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Abstract 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.

Fens have been forming in the river valleys of central Poland since the Bølling and went through a transformation from fully aquatic to semiterrestrial habitats during the Younger Dryas/Holocene transition. This drove plant and invertebrate communities and left a distinct pattern in chemical sediment composition, which is why river valley peatlands are sensitive palaeo-archives of climatic, hydrological and edaphic changes. Here we reconstruct the Late Weichselian history of the Bęczkowice fen in the upper Luciąża River valley using geochemical, pollen, Cladocera and Chironomidae proxies. Pollen-based age estimation indicates that the analysed peat sequence dates from the Bølling to Early Holocene. The layers 190-170 cm and 125-105 cm of the studied core were reworked by fluvial processes. Chironomidae and Cladocera communities indicate mostly limnetic conditions during the Allerød and early Younger Dryas. Peatland pools were supplied mostly by Luciąża River floods, but also by groundwater. Since the onset of the Holocene, the water level has dropped, eliminating aquatic midges and water fleas, and supporting taxa typical of astatic waters and wet soil. [ABSTRACT FROM AUTHOR]

In the Serteyka River valley in western Russia, eight accumulative fans formed at the mouths of ravines were examined geologically and geomorphologically. The test samples were collected from individual geological drillings made with a manual probe, as well as from excavations in the central and distal zones of the fans. Using the Gradistat program, sedimentological indicators were calculated, i.e. mean grain diameter (MZ), standard deviation (sorting -- σI), skewness (SkI) and kurtosis (KG),and then particle-size distribution frequency curves, cumulative curves and a Passega C/M diagram were drawn. It has been documented that the grain size of the fan sediments depends on the characteristics of the source material. Analysis of sedimentological indicators (mean grain diameter, sorting, skewness, kurtosis) showed the studied fans deposits to have a large variability of erosion and accumulation conditions. For the deposits of younger fans, the 2nd system of the MZ-versus-σI relationship after Mycielska- Dowgiałło (1995) was distinguished, while for the older, the 2nd, 3rd and 4th systems were recognised. The main process of grain transport within these forms was saltation. The ravines on the eastern slope of the Serteyka valley were most likely created in the periglacial period, while the gullies on the western side of the valley developed in the early modern period. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Pressurised meltwater has a major impact on ice dynamics, as well as on sedimentary and deformational processes occurring below/in front of glaciers and ice sheets, but its role in glaciotectonic processes is yet to be fully understood. This study explores micro- and macroscale structures developed within décollements in two thrust-block moraines of Late Weichselian age in Melasveit, western Iceland. The aim is to investigate how pressurised subglacial meltwater can aid the dislocation and transport of large, unfrozen and unlithified sediment blocks by glaciers. A detailed model is constructed for the development of the thrust-block moraines and the microscale processes occurring along their detachments during thrusting. The detachments are characterized by relatively thin zones of crosscutting hydrofractures, which reflect fluctuating water pressures during glaciotectonism. Little evidence of shearing is observed along the leading edges of the thrusts in both moraines. This is supported by high water pressures along the detachments and indicates that the thrust blocks were initially decoupled from the underlying deposits. As the thrust moraines evolved, an increased amount of shear occurred in between events of sediment liquefaction, hydrofracturing, and fluid escape. This was followed by progressive locking up of the detachments and eventual cessation in the accretion of the thrust blocks. [ABSTRACT FROM AUTHOR]

Onega Ice Lake developed in front of the receding Late Weichselian ice margin in Russian Karelia. Glacial varves that formed in Onega Ice Lake have been earlier studied by means of varve counts, palaeomagnetism and 14C AMS dates from small lakes north of modern Lake Onega and from Lake Onega proper. Synchronous changes in magnetic parameters and similar stratigraphy of these varve records together with the existence of basin-wide marker interval of pink-coloured varves have been used for core-to-core correlation and palaeogeographic interpretations. Unfortunately, there are missing varve-to-varve correlations between these cores. We present a 1155 yr long local varve chronology based on 3 parallel overlapping cores from two small lakes in the Zaonezhsky Peninsula at the northern coast of Lake Onega. Varve counts and matching of varve series were made from digital images. Following the textural, structural, colour and thickness changes of varves within Onega Ice Lake varve series, six characteristic varve units are identified. These clay units reflect changing sedimentary conditions at the time of accumulation that in general can be interpreted as a progressively increasing distance to the retreating ice margin. Variations in varve thickness superimposed on that overall trend, namely two episodes of abrupt and consistent decrease in varve thickness, do not correspond to known lake-level changes or shifts in outflow directions. AMS chronology for deglaciation of Lake Onega basin gives some evidences for correlation of above intervals of decreased varve thickness with the GI-1c2 and GI-1B cold events in NGRIP δ 18O event stratigraphy but further age estimations are needed to confirm presented correlations. Interval of reddish-brown varves – earlier described also as the 'pink horizon' – was observed in all studied sequences, and according to varve correlation, at the same stratigraphical level, which proves its basin-wide synchronous appearance. Ca 100 km south of our study area, Saarnisto and Saarinen (2001) reported ca 200 more varves compared to our results. Visual correlation of varve thickness graphs places these extra varves to the proximal part of the series and indicate a rapid ice recession from the main lake basin to the northern Lake Onega area with the ice recession rate ca 500 m per year. [ABSTRACT FROM AUTHOR]

Geomorphological evidence of catastrophic glacial floods has been discovered in many formerly glaciated areas of North America, in the mountains of Siberia and Central Asia, and in northern Europe. Within the area of the last Scandinavian Ice Sheet in the European Lowland a wide range of landforms related to glacial meltwater flows have been documented but no unequivocal evidence of cataclysmic glacial outburst floods exist. Here we discuss a landform signature of Late Weichselian glacial megafloods in the Suwałki Lakeland, north-eastern Poland. These landforms are oversized ice-marginal spillways, scabland-like features, expansion bars, megadunes, obstacle marks, and clusters of kettle holes. This unique glacial landscape was probably generated by at least two separate glacial megafloods (the older event ca 19 ka ago and the younger event shortly after ca 16 ka ago). Palaeohydraulic calculations based on the morphometric characteristics of the flood landforms suggest that one of those megafloods had water depth of at least 19 m and flow velocity of around 15–17 ms−1. The flood flow regime was from subcritical to supercritical. The calculated maximum flood discharge range was between 0.5 × 106 and 2.2 × 106 m3s−1 with the most likely value of around 2 × 106 m3s−1. These numbers place this megaflood among the largest glacial megafloods worldwide, with a possible impact on global climate through rapid release of large volumes of freshwater into the Atlantic Ocean following a transfer across the European Lowland through prominent ice-marginal meltwater spillways. [ABSTRACT FROM AUTHOR]

Abstract This paper focuses on the upland territory south-west of the Gulf of Gdańsk characterized by the existence of numerous hills with distinct ordering of their crest-line orientation. Characteristic features of relief in the Tczew Hump were analysed using GIS-based tools. Directional properties and morphometric characteristics are not uniform throughout the study area. Therefore, subsequent detailed analyses were performed after dividing it into three zones: north-western (NW), central and south-eastern (SE). The highest hills are situated in the central part of the Hump. The landforms analysed are mostly elongated, but they show varying elongation ratios (1.0–4.05). In general a NE-SW orientation is observed, however, the azimuthal distribution of their crest-lines shows considerable variation (from N-S to E-W). Two main systems of the crest-line orientation are distinguished: System A (NNE-SSW) and System B (NE-SW/ENE-WSW). The landforms considered are covered with till consisting of two subunits, what reflects two subsequent ice-sheet movement periods in the Late Weichselian but without releasing the area from ice-sheet cover. The subunits can be identified by changes in their petrographic composition – up to ten times more erratics of local provenance in the upper one than in the lower one. Ice flow direction during deposition of both till subunits, based on the till fabric of each of the three analysed sections, coincides with System A of the crest-lines. However, most of the till-covered hills fit System B, which suggests that they retained their previous (older than Late Weichselian) orientation. The complex relief of the Tczew Hump has a palimpsest nature and its arrangement emerged in several stages: (1) formation of the primeval relief before the Late Weichselian (hills built of sediments of heterogeneous ages); (2) partial relief reshaping in subglacial conditions during the two, successive, ice-flow events in the Late Weichselian (till-covered hills, clear bipartition of the till); (3) development of additional landforms during deglaciation − typically not covered with till (or with flow till on the slopes only), showing an orientation determined by the crevasse system developed in the ice. [ABSTRACT FROM AUTHOR]

