Solifluction Processes Research Articles

High-resolution luminescence-dated sediment record for the last two glacial-interglacial cycles from Rodderberg, Germany

The Rodderberg Volcanic Complex (RVC) is well-known for the long climate record archived in its crater basin, which lasts for several glacial-interglacial cycles. However, a detailed chronological framework is still lacking. Here, we perform high-resolution luminescence dating on a 72.8 m-long sediment core with the optically stimulated luminescence (OSL) signal from fine-grained (4–11 μm) quartz and three kinds of post-infrared infrared (pIRIR) stimulated luminescence signals from fine-grained polymineral fractions. Together with magnetic susceptibility, grain size and quartz OSL sensitivity measurements, a numerical age framework is built for the upper half of the sediment core. Quartz OSL ages align well with pIRIR ages for the last 45 ka, but they underestimate in relation to pIRIR ages for ages beyond 45 ka. The three pIRIR signals, including the pIRIR signal at 225 °C (pIRIR225), the pulsed pIRIR signal at 150 °C (pulsed pIRIR150) and the multi-elevated-temperature pIRIR at 250 °C (MET-pIRIR250), yield consistent ages up to ca. 250 ka at a sediment depth of 37.5 m. Below that depth, dating limits of the protocols are reached. Nevertheless, our results indicate that sediments below 37.5 m predate Marine Isotope Stage (MIS) 7. Altogether, obtained ages reveal continuous dust accumulation during MIS 7 and MIS 6. One erosional event happened at the end of the Eemian (MIS 5e), which eroded the Eemian soil. The sedimentation rate during the Weichselian glacial period is tenfold lower compared to the sedimentation rate observed during MIS 7–6. This low sedimentation rate likely arises from the cessation of slope wash effects and the occurrence of various wind erosional events alternating with dust deposition as the basin is filled by dust. A notably high sedimentation rate is observed at the transition from MIS 6 to the Eemian, marked by the deposition of a 7 m-thick loess layer between 135 and 129 (±5) ka. This high sedimentation rate could be attributed to intensified slope wash and solifluction processes resulting from the thawing of permafrost at the time of deglaciation. Alternatively, it might be a signature of Heinrich event 11, during which strong winds brought large amounts of dust into the basin within a short time.

Periglacial landforms and landscape development in southern England

The south-central and south-east England Geological Conservation Review region is unique in Britain in lying completely outside the margins of Quaternary ice sheets. In view of this, the area has been described as a ‘relict periglacial landscape’. This implies that the region has evolved its current form substantially under the influence of seasonal and/or perennial frost. In fact, modern research has demonstrated that permafrost, either continuous or discontinuous, likely existed across probably the whole of the region at different times during the Quaternary. This has important implications for ground permeability and the strength of sediments and soils and this has, without doubt, influenced landscape development. Whilst the whole region appears to have experienced cold environmental conditions, the landforms, structures and sediments of some sites are particularly associated with periglacial processes. Allington Quarry, Spot Lane Quarry, Oaken Wood, Chiddingly Wood (known locally as Chiddinglye Wood), High Rocks and Rusthall Common have exhibited typical cambering structures with open or closed gulls. The latter three sites also display a fine range of surface weathering features. Hubbard's Hill is characterised by solifluction and active-layer detachment slides and associated subsurface shear structures, whilst the sarsen trains at Fyfield Down and Valley of Stones are also attributed to solifluction processes. Birling Gap and Pegwell Bay exhibit spectacular sediment brecciation and involutions. Pegwell Bay is also known for its thick layer of periglacial loess, a sediment that is also a feature of North Cliff, Broadstairs. Unfortunately, the dating of these landscape features has, so far, proved possible only at Hubbard's Hill and Pegwell Bay. Nevertheless, the sites reviewed here provide exceptional, and in some cases internationally important, indications of landscape development in cold, often permafrost, environments which justifies their status as GCR sites.

