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We report on the key physical features of an active rock glacier that influence the distribution of plants and arthropods. We also perform a comparison with neighboring scree slope and alpine grassland to test whether the environmental features of the rock glacier drive the presence of specific species assemblages. Compared with scree slope and grassland, the studied rock glacier provides particular physical features that determine the presence of unique species. Plant distribution is mainly driven by grain size. Arthropod distribution is linked to grain size, with cold-adapted species found on areas with coarse-grained deep debris, which also shows a distinctive temperature regime with very low values throughout the year. On the basis of these findings, we advance the hypothesis that rock glaciers provide specific ecological conditions creating potential refugia for cold-demanding species during warm climatic periods. [ABSTRACT FROM PUBLISHER]

The spatial distribution and several morphometric characteristics of the Quaternary alluvial fans of the San Juan River, in the province of San Juan, at the Central and Western part of Argentina, have been studied to classify them as paraglacial megafans, as well to ratify its depositional environmental conditions. The high sedimentary load exported by San Juan river from the Central Andes to the foreland depressions is estimated about 3,682,200 hm 3 . The large alluvial fans of Ullum-Zonda and Tulum valleys were deposited into deep tectonic depressions, during the Upper Pleistocene deglaciation stages. The outcome of collecting remotely sensed data, map and DEM data, geophysical data and much fieldwork gave access to morphometric, morphographic and morphogenetic data of these alluvial fans. The main drainage network was mapped on processed images using QGis (vers.2.0.1). Several fan morphometric parameters were measured, such as the size, the shape, the thickness, the surface areas and the sedimentary volume of exported load. The analyzed fans were accumulated in deep tectonic depressions, where the alluvium fill reaches 700 to 1200 m thick. Such fans do not reach the large size that other world megafans have, and this is due to tectonic obstacles, although the sedimentary fill average volume surpasses 514,000 hm 3 . The author proposes to consider Ullum-Zonda and Tulum alluvial fans as paraglacial megafans. According to the stratigraphic relationships of the tropical South American Rivers, the author considers that the San Juan paraglacial megafans would have occurred in the period before 24 ka BP, possibly corresponding to Middle Pleniglacial (ca 65–24ka BP). They record colder and more humid conditions compared with the present arid and dry conditions. [ABSTRACT FROM AUTHOR]

The Indus River, one of Asia's premier rivers, drains the western Tibetan Plateau and the Nanga Parbat syntaxis. These two areas juxtapose some of the lowest and highest topographic relief and commensurate denudation rates in the Himalaya-Tibet orogen, respectively, yet the spatial pattern of denudation rates upstream of the syntaxis remains largely unclear, as does the way in which major rivers drive headward incision into the Tibetan Plateau. We report a new inventory of 10Be-based basinwide denudation rates from 33 tributaries flanking the Indus River along a 320 km reach across the western Tibetan Plateau margin. We find that denudation rates of up to 110 mm k.y.-1 in the Ladakh and Zanskar Ranges systematically decrease eastward to 10 mm k.y. -1 toward the Tibetan Plateau. Independent results from bulk petrographic and heavy mineral analyses support this denudation gradient. Assuming that incision along the Indus exerts the base-level control on tributary denudation rates, our data show a systematic eastward decrease of landscape downwearing, reaching its minimum on the Tibetan Plateau. In contrast, denudation rates increase rapidly 150-200 km downstream of a distinct knickpoint that marks the Tibetan Plateau margin in the Indus River longitudinal profile. We infer that any vigorous headward incision and any accompanying erosional waves into the interior of the plateau mostly concerned reaches well below this plateau margin. Moreover, reported long-term (>106 yr) exhumation rates from low-temperature chronometry of 0.1-0.75 mm yr-1 consistently exceed our 10Be-derived denudation rates. With averaging time scales of 10³-104 yr for our denudation data, we report postglacial rates of downwearing in a tectonically idle landscape. To counterbalance this apparent mismatch, denudation rates must have been higher in the Quaternary during glacial-interglacial intervals. [ABSTRACT FROM AUTHOR]

ABSTRACT Thawed soils in Antarctica represent organic carbon (C) reservoirs with great potential to increase the net losses of CO2 to the atmosphere under climate change scenarios. This study spatially zones CO2 emissions from soil and vegetation along a transect in front of the retreating margin of Ecology Glacier in Admiralty Bay, King George Island, South Shetlands, near the Polish Antarctic station Henryk Arctowski. Two experiments were carried out to determine soil respiration: (1) a transect of 150 measuring points spaced 1 m apart, statistically analysed with split moving windows, identified three regions with different patterns of CO2 emissions; (2) a survey with three grids containing 60 sampling points, with a minimum distance between points of 0.30 m, totalling 2.7 × 1.5 m, in each of the identified locations. The survey showed that CO2 emission rates decreased (from 2.38 to 0.00 µmol m-2s-1) and soil temperature at 5 cm depth increased (from 1.9 to 7°C) near the glacier. The site farthest from the glacier provided an emission 3.5 times higher than the closest site. The spatial variability of CO2 emissions decreased with distance from the glacier. Soil development and vegetation are identified as key drivers of CO2 emissions. Soil formation and vegetation growth increased with longer exposure since deglaciation, leading to enhanced homogeneity of CO2 emissions, independent of permafrost occurrence and stability. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Globally, glacial and paraglacial environments in mountains are vulnerable to the effects of ongoing contemporary climate change (global warming), but monitoring of such systems today provides only a limited spatial and temporal viewpoint of their likely evolution over coming decades to centuries. This is because these environments show complex and nonlinear responses to forcing and are affected by time lags, feedbacks and antecedent factors, including geologic control and geologic history that present monitoring of these systems cannot capture. In order to evaluate how glacial and paraglacial environments in mountains are likely to respond to future climate change, we consider how these environments have responded to climate change in the past (the last glacial-interglacial transition, and the Little Ice Age). From this, we may anticipate the likely responses of glacial and paraglacial environments in mountains to global warming over coming decades. We show that future changes in glacial and paraglacial environments, in particular in glaciated regions in continental interiors, have downstream implications for the biosphere (including biodiversity and ecosystem services, sustainable agriculture and water resources), the human environment (including cultural and heritage landscapes and social/economic activities), and for policy and planning. These will be important issues for the later twenty-first century and beyond. [ABSTRACT FROM AUTHOR]

In this study we used the Schmidt hammer to assess the relative exposure ages of previously dated Little Ice Age moraines deposited by Svellnosbreen glacier in Jotunheimen southern Norway. Schmidt hammer measurements were taken on moraine surfaces which have been deglaciated for 79-259 years since the Little Ice Age, to reconstruct and date previous snout positions. Dating used a typical linear Little Ice Age age-calibration curve and the ages of unknown surfaces were predicted based on Schmidt hammer measurements with the support of lichenometric dates. Calibrated ages exhibited potential dating errors of ±63-103 years, which were estimated using 95% confidence intervals associated with two control points based on moraines of known ages. Schmidt hammer R-value variability was identified and sources of significant errors were attributed to variations in boulder surface texture and the incorporation of weathered boulders into moraines through push mechanisms and paraglacial reworking. [ABSTRACT FROM AUTHOR]