Abstract Subglacial hydrology modulates how ice sheets flow, respond to climate, and deliver meltwater, sediment and nutrients to proglacial and marine environments. Here, we investigate the development of subglacial lakes and drainage networks beneath the Fennoscandian and Barents Sea ice sheets over the Late Weichselian. Utilizing an established coupled climate/ice flow model, we calculate high-resolution, spatio-temporal changes in subglacial hydraulic potential from ice sheet build-up (∼37 ka BP) to complete deglaciation (∼10 ka BP). Our analysis predicts up to 3500 potential subglacial lakes, the largest of which was 658 km2, and over 70% of which had surface areas <10 km2, comparable with subglacial lake-size distributions beneath the Antarctic Ice Sheet. Asynchronous evolution of the Fennoscandian Ice Sheet into the flatter relief of northeast Europe affected patterns of subglacial drainage, with up to 100 km3 more water impounded within subglacial lakes during ice build-up compared to retreat. Furthermore, we observe frequent fill/drain cycles within clusters of subglacial lakes at the onset zones and margins of ice streams that would have affected their dynamics. Our results resonate with mapping of large subglacial channel networks indicative of high-discharge meltwater drainage through the Gulf of Bothnia and central Barents Sea. By tracking the migration of meltwater drainage outlets during deglaciation, we constrain locations most susceptible to focussed discharge, including the western continental shelf-break where subglacial sediment delivery led to the development of major trough-mouth fans. Maps of hydraulic potential minima that persist throughout the Late Weichselian reveal potential sites for preserved subglacial lake sediments, thereby defining useful targets for further field-investigation. Highlights • We present modelled subglacial water storage and drainage between 37–10 ka BP. • Up to 3500 potential subglacial lakes predicted during LGM, storing >460 km3 of water. • Subglacial lake clusters are predicted with potential for fill/drain cycles and flood events. • Persistent lakes over the glaciation define potential sites for preserved sediments. • Catchment evolution and drainage outlet migration reveals subglacial discharge foci. [ABSTRACT FROM AUTHOR]

Abstract Recent synoptic studies have summarized the former spatial extent and chronology of the last Scandinavian Ice Sheet (SIS) and provide exceptional compilations of empirical datasets. The latter represent the primary source of information for the modelling community to test and develop thermomechanical ice sheet model, which are then further embedded into climatic and general circulation models. The Last Glacial Maximum (LGM) extent and chronology of the SIS across continental Europe were highlighted as being the least well-known thus generating the biggest uncertainties in the reconstruction of the ice sheet. While early geomorphological studies of the ice sheet marginal belts are numerous and detailed in western Russia, geochronological data are virtually inexistent. In an attempt to fill in this gap, we conducted a series of sampling campaigns for surface exposure dating using 10Be in the western and northwestern regions of Russia. We present here the first results from the Valday Heights where glacial deposits constitute well-preserved margins of the SIS. A total of 16 samples firmly establish the timing of the LGM in the Valday Heights at 20.1 ± 0.4 ka. The Valday Heights acted as a natural wall for the last maximum advance of the SIS during MIS2, constraining the eastern flank of the Ladoga-Ilmen-Lovat ice stream to the west of the hills. The Valday Heights were only overran by previously more extensive glacial advances as suggested by older exposure ages obtain on erratic boulders (31.2 ± 1.4 to 47.1 ± 1.5 ka) located east of the LGM limit. Highlights • We conducted a series of sampling campaigns for surface exposure dating using 10Be in W and NW Russia. • A total of 16 samples firmly establish the timing of the LGM in the Valday Heights at 20.1 ± 0.4 ka. • The Valday Heights acted as a natural wall for the last maximum advance of the SIS during MIS2. • Older exposure ages east of the Valday Heights suggest that the region was overran by more a extensive ice sheet prior the LGM. [ABSTRACT FROM AUTHOR]

The Eurasian ice sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum with a span of over 4500 km and responsible for around 20 m of eustatic sea-level lowering. Whilst recent terrestrial and marine empirical insights have improved understanding of the chronology, pattern and rates of retreat of this vast ice sheet, a concerted attempt to model the deglaciation of the EISC honouring these new constraints is conspicuously lacking. Here, we apply a first-order, thermomechanical ice sheet model, validated against a diverse suite of empirical data, to investigate the retreat of the EISC after 23 ka BP, directly extending the work of Patton et al. (2016) who modelled the build-up to its maximum extent. Retreat of the ice sheet complex was highly asynchronous, reflecting contrasting regional sensitivities to climate forcing, oceanic influence, and internal dynamics. Most rapid retreat was experienced across the Barents Sea sector after 17.8 ka BP when this marine-based ice sheet disintegrated at a rate of ∼670 gigatonnes per year (Gt a −1 ) through enhanced calving and interior dynamic thinning, driven by oceanic/atmospheric warming and exacerbated by eustatic sea-level rise. From 14.9 to 12.9 ka BP the EISC lost on average 750 Gt a −1 , peaking at rates >3000 Gt a −1 , roughly equally partitioned between surface melt and dynamic losses, and potentially contributing up to 2.5 m to global sea-level rise during Meltwater Pulse 1A. Independent glacio-isostatic modelling constrained by an extensive inventory of relative sea-level change corroborates our ice sheet loading history of the Barents Sea sector. Subglacial conditions were predominately temperate during deglaciation, with over 6000 subglacial lakes predicted along with an extensive subglacial drainage network. Moreover, the maximum EISC and its isostatic footprint had a profound impact on the proglacial hydrological network, forming the Fleuve Manche mega-catchment which had an area of ∼2.5 × 10 6 km 2 and drained the present day Vistula, Elbe, Rhine and Thames rivers through the Seine Estuary. During the Bølling/Allerød oscillation after c. 14.6 ka BP, two major proglacial lakes formed in the Baltic and White seas, buffering meltwater pulses from eastern Fennoscandia through to the Younger Dryas when these massive proglacial freshwater lakes flooded into the North Atlantic Ocean. Deglaciation temporarily abated during the Younger Dryas stadial at 12.9 ka BP, when remnant ice across Svalbard, Franz Josef Land, Novaya Zemlya, Fennoscandia and Scotland experienced a short-lived but dynamic re-advance. The final stage of deglaciation converged on present day ice cover around the Scandes mountains and the Barents Sea by 8.7 ka BP, although the phase-lagged isostatic recovery still continues today. [ABSTRACT FROM AUTHOR]

The Late Weichselian marine and glaciomarine sediments occurring in many places along the coast of Iceland are rich in invertebrate fossils, especially mollusks and barnacles. A diverse ichnofauna, constituted especially by bioerosional traces documenting the activity of predators and animals that use the host shell for attachment or the construction of dwellings, was identified at the localities of Ósmelur, Saurbær, and Brekkubakkar in southwestern Iceland. The ichnotaxa identified includeAnellusichnus circularis(Santos, Mayoral, and Muñiz),Caulostrepsisisp.,Centrichnus concentricus(Bromley and Martinell),Clionolithesisp.,Finichnus peristroma(Taylor, Wilson, and Bromley),Finichnusisp.,Sedilichnus asperus(Nielsen and Nielsen),Sedilichnuscf.excavatus(Donovan and Jagt),Sedilichnus gradatus(Nielsen and Nielsen),Sedilichnus smileyisp. nov.,Sedilichnus ovalis(Bromley),Sedilichnus paraboloides(Bromley),Sedilichnus simplex(Bromley), andSedilichnus spongiophilus(Müller). [ABSTRACT FROM PUBLISHER]

