bluuebunny/crossref_metadata_2025 huggingface dataset:
A scanning system for measuring the age‐related luminescence of split sediment cores
Authors: POOLTON NIGEL R. J. , BØTTER‐JENSEN LARS , WINTLE ANN G. , YPMA PETER J. , KNUDSEN KAREN LUISE , MEJDAHL VAGN , MAUZ BARBARA , CHRISTIANSEN HENRIK E. , JAKOBSEN JØRGEN , JØRGENSEN FINN , WILLUMSEN FINN
Published: July 2010

This article describes the development and performance of an integrated optical sensor system that has been designed for rapid analysis of split sediment cores. The primary aim of the system is to obtain information based on optically stimulated luminescence (OSL) techniques; these provide a record of the accrued radiation dose of material since deposition. Particularly after suitable normalization, the luminescence signal recorded along the length of the core will provide information on the relative age of the sediment. Two wavelengths of stimulation are used (infra‐red and green) and these probe the feldspar, and combined feldspar and quartz components of the sediment respectively; the ratio of the two signals can thus provide some indication of relative changes in the silicate mineralogy. A secondary use of the system is for optical reflectance measurements. With the addition of a monochromator, optical reflectance spectroscopy can be applied to obtain additional information on down‐core mineralogical changes. In this article we describe technical aspects of the sensor system, discuss measurement techniques and consider the relevance of data obtained. Two examples of sediment cores are presented, which demonstrate the applicability of the instrument.
Holocene lateral expansion, peat growth and carbon accumulation on Haukkasuo, a raised bog in southeastern Finland
Authors: MÄUKILÄU MARKKU
Published: July 2010

Paludification intensity and peat deposition on Haukkasuo bog in southeastern Finland were studied with peat stratigraphic investigations by taking 79 samples for 14C carbon dating and 164 volumetric samples. Peat formation of Haukkasuo, a concentric raised bog, began about 10 400 cal. BP. Lateral expansion has been largely controlled by the flat clayey floor, which has favoured rapid growth of the bog. During the first 400 years of its existence the bog covered one‐fifth, and in the following 2000 years one‐half, of its present extent. The long‐term carbon accumulation rate averages 22.3 g C/m2/yr in the central part of Haukkasuo and 16.7 g C/m2/yr in its margins. The highest rates of carbon accumulation over 500‐year periods were recorded in the central part of the bog in 6500–5500, 3500–2500 and 1500–0 cal. BP. The rate of vertical peat increment was higher than average in these periods, and the peat was mainly slightly humified and, when close to the surface, un compacted. The rate of carbon accumulation was lowest in 5500–3500 and 2500–2000 cal. BP, when the rate of vertical growth was lower than average and the peat was more humified than average. The formation of peat, the rate of vertical peat increment and the succession of peat types in Haukkasuo have mainly been controlled by hydrological changes caused by local factors, although climatic factors might also be important. In particular, the formation of slightly humified peat in 3300–2700 cal. BP and during the last 1300 years can be related to humid climate.
Rapid climatic shifts of the northern Norwegian Sea during the last deglaciation and the Holocene
Authors: HALD MORTEN , ASPELI ROALD
Published: July 2010

High resolution cores from the upper continental slope, northern Norwegian Sea, document rapid climatic fluctuations during the latest deglaciation and the Holocene. Based on down‐core analysis of planktic and benthic foraminifera, stable oxygen and carbon isotopes, carbonate and organic carbon and radiocarbon dating, the following evolution is proposed: sea‐ice cover broke up, the surface ocean warmed and an in situ benthic foraminiferal fauna was established at 12 500 BP. The Younger Dryas was characterized by reduced sedimentaion and foraminiferal production, due to surface ocean cooling. At the end of the Younger Dryas there were major shifts in both surface and bottom water conditions. The surface ocean warmed to temperatures similar to modern levels within < 100 years, reaching a maximum at about 9200 BP when foraminiferal production was high. A benthic foraminiferal assemblage indicative of bottom water conditions similar to present conditions was established at 10 000 BP. This was followed by a gradual decline in nutrients or an increase in ventilation of the bottom water throughout the Holocene. A gradual surface ocean cooling of c. 2°C ended around 6500 BP followed by a second warming that culminated at 2000 BP. The warming at the end of the Younger Dryas and the succeeding older Holocene temperature maximum correlate to a June insolation maximum in the northern hemisphere. In addition, fluctuating surface temperatures in the Holocene may be driven by variations in inflow of Atlantic Water.
Luminescence evidence for two Middle Pleistocene interglacial events at Tourville, northwestern France
Authors: BALESCU SANDA , LAMOTHE MICHEL , LAUTRIDOU JEAN‐PIERRE
Published: July 2010

The infrared stimulated luminescence (IRSL) dating method is applied to alkali feldspar coarse grains from the two distinct Middle Pleistocene interglacial estuarine deposits of Tourville, located along the Seine Valley. The upper deposit (unit D), previously dated at 200 ka by ESR onin situshells and correlated with a stage 7 high sea‐level stand (186–245 ka), yields a measured IRSL age of 176 ± 21 ka. The lower deposit (unit B) assigned to a distinctly older high sea‐level event (stage 9: 303–339 ka) yields a measured IRSL age of 273 ± 28 ka. The nearby stage 7 raised beach of Sangatte, in Northwestern France, previously dated by TL on quartz (229 ± 18 ka) yields a measured IRSL age of 186 ± 19 ka. These IRSL age estimates systematically underestimate the expected geological ages. This could be due to the long‐term fading or instability of the luminescence signal in alkali feldspars. The correction for long‐term fading has been tested on these samples. At Tourville, it yields corrected IRSL ages of 196 ± 23ka and 314 ± 32ka, for the upper and lower units respectively and, at Sangatte, a corrected IRSL age of 206 ± 20 ka. These corrected IRSL age estimates are in better agreement with the expected geological ages. This study demonstrates the potential of the feldspar luminescence dating method to provide chronological information on Middle Pleistocene interglacial estuarine sediments within the North Sea‐English Channel Basin.
Structure and rhythmic pattern of glaciofluvial deposits north of Lake Vänern, south‐central Sweden
Authors: LUNDQVlST JAN
Published: July 2010

