bluuebunny/crossref_metadata_2025 huggingface dataset:
Late glacial and Holocene vegetation history at Governor Bog, King Valley, western Tasmania, Australia
Authors: Colhoun Eric A. , van de Geer Guus , Fitzsimons Sean J.
Published: February 2007

Excavation of peat and clay filling a sink hole has provided a relatively long late glacial to Holocene pollen/vegetation record for the King Valley. The record shows a change from alpine herbland, Microstrobos scrub and heath at 13 ka BP to Eucalyptus subalpine woodland. Phyllocladus‐Nothofagus rainforest succeeded after 12.5 ka BP but degenerated to scrub rainforest after 11 ka BP, when Lagarostrobos franklinii expanded. The sequence of local changes occurred while the sink‐hole lake was being rapidly infilled and converted to topogenous peat around 12 ka BP.

Examination of the timing of changes in vegetation associations in other pollen profiles from different altitudes in western Tasmania indicates that many of the changes are non‐synchronous and cannot be related directly to climatic events. They probably reflect the effects of both biological and local environmental factors.

The major regional climatic change from alpine to temperate conditions on the lowlands occurred ca. 13 ka BP. Demonstration of non‐synchronous changes in the late glacial to early Holocene pollen/vegetation associations at several sites contrasts with the view of Markgraf et al., who infer synchronous changes related to climate. There are no indications in the pollen/vegetation sequence of either Allerød or Younger Dryas events in western Tasmania.
Quaternary volcanic ash zones on the Iceland Plateau, southern Norwegian Sea
Authors: Sjwøholm Jorunn , Sejrup Hans Petter , Furnes Harald
Published: February 2007

Four Quaternary volcanic ash zones in the southern Norwegian Sea have been investigated in core P57‐7 from the Iceland Plateau. Both the geochemical composition and morphological variation of each ash layer have been studied. The four volcanic ash zones appear in the light oxygen isotope stages 1, 5, 7 and 11. The ash zones are composed of transparent platy grains, light brown transparent grains, brown blocky and black blocky grains and white/transparent pumice, and each zone shows a distinct stratigraphic evolution. The geochemical results show a mixture of basaltic and silicic grains in each ash zone, and that each zone contains grains from more than one eruption. The geochemical investigations strongly suggest that all the ashes are derived from Iceland. The youngest ash zone includes two layers, which based on their geochemical composition and stratigraphic position are correlated with the 14C‐dated Vedde Ash (10 600 yr BP) and Saksunarvatn Ash (9 100 yr BP). Possible sources on Iceland for these layers are discussed.
Holocene alluviation and land‐use change on Callaly Moor, Northumberland, England
Authors: Macklin M. G. , Passmore D. G. , Stevenson A. C. , Cowley D. C. , Edwards D. N. , O'Brien C. F.
Published: February 2007

Archaeological survey and palaeoenvironmental investigations in Coe Burn, Callaly Moor, Northumberland, have examined the chronology and nature of prehistoric and historic land‐use change in a small upland river catchment. These studies have revealed an intensively used landscape with evidence of late Neolithic to Bronze Age, medieval and post‐medieval land use and settlement. Two episodes of valley floor alluviation are identified and dated to the middle‐late Bronze Age and post‐medieval periods. Magnetic mineral and geochemical analyses of fine sediments from the older alluvial fill show it to contain a high proportion of topsoil, which is believed to have been produced by soil erosion resulting from Bronze Age tree clearance and cultivation. Deposition of the younger alluvial fill (post AD 1500) was associated with the inwash of relatively unweathered bedrock generated by coal mining in the catchment. It is demonstrated that by integrating archaeological field survey with off‐site palaeoenvironmental investigations a much fuller picture of human activity and land‐use change has emerged than otherwise would have been the case. Studies of this type may be particularly useful in other upland river catchments where archaeological survival is limited or poor.
The glacigenic deposits of Western Lleyn, North Wales: Terrestrial or marine?
Authors: McCarroll Danny , Harris Charles
Published: February 2007

This paper describes a complex sequence of glacigenic sediments occupying a faultbounded depression at Aberdaron Bay, western Lleyn. The sequence offers an insight into sedimentary environments during deglaciation of the Irish Sea Basin. A lower stratified diamict association (LDA) containing contorted units of fine sand/silt and displaying strong, consistent clast fabrics, is overlain by an upper diamict association (UDA) with weaker fabrics and extensive sand and gravel layers and channel fills. Certain characteristics of the sequence can be explained by a glacimarine depositional model, but there are several problems. In particular, the geometry of the sediments is difficult to explain without recourse to the melting of buried ice. An alternative model that overcomes these problems involves the decay of a terrestrial glacier containing reworked marine sediments. Supraglacial sediment flows released during decay of thinner ice covering the surrounding hills (UDA) would have rapidly buried a thick stagnant ice mass in the Aberdaron depression, facilitating slow melting and release of basal meltout till (LDA). A model is presented that accounts for the stagnation and in situ decay of a debris‐rich Irish Sea glacier, and which could explain many of the deposits and landforms surrounding the Irish Sea Basin without recourse to high relative sea‐levels.
Micromorphological aspects of glaciolacustrine sediments in Northern Patagonia, Argentina
Authors: Van Meer Aap J. M. Der , Rabassa Orge O. , Evenson Dward B.
Published: February 2007

In this study the sedimentology, micromorphology and structure of four deformation es in end moraines or near‐end moraine settings are presented. Micromorphology has proven be a powerful tool in the interpretation of the sediments.