Insights on seasonal solifluction processes in warm permafrost Arctic landscape using a dense monitoring approach across adjacent hillslopes

Solifluction processes in the Arctic are highly complex, introducing uncertainties in estimating current and future soil carbon storage and fluxes, and assessment of hillslope and infrastructure stability. This study aims to enhance our understanding of triggers and drivers of soil movement of permafrost-affected hillslopes in the Arctic. To achieve this, we established an extensive soil deformation and temperature sensor network, covering 48 locations across multiple hillslopes within a 1 km2 watershed on the Seward Peninsula, AK. We report depth-resolved measurements down to 1.8 m depth for May to September 2022, a period conducive to soil movement due to deepening thaw layers and frequent rain events. Over this period, surface movements of up to 334 mm were recorded. In general, these movements occur close to the thawing front, and are initiated as thawing reaches depths of 0.4–0.75 m. The largest movements were observed at the top of the south-east facing slope, where soil temperatures are cold (mean annual soil temperatures averaging −1.13 °C) and slopes are steeper than 15°. Our analysis highlights three primary factors influencing movements: slope angle, soil thermal conditions, and thaw depth. The latter two significantly impact the generation of pore water pressures at the thaw–freeze interface. Specifically, soil thermal conditions govern the liquid water content, while thaw depth influences both the height of the water column and, consequently, the pressure at the thawing front. These factors affect soil properties, such as cohesion and internal friction angle, which are crucial determinants of slope stability. This underscores the significance of a precise understanding of subsurface thermal conditions, including spatial and temporal variability in soil temperature and thaw depth, when assessing and predicting slope instabilities. Based on our observations, we developed a factor of safety proxy that consistently falls below the triggering threshold for all probes exhibiting displacements exceeding 50 mm. This study offers novel insights into patterns and triggers of hillslope movements in the Arctic and provides a venue to evaluate their impact on soil redistribution.

A Spatially Detailed Projection of Environmental Conditions in the Arctic Initiated by Climate Change

The environmental conditions of the Arctic are vulnerable to the effects of climate change. We focus on the territory of the Yamalo-Nenets Autonomous Okrug (YaNAO). The objective of this study is to project mid-21st century climate-driven changes in the state of climate and the natural environment in the YaNAO. For this purpose, the CMIP6 data models with the climate change scenario SSP5-8.5 were used. Climate change directly affects the statistics of extreme events and climatically driven phenomena, such as frosts and thaws, as well as avalanches and slush flows. Climate change causes changes in the Arctic environment, primarily due to permafrost degradation, leading to important modifications in events such as mudflows, cryogenic landslides, abrasion, erosion, suffusion, frost heave, solifluction, thermokarst, and others. In some cases, the intensity and area of these processes increase, such as heaving processes and thermokarst becoming more active by 2050. In other cases, the solifluction processes decrease in the south part of the YaNAO due to the discontinuous or sporadic permafrost distribution. Projected climatic changes will inevitably lead to the restructuring of the geosystems in YaNAO, creating risks for infrastructure in economically active territories.

Ice wedge polygon stability on steep slopes in West Greenland related to temperature and moisture dynamics of the active layer

AbstractIce wedge polygons on steep slopes have generally been described as being covered by periglacial sediments and, typically, the active layer on slopes becomes mobile during thaw periods, which can lead to solifluction. In West Greenland close to the ice margin, however, the active layer and ice wedge polygons are stable despite their occurrence on steep slopes with inclinations of ≥30°. We conducted a soil survey (including sampling for soil analyses and radiocarbon dating) in the Umimmalissuaq valley and installed a field station ~4 km east of the current ice margin to monitor soil temperature and water tension at depths of 10, 20 and 35 cm of the active layer on a steep, north‐facing slope in the middle of an ice wedge polygon from 2009 to 2015. Thawing and freezing periods lasted between 2 and 3 months and the active layer was usually completely frozen from November to April. We observed simultaneous and complete water saturation at all three depths of the active layer in one summer for 1 day. The amount of water in the active layer apparently was not enough to trigger solifluction during the summer thaw, even at slope inclinations above 30°. In addition, the dense shrub tundra absorbs most of the water during periods between thawing and freezing, which further stabilizes the slope. This process, together with the dry and continental climate caused by katabatic winds combined with no or limited frost heave, plays a crucial role in determining the stability of these slopes and can explain the presence of large‐scale stable ice wedge polygon networks in organic matter‐rich permafrost, which is about 5,000 years old. This study underlines the importance of soil hydrodynamics and local climate regime for landscape stability and differing intensities of solifluction processes in areas with strong geomorphological gradients and rising air temperatures.

