bluuebunny/crossref_metadata_2025 huggingface dataset:
The Storegga tsunami along the Norwegian coast, its age and run up
Authors: BONDEVIK STEIN , SVENDSEN JOHN INGE , JOHNSEN GEIR , MANGERUD JAN , KALAND PETER EMIL
Published: July 2010

The statigraphy in 25 coastal lakes shows that most of the Norwegian coastline was impacted by a large tsunami about 7200 14C BP. The methodology has been to core a staircase of lake basins above the contemporary sea level in several areas and to map the tsunami deposit to its maximum elevation. The tsunami was identified in the sedimentary record as an erosional unconformity overlain by graded or massive sand with shell fragments, followed by redeposited organic detritus. The greatest recorded runup along the coast (10–11 m above high tide) is found in areas most proximal to the Storegga slide scar on the Norwegian continental slope (Sunnmøre). To the north and south, runup is less, about 6–7 m at Bjugn (250 km north of Sunnmøre) and about 3–5 m in Austrheim (200 km to the south of Sunnmerre). This runup pattern supports the suggestion that the tsunami was generated by the Second Storegga Slide. The recorded runup heights are consistent within and between the investigated areas, and imply that the tsunami wave was not significantly influenced by the local topography, suggesting a very long wave length. The mapped runup estimates are in good agreement with a numerical model of the tsunami generated by the Second Storegga slide, and indicate that the slide was a single major event rather than a set of smaller slides.
A mechanism for emplacement and concentration of diatoms in glacigenic deposits
Authors: BURCKLE LLOYD H. , KELLOGG DAVIDA E. , KELLOGG THOMAS B. , FASTOOK JAMES L.
Published: July 2010

The occurrence of diatoms (both marine and freshwater) in sediments beneath the West Antarctic Ice Sheet (WAIS) is suggestive of past ice‐sheet collapse. However, it is not the only model explaining such occurrences. We propose another mechanism for introducing diatoms beneath ice sheets by considering the fate of a diatom placed (by eolian processes) on top of an ice sheet. Mathematical modeling indicates that the route the diatom will take through the ice sheet is dictated by the basal melting rate. If no basal melting takes place, flowlines will crop out at the ice‐sheet margin. However, if basal melting is as low as 0.01 m/yr the trajectories of all Howlines except for those nearest the margin will intersect the bed, with those diatoms deposited near the dome reaching the bed about halfway down the Howband. Larger values of basal melting lead to the diatoms reaching the bed even faster and closer to the point of origin. In light of these results, the presence of diatoms in sediments beneath the WAIS does not lead to a unique solution; it is not necessary to invoke past ice‐sheet collapse to account for their presence.
Cirque glaciers as morphological evidence for a thin Younger Dryas ice sheet in east‐central southern Norway
Authors: DAHL SVEIN OLAF , NESJE ATLE , ØVSTEDAL JARL
Published: July 2010

Three localities with marginal moraines deposited by former cirque glaciers are investigated in east‐central southern Norway. The wet‐based (erosive) cirque glaciers with aspects towards S‐SW and N‐NE are mapped at altitudes above 1100 m, and have a mean equilibrium‐line altitude of 1275 m. With a suggested mean annual winter precipitation close to the average for the modern accumulation season (1 October‐30 April) when the cirque glaciers existed, the mean air‐temperature depression during the ablation season (1 May‐30 September) is calculated to be 6–7°C lower than at present. The high‐altitude cirques of central Rondane were still covered by ice when the low‐altitude cirque glaciers developed in distal position for this massif in eastern Rondane and on isolated mountains. Hence, the cirque glaciers are suggested to have existed during the deglaciation after the Late Weichselian maximum, and most likely during the Younger Dryas (11000–10000 BP). The cirque glaciers indicate a downwasting ice‐sheet surface well below an altitude of 1100 m prior to the Younger Dryas, and this supports a limited (small) vertical extent for the Late Weichselian ice sheet in this region. With the contemporaneous level for instantaneous glacierization (glaciation threshold) just below the highest elevated peaks in east‐central southern Norway, this fits with the idea of a continuous downwasting of the Late Weichselian ice sheet since the ‘first’ nunataks appeared. The occurrence of the cirque glaciers indicates a multidomed Scandinavian ice‐sheet geometry during the Late Weichselian.
The Late Devensian Lateglacial palaeoenvironmental record from Whitrig Bog, SE Scotland. 2. Chironomidae (Insecta: Diptera)
Authors: BROOKS STEPHEN J. , LOWE J. JOHN , MAYLE FRANCIS E.
Published: July 2010

