Search

The study analyses a 7.5-m-thick sedimentary succession deposited in the largest sandur (the Gwda sandur, a glacial outwash plain) in NW Poland, during the late Weichselian (MIS 2). Although the study site is located in the distal zone of the sandur, its sedimentological features and palaeohydrological parameters reflect the presence of an energetic, powerful environment typical of the proximal zone. Three sedimentary units were recognized in the studied sedimentary succession: (1) lower unit — fine-grained sands with ripple cross-lamination and horizontal lamination; (2) middle unit — gravelly coarse-grained sands and sandy gravels with planar cross-stratification; and, (3) upper unit — sands and gravelly sands with trough cross-stratification. Although the age of deposition of the sandur is accepted to be convergent with that of end-moraines of the same phase, the sediments in the distal zone of the Gwda sandur correlate with an earlier glaciation phase/subphase. Our findings hint at a complex problem: large sandurs such as the Gwda sandur were probably deposited over a long time, and their successions might record the textural and structural features of the proximal subenvironment, even in their distal parts due to deglaciation-related shifting of the proximal zone of a sandur. This paper presents a new approach to analysing the depositional processes in large sandurs, shows a new light on glaciofluvial water supply dynamics of distal parts of sandurs, and may solve several fundamental problems related to the sandur deposition.

International audience; Middle Pleistocene glaciation in the Pyrenees is still poorly documented, but the record of ice fluctuations that occurred before 29 ka within the time span of the Late Pleistocene has benefited from a growing catalogue of geochronological data. Here we provide an exhaustive review of results obtained from different generations of ice-marginal deposits for that period, including 14C ages from glaciolacustrine deposits, 10Be and 36Cl exposure ages from boulders embedded in moraines and/or glacially scoured bedrock steps, and optically stimulated luminescence ages from glaciofluvial outwash terraces. Data currently available indicate that the most extensive Pyrenean glaciation of the Late Pleistocene occurred prior to the Last Glacial Maximum (LGM), but that this outermost stadial position (local LGM) was reached on not just one, but several occasions between MIS (marine isotopic stage) 5b (or MIS 4) and MIS 3. Some preliminary results also document major glacier fluctuations during MIS 3.

Sandy outwash and glacial till soils compose large amounts of public forestland due to historically poor agricultural yields. The outwash soils have low fertility, poor nutrient retention and are restricted from whole-tree harvesting (WTH) in some states, whereas the glacial till has medium nutrient retention and fertility, and is unrestricted from WTH. To assess the long-term sustainability of harvesting, a nutrient budget was constructed from field measurements, the National Cooperative Soil Survey (NCSS) database, and literature values for stem-only harvesting (SOH) and WTH at a 45-year rotation length and 11 rotations were simulated. The budgets showed that SOH and WTH recovery years, or the time necessary for the inputs to match outputs through leaching and one harvest, exceeded common rotation lengths for both soil types under all weathering scenarios, and the average WTH reduced the total available rotations by one harvest. The large variation in soil nutrient pools and harvest removals complicated the ability to identify the difference between SOH and WTH early in the model, but differences became apparent with sequential harvests. The recovery years were 2–20 times the 45-year rotation length under all weathering rates. Taken together, models in this study bridge the gap between short- and long-term studies and bring into question the sustainability of WTH and SOH practices on nutrient-poor soils.

Reconstructing the growth and decay of palaeo-ice sheets is critical to understanding the relationships between global climate and sea-level change and to testing numerical ice sheet models. In this study, we integrate recently acquired high-resolution 2D seismic reflection and borehole datasets from two wind-farm sites offshore of the Netherlands to investigate the sedimentary, geomorphological, and glaciotectonic records left by the Saalian Drenthe substage glaciation, when Scandinavian land ice reached its southernmost extent in the southern North Sea (ca. 160 ka, Marine Isotope Stage 6). A complex assemblage of glaciogenic sediments and glaciotectonic structures is buried in the shallow subsurface. The northern wind-farm site revealed a set of NE–SW-oriented subglacial meltwater channels filled with till and glaciofluvial sediments and an E–W-trending composite ridge with local evidence of intense glaciotectonic deformation that denotes the maximum limit reached by the ice. Based on the identified glacial geomorphology, we refine the mapping of the maximum ice sheet extent offshore, revealing that the ice margin morphology is more complex than previously envisaged and displaying a lobate shape. Ice retreat left an unusual paraglacial landscape characterised by the progressive infilling of topographic depressions carved by ice-driven erosion and a diffuse drainage network of outwash channels. The net direction of outwash was to the west and southwest into a nearby glacial basin. We demonstrate the utility of offshore wind-farm data as records of process–form relationships preserved in buried landscapes, which can be utilised in refining palaeo-ice sheet margins and informing longer-term drivers of change in low-relief settings.

The article contains detailed petrographic studies, which covered a coarse and medium-grain gravel fraction of two layers of glacial till (units ŁS II and ŁS IV) and two layers of sand-gravelly outwash deposits (units ŁS I and ŁS III) related to the Odranian Glaciation (MIS6, Saalian) in Łubienica-Superunki, North Mazovian Lowland, central Poland. Additionally, the indicator erratics were identified to indicate their Scandinavian source areas and the directions of the ice sheet transgressions. This case study is discussed against the background of similar sediments and forms from the same age but from other places in the Polish Lowlands. Regardless of the facies types and fractions, crystalline rocks dominated over all other petrographic groups in all samples. The most common were the indicator erratics derived from the Åland Islands, followed by those from the south-eastern area of Sweden (Småland) and from Dalarna in central Sweden. Amongst the erratics of limited indicative significance, the most common were Lower Palaeozoic limestones and the Jotnian red sandstones. The complex petrographic analyses point to the dipartite nature of the studied profile. This separateness was confirmed by the TBC: 59.1–59.2° N and 18.0–18.2° E for the lower units and 58.8–59.4° N and 17.3–17.9° E for the upper ones.

Diffuse pollution of nitrate from agricultural fields is a critical environmental problem around the world. Sources and sinks of nitrate are heterogeneously distributed over various spatial scales, and the connectivity and transport pathways between them also change at different temporal scales. Therefore, understanding the impact of these variabilities in nitrate transport to the aquatic environment is fundamental for a correct numerical modelling of nitrate transport within a catchment. This study, hence, investigated controls on the spatiotemporal variability of nitrate in a glacial landscape and upscaled it to catchment scale by synthesizing geological, hydrogeochemical, and geophysical information. We found that different parts of the sedimentary succession define the locations of nitrate sinks in this catchment. Denitrification mainly may occur mainly around small patches of postglacial sediments on the outwash plain, which is the youngest formation covering the top layer of the catchment. In contrast, in older geological elements, which constitute the hill and the layers below the outwash plain, oxic, nitrate-containing groundwater was found, probably because of depletion of reduced compounds over the long exposure time. We also found that the boundary between these two formations may govern the seasonal shift of this oxic groundwater's connectivity to the stream consequently nitrate export from the catchment. This conceptual understanding of nitrate transport and sinks then was transformed into a 3D hydrogeochemistry model based on a high-resolution resistivity model of the catchment. We propose that such a basic understanding of how a catchment hydrogeochemically operates should be the first step toward setting up a catchment scale hydrological model with reactive N transport.