ABSTRACT Observations of subglacial landforms yielding the configuration and dynamics of former ice-flows have for the first time been made in Rijpfjorden and Duvefjorden, Nordaustlandet, Svalbard, using sub-bottom acoustic, swath-bathymetric data and sediment cores. Five acoustic-stratigraphic units were distinguished suggesting the presence of a complete glacial-postglacial succession in the central fjord basins. 14C ages from the sediments indicate that the inner Rijpfjorden and central Duvefjorden were deglaciated before ca. 10.6 cal ka BP and 11.0 cal ka BP, respectively. Maximum sediment thickness in Rijpfjorden and Duvefjorden is 26 m, resulting in sediment accumulation rates of ca. 66 cm ka−1. The landform record suggests that the ice streaming in both fjords was topographically controlled. The considerably deeper basin and higher elongation ratios of the crag-and-tails in Duvefjorden are linked to the faulted bedrock and possibly to somewhat larger ice stream and/or more focused ice-flow compared to that in Rijpfjorden. De Geer moraines suggest slower retreat of a grounded ice margin from shallow areas of Rijpfjorden. In deeper areas of the fjords, the glaciers were probably floating, resulting in the lack of ice-marginal transverse landforms. The ice margin retreat from these areas was probably relatively rapid and dominated by calving. [ABSTRACT FROM AUTHOR]

The fragmentary glacial-geological record across the Icelandic continental shelf has hampered reconstruction of the volume, extent and chronology of the Late Weichselian ice sheet particularly in key offshore zones. Marine geophysical data collected over the last two decades reveal that the ice sheet likely attained a continental shelf-break position in all sectors during the Last Glacial Maximum, though its precise timing and configuration remains largely unknown. Within this context, we review the available empirical evidence and use a well-constrained three-dimensional thermomechanical model to investigate the drivers of an extensive Late Weichselian Icelandic ice-sheet, its sensitivity to environmental forcing, and phases of deglaciation. Our reconstruction attains the continental shelf break across all sectors with a total ice volume of 5.96 × 10 5 km 3 with high precipitation rates being critical to forcing extensive ice sheet flow offshore. Due to its location astride an active mantle plume, a relatively fast and dynamic ice sheet with a low aspect ratio is maintained. Our results reveal that once initial ice-sheet retreat was triggered through climate warming at 21.8 ka BP, marine deglaciation was rapid and accomplished in all sectors within c. 5 ka at a mean rate of 71 Gt of mass loss per year. This rate of ice wastage is comparable to contemporary rates observed for the West Antarctic ice sheet. The ice sheet subsequently stabilised on shallow pinning points across the near shelf for two millennia, but abrupt atmospheric warming during the Bølling Interstadial forced a second, dramatic collapse of the ice sheet onshore with a net wastage of 221 Gt a −1 over 750 years, analogous to contemporary Greenland rates of mass loss. Geothermal conditions impart a significant control on the ice sheet's transient response, particularly during phases of rapid retreat. Insights from this study suggests that large sectors of contemporary ice sheets overlying geothermally active regions, such as Siple Coast, Antarctica, and NE Greenland, have the potential to experience rapid phases of mass loss and deglaciation once initial retreat is initiated. [ABSTRACT FROM AUTHOR]

We present a detailed study of an alluvial fan accumulated in a piggyback basin syn-kinematically to the emergence of a Weichselian glacitectonic complex (Jasmund peninsula, SW Baltic Sea). Although sediments formed contemporaneously with glacitectonic events have already been documented, a systematic approach is missing so far. Facies, architecture and distribution of alluvial-fan deposits are identified here as key features for analyzing glacitectonic complexes. The deposition of those syn-kinematic deposits was controlled by the progradation of thrust-faults and the resulting morphologic changes of both the thrust-bounded ridges and the adjacent piggyback basins. Another controlling factor is the episodic high runoff of meltwater discharge (glacial lake outburst flood, jökulhlaup) from lakes near the ice front. Sheetflood and debris-flow processes dominated the sedimentation and gave way to alluvial-fan, fan-delta and glacifluvial deposits. A stepwise rotation of the depositional plain within the piggyback basin is indicated by internal unconformities and the distinct converging stratal geometry. Based on three luminescence ages the development of the syn-kinematic alluvial-fan sequence and consequently of the glacitectonic complex took place between 21 and 19 ka during a late Weichselian readvance of the Scandinavian Ice Sheet. The overall results are summarized in a seven-stage genetic model, beginning with the initial glacitectonic phase and ending with the overfilled piggyback basin and subsequent overriding of the structure by the glacier front. With the presented criteria, the successive growth of the alluvial-fan deposits can be linked directly with the emergence of a glacitectonic complex formed during an ice advance. • Syn-kinematic alluvial fan deposits are vital strata of glacitectonic complexes. • Piggyback basins emerging between thrust-bounded ridges of glacitectonic complexes. • Fault propagation controls piggyback basin morphology and basin fill in glacitectonic complex. • Periodic glacial outburst floods are responsible for deposition on alluvial fan. • Jasmund Glacitectonic Complex (SW Baltic Sea) was formed between 21 and 19 ka. [ABSTRACT FROM AUTHOR]

The Eurasian ice-sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum (LGM), after the Antarctic and North American ice sheets. Despite its global significance, a comprehensive account of its evolution from independent nucleation centres to its maximum extent is conspicuously lacking. Here, a first-order, thermomechanical model, robustly constrained by empirical evidence, is used to investigate the dynamics of the EISC throughout its build-up to its maximum configuration. The ice flow model is coupled to a reference climate and applied at 10 km spatial resolution across a domain that includes the three main spreading centres of the Celtic, Fennoscandian and Barents Sea ice sheets. The model is forced with the NGRIP palaeo-isotope curve from 37 ka BP onwards and model skill is assessed against collated flowsets, marginal moraines, exposure ages and relative sea-level history. The evolution of the EISC to its LGM configuration was complex and asynchronous; the western, maritime margins of the Fennoscandian and Celtic ice sheets responded rapidly and advanced across their continental shelves by 29 ka BP, yet the maximum aerial extent (5.48 × 10 6 km 2 ) and volume (7.18 × 10 6 km 3 ) of the ice complex was attained some 6 ka later at c. 22.7 ka BP. This maximum stand was short-lived as the North Sea and Atlantic margins were already in retreat whilst eastern margins were still advancing up until c. 20 ka BP. High rates of basal erosion are modelled beneath ice streams and outlet glaciers draining the Celtic and Fennoscandian ice sheets with extensive preservation elsewhere due to frozen subglacial conditions, including much of the Barents and Kara seas. Here, and elsewhere across the Norwegian shelf and North Sea, high pressure subglacial conditions would have promoted localised gas hydrate formation. [ABSTRACT FROM AUTHOR]

The Dubičiai glaciolacustrine basin was studied by means of geomorphological, lithological and cartographic methods in order to reconstruct water level changes during postglacial time. The formation of the basin and respective sedimentation processes began immediately after the deglaciation. Glaciolacustrine terraces in the Dubičiai basin formed during the Frankfurt (Grūda) Stage of the last glaciation, and during the Dryas–Allerød, Boreal and Subatlantic chronozones. Intense evolution of the basin took place at the end of the Late Pleistocene and in the Early Holocene. The greatest changes in the topography were due to thermokarst processes which began in the Allerød and continued until the Boreal. Climate became warm and moist at the beginning of the Preboreal and thus created good conditions for accumulation of gyttja, peat and freshwater lime. The latest stage in the development of the Dubičiai basin occurred in the 19th century. In 50 years the area of the basin decreased by 10 times: from 221 ha in 1850 to 20 ha in 1900. The last major change in the hydrographic network of the basin occurred in 1958–59 when an artificial drainage project was completed.

