bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimizing sampling strategy for radiocarbon dating of Holocene fluvial systems in a vertically aggrading setting
Authors: TÖRNQVIST TORBJÖRN E. , DIJK GEO J. VAN
Published: July 2010

In this paper we address the question of how to determine the period of activity (sedimentation) of fossil (Holocene) fluvial systems in vertically aggrading environments. Our data base consists of almost 10014C ages (partly AMS) from the Rhine–Meuse delta in the central Netherlands. Radiocarbon samples from the tops of lithostratigraphically correlative organic beds underneath overbank deposits (sample type 1) yield consistent ages, indicating a synchronous onset of overbank deposition over distances of at least up to 20 km along channel belts. Similarly,14C ages from the base of organic residual channel fills (sample type 3) generally indicate a clear termination of within‐channel sedimentation. In contrast,14C ages from the base of organic beds overlying overbank deposits (sample type 2), commonly assumed to represent the end of fluvial sedimentation, show a large scatter reaching up to 100014C years. This setting usually produces14C ages significantly younger than residual channels of the same fluvial system, indicating the presence of non‐depositional unconformities. These usually occur on top of slightly elevated sediment bodies (especially natural levee deposits), which often contain palaeosols. Such hiatuses appear to be much more abundant than hitherto supposed. We conclude that a combination of sample types 1 and 3 generally yields a satisfactory delimitation of the period of activity of a fossil fluvial system. The problems associated with14C samples of type 2 may also be present in coastal areas with an alternation of tidal deposits and organic beds.
The Fossvogur marine sediments in SW Iceland ‐ confined to the Allerød/Younger Dryas transition by AMS 14 C dating
Authors: SVEINBJÖRNSD́OTTIR ÁRNÝ E. , EIRÍKSSON JÓN , GEIRSDÓTTIR ÁSLAUG , HEINEMEIER JAN , RUD NIELS
Published: July 2010

An exhaustive14C dating programme of molluscs from the Fossvogur sediments in Reykjavik. Iceland is presented. For the first time all the fossiliferous units of the sediments are dated. The results confirm earlier conclusions of a widespread occurrence of marine sediments of Allerød age in Reykjavik. The set of dates from the Fossvogur sediments shows a narrow14C age distribution (standard deviation of ±235 years) of molluscs from all localities and from successive marine units in vertical sections. The weighted mean conventional14C age is 11,400 BP. Assuming a reservoir effect of 400 years. this corresponds to a reservoir‐corrected age of I1,000 BP. i.e. the Allerød‐ Younger Dryas transition for the sampled units, These new14C dates from Fossvogur confirm the need for a revision of the Upper Pleistocene chronology of the Reykjavik region. They also have a bearing on the Late Weichselian record of glacier readvances and sea‐level changes in the area. The dates suggest that the marine units in Fossvogur accumulated within a restricted time‐span of a few hundred years. The sediments in Fossvogur are of volcaniclastic origin and are extremely lithified, indicating local geothermal activity soon after their deposition. This may explain anomalously high D/L amino acid ratios measured in molluscs from the Fossvogur sediments. δ13C and δ18O results suggest that temperatures may have ranged up to 60°C.
Late Wisconsin glacial advance and retreat patterns in southwestern Ohio, USA
Authors: EKBERG MICHAEL P. , LOWELL THOMAS V. , STUCKENRATH ROBERT
Published: July 2010

Despite the application of radiocarbon dating for more than three decades along the southern margin of the Laurentide Ice Sheet, fundamental questions about the timing of glacial advances remain. For one of its sublobes, the Miami, we undertook areal mapping, detailed lithostratigraphic analysis, and radiocarbon dating to interpret four pulses of ice advance. On top of the undated sediments deposited during the first advance is a major unconformity. The second advance occurred about 20,000 BP and marks the beginning of the late Wisconsin glaciation. A minor recession (more than 30 km) ensued, but plants did not reoccupy the landscape. A third advance of the ice margin produced a stone‐rich lodgement till to within 20 km of the late Wisconsin maximum. The final ice motion only occurred in the northern part of the study area and may be of local extent. Large accumulations of supraglacial gravity flowtills and outwash mark the final ice‐margin retreat. Of these. only the second advance is well dated. This study implies that the number of advances of the ice margin is fewer than previously suggested. Consequently we argue that several of the sublobes across the southern margin of the Laurentide Ice Sheet acted in unison for the interval of 22.000 to 18.000 BP implying ice‐sheet external forcing.
Morphology, stratigraphy and oxygen isotope composition of fossil glacier ice at Ledyanaya Gora, Northwest Siberia, Russia
Authors: VAIKMÄE REIN , MICHEL FREDERICK A. , SOLOMATIN VLADIMIR I.
Published: July 2010

Studies of the stratigraphy, sedimentology, structure and isotope composition of a buried massive ice body and its encompassing sediments at Ledyanaya Gora in northwestern Siberia demonstrate that the ice is relict glacier ice, probably emplaced during the Early Weichselian. Characteristics of this ice body should serve as a guide for the identification of other relict buried glacier ice bodies in permafrost regions.
Pleistocene glacial deposits along the eastern periphery of the Scandinavian ice sheets ‐ an overview
Authors: RAUKAS ANTO , GAIGALAS ALGIRDAS
Published: July 2010

