Development of a cliff-top dune indicated by particle size and geochemical characteristics: Rubjerg Knude, Denmark

Particle size and geochemical data have been used to investigate the development of a large cliff-top dune at Rubjerg Knude, located on the western coast of Jutland, Denmark. Textural parameters and geochemical ratios provided useful indicators of the dune sediment provenance and mode of evolution of the dune. The dune sediments themselves showed no significant spatial particle size trends and reflect a number of processes, including grainfall, wind-ripple migration and avalanching (grainflow), which formed a high proportion of the deposits on both the stoss and lee sides of the present dune. Fine grainfall sediments, which have accumulated to form a sandplain in the lee of the dune, show fining and improved sorting with distance, and extend more than 2 km downwind of the dune crest. Comparison of the textural and geochemical data from Rubjerg Knude and other locations on the Jutland coast indicates that, although there is a contribution of sand to the dune from local marine sources, the main source of sand to the cliff-top dune and sand plain sediments has been provided by the wind erosion of the underlying cliffs, which are composed of Weichselian age sandy glaciofluvial and glaciolacustrine deposits. Optically stimulated luminescence dating indicated an apparent age for the sand at the base of 274 ± 14 years. If this date is reliable, it suggests that accumulation of the aeolian sand in this area began within approximately the last 300 years. Map and photographic evidence indicate that the modern high dune only began to form after 1885, apparently associated with an acceleration in the rate of coastal cliff retreat.     

Late Quaternary glacial and environmental history of Kongsøya, Svalbard

On western Kongsøya, Svalbard, three coarsening-upwards sequences of marine to littoral sediments, separated by tills, are recognised in sections at ca 50-92 m above present sea level. These sequences show major glaciations in the northern Barents Sea, resulting in substantial glacioisostatic downpressing of Kongsøya. Till fabrics indicate ice movements controlled by the local topography, while glaciotectonic deformations suggest that ice moved from an ice divide northeast of Kongsøya. independent of the local topography. The stratigraphical evidences show two pre-Holocene ice-free periods, when the climate was similar to or slightly warmer than at present. The age of these periods is not clear. It is suggested that the elder ice free interval is older than isotope stage 5e. The younger ice free interval could be of Eemian or Early Weichselian age. The uppermost succession of sublittoral-littoral sediments is of early Holocene age. It relates to the high (≥100 m) postglacial marine limit, dated to approximately 10,000 bp.     

A test of TOPMODEL'a ability to predict spatially distributed groundwater levels

TOPMODEL was calibrated to a small catchment using precipitation and runoff data. Acceptable fits of simulated and observed runoff were obtained during both the calibration and validation periods. Predictions of groundwater levels using this calibration did not agree well with observations at the 37 points within the catchment where groundwater levels were measured, including three locations with continuous recordings. Groundwater level observations at one single point in time, however, sufficed to calibrate new topographic–soil indices that improved the prediction of the local groundwater levels at the observed tubes. This suggests that spatially distributed calibration data are necessary to exploit reliably TOPMODEL's ability to predict spatially distributed hydrology. The mean or recalibrated transmissivity values at these 37 points differed from the catchment mean as determined by the precipitation–runoff calibration. Thus, while groundwater information can help in predicting groundwater levels at specific locations, increasing the number of local groundwater level measurements is not sufficient to improve the spatially distributed representation of subsurface flow by TOPMODEL for the catchment as a whole, as long as the groundwater information is not integrated in the precipitation–runoff calibration. © 1997 John Wiley & Sons, Ltd.     

Deglaciation history and landscape development of fjord-valley deposits in Buvika, Mid-Norway

Thick deposits of glaciomarine clay and silt overlain by Holocene marine sediments in Norwegian fjord valleys have been, and still are, subject to erosional processes such as river incision, ravine formation and slide activity. In Buvika, Mid‐Norway, these land‐forming processes have been highly influenced by the valley‐fill stratigraphy. Glaciomarine and marine clay sediments dominate this 8 km long hanging valley south of the Gaulosen fjord, with local occurrences of coarser‐grained sediments. Studies of sediments and structures in road excavations together with ¹⁴C ages indicate at least one, possibly two, minor glacier readvances in late Allerød/early Younger Dryas (YD) time. This implies a more dynamic ice sheet with more minor ice‐front oscillations than earlier documented in this region. Glacioisostatic rebound resulted in groundwater leaching of marine clay and quick‐clay formation in certain layers or zones. The relative sea‐level fall led to incision by rivers accompanied by numerous slides involving quick clay, which completely liquefies when remoulded. To the east, permeInger‐Lise Solberg (e‐mail: inger‐lise.solberg@sintef.no ), Department of Geology and Mineral Resources Engineering, Norwegian University of Science and Technology (NTNU). Present address: SINTEF Building and Infrastructure, Høgskoleringen 7a, NO‐7465 Trondheim, Norway; Kåre Rokoengen, Department of Geology and Mineral Resources Engineering, NTNU, Sem Sælands veg 1, NO‐7491 Trondheim, Norway; Louise Hansen, Lars Olsen and Harald Sveian, Geological Survey of Norway, NO‐7491 Trondheim, Norwayable layers of northwesterly dipping sand and gravel generally originate from a former ice‐marginal delta. These relatively thick and frequent layers of interbedded sand and gravel in the clay‐dominated deposits drain groundwater in the slopes, leading to the development of deeply incised ravines. To the south and north, thinner layers of coarse material in the clay lead to pore‐pressure build‐ups and quick‐clay development, resulting in numerous slide scars. Knowledge of the morphology, stratigraphy and erosion pattern of areas prone to formation of quick clay is important in order to understand the landscape development and evaluate risk areas.     

