Periglacial Conditions Research Articles

Soil‐vegetation interplay in a Holocene toposequence at Torres del Paine National Park, southern Andes, Chile

AbstractChile's Torres del Paine National Park (TPNP) is one of the most impressive landscapes in southern Patagonia, with unique natural elements on the edge of the southern ice field, where knowledge of soils and ecological relationships is nonexistent. Therefore, the objective of this study was to determine the chemical, physical, mineralogical, and micromorphological characteristics of Holocene soils along a local toposequence representing the main vegetation types of the TPNP. The morphological, chemical, physical, and mineralogical properties of 12 soil profiles were studied and classified according to Soil Taxonomy. Coevolution of vegetation and soil taxa is clearly evident since glaciation, with podsolization under austral Nothofagus pumilio forests leading to the development of spodosols, while paludization in local depressions with Nothofagus forests allowed the formation of histosols. Slopes covered with loess and tephra led to the formation of Andisols with shrub vegetation. Predominant parent materials include till from Late Quaternary advances of southern Andean ice, Pleistocene loess, and volcanic ash from surrounding Chilean volcanoes. The parent materials were strongly influenced by Late Quaternary climatic and landscape changes following the retreat of the Last Glacial Maximum in southern Patagonia, resulting in erosional and depositional conditions (windblown loess, fluvial glacial deposits, and moraines). Stable landforms show the influence of allochthonous volcanic ash shaping Andean features, combined with the accumulation of organic matter in hydromorphic soils. Three main groups of soils have been identified: loess‐rich soils, organic‐rich soils, and poorly developed soils. The latter show low fertility related to recent landforms on different substrates ranging from till, rocky slopes, talus, or glacial deposits. In high mountain regions under periglacial conditions, cryoturbation features indicate seasonal frost–thaw cycles without current permafrost. The diversity of soil orders in the mountains of southern Patagonia is comparable to similar environmental conditions and latitudes in the Northern Hemisphere. However, the andic properties due to volcanic ejecta inputs, as well as organic‐rich soils at low altitudes of bottom valleys, are typical features of the soils at TNTP.

Age, composition and spatial distribution of sandy loess in north‐eastern Germany (Fläming, Brandenburg)

AbstractThe sandy loess deposits in the lowlands of northern Germany present a valuable sedimentary archive for late Weichselian periglacial geomorphodynamics. While other aeolian sediments from the Late Quaternary, especially loess deposits and sand dunes, have been studied and dated in some detail in the last decades, sandy loess has received less scientific attention with respect to its genesis, composition, age and provenance as well as distribution patterns. In this study, we present detailed results for three sediment sections located on the Fläming ridge in the south of the state of Brandenburg. According to our results from luminescence dating, the sandy loess deposits of this area were deposited during the late MIS 2 (19–14 ka) with a highly variable thickness of at least up to 4 m, followed by a deposition of periglacial coversands shortly thereafter. The sandy loess deposits display a homogeneous geochemical composition and grain size characteristics similar to loess sections in the main loess areas to the west and south. Furthermore, we analysed a large dataset of geological drill data and performed a spatial interpolation of sandy loess distribution in the Western Fläming. Despite the strongly dissected modern landscape of the Fläming ridge which is partly the result of intense Holocene soil erosion processes, general patterns of the original loess distribution could be deduced. Based on these findings, we were able to identify the low‐lying areas to the north and north‐east of the study area to be the most likely source areas for the sandy loess as a result of katabatic winds originating from the Fennoscandian Ice Shield. Thereby, this study yields important insights regarding aeolian transport and deposition patterns under periglacial conditions in the Central European Lowlands.

