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Kolstrup, E. 2007 (January): Lateglacial older and younger coversand in northwest Europe: chronology and relation to climate and vegetation. Boreas , Vol. 36, pp. 65–75. Oslo. ISSN 0300–9483.
Dutch, Belgian, German and Danish Lateglacial localities with both coversand and well-dated organic deposits are used to relate older and younger coversand development to changes in climate and vegetation. The number of well-dated coversand sequences in northwest Europe is low, but it appears that the transition from older to younger coversand was asynchronous and spanned Bølling sensu stricto to late Allerød, so there is no clear single cause for the change in grain-size composition of the sediment. Aeolian activity took place during all parts of the Lateglacial and seems to have continued well into the Holocene. The effect of changing temperatures is mainly reflected indirectly as periods with denser vegetation, especially forest, that led to reduced coversand net-accumulation. The outline proposes that the lithostratigraphic position of a peat layer cannot be used as an Allerød marker because even a well-developed peat layer within coversands may differ in age from one area to the next. The combined coversand and vegetation development shows that local conditions were important for the accumulation and preservation of sediments. 相似文献
Dutch, Belgian, German and Danish Lateglacial localities with both coversand and well-dated organic deposits are used to relate older and younger coversand development to changes in climate and vegetation. The number of well-dated coversand sequences in northwest Europe is low, but it appears that the transition from older to younger coversand was asynchronous and spanned Bølling sensu stricto to late Allerød, so there is no clear single cause for the change in grain-size composition of the sediment. Aeolian activity took place during all parts of the Lateglacial and seems to have continued well into the Holocene. The effect of changing temperatures is mainly reflected indirectly as periods with denser vegetation, especially forest, that led to reduced coversand net-accumulation. The outline proposes that the lithostratigraphic position of a peat layer cannot be used as an Allerød marker because even a well-developed peat layer within coversands may differ in age from one area to the next. The combined coversand and vegetation development shows that local conditions were important for the accumulation and preservation of sediments. 相似文献
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Primary production of the northern Barents Sea 总被引：7，自引：0，他引：7
ELSE NØST HEGSETH 《Polar research》1998,17(2):113-123
The majority of the arctic waters are only seasonally ice covered; the northern Barents Sea, where freezing starts at 80 to 81°N in September, is one such area. In March, the ice cover reaches its greatest extension (74-75°N). Melting is particularly rapid in June and July, and by August the Barents Sea may be ice free. The pelagic productive season is rather short, 3 to 3.5 months in the northern part of the Barents Sea (north of the Polar Front, 75°N), and is able to sustain an open water production during only half of this time when a substantial part of the area is free of ice. Ice algal production starts in March and terminates during the rapid melting season in June and July, thus equalling the pelagic production season in duration.
This paper presents the first in situ measurements of both pelagic and ice-related production in the northern Barents Sea: pelagic production in summer after melting has started and more open water has become accessible, and ice production in spring before the ice cover melts. Judged by the developmental stage of the plankton populations, the northern Barents Sea consists of several sub-areas with different phytoplankton situations. Estimates of both daily and annual carbon production have been based on in situ measurements. Although there are few sampling stations (6 phytoplankton stations and 8 ice-algae stations), the measurements represent both pelagic bloom and non-bloom conditions and ice algal day and night production. The annual production in ice was estimated to 5.3 g Cm-2 , compared to the pelagic production of 25 to 30 g Cm-2 south of Kvitøya and 12 to 15 g Cm-2 further north. According to these estimates ice production thus constitutes 16% to 22% of the total primary production of the northern Barents Sea, depending on the extent of ice-free areas. 相似文献
This paper presents the first in situ measurements of both pelagic and ice-related production in the northern Barents Sea: pelagic production in summer after melting has started and more open water has become accessible, and ice production in spring before the ice cover melts. Judged by the developmental stage of the plankton populations, the northern Barents Sea consists of several sub-areas with different phytoplankton situations. Estimates of both daily and annual carbon production have been based on in situ measurements. Although there are few sampling stations (6 phytoplankton stations and 8 ice-algae stations), the measurements represent both pelagic bloom and non-bloom conditions and ice algal day and night production. The annual production in ice was estimated to 5.3 g Cm
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ELSE KOLSTRUP VAGN MEJDAHL 《Boreas: An International Journal of Quaternary Research》1986,15(4):311-321
Excavations for an oil pipeline in western Jutland provided the opportunity to study geological features in the trenches. Among these were ice wedge casts, composite wedge casts, and wedges with primary infilling of eolian sand. In this paper the characteristics of three wedges with a high proportion of primary infill of eolian sand are described in some detail. Thermoluminescence (TL) dating was made on the eolian sand using 0.1–0.3 mm grains of quartz and potassium feldspar. The TL ages are: 39,000 ± 5,000, 24,000 ± 3,000, and 17,000 ± 3,000 years B.P. These ages are discussed and compared with indirect datings. Palaeoenvironmental conditions at the time of maximum cold during the upper part of the Weichselian are briefly considered. 相似文献