The glaciofluvial deposits of the Vanern plain, Värmland, form esker systems and trains. Esker trains are defined as series of short eskers, kames and other glaciofluvial deposits. Trains spreading fanlike from the same area are combined into esker systems. Some individual deposits are described. The general pattern differs from the long, coherent eskers typical of eastern Sweden. A rhythmic pattern of depositional units in the esker trains is found to correspond to a 10 to 11 yr cycle, possibly representing the sunspot cycle. Zones of alternating faster and slower retreat of the ice margin are identified. Two lines of slower retreat, the Karlstad and Fryken lines, correspond to the Norwegian Ski line, dated at 10 000 BP (conventional radiocarbon years) and to a slightly younger line. The spacing of the esker trains is controlled by topography in the north, but by basal ice melting, which controlled their flow and spacing on the Ratter terrain in the south.
Quantitative study of the distributary braidplain of the Preboreal ice‐contact Gardermoen delta complex, southeastern Norway
Authors: TUTTLE KEVIN J. , ØOUSTMO SVElN ROAR , ANDERSEN BJ ÖRN G.
Published: July 2010

This raised delta structure is an ice‐contact deltaic complex with a volume of c. 4.4.109 m3, deposited c. 9500 yr BP in a shallow wide ‘fjord’ during the retreat of the Scandinavian ice cap. The delta plain lies at an altitude of 200–223 m. It aggraded c. 20 m above the contemporaneous sea level during a regional marine regression. The braidplain palaeochannel characteristics indicate a peak meltwater discharge of 7–9 103 m3/s. Calculations based on a glacial ablation model indicate a mid‐summer discharge of c. 5.5 103 m3/s. However, the fluvial topset of the delta has an erosive base whose altitude decreases upstream and indicates stream incision by more the 6 m below the contemporaneous sea level. The deep scour is ascribed to episodic floods over the relatively short delta plain, which exceeded direct ablation‐associated discharges. The depositional time‐span of the delta is assessed to have been 70 years, calculated from coastal gradient and shoreline displacement curves. The average sedimentation rate of the delta is thereby inferred to have been extremely high, c. 6. 107 m3/yr. The sedimentation is thought to reflect ‘extreme’ ice‐margin conditions, where the sediment and water discharge was maximized by full‐scale ablation, with simultaneous subglacial, englacial and supraglacial sediment and water supply. These conditions might further coincide with an abundant rainfall in the catchment area or the drainage of dammed waters, initiating episodic floods which eroded deep beneath sea level. As a whole, the study illustrates the hydrological conditions of proglacial sedimentation at the front of the rapidly retreating last Scandinavian ice cap.
Dynamic sea‐level change during the last deglaciation of northern Iceland
Authors: RUNDGREN MATS , INGÓLFSSON ÓLAFUR , BJÖRCK SVANTE , JIANG HUI , HAFLIDASON HAFLIDI
Published: July 2010

Rundgren, M., Ingólfsson, Ó., Björck, S., Jiang, H. & Haflioason, H. 1997 (September): Dynamic sea‐level change during the last deglaciation of northern Iceland. Boreas, Vol. 26, pp. 201–215. Oslo. ISSN 0300–9483.

A detailed reconstruction of deglacial relative sea‐level changes at the northern coast of Iceland, based on the litho‐ and biostratigraphy of lake basins, indicates an overall fall in relative sea level of about 45 m between 11300 and 9100 BP, corresponding to an isostatic rebound of 77 m. The overall regression was interrupted by two minor transgressions during the late Younger Dryas and in early Preboreal, and these were probably caused by a combination of expansions of local ice caps and readvances of the Icelandic inland ice‐sheet margin. Maximum absolute uplift rates are recorded during the regressional phase between the two transgressions (10000–9850 BP), with a mean value of c. 15 cm 14C yr‐1 or 11–12 cm cal. yr‐1. Mean absolute uplift during the regressional phase following the second transgression (9700–9100 BP) was around 6 cm 14C yr‐1, corresponding to c. 3 cm cal. yr‐1, and relative sea level dropped below present‐day sea level at 9000 BP.
Pleistocene stratigraphy in the Dellen region, central Sweden
Authors: ROBERTSSON ANN‐MARIE , SVEDLUND JAN‐OLOV , ANDRÉN THOMAS , SUNDH MARTIN
Published: July 2010

Robertsson, A.‐M., Svedlund, J.‐O., Andrén, T. & Sundh, M. 1997 (September): Pleistocene stratigraphy in the Dellen region, central Sweden. Boreas, Vol. 26, pp. 237–260. Oslo. ISSN 0300–9483.