Changes in chironomid midge larval assemblages in Lateglacial (c. 13.5–10 ka yr BP) lake sediments from Whitrig Bog are used to infer climatic (temperature) change. The earliest sediments contain few, predominantly cold stenothermic taxa. This fauna is replaced by an assemblage dominated by thermophilic taxa, indicating rising temperatures. The relatively warm Interstadial is punctuated by at least two brief cold oscillations which are characterized by the return of certain cold‐water taxa and the demise of some elements of the thermophilic fauna. The earlier of the two oscillations was apparently shorter and colder than the second. The highest Lateglacial Interstadial temperatures were attained either shortly before or after the first cold oscillation. This timing of the Lateglacial thermal maximum is apparently later than has been previously inferred from fossil beetle data. The Lateglacial Interstadial is terminated by the Loch Lomond (Young Dryas) Stadial, which is indicated in this monolith by an abrupt return of cold stenothermic Chironomidae and the virtual elimination of thermophilic taxa. Temperatures during the Younger Dryas appear to have been colder than during either of the previous minor cold oscillations. Climatic inferences from chironomid analysis broadly support and augment conclusions drawn from sediment chemistry and palynological evidence derived from the same monolith, although there is evidence that the vegetation and chironomid responses to early postglacial warming were out of phase.
Seismic facies and architecture of ice‐contact submarine fans in high‐relief fjords, Troms, Northern Norway
Authors: LYSÅ ASTRID , VORREN TORE O.
Published: July 2010

During the Late Weichselian, large marginal moraines were deposited in the Norwegian fjords. In Troms County these features are termed the Skarpnes and Tromsø‐Lyngen moraines, respectively, and have been mapped from land into the marine environment where they were formed as ice‐contact submarine fans. High‐resolution seismic data from several fjords have been studied and reveal a typical sediment thickness of 150–320 m for these ice‐contact systems. All of the ice‐contact submarine fans were formed under similar climatic conditions, but display wide variation in geometry, architecture and seismic pattern. This variation is related to differences in sediment supply, the nature of the subsurface of the fan (e.g. position of thresholds), basin geometry and basin depth. Based on interpretation of the different seismic facies and the architecture of the fans, former ice‐front positions have been suggested and a model has been presented for the formation of different types of ice‐contact submarine fans dependent upon variation in local basin condition.
The ice‐dammed lakes of Ossian Sarsfjellet (Svalbard): their geomorphology and significance
Authors: BENNETT MATTHEW R. , HAMBREY MICHAEL J. , HUDDART DAVID , GLASSER NEIL F. , CRAWFORD KEVIN
Published: July 2010

The tidewater glacier complex of Kongsvegen/Kronebreen, at the head of Kongsfjorden in north‐west Spitsbergen, has advanced rapidly several times since its Neoglacial maximum. Two such advances, 1869 and 1948, are well constrained in time and space and are widely interpreted as glacier surges. During the 1869 advance an ice‐dammed lake formed on the western side of Ossian Sarsfjellet. This ice‐dammed lake is associated with a thrust moraine complex. Four lake levels are identified, two of which are associated with rock‐cut shorelines implying a degree of lake stability. The history of this lake, the nature of the ice dam and its relationship to the thrust moraine complex are discussed. The lake history spanning 28 to 35 years is used to assess the ice‐marginal dynamics of the Kongsvegen/Kronebreen glacier. It is concluded that, contrary to previous suggestions, the rapid advance of this tidewater glacier may simply be an example of a non‐climatic ice‐marginal fluctuation, of the type common to tidewater glacier, as opposed to a glacier surge. A second ice‐dammed lake, to the east of Ossian Sarsfjellet, formed sometime after 1869 as the ice retreated, and still exists today. This largely supraglacial lake is associated with a very different geomorphological assemblage, which has a poor long‐term preservation potential. The geomorphological characteristics of the two lakes on Ossian Sarsfjellet are compared and used to discuss the problems associated with the recognition of ice‐dammed lakes within the Pleistocene record. On the basis of the evidence presented here, ice‐dammed lakes may be more common during deglaciation than currently suggested.
Origin and significance of calcareous concretions within glacial outwash in the Tempo Valley, north‐central Ireland
Authors: KNIGHT JASPER
Published: July 2010

In the Tempo Valley, north‐central Ireland, flat‐lying calcareous concretions are found within massive sand beds of glaciofluvial outwash which were deposited during the late Weichselian deglacial cycle. (c. 17 000 14 000 BP). Morphologically, concretions (< 20 cm long. I I cm wide, 3 cm thick) arc bladcd to disc‐shaped, lie parallel to sediment bedding planes, and have long axes aligned perpendicular to ice retreat direction. Internally, concretions are massive to framework‐supported and were formed as calcareous cements precipitated from solute‐rich groundwatcrs. Concretions, related to steep groundwater gradients and vigorous groundwater circulation cells, were formed proglacially at the base of a thin (1.5‐2.0 m deep) layer of discontinuous permafrost as meltwater was actively expelled from the retreating ice margin. The presence of a discontinuous permafrost substrate can also help explain regional‐scale geomorphic patterns indicating stagnation zone retreat of the Tempo Valley ice mass.
Long‐term Arctic peatland dynamics, vegetation and climate history of the Pur‐Taz region, Western Siberia
Authors: PETEET DOROTHY , ANDREEV ANDREI , BARDEEN WILLIAM , MISTRETTA FRANCESCA
Published: July 2010

