabrics caused by simple shear demonstrates that crevasse filling was underway before the surge had fully halted. This study should prompt caution in using similar transverse ridges, such as those geophysically imaged in some submarine glacier forefields, as indicators of retreat rates. [ABSTRACT FROM AUTHOR]

Late Glacial organic succession is recorded at the Żabieniec and Koźmin Las sites, in the Łódź region. A multiproxy approach provides a palaeogeographical assessment and yields a new insight into the old morainic area of the Polish Lowland. Additionally, the key profile Witów contributes in the reconstruction. It is demonstrated that the Late Glacial organic sediments of the Łódź region contain signs of environmental changes, starting from the first warming just after the Weichselian ice-sheet retreat from the Polish territory. Records at Żabieniec, apart from registering biotic and abiotic conditions which influenced functioning of a peatbog, provides information on the permafrost behaviour throughout the Late Glacial. At Koźmin Las, a unique discovery of the in situ riparian forest accompanied by organic sediments led to a high-resolution study of a series of events taking place on the floodplain during the Younger Dryas. [ABSTRACT FROM AUTHOR]

Large numbers of small valley glaciers on Svalbard were thicker and more extensive during the Little Ice Age (LIA), demonstrated by prominent ice-cored moraines up to several kilometres beyond present-day margins. The majority of these glaciers have since experienced a long period of strongly negative mass balance during the 20th century and are now largely frozen to their beds, indicating they are likely to have undergone a thermal transition from a polythermal to a cold-based regime. We present evidence for such a switch by reconstructing the former flow dynamics and thermal regime of Tellbreen, a small cold-based valley glacier in central Spitsbergen, based on its basal sequence and glaciological structures. Within the basal sequence, the underlying matrix-supported diamict is interpreted as saturated subglacial traction till which has frozen at the bed, indicating that the thermal switch has resulted in a cessation of subglacial sediment deformation due to freezing of the former deforming layer. This is overlain by debris-poor dispersed facies ice, interpreted to have formed through strain-induced metamorphism of englacial ice. The sequential development of structures includes arcuate fracture traces, interpreted as shear planes formed in a compressive/transpressive stress regime; and fracture traces, interpreted as healed extensional crevasses. The formation of these sediment/ice facies and structures is indicative of dynamic, warm-based flow, most likely during the LIA when the glacier was significantly thicker. [ABSTRACT FROM AUTHOR]

Morphostratigraphic relationships between landforms and sediments, comparative boulder weathering status, and paired 10Be and 26Al exposure ages indicate the occurrence of at least three separate glaciations that are interpreted as dating from MIS 2, 6 and possibly 8. The Rhona Glacier remained at or close to its greatest LGM extent until ~17.6 ka due to a very favourable micro-climate that resulted from local topography. That these factors were sufficient to over-power relatively subtle zonal temperature shifts that caused significant changes in more exposed Tasmanian glaciers implies a need for caution in correlating between glacier systems in markedly different topographic settings when environmental conditions are only marginally supportive of glaciation. No evidence was detected for any greater ice extent during MIS 3 or MIS 4 than during MIS 2, but much more extensive glaciations occurred during earlier glacial climatic cycles. Reduced local precipitation in parallel with increasing aridity of the Australian continent may account for the progressively diminishing maximum extent of glaciers during the latter part of the Pleistocene, and it would have emphasized the importance of local topography and microclimate for the glaciers of southwest Tasmania. [ABSTRACT FROM AUTHOR]

A gigantic ∼12 km3 landslide detached from the west wall of Lake Tahoe (California- Nevada, USA), and slid 15 km east across the lake. The splash, or tsunami, from this landslide eroded Tioga-age moraines dated as 21 ka. Lake-bottom short piston cores recovered sediment as old as 12 ka that did not reach landslide deposits, thereby constraining the landslide age as 21-12 ka. Movement of the landslide splashed copious water onto the countryside and lowered the lake level ∼10 m. The sheets of water that washed back into the lake dumped their sediment load at the lowered shoreline, producing deltas that merged into delta terraces. During rapid growth, these unstable delta terraces collapsed, disaggregated, and fed turbidity currents that generated 15 subaqueous sediment wave channel systems that ring the lake and descend to the lake floor at 500 m depth. Sheets of water commonly more than 2 km wide at the shoreline fed these systems. Channels of the systems contain sediment waves (giant ripple marks) with maximum wavelengths of 400 m. The lower depositional aprons of the system are surfaced by sediment waves with maximum wavelengths of 300 m. A remarkably similar, though smaller, contemporary sediment wave channel system operates at the mouth of the Squamish River in British Columbia. The system is generated by turbidity currents that are fed by repeated growth and collapse of the active river delta. The Tahoe splash-induced backwash was briefly equivalent to more than 15 Squamish Rivers in full flood and would have decimated life in low-lying areas of the Tahoe region. [ABSTRACT FROM AUTHOR]