This first overview of large-scale rock slope failure (RSF) in the Pyrenees addresses the eastern third of the range. Around 30 principal RSFs greater than 0.25 km2 and 20 lesser or uncertain cases have been identified from remote imagery and groundtruthing. Compared with other European mountain ranges, RSF incidence is relatively sparse, displays no obvious regional trend or spatial clustering, and occurs across diverse landscape types, if mainly on metamorphic rocks. A transition is observed from paraglacial RSFs in formerly glaciated valleys to what are here termed 'parafluvial' RSFs, within wholly or mainly fluvial valleys but where slope failure is not directly provoked by or linked to river erosion. RSFs are particularly found in three topographic settings: at cirque and trough-head thresholds (transition zones of elevated instability between cirque and main glaciated trough walls); near the upper or outer periphery of the ice field, where glacial adaptation of fluvial valleys is incomplete; and in fluvial valleys beyond glacial limits where incision is locally intense. RSF is absent from the range divide, from within cirques, and from most main valleys. In the montane areas, RSF is strongly associated with vestiges of preglacial summit surfaces, confirming that plateau ridges are less stable than sharpened crests and horns. RSF is contributing significantly to the progressive destruction of this paleic relief. The overall sparsity of RSF indicates insufficient rock mass stresses, including rebound after concentrated bedrock erosion. This may reflect a relatively weak imprint of glacial erosion, including breaching, in a context of relatively low mean rates of neotectonic uplift, possibly signalling overall that eastern Pyrenees landscapes are close to dynamic equilibrium. [ABSTRACT FROM AUTHOR]

Abstract: High mountain geomorphology is mostly characterized by high elevation, steep gradients, rocky terrain, the presence of snow and ice and the related processes occurring in a high energy environment. Large sources of sediment and sediment storages often exist within high mountain systems and are controlled by the processes occurring within this setting. The purpose of this study is to describe sediment paths on a periglacial mountain slope and quantify geomorphic work within one example year in order to analyze and compare sediment budgets in high mountain geosystems. This energy-related approach helps to characterize a periglacial slope on account of the effectiveness of its geomorphological processes and might help to understand the complex dynamic behavior of its constituent subsystems. A periglacial mountain slope is investigated in Eastern Switzerland (Corvatsch). The environment is characterized by a typical coarse debris cascade: rock wall→rock fall→talus slope→permafrost creep→rockglacier. Rockglaciers are considered to be sediment traps of the coarse debris system, reflecting the erosion history of the corresponding catchment. Headwall recession and creep processes of the talus slopes and rockglaciers are quantified by a multi-method-approach combining remote sensing and terrestrial methods. Multitemporal DEMs of the last two decades enabled the quantification of sediment transfer of the slow moving landforms (frozen talus slopes and rockglaciers). Sediment input from the rock wall is quantified by repeated laser scanning over the last 4years. With the introduced cascading approach it is possible to assess dynamics within the coarse debris system. The mountain slope is divided into three subsystems (headwall, talus cone and rockglacier) and their dynamics are analyzed individually but also in relation to the entire mountain slope on a yearly base. A backweathering rate of 2mm can be derived for the headwall and an energy transfer of 29.8GJ from the headwall to the slope, 4GJ from the talus slope to rockglacier where 1.44GJ of geomorphic work are released by the downwards creep of the landform. This study is the first to include an analysis of the geomorphic work generated on the basis of vertically differentiated sediment production and transport processes. [Copyright &y& Elsevier]

Calcareous dust is often closely associated with periglacial features in the Pleistocene deposits of extra-Andean Argentina. Conventionally interpreted as resulting from continental pedogenic weathering and precipitation during interglacial episodes, little has yet been demonstrated about its origin. Strontium, oxygen and carbon isotopic compositions and REE distributions were determined for such calcareous dust from a wide geographic area including sites in Patagonia, the southern Pampa and the Mendoza Pre-Cordillera. The δ 13 C values between − 1.9 and − 7.2‰ (V-PDB) and δ 18 O values between − 2.6 and − 6.0‰ (V-SMOW) confirm a glaciogenic origin and not the generally advocated pedogenic genesis. The narrow 87 Sr/ 86 Sr ratio from 0.706463 ± 0.000008 to 0.707477 ± 0.000006 (2σ) and the constant REE distribution with a specific negative Ce anomaly both require crystallization in a large and homogeneous reservoir with some seawater supply during successive glacial episodes. The homogeneous Sr isotopic and REE data suggest that the Ca, Sr and REEs released from Andean basement rocks during glacial episodes: (1) were transported by rivers to the eastern continental shelf of which up to ~ 1 million of km 2 was probably emerged during the successive glacial episodes, (2) were mixed there in a semi-marine lacustrian meander-rich environment with seawater supply where they dissolved and re-precipitated, before (3) being eroded and dispersed by southeasterly winds over most of Argentina. [ABSTRACT FROM AUTHOR]

Abstract: The 2002 M w 7.9 Denali Fault earthquake, Alaska, provides an unparalleled opportunity to investigate in quantitative detail the regional hillslope mass-wasting response to strong seismic shaking in glacierized terrain. We present the first detailed inventory of ∼1580 coseismic slope failures, out of which some 20% occurred above large valley glaciers, based on mapping from multi-temporal remote sensing data. We find that the Denali earthquake produced at least one order of magnitude fewer landslides in a much narrower corridor along the fault ruptures than empirical predictions for an M ∼8 earthquake would suggest, despite the availability of sufficiently steep and dissected mountainous topography prone to frequent slope failure. In order to explore potential controls on the reduced extent of regional coseismic landsliding we compare our data with inventories that we compiled for two recent earthquakes in periglacial and formerly glaciated terrain, i.e. at Yushu, Tibet (M w 6.9, 2010), and Aysén Fjord, Chile (2007 M w 6.2). Fault movement during these events was, similarly to that of the Denali earthquake, dominated by strike-slip offsets along near-vertical faults. Our comparison returns very similar coseismic landslide patterns that are consistent with the idea that fault type, geometry, and dynamic rupture process rather than widespread glacier cover were among the first-order controls on regional hillslope erosional response in these earthquakes. We conclude that estimating the amount of coseismic hillslope sediment input to the sediment cascade from earthquake magnitude alone remains highly problematic, particularly if glacierized terrain is involved. [Copyright &y& Elsevier]

Numerous periglacial features (polygons, nets, soil stripes, ice-wedge pseudomorphs and sand-wedge casts, involutions) have been recorded in France by examining bibliographical sources and aerial photographs. These data show that a large part of France was affected by permafrost during the Pleistocene and only the southern Aquitaine Basin and Languedoc seem to have been beyond its maximum extent. The first OSL ages obtained from the aeolian infill of wedge structures indicate that at least two phases of thermal contraction cracking occurred in southwestern France between ∼25 and 36 ka. Chronostratigraphical data from loess in northern France indicate that these episodes correspond to the formation of ice-wedge networks associated with tundra gleys. In the latter region, two additional permafrost episodes probably occurred during the Last Glacial, the older one corresponding to the end of Marine Isotope Stage ( MIS) 4 around 60 ka and the more recent one to MIS 2 around 19-16 ka. Although stratigraphical data indicate that these episodes were relatively short (about one millennium), relict permafrost may have existed for longer periods in northern France. [ABSTRACT FROM AUTHOR]