Stratigraphic analyses of peat composition, LOI, pollen, spores, macrofossils, charcoal and AMS ages are used to reconstruct the peatland. vegetation and climatic dynamics in the Pur‐Taz region of western Siberia over 5000 years (9300‐4500 BP). Section stratigraphy shows many changes from shallow lake sediment to different combinations of forestcd or open sedge, moss, and Equisetum fen and peatland environments. Macrofossil and pollen data indicate that Larix sibirica and Beth pubescens trees were the first to arrive, followed by Picea obovata. The dominance of Picea macrofossils 6000‐5000 BP in the Pur‐Taz peatland along with regional Picea pollen maxima indicate warmer conditions and movement of the spruce treeline northward at this time. The decline of pollen and macrofossils from all of these tree species in uppermost peats suggests a change in the environment less favorable for their growth, perhaps cooler tempratures and/or less moisture. Of major significance is the evidence for old ages of the uppermost peats in this area of Siberia, suggesting a real lack of peat accumulation in recent millennia or recent oxidation of uppermost peat.
Deglaciation chronology and marine environments in southwestern Sweden
Authors: WASTEGARD STEFAN
Published: July 2010

Four sites in northwestern Dalsland and southwestern VHrmland, southwestern Sweden were investigated. including studies of marine biostratigraphy and AMS datings. A marine foraminifera and mollusc fauna existed in the area between c. 10 400 and 9700 14C years BP. Arctic assemblages dominate the lowermost layers, deposited immediately after the deglaciation. A transition to more diverse faunas affected by a higher meltwater influence and decreasing water depths is recorded higher up in the succession. Northwestern Dalsland was dcglaciated between c. 10 400 and 10 200 BP, and southwestern Viirmland between c. 10 100 and 9800 BP. A stagnation in the retreat of the ice margin is suggested at 10 300 to 10 200 BP. The subsequent rapid ice recession was probably an effect of warmer conditions at the Pleistocene‐Holocene climatic transition. A similar shift in the early Preboreal (c. 9900 BP) probably represents the dcglaciation which followed after the stagnation at the Ski moraines. Renewed glacial activity is indicated at c. 9700 BP.
Early Weichselian dust storm layer at Achenheim in Alsace, France
Authors: ROUSSEAU DENIS‐DIDIER , KUKLA GEORGE , ZÖLLER LUDWIG , HRADILOVA JANKA
Published: July 2010

The cause of the rapid transition from lush grasslands and woodlands of the Early Glacial interstadiul to Pleniglacial barrens in Europe is still a mystery. In the loess sections of Bohemia and Austria this transition is associated with thin layers of fine‐grained airborne dust known as ‘markers’, believed to be deposited by major contineiital‐scale dust storms. Here we present evidence that a similar. sharply delimited layer with a minimum TL age of 64.9 ± 6.9 ka separates the autochthonous humus steppe soils from abiogenic sediments of the Achenheim 1 pedocomplex in France. The soil complex has been previously correlated on pedostratigraphic grounds with marine oxygen isotope stage (MIS) 5. Given its age and stratigraphic position, the dust layer correlates with the PKII marker in Bohemia. The rccogiiition of a marker in Achenheim suggests that the development of the Early Glacial steppe soils ended abruptly not only in central Europe, but also in Alsace, France, prior to 65 ka, possibly as a result of a single continental‐scale dust storm.
An 800‐year long, radiocarbon‐dated varve chronology from south‐eastern Sweden
Authors: WOHLFARTH BARBARA , BJÖRCK SVANTE , POSSNERT GÖRAN , HOLMQUIST BJÖRN
Published: July 2010

More than 50 varve‐thickness diagrams, which were established from glacial varved clays in south‐eastern Sweden were correlated with each other to form an 800‐year long floating varve chronology. AMS |214|0C measurements on terrestrial macrofossils from the varved clays enabled synchronization of the record with other high‐resolution archives. The synchronization indicates that the chronology spans between c. 13 150 and c. 12 350 calendar years BP and covers the later part of the Allerørd and the early part of the Younger Dryas. Calibrated radiocarbon dates, which were obtained on varved clays south of the floating chronology, indicate that the ice recession in south‐eastern Sweden may have started during late Bølling. Our results indicate a longer time‐span in varve years for the deglaciation than has been previously estimated
Origin of Calcium carbonate granules found in buried soils and Quaternary deposits
Authors: CANTI MATTHEW
Published: July 2010

The ovoid calcium carbonate granules of less than 2 mm in size commonly found by molluscan specialists and soil micromorphologists are usually interpreted as coming from either earthworms or arionid slugs, or both. In this paper the granules are examined in detail, with a view to better understanding their origins and dynamics. Through collection and experiments, it is shown conclusively that both animals produce calcium carbonate granules of the right size range. The two types have distinctive morphologies, however, and most of the granules observed in soils and sediments are clearly identifiable as coming from earthworms. This arises from a far greater production rate: worms are capable of shedding granules at the rate of 1–3 per week, whereasArion ateronly yields around 40 granules < 250 μm on death. The granules survive digestive processes, so heavy predation of earthworms by various animals and birds means that there is a constant recycling of the granules in the biosphere.
New data from the Holsteinian interglacial site Öje, central Sweden
Authors: AMBROSIANI KARIN GARCIA , ROBERTSON ANN‐MARIE
Published: July 2010

The stratigraphy at Öje, central Sweden, has been reinvestigated. Till‐covered organic sediments were encountered in two out of three excavations, while in one excavation only till occurred. One sediment succession was analysed for pollen and macrofossils. The vegetation represented by both pollen and macrofossil flora indicates a correlation with (the latter) part of the Holsteinian Interglacial, also in accordance with the predominantly acidophilous diatom flora.
Quaternary records of the dire wolf,Canis dirus, in North and South America
Authors: DUNDAS ROBERT G.
Published: July 2010

