bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ice wedges: Growth, thaw transformation, and palaeoenvironmental significance
Authors: Harry D. G. , Gozdzik J. S. 
Published: February 2007

AbstractFrost‐cracking and ice‐wedge growth are fundamental processes within the permafrost environment. Extensive areas of contemporary permafrost terrain are characterised by frost‐fissure polygons, formed by repeated thermal contraction‐cracking of the ground. The incremental growth of ice veins and wedges along the axes of contraction‐cracks contributes significantly to the volume of ground ice in near‐surface permafrost. In areas beyond the present limit of permafrost, the recognition of ice‐wedge pseudomorphs provides one of the few unambiguous indications of the former existence of permafrost conditions. An understanding of the processes of ice‐wedge growth and thaw transformation is essential if contemporary ice wedges are to be used as analogues for Pleistocene frost‐fissure structures, in palaeoenvironmental reconstructions.
The significance of rock glaciers in the glacial‐periglacial landscape continuum
Authors: Giardino John R. , Vitek John D. 
Published: February 2007

AbstractRock glaciers are distinct landforms whose wide distribution, occurrence, and significance often go unrecognised. They are deposits of poorly sorted, angular, blocky to tabular debris which are held together by an ice core or a matrix of ice‐cemented fine clastics. Rock glaciers have formed in glaciated and non‐glaciated areas. Many researchers have suggested that the absence of an ice core or the lack of movement indicates relict or fossil status. Active and inactive states can be viewed as the end members of a movement continuum. Movement rates, derived from world‐wide locations as reported in the literature, range from less than 1 cmyr−1to greater than 130cmyr−1. Unfortunately, lack of observed movement has been equated incorrectly with an inactive status.Rock glacier movement must be considered from a rheological point of view. Movement is controlled by the transformation of potential energy to kinetic energy as the system attempts to reach thermal equilibrium or stability. Whereas a glacier can completely disappear or redevelop, reactivation of a rock glacier requires only the re‐establishment of the conditions responsible for development and maintenance of interstitial ice. Although it might not be possible to re‐establish an ice core, interstitial areas can definitely be recharged with ice and thus facilitate movement. The concept of active versus inactive should be abandoned in favor of the view that a spatial and temporal continuum of form and movement exists.
The occurrence of Greigite in sediments from Loch Lomond
Authors: Snowball Ian , Thompson Roy 
Published: February 2007

AbstractGreigite has been identified in the sediments of Loch Lomond using X‐ray diffraction. Greigite is the dominant magnetic mineral in the oldest sediments recovered, while magnetite predominates in the younger sediments which had previously been used for palaeomagnetic secular variation studies. A layer of sediment in between these two magnetic mineral regimes has very low magnetic concentrations, probably as a consequence of magnetite dissolution associated with sulphide rich pore‐waters produced at the time of a marine incursion.The greigite largely oxidises once the sediment is exposed to air, but if freeze dried the greigite becomes surprisingly stable. Following freeze drying the greigite can be heated to 280°C in air before it alters and loses its strong ferrimagnetic properties.
Loess and palaeoenvironment: Some results of a European joint programme of research
Authors: Derbyshire Edward , Billard Armelle , Van Vliet‐Lanoë Brigitte , Lautridou Jean‐Pierre , Cnr Mauro Cremaschi 
Published: February 2007

AbstractIn 1985, a programme of research on the sedimentology and diagenesis of the loess and loessic silts of western Europe was initiated jointly by laboratories in Leicester, Meudon, Caen, Milan, Cardiff and Southampton, involving a limited amount of comparative work on the loess from types sites in the Loess Plateau of central China. Preliminary results include the following: (1) Experimental procedures in particle size analysis, clay sample preparation and microscopy have been standardised in all cooperating groups; distinctive fabrics indicative of depositional mechanisms have been recognised. (2) Comparison of aeolian, colluvial and alluvial silt by laser‐scanning and bulk magnetic susceptibility anisotropy methods appears to differentiate aeolian silt from loessic silts re‐deposited by slope processes and flowing water. (3) The variability in the anisotropy of the limon à doublet facies has been assessed by image analysis of scanning electron microscopy (SEM) and optical microscopy. Strong anisotropy has also been measured in thin section imagery of loess from Normandy and Poland as the product of freezing and thawing. This is confirmed by scanning electron microscopy and by experimental freezing of some silts. (4) The clay fabric and mineralogy in western European loess differ from those in Chinese loess, especially in the case of semi‐arid deposits. (5) Distribution of CaCO3, using thin sections and SEM analysis, has been determined for loess from Normandy and the Rhǒne valley in France and for some Chinese loess, At Saint Vallier, zones of CaCO3 concentration occur masking much of the original (loess) sedimentary skeleton which is a locally reworked loessic silt with some laminations. Despite considerable scatter, the palaeomagnetic results indicate a reversed polarity throughout, placing the whole Saint Vallier sequence in the Matuyama chron.These preliminary results suggest the existence of two different palaeoenvironments: one typified by central China, with arid glacials and humid interglacials; and the other represented by western Europe, with generally high humidities. There was stronger weathering and soil development and fewer freezing effects on the lossic succession in northern Italy than in western littoral Europe.
The recognition of glacial retreat from palynological data: A review of recent work in the British Isles
Authors: Tipping Richard M. 
Published: February 2007