Three sediment cores from the northern part of Lake Peipsi in eastern Estonia were analysed for their ostracod content. The investigated sediments consist of late Weichselian glaciolacustrine varved and homogeneous clay, lake marl, and gyttja. Altogether eight freshwater ostracod species were identified. The distribution of ostracods in L. Peipsi deposits is mostly limited to the lake marl interval. Ostracods made their appearance in shallow-water conditions and were represented by species preferring cold water. The continuous presence of Ilyocypris bradyi refers to the existence of a shallow body of water through the whole period of marl accumulation. Two sediment intervals where Herpetocypris reptans is present and Darwinula stevensoni is absent are interpreted as regressional episodes during the low lake level stage, which were possibly caused by a temporary warming accompanied by increased productivity. Water level in L. Peipsi during the late Weichselian–Early Holocene was ca 10 m lower than at present. According to palynological and radiocarbon data, lake marl with the presence of calcareous fossils started to accumulate at the Younger Dryas–Preboreal transition and continued through the entire Preboreal Chronozone.

A detailed reconstruction of palaeo-ice flow configuration is lacking for the Kola Peninsula and Russian Lapland, northwest Arctic Russia. This study presents, for the first time, a 14-stage reconstruction of the last Fennoscandian Ice Sheet (FIS) flow configuration on the Kola Peninsula and Russian Lapland from build-up to complete deglaciation. Flowsets (n = 102) and cross-cutting bedform assemblages identified from a high-resolution subglacial bedform record (subglacial lineations and subglacial ribs) are combined with subglacially streamlined bedrock data to define ice flow patterns, ice divides, ice margins, and glaciation styles of the last glaciation through relative time. The results demonstrate that the FIS flow configuration was not static. The FIS advanced eastwards across the region from Scandinavia, rather than expanding from local upland areas, and established a predominantly cold-based ice mass on the Kola Peninsula with an extensive adjacent warm-based ice lobe in the White Sea. An east-west aligned ice divide was located on the Kola Peninsula and Russian Lapland during the ice sheet build-up stages. However, this divide was short-lived as the White Sea lobe dominated ice flow on the peninsula during the local-Last Glacial Maximum, and ice predominantly flowed across the region from the main ice dispersal zone that was centred over the Gulf of Bothnia during deglaciation. Deglaciation on the peninsula was initially characterised by cold-based ice sheet retreat on the central eastern Kola Peninsula and warm-based ice lobe retreat in the White Sea. Continued deglaciation was characterised by ice sheet thinning, exposing mountain summits as nunataks behind the ice sheet margin, with topography constraining ice flow around upland areas. Ice streams in the region were drivers and consequences of continued ice sheet configuration change throughout glaciation. Four palaeo ice streams – (i) the Imandra Ice Stream; (ii) the Lovozero Ice Stream; (iii) the Kanozero Ice Stream; and (iv) the Kuusamo Ice Stream – and three possible palaeo-ice stream pathways are identified. We consider our ice flow configuration reconstruction to be the simplest palaeo-glaciological interpretation of the bedform record of the Kola Peninsula and Russian Lapland. The empirically-based reconstruction of ice flow geometry provides a regional framework and context for interpreting results from local-scale fieldwork, and is presented in a format that can be utilised by numerical ice sheet modellers to test and verify their models. The results underpin a new data-driven reconstruction of the last FIS in northwest Arctic Russia that we present in Part 2 of this study. • First comprehensive ice flow configuration synthesis from a high-resolution bedform record in northwest Arctic Russia. • 102 discrete flow events and their relative chronology identified. • 14-stage reconstruction of Fennoscandian Ice Sheet evolution on the Kola Peninsula and Russian Lapland. • Evidence to support a transient ice divide in northwest Arctic Russia. • Four definite and three possible palaeo-ice stream pathways in northwest Arctic Russia. [ABSTRACT FROM AUTHOR]

The pattern, style, and timing of glaciation of the last Fennoscandian Ice Sheet (FIS) on the Kola Peninsula and Russian Lapland (northwest Arctic Russia) is widely debated. This is due, in part, to the lower-resolution empirical data used in previous investigations. In this paper, we present an ice margin reconstruction, an updated database of previously published numerical ages, and a new time-slice reconstruction. The reconstruction, which is presented across a series of 10 maps, documents the spatial evolution of the ice sheet every 1000 years between 16 and 11 ka, and for four selected time periods back to 29 ka (19–17, 21–20, 25–22, and 29–26 ka). Our reconstruction indicates that the Kola Peninsula and Russian Lapland was probably ice-free prior to the advance of the FIS c. 29 ka. The FIS reached its maximum lateral extent in northwest Arctic Russia c. 19–17 ka, later than many other sectors of the ice sheet. This disparity probably arises as a result of both the topography of Fennoscandia and the position of the Kola Peninsula and Russian Lapland in a precipitation shadow of the Scandinavian Mountains. Thus, FIS glaciation in northwest Arctic Russia was strongly influenced by a fluctuating climate. Most of the FIS in northwest Arctic Russia was terrestrial-based, although marine-terminating margins existed in the fjords of northern Russian Lapland. The retreat of the White Sea lobe was probably not influenced by marine transgression until c. 12 ka because palaeo-sea levels during most of the Late Weichselian were considerably lower than present, and a shallow sill in the Mouth of the White Sea would have inhibited ocean waters entering the White Sea basin. Instances of ice margin readvance during deglaciation are also apparent, including a significant readvance of the White Sea lobe c. 14 ka. This study presents the first reconstruction grounded in high-resolution empirical data for the Kola Peninsula and Russian Lapland, and is presented in a time-slice format that is of critical importance for testing and validating numerical ice sheet and climate models. • First comprehensive glacial reconstruction synthesis from a high-resolution glacial landform record. • Ice margin reconstruction derived from six independent lines of evidence. • Numerical age database including 209 numerical ages is compiled. • Reconstruction of Fennoscandian Ice Sheet flow configuration and margin positions from build-up to complete deglaciation on the Kola Peninsula and Russian Lapland. [ABSTRACT FROM AUTHOR]

We studied the water-level changes and palaeogeography of Late Weichselian proglacial lakes in eastern Estonia using the shoreline and sediment distribution proxies from the Saadjärve Drumlin Field area together with the geomorphological correlation and GIS-based palaeoreconstructions. Our results show that about 14.0-13.8 cal. kyr BP Glacial Lake Peipsi inundated large areas of the Saadjärve Drumlin Field, Emajõgi River valley and reached the Lake Võrtsjärv basin. In the Saadjärve Drumlin Field area this is reflected in the formation of the highest shoreline and the corresponding rather short period (up to 63 years) of varved clay accumulation. The highest shoreline determined in the Saadjärve Drumlin Field is correlated with the valley terraces in southeastern Estonia, which reflect the water level in Glacial Lake Peipsi and the proglacial lake in the Võrtsjärv basin. The study suggests settling of glacial varved clay in the deepest inter-drumlin basins at the critical (minimal) water depths of about 15-20 m. The proglacial conditions lasted in the Saadjärve Drumlin Field for about 150 years and were interrupted due to the isolation of the lakes from proglacial bodies of water in the Peipsi and Võrtsjärv basins after the formation of the second highest shoreline. In the bottom sediments this isolation is marked by the transition from the laminated sediments to the massive silt interval. The results show that about 14.0-13.8 cal. kyr BP the connection route between Glacial Lake Peipsi and proglacial Lake Strenči, northern Latvia, shifted from the Võhandu-Hargla valley to the Väike-Emajõgi valley and the strait between Glacial Lake Peipsi and large Lake Privalday in northwestern Russia was closed.