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ELSE KOLSTRUP REW MURRAY GÖRAN POSSNERT 《Boreas: An International Journal of Quaternary Research》2007,36(3):314-325
The chronology of two adjacent Danish Lateglacial sedimentary sequences with well-developed layering of alternating aeolian sand and organic matter has been investigated using both Optically Stimulated Luminescence (OSL) and Accelerator Mass Spectrometry (14 C). Both sites are known to cover at least the period Bølling to Younger Dryas, with the so-called older and younger coversand types present at both localities. Typical overall uncertainties with the OSL data are about two to five times those of the 14 C ages, but both data sets contain clear outliers. When these are excluded, OSL ages appear to be systematically slightly younger than the 14 C ages, by about 10%; possible reasons for this are discussed. The investigation stresses the importance of making several age estimates from any single locality. The older coversand type makes up the pre-Bølling and most, or possibly all, of the Bølling (which also has the highest net accumulation rate). Deposits of the younger coversand type are dominant in layers younger than the Bølling. 相似文献
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BY HANNA RIDEFELT JONAS ÅKERMAN ACHIM A BEYLICH JAN BOELHOUWERS ELSE KOLSTRUP ROLF NYBERG 《Geografiska Annaler: Series A, Physical Geography》2009,91(3):215-232
Solifluction movement rates from 1952 to 2008 for the Abisko region, northern Sweden, have been compiled and analysed through correlation tests and multiple regression. The temporal analysis is based on two datasets ( Lobe11 & gridAB and Line B ) from Kärkevagge. The dataset Lobe11 & gridAB show a strong correlation between movement rates and mean annual air temperature (MAAT) and MAAT is also identified as one of the significant contributing parameters in the multiple regression model. No significant correlations were found for the Line B dataset. The spatial analysis indicates generally higher movement rates in the western part of the region and at lower altitudes mainly between 700 and 900 m a.s.l., but the spatial variability is high. To reduce the influence of the temporal variation the data for the correlation tests of the spatial variations were divided into two parts: 1957 to 1980 and 1981 to 2008. The correlation analysis of the dataset 1957 to 1980 shows a significant negative correlation between annual average movement rates and permafrost probability and altitude. The dataset 1981 to 2008 shows a positive correlation between movement rates and wetness index. It is concluded that movement rates may increase with higher MAAT in the western part of the region (Kärkevagge), the spatial variability of movement rates within the region is very high and that altitude (and/or permafrost) together with wetness index are the main controls on the regional spatial variation. The study highlights the limitations in establishing statistical relationships between movement rates and climate using data from different field empirical studies. 相似文献
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ELSE KOLSTRUP 《Boreas: An International Journal of Quaternary Research》1985,14(3):217-223
Three to four km southwest of Egtved, in middle Jutland, diggings for a gas pipeline cut through a form which is believed to be a fossil frost mound. The horizontal outline of the form is that of a rounded silty body with a diameter of about 45 m. It is surrounded by layered eolian sand of which the layers are bent upwards into a vertical position close to the silty body. A small bulge of silty material is present on top of the neighbouring sand. The mechanism for the formation of the form is thought to have much in common with that of the hydrostatic system pingo of Mackay. It cannot be determined whether the mound was annual or perennial, but the presence of silty sediment in the central part shows that liquified sediment moved upward to fill the present form. By means of lithostratigraphy and pollen analysis, the development and decay of the mound were dated to Late Dryas time. It is suggested that similar features may be present in other parts of Scandinavia outside the area glaciated during the Late Dryas. 相似文献
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ELSE KOLSTRUP MICHAEL HOUMARK-NIELSEN 《Boreas: An International Journal of Quaternary Research》1991,20(2):169-182
Lithostratigraphical and palynological investigations of a coastal cliff section at Kobbelgård, Møn (Denmark) reveal a sedimentary sequence of Weichselian age. Bedded clayey sediments are overlain by stratified silt, sand and occasional beds of clay and gravel. The clay was deposited in water, and most of the silt and sand is aeolian, forming fairly thick units of loess and sand-loess. The lower part of the sequence forms an anticlinal structure, probably of glacio-tectonic orìgìn. The upper part of the sequence appears to represent a depression filling. In the lower part of this, clayey layers alternating with loess deposits suggest wet conditions periodically. In the upper part, loess and fine sand were deposited, interfingering with slope sediments in a periglacial environment from around 24,000 BP almost until the Weichselian glacial maximum. Pollen investigations at the site point to three periods of vegetation. The lowest pollen sequence contains much Ericales, Empetrum and occasionally also Pinus , and is thought to be of Early Glacial or Lower Pleniglacial age. Overlying pollen-bearing strata with high proportions of herbs, including Artemisia , antedate a TL dating of c. 27,000 BP. An upper pollen sequence, derived from slightly organic layers in the depression fill, points to a palaeovegetation almost exclusively of herbs, with Artemisia as an important component. This vegetation is thought to represent a relatively moist site, and is TL dated to c. 24,000 P. 相似文献
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