The dire wolf was an important large, late Pleistocene predator in North and South America, well adapted to preying on megaherbivores. Geographically widespread,Canis dirusis reported from 136 localities in North America from Alberta, Canada, southward and from three localities in South America (Muaco, Venezuela; Talara, Peru; and Tarija, Bolivia). The species lived in a variety of environments, from forested mountains to open grasslands and plains ranging in elevation from sea level to 2255 m (7400 feet).Canis dirusis assigned to the Rancholabrean land mammal age of North America and the Lujanian land mammal age of South America and was among the many large carnivores and megaherbivores that became extinct in North and South America near the end of the Pleistocene Epoch.
Lateglacial environmental changes recorded in calcareous gyttja deposits at Gulickshof, southern Netherlands
Authors: HOEK WIM Z. , BOHNCKE SJOERD J. P. , GANSSEN GERALD M. , MEIJER TOM
Published: July 2010

Environmental changes were reconstructed from Lateglacial calcareous gyttja deposits at Gulickshof, southern Netherlands. Analyses of pollen, fresh‐water mollusca, stable isotopes and geo‐chemistry were performed and the combined evidence was put into a chronostratigraphic framework based on regional biostratigraphy and accelerator mass spectrometry radiocarbon dating. The pollen diagram showed vegetation development from the Bφlling interstadial into the Late Dryas stadial within 2.9 m of lacustrine deposits. Early in the Allerφd, around 11 900 BP, the composition of aquatic taxa and stable isotopes of calcium carbonate changed significantly. It appears that the final melting of relic ground‐ice and subsequent re‐establishment of the hydrological cell early in the Allerφd were responsible for these changes. Later in the Allerφd, around 11 250 BP, the disappearance of molluscs, changes in vegetation and isotope composition all point to colder climate conditions attributable to the Gerzensee oscillation. The combination of different lines of evidence in these types of deposits proves to be an excellent tool for unravelling climate and environmental signals.
Early Holocene shore‐displacement in southern central Sweden as recorded in elevated isolated basins
Authors: HEDENSTRÖM ANNA , RISBERG JAN
Published: July 2010

Sediment cores from seven basins in two regions, the SÖdertÖrn peninsula and central Närke in southern central Sweden, were subject to diatom analysis and radiocarbon dating of the isolation events. In the former area, the compiled shore‐displacement curve covers the time period from the deglaciation to 5700 BP. The latter area is covered from 8200 to 6500 BP. The chronology is based on combined macrofossil and bulk ages with an acknowledged correction. The most elevated sedimentary basin on the SÖdertÖrn peninsula was isolated at the end of the brackish water phase of the Yoldia Sea. During the Ancylus Lake stage of the Baltic, one minor ingression is recorded in the same area. The end of the Ancylus Lake is dated to c. 8200 BP on the SÖdertÖrn peninsula and to c. 8100 BP in central Närke. There was an interval of c. 1000 14C years when brackish water prevailed in central eastern Sweden. Mastogloia is a typical diatom genus for that period. The onset of the brackish‐marine Litorina Sea is dated to c. 7000 BP in central Närke. The amplitude for the early Litorina Sea transgression (L 1) did not exceed 2 m. L 1 is recorded 2–3 m higher in central Närke compared to the SÖdertÖrn peninsula, i.e. the former area has experienced a more intense isostatic uplift since 6500 BP.
Late Weichselian and Holocene environments of lake Endletvatn, Andφya, northern Norway: as evidenced primarily by chemostratigraphical data
Authors: VORREN KARL‐DAG , ALM TORBJφRN
Published: July 2010

A 6.5 m long sediment succession (18.5‐2.2 ka BP) from the northern sub‐basin of lake Endletvatn was analysed lithologically, palynologically and chemically. The chemical analyses were performed at about 10 cm depth intervals for the following parameters: total organic C, N, P, Fe, Mn, Mg, Na, K, Ca and S, in addition to water content, dry density, and pH. Two main lithostratigraphical units can be distinguished, which also differ substantially in chemical characters. Five chemostratigraphical main units were distinguished. The two lowermost units 1–2 (18.5–12.9 ka BP) correspond to the lower lithostratigraphical main unit and are characterized by minerogenous sediments with low C and N, and high Fe, Mg and K. P is low, partly because of a scarcity of P in parent rocks. Chemostratigraphical unit 3 (12.9‐9.6 ka BP) is characterized by increasing C and N and a high N/P ratio (10–20) culminating in the early part of the Younger Dryas, indicating abundant N available for bio‐production. The Fe, Mg, and K content is still high, but decreasing, indicating decreasing glacial and kryogenic erosion and allogenic deposition until c. 10.5 ka BP. A hiatus represented by a sand layer covers most of the time‐span 10.5–9.6 ka BP. Chemostratigraphical unit 4 (9.6‐5.3 ka BP) represents the Holocene thermal optimum in three subunits. In the time interval 9.6–9.1 ka BP, Fe, Mg and K decrease to a minimum and P shows a pronounced increase. The megathermal period c. 8200‐5300 BP, is characterized by maxima of C, N and P and a minimum of Fe. The katathermal period after 5.3 ka BP is characterized primarily by increased Fe precipitation, increasing Fe/Mn ratio, and P, C and N at a constantly lower level than during the megathermal. A stable C/N ratio of about 10, of the sediment interval younger than 12.9 ka BP characterizes the sediments as transitional between gyttja and dy. The Holocene lake type varied between weakly oligohumic and mesohumic. Stagnant bottom waters (reducing conditions) occur in the periods 12.9–11.5 ka BP and c. 7.5‐5.3 ka BP. The climatic development and other environmental implications of the joint chrono‐, chemo‐, litho‐and biostratigraphical data set are discussed.
Cordilleran Ice Sheet lobal interactions and glaciotectonic superposition through stadial maxima along a mountain front in southwestern British Columbia, Canada
Authors: HICOCK STEPHEN R. , LIAN OLAV B.
Published: July 2010