The origin of alluvial fans at the drainage basin or the margins of the arid sedimentary basin on the northeastern Tibetan Plateau (NETP) has been a focus of debate among scientific communities. Extensive alluvial fans had developed in the mountain-basin systems of this region during the late Pleistocene. Based on geomorphic/stratigraphic studies and the optically stimulated luminescence (OSL) chronology, we investigated numerous alluvial sequences in the drainage basin of the coupled mountain-basin system on the NETP. Sedimentologic analyses showed that these alluvial sediments mainly comprise crudely meter and decimeter beds of fanglomerate and sandy lenticles, which occasionally contain boulders in the thinner layers. OSL dating results showed that the alluvial sediments were mainly developed during the late MIS 5, MIS 3, and Last Glaciation and Deglaciation (maximum aggradations), while little had occurred during the early Holocene. Comparing our ages and their probability density curves with those of glacial advances from the northeastern/eastern TP, the consistency of both records during different stages since the late Pleistocene suggested that the development of alluvial fans was driven by glacier activities, which yielded abundant outwash, feeding alluvial aggradations. Based on this finding, together with results of previous studies, we argued that the dynamics of alluvial geomorphic processes had a paleoclimatic origin rather than surface uplifts. Further studies indicated that the precipitation of glaciations originated from the ISM northward intrusion during the late MIS 5, MIS 3, and Holocene; however, it was mainly influenced by the westerlies during the Last Glaciation and Deglaciation. Therefore, the development of alluvial fans on the NETP represents coupling signals of the ISM and the westerlies on the interglacial–glacial cycle timescales. The coupling evolution of glacier activities and alluvial aggradations in the drainage basins of mountain-basin systems on the NETP provides a model for assessing the linkages between regional geomorphic processes and atmospheric circulations on hemispheric scales.

Frontiers in Earth Science 9, 600010 (2021). doi:10.3389/feart.2021.600010, Published by Frontiers Media, Lausanne

AMU Morasko soft clay is the normally consolidated, postglacial clayey silty sand to sandy clay, deposited during the last glaciation (Weichselian) within the marginal zone of end moraine of Posnanian Phase. These soils are characterized by low plasticity, high porosity and are fully saturated, therefore, from a geotechnical point of view they can be defined as soft clays. The over 10 meter thick complex of clayey glacial sediments is covered with fine and medium sands with single grains of gravel of the so-called first sandur level from the youngest glaciation. This kind of sediments are very common in the area of north-western Poland and, due to high compressibility, become a problematic subsoil for the shallow foundations. The high porosity and saturation also causes significant problems in obtaining high quality samples for laboratory tests. This means that in situ tests are very often the only possible and economically justifiable test methods. Extended investigations carried out on these clays, which provide reliable correlations between in situ and laboratory test results, will be very useful. For the purpose of this research paper, a wide variety of in situ (CPTU, DMT, FVT) and laboratory (physical properties, direct shear, oedometer) tests have been carried out on the material found at the depth of up to 16 m, in the area of 8 ha, within the campus of Adam Mickiewicz University (AMU) in Poznan, Poland. Preliminary investigations (performed four years ago) showed high uniformity of the test site. The current laboratory tests were carried out on both high quality natural samples and reconstructed samples. The rate effect on the results of some of the tests was also investigated. The obtained results allowed to present a wide geological and engineering characterization of these interesting glacial deposits.

Studies have documented that recent anthropogenic climate change has caused increased vegetative growth on arctic tundra landscapes, resulting in increased carbon storage (in biomass and soil), but decreased albedo and increased energy budgets. The glacial outwash sandplains (sandurs) of Iceland offer an interesting landscape comparison. Here, glacio-fluvial deposits of basaltic volcanic sands and gravels form a low albedo surface (mean 0.11) that stores little carbon (< 0.1%). Conversion of the barren surface to a moss-dominated heath in recent decades increased albedo substantially (mean 0.24), contrary to the general trend on Arctic tundra landscapes, and also increased soil carbon (> 0.2%). The environmental benefits of increased albedo and carbon sequestration highlight the importance of considering the specific processes of landscape change in projecting future environmental changes.

The lower reaches of the River Ure, on the flanks of the Pennine Hills in northern England, contain sedimentary and erosional landforms that are a record of fluvial activity during deglaciation and valley-glacier retreat at the end of the last (Devensian) glacial period, and in the subsequent post-glacial Holocene. Terraces and channels, most of which are now relict features well above the altitude of the present river, attest to the impacts of massive meltwater discharge and deposition of sand and gravel outwash, and dynamic river regimes with rapid incision. Through field survey, we have created a detailed geomorphological map of these landforms and glacial and fluvioglacial surface deposits, as well as the terraces and palaeochannels that were abandoned by the river due to avulsion and incision-driven course changes. We have recorded the nature of the outwash gravels, now effectively terrace features, from exposed sections in working quarries, one of which we discuss here. The palaeochannels have accumulated sediment fills and we have examined several which lie within the range of 100 and 16 m above present sea level. The results of lithostratigraphic, palynological, and radiocarbon analyses at two main and three subsidiary sites indicate that palaeochannel ages range from almost 14,000 to approximately 4000 calibrated years ago in a clear altitudinal sequence. The oldest are probably caused by rapid incision due to deglaciation-driven isostatic uplift. The similarity in date of the three downstream sites suggests that a late Holocene combination of climatic deterioration and increased human activity in the catchment caused instability and entrenchment. Pollen data from the channel fills provide relative dating, and agree well with pollen records from other regional Lateglacial and Holocene sites. Non-pollen palynomorph (NPP) analysis at one of the sites allows reconstruction of the hydrological history of channel infill. This research shows that the application of an integrated suite of research techniques can yield a highly detailed understanding of fluvial evolution and landscape history.

Thick Quaternary sediments of the Breiðavik Group are intercalated between lava flows and tuffs on Tjornes, North Iceland. The present chapter is a compilation of lithostratigraphic and fossil data, combined with an interpretation of the sedimentary and volcanic facies. The vertical column of strata displays a rhythmic character, and a model for sedimentation during glacial-interglacial cycles in a volcanic environment is presented. The Quaternary part of the Tjornes sequence contains evidence of 14 separate glaciations with tillite horizons. The tillites are typically associated with kame and outwash conglomerates, followed at first by glacio-lacustrine and glaciomarine mudrocks and diamictites, and then by deltaic and/or bar-lagoon assemblages, fluvial sediments, and subaerial lava flows. Depositional environments are reconstructed for several steps in the geological history of the Breiðavik Group. The oldest tillite has been dated to c. 2.6 Ma. Several of the tillite beds are succeeded by marine sediments with fossils, especially in the lower part of the sequence. During the first million years of the accumulation, the deposition took place in a transitional environment while the area was subsiding, but the latter part of the geological record reflects terrestrial deposition and increased volcanism in the region.

International audience; Compilation of the offshore and onshore altitudinal limits of the loess deposits of western France and southern England shows that they were deposited by low-level wind fields. These relate to (i) the deflation of silt-rich sediment extracted from the outwash plains of the not far distant British–Irish Ice Sheet and from the palaeo-rivers of the Channel, and (ii) the existence of north and north-western palaeo-winds deduced from particle size analysis and heavy mineral distribution, and suggest (iii) that loess particles were transported by strong katabatic winds blowing from the northern ice-covered regions towards Brittany and Normandy. Comparison between the main orientation of Neanderthal shelters and the direction of the katabatic winds shows that they were perpendicular to each other. The dominant orientation of the shelters was apparently ruled by these winds. A small-scale study concentrating on the penultimate glaciation shows that in contrast to Brittany and Normandy where loess deposits accumulated on north-facing cliffs, in England the same particles were deposited on the leeside of the hills. The existence of deflation zones, violently swept by Marine Isotope Stage 6 katabatic winds south of the British–Irish ice sheet, was probably at the origin of the restricted number of Neanderthals at that time in England.