К вопросу об источниках рыхлого материала, причин и мест зарождения катастрофических селей в районе горного массива Мунку-Сардык

The article discusses the results of the summer expedition of 2022 to study high-altitude permafrost-stone lithopotoks and solifluction processes. The materials of the article logically develop ideas about the lithocourses of the region not only of the cryogenic period of their existence, but at the subsequent erosion-proluvial stages of the regular completion, as a result of this, a vertical-age ladder of the main forms of relief of the Munku-Sardyk mountain range was obtained, the places of their localization, the mechanism of occurrence, functioning and further evolution were determined.

Опыт выделения современных и древних снежников горного массива Мунку-Сардык

The article discusses the results of the summer expedition of 2022 to study high-altitude permafrost-stone lithopotoks and solifluction processes. The materials of the article logically develop ideas about the lithocourses of the region not only of the cryogenic period of their existence, but at the subsequent erosion-proluvial stages of the regular completion, as a result of this, a vertical-age ladder of the main forms of relief of the Munku-Sardyk mountain range was obtained, the places of their localization, the mechanism of occurrence, functioning and further evolution were determined.

Increasing Spatio-Temporal Resolution for Monitoring Alpine Solifluction Using Terrestrial Laser Scanners and 3D Vector Fields

This article investigates the usage of terrestrial laser scanner (TLS) point clouds for monitoring the gradual movements of soil masses due to freeze–thaw activity and water saturation, commonly referred to as solifluction. Solifluction is a geomorphic process which is characteristic for hillslopes in (high-)mountain areas, primarily alpine periglacial areas and the arctic. The movement can reach millimetre-to-centimetre per year velocities, remaining well below the typical displacement mangitudes of other frequently monitored natural objects, such as landslides and glaciers. Hence, a better understanding of solifluction processes requires increased spatial and temporal resolution with relatively high measurement accuracy. To that end, we developed a workflow for TLS point cloud processing, providing a 3D vector field that can capture soil mass displacement due to solifluction with high fidelity. This is based on the common image-processing techniques of feature detection and tracking. The developed workflow is tested on a study area placed in Hohe Tauern range of the Austrian Alps with a prominent assemblage of solifluction lobes. The derived displacements were compared with the established geomonitoring approach with total station and signalized markers and point cloud deformation monitoring approaches. The comparison indicated that the achieved results were in the same accuracy range as the established methods, with an advantage of notably higher spatial resolution. This improvement allowed for new insights considering the solifluction processes.

Main problems of the research on the Palaeolithic of Halych-Dnister region (Ukraine)

Abstract The article presents the results of the Palaeolithic loess sites studies in the Halych-Dnister region. It is an area in the Dnister River basin (Ukraine) with a large number of Middle and Upper Palaeolithic sites (Yezupil I, Halych I, Halych II, Mariampil I, Mariampil V, Mezhyhirtsi, Kolodiiv, Hannusivka, etc.), which have been discovered and studied including multilayered ones. It is open-air Palaeolithic sites related to widespread distribution in the region Pleistocene loess-palaeosol sequence reaching up to 30 m thickness, sometimes even more. Palaeolithic sites have been investigated using various field and laboratory archaeological and natural science research methods. Defined cultural horizons of the sites are stratified and dated by luminescent and radiocarbon methods, and their cultural identity is characterized. In the Halych-Dnister region, the most developed are the Middle Palaeolithic (Levallois, Micoquian) cultural horizons as well as the Gravettian techno-complexes of the Upper Palaeolithic. During our research, some scientific problems have been identified in studying the Palaeolithic sites of Halych-Dnister region. They are described in the article. As our practice has shown, issues such as the interpretation of the taphonomy and chronology of archaeological artefacts, the determination of the cultural identity of the archaeological site or particular cultural horizons, the underestimation of the redeposition of cultural layers, the role of palaeorelief and the deluvial–solifluction processes in it, the incompleteness of geological sections of archaeological sites are often debatable among researchers. In the light of the increasing anthropogenic impact on the environment, the issue of rationale, certification and protection of Palaeolithic sites is becoming more urgent. The main purpose of the article is to analyse these issues and find ways to resolve them.