Glaciotectonic structures in subglacial till and substrate, as well as stone fabric, provenance and surface features in till, indicate that complex interactions of late Wisconsinan glacial lobes occurred along a mountain front in the western Fraser Lowland of southwestern British Columbia. Tills of this study represent subglacial deposition through the maxima of two stades in the Fraser Glaciation, the Coquitlam and the Vashon. Through each stadial maximum, temperate glacial ice was grounded and commonly overrode proglacial outwash while superimposing deformations in subglacial till during three phases: (1) pre‐maximum glacier flow down valleys and into lowland piedmont ice, (2) coalescent piedmont ice during stadial maxima when flow was westward along the mountain front and across valley mouths, and (3) post‐maximum glacier flow down valleys into lowland piedmont ice but prior to general deglaciation. Valley glaciers appear to have shifted flow directions during phases 1 and 3. During stadial maxima (phase 2), Fraser Lowland piedmont ice may have been part of an outlet glacier‐ice stream complex that terminated in salt water over the continental shelf.
Context of relict Wisconsinan glacial ice at Angus Lake, SW Banks Island, western Canadian Arctic and stratigraphic implications
Authors: WORSLEY PETER
Published: July 2010

Massive ice incorporating till beds and scattered erratic clasts exposed in a bimodal thaw slide displayed an association with the surrounding fluvioglacial and flow‐till facies indicative of a consanguineous relationship. The massive ice cores a low ridge interpreted as a recessional moraine feature paralleling the Last Glacial Maximum advance limit. Both ice and sand wedges penetrate the massive ice and their tops are truncated by a thaw unconformity overlain by a diamicton. In a permafrost environment, relict glacial ice can persist for many millennia, and the timing of the thaw is largely determined by the vagaries of erosional processes. The age of related kettle landforms can display considerable diachronism.
Devensian Lateglacial palaeoecological changes in Shetland
Authors: BIRNIE JACQUELINE F.
Published: July 2010

Diatoms and plant macrofossils in Devensian Lateglacial lacustrine sediments in Shetland suggest that the earliest response to interstadial warming was from benthic aquatic communities that could develop under lake ice. Further warming permitted longer ice‐free summers and plankton growth. The terrestrial vegetation communities responded more slowly. Pollen of land plants was then partly derived from long distance input. Macrofossils support a reconstruction of terrestrial vegetation of sparseSalix herbaceaand mosses in the early interstadial, increasing to grass tundra with tall herbs andEmpetrumlocally present, and with patches of disturbed ground. The occurrence ofBetulaandJuniperusremains questionable because of a lack of macrofossils, despite the presence of their pollen.Rumexpollen peaks suggest significant local presence at the stadial/interstadial transitions. Overall, the palaeoenvironmental reconstruction at this isolated oceanic site depends on several proxy indicators, of which pollen is less reliable than diatoms and plant macrofossils.
Late‐Holocene shore displacement of the Finnish south coast: diatom, litho‐ and chemostratigraphic evidence from three isolation basins
Authors: SEPPÄ HEIKKI , TIKKANEN MATTI , SHEMEIKKA PETRI
Published: July 2010

Lake isolation studies provide the most reliable method for reconstructing the shore displacement history of the areas affected by postglacial isostatic land uplift. Due to the slow uplift rate and the presence of numerous lakes, the Finnish south coast is one of the key areas for investigating the Litorina transgression and subsequent shore displacement history of the Baltic. To reconstruct the relative sea‐level dynamics during the late Holocene, three small lakes from the critical altitudes were analysed concerning their diatom, sulphate‐sulphur, and sodium stratigraphies and loss‐on‐ignition values. Comparisons of the records indicate that the availability of nutrients significantly influenced the diatom‐floristic patterns during the lake isolation. In particular, the mass occurrence of Fragilaria spp. seems to be associated with high values of sulphate‐sulphur and sodium during and after isolation. On the basis of the new and old data, a shore displacement curve for the 30m Litorina isobase is compiled. This indicates that since the clear Litorina transgression at 7500–6500 14C BP, no transgressions have taken place but that the shore displacement in the area has been a stable process. The occurrence of a number of raised shore formations between the altitude of the major Litorina shore and the present sea level in south Finland can be attributed to the erosion of soft soil layers by the high‐energy wave action on the exposed shore sections.
Late Devensian and Holocene depositional environments associated with the coversand around Caistor, north Lincolnshire, UK
Authors: BATEMAN MARK D. , MURTON JULIAN B. , CROWE WILLIAM
Published: July 2010