The flow of the Atlantic Water (AW) via the Return Atlantic Current (RAC) regulates the oceanographical conditions in the Northwestern (NW) Greenland Sea in the Fram Strait. As the intensity of the RAC might significantly influence both deep-water formation in the area and the stability of the Northeast Greenland Ice Sheet (NE GIS), knowledge of its variability in the past is important. Here we present a reconstruction of the paleoceanographic forcing of the AW on climatic conditions and associated environmental changes in the NW Greenland Sea by means of foraminiferal assemblages, stable (oxygen and carbon) isotopes, and various sedimentological parameters from sediment core GR02-GC retrieved from NE Greenland continental slope (1170 m water depth). Our data indicate an almost continuous presence of AW in the NW Greenland Sea during the last 35 kyr BP. Two peaks of low planktic δ18O values at ∼34.5 and 33 kyr BP are interpreted as meltwater signals associated with warm AW-induced melting of the adjacent NE GIS. The NE GIS advanced between 32 and 29 kyr BP, resulting in reduced meltwater influx to the NW Greenland Sea. Increased iceberg calving and melting after 29 kyr BP, were probably linked to surface warming and glacier advance to the shelf-break lasting until 23.5 kyr BP. During the Last Glacial Maximum, the extensive sea ice cover was associated with the presence of subsurface AW at the study site. During the Bølling–Allerød (B/A, ∼14.6–12.7 kyr BP) strong melting of glaciers and sea ice was probably caused by the combined effect of the B/A warming and the flow of warm AW. The RAC was weakened during the Younger Dryas (∼12.8–11.7 kyr BP), which reduced the advection of warm AW to the NW Greenland Sea. After 11.7 kyr BP, the RAC reached its modern strength, whereas, during the Holocene Thermal Maximum, it reached its maximum strength for the study period. In addition, short-term weakening of AW inflow to the core site was observed, especially at 10.5, 8.5, and 5.8 kyr BP. • Almost continuous presence of Atlantic Water was recorded in the NW Greenland Sea during the last 35 kyr BP. • The Greenland Ice Sheet advanced between 32 and 29 kyr BP and 26 and 23.5, reducing meltwater influx to the NW Greenland Sea. • The Last Glacial Maximum is associated with extensive sea ice cover, with the presence of subsurface AW. • Permanent inflow of warm AW via Return Atlantic Current to NW Greenland Sea started after the Bølling-Allerød, ∼13 kyr BP. [ABSTRACT FROM AUTHOR]

The area of the Kashubian Coastland and areas adjacent to the northern part of the Lower Vistula Valley (northern Poland) were involved in the major transgressive phases distinguished in Poland during the Late Weichselian. Due to the small scale of the regressions between the different phases of the Late Weichselian, the ice sheet usually deposited only one till, but with a complex vertical profile. Based on the studies of the directional properties, petrographic composition of the fine gravel fraction and the analysis of indicator erratics, the dichotomy of the till bed was demonstrated. The petrographic composition of the gravel fraction in tills together with the analysis of the indicator erratics and delimitation of the Theoretical Boulder Centres were used to determine the direction of the influx of ice masses. This allowed speculation on the reasons for the different dynamics of the Fennoscandian Ice Sheet (FIS) as well as the operation and time variability of the Baltic Ice Stream (BIS). It was emphasised that the delivery system of debris by the ice sheet might have been complex and multidirectional (more than one route). It has been suggested that changes in the petrographic composition of the gravel fraction of the glacial sediments did not have to be associated only with shifting the centre of glaciation, but may have resulted from a change in the thermal regime of the ice sheet's bed in the source area (especially with the spread of the cold regime zone), and depended on the dynamics of the ice sheet (stream or sheet flow) as well as the spatial and temporal conditions of its development in the deposition area. [ABSTRACT FROM AUTHOR]

The Bezedna site represents a unique lake-mire complex in the Lublin chalkland, eastern Poland. This karst region contains Upper Cretaceous carbonate rocks under the influence of continental climate. Using sedimentologic, palaeobotanical, and fossil ostracode analyses as well as radiocarbon dating on cores, we were able: (1) to reconstruct the morphogenetic mechanisms related to lake formation, (2) to describe the main stages of lake evolution, and (3) to identify the environmental conditions during this evolution. The first stage was the formation of an accumulation basin in a periglacial setting related to permafrost thawing in the last phase of the Weichselian and at the beginning of the Holocene. During the second stage, in the successive phases of the Holocene, lake evolution was determined by climate changes and local conditions, and in the youngest Subatlantic period-also by human activity in several settlement phases. Natural water bodies in a karstic region create unique conditions for water circulation, especially for groundwater. During the change from the periglacial to temperate climate of the Holocene in the Lublin chalkland, the response of substratum (deeply frozen during the Weichselian) was influential in the development of surface water conditions in the study area. The strong fracturing of the Upper Cretaceous bedrock and general change of groundwater circulation associated with the activation of an ascending groundwater supply favored the intensive dissolution of carbonate and the progressive ground subsidence. Based on the reconstruction and correlation with paleoenvironmental investigations of the adjacent Volhynia chalkland, we were able to estimate and compare the influences of local (morphologic and geologic) conditions versus global climate changes on the paleoenvironmental record. Climate-driven lake-level fluctuations coincided over great areas of the Northern Hemisphere and are well reflected in changes of the Ostracoda fauna. [ABSTRACT FROM AUTHOR]

A new varve chronology comprising 584 consecutive varve years, varve thickness changes and proglacial sedimentary environment are analysed across the Pandivere–Neva (>13 300 yr BP) belt of ice-recessional formations in coastal Estonia, eastern Baltic. Varved clays in the area have been deposited in the Baltic Ice Lake. All investigated sequences display a normal varve series with decreasing varve thickness upwards. According to the varve correlation, two groups of varve graphs could be distinguished: those representing sequences from the distal side and from the proximal side of the Pandivere–Neva ice marginal formations. Accumulation of varved clays started ca. 100 yr earlier in the distal part. A massive clay unit with corresponding 20 silty varves in some sequences precedes the beginning of varve formation at the proximal part of the basin and could therefore correspond to a ca. 20 yr long ice-stagnation period during the Pandivere–Neva Stade. Ice proximal conditions on both sides of the recessional formations (within 30 km distance) ceased simultaneously within a period of 10–15 yr, which is reflected in reduced total varve thickness accompanied with the beginning of winter layer dominance within a single varve. Because of post-sedimentary erosion, the length of the presented chronology underestimates the duration of proglacial conditions. Good visual correlation between the mean varve thickness graphs from the Pärnu area and from Lake Peipsi, eastern Estonia, indicate the possible regional causes of varve thickness changes and simultaneous varve formation in two basins. [ABSTRACT FROM AUTHOR]