AbstractRecent publications have presented palynological data from the early postglacial period in the British Isles, which have been interpreted as reflecting sequential glacial retreat following the Loch Lomond Stadial, The methodologies and results of these studies were examined and were concluded to be insufficient to demonstrate glacial retreat. A more cautious methodology was adopted and tested at several pollen sites in the Awe valley, Scotland. The results differed from previous studies in not demonstrating the sequence of palynological changes predicted from the hypothesis. These results need to be replicated at other localities, however, before the deglacial chronology hypothesis can be dismissed. Proposals to test the hypothesis further are suggested.
A Holocene tsunami deposit in eastern Scotland
Authors: Long David , Smith David E. , Dawson Alastair G. 
Published: February 2007

AbstractA thin, regionally extensive, laterally persistent sand layer identified within the Holocene coastal sequences of eastern Scotland, dated to 7000 years BP, is suggested to be a tsunami deposit. The likely source of the tsunami wave is the earthquake induced second Storegga Slide on the Norwegian continental slope at least 750 km northeast of the deposit.
Quaternary tephrachronology on the Iceland Plateau, north of Iceland
Authors: Sejrup H. P. , Sjøholm J. , Furnes H. , Beyer I. , Eide L. , Jansen E. , Mangerud J. 
Published: February 2007

AbstractFour major ash zones recorded in piston cores raised from the Iceland Plateau north of Iceland are shown to be coincident with the last four interglacial isotopic stages. Their geochemical composition links the ashes to volcanic events on Iceland. The occurrence of these ash layers, which record events orders of magnitude larger than the ‘normal’ Holocene volcanic eruptions, can not be explained by changes in sea ice cover and atmospheric circulation alone. It is suggested that these events are related to pressure releases in the magma chambers resulting from major deglaciations of the Icelandic Ice Cap.
Sediment source variations and lead‐210 inventories in recent Potomac Estuary sediment cores
Authors: Oldfield Frank , Maher Barbara A. , Appleby Peter G. 
Published: February 2007

AbstractWe present the results of magnetic measurements (low field susceptibility, anhysteretic and isothermal remanences) on samples of sediment from 11 cores from the Potomac River between Washington DC and its mouth. The magnetic properties indicate that at sites in the upstream reaches especially, there has been a shift to surface‐soil‐derived sediments in recent times. No such shift is indicated at the mouth of the Estuary. Comparison with pollen, 210Pb and trace metal analyses, where available, suggests that the shift to soil‐derived material dates from the early to mid‐19th century and coincides with a major land use change previously documented by Brush et al. (1982). Inventories of unsupported (excess) 210Pb activity in the cores increase upstream, are positively correlated with total sedimentation rates, and, in the upper reaches where the magnetic properties indicate soil inwash, greatly exceed values expected from direct atmospheric deposition alone. We infer that in these cores, most of the unsupported 210Pb is deposited from the surfaces of the catchment as a result of soil erosion.
Late Quaternary stratigraphy of the northern Rockall trough and Faeroe‐Shetland channel, northeast Atlantic Ocean
Authors: Stoker Martyn S. , Harland Rex , Morton Andrew C. , Graham Douglas K. 
Published: February 2007

AbstractA late Quaternary deep‐water stratigraphic framework has been established for the deep‐water areas (>450m) of the northern Rockall Trough and Faeroe‐Shetland Channel. Four stratigraphic units (1–4) are identified; these are primarily biostratigraphic units based on dinoflagellate cyst evidence. Unit 1 represents the late Weichselian glacial (pre‐13 000 yr BP); unit 2 the Late Glacial Interstadial (11 000‐13 000 yr BP); unit 3 is of Younger Dryas age (10 000‐11 000 yr BP); and unit 4 represents the Holocene interglacial (post‐10 000 yr BP). This stratigraphy is supported by the discovery of the mixed Vedde Ash (10 600 yr BP) and North Atlantic Ash zone 1, and the Saksunarvatn Ash (9000–9100 yr BP), concentrated in units 3 and 4 respectively. The sedimentology indicates that the oceanographic regime underwent a major change between the glacial and interglacial stages. This is marked by the onset of strong bottom current activity, allied to the restoration of overflow of the Norwegian Sea Deep Water into the North Atlantic, towards the end of the Younger Dryas Stadial. Despite intense bioturbation and bottom‐current reworking the basic stratigraphic framework is maintained. Recognition of two volcanic ash markers enables correlation with established onshore and offshore sequences of marine and non‐marine environments.
Stress indicators adjacent to buried channels of Elsterian age in North Germany
Authors: Bruns Johannes 
Published: February 2007