The four sites are related to three of the four major glaciations known from this part of Patagonia: Nahuel Huapi, Anfiteatro and Pichileufú. All four sites are characterised by glaciolacustrine vironments in which sedimentation occurred at least partly on and/or against dead ice. With the exception of one section in the San Martin de los Andes area, where deformation occurred active ice‐push, all major disturbances (faults and folds) are the result of dead ice collapse. Comparison with micromorphological observations on basal tills shows that the sediments all lack clear subglacial imprint.
Lateglacial and Holocene climate and soil erosion in southeastern France: A case study from Etang du Pourra, Provence
Authors: Laval H. , Medus J. , Parron C. , Simonnet J. P. , Trement P.
Published: February 2007

A synthesis of pollen evidence from Etang du Pourra, a small pond in Rhodanian Provence, France, complemented by new sedimentological, mineralogical and palynological data allow a reassessment of the Lateglacial‐Holocene vegetation and climatic history of the area. The Etang du Pourra succession is shown to consist of two parts; the lower part dates from the Lateglacial and the upper reveals the Holocene pollen‐stratigraphic succession typical of the region. In the Lateglacial, a humid and cooler phase is recorded before the Younger Dryas conditions progressively set in. In the Holocene succession, the consequences of human modifications on the environment are clearly visible in changes in mineralogy and pollen stratigraphy.
Quantitative climate reconstruction from pollen data in the Grand Duchy of Luxembourg since 15 000 yr BP
Authors: Guiot J. , Couteaux M.
Published: February 2007

Monthly temperature and precipitation estimates for the period 15000–2000 yr BP are statistically derived from pollen analytical data obtained from a site near Echternach, Luxembourg. A continuous warming trend of over 10°C is recorded for the period 10500—8000 yr BP, along with a rise in precipitation of 500 mm. A fairly constant temperature characterised the period between 8000 and 2000 yr BP, though an episode of slight temperature decrease (‐2°C) occurred at about 4500 yr BP. The most humid intervals seem to have been at around 9000–7000 and 5000–3000 yr BP (principally during the warm season: more continental influence). In contrast with results obtained from more southerly sites, the ‘Older Dryas’ climatic reversal is clearly recorded at Echternach slightly before 12000 yr BP. It is marked by a cooling in July temperature of about 4°C and a decrease in monthly precipitation of about 30 mm (40%).
Palaeoenvironments of the Hoxnian Nar Valley Clay, Norfolk, England: Evidence from an integrated study of diatoms and ostracods
Authors: Mitlehner Alexander G.
Published: February 2007

Diatoms and ostracods from the Nar Valley, west Norfolk, England are analysed with a view to establishing marine and freshwater palaeoenvironments of the Hoxnian interglacial Stage. No microfossils were recovered from the non‐marine facies, but rich assemblages of both fossil groups were extracted from the marine Nar Valley Clay and these, together with associated sedimentological evidence, indicate that the environment of deposition changed from a relatively nearshore, muddy shelf setting, to one that was more littoral and subject to higher current regimes, with salinities remaining at normal marine levels through both depositional phases. It is suggested that this sequence may reflect a regressional phase towards the close of the Hoxnian Stage, with palaeotemperature evidence from at least one ostracod species suggesting a warmer climate than at present. Non‐recovery of microfossils from some of the samples analysed is attributed to unfavourable palaeoenvironmental conditions and/or post‐depositional ground‐water percolation.
The long‐singular ridges of the Halland Coastal Moraines, South‐Western Sweden
Authors: Fernlund Joanne M. R.
Published: February 2007

Radiocarbon dates of shells from the long singular ridges belonging to the Halland Coastal Moraines indicate that the ridges are younger than 12 400 yr BP, whereas according to the existing chronostratigraphy of western Sweden, the area was ice free before 12 700 yr BP. The ridges are interpreted as push moraines and not deposits of a stationary ice margin. The chronostratigraphy of western Sweden seems to need revision; however, further study is necessary before it is possible to present a new model.
The stratigraphical significance of deer species in the cromer forest‐bed formation
Authors: Lister Adrian M.
Published: February 2007

Deer species provide a valuable biostratigraphical tool through Cromer Forest‐bed times, due particularly to species turnover between the Early and early Middle Pleistocene. This study is based on the reidentification of 348 fossil antlers. The provenance of most large mammal fossils from the CF‐bF, collected over 150 years, was recorded only by the nearest coastal village. None the less, analysis of the cervid taxa by these ‘localities’ reveals interesting patterns. The fauna of the West Runton Freshwater Bed is of early Middle Pleistocene complexion, and that from the foreshore at East Runton is of Early Pleistocene. Pure or nearly pure early Middle Pleistocene assemblages also occur at Kessingland‐Pakefield and at Trimingham. At Overstrand, Sidestrand, Mundesley, Bacton and Happisburgh, there is a mixture of Early and early Middle Pleistocene elements. Analysis of Savin's data shows that fossils of earlier species were generally found further down the beach than those of later ones. Late nineteenth century geological surveys, made when bone collecting was at its peak, give additional information about fossil horizons, which in several cases can be related to modern stratigraphical units. Most Early Pleistocene large‐mammal bones came from Pastonian conglomerates, in contrast to small‐mammal and molluscan assemblages mostly extracted from Pre‐Pastonian Crag. However, the diversity of Early Pleistocene CF‐bF cervid species in comparison with continental faunas, and their pattern of distribution between sites, suggests they may span more than one chronostratigraphic stage. Early Middle Pleistocene assemblages came from strata now referred to the Cromerian, and the differing proportions of taxa between sites provide limited evidence of time‐transgression.
Deglaciation of the younger dryas or Loch Lomond Stadial ice‐field in the northern Highlands, Scotland
Authors: Bennett Matthew R. , Boulton Geoffrey S.
Published: February 2007