The Pleistocene stratigraphy in the Dellen region, central Sweden was studied using field observations made during mapping of Quaternary deposits and fabric analyses in excavated sections. The lithostratigraphy was also studied by seismic refraction measurements, analyses of grain‐size distribution and organic carbon content. Biostratigraphical methods applied were pollen and diatom analyses. A general outline of the Pleistocene stratigraphy in the area is presented. Three different till beds are identified, the lowermost suggested to have been deposited during the Saalian glaciation and the other two during the Weichselian glaciation. According to the interpretation of the stratigraphy, it is questioned whether the first Weichselian ice sheet did in fact reach the Dellen area. A clayey sediment sequence at Norra Sannas accumulated during an interglacial, probably the Eemian. Most of the interglacial vegetation succession is reflected in the identified pollen flora. An initial phase with a light‐demanding forest of Belula and Pinus was followed by immigration of Alnus, Picea and scattered occurrences of Corylus. A freshwater diatom flora was identified dominated by plankton taxa, e.g. Aulacoseira italica, A. distans and Cyclotella spp. In the lower part of the sequence a brackish‐marine flora was registered, representing accumulation in a bay of the Eemian Sea. Fine‐grained sediments at the Sundson and Vastansjd sites are interpreted as rebedded Eemian sediments according to the pollen flora. An (Early Weichselian) interstadial age is suggested for sediments found at Bjuraker. Dating by the 14C‐ and OSL methods was carried out on the interglacial and interstadial sediments, respectively. The ages range from approximately 19000 to 92000 BP. Correlation of interglacial vegetation history with central Finland and other areas is discussed.
The Late Devensian Lateglacial palaeoenvironmental record from Whitrig Bog, SE Scotland. 1. Lithostratigraphy, geochemistry and palaeobotany
Authors: MAYLE FRANCIS E. , LOWE JOHN J. , SHELDRICK CHARLES
Published: July 2010

This is the first of a series of articles presenting the results of a multi‐proxy investigation aimed at reconstructing changes in the ecosystem and climate of Whitrig Bog, SE Scotland, during the last glacial‐inter‐glacial transition (Devensian Lateglacial, c. 14–10 ka BP). We present here the results from sediment lithology, chemistry, pollen, and plant macrofossil analyses. These data are used to infer the nature of the local catchment soils and both local and regional terrestrial vegetation. The interstadial period (c. 13–11 ka BP) is characterized by a successional sequence developing from a landscape with bare, poorly developed minerogenic soils supporting a sparse herbaceous flora into open birch woodland with juniper scrub and stable organic soils. At c. 11 ka BP the Younger Dryas climatic cooling event caused an abrupt reversion to an open herbaceous arctic/alpine flora (e.g. macrofossil evidence of Silene furcata and Oxyria digyna) and high levels of minerogenic erosion into the basin, indicating environmental response to a cold Arctic climate. In addition to this Younger Dryas climatic reversal, two lesser reversion episodes occurred earlier during the interstadial. The more pronounced of the two, late in the intersladial, is characterized by high levels of erosion and a change from birch/juniper woodland to an open herbaceous flora. The older oscillation occurs approximately mid‐way through the interstadial sequence and is marked by similar pollen changes, albeit shorter lived and more subtle.
Dense‐media separation as a more efficient pollen extraction method for use with organic sediment/deposit samples: comparison with the conventional method
Authors: NAKAGAWA TAKESHI , BRUGIAPAGLIA ELISABETTA , DIGERFELDT GUNNAR , REILLE MAURICE , BEAULIEU JACQUES‐LOUIS DE , YASUDA YOSHINORI
Published: July 2010

Dense‐media separation, frequently adopted as a standard pollen extraction method for use with minerogenic sediment samples, was adapted for use with organic‐rich sediment and peat samples. A total of 15 organic‐rich sediment samples, obtained from sites in Corsica and the Southern European Alps, was treated using both dense‐media separation and the conventional preparation method in order to compare the relative efficiencies of the two methods. The dense‐media separation method consistently achieved a remarkably higher purity of extracted pollen grains. This was especially true for the Corsican peat samples, the dense‐media separations being quite pure, whereas the classical method produced samples that were so severely polluted with organic fragments that it was impossible to carry out a satisfactory pollen analysis. The percentage values of each taxon were generally similar using both methods, showing that the two methods are compatible for pollen analytical studies. Total pollen concentrations were generally higher with the dense‐media separation method (especially for gyttja samples). In conclusion, dense‐media separation is an efficient method for pollen extraction from organic as well as from minerogenic sediments and deposits.
Genesis of hummocky moraine in the Bolmen area, southwestern Sweden
Authors: ANDERSSON GUNNAR
Published: July 2010

During the late Weichselian deglaciation of southern Scandinavia vast areas of hummocky moraine were formed. The genesis of this landform was studied by geomorphological and sedimentological methods in an area in southwestern Sweden. Four exposures in moraine hummocks were investigated using sedimentological methods. They were found to be composed of stratified diamictons with frost‐shattered boulders and deformed intrabeds of sorted sediments. The diamictons were interpreted as sediment‐flow deposits, with the hummocks formed in stagnant ice by flowage of supraglacial glacial debris into depressions and subsequent inversion of the landscape due to ice melt. With the exception of hummocky moraine, the study area contains low relief moraine, which like the hummocky moraine was supraglacially formed. A new model is presented where the distribution of hummocky and low relief moraine is dependent on the vertical distribution of glacial debris in the ice sheet, which in turn is related to the flow regime of the ice sheet prior to stagnation. A compressive flow before stagnation favoured development of the hummocky moraine, while low relief moraine formation occurred where the ice flow was extending or at steady state.
Salinity and redox alternations in the northwestern Baltic proper during the late Holocene
Authors: SOHLENIUS GUSTAV , WESTMAN PER
Published: July 2010