The Quaternary glacial sequences in the Baltic region in Estonia. Latvia and Lithuania are relatively complete and reasonably well studied. The maximum thickness of deposits (200 300 m) is found in the uplands and ancient valleys. Tills of several genetic types have been described and in this paper the present view on the structure of the Pleistocene cover is given. The ice movement and glacial sedimentation were controlled by climate. underlying topography and tectonic processes.
Paleoenvironments and correlations of interglacial sediments in the North Sea
Authors: SEJRUP HANS PETTER , KNUDSEN KAREN LUISE
Published: July 2010

Benthic foraminiferal faunas suggesting interglacial climatic conditions are present in several shallow drillings in the North Sea and in northern Jutland. Denmark. The interglacial deposits in six of the cores arc correlated by means of isoleucine epimerization, paleomagnetic data and environmental inferences. Four episodes of interglacial circulation are recorded in sediments of Brunhes age and one warm episode is found just below the Brunhes Matuyama boundary. The Holocene and Eemian faunas of the North Sea are richer in species and individuals and contain more thermophilous species than the older interglacial faunas. However. a much more northern distribution of Bulimina marginata in sediments of Eemian age suggests that oceanic circulation was different during this period than during the Holocene. Sediments of the three other Brunhes interglacials (the Holsteinian, the Norwegian Trench and the Devils Hole Interglacial) and the Leerdam Interglacial record periods of relatively cooler conditions and possibly reduced inflow of Atlantic water.
The vertical extent of ice sheets in Nordfjord, western Norway: measuring degree of rock surface weathering
Authors: McCARROLL DANNY , NESJE ATLE
Published: July 2010

Degree of rock surface weathering was measured on sites in Oldedalen and Brigsdalen, where dates of deglaciation have been estimated. and on an altitudinal transect on the slopes of Skåla. representing one of the highest supra‐marine reliefs in western Norway. The Schmidt hammer is useful only for distinguishing sites deglaciated during the Little Ice Age from those deglaciated during the Lateglacial and early Holocene. Degree of roughness of granitic augen gneiss bedrock surfaces was quantified from profiles measuredin situusing a micro‐roughness‐meter and profile gauge. There is a significant increase in surface roughness above a clear trimline at c. 1350 m a.s.I. but no significant increase above a higher trimline previously proposed as the vertical limit of the last ice sheet in this area (c. 1560 m a.s.I.). The roughness of boulder surfaces on the summit blockfield does not direr significantly from the roughness of bedrock surfaces downslope as far as the lower trimline. These unexpected results suggest that bedrock surfaces between the two trimlines were not glacially abraded during the Late Weichselian, so that the upper trimline is unlikely to represent the vertical limit of ice during either the Late Weichselian or a subsequent readvance. Preliminary results of10Be dating of surface quartz samples from above the lower trimline support the proposal that the site was not abraded during the last glaciation. The results can be interpreted in two ways: (1) The upper trimline represents the vertical limit of a pre‐Late Weichselian advance. During the Late Weichselian the mountains were completely covered but surfaces down to the lower trimline were protected by cold‐based ice. (2) The lower trimline marks the vertical limit of the Late Weichselian ice and the upper limit an older and more extensive glaciation.
Foraminifera from the Quaternary sequence in the Anholt boring, Denmark
Authors: SEIDENKRANTZ MARIT‐SOLVEIG
Published: July 2010

The Quaternary sequence of a boring from the island of Anholt, Denmark, comprises both marine and non‐marine sediments spanning a time interval from the Holocene to at least as far back as the Saalian. The oldest Quaternary sediments consist of a till and a glaciofluvial sand sequence. These are overlain by marine silty clays of Saalian to Eemian age. An interstadial (Flakket Interstadial) and a stadial (Kattegat Stadial) are identified in the late Saalian. This climatic fluctuation has been compared to the Allerød and Younger Dryas events at the Weichselian–Holocene transition. The Eemian sediments are followed by sand and non‐marine, varved clay overlain by 2 m of marine clay, which is correlated with the Middle Weichselian of the Skærumhede series. The marine clay is covered by silty clay and a thick sand sequence of non‐marine origin. The uppermost 2 m sediments may represent the Holocene coastal accretion on Anholt.
Middle Weichselian to Holocene palaeoecology in the eastern Kattegat, Scandinavia: foraminifera, ostracods and 14C measurements
Authors: SEIDENKRANTZ MARIT‐SOLVEIG , KNUDSEN KAREN LUISE
Published: July 2010

Examination of a 10 m piston core from the eastern Kattegat revealed marine sediments spanning a period from the late Middle Weichselian to the Early Holocene. The oldest marine unit in the core is 14C‐dated to about 30,000–36,000 years BP. These sediments represent the Middle Weichselian Sandnes/Denekamp‐Hengelo Interstadial (upper part of stable isotope stage 3) and can be correlated to marine deposits from several localities in the Kattegat region by means of foraminifera. The Late Weichselian deposits comprise sediments from the Oldest Dryas Stadial and the Allerød Interstadial. The intervening periods are not represented in the sequence (hiatuses). Sediments from the latest part of the Early Holocene Preboreal period succeeding the Allerod sequence indicate a considerable hiatus spanning 2000–3000 years around the Weichselian/Holocene boundary. The late Preboreal faunas document a high freshwater inflow during this period, and stable conditions seem not to have been reached in the area until a few hundred years later, in the Boreal period. Comparison with boxcore material from the same site documents a reduction of the energy level of the bottom currents some time between c. 8000 and 800 years BP.
Dislocated Quaternary deposits in southeastern Kattegat – a glacial or gravitational phenomenon?
Authors: VANGKILDE‐PEDERSEN THOMAS , LYKKE‐ANDERSEN HOLGER , LIND GUSTAF
Published: July 2010