When viewed from the air, Scottish ‘hummocky moraine’ can be resolved into a series of linear ridges that resemble those found at the margins of actively retreating glaciers today. Recent work has supported the interpretation of these linear ridges as ice‐marginal landforms and the authors believe that the majority of ‘hummocky moraine’ deposits can be interpreted in this way. Consequently the pattern of deglaciation can be established fairly precisely from the pattern of linear ridges. This approach is applied to the landforms of the northern part of the Loch Lomond Stadial ice‐field in order to reconstruct the regional pattern of deglaciation. This leads to important inferences about the significance of topographic control during deglaciation and more importantly it provides fresh insight into the environment of the British Isles during the Loch Lomond Stadial.
Late quaternary stratigraphy and geochemistry of the R47 section, Rouge River Basin, south‐central Ontario, Canada: Correlation with Scarborough Bluffs
Authors: Mahaney W. C. , Slowpoke R. G. V. Hancock
Published: February 2007

Quaternary glacial diamictons in section R47, overlying Ordovician shale in the Rouge River Basin of south‐central Ontario, are considered to be representative of older and younger Wisconsinan glacial diamictons in the field area. Field characteristics, clast composition, mineralogy, particle size and geochemistry permit delineation of two units within the sequence and subdivision of deposits that correlate with Sunnybrook and Halton diamictons of Wisconsinan age. No Wisconsinan interstadial deposits are present in the section; however, outwash sandy gravel capping the Halton diamicton was probably emplaced by a high‐energy stream draining into Lake Iroquois just prior to the incision of the Rouge Valley in the later Wisconsinan (ca. 11 000‐12 000 yr BP). A buried palaeosol, which developed in this sandy gravel and in overlying aeolian sediment, shows partial leaching of carbonates and a slight increase of clay in the palaeosol solum. The main clay‐mineral transformations in the buried palaeosol appear to involve the degradation of illite and illite‐smectite accompanied by the production of vermiculite and minor amounts of chlorite. The ground soil capping the buried palaeosol is formed in colluvium emplaced 200 ± 80 yr BP following a local forest fire; the ground soil Ahk horizon gives an age of 4000 yr in the future, probably as a result of nuclear bomb testing effects on modern radiocarbon. The presence of an A/C profile in the ground soil system, although thin, indicates that surface soils may form rapidly.

The geochemistry of the two Wisconsinan diamictons shows similar calcite and SiO2‐corrected mean element concentrations, with slightly elevated levels of Ca, Sr, Hf and Lu in the younger deposit. Both diamictons are geochemically quite different from the shale bedrock in the area, indicating that the bulk of transported sediment came from outside the area.
Glacier readvances in the Andes at 12 500–10 000 YR BP: Implications for mechanism of Late‐glacial climatic change
Authors: Clapperton Chalmers M.
Published: February 2007

Radiocarbon dates from two sites in the Andes (Ecuador and Peru) confirm that glaciers culminated a readvance after 11 000 yr BP. A moraine stage, equivalent in altitude and position relative to existing glaciers, is present in most glacierized ranges, but its age is equivocal. Broadly limiting dates from Colombia and Peru suggest that the stage may be Late‐glacial, as it is younger than 12100 yr BP, but formed before the early Holocene; in southern Chile a comparable moraine stage is older than ca. 9100 yr BP. Andean glaciers appear to have advanced at least twice during the Late‐glacial interval.

Glacier reconstruction from these moraine limits suggests depression of the equilibrium line altitude by at least 300–400 m in the northern and north‐central Andes, and possibly less than this farther south.

Late‐glacial climatic change occurred globally and possibly reflects North Atlantic temperature and circulation changes forced by deglaciation of the northern ice sheets, migrations north and south of the Atlantic Polar Front, and the switching off and on of a ‘dust pump’ in low midlatitudes.
On the history of the Late Devensian Lake Sparks in southern Fenland, Cambridgeshire, England
Authors: West Richard G.
Published: February 2007

A section in a gravel quarry at Somersham, Cambridgeshire, has revealed evidence for a lake, named Lake Sparks, in Fenland during the Late Devensian substage of the Pleistocene. Varved sediments were deposited in this lake over a minimum period of ca. 65 yr. The varved clays contain red diamicton clasts, interpreted as dump, delivered to the area by icebergs or floes from the ice‐front in the Wash that deposited the Hunstanton Till. The lake is therefore considered a result of impounding by the Late Devensian ice advance on the east coast. A small number of pale varves have a characteristic structure indicating increased calcite deposition in the summer. They are interpreted as a result of cooler summers with reduced gelifluction from the surrounding Jurassic (Ampthill) Clay. Such gelifluction introduced a mudflow into the varved sequence at the southern end of the section. Pollen analysis confirms the derivation of the clays from the surrounding Ampthill Clay.