Selected geochemical parameters and siliceous microfossil assemblages in Baltic Sea sediments are presented which reflect past variations in redox conditions, salinity and primary production. The sediments were deposited during the freshwater Ancylus Lake (9500‐8000 14C BP) and brackish Litorina Sea (8000‐3000 BP) stages of the Baltic. The diatom record shows that surface‐water salinity increased further at c. 7000‐6500 BP, although smaller amounts of brackish water entered the basin from c. 8000 BP onwards. Attempts to use exchangeable Mg as a palaeosalinity indictor were not applicable. Gross primary productivity increased along with salinity, which has been interpreted as an effect of nutrient enrichment in the photic zone. This led between c. 6500 and 4500 BP to a high accumulation of organic carbon, anoxic or nearly anoxic bottom conditions and formation of laminated deposits. Certain laminae consist of alternating layers of organic and minerogenic material and were probably formed annually, i.e. in the manner of varves. The laminated successions are distinguished by enrichments of V, Cu and especially Mo. The highest Mo content occurs in the core from the greatest water depth, an effect of anoxic conditions during deposition. The Fe/Mn ratio was shown to be ambiguous as an indicator of past redox conditions. Since biogenic silica shows large variablity in contemporaneously deposited sediments, this parameter cannot be used as a proxy for the past production of siliceous algae in the Baltic Sea.
A little goes a long way: discovery of a new mid‐Holocene tephra in Sweden
Authors: BOYGLE JANE
Published: July 2010

This pilper reports the presence of a volcanic ash layer in western Sweden which is geochemically identiticd as the Kebister tephra. This tephrdpresenceof (dated c. 3600 14C BP) was discovered at Kebister, Shetland and thc rcsults presented here indicate that the deposit may have a greater geographical distribution than previously thought. The geochemistry of the volcanic glass was analysed by using discrete grain electron probe microanalysis (EPMA). Thc SiO2 content of the glass ranges from 66.19 to 71.96%, FeO content 2.73 to 6.07% and MgO content 0.15 to 0.57%˜ The tephra can he distinguished from the more widespread Hekla 4 tephra (c. 3800 14C BP) on the basis of calcium and magnesium contents.
A reconstruction of Holocene climatic changes from peat bogs in north‐west Scotland
Authors: ANDERSON DAVID E.
Published: July 2010

Continuous palaeoenvironmental sequences from three peat bogs located in north‐west Scotland are presented which reveal palaeoclimatic changes during the Holocene, Peat cores were analysed lor humification. pollen and a range of other physical and palaeoecological data, and chronologies were constructed by radiocarbon dating. Reconstruction of past changes in bog hydrology formed the basis for palaeoclimatic interpretation. Four regional shifts to wetter bog conditions and two regional shifts to drier conditions are inferred. Best estimated aye ranges for the wet shifts spanc. 5120 to 5070, 4020 to 3630, 3340 to 3270 and 940 to 800 cal BP, arid dry shifts are estimated atc. 4330 to 4120 and 1480 to 1340 cal BP. The most distinctive feature of the record is the oscillation from wetter to drier conditions around 4300 cal BP, followed by a return to wetter conditions after 4000 cal BP. This oscillation was probably caused by climatic changes which also had an inHuence on the dynamics of Scots pine within the region prior to, and during, its mid‐Holocene phase of decline. Later shifts probably also reflect climatic changes, although evidence for human land‐use complicates interpretation atc. 3300 cal BP. Potential causes are considered, including changes in the circulation of the North Atlantic Ocean during the mid‐Holocene.
Active ice‐sheet deglaciation and ice‐dammed lakes in the northern Cairngorm Mountains, Scotland
Authors: BRAZIER VANESSA , KIRKBRIDE MARTIN P. , GORDON JOHN E.
Published: July 2010

Mapping of ice‐marginal and glaciolacustrine deposits in the northern Cairngorm Mountains allows the nature of deglaciation following the Last Glacial Maximum (c.18 000 BP) to be reinterpreted. Two ice‐dammed lakes were ponded between the Glenmore lobe of the Scottish ice sheet and local glaciers draining northwards from the Cairngorm Mountains. Delta progradation from the southern end of each lake reflects dominant meltwater sources and glacio‐hydrological gradients. Sediment facies representing subaqueous mass‐flow deposits, lakebottom rhythmites, lower and upper foresets and topsets are associated with prograding delta fronts. Moraines show that the lakes were ice dammed at both ends, evidence that active glaciers existed in the Cairngorm Mountains while ice was retreating from Strath Spey, and that deglaciation was punctuated by readvances of the ice margin. These results indicate that an ice‐stagnation model of deglaciation is invalid for most of the duration of ice wastage, but instead support an active‐retreat hypothesis with multiple, climatically forced readvances.
Late Quaternary environmental history of central Prins Karls Forland, western Svalbard
Authors: ANDERSSON TORBJÖRN , FORMAN STEVEN L. , INGÓLFSSON ÓLAFUR , MANLEY WILLIAM F.
Published: July 2010

This paper presents the results from stratigraphic and geomorphologic investigations in the Poolepynten area, Prins Karls Forland, western Svalbard. Field mapping, soil profile development and 14C dating reveal the existence of at least two generations of raised beach deposits. Well‐developed raised beaches rise to the Late Weichselian marine limit at 36 m a.s.l. Discontinuous pre‐Late Weichselian beach deposits rise from the Late Weichselian marine limit to approximately 65 m a.s.l. Expansion of local glaciers in the area during the Late Weichselian is indicated by a till that locally overlies pre‐Late Weichselian raised beach deposits. Stratigraphic data from coastal sections reveal two shallow marine units deposited during part of oxygen isotope stage 5. The two shallow marine units are separated by a subglacially deposited till that indicates an ice advance from Prins Karls Forland into the Forlandsundet basin some time during the latter part of stage 5. Discontinuous glaciofluvial deposits and a cobble‐boulder lag could relate to a Late Weichselian local glacial advance across the coastal site. Late Weichselian/early Holocene beach deposits cap the sedimentary succession. Palaeotemperature estimates derived from amino acid ratios in subfossil marine molluscs indicate that the area has not been submerged or covered by warm based glacier ice for significant periods of time during the time interval ca. 70 ka to 10 ka.
Soft‐bedded subglacial meltwater channel from the Welzow‐Süd opencast lignite mine, Lower Lusatia, eastern Germany
Authors: PIOTROWSKI JAN A. , GELETNEKY JÖRN , VATER RALF
Published: July 2010