A set of four outwash terraces in the northern Alpine Foreland motivated Penck and Brückner's classical scheme of four great Alpine ice ages: Günz, Mindel, Riss, and Würm. While it is now established that the Würm corresponds to marine isotope stages (MIS) 5d–2 (∼117–14 ka) and the Riss type locality to MIS 6 (∼191–130 ka), there is no consensus regarding the age of the older glaciations. The two oldest terraces, known as Höhere Deckenschotter (HDS) and Tiefere Deckenschotter (TDS) in Switzerland and neighbouring Germany, contain interbedded tills that directly indicate the first arrival of glaciers into the northern Alpine Foreland. Here, we set out to constrain the timing of the HDS, which signal the first major glaciations in the Alps. To achieve this goal, we devised a new burial-dating model tailored to glaciogenic sediments: P-PINI (Particle Pathway Inversion of Nuclide Inventories). The method applies a source-to-sink framework to a cosmogenic 10Be-26Al inversion model accounting for variable cosmic-ray exposure and non-steady erosion. Taking published 10Be-26Al data from five HDS sites (Feusi, Tromsberg, Siglistorf, Irchel Steig, and Irchel Hütz) and one TDS site (Iberig), we obtain age distributions (±1σ) that are especially well constrained for Feusi (0.93 ± 0.13 Ma), Iberig (0.93 ± 0.17 Ma), and Tromsberg (0.88 ± 0.14 Ma), less well-constrained for Irchel Steig (0.69 ± 0.25 Ma) and Siglistorf (0.94 ± 0.27 Ma), and very poorly constrained for Irchel Hütz (1.39 ± 0.56 Ma). Consistent with the morphostratigraphy, which dictates that the TDS postdates the HDS, we implemented a Bayesian modelling framework, yielding an age of 0.69 ± 0.12 Ma for Iberig (TDS) and a combined age of 0.95 ± 0.07 Ma for the HDS sites. Based on the P-PINI burial ages as well as the combined, Bayesian burial age, we propose an age around 1.0–0.9 Ma for the onset of the large Alpine glaciations that triggered the accumulation of the HDS outwash sediments. This roughly accords with the first long glaciation of the Pleistocene (MIS 24–22), identified as a step-change to colder climate and larger glaciations towards the end of the Middle Pleistocene Transition. While our results challenge previously reported ages of ∼2 Ma or more for the HDS in Switzerland, they corroborate evidence from the southern Alpine retroforeland and provide quantitative support for the early hypothesis by G.J. Kukla, who ascribed the oldest glacial deposits in the northern Alpine Foreland to around MIS 22. Finally, we suggest that the source-to-sink approach of P-PINI offers a viable alternative to the established isochron burial-dating method in cases involving non-steady exposure and erosion.

International audience; InSAR time series of surface deformation from 16 yr of Envisat (2003-2011) and Sentinel-1 (2014-2019) ESA satellite radar measurements have been constructed to characterise spatial and temporal dynamics of ground deformation over an 80,000 km2 area in the permafrost of the northeastern Tibetan Plateau. The regional deformation maps encompass various types of periglacial landforms and show that seasonal thaw effects are controlled by the sediment type and local topography. High seasonal ground movements are concentrated on shallow slopes and poor-drainage areas in unconsolidated, frost-susceptible and fine-grained sediments within glacier outwash plains, braided stream plains, alluvial deposits or floodplains. Fast subsidence due to thaw settlement takes place during June/July while frost heave is intense during December/January when two-sided freezing of pore water under pressure causes prolonged ice segregation near the permafrost table. The analysis reveals pervasive subsidence of the ground of up to ∼2 cm/yr, and increasing by a factor of 2 to 5 from 2003 to today, in high-relief and well-drained areas. The findings suggest that seasonal thaw increasingly affects ice-rich layers at the permafrost table, as well as high-rates of widespread mass movements of non-consolidated sediments, the latter amplified by an increase of effects from frost heave/thaw settlement.

The favorable overall conditions for the utilization of groundwater in fluvioglacial aquifers are impacted by significant heterogeneity in the hydraulic conductivity, which is related to small-scale facies changes. Knowledge of the spatial distribution of hydraulically relevant hydrofacies types (HF-types), derived by sedimentological analysis, helps to determine the hydraulic conductivity distribution and thus contribute to understanding the hydraulic dynamics in fluvioglacial aquifers. In particular, the HF-type “open framework gravel (OW)”, which occurs with the HF-type “bimodal gravel (BM)” in BM/OW couplings, has an intrinsically high hydraulic conductivity and significantly impacts hydrogeological challenges such as planning excavation-pit drainage or the prognosis of plumes. The present study investigates the properties and spatial occurrence of HF-types in fluvioglacial deposits at regional scale to derive spatial distribution trends of HF-types, by analyzing 12 gravel pits in the Munich gravel plain (southern Germany) as analogues for outwash plains. The results are compared to the reevaluation of 542 pumping tests. Analysis of the HF-types and the pumping test data shows similar small-scale heterogeneities of the hydraulic conductivity, superimposing large-scale trends. High-permeability BM/OW couples and their dependence on recognizable discharge types in the sedimentary deposits explain sharp-bounded small-scale heterogeneities in the hydraulic conductivity distribution from 9.1 × 10−3 to 2.2 × 10−4 m/s. It is also shown that high values of hydraulic conductivity can be interpolated on shorter distance compared to lower values. While the results of the HF-analysis can be transferred to other fluvioglacial settings (e.g. braided rivers), regional trends must be examined with respect to the surrounding topography., Bayerisches Staatsministerium für Umwelt und Verbraucherschutz http://dx.doi.org/10.13039/501100010219

Slope deformation in mountainous terrain can be driven by different processes, the nature of which is either gravitational and irreversible or seasonal and reversible, the latter induced by permafrost variations or by hydromechanical or thermomechanical effects. The importance of identifying such deformations is not only related to the hazard they can pose, but also to the understanding of changes that permafrost or local hydrological conditions undergo. Here, we carry out a multi-temporal InSAR analysis over a mountainous area 8000 km2 large, straddling north-western Bhutan and southern Tibet. We propose a methodology to separate locally deforming areas from the effects of long-wavelength signals through the analysis of the spatio-temporal behaviour of 4-years long time series of surface displacements. We present the mapping of hundreds of small-scale features that appear to be actively deforming, as well as several examples of reversible deformation rarely detected at this scale in such a challenging and vast region. The analysis of the multi-annual trend of ground deformation shows a relatively small number of irreversible gravitational movements clearly related to rock slides which attests a low level of recent activity of large rock slope instabilities in the region. In the southernmost, lower elevation parts of the study area, we quantify reversible surface displacements with amplitudes ranging between 5 and 17 mm, and showing maximum displacements towards the satellite in summer months, thus compatible with hydro-mechanical effects related to groundwater table variations. In addition, the ground movement induced by the active layer's response to thawing and freezing over the gentler slopes and high-elevation permafrost regions of Bhutan and southern Tibet is on average around 10 mm, with maxima up to 28 mm. The localised displacements appear to be largely associated to braided stream plains, glacier outwash plains or low angle, fine sediment covered slopes.