Сравнительное исследование сохранности культуровмещающих отложений на памятнике Мойлтын Ам (Центральная Монголия)

Archaeological sites with unclear conditions of sediment accumulation and stratigraphic disturbances are always complicated to research. Usually other sites in the region with better preservation of cultural layers helps to understand and divide them into cultural chronological stages. However lack of such sites results in the need to find other approaches and research methods to study stratigraphic positions of cultural horizons. Purpose. This article considers approaches and methods and their application to estimate the preservation of cultural layers at the Upper Paleolithic site of Moiltyn Am in Central Mongolia. Results. The authors analyzed positions of artifacts from layers 1.2, 2, 3 and 4. Indexes of layer 1.2 fall within the value range, characteristic to rockfall. Layers 2 and 3 are also close to rockfall, but the level of isotropy falls outside the limits of its range. Layer 4 is closer to the range of solifluction. Conclusions. The authors correlated lithological divisions, revealed in 2018–2019, and stratigraphic units, that previous researchers divided and described. Sediments of Layer 4 were accumulated under the solifluction process and went through post-sedimentological disturbances, that also impacted the underlying layers. Layers 2 and 3 were formed under drier conditions.

Unmanned aerial vehicle‐based mapping of turf‐banked solifluction lobe movement and its relation to material, geomorphometric, thermal and vegetation properties

AbstractSolifluction is one of the most widespread periglacial processes with low annual movement rates in the range of —millimeters to centimeters. Traditional methods to assess solifluction movement usually have low spatial resolution, which hampers our understanding of spatial movement patterns and the factors controlling them. In this study, we (a) test the applicability of unmanned aerial vehicle (UAV)‐based structure‐from‐motion photogrammetry in comparison to a traditional total station survey to map surface movement of a turf‐banked solifluction lobe (TBL) in the Turtmann Valley (Switzerland). We then (b) relate the detected movement patterns to potential geomorphometric, material, thermal and vegetation controls, which we assessed using geomorphic and vegetation mapping, electrical resistivity surveys and temperature loggers. Our results show that (a) UAV‐based mapping can detect solifluction movement with high spatial resolution (one point per m2, total > 900 points) and rates and patterns consistent with a total station survey, but requires careful measurement set‐up and analysis; and (b) movement rates differ between lobe tread, riser and a ridge feature. Differences can be explained by heterogeneous material, geomorphometric, thermal and vegetation properties of the TBL, which promote different solifluction processes. Our study demonstrates the applicability of UAV‐based mapping in solifluction research and improves our understanding of solifluction processes and landform development.

Polychemical pollution of surface waters and permafrost-affected soils in Central and North Yakutia and in North-West Siberia

The concentration of main organic and inorganic pollutants (heavy metals, polyaromatic hydrocarbons, radionuclides) in surface waters and in water-soil solutions was analysed on three keysites within the permafrost zone: Tazovsky Peninsula (North-West Siberia), Kolyma Lowland (North Yakutia) and adjacent to Yakutsk (Central Yakutia). In the majority of sampling points that are not directly impacted by human activity, the pollutants accumulate in the uppermost organogenic and organo-mineral horizons of natural soils. At the human-affected keysites the major pollutants may accumulate not only in the superficial horizons of the disturbed soils due to the surface runoff but also in the central parts of the profile, in the material buried by cryogenic, solifluction or fluvial processes and in some cases – in the suprapermafrost horizons and in the upper layer of permafrost transported via suprapermafrost water runoff.