An excellent section in the Welzow‐Süd open‐cast lignite mine in Lower Lusatia, eastern Germany, provided a rare opportunity to study a small (5 m deep), buried subglacial meltwater channel of Saalian age. The channel is steep‐sided and distinctly U‐shaped. It is separated from undeformed outwash deposits in which it is incised by a sharp erosional contact and it is filled with meltwater sand and till. The till was possibly squeezed into the channel from the adjacent ice/bed interface. Directly beneath the channel, there is a partly truncated diapir of clayey silt, evidencing sediment intrusion into the channel from below. During channel formation, the pressure gradient was oriented from the surrounding sediments into the channel, so that the channel served as a drainage conduit for groundwater from the adjacent subglacial aquifer. The substratum consists largely of sandy aquifers with a total thickness of about 100 m, separated by two aquitards. Channel formation was initiated when hydraulic transmissivity of the bed did not suffice to evacuate all the subglacial meltwater as groundwater flow. As the Welzow‐Süd channel belongs to a dense network of subglacial channels in eastern Germany, temporary ice‐sheet instability in this region prior to channel formation seems possible.
A data chart for field description and genetic interpretation of glacial diamicts and associated sediments…with examples from Greenland, Iceland, and Denmark
Authors: KRüGER JOHANNES , KJÆR KURT HENRIK
Published: July 2010

A data chart is presented for detailed field description of sediment successions containing glacial diamicts and associated sediments. The design is based on field experience from modern glacial environments in Greenland and Iceland and ancient deposits in Denmark. The data chart proposes an integrated scheme that provides a synthesis of existing approaches to sediment description in the field. Three examples of the use of the data chart and logging technique illustrate its wide variability in comparison with the limited sedimentology practised by many scientists working with ancient glacial diamicts. It is concluded that the data chart might be a useful approach for recognition of the various possible types of glacial diamicts, but it does not assume to be a complete approach; it is the object of continuing discussion and can be extended or modified.
Dinoflagellate cysts reflecting surface‐water conditions in Voldafjorden, western Norway during the last 11 300 years
Authors: GRφSFJELD KARI , LARSEN EILIV , SEJRUP HANS PETTER , VERNAL ANNE DE , FLATEBφ TROND , VESTBφ MONICA , HAFLIDASON HAFLIDI , AARSETH INGE
Published: July 2010

Abundant dinocysts in a high‐resolution core from Voldafjorden, western Norway, reflect changes in sea surface‐water conditions during the last c. 11 300 BP. The period from c. 11 300 to 10 800 BP (Late Allerφd) was characterized by cool temperate surface‐waters, high annual temperature variation and relatively strong stratification of the water column, which is characteristic of fjord environments. Due to the stratification of the surface waters, the uppermost layer may have warmed considerably. This generated a principal difference in temperature conditions between land and sea, with slightly higher temperatures in the marine environments. The period from c. 10 800 to 10 000 BP is characterized by very harsh conditions, with sea surface‐water temperatures close to freezing and long lasting seasonal sea‐ice cover. Similar temperature changes at the beginning and end of the Younger Dryas are characteristic for NW Europe, but those in Voldafjorden differ from those in the open sea and in the Norwegian Channel by being significantly larger. The stratification of the water column during the Late Allerφd was probably broken down because of incipient inflow of temperate normal saline waters, which caused a marked sea surface‐water warming, at c. 10 000 BP. Surface‐water conditions close to those of today were gradually established between c. 10000 and 9500 BP. However, these interglacial conditions were abruptly interrupted by a significant drop in winter sea surface‐water temperature and salinity occurring around 9700 BP. From c. 9500 to 7000 BP the influence of temperate normal saline water masses increased stepwise until full interglacial conditions were established around c. 7000 BP. The change in the dinocyst assemblage around 7000 BP in Voldafjorden was probably related to the onset of the modern Norwegian Coastal Current, previously documented in cores from the Skagerrak and the Mid‐Norwegian Continental Shelf. The last c. 7000 BP is characterized by relatively stable surface‐water conditions, possibly interrupted by periods of cooling or decreased inflow of temperate normal saline water. Like several other dinoflagellate cyst records from the Norwegian‐Greenland Sea, O. centrocarpum peak values are between 4000 and 5000 BP, suggesting a regional‐scale oceanographic change.
Early middle Pleistocene glacial sediments (780000‐620000 BP) near Kansas City, northeastern Kansas and northwestern Missouri, USA
Authors: COLGAN PATRICK M.
Published: July 2010