Glacier thermal regime is shown to have a significant influence on the formation of ice-marginal moraines. Annual moraines at the margin of Midtdalsbreen are asymmetrical and contain sorted fine sediment and diamicton layers dipping gently up-glacier. The sorted fine sediments include sands and gravels that were initially deposited fluvially directly in front of the glacier. Clast-form data indicate that the diamictons have a mixed subglacial and fluvial origin. Winter cold is able to penetrate through the thin (<10 m) ice margin and freeze these sediments to the glacier sole. During winter, sediment becomes elevated along the wedge-shaped advancing glacier snout before melting out and being deposited as asymmetrical ridges. These annual moraines have a limited preservation potential of ∼40 years, and this is reflected in the evolution of landforms across the glacier foreland. Despite changing climatic conditions since the Little Ice Age and particularly within the last 10 years when frontal retreat has significantly speeded up, glacier dynamics have remained relatively constant with moraines deposited via basal freeze-on, which requires stable glacier geometry. While the annual moraines on the eastern side of Midtdalsbreen indicate a slow steady retreat, the western foreland contains contrasting ice-stagnation topography, highlighting the importance of local forcing factors such as shielding, aspect and debris cover in addition to changing climate. This study indicates that, even in temperate glacial environments, restricted or localised areas of cold-based ice can have a significant impact on the geomorphic imprint of the glacier system and may actually be more widespread within both modern and ancient glacial environments than previously thought. [ABSTRACT FROM AUTHOR]

The Altai Mountains occupy the northwestern part of the Central Asian collision belt. The late-Holocene behavior of glaciers in the Altai Mountains was reconstructed for the Khaidun river valley in the western part of the Russian Altai. We report here 17 new radiocarbon datings from wood remains buried by moraines, from peat layers and lacustrine sediments. The glaciers’ advance took place in 2500–2200 bc, 1100 bc, 500 bc, ad 400, ad 1200–1300 and ad 1500–1850. It is the first time that material which separates the so-called Historical stage of cooling into three stages has been collected in the Altai Mountains. The comparison of time of moraine formation in the Altai with glacier activity in the Alps is evidence of the simultaneity of these processes. [ABSTRACT FROM AUTHOR]

Abstract: The last glacial period left a mantle of freshly reworked sediments covering the European landscape. Glacial, periglacial, fluvio-glacial, and aeolian dynamics enhanced transportation and mixing of materials, generating new superficial deposits in which Holocene soils developed. These assorted surface sediments often differed from the underlying bedrock in their lithological composition and texture, and were delimited by lithological discontinuities. In the Swiss Jura Mountains, the Mesozoic limestone bedrocks are covered by various superficial deposits (moraines, cover-beds, loess deposits, cryoclasts, etc.), which reduce or even suppress the influence of limestone on present-day soil development. In this context, soils and their underlying bedrock no longer present a genetic continuity. The nature and relationships between these deposits is studied within a toposequence of soils, in terms of their mineralogical and geochemical compositions. Three main superficial deposits (limestone bedrock clasts, loess, and non-carbonate moraine), are used as reference materials in order to characterize the complex mixing of sediments through the toposequence. Soils with limestone clasts undergo decarbonation and decalcification processes. Iron-rich Alpine loess deposits, composed of fine silicate particles, enhance brunification process in soils. A non-carbonate Alpine moraine displays the most acidic conditions within the toposequence due to enhanced leaching (clay and ions) processes. Consequently, the reworked surface sediments (including limestone cryoclasts, moraines, and cover-beds) have a prevailing influence on pedogenesis compared to the hard underlying bedrock. [Copyright &y& Elsevier]