The varved clays are succeeded by fluviatile sediments related to a delta building into the lake from the north. The delta sediments show periodic influx of sand into the lake interrupted by quiet periods with the development of Chara meadows. A thin spread of fluviatile gravels succeed the delta sediments, indicating the development of a braided river plain as the lake drained on the melting of the Late Devensian ice. This was followed by permafrost development, with the formation of thin thermal contraction cracks and coversand deposition. Later, degradation of the permafrost was associated with the formation of diapirs and a solifluction mantle, and incision of the fluviatile and lacustrine sediments took place. Flandrian peat and marl later filled the valley so formed.

A radiocarbon date of 18310 yr BP from Salix leaves in a drift mud at the top of channel sands preceding lake sediment, in a neighbouring section, confirms the relation of the lake to the Late Devensian ice advance.

The significance of the Late Devensian sediments at Somersham lies in the information they give on the timing and variety of processes related to drainage and ice movement in the period before, during and after the ice advance to the Wash. A period of low deposition rate in the lake was followed by rapid delta sedimentation and lake drainage, with implications for climatic change.
Pattern of deglaciation of the last (Late Devensian) Scottish ice sheet: Evidence from ice‐marginal deposits in the Dee valley, Northeast Scotland
Authors: Brown Iain M.
Published: February 2007

The mode of deglaciation of the last Scottish ice sheet is assessed from evidence provided by geomorphological mapping and sedimentology. Ice‐marginal deposits in the Dee valley have a distinctive morphological expression and a characteristically varied sedimentology that strongly resembles those from subpolar glaciers. The deposits tend to occur in certain topographic situations which can be accounted for by compression of ice near the margin and formation of an ice‐cored supraglacial land system. A series of recessional stages of the ice‐front can be mapped demonstrating that active retreat occurred. However, additional evidence shows there was probably a thin marginal zone of stagnant ice. Recessional stages are inferred to be stillstands that are considered to be topographically controlled rather than related to climate. Development of the supraglacial land system during deglaciation suggests that the ice sheet had a polythermal basal regime with a cold‐based margin. This implies that deglaciation took place in northeast Scotland while the climate remained cold, probably due to a precipitation deficit, which agrees well with chronostratigraphic data.
Glaciomarine deltaic deposition and ice‐marginal tectonics: The ‘Loch Don Sand Moraine’, Isle of Mull, Scotland
Authors: Benn Douglas I. , Evans David J. A.
Published: February 2007

Detailed descriptions are given of sediments exposed in the ‘Loch Don Sand Moraine’, Isle of Mull, Scotland. Two distinct sediment‐landform associations occur within the ‘moraine’: (i) a Gilbert‐type glaciomarine delta complex graded to ca. 34 m Ordnance Datum; and (ii) thrust moraines consisting of deformed sands and silts. Whereas previous studies have attributed the ‘moraine’ to a single glacial readvance, this paper shows that the delta and the thrust moraines formed during ice‐sheet deglaciation and the Loch Lomond Readvance, respectively. Depositional conditions and the palaeoenvironment for each stage of ‘moraine’ formation are reconstructed. During the Loch Lomond Readvance, till deposition and thrust moraine formation appear to have been controlled by drainage conditions in the marginal zone of the glacier.
Geochemical control of magnetite dissolution in subarctic lake sediments and the implications for environmental magnetism
Authors: Snowball Ian F.
Published: February 2007

Geochemical and mineral magnetic studies of lake sediments from the Kårsa valley in north Sweden demonstrate that down‐core variations in magnetic properties have been determined by post‐depositional magnetite dissolution rather than by sediment source changes. A low sediment accumulation rate during times of climatic amelioration combined with a higher organic carbon content produced intense reducing conditions with almost complete magnetite loss. An increase in the sedimentation rate and a reduction in the organic carbon content, primarily due to glacier reformation, allowed magnetite preservation. Thus the mineral magnetic profiles record lake sediment palaeoredox conditions brought about by climate change. This new interpretation of mineral magnetic transformations in freshwater sediments may have far reaching implications for other mineral magnetic studies concerned with the alternation between glacial (stadial) and interglacial (interstadial) episodes during the Quaternary period.
Sea‐cave temperature measurements and amino acid geochronology of British Late Pleistocene Sea stands
Authors: Hollin John T. , Smith Franklin L. , Renouf John T. , Jenkins D. Graham
Published: February 2007