Ventifacts and wind deflation surfaces in context with glaciofluvial sediment successions in southern Sweden – Their age and implication for glacial history

Recent suggestions propose that the glacial landscape in southern Sweden is primarily a relict from the Saalian glaciation (>130 ka). The arguments for this standpoint are the assertion that the majority of glaciofluvial deposits in this region are till-covered, and that wind-abraded clasts are observed at the contact between glaciofluvial sediments and till at numerous locations. Furthermore, it has been posited that this wind abrasion occurred during periglacial conditions during the Early Weichselian, preceding the Last Glacial Maximum (LGM). If this hypothesis holds true, it would necessitate a significant shift in our understanding of the Quaternary geological history for this region. To test this claim, we conducted an extensive examination of the purported stratigraphic conditions within 54 gravel pits situated south of the Middle Swedish End Moraine Zone (MSEMZ). The presence of a covering till bed on top of glaciofluvial sediments could only be confirmed in 22% of the gravel pits, and these sites were almost exclusively associated with ice-margin standstills/oscillations during the Late Weichselian deglaciation. In all other gravel pits where covering till could not be verified, ventifacts occur in several stratigraphic positions: at the contact between glaciofluvial and overlying littoral sediment, redeposited ventifacts within littoral sediment, and ventifacts at the contact between glaciofluvial or littoral sediments and overlying aeolian sediment. We conducted an extensive luminescence dating program (comprising 74 samples) in 22 of the gravel pits to determine the age of the ventification by dating underlying and overlying sediments. We conclude that wind abrasion across southern Sweden was not a single simultaneous event but rather a time-transgressive or recurrent process. It occurred in close conjunction with local deglaciation in some instances, while in others, it transpired later, extending into the Early Holocene. Notably, none of the encountered ventifact surfaces are of a pre-LGM age. For sites along the west coast, the evidence indicates a first wind abrasion event during periglacial conditions roughly between 17 and 16 ka. In upland sites, ventifact formation either occurred immediately after deglaciation, during the Bølling−Allerød interstadial complex (14.7−12.8 ka), or during the Younger Dryas. Even though the ice margin was situated far to the north of these sites during the latter event, concurrent patterned ground formation suggests a harsh climate with reduced vegetation cover, leading to sand drift and ventifact formation in both coastal and upland areas. In some locations, the sand drift and subsequent aeolian sediment deposition persisted into the Early Holocene. Based on our stratigraphic investigations and dates, we reject the idea that southern Sweden's glacial landscape was shaped primarily during the Saalian.

Lake sedimentation conditions in the lower part Seyda River (north of Komi Republic, Russia) according to palynological and diatom data

The aim of the study is to investigate sedimentation processes during the Late Glacial and Holocene in the eastern Bolshezemelskaya Tundra. The coastal outcrop SD-5, 16 m high, in the lower reaches of the Seyda River (Komi Republic) was studied. Analytical methods included palynological and diatom analysis, and 14C dating. When characterizing the stages of sediment formation, algae Pediastrum, Desmidiales, and other non-pollen palynomorphs were also identified. The lithological structure of the outcrop and the results obtained made it possible to trace the transformations of the periglacial paleo-reservoir and the four main stages of sedimentation associated with them. The banded clay at its base was deposited in a periglacial lake under periglacial conditions. The overlying layer of interbedded sands accumulated as a result of the descent of the periglacial paleo-reservoir. The peat exposed in the roof of the section was initially formed (12125±49 – 8719±44 14C BP) in a cold deep-water lake that arose in place of a periglacial reservoir. The vegetation cover consisted of yernik and wormwood-chenopodium thickets. Later (up to ~ 4500 14C BP) the shallows were overgrown with wetland plants. The improvement of the climate contributed to the advance of birch and later (7705±43 14C BP) spruce forests. Then, starting from ~ 4500 14C BP, the swamp massif drained and froze, and modern plant communities developed.

Record of aeolian processes in Pleistocene deposits in the foreland of the European sand belt