This work was supported by Natural Environment Research Council consortium grant: BRITICE-CHRONO NE/J009768/1. This paper provides a new deglacial chronology for retreat of the Irish Ice Sheet from the continental shelf of western Ireland to the adjoining coastline, a region where the timing and drivers of ice recession have never been fully constrained. Previous work suggests maximum ice‐sheet extent on the outer western continental shelf occurred at ~26–24 cal. ka BP with the initial retreat of the ice marked by the production of grounding‐zone wedges between 23–21.1 cal. ka BP . However, the timing and rate of ice‐sheet retreat from the inner continental shelf to the present coast are largely unknown. This paper reports 31 new terrestrial cosmogenic nuclide (TCN ) ages from erratics and ice‐moulded bedrock and three new optically stimulated luminescence (OSL ) ages on deglacial outwash. The TCN data constrain deglaciation of the near coast (Aran Islands) to ~19.5–18.5 ka. This infers ice retreated rapidly from the mid‐shelf after 21 ka, but the combined effects of bathymetric shallowing and pinning acted to stabilize the ice at the Aran Islands. However, marginal stability was short‐lived, with multiple coastal sites along the Connemara/Galway coasts demonstrating ice recession under terrestrial conditions by 18.2–17. ka. This pattern of retreat continued as ice retreated eastward through inner Galway Bay by 16.5 ka. South of Galway, the Kilkee–Kilrush Moraine Complex and Scattery Island moraines point to late stage re‐advances of the ice sheet into southern County Clare ~14.1–13.3 ka, but the large errors associated with the OSL ages make correlation with other regional re‐advances difficult. It seems more likely that these moraines are the product of regional ice lobes adjusting to internal ice‐sheet dynamics during deglaciation in the time window 17–16 ka. Publisher PDF

This paper presents macro and microsedimentological data recording subglacial deformation of a sediment succession at Przeszkoda in north-central Poland under the Vistula Ice Stream at the southern fringe of the Scandinavian Ice Sheet during the Weichselian glaciation. The sediment succession consists of (i) undeformed outwash sand, (ii) deformed outwash sand, (iii) bedded till, and (iv) massive till. These deposits were examined in a closely sampled vertical profile for kinematic structures, macrofabrics, grain shape characteristics, and micromorphology (detrital components, microstructures, clast microfabrics). The analyzed parameters suggest that the deposits were generated by a progressive homogenization and mixing of local material with far-travelled detritus successively released from the active ice sole. Grain crushing and abrasion characteristics lack any obvious trends in the vertical profile, indicating that the deformation was focused in a thin (cm-scale) layer which progressively migrated upwards parallel with sediment accretion. The closely spaced thin sections were collected in the deformed outwash sand, bedded till and massive till units. These revealed formation and evolution of stress-induced foliation in the glacier bed whereby three microfabric generations including S1 (earliest), S2 and S3 (latest) foliation were recognized. The geometry of these microfabrics is consistent with their formation in response to the development of subhorizontal Y-type shears, and up-ice dipping P-type and down-ice dipping R-type Riedel shears within the subglacial shear zone. The geometry and cross-cutting relationships between the microfabrics throughout the succession reflects changing deformation styles within a thin deforming bed that migrated time-transgressively up the profile during till accretion. Strain magnitude accumulated in the whole sediment succession was low, in the range of 101 to 102, suggesting that enhanced basal sliding was an important component contributing to fast flow of the ice stream.

The article presents geomorphological analysis results for two outwash fans (sandurs), Elveflya and Nottingham, in the marginal zone of the Werenskiold Glacier in the south-west part of the Spitsbergen. The main goal of this study was to reconstruct the morphological evolution of these landforms and to identify the permafrost zone under their surface. For this purpose, age data of fossils were compiled and compared with newly exposed and dated fossil tundra in the layer glaciotectonically deformed by the forming glacier end moraine. Using this method, a time frame was identified for the glacier advance and for the simultaneous formation of the outwash plains. It was concluded that the Elveflya surface has been built-up with deposits since the Little Ice Age. Sediment deposition ended in the late 1960s, due to hydrographic changes and the redirection of all proglacial waters towards the Nottingham bay. A photointerpretation analysis based on two orthophotomaps and LANDSAT scenes allowed the identification of five microfans in Elveflya, of which two youngest fans have a twice shorter range than the other three. The sixth microfan is currently shaped by deposits washed from the slope of the end moraine. An additional focus was placed on a currently active sandur, which fills the Nottingham bay, in order to identify its growth rate. The average growth rate of this surface increased from 5700 m2&middot, year-1 over the period of 1985&ndash, 2000 to 24,900 m2&middot, year-1 over the period of 2010&ndash, 2017. Electromagnetic measurements carried out on the surfaces of the sandurs demonstrated that the electrical resistivity of the ground is high in the apex of the Elveflya fan (&rho, &ge, 1 k&Omega, m) and low in its toe (typically &rho, &lt, 200 &Omega, m), as in the case of the Nottingham fan ground. In the interpretation advanced here, permafrost developed in the proximal part of the Elveflya sandur, which continues to be supplied by fresh groundwaters flowing from the glacier direction. Low electrical resistivity of the ground in the distal part of the outwash fan suggests the absence of ground ice in this zone, which is subjected to the intrusion of salty and comparatively warm seawater, reaching approximately 1 km inland under the surface of the low-elevated marine terrace. The identified zones additionally display different tendencies for vertical movements of the terrain surface, as identified with the Small Baseline Subset (SBAS) method. The proximal part of the Elveflya outwash fan is relatively stable, while its distal part lowers in the summer period by a maximum of 5 cm. The resulting morphological changes include linear cracks having lengths up to 580 m and an arc line consistent with the coastline.

High-magnitude jokulhlaups, glacier margin position and ice-thickness have been identified as key controls on sandur evolution. Existing models however have focused primarily on observations made during short windows of time and often do not account for the subsequent modification of proglacial landsystems by repeated jokulhlaups or post-depositional modification due to melt out over decadal time-scales. Digital Elevation Models (DEMs) were used to reconstruct the development of large depressions on Skeiðararsandur, an outwash plain in southeast Iceland. These depressions measure up to 1 km in width and up to 13 m in depth and are associated with ice bodies up to 1 km in length and up to 150 m in height emplaced during a high-magnitude jokulhlaup in 1903 and subsequently buried by jokulhlaups in 1913 and 1922. The continued melting of the Harðaskriða ice bodies over a century following their emplacement, together with subsequent repeated burial, by high-magnitude jokulhlaups demonstrates that jokulhlaups may continue to serve as important controls on sandur evolution on a decadal to centennial timescale (101–102 years). The Harðaskriða depressions developed only following the retreat of the glacier margin after 1945, which highlights the controls of margin position on the evolution of the sandur. Margin position and thickness of the glacier profile was seen to affect not only the distribution and thickness of sediment emplaced during jokulhaups but also the rate and pattern of melt in the decades following the decoupling of the margin from the sandur. The jokulhlaup landsystem model signatures identified at this site may provide a useful analogue for interpreting landforms and strata emplaced by glacier margin fluctuations, jokulhlaups and melt out generated by retreating continental Pleistocene ice sheets.