The Quaternary deposits in the Store Middelgrund–Rørdebanke area midway between the island of Anholt and Hallandsåsen on the Swedish coast are described on the basis of reflection seismic profiles with a vertical resolution of 5–10 m. The Quaternary rests on Upper Cretaceous limestone, the surface of which is nearly horizontal. Three Quaternary sequences are defined and interpreted as: (1) Late Weichselian marine or lacustrine deposits, (2) Late Weichselian glaciogenic deposits, and (3) Late Saalian–Eemian and Early–Middle Weichselian deposits. Sequence 3 is probably comparable to the upwards‐coarsening sequence known from Skaerumhede in Vendsyssel. The layers in sequence 3 are dislocated in the eastern part of the Store Middelgrund–Rødebanke area mainly by gentle folding, but other types of deformations occur. Folding could be the result of horizontal push from an ice sheet approaching from the east. Alternatively the folding is an effect of vertical, gravitational forces acting on the sediments due to an unstable density profile, as described by the Rayleigh–Taylor instability model. The zone of deformation is located close to the northern flank of the tectonically active Sorgenfrei–Tornquist Zone. It is suggested that the initiation of the folding process was facilitated by tremors from small earthquakes.
Timing and pattern of the last deglaciation in the Kattegat region, southwest Scandinavia
Authors: LAGERLUND ERIK , HOUMARK‐NIELSEN MICHAEL
Published: July 2010

This paper presents evidence on the timing and pattern of the Late Weichselian deglaciation in SW Scandinavia, particularly in the Öresund–Kattegat region before the Allerød interstadial. New radiocarbon ages and evaluated older dates demonstrate that active glacier ice had left eastern Denmark, southern Halland and western Skåne before 14,000 BP. The deglaciation in the Öresund region took place mainly under glacioestuarine conditions in a narrow fjord or inlet with some marine influence, as indicated by radiocarbon‐dated finds of Polar Cod (Boreogadus saida) and the vertebra of a Ringed Seal (Phoca hispida). The Swedish west coast experienced glaciomarine and deltaic ice proximal conditions, where Vendsyssel was at the same time under full marine conditions with little evidence of ice rafting. A paleogeographic interpretation illustrates land, sea and ice configurations around 14,000 BP. We suggest that a subsequent lateglacial transgression reached the entire region almost simultaneously and peaked around 13,300 BP. This led to deposition of an ice‐rafted diamicton (the Öresund diamicton) in Skåne and Sjælland, and of glaciolacustrine mud in Halland. We propose that the complex transgression and regression events recorded in the region were governed by interaction of the eustatic sea level rise, isostatic reponse to glacier unloading and possibly also by damming by an ice stream in the Skagerrak and northern Kattegat.
Late Weichselian glaciation history of the northern North Sea
Authors: SEJRUP HANS PETTER , HAFLIDASON HAFLIDI , AARSETH INGE , KING EDWARD , FORSBERG CARL FREDRIK , LONG DAVID , ROKOENGEN KÅRE
Published: July 2010

Based on new data from the Fladen, Sleipner and Troll areas, combined with earlier published results, a glaciation curve for the Late Weichselian in the northern North Sea is constructed. The youngest date on marine sedimentation prior to the late Weichselian maximum ice extent is 29.4 ka BP. At this time the North Sea and probably large parts of southern Norway were deglaciated (corresponding to the Alesund interstadial in western Norway). In a period between 29.4 and c. 22 ka BP, the northern North Sea experienced its maximum Weichselian glaciation with a coalescing British and Scandinavian ice sheet. The first recorded marine inundation is found in the Fladen area where marine sedimentation started close to 22 ka BP. After this the ice fronts receded both to the east and west. The North Sea Plateau, and possibly parts of the Norwegian Trench, were ice‐free close to 19.0 ka, and after this a short readvance occurred in this area. This event is correlated with the advance recorded at Dimlington, Yorkshire, and the corresponding climatostratigraphic unit is denoted the Dimlington Stadial (18.5 ka to 15.1 ka). The Norwegian Trench was deglaciated at 15.1 ka in the Troll area. The data from the North Sea, together with the results from Andwa, northern Norway (Vorren et al. 1988; Møller et al. 1992), suggest that the maximum extent of the last glaciation along the NW‐European seaboard from the British Isles to northern Norway was prior to c. 22 ka BP.
Episodic ice streams and ice shelves during retreat of the northwesternmost sector of the late Wisconsinan Laurentide Ice Sheet over the central Canadian Arctic Archipelago
Authors: HODGSON DOUGLAS A.
Published: July 2010

A complex of glacial landforms on northeastern Victoria Island records diverse flows within the waning late Wisconsinan Laurentide Ice Sheet over an area now divided by marine straits. Resolution of this ice flow pattern shows that dominant streamlined landforms were built by three radically different ice flows between 11,000 and 9000 BP. Subsequent to the glacial maximum, the marine‐based ice front retreated at least 300 km to reach northeast Victoria Island by 10,400 BP. Disequilibration at the rapidly retreating margin induced minor surges on western Storkerson Peninsula (Flow 1). Next, a readvance into Hadley Bay transported 10,300 BP shells, while a major ice stream over eastern Storkerson Peninsula (Flow 2) remoulded till into a drumlin field several hundred kilometres long and at least 80 km wide until flow ceased prior to 9600 BP. The ice stream surged into Parry Channel, covering 20,000 km2 with the Viscount Melville Sound Ice Shelf. Finally, Flow 2 drumlins on the northwest shore of M'Clintock Channel were cross‐cut c. 9300 BP by advance of the grounded margin of a buoyant glacier (Flow 3), possibly an analogue of Flow 2 displaced farther south.
Quaternary changes in level of the upper Taylor Glacier, Antarctica: implications for paleoclimate and East Antarctic Ice Sheet dynamics
Authors: MARCHANT DAVID R. , DENTON GEORGE H. , BOCKHEIM JAMES G. , WILSON SCOTT C. , KERR ANDREW R.
Published: July 2010