Abstract: A potential complication in using glacier extent to estimate paleoclimatic conditions is the influence of glacier bed evolution on changes in ice extent over time. Here, we examine this issue through model-based reconstructions of the Last Glacial Maximum (LGM) Pukaki glacier, Southern Alps, New Zealand, whose LGM extents are exceptionally well defined by lateral and terminal moraines. Using the well-dated moraine limits as an empirical constraint on maximum ice extents, we employ a one-dimensional glacier flowline model driven by a mass balance model in order to evaluate the influence of climate and glacier bed profile on the extent of the LGM Pukaki glacier. The LGM glacier bed is buried by Lateglacial and post-glacial sediment, so we calculate bed profiles using a modified version of the one-dimensional model and available geologic constraints. A best fit to the moraine record occurs with a LGM temperature of 7–8 °C cooler than present, with precipitation ranging from 80% to 100% of present levels. Modeling of the bed profile evolution indicates that bed changes alone could account for kilometer-scale changes in glacier width and length. [Copyright &y& Elsevier]

This paper presents the first detailed sedimentological study of annual moraines formed by an alpine valley glacier. The moraines have been forming since at least AD 1980 by a subsidiary lobe of Gornergletscher, Switzerland that advances up a reverse bedrock slope. They reach heights of 0.5-1.5 m, widths of up to 6 m and lengths of up to several hundreds of metres. Sediments in these moraines are composed of proglacial outwash and debris flow units; subglacial traction till is absent entirely. Based on four representative sections, three genetic process combinations have been identified: (i) inefficient bulldozing of a gently sloping ice margin transfers proglacial sediments onto the ice, causing differential ablation and dead-ice incorporation upon retreat; (ii) terrestrial ice-contact fans are formed by the dumping of englacial and supraglacial material from point sources such as englacial conduit fills; debris flows and associated fluvial sediments are stacked against a temporarily stationary margin at the start, and deformed during glacier advance in the remainder, of the accumulation season; (iii) a steep ice margin without supraglacial input leads to efficient bulldozing and deformation of pre-existing foreland sediments by wholesale folding. Ice-surface slope appears to be a key control on the type of process responsible for moraine formation in any given place and year. The second and third modes result in stable and higher moraines that have a higher preservation potential than those containing dead ice. Analysis of the spacing and climatic records at Gornergletscher reveals that winter temperature controls marginal retreat and hence moraine formation. However, any climatic signal is complicated by other factors, most notably the presence of a reverse bedrock slope, so that the extraction of a clear climatic signal is not straightforward. This study highlights the complexity of annual moraine formation in high-mountain environments and suggests avenues for further research. [ABSTRACT FROM AUTHOR]

Abstract: We carried out an extensive waterborne GPR survey consisting of 50 profiles with a total length of nearly 37km on the morainic lake of Candia northerly Turin (Italy). Our aim was to test the capability of GPR to estimate the bathymetry, the water volume and the sediment type. We enhanced and controlled the GPR data processing and interpretation with bathymetry acquired with an acoustic echo sounder and measured conductivity and temperature profile of the water column with a multiparametric probe. We also analyzed the diffraction hyperbola that originated within the sediments in order to estimate the velocity and relative permittivity. With the permittivity and dielectric mixing rules, we estimated the porosity of the sediments above the diffracting objects and drew a map of the bottom lake porosity. [Copyright &y& Elsevier]