Smykiv – the new key section of the upper pleistocene of the Volyn Upland

Formulation the problem. The new section at Smykiv in the Volyn Upland has an informative stratigraphic record, showing details of climatic phases in the Late Pleistocene. The site is located in the Rivne Oblast, 40 km south of Lutsk, on slope of the River Dezha (the tributary of the River Styr). Review of previous publications and studies. The loess-palaeosol sequence of the Volyn’ Upland has been intensively studied by Ukrainian, Russian and Polish researchers such as A. Bogucki, M. Lanczont, P. Voloshyn, A. Tsatskin, V. Nechaev, T. Morozova, L. Bezusko, J. Kusiak, S. Fedorowicz, J. Nawrocki, R. Dmytruk and many others. Methods. The section has been studied using lithostratigraphic, palaeopedological, palaeocryological, grain size, micromorphological and partial chemical methods, which enable the reconstruction of past climate and environment. The stratigraphy is applied follows the Quaternary Framework of Ukraine (Veklitch et al., 1993). All the stratigraphical units of the Upper Pleistocene are represented in the section; and, herein, these divided into smaller parts characterized by distinct environmental histories. The purpose of the article is to study the detailed stratified sequence at Smykiv by various methods in order to clarify the regional Quaternary palaeogeographical scheme. Results. The periglacial alluvium of the Dnipro unit, at the base of the sequence, and the analysis of the position of the site in the relief indicate the interpretation that it is located on the Dezha river’s terrace. The alluvium bed is distorted by syngenetic involutions. The overlying Kaydaky unit truncates the alluvium, and is inclined parallel to the present valley slope. Three pedogenetic phases during the Kaydaky times are identifiable: pedosediments formed in the first phase (kda), pedosediments of forest soil formed in the early optimum (kdb1) and a Retisol formed in the late optimum (kdb2). During the Tyasmyn cold event, a network of small soil veins formed. Renewed, but less intense than in the Kaydaky unit, erosion processes started in Pryluky times. It can be demonstrated that the Pryluky polygenetic soil was formed in three phases, divided by a cold event in mid Pryluky times (pl2). A Chernozem with signs of slight podzolisation and biogenic aggregation was formed during the first phase (pl1b2). The soil is disturbed by cryogenic features formed during pl2. An incipient Cambisol was enriched with a fine organic matter during the phase pl3b1. An incipient Calcic Cambisol (pl3b2), aggregated and slightly gleyed, formed at the end of the Pryluky time. Erosion processes were not strongly developed during Pleniglacial. At the beginning of the stadials (in Uday and Bug times), solifluction processes occurred. At the beginning of these stadials, other cryogenic features, such as soil veins, frost fissures and ice-wedges, were also formed. Upper Pleistocene loess beds show slight pedogenesis, particularly very weak humus accumulation and biogenic aggregation. Furthermore, all Pleniglacial units are enriched in carbonates in diverse forms: however, the most common is disperse powdery lime. These last are frequently interpreted as being the result of calcite crystallization under cryogenic processes. During Vytachiv and Dofinivka interstadial times, boreal soils were formed – Gleyic Cambisol and Calcic Gleyic Cambisol, respectively. The first is mostly represented by pedosediments (indicating intense erosion), whereas the second soil is preserved in situ and it is enriched in fine organic matter and is well-microaggregated. The last loess unit of the Upper Pleistocene, the Prychornomorsk loess unit, is subdivided into two loess subunits (pc1 and pc3) which are connected with cryogenic events, and a Gleysol (pc2), indicating a relatively warm period.

New data from the Middle Palaeolithic Cotencher cave (Swiss Jura): site formation, environment, and chronology

Abstract. Cotencher cave is one of the oldest Palaeolithic sites of Switzerland and is known for its rich faunal and Mousterian artefacts, the latter suggesting one or several passages of Neanderthal hunter–gatherer tribes. This interdisciplinary study summarises novel data concerning site formation processes and anthropic attendance of the site. While the lithic artefacts indicate tool production at the site, the faunal remains do not yield any evidence of a link to human occupation. The sedimentary sequence permits us to unravel several important environmental changes that occurred during the Late Pleistocene. The presence of a local glacier around 70 ka (Marine Isotope Stage, MIS 4) is revealed followed by ice-free conditions characterised by alternating soil formation processes and landscape destabilisation during MIS 3. Solifluction processes suggesting recurrent frozen ground were responsible for the displacements of part of the artefacts and faunal remains. Evidence of local glacier development around 36 ka is related to the particular geomorphological conditions of the studied region and shed new light on the complexity of glacier dynamics. The recognition and dating of recurrent hostile glacier landscapes might contribute to understanding the reasons for the Middle and Upper Palaeolithic attendance hiatuses known in the studied region.

Divergence, convergence, and path dependency of paraglacial adjustment of alpine lateral moraine slopes