Glacial drifts perched alongside outlet glaciers that drain through the Transantarctic Mountains constrain inland polar plateau ice elevations. The Taylor Glacier, which heads in the Taylor Dome (a peripheral dome of the East Antarctic Ice Sheet), drains East Antarctic ice into the Dry Valleys sector of Transantarctic Mountains and terminates in central Taylor Valley, about 24 km west of the Ross Sea. Five gravel‐rich drifts (including 39 distinct moraine ridges) fringe a lateral lobe of the Taylor Glacier in the lower Arena Valley, Quartermain Mountains, southern Victoria Land. 3He and 10Be exposure age dating (from Brook et al. 1992), together with Arena Valley stratigraphy and soil morphologic data, provide chronologic control for these drifts and constrain maximum Quaternary thickening of the inland Taylor ice dome to less than 160 m. These minor Quaternary expansions of Taylor Glacier were out‐of‐phase with outlet glaciers that pass through the Transantarctic Mountains and terminate in the Ross Sea north and south of the Dry Valleys region. Textural analyses suggest that drift deposition occurred from cold‐based ice, even though Taylor Glacier advances most likely occurred during global interglaciations. The thermal regime of former Taylor Glacier ice lobes, the character of geomorphic features superimposed on individual drifts, the chemical composition of soils developed on Taylor drifts, and the stability of in situ moraine ridges on steep valley walls suggest that the present cold‐desert climate in Arena Valley has persisted for at least the last 2.2 Ma.
North American Quaternary cold‐tolerant turtles: distributional adaptations and constraints
Authors: HOLMAN J. ALAN , ANDREWS KENNETH D.
Published: July 2010

The painted turtle,Chrysemys picta, and the snapping turtle,Chelydra serpentina, occur in aquatic habitats north of Lake Superior in boreal forest and cold prairie areas across Canada, and have by far the most northern range of any modern North American chelonian taxa. These two species are also the dominant turtles of the North American Pleistocene glacial ages and were among the first species to invade formerly glaciated areas at the end of the Wisconsinan. These Pleistocene occurrences are documented here. Several remarkable behavioral, physiological and reproductive adaptations that may act together to allow these species to survive in such northern areas are discussed.
Late‐glacial and early Holocene environments at Pine Hill Pond, Newfoundland, Canada: evidence from pollen and diatoms
Authors: WOLFE ALEXANDER P. , BUTLER DEBORAH L.
Published: July 2010

The basal 150 cm of lacustrine sediment in a 380 cm core from Pine Hill Pond, eastern Newfoundland, includes the late‐glacial and early Holocene and contains strong sedirnentological and paleoecological evidence for a climatic oscillation correlative with the Younger Dryas event. Basal late‐glacial minerogenic sediments are overlain by a silty gyttja marking the onset of organic sedimentation. An overlying unit comprising 7 cm of silty clay marks a return to mineral sedimentation prior to subsequent uninterrupted deposition of organic sediments. During this phase, the reversion from shrub tundra to a sparser herb‐shrub tundra pollen assemblage (Oxyria digyna, Arremisia) is a strong indicator of climatic deterioration at the site. The paleolimnological expression of the Younger Dryas event at this site is manifested by a sharp decrease of diatom concentrations followed by decreases in the relative frequencies of Fragilaria spp., which are largely replaced by a stratigraph‐ically restricted group of unusual benthic forms, a rise in the relative frequency of chrysophyte cysts, and a crash in Pediastrum concentrations. The nature and timing of palynological and diatom changes are interpreted in terms of both the direct and indirect consequences of climatic deterioration, as well as within the stratigraphic context of sediment lithological changes.
Proglacial glaciotectonic deformation at Melabakkar‐Ásbakkar, west Iceland
Authors: HART JANE K.
Published: July 2010

A study of proglacial deformation associated with a Late Weichselian glaciomarine sequence was carried out at Melabakkar‐Ásbakkar, west Iceland. At this site, coarse‐grained sediments have been deformed into compressive structures with no associated push moraine morphology. Two large structures were examined, Structure A which consists of large‐scale reverse (and normal) faulting and overturned bedding; and Structure B, which is more complex, with open folding, high‐angle reverse faulting, nappe structures and normal faulting. The structures were interpreted as the result of increasing compressive proglacial deformation, followed by subglacial deformation, which destroyed the surface morphology of the push moraine and incorporated some of the sediments into a subglacial diamicton. The results from this study were compared with other examples of proglacial deformation, and it is suggested that at sites where deformation was restricted to the margin, longitudinal strain was lower than at sites where deformation extended out into the foreland. It is also suggested that if deformation increases downglacier, this is indicative of an overall glacial advance, whilst if the deformation decreases downglacier, this is indicative of a glacial retreat.
Sedimentary facies and environmental history of the Late‐glacial glaciomarine Fossvogur sediments in Reykjavík, Iceland
Authors: GEIRSDÓTTIR ÁSLAUG , EIRÍKSSON JÓN
Published: July 2010