Abstract This article presents the degree of aeolization of Pleistocene deposits in the foreground of the European sand belt in southern Poland. Ten of the 13 sites were established in the Oświęcim Basin and three in the south part of the Silesian Upland. Attention was focused on four types of deposits formed during three glaciations (Sanian, Odranian, Vistulian): boulder clay, fluvioglacial sands and gravels, end moraine deposits, and aeolian sands. Quartz grain abrasion (for the 0.8–1.0 mm fraction) was examined by mechanical graniformametry and the morphoscopic method. The record of aeolian processes in analyzed deposits is the presence of quartz grains RM (very well-rounded and mat) and EM/RM (moderately rounded and mat). They were found in deposits of various origins and ages but in variable proportions. Considering only the average percentage of grains RM, it should be regarded that abrasion of deposits is low in the case of fluvioglacial deposits, moderate in the case of glacial deposits, and good in the case of aeolian deposits. However, the key factor in determining the degree of abrasion is the share of EM/RM grains, which in the abovementioned deposits are seven, three, and twice as many as RM grains. Therefore, the most noteworthy research result is the very high total share of grains with aeolian abrasion (RM + EM/RM), amounting on average to 84.1% for Odranian fluvioglacial deposits, 86.7% for Sanian glacial deposits and 92.6% for Late Glacial aeolian deposits. It means that in the study area, glacial and fluvioglacial transport included deposits with good aeolian abrasion obtained in the periglacial environment before the transgression of the ice sheets. Probably due to the longer persistence of periglacial conditions in southern Poland, compared to its central and northern parts, the degree of aeolization of fluvioglacial and glacial deposits is better. At the same time, there is a significant differentiation in the aeolization of fluvioglacial deposits within the outwash plain in the foreland of the maximum extent of the Odranian ice sheet. In its proximal part, near the front of the ice sheet, fluvioglacial deposits are characterized by much worse abrasion of quartz grains than in the distal part.

The summer heatwave in 2022 and its role in changing permafrost and periglacial conditions at a historic mountain pass in the Eastern Alps (Hochtor, Hohe Tauern Range, Austria).

Air temperatures in Europe in 2022 had been the highest on record for the meteorological summer season [June, July and August (JJA)], with +1.3°C above the 1991-2020 average. We studied the effects of recent warming on permafrost and periglacial conditions at a historical mountain pass in the Eastern Alps (Hochtor, 2,576 m asl, 47.08°N, 12.84°E). We used ground temperature data (2010-2022), repeated electrical resistivity tomography measurements (2019, 2022) and auxiliary data dating back to Roman times. We quantified permafrost conditions, evaluated frost-related weathering and slope processes and assessed the impact of atmospheric warming on it. Results show that summer ground surface temperatures increased by 2.5°C between 1891-1920 and 1991-2020, whereas frost-related weathering and periglacial processes decreased. The summers of 2003, 2015, 2019 and 2022 were the four warmest ones in 1887-2022. Hochtor changed in 2010-2022 from an active permafrost site to an inactive one with supra-permafrost talik. A general three-layer structure was quantified for all three ERT profiles measured. The middle, 5-10m thick layer is ice-poor permafrost detected in 2019, whose existence, although smaller, was confirmed in 2022. Resistivity decreased at the three profiles by 3.9% to 5.2% per year, suggesting permafrost degradation. We interpret the resistivity changes between the summers of 2019 and 2022 as a long-term signal of permafrost degradation and not as the single effect of the summer heatwave in 2022. As our data show how rapidly permafrost degrades and as we face an even warmer climate for the remaining part of the 21st century, we expect that near-surface permafrost at the Hochtor site will soon be history.

A multiscalar and multiproxy geoarchaeological approach to site formation processes at the Middle and Upper Palaeolithic site of La Roche-à-Pierrot, Saint-Césaire, France

The site of La Roche-à-Pierrot in Saint-Césaire (Charente-Maritime, France) produced a succession of Mousterian, Châtelperronian and Aurignacian occupations, and continues to play a central role in debates concerning the Middle-to-Upper Palaeolithic transition. The source of controversy surrounding the site relates to ambiguities concerning the overall archaeological sequence, the cultural association of the human remains found at the site and the limited number of robust absolute dates. Here, we present the results of a multiscalar, multiproxy geoarchaeological investigation of the site's sedimentary sequence. Our study integrates geomorphology, field lithostratigraphy, microstratigraphy, geochemistry and absolute dating methods (radiocarbon and optically stimulated luminescence) designed to characterize site formation processes. We propose a site formation model involving the evolution of a karstified limestone cliff from a semi-closed system to an exposed slope deposit, with sediments at the base of the cliff accumulating under periglacial conditions of MIS3, broadly between ca. 59.9 ± 3.9 ka and ca. 37.7 ka. The lowermost Mousterian occupations took place in a semi-closed, sheltered space in which sedimentary rates were low, involving mainly cryoclastic roof spall and episodic percolation of fine-grained sediment. This depositional environment generated a Mousterian archaeological palimpsest in the proximal area and translocated downslope. Subsequent Mousterian, Châtelperronian and Aurignacian remains embedded within diamictons were deposited in an open-air context, on a sloping surface at the apex of a palaeotalus, and possibly above the site, at the top of the cliff. The resulting diachronous surfaces and immature deposits were subject to solifluction and slopewash, with low sedimentary rates. Our geoarchaeological study sheds new light on previously noted spatial inconsistencies in the archaeological sequence and constitutes a rigorous framework for further archaeological research at the site, highlighting the potential of a multiscalar, multiproxy site formation research to improve stratigraphic investigation of Palaeolithic sites in similar geomorphological contexts.