Abstract: Zircon LA-ICP-MS U–Pb geochronology and geochemistry on representative bedrocks and moraine sediments in the Windmill Islands in Wilkes Land, East Antarctica were performed to characterize the age and origin of main rocks as well as the lithology and age of ice-covered basement in this sector of East Antarctica. Zircon U–Pb dating on two garnet-bearing granite gneisses and one foliated garnet-bearing granite from Bailey Peninsula yield weighted mean 207Pb/206Pb ages of 1247±13Ma, 1258±12Ma and 1242±13Ma, respectively, which are interpreted as emplacement ages of these rocks. Igneous inherited zircons in these rocks yield a weighted mean 207Pb/206Pb age of 1372±13Ma, indicating existence of a ca. 1.37Ga igneous activity in the Windmill Islands. Both garnet-bearing granite gneisses and foliated garnet-bearing granites from Bailey Peninsula are characterized by similar geochemical and isotopic compositions and were likely produced by partial melting of predominantly Paleoproterozoic ancient crustal materials at 1.24–1.25Ga. Zircon U–Pb analyses on two charnockite samples from Robinson Ridge yield weighted mean 207Pb/206Pb ages of 1196±8Ma and 1205±13Ma, respectively, indicating emplacement of the Ardery Charnockite at ca. 1.20Ga. The charnockites were likely produced by partial melting of the ancient mafic lower crust heated by underplated basaltic magma during the D2 cycle at late stage of the granulite facies metamorphism, and some lithospheric mantle materials could be involved during formation of these rocks. U–Pb analyses of detrital zircons from sand-sized moraine sediments yield concordant 207Pb/206Pb ages mainly ranging from ca. 1368Ma to ca. 1107Ma with main magmatic zircon populations at ca. 1107Ma, 1150–1160Ma, ca. 1196Ma, 1231–1255Ma, ca. 1317Ma and ca. 1368Ma, respectively. Some old zircon populations at ca. 1411Ma to ca. 2360Ma, which are considered to be derived from recycling of the Proterozoic metapsammitic gneiss rocks, have been identified. Their zircon Hf isotopic model ages () are mainly around 1.6–2.4Ga. The absence of Archean zircons in moraines suggests that the crust of Law Dome and inland areas of Wilkes Land are dominated by Palaeo-Mesoproterozoic rocks, which is consistent with the vast majority of the Nd–Hf isotopic data presented. Abundant Mesoproterzoic zircons from ca. 1107Ma to ca. 1533Ma in moraines indicate the crustal rocks in the Windmill Island and its inland areas are mainly formed in the Mesoproterozoic. The ages and Hf isotopic compositions of these moraine zircons are comparable with those of the bedrocks in the Windmill Islands, indicating that subglacial rock compositions of Law Dome and the inland areas of Wilkes Land are similar to the rock composition of the Windmill Islands area. Law Dome and the inland areas of Wilkes Land are probablly a similar Mesproterozoic high-grade metamorphic terrane as the Windmill Islands in East Antarctica. Our results also confirmed that there is no evidence for Pan-African tectonothermal events and the Windmill Islands and its inland areas are not affected by Pan-African tectonism and magmatism. [Copyright &y& Elsevier]

Gualas Glacier is an outlet glacier of the Northern Patagonian Icefield, one of the largest temperate ice bodies on Earth. Golfo Elefantes, the depositional basin of Gualas Glacier, has a sedimentary record that spans, with some hiatuses, at least the last ~11.3±3.0 ka. During this period the gulf remained free of ice, as suggested by the absence of proximal glacimarine sediment and till in the sedimentary section. This implies that the arcuate terminal moraines that occur along the edges of Golfo Elefantes were formed during the waning stages of the local glacial maxima (Late Pleistocene) or the early Holocene. Between ~11.3±3.0 ka and ~4.2±0.3–1.4 ka, the basin received low sediment input consisting of fine-grained sediments in the form of low concentration density currents that filled bathymetric lows. Sediment discharge increased several times in the late Holocene (~<1.4 ka) and started with the accumulation of ~ 0.5 km3 of sandy sediments in a relatively short time span (~670 yr). This high discharge of sandy sediments is interpreted as being the result of glacial reworking of sediments stored in Gualas Glacier proglacial lake and thus implies that the glacier advanced at ~1.4–0.8 ka. The overall increase in sediment discharge in the late Holocene indicates a sharp increase in centennial timescale precipitation, which in turn suggests an increase in the intensity of the westerly winds in the area. Two recent periods of interannual sedimentation variability were identified at ~ad 1160–1460 and ~ad 1680–1890 and correlate with documented regional glacier advances. [ABSTRACT FROM PUBLISHER]

Lacustrine, alluvial terraces and sediments record at least one Holocene glacially dammed lake in Songzong Basin immediately upstream of the Purlung TsangpoRiver, a main tributary of the downstream of Yarlung Tsangpo River, at the northeastern syntaxis of the Himalaya. The lacustrine deposit is more than 88 meters thick at the SongzongLandslide. There is an 18.33 meters thick layer of lacustrine silt within the lacustrine terrace. The Optical Simulated Luminescence (OSL) ages at the bottom and top of the lacustrine silt layerare 22.5±3.3ka B.P., and 16.1±1.7ka B.P., respectively, which indicates that the lacustrine deposits were formed during the Last Glacial Maximum ranging from 25kaB.P. to 15kaB.P.The ancient shorelines and the lake erosion zone confirm the preexistence of Songzong Lake. There are also terraces formed by moraines in the Songzong Basin. The high and large moraineterrace seen near the mouth of the Dongqu Valley is very prominent. The special characteristics of thelacustrine sediment and the ancient lake line in the Songzong Basin indicate that the lacustrinesediments are related to the blocking of the Purlung Tsangpo River by a glacier from DongquValley during Last Glacial Maximum. [ABSTRACT FROM AUTHOR]