‘Calibrating’ amino acid ratios with uranium‐series dates requires an accurate knowledge of current mean annual temperatures (CMATs) over the region studied. To measure these, test‐tube sized ‘diffusion sensors’ were emplaced for 1 year (in 1984, 1985 and 1986), both outside and inside Minchin Hole sea‐cave in South Wales and Belle Hougue sea‐cave in Jersey, both of which have yielded Oxygen Isotope Substage 5e uranium‐series ages on speleothems. Our outside temperatures agreed with meteorological ones. Our inside temperatures were over 1°C lower. To allow for this, a mean of ‘empirical’, ‘linear’ and ‘parabolic’ epimerisation calculations suggests that ratios from molluscs inside the caves should be multiplied by over 1.1 for comparison with outside ratios. This raises Bowen et al.'s ‘Pennard’ stage ratios from inside Minchin (and Bacon) Hole up towards the ‘Unnamed’ stage ratios outside, and suggests that the Unnamed sites are also from Oxygen Isotope Substage 5e, as proposed by Proctor and Smart. The same conclusion is reached more strongly by comparisons with the ratios and temperatures inside Belle Hougue to the south, and at Eemian (assumed 5e) sites in The Netherlands, Germany and Denmark to the east. The Pennard ratios from outside sites may provide further evidence for global sea stands close to the present level later in Oxygen Isotope Stage 5.
A Late Weichselian stable isotope stratigraphy compared with biostratigraphical data: A case study from southern Sweden
Authors: Hammarlund Dan , Lemdahl Geoffrey
Published: February 2007

Late Weichselian lake sediments from a site in southern Sweden, were analysed for stable carbon and oxygen isotopes, as well as plant macrofossils and insect remains. By comparison of independent data sets, general climatic changes were demonstrated. Lithological, chemical and stable isotope data reveal two significant climatic oscillations at ca. 12 200–12 000 and ca. 11 000–10 200 yr BP respectively. Continental climatic conditions, indicated by evaporative enrichment of 18O in lake marl, characterise parts of the early lake history, including the Older Dryas Stadial. Distinct variations of δ13C in organic material is discussed in terms of climatically induced changes in lake‐water chemistry. Different types of photosynthetic assimilation of dissolved inorganic carbon is proposed as a contributing factor influencing lake marl δ13C. The universal application of a positive correlation between lake marl δ18O and mean annual air temperature is questioned.

Quantifications of mean summer and winter temperatures based on beetle analysis show a climatic optimum around 12 000 yr BP, a marked cooling around 11 000 yr BP and a strong amelioration at ca. 10 200 yr BP. These climatic events were accompanied by distinct changes in aquatic vegetation. Plant macrofossil and insect analyses indicate an open vegetation during the entire period studied.

Biostratigraphical data reflecting local limnic and terrestrial vegetation and regional climate facilitate the interpretation of stable isotope data.
Climatic deterioration and the end of the Gortian Interglacial in sediments from Derrynadivva and Burren Townland, near Castlebar, County Mayo, Ireland
Authors: Coxon Peter , Hannon Gina , Foss Peter
Published: February 2007

Pollen and macrofossil analyses of two sequences of organic sediment in western Ireland have allowed the recognition of the latter parts of the Gortian Interglacial, a Middle Pleistocene temperate stage. The palaeobotanical information from the two sites identifies the preservation of partial sequences from the Gortian Interglacial (believed to be the equivalent of the Hoxnian Stage of Britain and the Holsteinian of Europe). The pollen and macrofossil data from one of the sites, Derrynadivva, span the middle and latter parts of the temperate stage. The results show that fire influenced the vegetation throughout the middle part of the temperate stage, and the termination of the organic depositional sequence appears to have been due to environmental deterioration. The former is identified through the abundant occurrence of charcoal in the sediments, whereas the latter is apparent in the sediment sequence and in the reworking of thermophilous pollen types into the upper part of the deposit. The second site, Burren Townland, records only part of the later zones of the interglacial, but the ericaceous assemblages of the latter part of the Gortian Interglacial are well developed and well preserved. Macrofossil analyses and scanning electron microscopy work on the pollen at the latter site has allowed the recognition of Rhododendron ponticum, adding to previous records of this species, which now has a very disjunct European distribution.
The Würmian Late‐glacial in Iowland Switzerland
Authors: Ammann B. , Lotter A. F. , Eicher U. , Gaillard M.‐J. , Wohlfarth B. , Haeberli W. , Lister G. , Maisch M. , Niessen F. , Schlüchter Ch.
Published: February 2007

A synthesis is provided of Late‐glacial (14‐9 ka BP) environmental changes in lowland Switzerland (the ‘Swiss Plateau’). The chronology of deglaciation and subsequent developments in vegetation cover in the area are summarised. The sequence of climatic variations experienced in the region during the Late‐glacial is then described and a curve representing the main palaeotemperature variations is presented.
Wisconsinan Late‐glacial environmental change in southern New England: A regional synthesis
Authors: Peteet D. M. , Daniels R. , Heusser L. E. , Vogel J. S. , Southon J. R. , Nelson D. E.
Published: February 2007

A synthesis of vegetational and climatic history during the Wisconsinan Late‐glacial (13‐9 ka BP) is presented for the southern New England region. The interpretations are based on a number of pollen‐stratigraphical investigations supported by plant macrofossil data. Chronology is based partly on AMS dates of plant macrofossils. Reference is made briefly to the controversial nature of the evidence for deglaciation in the region. A curve representing mean July temperature changes in the region during the period 13‐9 ka BP is provided.
Patterned fen development in northern Scotland: developing a hypothesis from palaeoecological data
Authors: Charman Daniel J.
Published: February 2007