Sand deposits described at three sites near Caistor, north Lincolnshire (UK), provide a record of Late Devensian (Late Weichselian) to Holocene palaeoenvironments at the western margin of the European sand belt. Thermoluminescence (TL) and radiocarbon analyses provide for the first time a chronological framework for the demise of proglacial Lake Humber and the onset of coversand deposition. The reconstructed palaeoenvironmental history suggests that proglacial Lake Humber had receded from its initial high‐level stand before c. 18 ka, exposing the lake floor to periglacial conditions marked by the development of thermal contraction cracks. In the period between c. 18 and 14 ka, sand‐depositional processes changed from dominantly fluvial to aeolian. The fluvial activity was possibly a consequence of ameliorating winter climates between c. 17 and 16 ka. The aeolian coversand deposition in this period has not been previously recognized in Britain and correlates with the Older Coversand II and Younger Coversand I deposits elsewhere in the European sand belt. Peat accumulation followed during the Windermere (Bølling/Allerød) Interstadial and early part of the Loch Lomond Stadial (Younger Dryas) before regionally extensive coversand deposition took place in the later part of the Loch Lomond Stadial. This coversand correlates with the widespread Younger Coversand II deposits found both within the UK and across the European sand belt. The Holocene has been characterized by widespread stability with the development of soils on the coversand punctuated with periods of localized reworking through to the present day.
Coleoptera from the Late Weichselian deposits at Nørre Lyngby, Denmark and their bearing on palaeoecology, biogeography and palaeoclimate
Authors: COOPE GEOFFREY RUSSELL , BÖCHER JENS
Published: July 2010

The freshwater sediments exposed on the cliffs at Nørre Lyngby northern Jutland has long been a classical locality for the study of Danish Quaternary geology, palaeontology and archaeology. These deposits date from the latter part of the Allerød period (i.e. G I‐1). Samples for insect analysis have been taken from both the northern and southern exposures of these deposits. Ninety‐five‐ taxa of Coleoptera (beetles) were obtained, of which 69 could be named to species. Of the latter, 23 are not found living in Denmark today. Most of these are still living in northern Fennoscandia but one species is now confined to Mongolia. These assemblages have enabled a detailed picture of the local environment to be reconstructed, showing that the basin‐like profile of the deposits represents a section through a channel with slowly moving water. It has been possible to quantify the thermal climate of the time using the Mutual Climatic Range method indicating that mean July temperatures were about 10°C and mean January temperatures were about – 12°C. These figures are considered in the context of Lateglacial climatic reconstructions obtained from coleopteran assemblages elsewhere in northwestern Europe.
Holocene vegetation and climate changes in Hoton‐Nur basin, northwest Mongolia
Authors: TARASOV PAVEL , DOROFEYUK NADEZHDA , ‘TSEVA ELIZAVETA METEL
Published: July 2010

Radiocarbon‐dated pollen and diatom records from Hoton‐Nur lake (48°40'N, 88°18'E), northwest Mongolia are used to reconstruct Holocene vegetation and climate changes. Steppe, which covered the area some time before 9000 BP (all ages are given in 14C BP), was replaced by boreal conifer forest‐steppe by 9000–8500 BP. At the same time, planktonic diatoms increased in abundance from 5 to 45%. After 4000 BP there was a sharp reduction in forest and re‐establishment of steppe. Changes in the pollen composition were accompanied by a decrease in the abundance of planktonic diatoms from 35–50% (between 9000 and 5500 BP) to less than 10% soon after 4000 BP. These and other published data from Mongolia suggest wetter conditions during the early and middle Holocene than those of today. This pattern probably reflects an expansion of the Pacific monsoon recorded in geological data from China and simulated in climate‐model experiments, and suggests that the summer monsoon influenced a larger area than might appear if the Chinese records only are taken into consideration.
Micromorphological evidence supporting Late Weichselian glaciation of the Northern North Sea
Authors: CARR SIMON J. , HAFLIDASON HAFLIDI , SEJRUP HANS PETTER
Published: July 2010

Thirteen samples from three cores and boreholes are examined using micromorphology to test existing interpretations of Late Quaternary sedimentary sequences from the Norwegian Channel, North Sea Fan and the North Sea Plateau. Previous studies have interpreted these sediments using arbitrary parameters as reflecting Late Weichselian subglacial and glacimarine conditions associated with the Scandinavian Ice Sheet and Norwegian Channel ice stream. This study develops existing micromorphological criteria to interpret the samples as reflecting specific processes of subglacial deformation and proximal and distal glacimarine sedimentation during and subsequent to the Last Glacial Maximum. The study concludes by outlining diagnostic criteria for the identification of these sediment types from core and borehole samples of other Quaternary sediments.
Minor end moraines of the Wisconsin Valley Lobe, north‐central Wisconsin, USA
Authors: HAM NELSON R. , ATTIG JOHN W.
Published: July 2010