This study analyses the temperature distribution underneath the Piedmont Po Plain (NW Italy), where an important shallow aquifer exists due to fluvial and outwash deposits. A total of 118 thermal logs, for a total of 513 temperature measurements in spring 2008 and 585 in autumn 2008, were used to propose the conceptual thermal model of the vertical temperature distribution in the shallow aquifer of the western Po Plain. A constant temperature depth between 30 and 50 m below ground level was observed, under which aquifer temperatures were constant in the range 13−15 °C during the year independent of the external climatic condition. Above the constant temperature depth, the variable temperature zone, where the temperature is strongly influenced by external seasonal variations, was observed. Moreover, the collected thermometric data were processed, and the solution to the heat diffusion equation underground allowed us to determine the average distribution of temperature at different depths over time. This study provides a more detailed conceptual model of the temperature distribution in the Piedmont Po Plain. The model can be applied to other areas with similar hydrogeological characteristics (e.g., the eastern Po Plain or large plain alluvial aquifers). The paper also furnishes a description of the physical processes of heat diffusion in the shallow aquifer, as supported by statistical analysis. The proposed methodology may be adopted as a simple statistical method for the assessment of temperature values for the low-enthalpy geothermal exploitation of groundwater resources.

The outwash rivers of the Venetian-Friulian plain promoted a high-rate aggradation during the Last Glacial Maximum (LGM), with large sedimentary bodies fed by major glaciers along the south-eastern side of the Alps. Glaciers were temperate-type, hold up by high precipitation rates and characterized by large amount of water trapped in subglacial lakes or funneled in speedy streams. The stratigraphic analysis of these sedimentary bodies showed sharp changes from coarse gravels to well-sorted sandy gravels few kilometers downstream. Large boulders, 1–2 m in size, are present in many sites, especially in the Tagliamento outwash plain, from the end-moraine system to about 13 km far to the south. Most of the boulders are located on the eastern area of the sandur and lie stratigraphically above a paleosol, radiocarbon dated to 31,114 ± 643 cal a BP, thus belonging to the LGM sandur of the Tagliamento glacier. In some locations these boulders are associated to large bars, showing a rough cross-bedding. Similar sedimentary structures are observed 2 km downstream of the LGM frontal moraines in the Astico outwash system, a 25-km-long transfluence tongue of the Adige-Brenta glacial complex. In this case the occurrence gravel dunes containing many boulders marks the evidence of a high-energy deposition. The occurrence of cross-bedded bars, embedding large boulders up to 2 m of diameter, in the piedmont plain of the south-eastern Alps is peculiar. Breaks of natural dams, such as the frontal moraines or the glacier itself, may have triggered glacial lake outburst floods (GLOFs) that determined the formation of such gravel bars with meter-size clasts.

An intensified debate centers on the use of strontium isotopes in surface water run-off as archive for bioavailable signatures in prehistoric provenance studies. Its use has been challenged by a recent suggestion that modern agricultural liming of farmlands exerts a serious imprint on the strontium isotope compositions of these waters. We here present results from a soil profile beneath agricultural farmland in the glaciogenic outwash plain of central West Jutland, Denmark, which show that strontium and its isotope composition derived from lime products is efficiently retained near the surface. Pore waters and bioavailable strontium from the acidic zone below the surface soil depict strontium isotope signatures that can best be explained by a mixture of silicate-derived and relic natural (not agriculturally added) carbonate-derived strontium. We therefore argue that agricultural liming does not contaminate groundwaters and groundwater-supported surface waters, rendering reference maps based on them relevant for modern and past provenance studies.

During the Last Glacial Maximum (LGM), most of the major glaciated basins of the European Southern Alps had piedmont lobes with large outwash plains; only a few glaciers remained within the valley. Piedmont glaciers have left well-preserved terminal moraines, which allow for investigations to be carried out and inferences to be made regarding their evolution and chronology. Valley glaciers' remnants, on the contrary, are often scantly preserved, and changes can only be detected through correlations with glaciofluvial deposits in downstream alluvial basins. The Brenta glacial system's dynamics in the glacier's terminal tract have been inferred through a wide range of sediment analysis techniques on an alluvial stratigraphic record of the Brenta megafan (northeast Italy), and via the mapping of in-valley glacial/glaciofluvial remnants. Glaciers flowing across narrow gorges could possibly be slowed/blocked by such morphology, and glacial/sediment fluxes may then be diverted to lateral valleys. Moreover, narrow valleys may induce glaciers to bulge and form icefalls at their front, preventing the formation of terminal moraines. The Brenta Glacier was probably slowed/blocked by the narrow Valsugana Gorge downstream of Primolano and was effectively diverted eastwards across a wind gap (Canal La Menor Valley), joining the Cismon/Piave glaciers near Rocca and ending ∼ 2 km downstream. The Cismon and Piave catchments started to contribute to the Brenta system just after 27 ka cal BP until at least ∼ 19.5 ka cal BP. After the glaciers collapsed, the Piave River once again flowed into its main valley, whilst the Cismon continued to merge with the Brenta.This investigation shows that glacial catchments may vary significantly over time during a single glaciation in rugged Alpine terrains. Sand petrography and the chemical/mineralogical composition of sediments are powerful proxies for tracing such variations, as they propagate through the glacial and glaciofluvial systems and can be recognized in the alluvial stratigraphic record far downstream from the glacier front.

We present a multi-proxy study of environmental conditions during and after the recessional phases of pro-glacial Lake Algonquin in the vicinity of the North Bay outlet, Great Lakes Basin. Data presented comes from a new sedimentary profile obtained from the Balsam Creek kettle lake c. 34 km north-east of the city of North Bay. This site lies close to the north-east margin of the maximum extent of the post-Algonquin lake sequence, which drained through the Ottawa-Mattawa valley system. Our data are presented against a Bayesian age-depth model, supporting and extending regional understanding of vegetation succession in this part of north-east Ontario. The core profile provides a minimum age for the formation of the glacial outwash delta in which the kettle is set, as well as tentative timing for the Payette (post-Algonquin) lake phase. We highlight two discrete intervals during the Early Holocene, with modelled mean ages of: 8475–8040 cal. BP (332–316 cm) and 7645 cal. BP (286 cm), when climatic aridity affected the growth of vegetation within the kettle vicinity. Association with volcanic activity is posited. Cryptotephra dating to 7660–7430 cal. BP (mean age: 7580 cal. BP) is chronologically and geochemically assigned to the Mazama climactic eruption, while an earlier ash accumulation 8710–7865 cal. BP is tentatively sourced to an unknown eruption also in the Cascades region of Oregon. Outside of these periods, the Balsam Creek sequence shows considerable habitat stability and a character akin to that seen at more southerly latitudes. On this evidence we propose that access to reliable resources within kettle features could have aided the initial colonisation of northern Ontario’s environmentally dynamic early post-glacial landscape.