Palaeoenvironmental history of the Middle Pleistocene deposits at Gilson, Warwickshire, England: part of the High Speed Two railway route alignment

ABSTRACTThe investigation of a hillside at Gilson (Lat. 52.510341, Long. ‐1.718313), southwest of Coleshill, Warwickshire (within the High Speed Two railway ‘Delta Junction’ compound), England, has yielded evidence of sedimentation during a temperate stage. The site's stratigraphy starts with the aggregation of cold‐climate sand and gravels deposited during the Anglian Stage within the proto‐Tame and proto‐Blythe palaeovalleys. A warm‐climate period is recorded by the infill of organic material representing the second half of the Hoxnian interglacial Stage. Picea, Abies and Pinus dominate vegetation within a swamp‐like environment, before a Pinus forest develops in the upper part of the organic sequence. The following cold‐climate period saw incision and aggregation of the surrounding region throughout much of the Wolstonian and Devensian Stages, where much of the overlying silt, sand and gravel were reworked under intense periglacial conditions. Presented here is a geophysical examination of the shallow basin by ground‐penetrating radar undertaken to understand the spatial distribution and stratigraphical history of the basin. The deposits at Gilson provide a valuable stratigraphic marker in the glacial sequence of the English West Midlands and are correlated to similar deposits at neighbouring Quinton and Nechells. At these regional sites organic accumulation occurred for most of the temperate stage, infilling lake basins. These sequences indicate an environment dominated by pollen of Abies, Quercus, Ulmus and Corylus woodland vegetation. These assemblages differ markedly from those typically found in the last interglacial and confirm correlation to the Middle Pleistocene Hoxnian interglacial Stage (c. MIS 11c).

Morphology and distribution of biological soil crusts and their potential role in soil-forming processes under dry high-altitude periglacial conditions (Eastern Pamir, Tajikistan)

Under demanding climatic conditions that limit the development of vascular vegetation, biological soil crusts (BSCs) drive the processes of soil formation and nutrient sequestration. Though BSCs were studied in glacier forelands worldwide, the high-altitude areas with a combination of glaciation/deglaciation and arid or hyperarid climate remain almost unstudied in this respect. Therefore, we provided the first data on BSCs from a glacier foreland in the E Pamir. These characteristics can be crucial for assessing BSC's role in soil-forming processes in dry, high-altitude periglacial environments. During our research, we assessed (1) BSCs’ morphology and distribution; (2) microbial biomass and nutrient retention patterns in morphologically differentiated BSC types, (3) C, N and P accumulation in BSCs biomass in comparison to sub-crust soils; (4) sub-crust soils enrichment in C, N and P in comparison to bare soils and soils under vascular plants; (5) potential origin and transformation degree of organic matter accumulated by BSCs. Our study showed that the distribution and development of BSCs were noticeably restricted, probably due to low temperatures, aridity and intense periglacial processes, resulting in continuous soil surface remodeling. Thus, poorly developed BSCs were the dominating biologically active soil cover type and, thus, most likely the main biological soil-forming factor in the foreland. BSCs accumulated C, N and P in their biomass and enriched their sub-crust soils in these nutrients. The average enrichment observed for soils under advanced crusts was similar to those obtained for soils under vascular plants. In all types of the studied samples, including bare soils, n-alkanes of vascular plant origin dominated, indicating mixing and uniform distribution of organic matter. Over the course of aridification projected for the Pamir Mountains, the BSCs could potentially become the most important player in the accumulation of soil nutrients in this area. However, due to the dominance of the simplest BSC type, soil formation in the Uisu Glacier foreland will be relatively slow.