Two lithologically distinct tills are present near the pre‐Illinoian glacial boundary in northeastern Kansas and northwestern Missouri. The tills are probably early middle Pleistocene (780 000–620 000 BP) based on normal polarity and their stratigraphic relationship to dated terraces. The upper till is sandier than the lower till and contains more expandable clay minerals and less illite than the lower till. Glaciofluvial and supraglacial sediments are preserved between the tills, yet palaeosols, or other evidence of an interglacial, are not present, suggesting that the tills were deposited during a single glaciation. Southeasterly and southwesterly trending striae and till fabric suggest that the glacial succession was deposited by at least two fluctuations (phases) of a lobe, which probably advanced down the axis of the present Missouri River lowland. These tills probably correlate to early middle Pleistocene tills in southwestern Iowa and eastern Nebraska, although it is possible that the lower till may correlate to even older tills in these areas.
Chronology and paleoenvironments during the late Weichselian deglaciation of the southwest Iceland shelf
Authors: JENNINGS ANNE , SYVITSKI JAMES , GERSON LINDA , GRÖNVOLD KARL , GEIRSDÓTTIR ÁSLAUG , HARDARDÓTTIR JÓRUNN , ANDREWS JOHN , HAGEN SVEINUNG
Published: July 2010

Foraminifera, sedimentology, and tephra geochemistry in core 93030‐006 LCF from the southwestern Iceland shelf were used to reconstruct paleoenvironments between 12.7 and 9.4 14C ka BP. Seismic‐reflection profiles place the core in glacial‐marine and marine sediments within one meter of the underlying glacial till. Foraminifers in the earliest glacial‐marine sediments provide a record of ice‐distal conditions and immigration of slope species onto the shelf in association with warm Atlantic water. Meltwater increased during the Allerød under a weakened Atlantic water influence. Arctic conditions began by 11.14 14C ka BP with an abrupt increase in meltwater and near exclusion of boreal fauna from the shelf. Meltwater diminished in the early Younger Dryas, coinciding with sea‐surface cooling between 11.14 and 10.5 14C ka BP. A slight warming recorded in the uppermost glacial‐marine sediments was interrupted by an inferred jökulhlaup event emanating from glacier ice on the Western Volcanic Zone. Retreat of the ice margin from the sea sometime between c. 10.3 and 9.94 14C ka BP coincided with this event. The onset of postglacial marine sedimentation occurred along with increasing evidence of Atlantic water c. 9.94 14C ka BP and was interrupted by a short‐lived Pre‐boreal cooling of the Irminger Current c. 9.91 14C ka BP. Conditions similar to those today were established by 9.7 14C ka BP.
Palynological analyses in the laminated sediment of Lake Holzmaar (Eifel, Germany): duration of Lateglacial and Preboreal biozones
Authors: LEROY SUZANNE ALICE G. , ZOLITSCHKA BERND , NEGENDANK JÖRG F. W. , SERET GUY
Published: July 2010

The laminated sediment of Lake Holzmaar (Germany) has provided a continuous varve chronology for the last 3500 varve years (vy) and beyond that a floating varve chronology back to more than 22500 vy BP. This chronology in calendar years, in combination with palynology, enables us to determine the timing and the magnitude of Lateglacial and Early Holocene environmental changes on land (from 13838 to 10930 vy BP). The palynological diagram has a mean time resolution of 27 vy between samples. This paper establishes for the first time the biozonation for Lake Holzmaar below the Laacher See Tephra. Fifteen pollen subzones grouped in four biozones are defined by cluster analysis. After a period disturbed by microturbidites, only a part of the Bølling is present. Three cold periods have been evidenced by pollen analyses: the Older Dryas (96‐vy‐long), the Younger Dryas (654‐vy‐long) and the Rammelbeek phase (237‐vy‐long). The Allerød (883‐vy‐long) is bipartite with a first Betula‐dominated period followed by a Pinus‐dominated one. The Younger Dryas is also bipartite, with first a decrease of winter temperatures along with a change to a more continental climate. It is followed by a drier phase with a second decrease in temperatures, probably this time also affecting summer temperatures. The Preboreal is 702‐yr‐long. The duration of most phases corresponds to published records, except for that of the Younger Dryas. Cluster and rate‐of‐change analyses indicate a sharp change in the terrestrial vegetation assemblages that may be caused by a sedimentary hiatus of erosive origin during this cold and dry period. As a result, the chronology of Holzmaar has to be revised most likely below the middle of the Younger Dryas. Comparison with the varve record of Meerfelder Maar, a neighbour maar lake, suggests adding 320 vy below 12025 vy.
Last Interglacial stratigraphy at Ristinge Klint, South Denmark
Authors: KRISTENSEN PETER , GIBBARD PHILIP , KNUDSEN KAREN LUISE , EHLERS JÜRGEN
Published: July 2010

Past environmental changes in the Baltic area are discussed on the basis of foraminifera and ostracods as well as pollen and spores in marine sediments in cliff sections at Ristinge Klint, Langeland, southern Denmark. The sediment succession represents Jessen & Milthers' (1928) pollen zones d–g or Andersen's (1961, 1975) zones E2–E5, and a correlation with the annually laminated Bispingen sequence indicates that the sequence spans about 3400 years. Marine conditions seem to have occurred at c. 300–365 years after the beginning of the Eemian Interglacial, close to fully marine conditions developing by c. 2500 years. This early date of the marine ingression pre‐dates that of most previous studies in the region by several hundred years, but it postdates the initial marine ingression in the easternmost Baltic. A marked change in salinity at c. 650 years after the beginning of the Eemian was presumably caused by an opening of the Danish Belts. An indication of a major alteration in current activity is registered at c. 3000 years after the beginning of the interglacial. The recognition of the relative timing of these events may be significant for the understanding of the opening of connections between the North Sea, the Baltic and the White Sea.
Postglacial climate and vegetation history, north‐central Kola Peninsula, Russia: pollen and diatom records from Lake Yarnyshnoe‐3
Authors: SNYDER JEFFREY A. , MACDONALD GLEN M. , FORMAN STEVEN L. , TARASOV GENNADY A. , MODE WILLIAM N.
Published: July 2010