This paper presents a glacial geomorphological map of landforms produced by the Lago General Carrera–Buenos Aires and Lago Cochrane–Pueyrredón ice lobes of the former Patagonian Ice Sheet. Over 35,000 landforms were digitized into a Geographical Information System from high-resolution (

Summary A new dataset of benthic foraminiferal assemblages from Adventfjorden (tributary fjord of Isfjorden, West Spitsbergen) was compared with the results of a study conducted by Zajączkowski et al. (2010) in Hornsund (West Spitsbergen). According to Nilsen et al. (2016) , Atlantic water inflow to the Isfjorden Trough occurs more readily than to anywhere else along the shelf of Spitsbergen; thus, we compared the foraminiferal assemblages of the outwash Adventfjorden fjord, located in the Isfjorden system, with glacial Hornsund, located in southwest Spitsbergen. Despite the juxtaposition of Adventfjorden and Hornsund the data revealed varying impacts of shelf-transformed water (STW) on the benthic foraminiferal assemblages. Outer and central Adventfjorden was dominated by Adercotryma glomerata, Recurvoides turbinata and Spiroplectammina sp., reflecting the presence of STW, while abundant Melonis barleeanus in the central area of the fjord indicated a large flux of unaltered organic matter. Only the head of the fjord was dominated by the glaciomarine taxa Cassidulina reniforme and Elphidium clavatum. Foraminiferal fauna characteristic of STW-influenced environments (i.e., Nonionellina labradorica and R. turbinata) were also observed in outer Hornsund. However, the glacier-proximal taxa E. clavatum and C. reniforme were dominant throughout the fjord, demonstrating the impacts of meltwater and high sedimentation. Therefore, it is likely that in Hornsund, glacial impact is a major environmental factor, which is stronger than the influence of STW.

The sensitivity of synthetic aperture radar (SAR) coherence has been applied in delineating the boundaries of alpine glaciers because it is nearly unaffected by cloud coverage and can collect data day and night. However, very limited work with application of SAR data has been performed for the alpine glaciers in the Qinghai-Tibetan Plateau (QTP) of China. In this study, we attempted to investigate the change of coherence level in alpine glacier zone and access the glacier boundaries in the QTP using time series of Sentinel-1A SAR images. The DaDongkemadi Glacier (DDG) in the central QTP was selected as the study area with land cover mainly classified into wet snow, ice, river outwash and soil land. We utilized 45 Sentinel-1A C-band SAR images collected during October of 2014 through January of 2018 over the DDG to generate time series of interferometric coherence maps, and to further extract the DDG boundaries. Based on the spatiotemporal analysis of coherence values in the selected sampling areas, we first determined the threshold as 0.7 for distinguishing among different ground targets and then extracted the DDG boundaries through threshold-based segmentation and edge detection. The validation was performed by comparing the DDG boundaries extracted from the coherence maps with those extracted from the Sentinel-2B optical image. The testing results show that the wet snow and ice present a relatively low level of coherence (about 0.5), while the river outwash and the soil land present a higher level of coherence (0.8–1.0). It was found that the coherence maps spanning between June and September (i.e., the glacier ablation period) are the most suitable for identifying the snow- and ice-covered areas. When compared with the boundary detected using optical image, the mean value of Jaccard similarity coefficient for the total areas within the DDG boundaries derived from the coherence maps selected around July, August and September reached up to 0.9010. In contrast, the mean value from the coherence maps selected around December was relatively lower (0.8862). However, the coherence maps around December were the most suitable for distinguishing the ice from the river outwash around the DDG terminus, as the river outwash areas could hardly be differentiated from the ice-covered areas from June through September. The correlation analysis performed by using the meteorological data (i.e., air temperature and precipitation records) suggests that the air temperature and precipitation have a more significant influence on the coherence level of the ice and river outwash than the wet snow and soil land. The proposed method, applied efficiently in this study, shows the potential of multi-temporal coherence estimation from the Sentinel-1A mission to access the boundaries of alpine glaciers on a larger scale in the QTP.

International audience; Studies of the submerged Pleistocene conglomerate cored and dredged in the English Channel show that it resulted from the cementation of stony beaches under a loess blanket. Although the loess cover was later washed out by younger transgressions, the northern limit of the conglomerate corresponds to the original offshore extension of the loess deposits. Compilation of offshore and onshore altitudes of the limits of these deposits shows that loess was deposited by low-level wind fields never thicker than 200 m. Mapping surveys show that the present limits of loess are probably close to their original boundaries. The past proximity of the British Ice Sheet, the accumulation of dusty sediments coating north-facing cliffs of Brittany originating in the outwash of the British–Irish Ice Sheet and in the palaeo-rivers of the English Channel, as well as the southeastward orientation of the palaeo-winds deduced from particle size analysis and heavy minerals distribution, suggest that large volumes of loess were transported by strong katabatic winds blowing from the northern ice-covered regions towards Brittany and Normandy. The existence of katabatic winds is also consistent with the drift of ice rafts that transported Icelandic basalts now grounded in Brittany and possibly with the orientation of Homo neandertalensis shelters.

Brook trout (Salvelinus fontinalis) spawn in fall and overwintering egg development can benefit from stable, relatively warm temperatures in groundwater-seepage zones. However, eggs are also sensitive to dissolved oxygen concentration, which may be reduced in discharging groundwater (i.e., seepage). We investigated a 2 km reach of the coastal Quashnet River in Cape Cod, Massachusetts, USA, to relate preferred fish spawning habitats to geology, geomorphology, and discharging groundwater geochemistry. Thermal reconnaissance methods were used to locate zones of rapid groundwater discharge, which were predominantly found along the central channel of a wider stream valley section. Pore-water chemistry and temporal vertical groundwater flux were measured at a subset of these zones during field campaigns over several seasons. Seepage zones in open-valley sub-reaches generally showed suboxic conditions and higher dissolved solutes compared to the underlying glacial outwash aquifer. These discharge zones were cross-referenced with preferred brook trout redds and evaluated during 10 years of observation, all of which were associated with discrete alcove features in steep cutbanks, where stream meander bends intersect the glacial valley walls. Seepage in these repeat spawning zones was generally stronger and more variable than in open-valley sites, with higher dissolved oxygen and reduced solute concentrations. The combined evidence indicates that regional groundwater discharge along the broader valley bottom is predominantly suboxic due to the influence of near-stream organic deposits; trout show no obvious preference for these zones when spawning. However, the meander bends that cut into sandy deposits near the valley walls generate strong oxic seepage zones that are utilized routinely for redd construction and the overwintering of trout eggs. Stable water isotopic data support the conclusion that repeat spawning zones are located directly on preferential discharges of more localized groundwater. In similar coastal systems with extensive valley peat deposits, the specific use of groundwater-discharge points by brook trout may be limited to morphologies such as cutbanks, where groundwater flow paths do not encounter substantial buried organic material and remain oxygen-rich.

A vortex-based approach is employed to predict the downwash and outwash of a tandem rotor in ground effect and provide an understanding of its wake. The aerodynamic loads of the blades are represented through a panel method, and the behavior of the wake is captured by a viscous vortex particle method. The viscous effects of the ground are accounted for by a viscous boundary model satisfying the no-slip and nonpenetration boundary conditions. The method is first validated for an isolated full-scale Lynx tail rotor and a 172-mm-diameter-scale rotor in ground effect. The results show that the predicted trajectories of the tip vortices and the radial velocity profiles compare favorably with experiments and published computational fluid dynamics results. The results for model CH-47D are then compared with experiments for the downwash and outwash of the tandem rotor. As opposed to the isolated single rotor, a radial outward expansion in the overlapping area is observed, and the peak and the corresponding vertical distance of the velocity maximum of the radial outwash flow for the tandem rotor are larger. Moreover, the rotational direction of the tandem rotor leads to a wake with several vortical interactions resulting in different outwashes on the port and starboard sides.