The nature of permafrost and related environmental conditions in the Weichselian Late Pleniglacial and Lateglacial are reconstructed based on the assessment of frost structures that are best documented in the Loess Belt and in plateau areas composed of glacial till. Investigations were conducted in the central-eastern part of the European Sand Belt ( SE Poland and NW Ukraine) on a fluvio-aeolian sedimentary succession and took into account its chronological context given by luminescence dating. Various generations of periglacial structures found in these deposits indicate not only the development of permafrost (ice-wedge pseudomorphs) and decreased humidity (composite wedge casts) but also the degradation of permafrost (large-scale involutions) and, finally, the establishment of deep seasonal frost (frost cracks). The diversity of structures in the study region appears to result from local conditions rather than increasing continentality of climate towards the east. [ABSTRACT FROM AUTHOR]

Recent investigations into relict periglacial phenomena in northern and western China and on the Qinghai- Tibet Plateau provide information for delineating the extent of permafrost in China during the Late Pleistocene. Polygonal and wedge-shaped structures indicate that, during the local Last Glacial Maximum ( LLGM, between ∼35 and 10.5 ka BP), the southern limit of latitudinal permafrost in northern China advanced southward at least to ∼38-40° N in the east and to ∼37-39° N in the west. This represents an advance of about 5-10° of latitude beyond present-day permafrost limits. The lower limits of elevationally controlled permafrost on the Qinghai- Tibet Plateau and its peripheries were about 1000 m lower: this permafrost was largely continuous during the LLGM. This suggests a cooling of between 4 and 10° C, or more. This paper discusses the extent of permafrost during the LLGM and presents maps that have been constructed on the basis of extensive and integrative analysis of all reliable and pertinent data. The results indicate that the extent of LLGM permafrost in China was between ∼3.8 and 4.3×106 km2. This is 80 to 100% more than that of ∼2.15×106 km2 in the 1970s, and 120 to ∼150% more than that of ∼1.75×106 km2 today. [ABSTRACT FROM AUTHOR]

Thermal regimes of eight periglacial talus slopes, at contrasting elevations, aspects, and substrates, in the Sierra Nevada, California, had complex microclimatic patterns partially decoupled from external conditions. Over three years, warm seasons showed mean talus matrix temperatures and daily variances lower than surfaces and cooler than free-air; talus surface and matrix positions low in the taluses were colder than higher positions, yielding highly positive altitudinal temperature differentials; ground surface temperatures had greater daily extremes than talus positions; and talus matrix temperatures lagged in response to surface temperature changes. Regulating processes in summer include evaporative cooling, cold-air drainage and Balch effect, and shading effects. In the cold season, talus matrices were warmer than surfaces; low talus positions were warmer than high; isothermal zero-curtain periods occurred before snow disappearance; and snow covered talus low positions more often and longer than higher in the taluses, which were often snow-free. Winter thermal processes likely include insulation from snow cover at talus bases, free exchange between talus matrix and external air in the upper talus, and latent heat from thaw-refreezing in late winter. Permanent ice may occur within high elevation talus slopes. Partially decoupled talus thermal regimes provide buffered habitats for mammals such as American pikas and are likely to be important refugia under future warming. [ABSTRACT FROM AUTHOR]

In the highest land of the Sierra Nevada National Park, an experiment to monitor solifluction rates together with the thermal regime of the ground was implemented during the period 2005-2011. Data show evidence of the low activity of solifluction processes in the present-day periglacial belt of Sierra Nevada. Annual displacement rates were lower than 1 cm yr-1 both in northern and southern slopes. Solifluction was more active near snow patches and streams. Rates were also higher during snowier years. Soil temperatures showed seasonal frost occurrence, though the depth and duration of the frozen layer is strongly conditioned by the annual snow cover. Water availability appears to be a crucial factor for solifluction processes in this semiarid environment. [ABSTRACT FROM AUTHOR]

ABSTRACT During the Late Pleistocene, East Anglia experienced multiple cycles of periglacial activity. This research investigates whether chalkland patterned ground infilled with coversand developed during one or more glacial cycles or only during the last period of intensive periglacial activity to affect lowland Britain. Single grain luminescence ages from polygons and stripes at six sites in East Anglia suggest that the patterns experienced multiple phases of activity during the last 90-10 ka but do not date back to earlier glacial cycles. This activity is attributed to four main phases: (1) ∼55-60 ka, (2) ∼31-35 ka, (3) ∼20-22 ka and (4) ∼11-12 ka. Most sites show some activity around the Greenland Stadial 2a and the Younger Dryas Stadial, but polygons show a longer, more temporally and spatially varied record than stripes. Interpreted phases of activity mostly coincide with stadials within the last glacial-interglacial cycle, possibly at the end of climatic cold phases. [ABSTRACT FROM AUTHOR]

Abstract: Gale crater is a ~154-km-diameter impact crater formed during the Late Noachian/Early Hesperian at the dichotomy boundary on Mars. Here we describe potential evidence for ancient glacial, periglacial and fluvial (including glacio-fluvial) activity within Gale crater, and the former presence of ground ice and lakes. Our interpretations are derived from morphological observations using high-resolution datasets, particularly HiRISE and HRSC. We highlight a potential ancient lobate rock–glacier complex in parts of the northern central mound, with further suggestions of glacial activity in the large valley systems towards the southeast central mound. Wide expanses of ancient ground ice may be indicated by evidence for very cohesive ancient river banks and for the polygonal patterned ground common on the crater floor west of the central mound. We extend the interpretation to fluvial and lacustrine activity to the west of the central mound, as recorded by a series of interconnected canyons, channels and a possible lake basin. The emerging picture from our regional landscape analyses is the hypothesis that rock glaciers may have formerly occupied the central mound. The glaciers would have provided the liquid water required for carving the canyons and channels. Associated glaciofluvial activity could have led to liquid water running over ground ice-rich areas on the basin floor, with resultant formation of partially and/or totally ice-covered lakes in parts of the western crater floor. All this hydrologic activity is Hesperian or younger. Following this, we envisage a time of drying, with the generation of polygonal patterned ground and dune development subsequent to the disappearance of the surface liquid and frozen water. [Copyright &y& Elsevier]

Abstract: Periglacial landscapes comprise landforms that are inherently 3D structures, often exhibiting small-scale spatial heterogeneity of surface and subsurface conditions. The objectives of the present paper are to illustrate the potential of the novel application of 3D electrical resistivity imaging for mapping frozen ground conditions exemplified by three case studies with different geomorphological problems to be addressed and to consider the efficacy of the 3D approach to geomorphological investigations in mid-latitude high alpine and high latitude lowland permafrost environments. The approach described in the three case studies includes reconnaissance surveys using two-dimensional electrical resistivity tomography (2D ERT) followed by a detailed mapping using three-dimensional electrical resistivity imaging (3D ERI). The latter approach enables a spatial imaging of the subsurface resistivity distribution and clearly improves the delineation and characterization of subsurface structures compared to state-of-the-art 2D ERT that is limited to findings gained along single profiles or extrapolation between several profiles. Although it can be challenging and time-consuming to apply this technique in periglacial environments, the promising results demonstrate its value for the 3D delineation of frozen ground conditions. In the case of the described case study sites, characterizing the subsurface heterogeneity is close to impossible using drilling or 2D geophysical surveying alone because of the complex 3D nature of the frozen ground characteristics comprising permafrost and permafrost-free areas (alpine permafrost test site) as well as permafrost with variable characteristics (subarctic lowland permafrost test site) at close distance. Even in environments that seem homogeneous at first sight, this method allows us to detect substantial subsurface property variations that can be attributed to different frozen ground conditions. Furthermore, 3D ERI allows the linking of different data sources (e.g., site-specific geomorphology and hydrology) to enhance the spatial understanding of surface and subsurface characteristics and dynamics in permafrost environments. The improved knowledge of the geophysical anatomy and subsurface architecture of the permafrost occurrences revealed by this study suggests a more widespread use for glacial and periglacial landform studies in the future. [Copyright &y& Elsevier]