Campanula aibgica (Campanulaceae) – a new species from vicinity of Sochi

The description of Campanula aibgica from basalt rocks of northern slope of Aibga Ridge (Sochi National Park, Krasnodar Territory) is presented. The species belongs to subgenus Campanula, sect. Cordifoliae (Fomin) Charadze. Apparently, it is close to sympatric Colchian taxa C. dzyschrica Kolak., C. kolakovskyi Charadze, C. collina Sims subsp. sphaerocarpa (Kolak.) Ogan., however, it differs exactly from them in morphology and ecology. It differs radically from other species of the section Cordifoliae in habitus and ecology. New species is narrow northern Colchis endemic, which developed under the periglacial conditions of the basalt rocks on northern slope of Aibga Ridge.

Multidisciplinary analysis of pit craters at Hale Crater, Mars

Pit craters are circular to subcircular depressions that lack a rim and ejecta layer and typically have a conical shape. There are several mechanisms that can explain the formation of such depressions and they are associated with collapse due to the removal of subsurface material. Possible origins of pit craters include: volcanic processes (collapse of lava tubes, magmatic chambers, intrusion of dikes), karstic dissolution, extensional faulting or volatile processes.In this work, we study pit craters in the north-estern external slope of Hale Crater. We identified >40 pit craters that present unique morphological features in association with different landforms associated with volatile activity in the area. We identified moraine like ridges, gullies and aprons together with pits that represent an interesting suite of landforms. After producing a detailed geomorphic map, we classified the pits into: i) single pit craters, ii) chain pit craters, iii) complex pit craters and iv) elongated pit craters.We used DTMs to determine orientation and slopes of the pit craters-hosting terrains and to analyze elevation profiles of the different types of pits and their relation with the gullies and other features. In addition, we performed a spectral analysis using CRISM multispectral dataset in order to characterize the mineralogy of the sediments in the region and to identify any distinctive properties that could promote the formation of these depressions.Here, we propose that pit craters are stratigraphically on top of the ice-related landforms and present complex relationships with the gullies. The spatial relationship between the pits and these structures, along with the absence of evidence of present or past volcanic activity and the lack of evidence of any extensional faulting allows us to propose that the origin of the pit craters in the study area might be related to some volatile process. We propose here that these particular pit craters at Hale crater, are morphologically similar to Icelandic depressions located in a glacial environment. We conclude that the landforms found in the area are in close relation with glacial or periglacial conditions and pit craters might be formed by sublimation/melting of ground ice.

Soil Fungal Diversity and Ecology Assessed Using DNA Metabarcoding along a Deglaciated Chronosequence at Clearwater Mesa, James Ross Island, Antarctic Peninsula

We studied the fungal diversity present in soils sampled along a deglaciated chronosequence from para- to periglacial conditions on James Ross Island, north-east Antarctic Peninsula, using DNA metabarcoding. A total of 88 amplicon sequence variants (ASVs) were detected, dominated by the phyla Ascomycota, Basidiomycota and Mortierellomycota. The uncommon phyla Chytridiomycota, Rozellomycota, Monoblepharomycota, Zoopagomycota and Basidiobolomycota were detected. Unknown fungi identified at higher hierarchical taxonomic levels (Fungal sp. 1, Fungal sp. 2, Spizellomycetales sp. and Rozellomycotina sp.) and taxa identified at generic and specific levels (Mortierella sp., Pseudogymnoascus sp., Mortierella alpina, M. turficola, Neoascochyta paspali, Penicillium sp. and Betamyces sp.) dominated the assemblages. In general, the assemblages displayed high diversity and richness, and moderate dominance. Only 12 of the fungal ASVs were detected in all chronosequence soils sampled. Sequences representing saprophytic, pathogenic and symbiotic fungi were detected. Based on the sequence diversity obtained, Clearwater Mesa soils contain a complex fungal community, including the presence of fungal groups generally considered rare in Antarctica, with dominant taxa recognized as cold-adapted cosmopolitan, endemic, saprotrophic and phytopathogenic fungi. Clearwater Mesa ecosystems are impacted by the effects of regional climatic changes, and may provide a natural observatory to understand climate change effects over time.