A sediment core from Lake Yarnyshnoe‐3 (69°04'N; 36°04'E), an emerged coastal lake from the tundra of the north‐central Kola Peninsula, has been analyzed for fossil pollen and diatoms. The pollen record shows the Younger Dryas event marked by increasing Artemisia coupled with decreases in Poaceae, Cyperaceae and Salix at c. 10 700 to 10 000 BP. This core provides the first well‐defined palynological record of the Younger Dryas event on the Kola Peninsula. Stomates from Pinus were recovered from the core interval between 8000 and 6000 BP. The stomates, coupled with elevated values of pine pollen, indicate that Pinus sylvestris grew near the arctic coastline of the central Kola Peninsula in the middle Holocene. However, the small number of stomates suggests that pines were not plentiful. The diatom record from the core reflects basin isolation from the sea and indicates additional limnological changes during the climate transition between c. 5000 and 4000 BP. The broadly similar climate and vegetation history on the north‐central Kola Peninsula and in Fennoscandia demonstrates the propagation of late glacial and Holocene climate events from the North Atlantic region into the Eurasian Arctic.
Early Holocene drowned lagoonal deposits from the Kattegat, southern Scandinavia
Authors: BENNIKE OLE , JENSEN JØRN BO , KONRADI PETER B. , LEMKE WOLFRAM , HEINEMEIER JAN
Published: July 2010

Shallow seismic profiling indicated the presence of a drowned lagoon–barrier system formed during the transgression of the southern Kattegat, and investigations of core material have confirmed this. Studies of plant and animal macrofossils show that the lagoonal sediments contain a mixture of marine, brackish, lacustrine, telmatic and terrestrial taxa, and analyses of foraminifers indicate brackish‐water conditions. Low oxygen isotope values obtained on shells of marine molluscs also point to lowered salinity. The lagoonal sediments are situated at depths between 24 and 35 m below present sea level. They are dated to between c. 10.5 cal. ka BP and c. 9.5 cal. ka BP, and reflect a period characterized by a moderate relative sea level rise. The lagoonal sediments are underlain by lateglacial glaciomarine clay and silt, which are separated from the Holocene deposits by an unconformity. The earliest Holocene sediments consist of littoral sand with gravel, stones and shells; these sediments were formed during the transgression of the area before the barrier island–lagoon system was developed. The lagoonal sediments are overlain by mud, which contains animal remains that indicate increasing water depths.
Quaternary chronostratigraphy: the nomenclature of terrestrial sequences
Authors: GIBBARD PHILIP L. , WEST RICHARD G.
Published: July 2010

There is a long‐standing tradition of dividing Quaternary stratigraphical sequences on the basis of climate. This climatostratigraphical approach, begun on terrestrial sequences in the last century, led to the widespread adoption of glacial, interglacial, stadial and interstadial subdivisions as standard. However, the limitations of the approach resulted in its replacement by local sequences of chronostratigraphical stages from the 1950s. The subsequent establishment of the detail and complexity of ocean‐core sequences has encouraged increasing use of the terminology developed for these records to the terrestrial and shallow marine succession. The view is expressed that it is advisable to separate and retain regional chronostratigraphies for each sequence‐type, and that these should be correlated using event‐based stratigraphy where possible. This should ensure both the highest precision and lack of ambiguity and a securely‐based synthesis of the relations between the terrestrial and ocean isotope sequences, a synthesis which is fundamental to understanding the nature and detail of regional and global climate change.
Holocene paleoceanography of the northern Barents Sea and variations of the northward heat transport by the Atlantic Ocean
Authors: DUPLESSY JEAN‐CLAUDE , IVANOVA ELENA , MURDMAA IVAR , PATERNE MARTINE , LABEYRIE LAURENT
Published: July 2010

Foraminiferal assemblages were studied in northern Barents Sea core ASV 880 along with oxygen and carbon isotope measurements in planktonic (N. pachyderma sin.) and benthic (E clavatum) species. AMS C‐14 measurements performed on molluscs Yoldiella spp. show that this core provides a detailed and undisturbed record of Holocene climatic changes over the last 10000 calendar years. Surface and deep waters were very cold (<0°C) at the beginning of the Holocene. C. reniforme dominated the highly diverse benthic foraminiferal assemblage. From 10 to 7.8 cal. ka BP, a warming trend culminated in a temperature optimum, which developed between 7.8 and 6.8 cal. ka BP. During this optimum, the input of Atlantic water to the Barents Sea reached its maximum. The Atlantic water mass invaded the whole Franz Victoria Trough and was present from subsurface to the bottom. No bottom water, which would form through rejection of brine during winter, was present at the core depth (388 m). The water stratification was therefore greatly reduced as compared to the present. An increase in percentage of I. helenae/norcrossi points to long seasonal ice‐free conditions. The temperature optimum ended rather abruptly, with the return of cold polar waters into the trough within a few centuries. This was accompanied by a dramatic reduction of the abundance of C. reniforme. During the upper Holocene, the more opportunistic species E. clavatum became progressively dominant and the water column was more stratified. Deep water in Franz Victoria Trough contained a significant amount of cold Barents Sea bottom water as it does today, while subsurface water warmed progressively until about 3.7 cal. ka BP and reached temperatures similar to those of today. These long‐term climatic changes were cut by several cold events of short duration, in particular one in the middle of the temperature optimum and another, which coincides most probably with the 8.2 ka BP cold event. Both long‐ and short‐term climatic changes in the Barents Sea are associated with changes in the flow of Atlantic waters and the oceanic conveyor belt.
Middle to Late Pleistocene vegetation history and climatic changes at Lake Kopais, Southeast Greece
Authors: OKUDA MASAAKI , YASUDA YOSHINORI , SETOGUCHI TAKESHI
Published: July 2010