Knight, J., Burningham, H., 2014. A paraglacial coastal gravel structure: Connell's Bank, NW Ireland. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 121-126, ISSN 0749-0208. Coastal gravel structures have been well documented worldwide and are formed dominantly by onshore wave transport of gravel, mainly during storm events. They are commonly observed along paraglacial coastlines where their origins are more ambiguous because of the effects of antecedent patterns of sediment supply, glacioisostatic sea-level change, and contemporary coastal processes. This paper describes the properties and polygenic origin of Connell's Bank, a small paraglacial gravel structure on the Atlantic-facing coast of NW Ireland. This feature has been shown on historical maps, air photos and satellite imagery since ca. 1850 but its outline has varied depending on seasonal migration, expansion and contraction of a sand veneer. It has also acted as a major control on tidal channel position within the estuary, and thus on sensitivity of the estuary system to ocean forcing. In detail, the bank surface is composed of cobbles sourced from outside of the immediate catchment. These surface cobbles are strongly winnowed, forming a lag deposit, whereas below the surface, cobbles exist within a granule and shell matrix. A significant proportion of surface cobbles show evidence for recent ventifaction by blown sand at low tide. The paraglacial evolution of Connell's Bank since the last glaciation comprises the following stages: (1) deposition of coarse glacigenic sediment as a moraine or proximal outwash fan during the late Pleistocene lowstand; (2) reworking of sediments onshore during early Holocene sea-level rise; (3) surface winnowing during mid to late Holocene tides and storms; and (4) surface cobble modification by contemporary wind abrasion. [ABSTRACT FROM AUTHOR]

ABSTRACT Environmental factors that affect the activity-inactivity variation of periglacial features may differ from those factors that control the distributional patterns of active features. To explore this potential difference, a statistically based modelling approach and comprehensive data on active and inactive cryoturbation and solifluction features from a subarctic area of Finnish Lapland are investigated at a landscape scale. In the cryoturbation modelling, vegetation abundance is the most important environmental variable explaining both the activity-inactivity variation and the distribution of active sites. The next most important variables are soil moisture and (micro)climatological conditions in the activity modelling, and slope angle and ground material in the distribution modelling. For solifluction, the key variables determining the activity-inactivity variation are mean annual air temperature and mean maximum snow depth, whereas vegetation abundance and slope angle control the distribution of active sites. Comparison between the environmental conditions of active and inactive periglacial features may provide new insights into activity-environment relationships, which in turn are valuable when the effects of climate change on periglacial processes are explored. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT Automated monitoring that combines time-lapse photography and sensor-based data logging can elucidate the environmental conditions, processes and rates of soil movement on remote periglacial hillslopes. This study presents the results from 5 years of time-lapse photography of soil movements, supported by time series data on frost heave, soil temperature, soil moisture and surface weather, on an alpine stone-banked lobe subject to frequent diurnal freeze-thaw cycles and deep seasonal frost on Mt Ainodake in the Japanese Alps. The lobe is dominated by biannual shallow soil movements, mostly originating from diurnal frost heave by needle ice or shallow ice lens formation and approximated by potential frost creep. The surface velocity shows a small interannual variation mainly reflecting snow conditions that control the spatio-temporal variability of freeze-thaw action, while it is independent of mean annual air temperature that influences the intensity of seasonal freezing. Occasional rill erosion occurs when the topmost frozen soil is rapidly thawed and super-saturated by intensive rainfall during seasonal thawing periods. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The knowledge of past permafrost conditions is of importance to assess the potential magnitude of changes that periglacial environments may experience as a result of climate warming or disturbance. To assess if past thaw unconformities may be preserved from isotopic and geochemical discontinuities within permafrost, this study investigates the distribution of ground ice, stable water isotopes and major cations in two permafrost cores collected in a hummocky terrain site near Inuvik, Northwest Territories, Canada; a site where the evolution of the active layer during a recent period of permafrost degradation and subsequent aggradation was documented. Based on the high-resolution isotope geochemistry profiles, closed-system Rayleigh-type ionic segregation and isotope fractionation occurred during thermally-induced water migration into shallow permafrost and its freezing along a negative soil temperature gradient. Due to thermally-induced water migration into permafrost, δ18O may not always be able to identify thaw unconformities; however the calculation of the 18O enrichment factors between ice and water (ε18Oi−w) may be used to determine position of thaw unconformities in permafrost, if thaw events are followed by permafrost aggradation. The approach of using ε18Oi−w provides additional information regarding past permafrost conditions that can complement change in cryostructures observed along natural exposures. [Copyright &y& Elsevier]

Fire is a key factor controlling global vegetation patterns and carbon cycling. It mostly occurs under warm periods during which fuel builds up with sufficient moisture, whereas such conditions stimulate fire ignition and spread. Biomass burning increased globally with warming periods since the last glacial era. Data confirming periglacial fires during glacial periods are very sparse because such climates are likely too cold to favour fires. Here, tree occurrence and fires during the Upper Pleistocene glacial periods in Central Canada are inferred from botanical identification and calibrated radiocarbon dates of charcoal fragments. Charcoal fragments were archived in sandy dunes of central Saskatchewan and were dated >50 000-26 600 cal BP. Fragments were mostly gymnosperms. Parallels between radiocarbon dates and GISP2-δ18 O records deciphered relationships between fire and climate. Fires occurred either hundreds to thousands of years after Dansgaard- Oeschger ( DO) interstadial warming events (i.e., the time needed to build enough fuel for fire ignition and spread) or at the onset of the DO event. The chronological uncertainties result from the dated material not precisely matching the fires and from the low residual 14C associated with old sample material. Dominance of high-pressure systems and low effective moisture during post- DO coolings likely triggered flammable periglacial ecosystems, while lower moisture and the relative abundance of fuel overshadowed lower temperatures for fire spread. Laurentide ice sheet ( LIS) limits during DO events are difficult to assess in Central Canada due to sparse radiocarbon dates. Our radiocarbon data set constrains the extent of LIS. Central Saskatchewan was not covered by LIS throughout the Upper Pleistocene and was not a continental desert. Instead, our results suggest long-lasting periods where fluctuations of the northern tree limits and fires after interstadials occurred persistently. [ABSTRACT FROM AUTHOR]

Researches carried out on the main glacier of the Dovrefjell massif, Scandes Mountains, Norway (62° N; 9° E) point to recent periglacial features which are presently directly developed on the ice. This original location raises the problem of their morphodynamic significance and a hypothesis of ephemeral periglacial activity in a paraglacial context is proposed here. [ABSTRACT FROM AUTHOR]