AbstractLateral moraines represent important sediment storages and are one of the most dynamic areas within glacier forelands. Following glacier retreat, lateral moraine slopes adjust as their material is reworked by paraglacial processes. Previous research focused primarily on the role of gullying, however, path‐dependent slope adjustment and divergent adjustment of lateral moraine slopes are poorly understood. We report data from geomorphic and vegetation mapping, electrical resistivity tomography, soil moisture measurements, and soil texture analysis acquired in the Turtmann glacier foreland in the Swiss Alps where periglacial processes are abundant. We demonstrate that paraglacial slope adjustment shows divergent, convergent, and path‐dependent behaviour. Steep proximal moraine slopes are first eroded by gullying processes. When moraine slopes reach a threshold angle of 30°, the importance of solifluction increases, and solifluction processes subsequently rework debris flow deposits. In contrast, more gently inclined distal slopes are below the threshold angle immediately following glacier retreat and biogeomorphic feedbacks result in an earlier onset of solifluction processes. We identified two different types of turf‐banked solifluction lobes based on their temporal development and genesis. Lobe Type 1 develops on distal moraine slopes and reworks glacial till, whereas Lobe Type 2 evolves from debris flow deposits at the footslopes of the lateral moraines. Both lobe types can only be differentiated using actual shape. Overprinting by subsequent geomorphic processes can result in equifinal and convergent forms such as solifluction sheets from the Last Glaciation. Our study provides an actualistic example of how paraglacial solifluction in 90 to 150 years rapidly reworks glacial sediments.

Depositional and anthropic processes in the Holocene record of the Can Sadurní cave (Begues, Barcelona, Spain): microstratigraphic contributions

The geoarchaeological and microstratigraphic study of the Can Sadurní cave sequence (Begues, Barcelona) reveals the presence of detrital and anthropogenic depositional processes, alternating at certain stages. These influenced the location of the diagenetic processes. The cultural sequence of the site ranges from Epipaleolithic to Late Roman Empire, with some chronocultural interruptions. During the Epipaleolithic and Mesolithic, solifluction processes were responsible for sedimentation. From the Neolithic, mass wasting and colluvial processes were dominant. Dense flows are distinguished mainly during the Cardial Early Neolithic and Early Postcardial. This type of contribution is also present to a lesser extent during the Postcardial Middle Neolithic, Late Neolithic/Chalcolithic and Early Bronze Age. Non-laminated colluvial inputs appear in the rest of the sequence. These episodes alternate with periods of stability, in which the rate of detrital sedimentation is lower or almost non-existent. This is replaced by the presence of in situ stabling areas during the Epicardial and Early Postcardial Neolithic, although evidence is detected from the Cardial Early Neolithic. Associated with these contexts, hydromorphic processes are accentuated leading to the formation of vivianite -an iron phosphate mineral- typical of a reducing medium with high organic matter.

Chronostratigraphy in karst records from the Epipaleolithic to the Mid/Early Neolithic (c. 13.0–6.0 cal ka BP) in the Catalan Coastal Ranges of NE Iberia: environmental changes, sedimentary processes and human activity

The stratigraphic, sedimentary and palaeoenvironmental features reflected in cavities in the Catalan Coastal Ranges of NE Iberia (Can Sadurní and Guineu caves) characterize the periods of pronounced climatic and human complexity that occurred c. 13.0–6.0 cal ka BP. This includes the stages of the Younger Dryas and Mid/Early Holocene, the latter being one of the periods of so-called Rapid Climatic Changes (RCCs). These caves, like others in Mediterranean contexts, are the result of an old duct originating in the saturated zone of the karst system and open to the outside; recording a succession of different detrital and anthropic episodes of the Epipaleolithic, Mesolithic and Neolithic communities.From this study it can be seen that paleoclimatic events do not always present clear signals in the karst records, especially c. 12.7–7.4 cal ka BP, corresponding to the Epipaleolithic and Mesolithic. It is characterized by a stratigraphic discontinuity in which there are phases with predominantly detrital sedimentation alternating with hiatus intervals. Detrital sedimentation formed by fine material colluvium with gravitational movements or solifluction processes in fresh and humid conditions. It appears in the following chronological intervals: 12.7–12.2 cal ka BP, 11.5/11.1–10.7/10.4 cal ka BP and 8.2–8.0 cal ka BP (less humid). Hiatus phases are represented in the rest of the sequence up to c. 7.4 cal ka BP. From the sedimentary point of view these stages of hiatus are indicative of phases of stability or lack of episodes with seasonal contrasts; a fact that would cause interruptions to detrital deposition in the interior of the caves.In contrast, in the period c. 7.4 to 6.0 cal ka BP, attributed to the Middle and Early Neolithic, there is a certain stratigraphic continuity. From the sedimentary point of view it is distinguished by a variability of processes that responds to accumulative episodes of short duration characteristic of morphogenesis of the slopes in an arid Mediterranean environment, identified in our records as RCCs, (c. 7.4–7.2 cal ka BP- Cardial Neolithic; c. 6.8–6.3 cal ka BP-Early Postcardial Middle Neolithic and c. 6.2–5.7 cal ka BP- Late Postcardial Middle Neolithic) alternating with episodes of stability, more humid and coinciding with a better sedimentary record of the pastoral activity in the cavities during Epicardial and Late Cardial Neolithic (c. 7.1–6.7 cal ka BP) and Postcardial Middle Neolithic (c. 6.6–5.9 cal ka BP). It is during this period that Holocene climate variability has better resolution in caves in the Catalan Coastal Ranges of NE Iberia.