Depositional conditions of the Upper Younger Loess during the Last Glacial Maximum in central and eastern Europe

This paper is a summary of the results of research on the accumulation conditions of the Upper Younger Loess (LMg) in Poland and Bug loess (bg) in Ukraine from the maximum stage (MIS 2) of the Vistulian (Weichselian) Glaciation in central and eastern Europe. These studies included an analysis of the morphological (topographic) situation of the loess cover, its grain size and heavy mineral composition, the preserved structures of loess sedimentation as well as mollusc and pollen analyses of this loess. They revealed that the accumulation of Upper Younger Loess (UYL) might have been more dependent on the prevailing moisture conditions than previously thought. These conditions could have been caused by cold air masses from an ice sheet and warm air masses from the Mediterranean Sea and Atlantic coming together in the Carpathians and the Holy Cross Mountains and favouring the formation of dust storms and precipitation. In this process, a loading of loess dust (formed from local rocks weathering in periglacial conditions) by atmospheric moisture particles was especially significant. The moist substrate not only favoured the periodic development of vegetation and molluscs but also enabled the interception of dust and the accumulation of an increasingly thick loess cover. Westerly and south-westerly winds predominated in the UYL as indicated by the topographic position of loess patches and the mineral composition of the studied loess. Periodically an increased air circulation from the east and northeast occurred.

Rates and processes controlling periglacial alluvial fan formation: Implications for martian fans

Abstract Alluvial fans are found across a range of climates and are built from a combination of fluvial and debris flow processes. Correct identification of process is critical to reconstructing the climate and water histories of alluvial fans on Earth and Mars. Theory and data from subaerial Earth fans are often used to estimate paleoflow discharges and sediment fluxes for martian fans; however, most terrestrial work has been conducted on fans that are in hot, dry climates with runoff sourced from rainfall. This differs from the prevailing interpretation that martian fans were sourced from snowmelt under warming periglacial conditions. To characterize processes and rates of periglacial fan formation, we conducted a field-based study of the Black Mountain alluvial fan in the Aklavik Range, Canada. We observed active fluvial bedload transport as well as several small debris flows that had initiated from ice-filled gullies. Following a runoff event of ~0.005 mm/hr to ~0.2 mm/hr across the fan, we estimated sediment fluxes of ~0.04 m3/hr. Under bankfull conditions, we estimated runoff rates between ~0.01 mm/hr to ~14 mm/hr and corresponding sediment fluxes of ~0.3 m3/hr to ~550 m3/hr. This suggests that moderate flow events, well below the maximum runoff production rates suggested for Mars, are capable of entraining and transporting appreciable amounts of sediment by fluvial processes. However, sedimentological and geomorphological observations suggest that ~67% of the fan was deposited fluvially; the remainder was deposited by mass flows. Our results emphasize the need to take care in interpreting martian sedimentary processes and climate from fan surface morphology alone.

Viscous creep of ice-rich permafrost debris in a recently uncovered proglacial area in the Tianshan Mountains, China

Since the Little Ice Age and as a consequence of climate warming, many recently deglaciated forefields have become and will continue to evolve into large ice-debris complexes exposed to periglacial processes and environment. Such transitional processes have significant implications for geomorphologic shaping and water supply for the downstream communities, especially in arid regions, but our understanding of their evolutionary processes and their potential geomorphic and hydrological impacts is still limited. A landform transition from partly debris-covered glaciers to ice-rich permafrost debris undergoing slow viscous creep was revealed in the Aerzailaikunai Valley in the eastern Tianshan Mountains in China based on the results of in-situ observations and measurements (boreholes, ground temperature monitoring, electrical resistivity tomography surveys, and continuous global positioning system measurements, among others). The internal structure of ice-till mixture contains pure ice layers, supersaturated frozen sands with ice lenses, and ice-bearing blocks with maximum volumetric contents of heterogeneous ice at 35%–60%. Beneath an 1.5-m-thick active layer, permafrost reached far into the underlying bedrock with the mean annual ground temperature of −2.1 °C at the depth of 20 m. The higher surface velocities (with an accumulative displacement of 65 mm from October 2019 to May 2020) and extremely high electrical resistivity (several million Ω m) of the debris-covered glacier margin were in sharp contrast to those of the progressively stabilizing ground surface (up to 16 mm) and the lower zones with relatively smaller electrical resistivity (several thousand Ω m). Combined with the borehole stratigraphy (higher rock content), monitored ground temperatures (permafrost environment), lower electrical resistance (ice-rich moraine), and continuous global positioning system results (viscous creeping), this study documents a transition from glacial to periglacial conditions, materials and processes characteristic of cold-dry ice-clad mountains, and reinforces the theory of the transition from debris-covered glaciers into morainically originated rock glaciers.