Abstract: The buzzsaw hypothesis refers to the potential for glacial and periglacial processes to rapidly denude mountains at and above glacier Equilibrium Line Altitudes (ELAs), irrespective of uplift rates, rock type or pre-existing topography. Here the appropriateness of the buzzsaw metaphor is examined alongside questions of the links between glacial erosion and ELAs, and whether the glacial system can produce low-relief surfaces or limit summit heights. Plateau fragments in mountains on both active orogens and passive margins that have been cited as products of glacial and periglacial buzzsaw erosion instead generally represent dissected remnants of largely inherited, pre-glacial relief. Summit heights may correlate with ELAs but no causal link need be implied as summit erosion rates are low, cirque headwalls may not directly abut summits and, on passive margins, cirques are cut into pre-existing mountain topography. Any simple links between ELAs and glacial erosion break down on passive margins due to topographic forcing of ice-sheet growth, and to the km-scale vertical swaths through which ELAs have shifted through the Quaternary. Glaciers destroy rather than create low-relief rock surfaces through the innate tendency for ice flow to be faster, thicker and warmer along valleys. The glacial buzzsaw cuts down. [Copyright &y& Elsevier]

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Boulder-dominated landforms of periglacial, paraglacial and related origin constitute a valuable, but often unexplored source of palaeoclimatic and morphodynamic information. The timing of landform development initiation and its subsequent stabilization can be linked to past climatic conditions offering the potential to reconstruct cold climatic periods. In this study, Schmidt-hammer exposure-age dating (SHD) was applied to a variety of boulder-dominated landforms (sorted stripes, blockfield, rock-slope failure, paraglacial alluvial fan) in Rondane, eastern South Norway for the first time. On the basis of old and young control points a regional SHD calibration curve was established and successively utilized for the calculation of surface exposure ages for individual landforms. The chronological investigation of development and stabilization of the respective landforms permitted an assessment of Holocene climate variability in Rondane and its impact on overall landform evolution. Our obtained SHD age estimates ranged from 11.44 ± 1.22 ka (ST-D2) to 4.09 ± 1.51 ka (AF1) showing their inactive and relict character. Most surface exposure ages for sorted stripes clustered between 9.88 ± 1.35 ka and 9.25 ± 1.21 ka, hence indicating stabilization during the late stage of the Erdalen Event or shortly thereafter. It is inferred that the blockfield formed prior to the Last Glacial Maximum, was protected by cold-based ice throughout glaciation and shortly reactivated during the Erdalen Event only to subsequently becoming inactive. The surface exposure age of a rock-slope failure (7.58 ± 0.73 ka) falls into the early phase of the Holocene Thermal Maximum (HTM, ~8.0–5.0 ka). This indicates permafrost degradation and/or increasing hydrological pressure negatively influencing slope stability. The paraglacial alluvial fan with its four subsites yielded ages between 8.73 ± 1.63 ka and 4.09 ± 1.51 ka. The old exposure ages point to fan aggradation following regional deglaciation due to paraglacial processes, whereas the younger ages can be explained by increasing precipitation during the onset neoglaciation at ~4.0 ka. Our results underline the importance of meltwater for the activation of periglacial landforms in a continental climate and indicate that the Erdalen Event and immediately following onset of the HTM had major impact on landscape evolution in Rondane. Our obtained surface exposure ages from boulder-dominated landforms in Rondane give important insights into the local palaeoclimatic variability during the Holocene. • Successful application of Schmidt-hammer exposure-age dating • First surface exposure ages of peri- and paraglacial landforms from Rondane • Stabilization of landforms during a late stage of the Erdalen Event • Lack of moisture due to continentality was compensated by meltwater supply. • Paraglacial alluvial fan development steered by debris flows throughout the Holocene [ABSTRACT FROM AUTHOR]

Abstract: Comparison of Martian hillside gullies with terrestrial analogues is a productive method for gaining an understanding of how surface processes operate on Mars and on Earth as well as their similarities and differences. Here we compare gullies within a semiarid region of Island Lagoon near Woomera, Australia, and periglacial gullies located at Pasture Hill, New Zealand, with the Martian gullies in Noachis Terra. We discovered that fluvial processes dominate erosion at the terrestrial sites, though in different forms. Concentration of overland flow and the presence of a resistant cap rock have played a key role in the location and shape of the Island Lagoon gullies. The presence of steeper slopes and a greater abundance of volatiles such as water, frost, and snowmelt at Pasture Hill have helped carve channels equivalent in size to the Martian gullies; and the interaction of frost, dry flows, snowmelt, and debris flows has led to a complex regime of gully erosion and deposition. The observation of similar features on Mars suggests that Martian gully formation is not necessarily restricted to a single process. In addition, gully slopes are closely related to those of their host escarpment as well as the thickness of erodible material and presence of bedrock. Traditional indicators of water-related activity such as slope and sinuosity need to be placed into the context of the environment of the study site. [Copyright &y& Elsevier]

Abstract: The presence of angular bedrock-derived debris on mountain summits worldwide has usually been associated with present or past periglacial frost shattering, thermal fracturing and other climatically-mediated weathering processes. Climatic inferences are commonly made based on such geomorphological evidence, even if frost shattering and other processes are unlikely under present climatic conditions. This paper questions this assumed genetic link between present/past climate and production of angular bedrock-derived debris by describing the geomorphological impacts of lightning strikes on exposed mountain summits. Using examples from the high Drakensberg of eastern Lesotho, southern Africa, the impacts of lightning strikes are described, which include the generation of angular, fractured bedrock-derived debris. These impacts are identified in the field based on clear and unambiguous criteria that can be used to distinguish between lightning-induced weathering processes and those processes associated with ‘more typical’ alpine weathering. This paper argues that lightning strikes are an important geomorphic agent of, in particular, low-latitude mountain summits, and that to make uncritical climatic inferences based on the presence of ‘frost shattered debris’ on mountain summits is wholly erroneous. [Copyright &y& Elsevier]

Recently, the investigation of Mars is carried Out by space probes. Satellite images, DEMs and other types of planetary datasets can be integrated and analyzed in GIS software environment. I have investigated two groups of water ice-related Martian slope landforms in eight study areas. The periglacial debris aprons of mid-latitudinal regions developed in the last few hundred million years, as a result of the slow downslope movement and plastic deformation of rock-ice mixtures with cemented inner structure. Nowadays these are inactive or fossil landforms, indicating different climatic conditions in the past. The dark slope streaks on the dune fields of the sub-polar regions are the surface signatures of the pore volume-filling downslope seepage of liquid interfacial H2O, originating from the near-surface material in recent spring/summer periods. These two different types of ice-related slope landforms can be explained by the same process: partial melting of water ice in the shallow subsurface layers. Therefore, both can be considered as reliable locations and reachable sources of H2O reservoirs to be found on the planet. [ABSTRACT FROM AUTHOR]

