Late Pleistocene stratigraphy and sedimentary environments of the Severnaya Dvina‐Vychegda region in northwestern Russia

The Late Pleistocene stratigraphy from the Severnaya Dvina‐Vychegda region of northwestern Russia is revised based on investigations of new localities, revisiting earlier localities, introduction of about 110 new OSL dates and burial depth corrections of earlier published OSL dates, in addition to six new radiocarbon dates. Most of the OSL samples studied here are from fluvial and subaquaeous sediments, which we found to be well bleached. Six chronostratigraphical units and their sedimentary environment are described, with the oldest unit consisting of pre‐Eemian glacial beds. For the first time, Early Weichselian sediments are documented from the region and a fluvial environment with some vegetation and permafrost conditions is suggested to have persisted from the end of the Eemian until at least about 92 ka ago. The period in which a Middle Weichselian White Sea Lake could have existed is constrained to 67?62 ka, but as the lake level never reached the thresholds of the drainage basin, the lake probably existed only for a short interval within this time‐span. Blocking and reversal of fluvial drainage started again around 21?20 ka ago when the Fennoscandian Ice Sheet advanced into the area, reaching its maximum 17?15 ka ago. At that time, an ice‐dammed lake reached its maximum water level, which was around 135 m above present sea level. Drainage of the lake started shortly after 15 ka ago, and the lake was emptied within 700 years. Severe periglacial conditions, with permafrost and aeolian activity, prevailed in the area until about 10.7 ka.     

An OSL‐dated sediment sequence at Idre,west‐central Sweden,indicates ice‐free conditions in MIS 3

In central and northern Sweden, glacial sediments and landforms, formed during Early and Middle Weichselian stadials and their transition into interstadials, are often preserved in spite of having been overridden by later glacial advances. This study presents an OSL‐dated glacial stratigraphy from Idre in west‐central Sweden, expanding the area in which Middle Weichselian ice‐free conditions have been identified. Three sedimentary units were identified, with the lowermost unit consisting of glaciolacustrine sand, deposited in a stagnant water‐body. Nine OSL samples gave ages ranging from 54 to 41 ka, suggesting deposition during a deglacial phase in MIS 3. Normal faults and silt veins, formed after deposition, indicate that the area was ice‐free for a prolonged period, enabling the melting of buried stagnant ice. Above an erosional unconformity is a sediment unit characterized by gravels and sands deposited in a proximal braided‐river environment. OSL ages range from 180 to 41 ka, indicating poor sediment bleaching during deposition. We thus consider them to give a maximum age of the sedimentation, indicating deposition at or after 41 ka. The uppermost unit consists of a stacked succession of subglacial traction tills and glaciotectonite beds, representing the Late Weichselian glaciation of the area, probably during the inception phase with a wet‐based glacier regime. At the last deglaciation of the area there was extensive meltwater erosion, eroding all sedimentary units and forming a landscape with terraces and channels, and erosional remnants of the uppermost diamict as free‐standing hummocks.     

Lithostratigraphy and Optically Stimulated Luminescence age determinations of pre‐Late Weichselian deposits in the Suupohja area,western Finland

The lithostratigraphy of pre‐Late Weichselian sediments and OSL‐dating results from four localities in the Suupohja area of western Finland, adjacent to the centre of the former Scandinavian glaciations, are presented. The studied sections expose glacifluvial, quiet‐water, littoral and aeolian deposits overlain by Middle and/or Late Weichselian tills. Litho‐ and biostratigraphical results together with seven OSL age determinations on buried glacifluvial sediment at Rävåsen (94±15 ka) and on till‐covered littoral and aeolian sediments at Risåsen, Rävåsen, Jätinmäki and Kiviharju (79±10 to 54±8 ka), accompanied by previous datings and interpretations, suggest that the glacifluvial sediments at Risåsen were deposited at the end of the Saalian Stage (MIS 6) and those at Risåsen were deposited possibly in the Early Weichselian Substage (MIS 5d?). Palaeosol horizons and ice‐wedge casts together with the dated littoral and aeolian sediments between the Harrinkangas Formation (Saalian) and the overlying till(s) indicate that western Finland was ice‐free during most of the Weichselian time. Littoral deposits, dated to the Middle Weichselian (MIS 4–3), occur at altitudes of 50–90 m a.s.l., which indicates significant glacio‐isostatic depression. The depression resulted from expansion of the ice sheet in the west of Finland at that time.     