Solifluction meets vegetation: the role of biogeomorphic feedbacks for turf‐banked solifluction lobe development

AbstractVegetation is an important factor influencing solifluction processes, while at the same time, solifluction processes and landforms influence species composition, fine‐scale distribution and corresponding ecosystem functioning. However, how feedbacks between plants and solifluction processes influence the development of turf‐banked solifluction lobes (TBLs) and their geomorphic and vegetation patterns is still poorly understood. We addressed this knowledge gap in a detailed biogeomorphic investigation in the Turtmann glacier foreland (Switzerland). Methods employed include geomorphic and vegetation mapping, terrain assessment with unmanned aerial vehicle (UAV) and temperature logging. Results were subsequently integrated with knowledge from previous geomorphic and ecologic studies into a conceptual model. Our results show that geomorphic and vegetation patterns at TBLs are closely linked through the lobe elements tread, risers and ridge. A conceptual four‐stage biogeomorphic model of TBL development with ecosystem engineering by the dwarf shrub Dryas octopetala as the dominant process can explain these interlinked patterns. Based on this model, we demonstrate that TBLs are biogeomorphic structures and follow a cyclic development, during which the role of their components for engineer and non‐engineer species changes. Our study presents the first biogeomorphic model of TBL development and highlights the applicability and necessity of biogeomorphic approaches and research in periglacial environments. Copyright © 2016 John Wiley & Sons, Ltd.

Analysis of the Seepage Due to the Thawing of Permafrost, Considering the Gradient of the Impermeable Layer

Topographical deformation due to global warming has become a serious problem. However, scientific studies have not been sufficiently conducted to understand the mechanisms. Solifluction, a gradual mass movement related to freeze-thaw processes, is known as a typical topographical deformation. The purpose of this study is to simulate the solifluction process considering the seepage influence, and then establish a predictive numerical model. The authors adopted the Finite Volume Method (FVM) and Dupuit's assumption in order to precisely simulate the seepage flow. Consequently, according to this study, the authors suggested to adopt a non-linear assumption for appropriate estimation of seepage flow velocity.

Modern and past periglacial features in Central Asia and their implication for paleoclimate reconstructions

In the continental areas of Central and High Asia, periglacial landform assemblages, sediment structures and processes are mainly influenced and determined by of soil humidity during freeze–thaw cycles. These cryogenic processes result in periglacial landforms such as solifluction, earth hummocks or patterned ground. The distribution of rock glaciers as clear indicators of permafrost is additionally determined by rock fall or moraine debris composed of large boulders (e.g. of granite). Periglacial features were used to reconstruct past climatic conditions, e.g. relict involutions and ice-wedge casts provide evidence for the distribution of former permafrost, say, for the Last Glacial Maximum (LGM). Past temperatures, e.g. mean annual air temperatures, can be estimated from these periglacial features and can be compared with other proxy data, such as glacier fluctuations. Examples from late Holocene solifluction activity in the Altai, Khangai and north-eastern Tibetan Plateau show a different intensity of solifluction processes during the late Holocene and Little Ice Age due to a decrease in temperature and higher soil humidity. The distribution of past permafrost in some regions is still a matter of debate because of different interpretations of sediment structures: sometimes features described as ice-wedge casts may be caused by roots or desiccation cracks due to drying of clay rich sediments. Seismically deformed unconsolidated deposits (seismites) can also be misinterpreted as periglacial involutions. The lack of certain landform assemblages and sediment structures does not necessarily mean that the area had no permafrost. Moisture conditions can also determine the periglacial landform generation to a large degree. They can be ordered in Central Asia as follows (from highest moisture availability to lowest): solifluction; rock glacier; permafrost involutions; ice-wedge casts; sand-wedge casts.