ABSTRACT Rock glaciers near the Andean mountains of central and northwestern Argentina provide an important supply of water for agriculture, but data on their number, size, geographic distribution and altitudinal range are poorly known. Here, we provide the first detailed rock glacier inventory of the Valles Calchaquíes region of Salta, Argentina, based on 2.5 m x 2.5 m resolution Advanced Land Observing Satellite PRISM (Panchromatic Remote-sensing Instruments for Stereo Mapping) satellite images. Rock glacier outlines were manually digitised and a total of 488 were identified, which cover a total area of c. 59 km2. The lower limits of intact and fossil rock glaciers are at c. 4300 m asl and 4100 m asl, respectively. Because rock glaciers are protected by law in Argentina, the inventory provides an important basis for political decision-making about water resources and for further periglacial and environmental studies in this region. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Upfreezing is an important geomorphic process in the periglacial environment. It is a product of cold climate and thus an important part of the cryospheric processes. Based on the long-term positioning observations in the source area of the Urumqi River, this article represents an in-depth discussion of the characteristics of sorted circles and upfreezing mechanisms in the Tianshan Mountains. In the source area of the Urumqi River, the intensity of upfreezing is the highest within the top 25 cm near the surface, while targets with a diameter of 3 cm are least affected by upfreezing. There is no distinct difference between the centre with fine grains and the margin with coarse debris within the same sorted circle in terms of the intensity of upfreezing. The correlation analysis demonstrates that temperature plays an important role in upfreezing and the development of sorted circles. A long-time positioning observation of sorted circles reveals that periglacial landforms are sensitive to regional climate change and respond quickly to the temperature increase of the recent two decades. Enhanced upfreezing was found to be due to increased soil moisture content. [ABSTRACT FROM AUTHOR]

Highlights: [•] Different implementations of the same ice history produce artefacts. [•] Synchronization of RSL simulated with different ice history is not trivial. [•] Different implementations of the same ice history produces up to 5% of difference in GIA corrections for GRACE data. [ABSTRACT FROM AUTHOR]

Abstract: We study the paraglacial activity in Gredos Gorge, a glaciated valley of Sierra de Gredos (Central Spain), using geomorphic markers, stratigraphy and an approach based on OSL. We use luminescence signals from debris flow and fluvial deposits as well as OSL dating of three deposits to detect the main paraglacial processes in Gredos Gorge. We identify two major phases of paraglacial activity during and after the retreat of Last Glacial Maximum (LGM) glaciers. The first phase consisted of high discharge debris flows, sourced up-valley, triggered during the deglaciation. The second phase started ~11ka and is characterized by two processes: (1) the triggering of low discharge debris flows sourced on the flanks of moraines, and (2) the reworking of paraglacial deposits by rivers. Our results of OSL signals, stratigraphy markers and sediment volume indicate that during and after the deglaciation of Gredos Gorge, paraglacial sediment was depleted as theory predicts. However, glacigenic sediments have not been transferred to sediment sinks as long as ~70% of glacial deposits are still stored in the valley. The transition of the environmental conditions prevailing during the LGM to current Mediterranean climate seems to play an important role in delaying the exhaustion model of glacially-conditioned sediment release. We propose that the poor coverage of vegetation driven by the Mediterranean climate prevents the stabilization of glacigenic sediment that is only mobilized during high discharge events responding to extreme rainfalls. [Copyright &y& Elsevier]

To explore thermal regimes and hydrologic capacity of rock glaciers and related periglacial talus landforms, mini-thermochrons were deployed in and around potentially ice-embedded features of the Sierra Nevada. Results from pilot studies at 13 rock glaciers and 7 taluses indicate that outlet springs from these landforms generally do not desiccate but persist year-round as ice (frozen) in winter and flowing water in the warm season. Temperatures of water (liquid and ice) in rock-glacier outlet springs had an annual mean of −0.2 °C and mean of 0.6 °C during the warm season with very low diurnal fluctuation. These and other attributes suggest the existence of internal ice and/or permafrost supplying the springs. Air temperatures of rock-glacier matrices (1 m below the surface) versus surface air corroborate the periglacial nature of internal environments: annual air temperatures of matrices were below freezing (mean, −0.8 °C). Compared to surface air, especially during the warm season, matrix air temperatures were significantly colder and fluctuated less. Talus landforms followed a similar pattern, although water- and matrix air temperatures were warmer, and contrasts with surface air were not as strong as for rock glaciers. For rock glaciers and talus slopes, matrix air temperatures showed resistance (buffering) to changes in external air temperatures. Unique geomorphic conditions of rock glaciers and periglacial taluses in the Sierra Nevada appear to maintain cool-buffered thermal regimes at least partly decoupled from external air. Springs support persistent wetlands and lakes at their snouts, retaining water in otherwise semi-arid high cirques, and contribute as hydrologic reserves and critical habitat for alpine biota. Daily and seasonal lags and buffering effects suggest that ice within these landforms might resist surface warming on the longer term, which could make these landforms increasingly important as regional climates change. [ABSTRACT FROM AUTHOR]

Abstract: Retrogressive thaw slumps are one of the most dramatic thermokarst landforms in periglacial regions. This study investigates the impacts of one stable and two active thaw slumps on the geochemistry of streams in the Stony Creek watershed (Peel Plateau, NWT, Canada). The objective of this study is to elucidate the geochemical processes associated with ground ice ablation in retrogressive thaw slumps and the geochemical evolution of slump runoff to streams. This is accomplished by describing the geochemical composition of runoff across active mega-slumps, impacted and pristine tundra streams, as well as that of the ice-rich permafrost exposed in the slump headwalls. In the Stony Creek watershed, runoff derived from active and stable thaw slumps is characterized by a Ca(Mg)–SO4 geochemical facies with conductivity and solute concentrations approximately one order of magnitude higher than in pristine streams. The elevated solute concentrations in the slump runoff are directly related to thawing of highly weatherable Late Pleistocene age ice-rich and solute-rich permafrost exposed in the headwalls of slumps, which has solute concentrations nearly 100 times higher than those measured in the uppermost 1–2m (i.e., above the early Holocene thaw unconformity). An examination of ionic relations revealed a strong relation between Ca2+ and SO4 2− and (Ca2++Mg2+)–SO4 2−, suggestive that sulfate dissolution is the main process responsible for the geochemical composition of slump impacted streams. Thaw slumps significantly impact the geochemistry of streams, by increasing their solute load well above that of pristine streams along any reach of impacted streams. Unlike shallow active layer disturbances, the thaw slumps can degrade permafrost to depths of 10m or more and the impacts of abundant slump activity on stream geochemistry can be detected at the 10^2 km2 watershed-scale. [Copyright &y& Elsevier]

The study of snow avalanches and their geomorphological effect in the periglacial parts of the cryosphere is important for enhanced geomorphological process understanding as well as hazard-related studies. Only a few field studies, and particularly few in the High Arctic, have quantified avalanche sedimentation. Snow avalanches are traditionally ranked behind rockfall in terms of their significance for mass-wasting processes of rockslopes. Cornice fall avalanches are at present the most dominant snow avalanche type at two slope systems, called Nybyen and Larsbreen, in the valley Longyeardalen in central Svalbard. Both slope systems are on northwest-facing lee slopes underneath a large summit plateau, with annual cornices forming on the top. High-frequency and magnitude cornice fall avalanching is observed by daily automatic time-lapse photography. In addition, rock debris sedimentation by cornice fall avalanches was measured directly in permanent sediment traps or by snow inventories. The results from a maximum of seven years of measurements in a total of 13 catchments show maximum mean rock debris sedimentation rates ranging from 8.2 to 38.7 kgm-2 at Nybyen, and from 0.8 to 55.4 kgm-2 at Larsbreen. Correspondingly, avalanche fan surfaces accreted from 2.6 to 8.8mmyr-1 at Nybyen, and from 0.2 to 13.9mmyr-1 at Larsbreen. This comparably efficient rockslope mass wasting is due to collapsing cornices producing cornice fall avalanches containing large amounts of rock debris throughout the entire winter. The rock debris of different origin stems from the plateau crests, the adjacent free rock face and the transport pathway, accumulating distinct avalanche fans at both slope systems. Cornice fall avalanche sedimentation also contributed to the development of a rock glacier at the Larsbreen site during the Holocene. We have recorded present maximum rockwall retreat rates of 0.9mmyr-1 at Nybyen, but as much as 6.7mmyr-1 at Larsbreen, while average Holocene rockwall retreat rates of 1.1mmyr-1 at Nybyen have been determined earlier. As cornice fall avalanches are the dominant type of avalanche in central Svalbard, the related geomorphological effect is assumed to be of significance at periglacial landscape scale. A climate-induced shift in prevailing winter wind direction could change the rockslope sedimentation effectively by changing the snow avalanche activity. [ABSTRACT FROM AUTHOR]