Glaciotectonised Quaternary sediments at Cape Shpindler,Yugorski Peninsula,Arctic Russia: implications for glacial history,ice movements and Kara Sea Ice Sheet configuration

The coastal cliffs of Cape Shpindler, Yugorski Peninsula, Arctic Russia, occupy a key position for recording overriding ice sheets during past glaciations in the Kara Sea area, either from the Kara Sea shelf or the uplands of Yugorski Peninsula/Polar Urals. This study on Late Quaternary glacial stratigraphy and glaciotectonic structures of the Cape Shpindler coastal cliffs records two glacier advances and two ice‐free periods older than the Holocene. During interglacial conditions, a sequence of marine to fluvial sediments was deposited. This was followed by a glacial event when ice moved southwards from an ice‐divide over Novaya Zemlya and overrode and disturbed the interglacial sediments. After a second period of fluvial deposition, under interstadial or interglacial conditions, the area was again subject to glacial overriding, with the ice moving northwards from an inland ice divide. The age‐control suggests that the older glacial event could possibly belong to marine oxygen isotope stage (MOIS) 8, Drenthe (300–250 ka), and that the underlying interglacial sediments might be Holsteinian (>300 ka). One implication of this is that relict glacier ice, buried in sediments and incorporated into the permafrost, may survive several interglacial and interstadial events. The younger glacial event recognised in the Cape Shpindler sequence is interpreted to be of Early‐to‐Middle Weichselian age. It is suggested to correlate to a regional glaciation around 90 or 60 ka. The Cape Shpindler record suggests more complex glacial dynamics during that glaciation than can be explained by a concentric ice sheet located in the Kara Sea, as suggested by recent geological and model studies. Copyright © 2003 John Wiley & Sons, Ltd.     

A new Early–Middle Weichselian palaeoenvironmental record from a lacustrine sequence at Svirkanciai,Lithuania

The Middle Weichselian (OIS 4‐3) and the transition from Early to Middle Weichselian are the most problematic and disputed time intervals of the Late Pleistocene with regard to the palaeogeography of the Fennoscandian glaciations. The number of sites with sediments of Middle Weichselian age in the Baltic region is very limited. An extensive area (77 km²) of lacustrine sediments (sand, clay, silt with humus and interlayers of peat), under the relief‐forming Upper Weichselian till, was discovered in the vicinity of the Venta settlement, northwestern Lithuania, and named the Venta Palaeolacustrine Basin. The Svirkanciai outcrop (56°18′05″N, 22°53′00″E) (15 m in height) of this palaeobasin is composed of two sediment complexes of different genesis and age. The lower part consists of silt and very fine‐grained sand of lacustrine origin. According to palynological data, the lacustrine sediments accumulated under boreo‐arctic climatic conditions. The pollen records suggest that local vegetation was sparse forest with open areas. An Optically Stimulated Luminescence (OSL) date of the lacustrine sand yielded an age of >79±6 ka, which indicates that lacustrine conditions may have occurred during part of the Early Weichselian Odderade Interstadial (Jonionys 2). However, the palynological data from Svirkanciai suggest a Middle Weichselian age, possibly correlating with the Oerel Interstadial (Jonionys 3) 55 ka ago. No traces of early Middle Weichselian Schalkholz (Nemunas 2a) stadial glacial advance have been found in the Venta sections. This also suggests a Middle Weichselian age for the Svirkanciai lacustrine sediments.     