Aerosols and clouds play important roles in the Arctic climate. Conversely, aerosol emissions and cloud formation are affected by changes in the Arctic climate. This paper reviews studies of aerosols and clouds performed during the Arctic Challenge for Sustainability (ArCS) project carried out by the National Institute of Polar Research (NIPR) in Japan and collaborating institutions. The ArCS project included intensive studies of black carbon aerosols (BC). We installed Continuous Soot Monitoring System (COSMOS) instruments to measure atmospheric BC at four locations in the Arctic, establishing the Arctic BC COSMOS Measurement Network (ABCM-net). We also measured BC concentrations in snowpack in extensive areas of the Arctic and showed that previous studies have greatly overestimated BC in snowpack. We developed and improved new aerosol models that achieved better agreements with measurements of BC in the Arctic atmosphere, snowpack, and falling snow. We made new estimates of radiative forcing of BC in the Arctic atmosphere and snow/ice surfaces that lower their albedo. In addition to these researches on BC, we made accurate measurements of ice nucleating particles (INPs) at Ny-Alesund, Svalbard, showing that their concentrations increased in summer as a result of dust particle emissions from glacial outwash sediments. This high ice nucleating ability was likely due to the presence of organic substances mixed with the dust particles. We also made continuous cloud radar measurements and the first continuous in-situ measurements of cloud microphysical properties in the Arctic at Ny-Alesund. Results from these cloud measurements and their relationship with aerosols are described.

The Rospuda subglacial channel hosts not only deep ribbon lakes and the Rospuda River itself, but also an outwash plain. The paper deals with a lithofacies analysis of deposits from exposures within the Rospuda outwash plain. With the support of geomorphological and geological analyses, it has been found that the outwash plain formed along the Rospuda subglacial channel that was being exposed from under the ice cover. The lithological record of the Rospuda outwash plain shows a distinct division into a proximal and a distal zone. The deposits under study reveal a record of a break in basial sedimentation, when ice-wedge casts developed under conditions of periglacial climate. The development of the Rospuda outwash plain is linked with the ice-marginal zone of the Pomeranian phase, similarly to the Olecko-Rajgród outwash plain that is located to the west.

Im Tiefland Nordwestdeutschlands sind von der saalezeitlichen Vereisung aufgebauten glazifluvialen Geestplatten und Stauchmoränen von flachen Niederungen umgeben. Im Untersuchungsgebiet im Hümmling besteht die Geestplatte aus hauptsächlich sandigen Schmelzwasserablagerungen die von Grundmoräne oder Blockbestreuung überdeckt sind. Diese Sanderfläche ist vom Haupt-Drenthe-Vorstoß abgelagert und danach beim weiteren Vorrücken des Eises überfahren worden. Die Schmelzwassersande bilden nach oben gröber werdende Sequenzen, die im Untersuchungsgebiet in drei Gruben aufgeschlossen sind. Vom Liegenden zum Hangenden sind in den Aufschlüssen drei vom Wasser abgelagerte Fazies erkennbar: eine untere glazilimnische Fazies, eine Übergangsfazies und eine obere glazifluviale Fazies. Sofern sich keine erosiven Zwischenfälle ergeben haben, ist die aufwärtsgerichtete Veränderung von einer Fazies zur anderen ausgesprochen allmählich. Dieser Artikel bringt Argumente dafür, daß die untere Fazies abgelagert worden sei in einer abflußlosen Senke,die sich im fernen Vorland des Inlandeises befand. Durch diesen Vorgang wurde das Gelände eingeebnet und vorbereitet auf eine allmähliche Änderung von glazilimnischen nach glazifluvialen Ablagerungsverhältnissen., research

Anhand von zwei Dünenprofilen wird die Art, Dauer und Intensität von spätglazialen und holozänen Flugsand- und Bodenbildungen innerhalb des Pommerschen Sandergebietes dargestellt. Hierfür wurde ein interdisziplinärer Ansatz aus Sedimentologie, Pedologie, Palynologie und Geochronologie verwendet. Während des Spätglazials kommen auf den Sanderhochflächen flache Flugsanddecken zur Ablagerung, unterbrochen durch die Bildung des Finowbodens. Durch die Ausbreitung einer geschlossenen Vegetationsdecke im Frühholozän, erfolgt eine Stabilisierung der Reliefoberfläche mit anschließender Bodenbildung. Nach intensiven mittelalterlichen Rodungen werden die Oberflächen erneut destabilisiert. Es kommt zur partiellen Aufarbeitung der Flugsande resultierend in Dünenbildungen und einem kuppigen Relief. Eine der untersuchten Dünen wurde dabei komplett im späten Subatlantikum gebildet. Diese Studie unterstreicht die zeitlich-räumliche Variabilität äolischer Aktivität, wobei Umlagerungen entsprechender Korngrößen während verschiedener Phasen nach der Deglaziation ermöglicht wurden., research

The aim of this paper is to quantify and map the impact of the post‐Little Ice Age climate change on the coastal evolution on three glacier catchments in the Kongsfjorden area in Svalbard. Climatic data at Ny‐Alesund indicate an increase in the annual mean air temperature of +4 °C from 1969 to 2016 and an increase in precipitation. On the northern coast of the Brogger Peninsula, the Austre Lovenbreen, Midtre Lovenbreen, and Vestre Lovenbreen glaciers have experienced a net retreat in response to changing meteorological conditions. Because of this retreat, the glaciers have disclosed a large area of 7 km2 composed of terrigenous sediments. These sediments are transported by runoff and created coastal sandur deltas. Channel network behavior has been studied using the computation of the active floodplain width by photointerpretation, which decreased in average from 1966 to 2010. This demonstrated a contraction of the active braided belt and a decrease in the number of braided channels. A photointerpretation analysis combined with acquisition of dGPS data during field work shows a mean shoreline progradation of +0.16 m a−1 from 1966 to 2016, with a maximal advance of +82 m seaward. Since 1966, coastal progradation has decreased in time with higher mean values at the beginning of the studied period and an erosional trend from 1990. The sublittoral area was studied using analog side scan sonar in 2009, 2011, 2012, and 2017. Three prodeltas were identified and underwent a huge extension from 2009 to 2017. In the light of this knowledge, our main conclusion is that, by retreating, glaciers have an impact on the sediment availability and on the capacity of the fluvial system to effectively transport sediment to the shoreline. These two factors control the overall coastal evolution by regulating the sediment supply to the coastal area. The coastal zones that were fed with sediments by runoff have experienced a coastal progradation, and those that lost this supply have undergone a coastal recession. Due to the contraction of proglacial floodplains, current progradation concerns restricted coastal areas.