Ground deformation as a result of the foundation of a new module in the Spanish Antarctic Base Gabriel de Castilla, Deception Island, Antarctica

Since its inauguration in the 1989/90 campaign, the Spanish Antarctic Base Gabriel de Castilla (BAEGC) has supported an increasing volume of scientific projects, stimulating the expansion of its facilities. The permafrost soil on which they are located is affected by changing thermal and periglacial conditions that disturb its mechanical and physical characteristics. This paper analyzes the foundation behavior of a building (18.5x6.5x2.7 m length – width – height, around 104 kg in operation supported on 16 posts) through the geomechanical study (stresses and deformations) of the ground during the winter and southern summer seasons, supported by three types of foundations: piles, footings and slabs. These are commonly recommended as support elements inperiglacial soils affected by thermal-seasonal variations. The geotechnical properties have been obtained from stress-tests on soil samples collected in the surroundings of the BAEGC, General Marvá Army Engineers Laboratory (INTA). Considering the thermal variations in the tests on frozen and unfrozen samples, the geotechnical column type has been established and extended along the profile of the 2D domain. The stationary stress-strain equations with a constitutive Mohr-Coulomb rupture model have been solved using finite elements in MIDAS GTS-NX, for each season and each foundation, discretizing with a triangular or quadrangular mesh adapted to the 2D domain geometry with the foundation. The numerical results show that, in any tested case, there is no critical ground failure, and the foundation with the smallest displacement (about 0.036 m), both in summer and winter, is the 1.2 m foundation placed at 0.5 m depth on permafrost.

Contemporary and past aeolian deposition rates in periglacial conditions (Ebba Valley, central Spitsbergen)

Quantitative measurements of aeolian activity at high latitudes are not currently carried out on a large scale, even though these processes are important elements of the geomorphic system of polar regions, which are particularly affected by climate change. This study presents the results of aeolian deposition rates measured and calculated for one of the central Spitsbergen postglacial valleys (Ebba Valley). The results are based on seven summer season field campaigns (2012–2018), as well as on AMS 14C and OSL dating of niveo-aeolian and aeolian sediments. Contemporary mean aeolian deposition rates ranged from 0.1 to 22.9 g·m−2·day−1 over selected parts of the valley and averaged from 2.1 to 12.3 g·m−2·day−1 over the studied summer seasons. Interestingly strong relationships (r2 = 0.71, p = 0.017) between mean air temperature and mean aeolian deposition were observed, possibly indicating the importance of the source material delivered to the valley by fluvioglacial processes. Moreover, aeolian deposition dependence on the source material reflected in the local nature of the process was observed. Niveo-aeolian deposition rates were estimated for the period since the 11th century, through the Little Ice Age, till the second half of the 20th century and revealed a rather constant value of 0.05 cm per year. Since then, the niveo-aeolian deposition rate has significantly increased and equalled 0.3 cm per year, which may be related to rising air temperatures and associated pan-Arctic environmental changes.