A detailed account of facies relationships in the Late‐glacial Fossvogur beds is presented for the first time. A new interpretation in terms of sedimentary processes has been synthesized in a palaeoenvironmental reconstruction that incorporates the results of a recently completed, systematic14C dating project for the Fossvogur beds. The present sedimentological analysis has revealed three marine fossiliferous facies and several diamictite facies. The two uppermost marine facies are separated by a horizon of local deformation and erosion which is ascribed to increased activity at a tidewater glacier margin in Fossvogur. The fact that marine fossiliferous sediments below and above this horizon have been confined to the Allerød chron indicates a temporary expansion of glaciers in the Reykjavík region towards the end of, but within, the Allersd. The relative sea level must have been at least 20 m higher than at present before the expansion, and it was probably even higher during and after the expansion. The total absence of facies indicating either lodgement or melt‐out processes, and the abundance of diamictites interpreted as debris‐flow deposits as well as frequent erratics in the marine mudrocks favour an interpretation based on a glaciomarine model for the Allerød deposition in Fossvogur. It is suggested that the relatively quiet, submarine conditions indicated by facies towards the top of the Fossvogur beds display continued transgression and an increased distance to the source of sediment supply during the Younger Dryas.
Palaeoenvironments and changes in relative sea level during the last interglaciation at Langelandselv, Jameson Land, East Greenland
Authors: VOSGERAU HENRIK , FUNDER SVEND , KELLY MICHAEL , KNUDSEN KAREN LUISE , KRONBORG CHRISTIAN , MADSEN HANNE BIRGIT , SEJRUP HANS PETTEK
Published: July 2010

Coastal cliffs and stream cut sections at Langelandselv on Jameson Land show a 22 m thick sedimentary succession reflecting the development of shallow marine and fluvial environments during the last interglaciation. The shallow marine sediments were deposited in upper shoreface, back‐barrier, and delta environments during a rise in the relative sea level from 0 to 18 m. The interglacial succession ends with glaciotectonically dislocated fluvial sand, and is capped by alternating beds of lodgement till and fluvial sand, deposited during the Early Weichselian. The age is determined by palacoceanographic correlation of molluse and foraminifer faunas with isotopic substage 5e in the deep sea record, supported by luminescencs and U/Th dates and amino acid analysis.
Late Quaternary glacial history of the central west coast of Jameson Land, East Greenland
Authors: INGÓLFSSON ÓLAFUR , LYSÅ ASTRID , FUNDER SVEND , MÖLLER PER , BJÖRCK SVANTE
Published: July 2010

The Late Quaternary (c. 130,000–10,000 BP) glacial history of the central west coast of Jameson Land, East Greenland, is reconstructed through glacial stratigraphical studies. Seven major sedimentary units are described and defined. They represent two interglacial events (where one is the Holocene). one interstadial event and two glacial events. The older interglacial event comprises marine and fluvial sediments, and is correlated to the Langelandselv interglacial, corresponding to oxygen isotope sub‐stage 5e. It is followed by an Early Weichselian major glaciation during the Aucellaelv stade, and subsequently by an Early Weichselian interstadial marine and deltaic event (the Hugin Sø interstade). Sediments relating to the Middle Weichselian have not been recognized in the area. The Hugin Sø interstade deposits have been overrun by a Late Weichselian ice advance, during the Flakkerhuk stade, when the glacier, which probably was a thin, low gradient fjord glacier in Scoresby Sund, draped older sediments and landforms with a thin till. Subsequent to the final deglaciation, some time before 10,000BP, the sea reached the marine limit around 70 m a.s.l., and early Holocene marine, fluvial and littoral sediments were deposited in the coastal areas.
Revision of the early Holocene lake sediment based chronology and event stratigraphy on Hochstetter Forland, NE Greenland
Authors: BJÖRCK SVANTE , WOHLFARTH BARBARA , BENNIKE OLE , HJORT CHRISTIAN , PERSSON THOMAS
Published: July 2010

The previously established and often debated lake sediment based chronology and event stratigraphy from Hochstetter Forland, NE Greenland, has been re‐examined. These new studies show that the last deglaciation of the coastal area is several thousand years younger than previously described. The main reason behind the difference is the fact that the older chronology was based on14C datings of bulk sediment samples, which are now shown to contain enough coal fragments to produce erroneous ages. The re‐examination was performed on sediments from two lakes located within the Nanok moraine system: one is situated at or slightly above the marine limit around 65 m. the other at 21–22 m a.s.l. The combined stratigraphy from the two lakes shows that the area was deglaciated before 9000 BP, after which followed deposition of glaciomarine sediments, fining upwards. The first vegetation seems to have been dominated by grasses,Lycopodiumand Polypodiaceae. Atc. 8000 BP the limnic production increased significantly and a pioneer vegetation characterized the area. At this time the‘Artemisia’grains appear. A short but distinct climatic cooling occurs atc. 7500 BP causing a significant drop in lake productivity and possibly also producing coarser sediments in the (glacio)marine environment. About 200 years later the lake productivity again increased, very rapidly, and the marine sediments became finer and more rich in molluscs, as a response to the beginning of the climatic optimum. Because of the time‐lag between climate and vegetation response it took another 300 years beforeBetulci nanaimmigrated, at the same time as the‘Artemisia’grains disappeared, and another several hundred years before a real dwarf‐shrub vegetation developed in these parts of Hochstetter Forland. Before the lower lake was isolated from the sea atc. 6000 BP, coarse wave‐washed sediments, followed by a typical isolation sequence, were deposited in it.
Holocene changes on a peatland in northwestern Ontario interpreted from testate amoebae (Protozoa) analysis
Authors: WARNER BARRY G. , CHARMAN DANIEL J.
Published: July 2010

Radiocarbon‐dating and analyses of fossil testate amoebae (Protozoa) have established changes in soil moisture conditions on the developing surface of a Sphagnum ‐dominated peatland near Emo in northwestern Ontario.

