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SYLVI HALDORSEN KARL ANUNDSEN 《Boreas: An International Journal of Quaternary Research》1988,17(4):429-429
The results from a Nordic research project on Quaternary geology, entitled the Nordkalott project, were presented at a symposium in northern Sweden in 1987. Organic deposits and tills in northern Fennoscandia are interpreted as belonging to the Eemian as well as to interstadials and stades of the Weichselian. Retreat of the ice front under cold climatic conditions has been assumed for parts of northern Norway. Ice-dammed lakes formed during the deglaciation period are described from northern Finland. Boreas , Vol. 17, no. 4, consists of articles based on the symposium contributions. 相似文献
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We analyse the stacking process within the framework of imaging techniques. Our results show how the NMO stretch, traditionally looked upon as giving a negative contribution, can be utilized to improve the vertical resolution of the stacked data from a source deficient in low frequencies. The added bandwidth is provided by the spatial coherency of the energy emitted by a point source. 相似文献
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SYLVI HALDORSEN PER JØRGENSEN MARTIN RAPPOL PETER A. RIEZEBOS 《Boreas: An International Journal of Quaternary Research》1989,18(2):89-97
The clay mineral composition of a number of Saalian till samples from The Netherlands shows a large variation in smectite and illite abundances. The samples were selected according to their source area, as inferred from coarse erratic components. Specimens containing primarily rock fragments indicative of East and East-Central Baltic areas are associated with no or low smectite percentages in their clay fractions. Those with mainly flint and rock fragments indicative of the West Baltic areas have high smectite contents in the clay. In general the smectite-rich material is found in the lower portions of the Saalian till bed, whereas the smectite-poor occurs in the upper portions. The linkage between very fine and coarse till components in the upper smectite-free parts of the till suggests that this entire till has been subjected to englacial transport over distances of at least 1000 km. 相似文献
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JAN MANGERUD HANS-PETTER SEJRUP EIVIND SØNSTEGAARD SYLVI HALDORSEN 《Boreas: An International Journal of Quaternary Research》1981,10(2):137-208
A complete interglacial cycle, named the Fjøsangerian and correlated with the Eemian by means of its pollen stratigraphy, is found in marine sediments just above the present day sea level outside Bergen, western Norway. At the base of the section there are two basal tills of assumed Saalian ( sensu lato ) age in which the mineralogy and geochemistry indicate local provenance. Above occur beds of marine silt, sand and gravel, deposited at water depths of between 10 and 50 m. The terrestrial pollen and the marine foraminifera and molluscs indicate a cold-warm-cold sequence with parallel development of the atmospheric and sea surface temperatures. In both environments the flora/fauna indicate an interglacial climatic optimum at least as warm as that during the Holocene. The high relative sea level during the Eemian (at least 30 m above sea level) requires younger neotectonic uplift. The uppermost marine beds are partly glaciomarine silts, as indicated by their mineralogy, drop stones and fauna, and partly interstadial gravels. The pollen indicates an open vegetation throughout these upper beds, and the correlation of the described interstadial with Early Weichselian interstadials elsewhere is essentially unknown. The section is capped by an Early Weichselian basal till containing redeposited fossils, sediments, and weathering products. Several clastic dikes injected from the glacier sole penetrate the till and the interglacial sediments. Radiocarbon dates on wood and shells gave infinite ages. Amino acid epimerization ratios in molluscs support the inferred Eemian age of the deposit. The Fjøsangerian is correlated with the Eemian and deep sea oxygen isotope stage 5e; other possible correlations are also discussed. 相似文献
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SYLVI HALDORSEN JOHN SHAW 《Boreas: An International Journal of Quaternary Research》1982,11(3):261-277
Deposition of till by melt-out was described as early as a hundred years ago, and today the criteria which provide evidence to support an interpretation of melt-out till are available. The most important criteria are (P1 ) the presence of unlithified, sorted and stratified sediments within or interstratified with the till(s). (P2 ) the presence of a statistically preferred orientation of stone axes closely related to ice-flow condition, and (P3 ) a configuration of till with a recognizable textural or lithological property closely related to the configruation of englacial debris with regard to P1 . Based on P1 and P2 and on regional aspects, tills composing ridges transverse to the dircetion of ice flow are interpreted as mult-out till and flow till. The interpretation of till genesis must be based on the balnce of probability, as absolute proof is unrealistic in most cases. 相似文献
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Grain-size distribution of subglacial till and its realtion to glacial scrushing and abrasion 总被引：1，自引：0，他引：1
SYLVI HALDORSEN 《Boreas: An International Journal of Quaternary Research》1981,10(1):91-105
A subglacial till formed from a sandstone bedrock has a variable grain-size distribution which reflects its variable genesis. Glacial comminution processes were simulated by artificial mill experiments with fragments of the sandstone bedrock. Pure crushing caused disintegration along mineral boundaries into separate minerals, most mineral grains retaining their primary size during the crushing process. Abrasion produced cracks across the minerals and resulted in silt-sized rock flour. The experiments indicate that most of the sand-sized till material formed as a result of crushing, while the silt is mainly the result of abrasion. The sand and silt are both regarded as components resistant to further glacial comminution, but are formed by different comminution processes. By considering also the coarser till material, the general principles of glacial breakdown of resistant rocks from boulders to sand or silt can be illustrated. A matrix index and an abrasion index based on the mill experiments distinguish well between genetically different subglacial till types 相似文献
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