Recurrent interaction between the Norwegian Channel Ice Stream and terrestrial‐based ice across southwest Norway

The occurrence of till beds alternating with glaciomarine sediment spanning oxygen isotope stages 6 to 2, combined with morphological evidence, shows that the southwestern fringe of Norway was inundated by an ice stream flowing through the Norwegian Channel on at least four occasions, the last time being during the Late Weichselian maximum. All marine units are deglacial successions composed of muds with dropstones and diamictic intrabeds and a foraminiferal fauna characteristic of extreme glaciomarine environments. Land‐based ice, flowing at right angles to the flow direction of the ice stream, fed into the ice stream along an escarpment formed by erosion of the ice stream. Each time the ice stream wasted back, land‐based ice advanced into the area formerly occupied by the ice stream. During the last deglaciation of the ice stream (c. 15 ka BP), the advance of the land‐based ice occurred immediately upon ice stream retreat. As a result, the sea was prevented from inundating the upland areas, allowing most of the glacioisostatic readjustment to occur before the land‐based ice melted back at about 13 ka BP. This explains the low Late Weichselian sea levels in the area (10–20 m) compared with those of the Middle Weichselian and older sea‐level high stands (～200 m). Regional tectonic movements cannot explain the location of the observed marine successions. The highest sea level recorded (>200 m) is represented by glaciomarine sediments from the Sandnes interstadial (30–34 ka BP). Older interstadial marine sediments are found at somewhat lower levels, possibly as a result of subsequent glacial erosion in these deposits. Ice streams developed in the Norwegian Channel during three Weichselian time intervals. This seems to correspond to glacial episodes both to the south in Denmark and to the north on the coast of Norway, although correlations are somewhat hampered by insufficient dating control.     

OSL‐based chronostratigraphy of river terraces in mountainous areas,Dunajec basin,West Carpathians: a revision of the climatostratigraphical approach

The technique of optically stimulated luminescence (OSL) dating applied to fluvial sediments provided a geochronological framework of river terrace formation in the middle part of the Dunajec River basin – a reference area for studies of evolution of river valleys in the northern part of the Carpathians (West Carpathians). Fluvial sediments at 18–90 m above valley bottoms were dated in the valleys of the Dunajec River and one of its tributaries. The resulting ages range from 158.9±8.3 to 12.2±1.3 ka. This indicates that some of the terrace sediments were deposited much later than previously assumed on the grounds of a combined morphostratigraphical and climatostratigraphical approach. The OSL‐based chronostratigraphy of terrace formation consists of seven separate phases of fluvial aggradation, separated by periods of incision and lateral erosion. Some of the ages determined correspond to warm stages of the Pleistocene – Marine Isotope Stage 3 (MIS 3) and MIS 5 – demonstrating that some terraces were formed during interstadial or interglacial periods. The results provide a key for evaluating rates of neotectonic uplift, allowing us to decipher the response of a fluvial system to climate change within the context of the glacial–interglacial scheme.     

The Rautuvaara section,western Finnish Lapland,revisited – new age constraints indicate a complex Scandinavian Ice Sheet history in northern Fennoscandia during the Weichselian Stage

The Rautuvaara section in northern Finnish Lapland has been widely considered as the stratotype for the northern Fennoscandian late Middle and Late Pleistocene. It exposes four till units interbedded with sorted sediments resting on Precambrian bedrock. In order to shed light on the Scandinavian Ice Sheet (SIS) history and palaeoenvironmental evolution in northern Fennoscandia through time, a chronostratigraphical study was carried out at the Rautuvaara site. The succession was studied using sedimentological methods and different sand‐rich units between till units were dated using the Optical Stimulated Luminescence (OSL) method. The results obtained indicate that the whole sediment succession at Rautuvaara was deposited during the Weichselian Stage and there is no indication of older deposits. The SIS advanced across Finnish Lapland to adjacent areas to the east at least once during the Early Weichselian, twice during the Middle Weichselian (～MIS 4 and MIS 3) and once during the Late Weichselian substages. Glaciolacustrine sediments interbedded between the till units indicate that a glacial lake repeatedly existed after each deglacial phase. The results also suggest that there were two ice‐free intervals in northern Fennoscandia during the Middle Weichselian close to the SIS glaciation centre.     

Re‐dating the Pilgrimstad Interstadial with OSL: a warmer climate and a smaller ice sheet during the Swedish Middle Weichselian (MIS 3)?