Surface temperatures of the Barents Sea

Temperature conditions in the Barents Sea are determined by the quality and quantity of the inflowing Atlantic water from the west and by processes taking part in the Barents Sea itself, in particular as a consequence of winter cooling and ice formation. The field of inflow to the Barents Sea during the period 1977-1987 has been studied. The surface winter temperatures within the Barents Sea vary in parallel with variations in the deeper layers of the inflowing water masses, whereas the surface temperatures in summer have a different variation pattern which is most likely dependent on the summer heating process.     

THE PEATLAND/ICE AGE HYPOTHESIS REVISED, ADDING A POSSIBLE GLACIAL PULSE TRIGGER

Carbon sequestering in peatlands is believed to be a major climate‐regulating mechanism throughout the late Phanerozoic. Since plant life first evolved on land, peatlands have been significant carbon sinks, which could explain significant parts of the large variations in atmospheric carbon dioxide observed in various records. The result is peat in different degrees of metamorphosis, i.e. lignite, hard coal and graphite. During phases of extensive glaciations such as the 330–240 Ma Pangea Ice Age, atmospheric carbon dioxide was critically low. This pattern repeats itself during the Pleistocene when carbon dioxide oscillates with an amplitude of c. 200–300 ppmv. This paper suggests that the ice age cycles during the Pleistocene are generated by the interglacial growth of peatlands and the subsequent sequestering of carbon into this terrestrial pool. The final initiation of ice age pulses towards the end of inter‐glacials, on the other hand, is attributed to the cyclic influx of cosmic dust to the Earth surface, which in turn regulates cloud formation and the incoming shortwave radiation. These shorter cycles have a frequency of c. 1000‐1250 years and might be connected to sunspot or other low frequency solar variations. In a wider context the ice age cycling could be regarded as an interplay between terrestrial life on the high latitudes of the northern hemisphere and the marine subsurface life in the southeast. If the results presented here are correct, the present global warming might just be the early part of a new warm period such as the Bronze Age and the Roman and Medieval Warm periods. This could be caused by entry into another phase of decreasing influx rates of cosmic dust. The increasing concentrations of atmospheric carbon dioxide might have contributed to this warming but, most important of all, it might temporarily have saved us from a new ice age pulse.     

Basal till genesis in relation to bedrock morphology in the Berghem area, southwestern Sweden

Investigations of Late Weichselian deposits on the plateau north of Berghem, southwestern Sweden, constitute the basis for a detailed interpretation of basal tills above the marine limit. Deposition in relation to bedrock ridges perpendicular to ice flow occurred mainly on the stoss side. The content of locally derived bedrock increases with depth and the intensity of deformation within the ridge increases whengoing from the ice-proximal to the distal position. Drumlinoid features around a rock hillock suggest that the depositional behaviour on the stoss side was slightly different in the central part compared with the flanks. In the ice-proximal position the earliest deposition occurred in the centre of the drumlinoid, where the frequency of locally derived components is highest. The deformation in the central part was more intense than on the flank. The details of the till stratigraphy and structures cannot be attributed to one single process. Rather, an interaction of processes is proposed to account for this deposition. The processes involved are lodgement, basal melt-out, deformation and subglacial meltwater sedimentation.     

The distribution of different glacial landscapes on southern Jameson Land, East Greenland, according to Landsat Thematic Mapper Data

Four geologic units previously mapped in southern Jameson Land. _East Greenland (Funder 1978, 1990) are identifiable on a false colour composite of Landsat Thematic Mapper (TM) spectral hands TM5. TM4 and TM1. The area covered by the Weichselian glaciations has a fresh glacial morphology and a less developed drainage system than the older landscape. The Weichselian glaciers reached more than 200 m a.s.l. in the west. but only about 100 m a.s.l. in the east. A contextual analysis (local frequency and local orientation) was included in a Maximum Likelihood classification (M-L) to map the extent of the Weichselian glaciations. Deposits correlated with the Saalian Scoreshy Sund glaciation are found on the central plateaux of Jameson Land. Landsat TM geological mapping of the surficial distribution of deposits from the Scoreshy Sund glaciation and of weathered Jurassic sandstone or deposits with a high percentage of such sandstone was done using a supervised Maximum Likelihood procedure. Except for the mapping of thc extent of the Late Weichselian Flakkerhuk glaciation, the Maximum Likelihood boundaries between units are in general agrecnient with earlier mapping or with the visual interpretation of the false colour composite. A strong vegetational influence. and similar spectral reflectance lrom deposits of different age due to similarities in lithological composition reduced the possibility of an independent remote sensing approach. Taking already existing general geological knowledge and chronology into account allowed successful Landsat TM geological mapping.     

Late Stone Age hunters

Book reviewed in this article:
Smith, C. 1992: Late Stone Age Hunters of the British Isles     

Glaciofluvial channels formed prior to the last deglaciation: examples from Swedish Lapland

At four localities in area east of the Sarek and Kebnekajse massifs in Swedish Lapland, glaciofluvial channels seem to have been overhidden by glaciers without having extensively modified. It is suggested that the channels were formed during an Early Weichselian stade. The last glaical advance had little effect on the pre-exiting landforms at these localities and probably also at many other places in the area. Earlier theories about glacial development and deglaciation patterns in this area are based on morphology and the assumption that the landforms were formed during the last deglaciation. These theories need to be revised.