Ostatni epizod vistuliańskiego chłodu: cechy diagnostyczne w obszarach ekstraglacjalnych

The general trend of paleogeographic events is dependent on global climate changes. In the analysis of short geological periods, a large role should be assigned to local conditions, understood both in the regional sense and, above all, at the microscale, i.e. the specificity of sites with different morphological location and lithological properties of the substratum, generating a strictly local course of morphogenetic processes reflected in geological records. In this context, a large role should be assigned to the smallest marks of disturbances. Interpretation difficulties that researchers of the Younger Dryas often encounter result from the small thickness of the sub-surface sediment and its weathering changes. The article shows how a detailed analysis of data from the abiotic sphere can be used to reconstruct the conditions prevailing in short geological periods. The area of study is situated in central Poland in an extraglacial zone of the last Quaternary ice sheet that during the Vistulian remained under periglacial conditions (Fig. 1). Among the diagnostic properties are: sedimentological palaeohydrological marks, traces of permafrost re-aggradation, oversnow deposits, aeolian specificity and random events. Changes in the hydrological regimes in rivers are reflected in changes in the sedimentary record showing effective floods (Fig. 2) and together with raising of groundwater table registered in biogenic baśni point two distinct phases of humidity. Traces of permafrost re-aggradation are scarce and found only in particular localities (e.g., under peatlands), but the environmental context of involutions reported from study sites allow us to conclude a return of frozen substratum (Figs 2, 4). The smallscale fissure and fault network in the deposits of the youngest unit of dry periglacial valleys dated to the Younger Dryas were linked to deposition on patches of frozen snow that lasted for several summers and, afterwards, a collapse of he deposit due to melting (Fig. 5). This process did not require the presence of permafrost. In the aeolian environment, the cool conditions of the Younger Dryas resulted locally in the deposition of thin sand covers (Figs 6, 8), which, in favourable topographic conditions, could even form initial dune ramparts (Fig. 7). In the Younger Dryas environment, morphogenetic processes may have been activated by a random event not necessarily associated with global climatic change. One potential example is traces of wildfires registered in a depositional sequence of the Żabieniec site.

Soil pockets phosphatization and chemical weathering of sites affected by flying birds of Maritime Antarctica.

The majority of ornithogenic soils studied in Antarctica focus on the influence of penguins, wherever little reports evaluated the influence of flying birds on soil genesis. This study aimed to characterize the morphologic, chemic, physic, mineralogic, and micromorphologic ornithogenic soil pockets influenced by flying birds in Snow Island, Maritime Antarctica. Fifteen soil pockets were selected, described, sampled and analyzed, these sites constitute the main areas with intense long-term terrestrial biological activity in Snow Island. In order to investigate the impact of phosphatization, we compared the soil pockets with the surrounding soils and soils affected by penguins. Zone of phosphatization have a high concentration of P, K, and Ca. The XRD patterns for the clay fraction of ornithogenic soils show that phosphate minerals are the main crystalline phases (leucophosphite, minyulite, fluorapatite, and apatite). We show that even under typical periglacial conditions, sites influenced by flying birds present active chemical weathering processes. The phosphatization release exchangeable bases and accelerate mineralogical and micromorphological transformations in soils. Under the current global warming trend and expected sea-level rise, the ornithogenic environments are susceptible to accelerated erosion rates and a great part of these hotspots may be lost for the open sea.

Low-altitude periglacial activity in southeastern Australia during the late Pleistocene

AbstractOnly a small area of the Australian mainland was glaciated during the Pleistocene, whereas periglacial deposits are far more common, indicating that cold environments were extensive and a major influence on landscape evolution. Here we identify representative low-elevation examples of scree slopes and frost action, together with fans and valley fills, indicating pronounced erosion cycles during the Pleistocene. To date the deposits, we explore approaches using radiocarbon, optically stimulated luminescence, and profile dating using the cosmogenic nuclide10Be. The radiocarbon and optical ages show that screes, alluvial valley fill, and fans were deposited between 66–13 ka during the coldest part of the last glacial cycle, and within the previous glacial cycle. Exposure dating indicates further landscape erosion cycles back to the mid Pleistocene. Together, the deposits indicate the frost cracking limit was ~1300 m lower at 680 ± 10 m and mean winter temperature was 8.2 ± 0.5°C colder than present. Periglacial conditions probably affected much of southeastern Australia. The treeless and dry conditions resulted in widespread erosion and increased run off. Combined with increased snow storage within catchments, rivers were paradoxically larger, with high seasonal discharge and sediment loads.