This study presents a detailed vegetation history of Lake Kopais, Southeast Greece based on pollen analysis of a 120 m‐long sediment core. The record extends from the Holocene back to Oxygen Isotope Stage 11, and it gives a detailed history of Mediterranean evergreen woodlands during the last 500 ka. Vegetation of glacials consisted of open steppe with Chenopodiaceae and Artemisia associated with Tubuliflorae and other herbs, while that of interglacials was dominated by temperate Quercus forest. The Last Interglacial (Substage 5e) shows a complete vegetation succession starting with Juniperus and Betula, followed by deciduous oak and ending with Pinus and Abies. Wild olive is abundant in Substages 11c and 5e, suggesting very warm climatic conditions in Stage 11. Stages 9 and 7 were significantly cooler than 11 and 5e. The Pterocarya occurrence near the bottom of the core provides a possible equivalent of the Holsteinian Interglacial.
A Holocene lacustrine record of environmental change in northeastern Prince of Wales Island, Nunavut, Canada
Authors: GAJEWSKI KONRAD , FRAPPIER MONIQUE
Published: July 2010

A core from Prince of Wales Island in the central Canadian Arctic was analysed for pollen and sediment characteristics. From 9200 yr BP to 7000 yr BP, the landscape supported a pioneer vegetation under cold conditions, with relatively high sediment input to the lake. Between 7000 and 4000 yr BP there was a period of high pollen concentrations, more abundant Cyperaceae and Dryas on the landscape and finer sediment input. In the last 4000 years, climate cooling is indicated.
Vegetation, climate and ice‐front oscillations in the Tromsø area, northern Norway during the Allerød and Younger Dryas
Authors: FIMREITE SOLVEIG , VORREN KARL‐DAG , VORREN TORE O.
Published: July 2010

Sediments from two small lakes distal to the Tromsø–Lyngen moraine at Tromsø, northern Norway, indicate that the area was deglaciated prior to c. 11.7 14C ka BP. The earliest vegetation was dominated by calciphilous and heliophilous pioneer plants on unstable soils; this changed to a vegetation reflecting a dry continental climate until c. 10.7 14Cka BP. A phase (10.7–10.5 14Cka BP) with snow‐bed communities was followed by one with a mosaic of plant communities. This was succeeded by Empetrum heaths c. 10.3 14Cka BP, then by an open forest with Betula pubescens after 10.0 14Cka BP. Ice‐front oscillations in the Tromsø area are evaluated. The main part of the Younger Dryas glacial readvance, the Tromsø–Lyngen event, probably occurred between 10.7 and 10.3 14Cka BP.
The Late Weichselian sea level history of the Kullen Peninsula in northwest Skåne, southern Sweden
Authors: SANDGREN PER , SNOWBALL IAN
Published: July 2010

The Kullen Peninsula in northwest Skåne, at the time of the Weichselian deglaciation an island surrounded by the Kattegat Sea, is the earliest known deglaciated area in Sweden. Sediment stratigraphic and mineral magnetic properties, combined with radiocarbon dating, were used to determine and date the isolation of present‐day lake basins from the sea. Significant environmental changes, which reflect the isolations, are supported by previously published palaeoecological data and cannot be related to climate changes. Basins situated above the marine limit (ML) have short (in the order of centimetres) minerogenic sequences that are magnetically characterized by low concentrations of detrital magnetite. In contrast, the pre‐isolation sediments in basins below the ML, especially those deposited in sheltered positions in the landscape, have thick sequences (in the order of metres) of authigenic greigite‐bearing sediments. Age determinations of the isolation level are based on the AMS radiocarbon dating of terrestrial plant macrofossil remains and previously published pollen stratigraphical investigations. Supported by the upper level of a sandy beach deposit preserved on the generally steep till covered slopes, the marine limit can be determined to 88–89 m a.s.l., which developed at the regional deglaciation c. 17000 calendar years ago. The results indicate that the deglaciation shoreline level remained fairly constant, relative to the sea level, for c. 1000 years and was followed by a gentle regression. The presented shoreline displacement curve from the Kullen Peninsula extends c. 1000 calendar years further back in time than any previously published records from the Swedish west coast.
Effects of late Pleistocene permafrost on the landscape of Wisconsin, USA
Authors: CLAYTON LEE , ATTIG JOHN W. , MICKELSON DAVID M.
Published: July 2010

Pleistocene permafrost had a major but generally unappreciated effect on the landscape of Wisconsin, second only to glaciation. Evidence for continuous permafrost during the last part of the Wisconsin Glaciation includes ice‐wedge casts seen both in outcrop (generally in gravel pits) and as polygonal networks (on aerial photographs). Other important evidence includes fossil tundra organisms. Other features that are probably the result of permafrost in Wisconsin include talus cones, block streams, solifluction rubble at the base of most hillslopes, fluvial cobble gravel, gullies that are today inactive, lake‐ice collapse trenches, and ice‐walled‐lake plains. Permafrost caused accelerated regional erosion of the landscape; most topographic features formed before the last permafrost melted have been highly modified or even destroyed, whereas those formed after are much better preserved. In addition, the presence of permafrost influenced many glacial processes and land‐forms. Permafrost was present until about 14000 yr BP in the southern part of the state to about 10000 yr BP in the northern part.