The recent discovery and description of patterned fens in Scotland has raised questions about their origins and development. A series of possible developmental models has been derived which are tested using data from a well‐developed site in Sutherland, northern Scotland. The site morphology indicates that the fen has developed over a more complex subpeat topography and that the present‐day features are unrelated to the original mineral surface. Stratigraphical information together with radiocarbon dates and pollen age estimates suggest that the mire developed initially in one, perhaps two, narrow gullies as poor fen peats from the early tenth millenium BP. The mire then spread on to surrounding slopes with the onset of ombrotrophic peat accumulation, where the most recent basal age estimate is ca. 3500 yr BP. Poor fen peats extending to the surface began growth at ca. 2850 yr BP, once this ombrotrophic peat cover was complete. A reconstruction of mire conditions based on macrofossil, pollen and other microfossils shows the nature and timing of these changes in more detail. The findings show that the existing models of patterned fen development are not applicable to the Scottish systems. Instead, the poor fen systems are recent developments, which may overlie extensive earlier peat deposits of ombrotrophic character, and are unrelated to earlier peat development. The site has probably developed as a result of localised hydrological changes within the underlying peat body and mineral base, resulting in increased volume and quality of the water supply. It is suggested that this may be by the development and emergence of sub‐peat pipes at the head of a suitable slope.
Modelling ice‐sheet sensitivity to late weichselian environments in the svalbard‐barents sea region
Authors: Siegert Martin J. , Dowdeswell Julian A.
Published: February 2007

Ice‐proximal sedimentological features from the northwestern Barents Sea suggest that this region was covered by a grounded ice sheet during the Late Weichselian. However, there is debate as to whether these sediments were deposited by the ice sheet at its maximum or a retreating ice sheet that had covered the whole Barents Sea. To examine the likelihood of total glaciation of the Late Weichselian Barents Sea, a numerical ice‐sheet model was run using a range of environmental conditions. Total glaciation of the Barents Sea, originating solely from Svalbard and the northwestern Barents Sea, was not predicted even under extreme environmental conditions. Therefore, if the Barents Sea was completely covered by a grounded Late Weichselian ice sheet, then a mechanism (not accounted for within the glaciological model) by which grounded ice could have formed rapidly within the central Barents Sea, may have been active during the last glaciation. Such mechanisms include (i) grounded ice migration from nearby ice sheets in Scandinavia and the central Barents Sea, (ii) the processes of sea‐ice‐induced ice‐shelf thickening and (iii) isostatic uplift of the central Barents Sea floor.
Pliocene—pleistocene boundary in the Kleszczów Graben at Belchatów, central Poland
Authors: Krzyszkowski D. , Szuchnik A.
Published: February 2007

The Pliocene‐Pleistocene boundary, defined using pollen analysis, has been recorded in sections at the Belchatów outcrop, Kleszczów Graben, central Poland. The boundary is located at the top of the green clay subunit of the Tertiary Clayey‐sandy unit. A pollen flora of Reuverian C type, dominated by pine, 10–20% of ‘Reuverian elements’ and scarce thermophilous Tertiary trees, was found directly below this subunit. Cold stage floras of Praetiglian type were, in turn, recorded in the Łekińsko Formation, lying directly on the green clays. The Pliocene—Pleistocene transition at Belchatów demonstrates the characteristic features of this boundary in western Europe, that is, the disappearance of Tertiary thermophilous tree pollen taxa, followed by a cooling to open‐forest or forest‐steppe conditions. Both pollen analysis and geological data suggest continuous sedimentation at least from the Upper Pliocene to the Prae‐Tiglian, with no change of sediment sources and no marked hiatuses. The fluvial deposits of the Praetiglian Łekińsko Formation, although Pleistocene in age, mark a final period in the Tertiary evolution of the Kleszczów Graben. Later, there is a hiatus to the deposition of the first glacigenic sediments in the region possibly of Elsterian age.
Quaternary stratigraphy of the buried valleys of the lower Red Deer River, Alberta, Canada
Authors: Evans David J. A. , Campbell Ian A.
Published: February 2007

The Quaternary fills of the buried valleys of southern Alberta and Saskatchewan have provided a wealth of information for the reconstruction of the glacial‐interglacial record of the western plains of Canada, and this paper reports on the previously unstudied stratigraphy of the buried Calgary Valley and its former tributaries in the lower Red Deer River area. We attempt to differentiate Empress Group sediments, which potentially relate to pre‐glacial, interglacial/ interstadial and post‐glacial lake and river deposition, using sedimentology, stratigraphy and palaeoecology. Twenty‐nine stratigraphical logs indicate that Empress Group sediments have infilled a considerably large area of badlands and tributary coulees that once drained into the Calgary Valley, located 15 km to the north of Dinosaur Provincial Park. Radiocarbon dates of 52.4 ka, 27.4 ka and > 42.4 ka and glacially modified quartz grains suggest that at least some of the valley fills date to interglacial or interstadial periods and may be mid‐Wisconsinan in age. However, outcrops of an older till overlying other valley fills suggest that the buried valleys were only partially excavated during interglacials/interstadials and that older (even pre‐glacial) sediments could have survived. Subglacial channels, recognisable on air photographs, largely coincide with buried valley positions due to the preferential excavation of the Quaternary sediment by meltwater and are filled with post‐glacial lake sediment from which a radiocarbon date of 16 ka BP was obtained. Pre‐glacial and glacial/post‐glacial Empress Group sediments are lithologically indistinct but cover a large time span in southern Alberta.
Direct comparison of UK temperatures and Greenland snow accumulation rates, 15000—12000 yr ago
Authors: Lowe J. J. , Coope G. R. , Sheldrick C. , Harkness D. D. , Walker M. J. C.
Published: February 2007