To better understand the past retreat patterns and chronologies of major marine-terminating outlet glaciers, the Late Weichselian and Holocene glacial history of a NE Greenland fjord system is reconstructed using new and previously published swath bathymetry and high-resolution seismic data, supplemented with multi-proxy analysis of sediment cores. The investigated area extends more than 190 km, including Fosters Bugt, Kejser Franz Josef Fjord, Nordfjord and Moskusoksefjord, the drainage routes for Waltershausen Gletscher, one of the largest outlet glaciers in the NE sector of the Greenland Ice Sheet. A complex of moraine ridges identified in Fosters Bugt show former stillstand positions during this period, and, alongside radiocarbon ages, supports the theory of a maximum ice front position in the outer coastal areas during the Younger Dryas-Preboreal period. The retreat moraines distributed within the Kejser Franz Josef Fjord system provide evidence of a stepwise retreat during the last deglaciation, whereby rapid retreat was interrupted by episodes of stillstands and/or readvances of the grounding line. The fjord system was mostly deglaciated prior to 7.8 ka cal BP, with an estimated average retreat rate ranging between 33 and 96 m a−1 since the Younger Dryas. Following this, only minor ice advances in the inner fjords have been identified. The sediment supply from Waltershausen Gletscher dominated the Kejser Franz Josef Fjord, Nordfjord and outer Moskusoksefjord throughout the Holocene period, whereas in the middle and inner Moskusoksefjord the sediment deposits reflect a more local catchment area. The estimated average retreat rate is in the same order of magnitude as the rates from fjords of northern Fennoscandia, indicating the same overall control for the deglaciation, ice melting from increased Northern Hemisphere summer insolation that peaked in Early Holocene. • Maximum ice front position in the outer coastal areas during the Younger Dryas-Preboreal period. • Rapid retreat was interrupted by episodes of stillstands and/or readvances. • The fjord system was mostly deglaciated prior to 7.8 ka cal BP. • Estimated retreat rate ranged between 33 and 96 m a−1 since the Younger Dryas. [ABSTRACT FROM AUTHOR]

The chronology and configuration of the Svalbard Barents Sea Ice Sheet (SBSIS) during the Late Weichselian (LW) are based on few and geographically scattered data. Thus, the timing and configuration of the SBSIS has been a subject of extensive debate. We present provenance data of erratic boulders and cosmogenic 10Be ages of bedrock and boulders from Northwest Spitsbergen (NWS), Svalbard to determine the thickness, configuration and chronology during the LW. We sampled bedrock and boulders of mountain summits and summit slopes, along with erratic boulders from coastal locations around NWS. We suggest that a local ice dome over central NWS during LW drained radially in all directions. Provenance data from erratic boulders from northern coastal lowland Reinsdyrflya suggest northeastward ice flow through Liefdefjorden. 10Be ages of high-elevation erratic boulders in central NWS (687–836 m above sea level) ranging from 18.3 ± 1.3 ka to 21.7 ± 1.4 ka, indicate that the centre of a local ice dome was at least 300 m thicker than at present. 10Be ages of all high-elevation erratics (>400 m above sea level, central and coastal locations) indicate the onset of ice dome thinning at 25–20 ka. 10Be ages from erratic boulders on Reinsdyrflya ranging from 11.1 ± 0.8 ka to 21.4 ± 1.7 ka, indicate an ice cover over the entire Reinsdyrflya during LW and a complete deglaciation prior to the Holocene, but apparently later than the thinning in the mountains. Lack of moraine deposits, but the preservation of beach terraces, suggest that the ice covering this peninsula possibly was cold-based and that Reinsdyrflya was part of an inter ice-stream area covered by slow-flowing ice, as opposed to the adjacent fjord, which possibly was filled by a fast-flowing ice stream. Despite the early thinning of the ice sheet (25–20 ka) we find a later timing of deglaciation of the fjords and the distal lowlands. Several bedrock samples (10Be) from vertical transects in the central mountains of NWS pre-date the LW, and suggest either ice free or pervasive cold-based ice conditions. Our reconstruction is aligned with the previously suggested hypothesis that a complex multi-dome ice-sheet-configuration occupied Svalbard and the Barents Sea during LW, with numerous drainage basins feeding fast ice streams, separated by slow flowing, possibly cold-based, inter ice-stream areas. [ABSTRACT FROM AUTHOR]

Abstract: The Late Weichselian and Holocene (fluvio-)aeolian sands of the type locality Lutterzand in the E Netherlands have been the focus of many palaeoclimatic, palaeoenvironmental and geochronological studies. In the present study, an accurate and detailed chronological framework has been established using radiocarbon and optically stimulated luminescence dating. Additionally, the sedimentological characteristics of the fluvio-aeolian and aeolian sequences have been reinvestigated. Four main phases of (fluvio)aeolian sedimentation have been differentiated in the Lutterzand sections, consistent with the Late Pleniglacial, the pre-Allerød Lateglacial, the Late Dryas, and the Late Holocene. From at least 25.2 ± 1.9 ka up to 19.9 ± 1.6 ka, the area was marked by a transition from fluvial to aeolian deposition under continuous permafrost conditions (Older Coversand I). The Beuningen Gravel Bed is considered as the lithostratigraphic marker for permafrost degradation, shallow channelling and aeolian deflation associated with the formation of a desert pavement. Localised fluvial sedimentation in shallow channels took place in two phases, a first from ∼20 ka to ∼23 ka, and a second at around 16 ka; the desert pavement formed in between ∼16 ka and ∼14 ka, but probably shortly after 16 ka. The aeolian sediments overlying the Beuningen Gravel Bed were deposited as sand sheets and low dunes, and yielded ages between 15.8 ± 1.4 ka and 12.2 ± 0.9 ka. Although the OSL ages seem to point to fairly continuous coversand sedimentation during the Lateglacial, the intercalated Usselo Soil allows distinguishing a pre-Allerød phase (resulting in the Older Coversand II and the Younger Coversand I between 15.8 ± 1.4 ka and 12.3 ± 1.0 ka) from a post-Allerød phase (with deposition of the Younger Coversand II between 13.6 ± 1.1 ka and 12.2 ± 0.9 ka). During the major part of the Holocene, (podzol) soil formation occurred in the top of the aeolian sediments. Probably due to human activities, local erosion of the upper part of the Lateglacial sequences and redeposition took place. These drift-sands were dated between 0.40 ± 0.04 ka and 0.20 ± 0.02 ka. [Copyright &y& Elsevier]

Subsurface sediments of a 120 cm deep trench from Ny-Alesund, Svalbard, were analysed for pollenspores and other organic matter contents. This study is supported by two AMS C dates (27, 200 yrs BP and 8,762 yrs BP) at the bottom and topmost litho-unit of the trench, respectively. The pollen record provides an evidence of a warm interval at about 27,200 yr BP (Late Weichselian and MIS 3) and cooling episode around 8,762 yr BP. This is also supported by the amount and type of organic matter as well as sediment type and depositional history of the trench sediments. [ABSTRACT FROM AUTHOR]

The Dubičiai glaciolacustrine basin was studied by means of geomorphological, lithological and cartographic methods in order to reconstruct water level changes during postglacial time. The formation of the basin and respective sedimentation processes began immediately after the deglaciation. Glaciolacustrine terraces in the Dubičiai basin formed during the Frankfurt (Grūda) Stage of the last glaciation, and during the Dryas—Allerød, Boreal and Subatlantic chronozones. Intense evolution of the basin took place at the end of the Late Pleistocene and in the Early Holocene. The greatest changes in the topography were due to thermokarst processes which began in the Allerød and continued until the Boreal. Climate became warm and moist at the beginning of the Preboreal and thus created good conditions for accumulation of gyttja, peat and freshwater lime. The latest stage in the development of the Dubičiai basin occurred in the 19th century. In 50 years the area of the basin decreased by 10 times: from 221 ha in 1850 to 20 ha in 1900. The last major change in the hydrographic network of the basin occurred in 1958?59 when an artificial drainage project was completed. [ABSTRACT FROM AUTHOR]