AbstractTectonic and soil mechanics investigations of a strongly plastic clay (Miocene ‘Mica Clay’) led to the detection of strain phenomena induced in connection with the formation of Elsterian buried channels. A microjoint system with randomly distributed fissures is thought to result from early Elsterian dessiccation and frost crack formation. It occurs frequently in the upper part of the clay horizon. A younger joint system, which is encountered throughout the entire clay body, comprises macrojoints arranged in three joint sets. The evidence strongly suggests that they were formed by gravitational and kinematic loading of the clay body by overriding ice. The macrojoints display various secondary alterations such as slickensides, escarpments, shear zones, erosive and pressure zones, the formation of which is seen in context with the channel incision. Investigations into the genesis of these alterations indicate a strong horizontally‐orientated stress induction lateral to the channels, which resulted in stiffness modulus anisotropy. It has also caused a horizontal compression of the clay body, which at that time was already consolidated through ice overburdening. Horizontal compression of the clay led to evorsion of pore water eroding clay particles from the joint walls. Lower water content of the clay, in combination with increased dry unit weights, are found adjacent to the channels today.
Pleistocene climatic change in Southern Australia and its effect on speleothem deposition in some Nullarbor caves
Authors: Coede Albert , Harmon Russell S. , Atkinson Tim C. , Rowe Peter J. 
Published: February 2007

AbstractActivity ratios of 234U/238U, 230Th/234U, and 230Th/232Th have been determined for calcite, gypsum and halite speleothems from caves of the Nullarbor Plain, mostly in the area N and NW of Mundrabilla Station, for the purpose of U‐series dating. All calcite speleothems contain adequate amounts of uranium for dating, but some show an excess of 230Th. Stratigraphic relationships indicate that there were at least three phases of calcium carbonate deposition in the Nullarbor caves. The calcite samples, with one possible exception, have ages in excess of ca. 400000 yrs BP. This suggests that no significant amounts of calcium carbonate deposition have taken place during the last 400ka.At present, active deposition of speleothems is restricted almost entirely to gypsum and halite. The only gypsum speleothem dated was found to have a finite age of ca. 185 ka. Six dates on a small halite speleothem containing insect and arachnid remains indicate that it formed rapidly during Holocene time.
The last glaciation and relative sea level history of Northwest Ellesmere Island, Canadian high arctic
Authors: Evans David J. A. 
Published: February 2007

AbstractPhilips Inlet and Wootton Peninsula are located at 82°N and 85°W on the northwest coast of Ellesmere Island and are composed of three bedrock controlled zones: (1) 900 m undulating plateau dissected by fiords; (2) a deeply fretted cirque terrain >1200m; (3) a 300m plateau bounded by coastal cliffs. Each zone contains different glacier morphologies and these control glacigenic sediment and landform assemblages. The extent of the last glaciation is mapped using the distribution of moraines, kames, meltwater channels and glacimarine sediments. Glaciers advanced on average <10 km from their present margins and many piedmont lobes coalesced and floated in the sea. Morainal banks were deposited at the grounding lines of floating glaciers, and where debris‐charged basal ice occurred, subaqueous fans were deposited upon deglaciation. Marine shells dating 20.2 ka BP (<2km from present ice margin) and 14.9ka BP (from a morainal bank) document full glacial marine fauna. Thirty‐three radiocarbon dates document glacier retreat patterns and are used to reconstruct the postglacial sea level history (glacioisostatic rebound pattern). An equidistant shoreline diagram is constructed using the 8.5ka BP shoreline as a guide. Tilts from 0.73‐0.85m/km are calculated for this shoreline. Using two firm control points and tilts from elsewhere on northern Ellesmere Island, the 10.1 ka BP (full glacial) marine limit descends from 117m as at the fiord heads to 63 m asl at the north coast. Deglaciation started with a pronounced calving phase throughout the field area between 10.1 and 7.8ka BP. This chronology is similar to that from northeast Ellesmere Island and attests to an early Holocene warming trend recorded in high arctic ice cores. A maximum lag of 2.1 ka exists between the field area and locations to the south of the Grant Land Mountains suggesting differences in glacioclimatic regimes on either side of the mountain range. Persistent reconstructions of all‐pervasive ice sheets for the last glaciation of the area are obsolete and should be abandoned.
The Seal Edge Coombes, North Derbyshire — a study of their erosional and depositional history
Authors: Johnson Richard H. , Tallis John H. , Wilson Peter 
Published: February 2007