Alexanderson, H., Johnsen, T. & Murray, A. S. 2009: Re‐dating the Pilgrimstad Interstadial with OSL: a warmer climate and a smaller ice sheet during the Swedish Middle Weichselian (MIS 3)? Boreas, 10.1111/j.1502‐3885.2009.00130.x. ISSN 0300‐9483. Pilgrimstad in central Sweden is an important locality for reconstructing environmental changes during the last glacial period (the Weichselian). Its central location has implications for the Scandinavian Ice Sheet as a whole. The site has been assigned an Early Weichselian age (marine isotope stage (MIS) 5 a/c; >74 ka), based on pollen stratigraphic correlations with type sections in continental Europe, but the few absolute dating attempts so far have given uncertain results. We re‐excavated the site and collected 10 samples for optically stimulated luminescence (OSL) dating from mineral‐ and organic‐rich sediments within the new Pilgrimstad section. Single aliquots of quartz were analysed using a post‐IR blue single aliquot regenerative‐dose (SAR) protocol. Dose recovery tests were satisfactory and OSL ages are internally consistent. All, except one from an underlying unit that is older, lie in the range 52–36 ka, which places the interstadial sediments in the Middle Weichselian (MIS 3); this is compatible with existing radiocarbon ages, including two measured with accelerator mass spectrometry (AMS). The mean of the OSL ages is 44±6 ka (n=9). The OSL ages cannot be assigned to the Early Weichselian for all reasonable adjustments to water content estimates and other parameters. The new ages suggest that climate was relatively mild and that the Scandinavian Ice Sheet was absent or restricted to the mountains for at least parts of MIS 3. These results are supported by other recent studies completed in Fennoscandia.     

A pre‐LGM sandur at Fiskarheden in NW Dalarna,central Sweden – sedimentology and glaciotectonic deformation

The Fiskarheden quarry, situated in NW Dalarna, central Sweden, reveals thick coarse‐grained sediments of Scott type facies association representing a sandur deposited in an ice‐proximal proglacial environment. Optically Stimulated Luminescence (OSL) dating of the sandur sediments suggests a pre‐Last Glacial Maximum (LGM) age. Most acquired ages are pre‐Saalian (>200 ka) and we regard each of these ages to represent non/poorly bleached sediment except for one small‐aliquot OSL age of 98±6 ka. This age comes from the top surface of an arguably well‐bleached sand bed deposited on the lee‐side of a braid‐bar, putting the sandur build‐up into the Early Weichselian. Large‐scale glaciotectonic structures show an imbricate thrust fan involving both ductile and brittle deformation. The deformation was from the WNW, which largely coincides with the formative trend of the predominating streamlined terrain and Rogen moraine tracts surrounding Fiskarheden. It is suggested that the deformation of the sandur sediments took place when the advancing glacier approached and pushed its own proglacial outwash sediment, during an ice‐marginal oscillation either at the inception of one of the Early Weichselian glaciations in the area, or during a general ice retreat amid a deglacial phase. The Fiskarheden sandur deposits are covered by a subglacial traction till deposited from the NE/NNE. This direction corresponds with younger streamlined terrain flowsets cross‐cutting the older NNW–SSE system and probably represents deglaciation in the area following the LGM. This study will add to the understanding of the formation and deformation of Pleistocene sandur successions and their relationship to past ice‐sheet behaviour.     

Middle and Late Pleistocene fluvial systems in central Poland

This reconstruction of the fluvial palaeogeography of central Poland is based on an exhaustive and critical review of the published and archival data for the Middle and Late Pleistocene sediments of the area. The Warsaw Basin in central Poland was a major confluence area during the Middle and Late Pleistocene. The fluvial watersheds have been only slightly modified since that time. The past river systems resembled the contemporary one, therefore indicating rebuilding during successive interglacials, at least since the Holsteinian when the sea undoubtedly occupied the southern Baltic Basin. The Weichselian fluvial system was strongly influenced by the Scandinavian ice sheet, especially by meltwater runoff in the extraglacial area and ice-damming in the Warsaw Basin where a large proglacial lake developed. The Weichselian fluvial sediments form up to three terraces in the valleys of the Vistula and its tributaries. The most contentious issue is the mutual relation of the ice-dammed lake and ice marginal spillways in the Warsaw Basin, both being important fragments of a widespread drainage network in the Central European Lowland.     