Tunnicliffe, J., Church, M. & Enkin, R. J. 2012 (January): Postglacial sediment yield to Chilliwack Lake, British Columbia, Canada. Boreas, Vol. 41, pp. 84-101. 10.1111/j.1502-3885.2011.00219.x. ISSN 0300-9483. Seismic records and evidence from sediment cores at Chilliwack Lake provide the basis for a long-term (postglacial) sediment budget for a 324-km2 Cordilleran catchment. Chilliwack Lake (11.8 km2 surface area), situated in the North Cascade Mountains, near Chilliwack, British Columbia, was formed behind a valley-wide recessional moraine in the final phase of post-Fraser alpine glaciation. Seismic surveys highlight the postglacial lacustrine record, which is underlain by a thick layer of sediments related to deglacial sedimentation. Sediment cores provide details of grain-size fining from the delta to the distal lake basin. The cores also show a record of intermittent fire and debris flows. Magnetic measurements of lake sediments provide information on grain size, as well as a dating framework. The total postglacial lake-floor deposit volume is estimated to be 397 ± 27 × 106 m3. Including estimates of fan and delta deposition, the specific postglacial yield to the lake is calculated to be ∼86 ± 13 Mg km2 a−1. The sediment volume in the uppermost (Holocene) lacustrine layer is 128 ± 9 × 106 m3, representing ∼41 ± 4 Mg km2 a−1 in the Holocene. Compared with other Cordilleran lakes of similar size, particularly those with glacial cover in the watershed, Chilliwack Lake has experienced relatively modest rates of sediment accumulation. This study provides an important contribution to a growing database of long-term (postglacial) sediment yield data for major Cordilleran lakes, essential for advancing our understanding of the pace of landscape evolution in formerly glaciated mountainous regions. [ABSTRACT FROM AUTHOR]

Bathymetry and bottom sediment types of inland water basins provide meaningful information to estimate water reserves and possible connections between surface and groundwater. Water-borne geophysical surveys can be used to obtain several independent physical parameters to study the sediments. We explored the possibilities of retrieving information on both shallow and deep geological structures beneath a morainic lake by means of waterborne nonseismic methods. In this respect, we discuss simultaneous magnetic, electrical, and ground-penetrating radar (GPR) waterborne surveys on the Candia morainic lake in northerly Turin (Italy). We used waterborne GPR to obtain information on the bottom sediment and the bathymetry needed to constrain the magnetic and electrical inversions. We obtained a map of the total magnetic Held (TMF) over the lake from which we computed a 2D constrained compact magnetic inversion for selected profiles, along with a laterally constrained inversion for one electrical profile. The magnetic survey detected some deep anomalous bodies within the slibbottom moraine. The electrical profiles gave information on the more superficial layer of bottom sediments. We identify where the coarse morainic material outcrops from the bottom finer sediments from a correspondence between high GPR reflectivity, resistivity, and magnetic anomalies. [ABSTRACT FROM AUTHOR]

Abstract: At several times during the Quaternary, a major eastward-flowing outlet glacier of the former Patagonian Ice Sheet occupied the Lago San Martin Valley in Argentina (49°S, 72°W). We present a glacial chronology for the valley based on geomorphological mapping and cosmogenic nuclide ( 10 Be) exposure ages (n =10) of boulders on moraines and lake shorelines. There are five prominent moraine belts in the Lago San Martin Valley, associated with extensive sandar (glaciofluvial outwash plains) and former lake shorelines. Cosmogenic nuclide exposure ages for boulders on these moraines indicate that they formed at 14.3±1.7ka, 22.4±2.3ka, 34.4±3.4ka to 37.6±3.4ka (and possibly 60±3.5ka), and 99±11ka (1σ). These dated glacier advances differ from published chronologies from the Lago San Martin Valley based on 14C age determinations from organic sediments and molluscs in meltwater channels directly in front of moraines or in kettleholes within end moraine ridges. The moraine boulder ages also point to possible pre-LGM glacial advances during the last glacial cycle and a key observation from our data is that the LGM glaciers were probably less extensive in the Lago San Martin Valley than previously thought. [Copyright &y& Elsevier]