The distribution and composition of modern testate amoebae communities were studied from peatlands in the region of Ontario and Minnesota as a guide to interpreting fossil assemblages. Although the core spans all of the Holocene, fossil testate amoebae were recovered only from the part post‐dating 6500 BP. Earliest testate amoebae assemblages associated with bryophytic and cyperaceous‐rich fen peat are dominated by species in the genera Cyclopyxis and Centropyxis. By 5000 BP, Amphitrema Jraaum, Assulina muscorum, Heleopera sphugni and Hyalosphenia subjaoa become important species as Sphagnum‐rich peat accumulated at the site. Present‐day microtopographic differentiation probably developed during historic time when the site became progressively drier, as indicated by a change of Nebela griseola, N. militaris and Trigonopyxis arcula. Although it is possible to derive quantitative estimates of changing soil moisture conditions from testate amoebae, care should be taken in interpreting results, particularly from non‐Sphagnum‐rich peats, until more is learned about the distribution and ecology of modern faunas.
On the meltwater genesis of drumlins
Authors: SHOEMAKER EDWARD M.
Published: July 2010

Large subglacial cavities in basal ice. the presumed precursors of depositional drumlins, can be created by corrasion from suspended sediment during a large water sheet outburst flood. The cavities are primarily the result of vortex action. For a given flood discharge the corrasion rate of the ice roof increases with water sheet velocity, V, to a power greater than V16/3, Because of ice displacment during a flood, V can vary spatially along a flow line by up to an order of magnitude. The highest velocities normally occur downstream from major bed depressions or near the ice margin. Fields of large drumlins frequently occur at such sites. The process of formation of large subglacial cavities is predicted to be more velocity‐sensitive than the erosion of bedrock. No accurate estimate of water sheet flood volumes can be made at this time but they could be at least an order of magnitude less than the 80 000 km3, which was previously estimated.
Debris structures in basal ice exposed at the margin of the Greenland ice sheet
Authors: KNIGHT PETER G.
Published: July 2010

The basal ice of many glaciers contains debris structures that reflect subglacial processes. Presented here is an unusually clear photograph of ice and debris in the lowest 2 m of the basal layer at the margin of the Greenland ice sheet. The photograph shows ice‐debris relationships and deformation structures that reflect entrainment processes and flow history.
Composition and genesis of glacial hummocks, western Wisconsin, USA
Authors: JOHNSON MARK D. , MICKELSON DAVID M. , CLAYTON LEE , ATTIG JOHN W.
Published: July 2010

Glacial hummocks associated with the Superior Lobe in western Wisconsin are stagnant‐ice features composed of melt‐out till, meltwater‐stream sediment, and flow till. The greater proportion of melt‐out till in these hummocks than in hummocks described elsewhere suggests that a model of extensive, supraglacial reworking of supraglacially released debris does not apply to the western Wisconsin hummocks. Interpretation of melt‐out till in hummock exposures is based on its strong fabric oriented parallel to regional ice‐flow direction. Other features of this melt‐out till include poorly developed stratification (color banding and discontinuous thin sandy lenses), and minor faulting, both of which support a melt‐out origin. We suggest that as stagnant, debris‐rich ice began to melt, supraglacially released debris was deposited as flow till and meltwater‐stream sediment (with some debris‐flow sediment and lake sediment), but as the thickness of supraglacial debris increased, debris melting out at depth was stabilized, allowing features characteristic of melt‐out till to be retained. Because the supraglacial debris was sandy and the stagnant ice was likely at the pressure‐melting point, the supraglacial debris was well drained and did not readily fail and flow. Debris volume in the glacier generally was greater at the glacier margin, but lateral and longitudinal variations within this zone were caused by thrusting, freezing‐on, or ice‐margin fluctuations, which in turn resulted in variations in hummock relief. Ice‐walled‐lake plains are commonly associated with the hummocks and developed where debris volume was small.
A new book on the ‘Ice Age World’ ‐ a pictorial feast and more than a fresher's primer!
Authors: Lowe J. John
Published: July 2010

Andersen, B. G. & Borns Jr., H. W. 1994: The Ice Age World (an introduction to Quaternary history and research with emphasis on North America and Northern Europe during the last 2.5 million years). Scandinavian University Press.
Glacial drainage towards the Mediterranean during the Middle and Late Pleistocene
Authors: ARKHIPOV STANISLAV A. , EHLERS JÜRGEN , JOHNSON ROBERT G. , WRIGHT, Jr. HERBERT E.
Published: July 2010

To a varying degree the Middle and Late Pleistocene ice sheets in northern Eurasia redirected the drainage of major catchments in Europe and western Siberia from the North Sea and Arctic Ocean south to the Caspian, Black Sea, and ultimately the Mediterranean. During the Late Weichselian, glacial meltwater reached the Mediterranean through the Dniepr and Don catchments and to a minor extent through the Danube. During the Warthe Substage of the Saalian, meltwater from the Volga was most likely added. During the Drenthe Substagc of the Saalian the watershed shifted Par to the east, and meltwater reached the Mediterranean also from the Oh. Irtysh, Yenisei, and Tunguska catchments in Siberia. Depending on the extent of the ice sheets, the increase in freshwater supply during deglaciations resulted in reductions of Mediterranean overflow into the North Atlantic. Such overflow reductions may have reduced vapour transport to the ice sheets and thus accelerated wastage.
Glaciotectonic deformation during the Elsterian ice‐sheet advance at the northeastern margin of the Sudetic Foreland, SW Poland
Authors: KRZYSZKOWSKI DARILSZ
Published: July 2010