Late Quaternary glacial history of the central west coast of Jameson Land, East Greenland

The Late Quaternary ( c . 130,000–10,000 BP) glacial history of the central west coast of Jameson Land, East Greenland, is reconstructed through glacial stratigraphical studies. Seven major sedimentary units are described and defined. They represent two interglacial events (where one is the Holocene). one interstadial event and two glacial events. The older interglacial event comprises marine and fluvial sediments, and is correlated to the Langelandselv interglacial, corresponding to oxygen isotope sub-stage 5e. It is followed by an Early Weichselian major glaciation during the Aucellaelv stade, and subsequently by an Early Weichselian interstadial marine and deltaic event (the Hugin Sø interstade). Sediments relating to the Middle Weichselian have not been recognized in the area. The Hugin Sø interstade deposits have been overrun by a Late Weichselian ice advance, during the Flakkerhuk stade, when the glacier, which probably was a thin, low gradient fjord glacier in Scoresby Sund, draped older sediments and landforms with a thin till. Subsequent to the final deglaciation, some time before 10,000BP, the sea reached the marine limit around 70 m a.s.l., and early Holocene marine, fluvial and littoral sediments were deposited in the coastal areas.     

Early Weichselian palaeoenvironments reconstructed from a mega-scale thrust-fault complex, Kanin Peninsula, northwestern Russia

A section, almost 20 km long and up to 80 m high, through alternating layers of diamict and sorted sediments is superbly exposed on the north coast of the Kanin Peninsula, northwestern Russia. The diamicts represent multiple glacial advances by the Barents Sea and the Kara Sea ice sheets during the Weichselian. The diamicts and stratigraphically older lacustrine, fluvial and shallow marine sediments have been thrust as nappes by the Barents Sea and Kara Sea ice sheets. Based on stratigraphic position, OSL dating, sea level information and pollen, it is evident that the sorted sediments were deposited in the Late Eemian-Early Weichselian. Sedimentation started in lake basins and continued in shallow marine embayments when the lakes opened to the sea. The observed transition from lacustrine to shallow marine sedimentation could represent coastal retreat during stable or rising sea level.     

Late Pleistocene fluvial dynamics in the Hochrhein Valley and in the Upper Rhine Graben: chronological frame

During the Pleistocene, the Rhine glacier system acted as a major south–north erosion and transport medium from the Swiss Alps into the Upper Rhine Graben, which has been the main sediment sink forming low angle debris fans. Only some aggradation resulted in the formation of terraces. Optically stimulated luminescence (OSL) and radiocarbon dating have been applied to set up a more reliable chronological frame of Late Pleistocene and Holocene fluvial activity in the western Hochrhein Valley and in the southern part of the Upper Rhine Graben. The stratigraphically oldest deposits exposed, a braided-river facies, yielded OSL age estimates ranging from 59.6 ± 6.2 to 33.1 ± 3.0 ka. The data set does not enable to distinguish between a linear age increase triggered by a continuous autocyclical aggradation or two (or more) age clusters, for example around 35 ka and around 55 ka, triggered by climate change, including stadial and interstadial periods (sensu Dansgaard–Oeschger cycles). The braided river facies is discontinuously (hiatus) covered by coarse-grained gravel-rich sediments deposited most likely during a single event or short-time period of major melt water discharge postdating the Last Glacial Maximum. OSL age estimates of fluvial and aeolian sediments from the above coarse-grained sediment layer are between 16.4 ± 0.8 and 10.6 ± 0.5 ka, and make a correlation with the Late Glacial period very likely. The youngest fluvial aggradation period correlates to the beginning of the Little Ice Age, as confirmed by OSL and radiocarbon ages.     

Age and extent of the Barents and Kara ice sheets in Northern Russia

The youngest ice marginal zone between the White Sea and the Ural mountains is the W-E trending belt of moraines called the Varsh-Indiga-Markhida-Harbei-Halmer-Sopkay, here called the Markhida line. Glacial elements show that it was deposited by the Kara Ice Sheet, and in the west, by the Barents Ice Sheet. The Markhida moraine overlies Eemian marine sediments, and is therefore of Weichselian age. Distal to the moraine are Eemian marine sediments and three Palaeolithic sites with many C-14 dates in the range 16-37 ka not covered by till, proving that it represents the maximum ice sheet extension during the Weichselian. The Late Weichselian ice limit of M. G. Grosswald is about 400 km (near the Urals more than 700 km) too far south. Shorelines of ice dammed Lake Komi, probably dammed by the ice sheet ending at the Markhida line, predate 37 ka. We conclude that the Markhida line is of Middle/Early Weichselian age, implying that no ice sheet reached this part of Northern Russia during the Late Weichselian. This age is supported by a series of C-14 and OSL dates inside the Markhida line all of >45 ka. Two moraine loops protrude south of the Markhida line; the Laya-Adzva and Rogavaya moraines. These moraines are covered by Lake Komi sediments, and many C-14 dates on mammoth bones inside the moraines are 26-37 ka. The morphology indicates that the moraines are of Weichselian age, but a Saalian age cannot be excluded. No post-glacial emerged marine shorelines are found along the Barents Sea coast north of the Markhida line.     