ABSTRACT Three relict talus-foot rock glaciers at Øyberget, upper Ottadalen, were dated using high-precision Schmidt hammer exposure-age dating (SHD). A SHD calibration curve was constructed for the local banded gneiss using two control points: (1) fresh bedrock in a road cutting; and (2) glacially scoured bedrock surfaces deglaciated c. 9.7 ka. Two alternative hypotheses are suggested to explain SHD ages (± 95% confidence intervals) of 10 340 ± 1280, 9920 ± 1385 and 8965 ± 1700 years obtained for the three rock glaciers located ~ 1000 m below the present lower limit of mountain permafrost, at a site covered by glacier ice throughout the Late Weichselian. First, the rock glaciers may be paraglacial features, which formed rapidly during deglaciation when enhanced debris supply may have buried residual ice bodies. If this was the case, the SHD ages are a true reflection of rock glacier age. Second, the rock glaciers may have formed during several thousand years of permafrost conditions in the Mid-Weichselian (possibly during the Ålesund Interstadial, c. 34.5-38.2 ka) and then been preserved beneath a cold-based ice sheet until renewed exposure during Holocene deglaciation. If the second hypothesis is true, then the true age of the rock glaciers is much older than their SHD ages, the latter failing to record the interval of burial when rock weathering would have been zero. Although evidence is currently insufficient to distinguish between these two interpretations, the paper demonstrates both the potential and limitations of high-precision SHD in the context of rock glaciers. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT The influence of past microclimates on the morphology and distribution of clasts is considered for relict large-scale sorted polygons in the Krkonoše Mountains (Czech Republic). Sixty-two sorted polygons with an average length of 194 cm and an average height of 21.5 cm were measured at four sites on Mt Luční hora, at elevations of 1455 to 1555 m asl. The polygons consist of tabular clasts with a mean length of 11 cm at the borders and 5 cm in the interiors. Smaller polygons are better sorted because of the shorter distances for the clasts to reach their borders. Polygons with greater relative height are better sorted due to more intensive slope processes associated with differential frost heaving. Better sorted and more domed polygons at higher altitudes suggest more severe and longer-lasting microclimates suitable for the development of sorted polygons. The altitudinal gradient in polygon morphology and sorting suggests the dominant role of microclimate in the periglacial environment of the summit area of the Krkonoše Mountains during the Last Glacial/Holocene period. Polygon development probably involves positive feedback between morphology and frost susceptibility, driven by microclimate. The proposed method for evaluating frost sorting allows for rapid non-invasive assessment of sorting using modern methods including high-resolution remote sensing (especially terrestrial photogrammetry). Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

During the deglaciation stages of the last glacial period a rock avalanche took place on the glacier that occupied the upper sector of the Cuerpo de Hombre Valley ( Sierra de Béjar). The material displaced during the avalanche fell onto the ice, was transported by the glacier and later deposited as supraglacial ablation till. The cause of the avalanche was the decompression of the valley slopes after they were freed from the glacier ice (stress relaxation). Reconstruction of the ice masses has been carried out to quantify the stress relaxation that produced the collapse. The rock avalanche took place on a lithologically homogeneous slope with a dense fracture network. The avalanche left a 0.4 ha scar on the slope with a volume of displaced material of 623 ± 15 × 103 m3. The deposit is an accumulation of large, angular, heterometric boulders (1-100 m3 in volume) with a coarse pebble-size matrix. The avalanche can be explained as a relaxation process. This implies rock decompression once the glacier retreat left the wall ice free (debuttressing). Calculations show that the avalanche took place where the decompression stresses were highest (130-170 kPa). In the Spanish Central System paleoglaciers the largest accumulation of morainic deposits occurred after the glacial maximum and the earliest stages of the ice retreat. The process described here is used as an example to formulate a hypothesis that the largest accumulations of tills were formed in relation to enhanced slope dynamics once some glacier retreat had occurred. [ABSTRACT FROM AUTHOR]

Abstract: Geophysical survey by Automatic Resistivity Profiling (ARP©) system of the Pierrelaye–Bessancourt area revealed remarkable conductive polygon patterns of 20- to 30-m diameter detected between 0.5- and 1.7-m depth. Trenches dug down to the limestone substrate allowed detailing of the pedological and lithological units that compose such polygonal features. The patterns are formed by greenish glauconite and carbonated sand hollows where clay-rich pedological horizons bend downward, forming narrow tongs extending up to 2- to 3-m depth. Such structures were interpreted as a buried polygonal ice-wedge network (thermokarst depressions). Geometrical relationships between the lithological units and consecutive erosional surfaces allowed the identification of successive landscape events and a landscape chronology. The sequence started during the Saalian glaciation with (1) the development of patterned grounds by thermokarstic cryoturbation; (2) the consecutive deflation/erosion during post-permafrost aridity; (3) the loess and eolian sand deposits; (4) the weathering of the former deposits with development of pedogenic horizons during the Eemian interglacial; (5) the recurrent cryoturbation and thermal cracking leading to infolding of the pedogenic horizons during the Pleniglacial optimum (Weichselian); and finally (5) the erosion that levelled the periglacial microreliefs, most probably during the last glacial stage (Weichselian), leading to the modern landscape. In this agricultural area, urban waste water has been spread for more than 100years by flooding irrigation for food crop production and has led to high levels of metal pollution in the surface horizons of the soils. The polygonal cryogenic structures have major impacts on soil hydrology and dispersion/distribution of heavy metals toward the geological substrate. Such structures are essential to consider when conceiving proposals for future soil management of this polluted area. [Copyright &y& Elsevier]