The glaciotectonic deformations near the northeastern margin of the Sudetic Foreland, SW Poland. were formed during one glacial episode. They are relatively small and are truncated. Deformation structures have no recognizable relationship to the thick Neogene clay in the basement; they have variable relations to the morphology and indicate transverse to opposite directions of the glacial push in very small areas within a distance of 2 to 5 km. This suggests an unusual deformational history. Deformations have probably been created due to sliearing en masse of the anisotropic sediments and during the ice‐sheet advance. Deformation structures have been formed a few kilometres ahead of the curved ice margin, which created ‘glaciotectonic hills’ with strongly differentiated orientations of thrust structures and folds.
Sedimentary and tectonic development of a high‐arctic, thrust‐moraine complex: Comfortlessbreen, Svalbard
Authors: HUDDART DAVID , HAMBREY MICHAEL J.
Published: July 2010

The glaciotectonic processes that have shaped the morphology and structural geology of the Comfortlessbreen thrust‐moraine complex are shown to be largely proglacial in origin, with the development of low‐angle thrusts, nappe‐like structures and folds. The propagation of the deformation has extended into the glacier foreland. A style of deformation called the ‘englacial deformation zone’ explains the incorporation of subglacial debris into the ice by thrusting and subsequent deposition of thrust sheets is inherited from the ice structures. A model for thrust‐moraine development and its possible chronology at Comfortlessbreen emphasizes the role played by glaciomarine sediment in facilitating deformation and also the role of thrusting, rathcr than pushing, in moraine formation. The importance of sediment type in controlling the overall development of the moraine is emphasized and a comparison to illustrate this control is made with neighbouring Uvẽrsbreen.
Oxygen‐isotope record of Late‐Glacial climatic change in western Ireland
Authors: AHLBERG KARIN , ALMGREN ELISABETH , WRIGHT H. E. , ITO EMI , HOBBIE SARAH
Published: July 2010

Oxygen‐isotope profiles for the Late‐Glacial carbonate sediments from Red Bog and adjacent Lough Gur in County Limerick in western Ireland are readily correlated with the classical hiozones delineated on pollen diagrams for the same cores. The estimated summer temperatures of the Bølling/Allerød were as high as those in the early Holocene and are correlated with increasing Milankovitch summer insolation. This warm phase was abruptly terminated in the Younger Dryas cold episode by a depletion of 4% in δ18O, suggesting a summer atmospheric temperature decrease of about 12°C, comparable to that inferred from fossil beetle data. The Younger Dryas phase is attributed to a major cooling of the sea‐surface temperature by a postulated discharge of icebergs similar to that of the Heinrich events, for the icebergs were much more effective than simple meltwater in cooling the sea surface and thus the climate over Europe. Shorter‐term cool phases (Older Dryas. Gerzensee. Preboreal oscillation) are also recognized.
Glacial deposits in northeast Europe — an untapped and unexplored story
Authors: KRZYSZKOWSKI DARIUSZ
Published: July 2010

Ehlers, J., Kozarski, S. & Gibbard, P. (eds) 1995: Glacial Deposits in North‐East Europe
Ferdynandovian Interglacial climate reconstructions from pollen successions, stable‐isotope composition and magnetic susceptibility
Authors: KRZYSZKOWSKI DARILJSZ , BÖTTGER TATJANA , JUNGE FRANK W. , KUSZELL TERESA , NAWROCKI JERZY
Published: July 2010

The Ferdynandovian Interglacial is one of the most controversial Quaternary stratigraphic horizons in Europe. This study concentrates on palaeoclimatic reconstruction of this interglacial based on pollen succession, isotope composition and magnetic susceptibility. The section investigated is located in the open cast mine at Belchatow, central Poland. The lacustrine sequence contains laminated diatomite at the base, which was deposited in deep, meromictic lake, and massive diatomite to calcareous gyttja in its upper part. The latter were deposited in a holomictic lake, which became progressively more shallow. The gradual increase of δ18O values and simultaneous decrease of susceptibility in the lower part of the Ferdynandovian sequence at Belchatow correspond well with climatic amelioration documented by pollen analysis. Simultaneous increase of precipitation of carbonates and its δ13C values correspond well with the increase in biological activity in the lake. Results obtained by isotope investigations showed an increase in the mean annual temperature to a maximum of 7.5°C from the beginning of the interglacial to the first appearance of thermophilous, deciduous trees. The oxygen‐isotope curve does not show any short‐term climatic oscillations. Susceptibility oscillations are somewhat more distinct, but because the main magnetic carrier is greigite deposited on spores of unicellular organisms, they are linked to the concentration of these spores rather than with the climatic oscillations. Twelve secular cycles or their fragments have been recorded in the interglacial sequence by palaeomagnetic investigations, suggesting c. 9600 years of deposition. This corresponds well with the 10 000 years of deposition calculated for the same sequence based on annually laminated diatomites.
Composite stable isotope records from a Late Weichselian lacustrine sequence at Grrenge, Lolland, Denmark: evidence of Allerød and Younger Dryas environments
Authors: HAMMARLUND DAN , BUCHARDT BJØRN
Published: July 2010