Abstract: Progressive glacier thinning, retreat and mass loss in the High-Arctic is increasingly exposing forefield sediments to processes of mobilisation and redistribution. In this paper, we quantify forefield sediment redistribution at Midtre Lovénbreen, Svalbard, using repeat light detection and ranging (lidar) surveys conducted in 2003 and 2005 in combination with field-based observations. Average surface lowering of the forefield over the observation period identified from lidar surveys is −0.05ma−1; and two primary areas of sediment reworking are identified: active fluvial incision of proglacial streams by ~2m and lateral moraine downwasting of similar magnitude. Multivariate analysis of fluvial and climatological field data indicates that observed forefield sediment mobilisation is driven primarily by discharge forcing, but with contributions from thermoerosive processes and stochastic, autogenic sediment supply. During the period of observation, disparity between sediment loss in forefield fluvial systems as calculated from lidar data (3000–4000×103 kg) and monitoring of fluvial sediment load (1600–3500×103 kg) suggests the likely presence of significant quantities of buried ice beneath a thick debris mantle, as evidenced by field observations. Relatively uniform lowering of the moraine crest identified from our repeat lidar surveys indicates thermoerosion of an ice core. However, simple debris layer thickness modelling indicates an increase in variation of debris layer thickness at lower elevations, providing support for the assertion that moraine disintegration is driven by complex combinations of both thermal and mechanical processes. This study demonstrates the viability of using lidar in conjunction with field monitoring to better understand sedimentary deglaciation dynamics and processes, and also highlights the significance of forefield areas in controlling the sediment yield from deglaciating catchments. [Copyright &y& Elsevier]

Abstract: Exposures through the LGM latero-frontal moraine loops at sites along the west coast of South Island, New Zealand reveal a depositional environment that was dominated by the progradation of steep fronted, debris flow-fed fans, manifest in crudely stratified to massive diamictons, arranged in sub-horizontal to steeply dipping clinoforms and containing discontinuous bodies of variably sorted, stratified sediment (LFA 1). The fans were constructed by debris-covered glaciers advancing over outwash plains, as recorded by well stratified and horizontally bedded gravels, sands and diamicts (LFA 0). The ice-contact slopes of the fans are offlapped by retreat phase deposits in the form of glacilacustrine depo-centres (LFA 2), which record the existence of moraine-dammed lakes. Interdigitation of lake rhythmites and subaerial to subaqueous sediment gravity flow deposits documents intense debris-flow activity on unstable moraine/fan surfaces. Glacier readvances in all catchments are documented by glacitectonic disturbance and localized hydrofracturing of LFA 2, followed by the emplacement of schist-dominated debris flow-fed fans (LFA 3) inside and over the top of the earlier latero-frontal moraine/fan loops. Contorted and disturbed bedding in LFA 3 reflects its partial deposition in supraglacial positions. Clast lithologies in LFAs 1 and 3 reveal that two distinct transport pathways operated during moraine construction, with an early period of latero-frontal fan construction involving mixed lithologies and a later period of ice-contact/supraglacial fan construction dominated by schist lithologies from the mountains. These two periods of deposition were separated by a period of moraine abandonment and paraglacial reworking of ice-contact slopes to produce LFA 2. The occurrence of LFA 3 at all sites indicates that the glacier readvance phase responsible for its deposition was not localized or glacier-specific, and involved the transfer of large volumes of schist, possibly due to rock slope failures, onto glacier surfaces. The absence of any sediment that could be unequivocally classified as subglacial till reflects the dominance of debris flow and glacifluvial processes in latero-frontal moraine construction in this hyper-humid west coast setting. [Copyright &y& Elsevier]

Abstract: The subdivision and ordering of Quaternary sediments and landforms is very often based on geomorphology. Quaternary landforms such as moraines, river terraces, palaeoshorelines, and indeed any other landform, can be arranged and ordered in time based on their relative position in the landscape. Morphostratigraphy is the subdivision of sedimentary units primarily on the basis of surface form. Whilst surface form is often used as a criterion for separating sedimentary units, morphostratigraphy also usually incorporates lithological criteria to aid stratigraphical subdivision, and morpho- and lithostratigraphy are often interlinked in Quaternary science. However, another approach–allostratigraphy–has increasingly been applied to subdivide and order Quaternary sediment landforms. Allostratigraphy uses discontinuities to subdivide sedimentary successions. Allostratigraphy enables lateral variations in lithology to be included within the same stratigraphical unit. Furthermore, it enables lithologically similar sediments stacked on top of each other to be divided into separate units based on discontinuities. This paper examines the applications of morpho-, litho- and allostratigraphy to subdivide sediment-landform assemblages and critically reviews their role in Quaternary stratigraphy. [Copyright &y& Elsevier]