A palaeotemperature record based on fossil coleopteran evidence and dated by accelerator mass spectroscopy (AMS) 14C determinations on plant macrofossils has been obtained for the last glacial‐interglacial transition from the site of Gransmoor in eastern England. Calibration of the radiocarbon measurements enabled a direct comparison to be made between this palaeotemperature curve and the snow accumulation record from the GISP‐2 Greenland ice‐core. The similarity between the two data sets suggests a degree of correspondence in the pattern and timing of climatic change in Greenland and the British Isles at the end of the last cold stage.
The vertical dimensions of Late Devensian glaciation on the mountains of Harris and southeast Lewis, Outer Hebrides, Scotland
Authors: Ballantyne Colin K. , McCarroll Danny
Published: February 2007

On North Harris and southeast Lewis a weathering limit separates glacially‐moulded bedrock on low ground from frost‐shattered bedrock and blockfields on high plateaux. Analysis of the depths of horizontal stress‐release joints demonstrates significant contrasts in bedrock weathering above and below this boundary, and the survival of gibbsite only in soils above the weathering limit indicates that it represents the upper limit of Late Devensian glacial erosion. The weathering limit declines regularly in altitude on either side of the former ice shed, and is therefore interpreted as a periglacial trimline defining the upper limit of a locally‐nourished ice mass at its maximum extent, rather than a former thermal boundary between protective cold‐based and erosive warm‐based ice. Calculated basal shear stress values are consistent with this interpretation. The configuration of the trimline indicates that at the last glacial maximum the area supported an ice cap that achieved a maximum altitude of ca. 700 m above present sea level and declined in altitude to the west‐northwest and east‐southeast at an average gradient of ca. 20 m km−1. Extrapolation of the dimensions of this ice cap suggests that it terminated ca. 7–10 km west of the present coast of Harris, and was confluent with mainland ice a short distance east of the present coastline.
The back‐barrier and barrier depositional history of Romney Marsh, Walland Marsh and Dungeness, Kent, England
Authors: Long Antony J. , Innes James B.
Published: February 2007

Previous stratigraphical investigations of Romney Marsh have tended to be local in scale, and this has hindered efforts to establish a unifying stratigraphical framework for this area. This paper addresses this problem, by describing the results of a 12‐km transect across Romney Marsh, linking previously studied back‐ and fore‐marsh sites (Horsemarsh Sewer and Broomhill respectively), and presenting additional pollen, diatom and radiocarbon data from an intermediate, mid‐marsh site (Brookland). One main organic unit is recorded across much of Romney Marsh, although its age, altitude and composition varies. Microfossil and radiocarbon data from Brookland and elsewhere on Romney Marsh show that this organic unit accumulated under a general removal and return of marine conditions that took place between ca. 5100 and 2000 yr BP.

A recently proposed model of barrier development is used to investigate the history of back‐barrier sedimentation in Romney and Walland Marshes. This model suggests a three‐phase life‐history for gravel barriers, which consists of initiation, stability and breakdown. Although there are problems in relating back‐barrier deposits directly to barrier dynamics, nevertheless the Romney Marsh data do, for the most part, agree with the expected number and sequence of sea‐level tendencies predicted by this model. The back‐barrier stratigraphical data suggest that initiation, stability and breakdown of the Dungeness foreland occurred between ca. 6000 and 5000 yr BP, 5000 and 2000 yr BP and 2000 yr BP and present, respectively.
Late Pleistocene deposits at Block Fen, Cambridgeshire, England
Authors: West R. G. , Peglar S. M. , Pettit M. E. , Preece R. C.
Published: February 2007

Organic sediments in a gravel quarry at Block Fen, Cambridgeshire, form a sheet dividing lower from upper gravels. Analyses of pollen, macroscopic plant remains and molluscs from these organic sediments are presented. They indicate the presence of temperate freshwater and slightly brackish fine floodplain sediments, which, on the basis of the palaeobotany, are correlated with the temperate Ipswichian Stage. The freshwater sediments, ascribed to Ipswichian substage IIb, occur at ca. −3 m OD. Marine‐influenced tidal sediments, ascribed to Ipswichian substage III, occur at ca. −6 m OD. No evidence was found for the presence of more than one temperate stage in the sequence. The lower gravels are then correlated with the cold Wolstonian Stage and the upper gravels with the cold Devensian Stage. In contrast to the woodland environments indicated by the palaeobotany of the Ipswichian organic sediments, post‐Ipswichian pollen diagrams and macroscopic plant remains in the upper suite of sands and gravels indicate open tree‐less vegetation typical of the cold Devensian Stage. They also contain a typical cold‐stage mollusc fauna. The sediments containing these floras and faunas are associated with thermal contraction cracks, indicating the presence of permafrost. The final sand and gravel aggradation in the Devensian forms the Block Fen Terrace, near 0 m OD. The evidence indicates that it is younger than the lacustrine sediments resulting from the blocking of the Fenland at the Wash by Late Devensian ice at ca. 18.5 ka BP.