Middle Weichselian glacial event in the central part of the Scandinavian Ice Sheet recorded in the Hitura pit, Ostrobothnia, Finland

The Hitura open pit exposes a sedimentary sequence up to 50 m thick representing Late Saalian to Holocene glacial and non-glacial sediments. The sequence was investigated using sedimentological methods, OSL-dating and pollen and diatom analyses to reconstruct the Middle Weichselian (MWG) glacial event in the central part of the Scandinavian Ice Sheet (SIS). The results indicate that the sediment succession represents two entire glacial advance and retreat cycles. The lowermost deposits are Late Saalian esker and delta sediments overlain by sediments that correlate with the early Eemian lacustrine phase. Remnants of the Eemian soil post-dating the lacustrine phase were also observed. The area was ice-free during the entire Early Weichselian (EWG). The first glacial advance recorded in the sediments is related to the MWG. It started 79 kyr ago, deformed underlying sediments and deposited an immature till, including large detached sediment pods containing remains of organic material, soils and fluvial sediments representing allochthonous material from EWG ice-free stadials and interstadials. The glacial deposits are conformably overlain by glaciolacustrine and littoral accumulations, indicating MWG deglaciation between 62 and 55 kyr ago. Based on the fabric measurements from the till unit overlying the MWG sediments, ice advance during the Late Weichselian (LWG) was initially from the west and later from a north-northwesterly direction. The Hitura strata provide the first dating of the MWG deglaciation (55 to 62 kyr ago) from central parts of the SIS. It can be considered as a key site for studying the growth and decay of SIS during the poorly known early parts of the glaciation.     

Fluvial system response to Late Devensian (Weichselian) aridity,Baston, Lincolnshire,England

Little is known about the impact of Late Devensian (Weichselian) aridity on lowland British landscapes, largely because they lack the widespread coversand deposits of the adjacent continent. The concentration of large interformational ice‐wedge casts in the upper part of many Devensian fluvial sequences suggests that fluvial activity may have decreased considerably during this time. The development of optically stimulated luminescence (OSL) dating enables this period of ice‐wedge cast formation to be constrained for the first time in eastern England, where a marked horizon of ice‐wedge casts is found between two distinctive dateable facies associations. Contrasts between this horizon and adjacent sediments show clear changes in environment and fluvial system behaviour in response to changing water supply, in line with palaeontological evidence. In addition to providing chronological control on the period of ice‐wedge formation, the study shows good agreement of the radiocarbon and OSL dating techniques during the Middle and Late Devensian, with direct comparison of these techniques beyond 15 000 yr for the first time in Britain. It is suggested that aridity during the Late Devensian forced a significant decrease in fluvial activity compared with preceding and following periods, initiating a system with low peak flows and widespread permafrost development. Copyright © 2004 John Wiley & Sons, Ltd.     

Stratigraphy of a Late Pleistocene ice-cored moraine at Kap Herschell, Northeast Greenland