Abstract: Moraine and glacier dams bordering the Homathko Icefield in the southern British Columbia Coast Mountains failed in the 1980s and 1990s, causing catastrophic downstream floods. The largest of the floods occurred in August 1997 and was caused by overtopping and rapid breaching of the moraine dam that impounds Queen Bess Lake. The floodwaters from Queen Bess Lake eroded Holocene-age sedimentary deposits along the west fork of Nostetuko River and caused a steep rise in the hydrograph of Homathko River at the head of Bute Inlet, ∼115km downstream. A field investigation of the eroded valley fill in 2008, revealed multiple paraglacial valley-fill units, many of which are capped by in situ stumps and woody detritus. Dendrogeomorphological field techniques were employed to develop a chronology for the buried forests. A regional tree-ring chronology spanning the interval CE 1572–2007 was constructed from living subalpine fir (Abies lasiocarpa) trees at seven sites in the southern Coast Mountains. In cases where subfossil stumps and boles predated the regional chronology, relative death dates constrained by radiocarbon ages were assigned to floating chronologies. By combining these dendrogeomorphological dating methods, we identified six floodplain aggradation episodes within the past 1200years. Comparison to local and regional glacial histories suggests that these events reflect climate-induced Little Ice Age changes in local glacier cover. [Copyright &y& Elsevier]

Merten, Eric C., Nathaniel A. Hemstad, Randall K. Kolka, Raymond M. Newman, Elon S. Verry, and Bruce Vondracek, 2010. Recovery of Sediment Characteristics in Moraine, Headwater Streams of Northern Minnesota After Forest Harvest. Journal of the American Water Resources Association (JAWRA) 46(4): 733-743. DOI: 10.1111/j.1752-1688.2010.00445.x We investigated the recovery of sediment characteristics in four moraine, headwater streams in north-central Minnesota after forest harvest. We examined changes in fine sediment levels from 1997 (preharvest) to 2007 (10 years postharvest) at study plots with upland clear felling and riparian thinning, using canopy cover, proportion of unstable banks, surficial fine substrates, residual pool depth, and streambed depth of refusal as response variables. Basin-scale year effects were significant ( p < 0.001) for all responses when evaluated by repeated-measures ANOVAs. Throughout the study area, unstable banks increased for several years postharvest, coinciding with an increase in windthrow and fine sediment. Increased unstable banks may have been caused by forest harvest equipment, increased windthrow and exposure of rootwads, or increased discharge and bank scour. Fine sediment in the channels did not recover by summer 2007, even though canopy cover and unstable banks had returned to 1997 levels. After several storm events in fall 2007, 10 years after the initial sediment input, fine sediment was flushed from the channels and returned to 1997 levels. Although our study design did not discern the source of the initial sediment inputs (e.g., forest harvest, road crossings, other natural causes), we have shown that moraine, headwater streams can require an extended period (up to 10 years) and enabling event (e.g., high storm flows) to recover from large inputs of fine sediment. [ABSTRACT FROM AUTHOR]

Abstract: Optically stimulated luminescence (OSL) dating methods have been widely applied in Quaternary glaciology. However, glacigenic deposits are considered in general as problematic for OSL dating, mainly because they are transported shorter distances prior to burial and are usually partially bleached. Thus, most researchers choose glaciofluvial and glaciolacustrine sediments (with relatively longer transportation times) for OSL dating when constraining the age of glaciation. In this study, four samples were collected from a lateral moraine series at Zhuqing Village, northern margin of Queer Shan Mountain, eastern Tibetan Plateau, in order to investigate the applicability of OSL dating for morainic deposits. Quartz grains (38–63μm) were extracted and measured using single aliquot regenerative-dose (SAR) protocol. Internal checks and dose recovery test show that the SAR protocol is appropriate for equivalent dose (De) determination. The effect of thermal transfer is small for all samples and the recycling ratio for each individual sample is close to unity. The symmetry in the De distributions indicates that quartz grains were well-bleached prior to burial. OSL ages show good agreement with geomorphological and field investigations, and are also concordant with an independent ESR age. It is concluded that: (a) the morainic deposits in Zhuqing were well-bleached and suitable for OSL dating; (b) SAR protocol can be applied to morainic deposits for samples under study. [Copyright &y& Elsevier]