The sequence at Block Fen is related to nearby Ipswichian and Devensian sediments at Chatteris, March, Wimblington and Mepal, and to deposits at Wretton on the east margin of Fenland. The correlation permits an outline reconstruction of the history of the valley carrying the River Great Ouse between the Isle of Ely and the Chatteris and March ‘islands’ from the time of a gravel aggradation before the Ipswichian to the Flandrian. The reconstruction shows the time and level of the Ipswichian marine incursion into the Middle Level of Fenland and the extent of aggradation and erosion in the Devensian.
Englacial and proglacial glaciotectonic processes at the snout of a thermally complex glacier in Svalbard
Authors: Hambrey Michael J. , Huddart David
Published: February 2007

Many glaciers in Svalbard, which tend to be thermally complex with both warm and cold ice, produced complex ‘push moraines’ or ‘thrust‐moraine complexes’ at the time of their maximum neoglacial advance, and during their subsequent recession. Uvěrsbreen, which nearly reaches the coast of northwest Spitsbergen, has a push moraine 50 m high, comprising gravel and sand of fluvial origin, and diamicton derived from basal ice, as well as thrust masses of dead ice. The push moraine is almost entirely a product of the tectonic processes, especially thrusting, that occurred in the snout of the glacier and in the frozen sediments immediately in Journal of Quaternary Science front. Thrusting is probably initiated where the glacier switches from a sliding mode to a state of being frozen to the bed. Thrusting in the foreland is an extension of the same processes that occur within the ice itself, and a sole thrust probably extends from the frozen sediment that underlies the base of the glacier near its snout. Thrusting results in subglacial sediment being uplifted to a high level within the glacier or even to the surface. Subsidiary near‐horizontal thrusts parallel to the bedding plane link thrusts dipping up‐glacier, and result in local thickening of individual subglacial sedimentary units. Gravels incorporated in this way retain their integrity but sands are folded, whereas uplifted debris‐rich basal ice is intensely folded. The distinctive tectonic style of low‐dip bedding in gravels, truncated by high‐angle (30–40°) thrusts, and only localised folding in less competent material, differs from most descriptions of such ridges, but may be typical of many push moraines composed principally of fluvial material.
On the sensitivity of Holocene talus‐derived rock glaciers to climate change in the Ben Ohau Range, New Zealand
Authors: Kirkbride Martin , Brazier Vanessa
Published: February 2007

The morphology and surface ages of talus‐derived rock glaciers are investigated to establish the timing of rock glacier formation in the central Southern Alps. Samples of rock weathering rinds show that all rock glaciers studied were formed during the Neoglacial period, but differences exist between sites in the number of new rock glacier lobes formed by Holocene climatic fluctuations. A qualitative conceptual model is proposed to explain rock glacier formation in terms of two thresholds. An external threshold relates to the presence of a cool climate capable of allowing internal ice to form within talus slopes. An internal threshold relates to the presence of sufficiently thick talus at a site to generate a shear stress capable of overcoming internal friction within the talus/ice mass. The model produces a non‐steady‐state response to explain why unmodified talus, single‐lobed and double‐lobed rock glaciers developed at adjacent sites under the same climatic regime. Individual landforms have different sensitivities to formation, which depend partly on the previous history of talus accumulation and rock glacier activity at a site. The model demonstrates how successive cool climate periods may be fully represented by rock glacier lobes at sensitive sites but under‐represented at insensitive sites. Sensitivity (and therefore climatic representativeness) is favoured by high rates of debris supply. By implication, the timing of formation of rock glacier lobes in regions of prolonged cool climate and low debris production is less likely to correspond to the timing of climatic cooling and more likely to follow the ‘rules’ of deterministic chaos.
Mineral magnetic analysis of a ‘weathering’ surface within glacigenic sediments at Glanllynnau, North Wales
Authors: Walden John , Addison Kenneth
Published: February 2007

A number of ‘weathering’ horizons have been identified within glacigenic sediment sequences in North Wales and have been instrumental in determining various proposed Late Quaternary event chronologies. This paper applies the techniques of mineral magnetic analysis to such a sediment sequence at Glanllynnau. The presence (or otherwise) of evidence for weathering processes on the upper surface of the Criccieth Till, which is overlain by further glacial materials, is examined. Despite a marked colour variation between the ‘weathered’ and non‐weathered components of the Criccieth Till, their mineral magnetic properties suggest little or no variation in iron oxide assemblages. The consequences of this for the environmental interpretation of the sediment sequence are discussed.
Regional differences in the Lateglacial climate of northern Europe based on coleopteran analysis
Authors: Coope G. R. , Lemdahl G.
Published: February 2007

The termination of the Last Glaciation, the Lateglacial period, was characterised by highly unstable climates which, in northern Europe, oscillated between warm temperate and arctic conditions. Different indicators of past climate have provided contrasting views on the timing and intensity of these climatic changes. Here we present preliminary reconstructions of the thermal climate interpreted from subfossil coleopteran assemblages from Britain, Norway, Sweden and Poland, in which regional differences can be ascribed to the varying influence of, (a) the North Atlantic surface water temperatures, (b) the proximity of the Fennoscandian ice sheet and (c) the ice free continent. Quantification of the thermal climate enables these local differences to be resolved.