Red wood ant nest mounds were investigated on terrain deglaciated since the mid-18th century at three outlet glaciers of the Jostedalsbreen ice cap in southern Norway. Chronosequence methodology was combined with a geo-ecological approach in the context of autecology. Size and composition of 168 mounds, most of which belonged to Formica lugubris, were related to terrain age, vegetation characteristics and physical habitat types using non-metric multidimensional scaling (NMDS) linked to segmented bubble plots and inferential statistical techniques. Substantive insights include (1) colonisation occurs 50–80 years after deglaciation; (2) mounds up to 100 cm high occupy the glacier forelands with a density of 2.5–4.6 mounds/hectare; (3) the positive correlation between mound size and terrain age is weakened by the presence of numerous small mounds attributed to the expansion of polydomous colonies by budding; (4) although mounds are mostly composed of plant remains (litter), they contain up to 17% mineral material (mostly gravel) on relatively young terrain; (5) mound size and composition are related to the number of trees ( Betula pubescens) occurring within 5 m of each mound, which reflects the availability of biological resources for mound thatch and ant food, the latter being primarily honeydew from aphids; (6) where aphids are present on trees, the mounds tend to be relatively large, reflecting the presence of ant–aphid mutualism; (7) mounds are larger on moraines and till plains than on outwash deposits, probably reflecting the enhancement of tree growth because of greater moisture availability and soil fertility in the former habitat types; (8) a strong southerly preferred aspect in mound orientation indicates the importance of direct solar radiation in maintaining internal mound temperatures and (9) glacier-foreland landscapes are not simply time-dependent chronosequences reflecting succession but the product of spatio-temporal dynamics involving biotic and abiotic interactions, which we summarise in a conceptual geo-ecological model. The main methodological implications are that chronosequences can be used to investigate the autecology of keystone species using a geo-ecological approach and multivariate analysis.

Estimation of groundwater recharge is one of the most challenging subjects in hydrogeology. It is a critical factor influencing the pollution migration, assessment of aquifer vulnerability to contamination, small-scale groundwater budget calculation, modeling of nutrient cycling and detailed flow path calculations. In Poland an infiltration rate method is widely used, which depends on a system of rate coefficients referring to the type of soil in the vadose zone and shows which part of the precipitation actually reaches the water table. The paper presents results of numerical simulations of vertical flow in unsaturated zone of an experimental site located on Brda outwash plain. Two simulations for varying vegetative cover (pine forest and grass) were performed. The results were compared with five infiltration rates classifications.

Understanding the style and pattern of retreat of the offshore sectors of the last British-Irish Ice Sheet (BIIS) is critical to any attempt to reconstruct its history following the Last Glacial Maximum (LGM). This paper presents a new seismo-stratigraphic analysis of Quaternary deposits on the inner continental shelf offshore of southwestern Scotland. It correlates these data with new high resolution seafloor bathymetry and sediment cores to reconstruct the post-LGM retreat dynamics of the Hebrides Ice Stream, a major outlet of the last BIIS which drained across the continental shelf offshore of northwest Britain. Two primary glacigenic units (Units III and IV) are observed in seismic sequences from the region. Unit III partly corresponds to the previously defined Barra Formation, but is re-interpreted here as a time-transgressive subglacial to ice-proximal deposit. On the mid-shelf, this unit comprises grounding-zone wedges (GZWs). Within inshore waters and sea lochs Unit III can be found at or near seabed, where it is associated with retreat moraines, as well as with proglacial outwash sediments near the Kintyre coast (RSL ~10 m OD). The younger Unit IV (equivalent to the Jura Formation) represents ice-proximal to hemipelagic conditions. Bathymetric data imaged streamlined subglacial landforms recording ice sheet flow onto the inner shelf and a variety of transverse landforms collectively interpreted as moraines recording episodic retreat. These new data indicate that during the last deglaciation of the shelf offshore of southwestern Scotland the retreat dynamics of the Hebrides Ice Stream followed three main stages: i) tidewater margin retreat punctuated by stillstands on the inner shelf, ii) topography-controlled fjordic retreat, with evolution from a coherent ice-sheet to separate tidewater glaciers, and iii) stabilisation at the transition from a tidewater to land-based ice margin.

HL was funded by a NERC PhD studentship (NE/I528050/1) at Queen Mary University of London, the Queen Mary Postgraduate Research Fund, and an Arctic Field Grant from the Research Council of Norway through the University Centre in Svalbard (UNIS). SL acknowledges funding from the Westfield Trust. JCY was funded by a Carlsberg Foundation grant (2007/01/0383). A Royal Geographical Society Peter Fleming Award and a grant from the National Geographic Committee for Research and Exploration to Andy Hodson helped fund some of the fieldwork. Some surge-type glaciers on the High-Arctic archipelago of Svalbard have large glacitectonic composite ridge systems at their terrestrial margins. These have formed by rapid glacier advance into proglacial sediments during the active surge phase, creating multicrested moraine complexes. Such complexes can be formed during single surge advances or multiple surges to successively less-extensive positions. The few existing studies of composite ridge systems have relied on detailed information on internal structure and sedimentology to reconstruct their formation and links to surge processes. However, natural exposures of internal structure are commonly unavailable, and the creation of artificial exposures is often problematic in fragile Arctic environments. To compensate for these issues, we investigate the potential for reconstructing composite ridge system formation based on geomorphological evidence alone, focusing on clear morphostratigraphic relationships between ridges within the moraine complex and relict meltwater channels/outwash fans. Based on mapping at the margins of Finsterwalderbreen (in Van Keulenfjorden) and Grønfjordbreen (in Grønfjorden), we show that relict meltwater channels that breach outer parts of the composite ridge systems are in most cases truncated upstream within the ridge complex by an inner pushed ridge or ridges at their ice-proximal extents. Our interpretation of this relationship is that the entire composite ridge system is unlikely to have formed during the same glacier advance but is instead the product of multiple advances to successively less-extensive positions, whereby younger ridges are emplaced on the ice-proximal side of older ridges. This indicates that the Finsterwalderbreen composite ridge system has been formed by multiple separate advances, consistent with the cyclicity of surges. Being able to identify the frequency and magnitude of former surges is important as it provides insight into the past behaviour of surge-type glaciers and, if absolute dating is possible, allows for the assessment of surge-type glacier response to climate change on decadal to centennial timescales. Although further investigations into the internal structure of these deposits should be sought where possible, our study demonstrates that geomorphology could be an invaluable tool for reconstructing the formation of composite ridge systems. Postprint

Exhaustive sedimentological analysis of freshly exposed subglacial surfaces and moraines in southern Iceland provides diagnostic sedimentological signatures of: a) debris transport pathways through active temperate glacier snouts; and b) till production in subglacial traction zones dominated by deforming layers. Three till end members are recognised based on stratigraphic architecture: 1) thin and patchy tills over eroded bedrock; 2) single push moraines and complexes; and 3) overridden moraines or outwash fans. Typical till thicknesses are 0.10–1.40 m, with each till relating to a deformation event driven by the seasonally tuned processes of glacier sub-marginal shearing, freeze-on, squeezing and bulldozing. Clast form trends demonstrate progressive modification towards mature forms in subglacial traction zones with till being clearly differentiated from scree and glacifluvial deposits. Clast macrofabric strengths are variable, rarely matching those of laboratory shearing experiments, except where obviously lodged clasts are abundant. They also consistently record former glacier flow directions. But localized variability is introduced by bedrock protuberances, cavity infill, clast interference and freshly imported plucked clasts. Within tills, macrofabrics strengthen from lower (B horizon) to upper (A horizon) tills but at the outer edges of sub-marginally thickening till wedges or push moraines, seasonally-driven cycles of squeezing/flowage, freeze-on/melt-out and bulldozing give rise to a range of clast macrofabric strengths as well as superimposed deformation signatures. This reflects two extremes of till emplacement including the more mobile, flowing and often liquefied matrixes in push/squeeze moraines and, in contrast, the lodgement, deformation and ploughing at the thin end of sub-marginal till wedges.