Abstract: Several high resolution seismic surveys were conducted in Alpine and pre-Alpine Lombardia (Northern Italy) valleys in order to reconstruct the geometries of the sediments filling the valleys, their seismo-stratigraphy and the rock basement depth. The acquisitions were made mainly in the framework of the CARG (Geological CARtography) project for the new geological map of Italy and under different research programs between the National Research Council and Regione Lombardia. The research firstly shows the capability of seismic methods in support of Quaternary research, and secondly demonstrates the response of different geomorphological features in particular: glacial valley, terminal moraine, deeply eroded valley and alluvial plain. Different tests were carried out in the seismic surveys in order to optimize the acquisition techniques for shallow prospecting (100–1000m depth). The data were processed by applying a seismic refraction inversion technique, in addition to standard reflection processing. The integration of the two data sets improves the seismic migration of the reflection sections and the seismic interpretation, producing well-constrained seismo-stratigraphic sections coupled with an accurate seismic velocity section. The quality of the reflected events is generally higher in the glacial domain than in the fluvioglacial eroded valley, probably due to a stronger impedance contrast between soft sediments and hard rock. The terminal moraine sections show an intermediate quality of reflection record. [Copyright &y& Elsevier]

Summary: Recent studies suggest that talus slopes and moraines likely play an important role in groundwater flow and storage in alpine watersheds, though the subsurface processes of these unconsolidated sediment features are not fully understood. To gain insight into these groundwater systems, we investigated the spatial variability in groundwater properties and hydrological trends of a large spring and several nearby (⩽200m) springs, discharging from a single moraine–talus feature in an alpine watershed in the Canadian Rockies. A key question was whether groundwater flow in these features is reasonably homogeneous. Hydrograph analyses revealed at least two different groundwater responses to precipitation and melt inputs: a rapid and likely localized response and a slower response indicating a subsurface connection to a nearby lake. There was also a large spread in groundwater composition across the large spring and between springs, including a consistent linear trend in major ion chemistry over a 20-m section of the large spring. The spatial and temporal trends in groundwater chemistry data suggests there are three groundwater components associated with this sediment feature, and that their relative contributions vary temporally, though the component associated with the lake appears dominant. The study findings suggest that unconsolidated sediment features can possess multiple, and possibly disconnected, groundwater flow paths exhibiting unique hydrological and geochemical characteristics, and cannot necessarily be treated as a single, homogeneous groundwater component when modeling the hydrology of alpine watersheds. [Copyright &y& Elsevier]

The study of glacial landforms and deposits is important, as it is difficult to observe processes under modern glaciers and ice-sheets. Thus landscapes and sediments that are the product of present glaciation can give insight into processes that occurred during Pleistocene times. This study investigates the genesis of little ice age glacial landforms present in Portage Glacier, South-Central Alaska. The present day moraine morphology and sedimentology in Portage Glacier valley reveals the presence of two types of till and moraines. The clast-rich sandy diamicton present on the 1852 moraine is interpreted to be a basal till indicating this feature is a push moraine representing an advance or a standstill position of Portage Glacier in 1852. The moderately sorted gray sandy boulder gravel present on the 1900 and 1922 moraines is interpreted to be an ice-marginal deposit (ablation till) with a mixture of supraglacial and glaciofluvial sediments deposited by slumping and stream sorting processes. All of these features are interpreted to be ablation moraines representing glacier retreat and moraine building in 1900 and 1922. [ABSTRACT FROM AUTHOR]

Abstract: Optically stimulated luminescence (OSL) dating was applied to glacial sediments and adjacent loess from moraines in the Teskey Ala-Too and At-Bashy Ranges in the inner Tien Shan, Kyrgyz Republic (Kyrgyzstan). Two large glacier expansions during the Last Glacial were observed in the two study areas; Teskey (=Terskey) Stages I and II moraines were dated to marine isotope stage (MIS) 4–early-MIS 3 and MIS 2, and At-Bashy Stage II in the At-Bashy Range dated to late-MIS 3–MIS 2. The timing of the two expansions during the Last Glacial coincided with global cold periods and with advances of the major Northern Hemisphere ice sheets. However, the fact that the greater expansion occurred in MIS 4–early-MIS 3 in the Teskey Ala-Too Range, suggests that climate during MIS 4–early-MIS 3 was more humid than during MIS 2. It is possible that the strengthened Siberian High during MIS 2 restricted the impact of the westerlies and this reduced precipitation in the study area. [Copyright &y& Elsevier]