AbstractPeriglacial landforms and deposits of Devensian age are commonly observed on the higher hill slopes of North Derbyshire but to date very few glacial features or sediments have been recognised. At Seal Edge, the escarpment slope has been sculptured by both frost and nivational processes but at Middle Seal Clough there are lobate ridges located beyond the talus foot that are probably moraines, formed during the Dimlington Stadial of the Late Devensian, by a small corrie glacier. The history of the ‘coombe’ has been interpreted from a study of both the inorganic and organic sediments and although the results are not conclusive, they indicate that ice and snow were important in the development of the coombe and that the peat formations in the basin also provide the earliest record to date for events in the vegetation history of the southern Pennine moorlands.
Micromorphology of some North Sea till samples, a pilot study
Authors: Van Meer Jaap J. M. Der , Laban Cees 
Published: February 2007

AbstractIn a pilot study three samples of diamictons from boreholes in the Dutch sector of the North Sea have been thin sectioned. In the thin sections the granulometry, structure and plasmic fabric of the diamictons have been studied. On the basis of this study two of the samples have been interpreted as flow tills, while one sample has been interpreted as a basal (lodgement) till.
Pleistocene sediments, soils and landscape evolution at Stebbing, Essex
Authors: Whiteman Colin A. , Kemp Rob A. 
Published: February 2007

AbstractPleistocene sediments and soils exposed at Stebbing in central Essex, England are described, analysed and interpreted. The sand and gravel units above Eocene London Clay and Upper Pliocene Red Crag are shown to be a high level member of the Kesgrave Formation, with a surface immediately beneath that of the Westland Green Gravels, which are tentatively assigned to the Pre‐Pastonian ‘a’ Stage of the British Quaternary succession. The rubified, argillic soil developed in the surface of these fluvial deposits is a composite of the Valley Farm and Barham Soils and displays micromorphological evidence of several phases of clay illuviation, gleying and clay coating disruption. Originally truncated and buried beneath Anglian gelifluction deposits, cover sand and till, the soil has been exhumed in most places by subsequent erosion. The full succession, however, is preserved within large gulls that formed by periglacial cambering prior to this erosion. More recent loess incorporation and pedogenesis have modified the exhumed soil and the materials within the gulls.
Sand intraclasts within a diamicton mélange, southern Niagara Peninsula, Ontario, Canada
Authors: Menzies John 
Published: February 2007

AbstractSand intraclasts found within diamicton units along the north shore of Lake Erie in the Mohawk Bay area of the Niagara Peninsula would appear to be part of a ‘block‐in‐matrix’ mélange. The intraclasts are undeformed and many exhibit primary bedding structures. Numerous intraclasts have been rotated and/or tilted and are, in general, subrounded in outline. Examination of the surrounding diamicton reveals that the diamicton clast fabrics exhibit a wide scatter and are not characteristic of any known till clast fabric. Around each intraclast exists an aureole of brecciated diamicton. Other evidence in the form of macro‐ and microshear structures, and banding within the diamicton indicate that the diamicton has been subject to high strain.Interpretation of the sand intraclasts seems to be intrinsically linked to the origin of the diamicton and together linked to the origin of the mélange. Various hypotheses are suggested separately for the sand intraclasts, diamicton and mélange. A subglacial deformable bed hypothesis is advanced as the most acceptable explanation for the complete sediment sequence in which diamicton and frozen sand intraclasts, the latter mobilised from the substrate, are moved as a mélange below an active fast‐moving ice mass.Several implications from this study emerge with regard to glacial sedimentology and stratigraphic interpretations.
Lateglacial and Early Flandrian Coleoptera from La Taphanel, Massif Central, France: Climatic and Ecological Implications
Authors: Ponel Philippe , Russell Coope G. 
Published: February 2007

AbstractA Lateglacial and early Holocene sequence of coleopteran assemblages is described from La Taphanel in the Massif Central, France. The site is a sediment‐filled small lake at an altitude of almost 1000 m. The insect fauna provides evidence for a detailed palaeoecological reconstruction, and in particular enables a reconstruction of climatic changes at the close of the last glaciation. A sudden climatic warming occurs at about 13000 yr BP followed by a temperate episode equivalent in time to the Bølling period. There is clear evidence of a short cold period between the Bølling and Allerød that is approximately equivalent to the Older Dryas period. The Allerød phase is decidedly cooler than the Bølling, as is shown by the Coleoptera from several sites in northwest Europe. A clear Younger Dryas signal is provided by the Coleoptera, with climates similar in severity to those of the glacial period. The climatic improvement at the start of the Holocene is also sudden, so that by Preboreal times temperatures were equivalent to those of the present day.
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

AbstractExcavation 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.