Approximately 35 parallel, discontinuous glacial ridges occur in an area of about 100 km2 in north‐central Wisconsin. The ridges are located between about 6 and 15 km north (formerly up‐ice) of the maximum extent of the Wisconsin Valley Lobe of the Laurentide Ice Sheet. The ridges are between 1 and 4 m high, up to 1 km long, and spaced between 30 and 80 m apart. They are typically asymmetrical with a steep proximal (ice‐contact) slope and gentle distal slope. The ridges are composed primarily of subglacial till on their proximal sides and glacial debris‐flow sediment on the distal sides. In some ridges the till and debris‐flow sediment are underlain by sorted sediment that was deformed in the former direction of ice flow. We interpret the ridges to be recessional moraines that formed as the Wisconsin Valley Lobe wasted back from its maximum extent, with each ridge having formed by a sequence of (1) pushing of sorted ice‐marginal sediment, (2) partial overriding by the glacier and deposition of subglacial till on the proximal side of the ridge, and (3) deposition of debris‐flow sediment on the distal side of the ridge after the frozen till at the crest of the ridge melted. The moraines are similar to annual recessional moraines described at several modern glaciers, especially the northern margin of Myrdalsjokull, Iceland. Thus, we believe the ridges probably formed as a result of minor winter advances of the ice margin during deglaciation. Based on this assumption, we calculate the net rate of ice‐surface lowering of the Wisconsin Valley Lobe during the period when the moraines formed. Various estimates of ice‐surface slope and rates of ice‐margin retreat yield a wide range of values for ice‐surface lowering (1.7–14.5 m/yr). Given that ablation rates must exceed those of ice‐surface lowering, this range of values suggests relatively high summer temperatures along the margin of the Wisconsin Valley Lobe when it began retreating from its maximum extent. In addition, the formation of annual moraines indicates that the glacier toe was thin, the ice surface was clean, and the ice margin experienced relatively cold winters.
Storegga tsunami deposits in a coastal lake on Suouroy, the Faroe Islands
Authors: GRAUERT MARIANNE , BJÖRCK SVANTE , BONDEVIK STEIN
Published: July 2010

Presumed deposits of the Storegga tsunami have been recognized in a coastal lake situated 4 m a.s.l. on the island of Suouroy, the Faroe Islands. The stratigraphy in the lake reveals a major erosion and redepositional event. The deposited material ranges from sand and sandy gyttja, with marine shell fragments and foraminifera, to gyttja with rip‐up clasts, wood fragments and thin sand layers. Diatom analysis indicates that the deposit contains 5–8% polyhalobous (full marine) species, decreasing to 1–2% in the undisturbed lacustrine gyttja above. The tsunami event was dated to some time between 7300 and 6400 14C yr BP. Lithostratigraphic profiles in the lake suggest that at least two large waves inundated the basin. The first and largest wave eroded most or all of the sediments previously deposited in the basin. The next wave caused minor erosion of the re‐deposited material. The waves deposited two generations of sand overlain by organic conglomerates, after which followed a unit of suspension material and normal lacustrine gyttja.
Formation and disintegration of a high‐arctic ice‐cored moraine complex, Scott Turnerbreen, Svalbard
Authors: SLETTEN KARI , LYSÅ ASTRID , LØNNE IDA
Published: July 2010

Englacial debris structures, morphology and sediment distribution at the frontal part and at the proglacial area of the Scott Turnerbreen glacier have been studied through fieldwork and aerial photograph interpretation. The main emphasis has been on processes controlling the morphological development of the proglacial area. Three types of supraglacial ridges have been related to different types of englacial debris bands. We suggest that the sediments were transported in thrusts, along flow lines and in englacial meltwater channels prior to, and during a surge in, the 1930s, before the glacier turned cold. Melting‐out of englacial debris and debris that flows down the glacier front has formed an isolating debris cover on the glacier surface, preventing further melting. As the glacier wasted, the stagnant, debris‐covered front became separated from the glacier and formed ice‐cored moraine ridges. Three moraine ridges were formed outside the present ice‐front. The further glacier wastage formed a low‐relief proglacial area with debris‐flow deposits resting directly on glacier ice. Melting of this buried ice initiated a second phase of slides and debris flows with a flow direction independent of the present glacier surface. The rapid disintegration of the proglacial morphology is mainly caused by slides and stream erosion that uncover buried ice and often cause sediments to be transported into the main river and out of the proglacial area. Inactive stream channels are probably one of the morphological elements that have the best potential for preservation in a wasting ice‐cored moraine complex and may indicate former ice‐front positions.
Late Saalian climate changes in Europe in the light of pollen analysis and the problem of two‐step deglaciation at the oxygen isotope stage 6/5e transition
Authors: BIK KRZYSZTOF , NITYCHORUK JERZY
Published: July 2010

Taking a palynological study from Dziewule in eastern Poland as an example, we discuss the problem of distinguishing the so‐called ‘Zeifen‐Kattegat oscillation’ in some European pollen profiles. In the light of pollen analysis, this is questionable, and therefore requires careful consideration. In Poland, the palynological succession from this period indicates a gradual evolution from open plant communities to a closed forest in which no record of a ‘Younger Dryas’ type cool event exists.
Palaeoenvironmental changes inferred from malacofaunas in the Lateglacial and early Holocene fluvial sequence at Conty, northern France
Authors: LIMONDIN‐LOZOUET NICOLE , ANTOINE PIERRE
Published: July 2010

