摘要:

AbstractThe block-field investigation in the Narvik-Skjomen district has shown that the largest areas with flat continuous block fields are to be found in the higher parts of the mountains. There is a marked but variable lower limit (not conditioned by the gradient) for these block fields. The lowest values observed in the whole district lie within a zone between 1140 and 1220 m a.s.l.The depth of the block fields displays great local variations. The maximum depth measured is about 2 m. The blocks are underlain by finer material. Even today in the summit area of the district the frost is transporting blocks to the surface and sorting of the material is taking place.The well-developed state of the block fields around large snow-fields on scarcely weathered rock surfaces, the high local variability of the development of the block fields and the result of comparative X-ray analyses of the mineral distribution yield the conclusion that the block-field material in the district consists of postglacial weathering products and isolated erratics. Thus the block fields cannot be cited as indications of ice-free sites during the Würm glacial period.The highest rock surfaces near the edges of vertical precipices have most of the weathering pits in the district, which is probably due to the fact that these surfaces are subject to a large number of freeze-thaw cycles and high temperatures. The conditions favour both local microgelivation and chemical decomposition. Weathering pits also occur on block surfaces in the block-field material formed under recent periglacial conditions. Thus the weathering pits cannot be used as a proof that an area was not glaciated during the Würm glacial period.Finally the origin of the tor-like weathering stacks is discussed. On account of rapid drainage and evaporation the macrogelivation may be diminished locally in the higher parts of periglacial areas. On the other hand, microgelivation and chemical decomposition are locally favoured, especially along the lines of structural weakness. The result may be tor-like forms even in areas glaciated during the Würm glacial period.

ISSN:0435-3676    

DOI:10.1080/04353676.1966.11879730

出版商:Taylor&Francis    

年代:1966

数据来源: Taylor

摘要:

AbstractVegetation succession and sedimentation rates are being studied on those parts of the Kvikkjokk delta which are above normal summer low water level. Practically the whole delta is inundated during high floods (recurrence interval 3–4 years), but only 13% of the delta's land area receives sedimentation: during lower floods of annual frequency only 3%. Sedimentation is smoother and less variable during high than during low floods. It shows no correlation with suspended load transport during floods, but varies directly with the mean height of floods. It shows no simple correlations with vegetation, but close study of plant communities together with the study of stratification in the uppermost parts of the soil profile provides accurate information about actual sedimentation rates. Only a few plant communities receive sedimentation regularly, several never do, and special communities characterize, for example, the sinking areas on the delta. The mapping of delta vegetation by aerial photographs may provide clues to morphological activity in inaccessible drainage basins.

ISSN:0435-3676    

DOI:10.1080/04353676.1966.11879731

出版商:Taylor&Francis    

年代:1966

数据来源: Taylor

摘要:

AbstractThe tritium concentration has been determined in water from the outermost parts of the frozen core of a palsa and from different parts of the adjacent unfrozen peat. It is shown that the influence on the ground-water of precipitation with a high tritium content is restricted to the uppermost 2–3 m of the peat in the bog. The values of the tritium content in the peat underlying the frozen core of the palsa are still too low (less than 10TU) to be used for the identification of active zones of palsa formation.

ISSN:0435-3676    

DOI:10.1080/04353676.1966.11879732

出版商:Taylor&Francis    

年代:1966

数据来源: Taylor