Abstract: Multi-proxy analyses of two sediment cores from central Isfjorden were used to reconstruct the glacial history in central Spitsbergen during the Late Weichselian and the Holocene, and to relate iceberg rafting and sea-ice rafting to climatic and oceanographic changes in the north Atlantic region. A basal till was deposited beneath an ice stream prior to 12,700cal. years BP (calendar years before the present). Several tidewater glaciers influenced the sedimentary environment during the Younger Dryas and probably already during the Allerød. The Younger Dryas cooling might be reflected by enhanced sea-ice formation and suspension settling, as well as reduced iceberg rafting. The final deglaciation was dominated by intense iceberg rafting. It terminated around 11,200cal. years BP. Optimum Holocene climatic and oceanographic conditions with significantly reduced ice rafting occurred between c. 11,200 and 9000cal. years BP. Ice rafting occurred almost exclusively from icebergs after 10,200cal. years BP. The icebergs most probably originated from tidewater glaciers on east Spitsbergen, indicating the presence of a strong east–west temperature gradient at this time. An increase of iceberg rafting around 9000cal. years BP, followed by enhanced sea-ice rafting, reflects the onset of a general cooling in the western Barents Sea–Svalbard region. Comparatively intense rafting from icebergs and sea ice between 9000 and 4000cal. years BP is related to this cooling. A general reduction in ice rafting after 4000cal. years BP is most probably the result of the enhanced formation of shore-fast and/or more permanent sea-ice cover, reducing the drift of icebergs and sea ice in the fjord. The results indicate that the palaeoenvironmental conditions on central Spitsbergen to a large degree depended on the oceanographic conditions in the western Barents Sea and west off Spitsbergen. However, climatic trends affecting Greenland and the entire north Atlantic region can also be identified. [Copyright &y& Elsevier]

The basal erosion rate and sediment yield of the Vestfjorden paleo-ice stream, a marine-based part of the northwestern Fennoscandian Ice Sheet, were elucidated during a complete advance-retreat cycle using high-resolution seismic data and multibeam bathymetry. In most of the area, there is a semitransparent, continuous upper seismic unit showing a southwestward (downfjord) progradational pattern with megascale glacial lineations on top, interpreted to represent a subglacial deformable till. The till formed a continuous bed beneath most of the Vestfjorden paleo-ice stream, except for the upstream parts, where ice streaming is inferred to have occurred above bedrock. The till thickness is up to an order of magnitude larger than those reported from modern ice streams due to a more efficient transfer of material from the source area to the ice streambed. The till is draped by glaciomarine and marine sediments. The average sedimentation rate in the paleo-ice stream drainage route during the period from ca. 35 to 11 ka was ∼2.6 m/k.y. This equals an average sediment discharge of 35 x 106 t/yr and an average sediment yield of 6.4 x 103 t km-2 yr-1. From this, we estimate an average erosion depth of ∼40 m or rate of ∼1.7 mm/yr in the sediment source area, the encircling fjord, and valley landscape. These values are in agreement with the results reported from similar settings in southern Norway, but they are nearly twice the figures reported for arctic ice-stream erosion. They are also significantly higher than the rates estimated from the British Ice Sheet. In conclusion, glacial erosion beneath paleo ice streams seems to have been more efficient in subarctic regions. [ABSTRACT FROM AUTHOR]

Aim To obtain palaeobotanical evidence enabling evaluation of the viability of the hypothesis that the ‘oriental’ element of the Balkan flora reached south-east Europe from Turkey prior to the Holocene, probably via the Thracian Plain during a late Quaternary glacial stage but no later than the late Weichselian. Location Ezero wetland, northern Thracian Plain, Bulgaria. Methods We undertook analyses of pollen and microspores, plant macrofossils, wood fragments and molluscs recovered from sediments deposited in the Ezero wetland during the late Weichselian and Weichselian late-glacial. Sediment chronology was determined using radiocarbon age estimates. Results Six metres of sediments were recovered from the basin, of which the lower 3 m, extending from c. 15,450 cal yr bp to the early Allerød, was analysed. A major hiatus occurred after c. 13,900 cal yr bp, the overlying sediments being of late Holocene age. Palaeobotanical evidence indicates predominantly open vegetation during the Weichselian late-glacial, although macrofossil remains of woody taxa demonstrate the local presence of patches of wooded steppe and gallery forest. Changes in the composition of the steppe vegetation, and in the nature of the sediments deposited in the basin, indicate changes in climatic conditions, especially in the hydrological regime and in the moisture available to vegetation. After an initially relatively moister phase, the final centuries of the late Weichselian were drier, as was a short interval that may correlate with the Older Dryas. Moister conditions characterize intervals corresponding to the Bølling and Allerød sub-units of the Weichselian late-glacial interstadial. Although the pollen evidence is thus consistent with that from previous studies of this period in south-east Europe and south-west Asia, indicating predominantly open steppe vegetation, the macrofossil evidence indicates the persistent local presence of woody taxa. The woody taxa recorded include Celtis tournefortii-type and Juniperus cf. J. excelsa, two taxa today characteristic of the wooded steppes of Anatolia and members of the ‘oriental’ element of the southern Balkan flora, as well as Rosaceae Subfams. Maloideae and Prunoideae, Alnus and Fraxinus. Main conclusions The late Weichselian vegetation of the northern Thracian Plain included patches of wooded steppe that supported members of the ‘oriental’ element of the modern Balkan flora. The presence of such taxa renders viable the hypothesis that they could have reached south-east Europe from Turkey via the Thracian Plain during glacial times. Such hypotheses in historical biogeography can be evaluated critically using the evidence obtained from plant macrofossil analyses in combination with that from pollen analysis. [ABSTRACT FROM AUTHOR]

The article offers a look on the post-glacial development of four small river-lake systems in the Weichselian belt of northern central Europe. The valleys where the investigation were done are part of immature drainage systems which usually and abruptly change in flow direction and had stagnant-ice depressions in the valley course. The study revealed that the valleys recycle segments of former subglacial meltwater channels which carried meltwater streams during the course of Late Pleniglacial period. Stagnant-ice melting existed in various stages from the Oldest Dryas to the early Holocene which was usually followed by the formation of lakes in the valley course. It was said that such phases signify that slight catastrophic events is significant in triggering geomorphic changes.

Abstract: Glacial sediments of the western Scottish Highlands are comprehensively described and characterized here for the first time, enabling the first glacial stratigraphy for the area to be proposed. This classification is based on the results of extensive geological mapping and field investigation of sedimentary sequences and their structures, X-ray diffraction and particle size distribution analyses, and comparison with deposits formed in contemporary glaciated environments. These new data are subsequently appraised in terms of their implications for late Pleistocene glacier evolution and dynamics. Together, the data suggest that much of the landscape is palimpsest, and can be attributed to the Weichselian (Late Devensian) glaciation. Subsequent glacier advance during the Younger Dryas did little to modify the area, suggesting that ice flow was dominated by sliding on a meltwater-lubricated rigid bed, with deformation of basal sediments playing a more limited role. Final deglaciation was marked by a significant increase in basal meltwater flux, reflecting the warming climate and increasing precipitation. These new palaeoglaciological and palaeoenvironmental insights advance our understanding of former glacier dynamics in the western Scottish Highlands, improve our knowledge of Pleistocene landscape evolution of this area, and enable comparisons to be made with sedimentary sequences elsewhere. [Copyright &y& Elsevier]

We studied the water-level changes and palaeogeography of Late Weichselian proglacial lakes in eastern Estonia using the shoreline and sediment distribution proxies from the Saadjärve Drumlin Field area together with the geomorphological correlation and GIS-based palaeoreconstructions. Our results show that about 14.0–13.8 cal. kyr BP Glacial Lake Peipsi inundated large areas of the Saadjärve Drumlin Field, Emajõgi River valley and reached the Lake Võrtsjärv basin. In the Saadjärve Drumlin Field area this is reflected in the formation of the highest shoreline and the corresponding rather short period (up to 63 years) of varved clay accumulation. The highest shoreline determined in the Saadjärve Drumlin Field is correlated with the valley terraces in southeastern Estonia, which reflect the water level in Glacial Lake Peipsi and the proglacial lake in the Võrtsjärv basin. The study suggests settling of glacial varved clay in the deepest inter-drumlin basins at the critical (minimal) water depths of about 15–20 m. The proglacial conditions lasted in the Saadjärve Drumlin Field for about 150 years and were interrupted due to the isolation of the lakes from proglacial bodies of water in the Peipsi and Võrtsjärv basins after the formation of the second highest shoreline. In the bottom sediments this isolation is marked by the transition from the laminated sediments to the massive silt interval. The results show that about 14.0–13.8 cal. kyr BP the connection route between Glacial Lake Peipsi and proglacial Lake Strenči, northern Latvia, shifted from the Võhandu—Hargla valley to the Väike-Emajõgi valley and the strait between Glacial Lake Peipsi and large Lake Privalday in northwestern Russia was closed. [ABSTRACT FROM AUTHOR]

