bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quaternary volcanic ash zones on the Iceland Plateau, southern Norwegian Sea
Authors: Sjwøholm Jorunn , Sejrup Hans Petter , Furnes Harald 
Published: February 2007

AbstractFour 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

AbstractArchaeological 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

AbstractThis 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

AbstractIn 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

AbstractA 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

AbstractMonthly 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

AbstractDiatoms 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

AbstractRadiocarbon 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

AbstractDeer 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

AbstractWhen 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

AbstractQuaternary 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

AbstractRadiocarbon 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

AbstractA 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

AbstractThe 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

AbstractDetailed 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

AbstractGeochemical 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

Abstract‘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.