At Kap Herschell, in the outer fjord zone of central northeast Greenland, exposed sections in a Late Pleistocene ice-cored moraine revealed four major stratigraphic units deposited during the complex Kap Herschell Stade . All contain fragmented and redeposited marine shells that most likely belong to an Eemian or Early Weichselian marine episode. The oldest unit consists of buried ground ice with folded and sheared debris bands. Isotopic analyses show that the slope of the regression line for δ²H vs. δ¹⁸O of the ice is about 8.5. which suggests correlation with the Global Meteoric Water Line (GMWL). Data strongly suggest that the ground ice at Kap Herschell is a remnant of a Late Pleistocene glacier. It was probably generated at low altitudes (< 1000 m) in the inner fjord region or in the nunatak zone. The ground ice is unconformably overlain by all younger stratigraphic units, the oldest of which is a diamicton probably deposited as ablation till from the ice. A complex unit composed of mainly glaciolacustrine deposits and subordinate beds of fluvial and deltaic origin overlies the till and ground ice. Luminescence dating of the lacustrine sediments indicates maximum ages younger than 43 ka BP, suggesting deposition during isotope stages 3 or 2. The glaciolacustrine deposits suffered strongly from glaciotectonic deformation, caused by renewed glacier advance through the fjord. It reached the inner shelf and led to deposition of a discordant till at Kap Herschell, most probably during the Late Weichselian.     

The retreat of the Barents Sea Ice Sheet on the western Svalbard margin

The deglaciation of the continental shelf to the west of Spitsbergen and the main fjord, Isfjorden. is discussed based on sub-bottom seismic records and scdirncnt cores. The sea lloor on the shelf to the west of Isfjorden is underlain by less than 2 m of glaciomarine sediments over a firm diamicton interpreted as till. In central Isfjordcn up to 10 m of deglaciation sediments were recorded, whereas in cores from the innermost tributary, Billefjorden, less than a meter of ice proximal sediments was recognized between the till and the 'normal' Holocene marine sediments. We conclude that the Barents Sea Ice Sheet terminated along the shelf break during the Late Weichselian glacial maximum. Radiocarbon dates from thc glaciomarine sediments above the till indicate a stepwise deglaciation. Apparently the ice front rctrcatcd from the outermost shelf around 14. 8 ka A dramatic increase in the flux of line-grained glaciomarine sediments around 13 ka is assumed to reflect increased melting and/or current activity due to a climatic warming. This second stage of deglaciation was intcrruptcd by a glacial readvance culminating on the mid-shelf area shortly after 12.4 ka. The glacial readvance, which is correlated with a simultaneous readvance of the Fennoscundian ice sheet along the western coast of Norway, is attributed to the so-called 'Older Dryas' cooling event in the North Atlantic region. Following this glacial readvance the outer part of Isljorden became rapidly deglaciated around 12.3 ka. During the Younger Dryas the inner fjord branches were occupied by large outlet glaciers and possibly the ice liont terminated far out in the main fjord. The remnants of the Harcnts Sea Ice Shcet melted quickly away as a response to the Holocene warming around 10 ka.     

Age of the Pomeranian ice‐marginal position in northeastern Germany determined by Optically Stimulated Luminescence (OSL) dating of glaciofluvial sediments

Lüthgens, C., Böse, M. & Preusser, F. 2011: Age of the Pomeranian ice‐marginal position in northeastern Germany determined by Optically Stimulated Luminescence (OSL) dating of glaciofluvial sediments. Boreas, 10.1111/j.1502‐3885.2011.00211.x. ISSN 0300‐9843 The Pomeranian ice margin is one of the most prominent ice‐marginal features of the Weichselian glaciation in northern Europe. Previous results of surface‐exposure dating (SED) of this ice margin disagree with established chronologies and ice retreat patterns, i.e. are much younger than previously expected. We crosscheck the age of the Pomeranian ice‐marginal position in northeastern Germany using single‐grain quartz Optically Stimulated Luminescence (OSL) dating of glaciofluvial sediments. OSL dating indicates an active ice margin between 20.1±1.6 ka and 19.4±2.4 ka forming outwash plains attributed to the Pomeranian ice‐marginal position. On the basis of these results, we suggest a critical reassessment of previous SED data available for the Pomeranian ice‐marginal position within their respective regional geomorphological contexts. From a process‐based point of view, SED ages derived from glacigenic boulders document the stabilization of the landscape after melting of dead ice and landscape transformation under periglacial conditions rather than the presence of an ice margin. SED indicates a first phase of boulder stabilization at around 16.4±0.7 ka, followed by landscape stabilization within the area attributed to the recessional Gerswalder subphase around 15.2±0.5 ka. A final phase of accumulation of glaciolacustrine and glaciofluvial sediments at around 14.7±1.0 ka documents the melting of buried dead ice at that time.