Stable oxygen and carbon isotope data from a lacustrine sequence at Grænge, southeast Denmark, revealed distinct cnvironmental changes related to Late Weichselian climatic development in the region. Comparison of isotopic records obtained from sedimentary carbonates and freshwater molluscs enabled reconstruction of changes in the lacustrine environment. The degree of thermal and chemical stratification of the lake was evaluated and supported by pollen data from an earlier study of the site. During the Allerød interstadial, dimictic and stagnant conditions characterized the lake, whereas the stratification was disturbed during thc Younger Dryas stadial probably as a result of deforestation and increased wind impact. The origin of sedimentary carbonates was examined by mineralogic and morphologic studies. A considerable input of clastics and detrital carbonates, associated with pronounced enrichment of18O and13C. wds recorded in the Younger Dryas sediments indicating soil degradation and increased erosion. A climatic warming preceding the Pleis‐tocene/Holocene boundary is clearly reflected in the different stable isotope records and in the lithostratigraphy.
Postglacial emergence and the Tapes transgression, north‐central Kola Peninsula, Russia
Authors: SNYDER JEFFREY A. , KORSUN SERGEY A. , FORMAN STEVEN L.
Published: July 2010

The history of postglacial emergence on the Murman coast, Kola Peninsula, is reconstructed based on twelve new radiocarbon ages from three marine sections and regional shoreline observations. Two pronounced shore levels are recognized below the Late Weichselian marine limit. The lower shoreline (11 ‐16 m a.s.l.) is associated with a transgression dated to 6200–6600 BP, correlative to the Tapes transgression on the Norwegian coastline. The upper shoreline (36–47 m a.s.l.) is not yet dated directly but probably correlates to the Main (Younger Dryas) shoreline. Strandline elevations descend eastward along the Murman coast. Observed emergence trends suggest the greatest regional Late Weichselian glacier load over the west‐central Kola Peninsula rather than in the southern Barents Sea.
Mineral magnetic properties of Late Weichselian‐Holocene sediments from the northwestern Baltic Proper
Authors: SOHLENIUS GUSTAV
Published: July 2010

Mineral magnetic measurements were carried out on twelve sediment cores from the northwestern part of the Baltic Proper. The purpose was to use magnetic properties to correlate sediment sequences and to investigate changes in depositional conditions (e.g. rate of sedimentation and redox conditions). A general lithostratigraphy consisting of five units was established based mainly on mineral magnetic properties. Sediment has been deposited from the time of the Baltic Ice Lake (before 10 300 14C years BP) to the present, i.e. since the Late Weichselian deglaciation. Five of the cores were also investigated by means of biostratigraphical methods and three by 14C dates. Based on the general stratigraphy and hiatuses, variations in sedimentation rate were identified. The occurrence of authigenically formed ferrimagnetic greigite (Fe3S4), mainly in sediments deposited during the brackish Yoldia Sea and Litorina Sea stages, is implied. These sequences are characterized by low S‐ratios and high SIRM/z ratios. Glacial clay, deposited in freshwater during the Baltic Ice Lake stage and the early freshwater phase of the Yoldia Sea stage, seems to be unaffected by diagenetic processes. Gyttja clay, deposited in the Litorina Sea, has significantly lower susceptibility and SIRM than in the underlying clay. Dissolution of magnetic iron oxides (e.g. magnetite and hematite) in an anoxic environment was suggested as an explanation.
The last deglaciation of the Franz Victoria Trough, northern Barents Sea
Authors: LUBINSKI DAVID J. , KORSUN SERGEY , POLYAK LEONID , FORMAN STEVEN L. , LEHMAN SCOTT J. , HERLIHY FRANCES A. , MILLER GIFFORD H.
Published: July 2010

A study of two piston cores and a 3.5 kHz seismic profile from the Franz Victoria Trough provides new stratigraphic, stable isotopic and foraminiferal AMS 14C data that help constrain the timing of ice‐sheet retreat in the northern Barents Sea and the nature of the deglacial marine environment. Silty diamicton at the base of each core, interpreted as till or ice‐marginal debris flow, suggests that the Barents ice sheet was grounded at the core sites (470 m water depth). Eight AMS 14C dates on sediment overlying the diamicton indicate that the ice sheet retreated from both core sites by 12.9 ka and that postglacial sedimentation began 10 ka ago. These dates, combined with a recently published 14C date from a nearby core, suggest that the Franz Victoria Trough may not have been deglaciated until c. 13 ka, 2000 years later than modeled ice‐sheet reconstructions indicate. In the trough, oxygen isotopic ratios in planktonic foraminifera N. pachyderma (sinistral) were 0.5–0.750, lower during deglaciation than after, probably as a result of ice‐sheet and/or iceberg melting. Foraminiferal assemblages suggest that Atlantic‐derived intermediate water may have begun to penetrate the trough c. 13 ka ago.
Early Holocene insect and plant remains from Jameson Land, East Greenland
Authors: BÖCHER JENS , BENNIKE OLE
Published: July 2010

Fluvial and deltaic sediments from Jameson Land in East Greenland contain the first record of the leaf beetlePhratora of.polaris, not presently found in Greenland; the ground beetleBembidion grapii, north of this species' present northern range limit; and the true bugNysius gruenlandieus. In addition, there is a rather diverse flora. All of these records are in sediments of Early Holocene age. We suggest that most of these animals and plants immigrated to East Greenland in the Early Holocene by long‐distance chance dispersal, mostly from northwest Europe. The environment was physiognomically similar to that of today, butSalix areticaandCassiope tetragonuthat are important dwarf shrubs today had not yet immigrated.