Closed-system pingos (CSPs) are perennial ice-cored mounds that evolve in relatively deep and continuous permafrost. They occur where thermokarst lakes either have lost or are losing their water by drainage or evaporation and by means of freeze–thaw cycling, permafrost aggradation and pore-water migration. The presence of CSPs on Mars, particularly on late-Amazonian Epoch terrain at near-polar latitudes, would indicate: (1) the antecedent occurrence of ponded water at the mound-formation sites; (2) freeze–thaw cycling of this water; and (3) boundary-conditions of pressure and temperature at or above the triple point of water much more recently and further to the north than has been thought possible. In 2005 we studied two crater-floor landscapes in northern Utopia Planitia and used MOC narrow-angle images to describe mounds within these landscapes that shared a suite of geological characteristics with CSPs on Earth. Here, we show the results of a circum-global search for similar crater-floor landscapes at latitudes >∼55°N. The search incorporates all relevant MOC and HiRISE images released since 2005. In addition to the two periglacially suggestive crater-floor landscapes observed by us earlier, we have identified three other crater floors with similar landscapes. Interestingly, each of the five mound-bearing craters occur within a tight latitudinal-band (∼64–69°N); this could be a marker of periglacial landscape-modification on a regional scale. Just to the north of the crater-based pingo-like mounds Conway et al. have identified large (km-scale) crater-based perennial ice-domes. They propose that the ice domes develop when regional polar-winds transport and precipitate icy material onto the floor of their host craters. Under a slightly different obliquity-solution ice domes could have accumulated at the lower latitudes where the putative CSPs have been observed. Subsequently, were temperatures to have migrated close to or at 0°C the ice domes could have thawed, forming endogenic paleolakes. This region also contains a significant concentration of crater-floor polygons. The polygons are thought to have formed by desiccation (El Maarry et al. [2010]. J. Geophys. Res., 115 (E10006)) or thermal contraction (Soare et al. [2005a]. Icarus, 174 (373–382)); on Earth each of these processes is associated with the end-stage of lake evolution. On the basis of our enhanced image collection, a new map displaying the global distribution of mound-bearing craters and a two new digital-elevation models of a crater-floor with pingo-like mounds, we evaluate the CSP hypothesis anew. We also explore two alternative hypotheses: (1) the mounds are weathered central-uplift complexes; or (2) they are impact-related hydrothermal structures. However, we propose that the CSP hypothesis is much more robust than these alternatives, encompassing geomorphological, cartographical, stratigraphical and climatological observations, and less subject to inconsistencies. [ABSTRACT FROM AUTHOR]

Research on colluvial depositional systems has recently emphasized periglacial and high-altitude settings, and the relations between Quaternary slope stratigraphy and climate change. This article examines the role of variable slope morphology, surface hydrology and microclimate in controlling colluvial sedimentation along a coastal tract of the hyperarid Atacama Desert in northern Chile. Direct accessibility of active surfaces is accompanied by uninterrupted stratigraphic exposures along the base of slopes, allowing direct comparisons between surface processes and the resulting sedimentary record. Four slope sectors are identified, based on differences in morphology and processes over active surfaces. Colluvial sedimentation is controlled by complex interactions of slope gradients and profiles, exposure to dominant winds, and potential runoff pathways, which vary considerably between different sectors. Major differences are evident between these hyperarid deposits and slope sedimentation in periglacial and temperate settings, including the complete absence of pedogenic activity and clay minerals; the volume of aeolian deposits and their role in controlling processes which redistribute sediment downslope, extending colluvial aprons; and the occurrence of runoff processes only where favoured by particular topographic configurations. Depositional surfaces range from steep talus cones, to debris-flow-dominated and aeolian-dominated colluvial aprons, to an aeolian ramp subject to reworking by mass flows and flash floods. Consequently, facies associations and architectures at outcrop are highly variable and highlight the importance of spatial variations in slope morphology and processes in producing distinct, coeval colluvial stratigraphies within a single environmental context. Discrepancies between active processes and the corresponding stratigraphic signatures are also evident in some sectors; for example, preservation of alluvial and aeolian facies in stratigraphic sections does not always reflect the dominant processes over active slopes. Together with the spatial variability in processes and deposits along these slopes, this suggests that caution is required when extracting palaeoenvironmental information from analyses of colluvial successions. [ABSTRACT FROM AUTHOR]

Abstract: Located in the foreland of the Western Alps, the Crau Plain was the outlet of the Durance River in the Pleistocene. In order to constrain its geodynamic evolution in terms of chronology and denudation rates, the two main Quaternary deposits of this plain have been studied based on cosmogenic nuclide 10Be concentration measurements along depth profiles. The abandonment of the Miramas and Luquier alluvial surfaces occurred at the beginning of glacial periods, Würm (isotopic stage 4) and Riss (isotopic stage 6), respectively. Discrepancy in denudation rates under similar geomorphological and lithological conditions suggests different denudation processes during glacial and interglacial periods. The denudation rate has been estimated at about 25mmka−1 for the interglacial period and about 60mmka−1 for the glacial period. The abandonment of the Crau Plain as the outlet of the Durance River occurred sometime between 75 and 35ka. [Copyright &y& Elsevier]

Abstract: The Kamienne Mts. in SW Poland abound in geomorphic evidence for past landslides developed at the rhyolite/sedimentary rock contact, but it remains unknown when the displacements occurred. The slopes generally have been stable in the last 200years or so, covered by historical records. In this paper we use the presence of periglacial solifluction layers (cover-beds) and soil characteristics as indicators of the status of hillslopes and relative age of landslides. We follow an assumption that if landslides predate the Holocene, then solifluction layers should be present and soils within and outside landslide-affected slopes should have similar characteristics, allowing for differences caused by local factors. Cover-beds are not expected to be associated with Holocene landslides. Differences in the degree of soil development may be used to argue for different ages of some landslides within the Holocene. The absence of solifluction layers cannot always be regarded as the evidence of post-Pleistocene landsliding since such a layer is unlikely to have ever formed on densely jointed, but otherwise strong, rhyolite. Soil morphological properties, particularly horizonation, helped to establish the relative chronology of mass movement and to recognize both early to mid-Holocene and late Holocene landslides. Soils are good relative-dating tools and their usage does not necessarily require adherence to any particular soil classification system. This is because morphological features of entire profiles provide more information than diagnostic properties used in these systems. [Copyright &y& Elsevier]

Ice-rich permafrost landscapes are sensitive to climate and environmental change due to the melt-out of ground ice during thermokarst development. Thermokarst processes in the northern Yukon Territory are currently not well-documented. Lake sediments from Herschel Island (69°36′N; 139°04′W) in the western Canadian Arctic provide a record of thermokarst lake development since the early Holocene. A 727cm long lake sediment core was analyzed for radiographic images, magnetic susceptibility, granulometry, and biogeochemical parameters (organic carbon, nitrogen, and stable carbon isotopes). Based on eight calibrated AMS radiocarbon dates, the sediment record covers the last ~11,500years and was divided into four lithostratigraphic units (A to D) reflecting different thermokarst stages. Thermokarst initiation at the study area began ~11.5cal ka BP. From ~11.5 to 10.0cal ka BP, lake sediments of unit A started to accumulate in an initial lake basin created by melt-out of massive ground ice and thaw subsidence. Between 10.0 and 7.0cal ka BP (unit B) the lake basin expanded in size and depth, attributed to talik formation during the Holocene thermal maximum. Higher-than-modern summer air temperatures led to increased lake productivity and widespread terrain disturbances in the lake's catchment. Thermokarst lake development between 7.0 and 1.8cal ka BP (unit C) was characterized by a dynamic equilibrium, where lake basin and talik steadily expanded into ambient ice-rich terrain through shoreline erosion. Once lakes become deeper than the maximum winter lake ice thickness, thermokarst lake sediments show a great preservation potential. However, site-specific geomorphic factors such as episodic bank-shore erosion or sudden drainage through thermo-erosional valleys or coastal erosion breaching lake basins can disrupt continuous deposition. A hiatus in the record from 1.8 to 0.9cal ka BP in Lake Herschel likely resulted from lake drainage or allochthonous slumping due to collapsing shore lines before continuous sedimentation of unit D recommenced during the last 900years. [ABSTRACT FROM AUTHOR]