Five sediment cores, up to 5.3 m long, taken in 2004 from the north-eastern part of the Gulf of Riga, were studied in order to support interpretations of acoustic profiles. The acoustic profiles, altogether 1000 km long, were recorded using mud-penetrating ecosounder at 4 kHz. The sequence of Late Weichselian and Holocene deposits was subdivided into nine sediment layers, which correspond to six acoustically different zones in acoustic profiles. A transitional lithologic boundary on top of rhythmic couplets of the Baltic Ice Lake clay and silt, together with two sharp disconformities levels that occur below and above a homogeneous brownish grey clay, are the most distinct surfaces in acoustic profiles. The maximum thickness of nine sediment layers above the Late Weichselian till is 8,6 m. [ABSTRACT FROM AUTHOR]

Abstract: Twenty-two sediment cores raised from the central and eastern parts of the Barents Sea have been studied to reconstruct the evolution of the facies system since the Late Weichselian glaciation. Multiproxy records reveal four lithostratigraphic units, which reflect major development stages of paleoenvironments. Age control is provided by 23 AMS 14C dates for Holocene sections of four cores. Continental moraine deposits of the last glaciation are overlain by proximal glaciomarine facies of the initial deglaciation phase. During this phase, the Barents Sea ice sheet detached from the ground resulting in seawater penetration into troughs, iceberg calving, deposition of IRD and fine-grained glacier meltwater load in newly formed marine basins. The main deglaciation phase is characterized by pulsed sedimentation from various gravity flows resulting in accumulation of distal glaciomarine facies comprising laminated clay and sand sequences with minor IRD. Redistribution of fine-grained suspended matter by bottom currents and brine-induced nepheloid flows combined with biogenic processes and minor ice rafting caused facies diversity of the Holocene marine sediments. The Holocene facies of shelf depressions reflect rather high, but variable productivity responding to climate changes and variations of Atlantic water inflow into the Barents Sea. [Copyright &y& Elsevier]

An 8.40 m long sediment sequence from the Salziger See basin, Central Germany, was investigated by a multi-disciplinary approach including chronological, sedimentological, geo- and biogeochemical methods. Radiocarbon dating, conducted on ten samples of aquatic and terrestrial fossil remains, and the occurrence of the Laacher See Tephra (LST) reveal that the sediment sequence comprises the Late Glacial and Holocene lake history since ca. 13,800 cal. year BP. This onset of lacustrine sedimentation is almost 7,000 years earlier as assumed so far. The geo- and biogeochemical data indicate distinct variations throughout the Late Glacial, which can be correlated with cold and warm periods, such as the Oldest Dryas, the Bølling, the Allerød, and the Younger Dryas. During most of the Holocene, minor variations in the geo- and biogeochemical data and a high carbonate content due to the formation and precipitation of autochthonous carbonate in the lake indicate relatively stable lacustrine conditions. A slight change in the sedimentary conditions between 6,700 and 4,000 cal. year BP, with lower deposition of carbonate and fine material, can be traced back to enhanced subrosion in the basin. Increased deposition of coarser sediments and a high accumulation of heavy metals document intensive human activity in the region during the past ca. 1,000 years. [ABSTRACT FROM AUTHOR]

Pleistocene chronostratigraphy in Estonia is based on 60 radiocarbon (14C, 14C AMS), 63 TL/OSL, and 17 10Be datings from 57 studied sites/sections that cover a time span from approximately 200 000 yr BP to the Pleistocene-Holocene chronostratigraphic boundary. For the first time all scattered data from 40 years of chronological study into Estonian Pleistocene are presented together and critically analysed in regard to validity of obtained ages. Half of the relatively abundant but scattered chronological data cover only the youngest 5000-6000 year part of the Late Weichselian. New OSL datings, together with the results of earlier palynological, carpological, and diatom studies, have invalidated almost one-third of the available 14C dates, obtained mostly in the late 1960s and 1970s. Thermoluminescence ages from tills, available from the early 1980s, are very inconsistent within the studied sections and are considered to be unreliable because of questionable bleaching of the it signal. The results of the 10Be method, recently applied to the study of deglaciation chronology of the Estonian territory, do not contradict the earlier age estimations. However, due to relatively large uncertainties of the method, the results were not able to refine the existing Late-Glacial chronology in Estonia. [ABSTRACT FROM AUTHOR]

Abstract: The late Weichselian Nyk Slide offshore northern Norway was investigated using high resolution seismic data, side-scan sonar imagery, and gravity cores. The mapable extent of the slide is ∼2200 km2, but parts of the slide were buried by glacigenic debris flows, and parts were removed by the younger Trænadjupet Slide. The exposed parts of the Nyk Slide exhibit extensional and, somewhat anomalously, compressional ridges in the upper slide area. We suggest that the two distinct morphologic zones originate from the same slide event. The compressional ridges are related to a particular large-scale funnel-shape morphology defined by the Vøring Plateau slope facing the continental slope, and were generated as the slide reached the foot of the Vøring Plateau slope. The extensional ridges were generated on the continental slope as sediments were transported downslope and subjected to stretching. Dating of the slide deposits indicate an age of ≥16.3 ka BP, synchronous with a time that the Fennoscandian Ice Sheet was fluctuating near the shelf edge. Nearby sediment cores and seismic reflection data reveal that the slide was both preceded and succeeded by episodes of deposition of glacigenic debris flows. The glide plane is located within the same unit of contouritic sediments as the glide plane of the Trænadjupet Slide, and the Nyk Slide, was probably triggered by loading and unloading of a fluctuating ice-front. The full extent of the slide is yet unknown, but the existing data suggest that the headwall continues upslope and follows the shelf edge outside the Trænadjupet Trough, implying that the Nyk Slide influenced an area substantially larger than the exposed slide deposits. [Copyright &y& Elsevier]

The most extensive systems of submarine channels on the continental margins of the Norwegian–Greenland Sea occur in the Greenland Basin (72–75°N). Geophysical records show that these channels are up to 100-m deep, 4-km wide, and extend for about 300 km from the middle continental slope off Northeast Greenland to the abyssal depths of the basin. Mass-wasting deposits in the form of debris flows and turbidity currents, as well as hemipelagic sediments, dominate sediment cores recovered from the channels. Radiocarbon dates indicate that debris flow and turbidity current activity in the channels had ceased by 13,000 years BP and sedimentation rates show a corresponding order of magnitude decrease after this time. Mass-wasting in the submarine channels of the Greenland Basin therefore relates to full-glacial and deglacial conditions. This implies a more extensive Late Weichselian ice sheet in Northeast Greenland than traditionally thought. The ice sheet extended onto the outer continental shelf and may have reached the shelf edge, delivering debris and sediment-laden meltwater onto the upper slope. Channel formation is most likely the product of turbidity-current activity during successive glaciations of the Northeast Greenland continental shelf. Holocene sediments from the channel systems are predominantly of hemipelagic origin and formed in a low energy, ice distal environment. The low gradient (<1°) channels of the Greenland Basin are therefore a glacially influenced sedimentary system. Contrasts in slope morphology and sediment architecture between the Greenland Basin and trough-mouth fans elsewhere in the Norwegian–Greenland Sea are not the result of variations in slope gradient. Rather, these contrasts reflect the interplay between bedrock lithology of the continental shelf, rates of sediment delivery, sediment texture, meltwater volume and relative size of ice-sheet drainage basins. [Copyright &y& Elsevier]