Environmental changes are reconstructed from a Lateglacial and early Holocene sequence at Conty, northern France. The molluscan succession is put into a chronostratigraphic framework supported by numerous radiocarbon dates. Malacofaunas from the Bølling chronozone are reported for the first time in northern France and show progressive expansion of marshy communities within organic deposits. This biozone ended in a calcareous silt with the appearance of several species of arctic‐alpine affinities. These sedimentological and malacological data point to colder climatic conditions after 12 220 ± 90 BP, but before 11 640 ± 80 BP, allowing allocation to the Older Dryas event. The first part of the Allerød appears to have been drier and relatively stable. After 11 400 BP, a decline in species richness and diversity in the malacofaunas suggests increasing dryness. During the Younger Dryas, two molluscan biozones are identified in a homogeneous calcareous silt, reflecting an early wet phase followed by a drier episode. At the onset of the Holocene malacofaunas show a higher diversity, suggesting climatic improvement.
Quantification of SEM microtextures useful in sedimentary environmental discrimination
Authors: MAHANEY WILLIAM C. , STEWART ANDREW , KALM VOLLI
Published: July 2010

Scanning electron microscopic imagery is often used to identify and discriminate among environments of sedimentation with the main aim of identifying individual microfeatures, or suites of microtextures, that are considered indicative of a particular depositional environment or geologic process. Because few microtextures are considered to represent a single geologic process it is necessary to analyze a large number of quartz sands and other mineralic grains with the objective of determining the frequency of occurrence of a range of microtextures within a distinct sample suite. Using percent frequency of occurrence of different microtextures from suites of fluvial, glaciofluvial and glacial sands from sites in Estonia and Latvia, we invoked statistical comparison of different sample suites using Euclidean distances. These provide a quantitative means of measuring the differences among different sediments and processes that formed them and also a quantification tool useful
Late Weichselian pollen stratigraphy, clay varve chronology and palaeomagnetic secular variations in Lake Bolmen, Småland, south Sweden
Authors: ISING JONAS
Published: July 2010

Pollen analysis, glacial varve chronology and palaeomagnetic measurements were carried out on Late Weichselian lake sediments from southwestern Smaland, south Sweden. The sequence is correlated to the GRIP event stratigraphy, expressed in calendar years BP, and covers the period from the deglaciation at c. 14 400 to 11 300 calendar years BP. The series encompasses c. 930 varves and has been connected to the local varve chronology. Varve thickness increases markedly after the Older Dryas stadial, which indicates an accelerated deglaciation and melting of dead ice. The pollen diagram displays the vegetation development from the deglaciation at c. 14 400 calendar years BP to the transition to the Holocene. The vegetation succession starts with an arctic pioneer vegetation at the deglaciation, changes to a more stable tundra environment and displays a development which concurs with the traditional lateglacial pollen stratigraphy for southern Sweden. A palaeo‐magnetic secular variation curve is presented displaying two westerly declination swings at 14200‐13800 and 12 800‐11 600 calendar years BP, respectively. The upper one can be recognized from other palaeomagnetic stratigraphies from southern Sweden and Estonia.
Microstructures of sediment flow deposits and subglacial sediments: a comparison
Authors: LACHNIET MATTHEW S. , LARSON GRAHAME J. , LAWSON DANIEL E. , EVENSON EDWARD B. , ALLEY RICHARD B.
Published: July 2010

Microstructural analysis of glacial deposits has recently been used as a research tool to determine sediment genesis. However, the occurrence of microstructures in deposits of known origin has not been sufficiently documented, hindering our ability to confidently interpret microstructures in sediments of unknown origin. Our objective is to present a calibration study of microstructures of recent sediment flow deposits and associated sediments from the Matanuska Glacier, Alaska, and to evaluate the degree of commonality with micro‐structures found in subglacially deformed sediments. Microstructures in sediment flow deposits can be formed as a result of sediment transport, deposition, and/or post‐depositional processes, and are related to the viscosity regime of the source flow. Characteristic microstructures formed during brittle deformation include shears, faults, and brecciation; microstructures formed during ductile deformation include folds, pressure shadows, reorientation of clasts around a ‘core’ stone, fine laminations, basal shear zones, imbrication, and flow fabrics. Other microstructures include fluid escape and injection structures, clast haloes, and fissility. The results of our comparison suggest that sediment flow deposits share many microstructures in common with subglacially deformed sediments.
Mollusk record of millennial climate variability in the Loess Plateau during the Last Glacial Maximum
Authors: WU NAIQIN , LIU TUNGSHENG , LIU XIUPING , GU ZHAOYAN
Published: July 2010

A high‐resolution terrestrial mollusk record from the Loess Plateau of China has been studied to characterize climate variability during the Last Glacial Maximum (LGM). The rapid successions in mollusk taxa in the Weinan loess sequence reveal that climate changes occurred at least four times in this period. In the loess region, millennia‐scale climate fluctuations existed, as documented in the grain size and weathering intensity records. Our results show such millennia‐scale fluctuations reflecting changes in both temperature and precipitation, rather than a simple cold and warm alternation. Changes in temperature and precipitation were not in phase during the LGM. Temperature varied earlier than precipitation, which could have been the effect of winter and summer monsoon interactions. Our data also reveal that the East Asian summer monsoons could reach the southeast part of the Loess Plateau during the whole of the LGM. The intensification of winter monsoons during the LGM led to short duration of summer monsoons annually impacting on the Loess Plateau, but the intrinsic intensity of summer monsoons would not have changed significantly, thus providing the thermo‐hydrological conditions for temperate‐humidiphilou s mollusks to persistently grow and develop in the glacial age.