摘要:

ABSTRACTA population of stones moving under seasonal snow creep down the backwall of a shallow glacial cirque in the Snowy Mountains, Australia, was sampled on a stratified random plan. On this basis the weight of the total population was estimated for combination with movement measurements over the 1963–1975 winters to determine an annual transport rate of 15 t/m/km2/y, resolvable into a vertical drop of 6.6 t/m/km2/y and a horizontal shift of 13.5 t/m/km2/y. Compared with the rates determined by Rapp for different slope processes in Swedish Lapland this is slow. This process may be better developed in mid-latitudes than in high latitudes as a result of more rapid firnification.Some measures of nivational striae are given.

ISSN:0435-3676    

DOI:10.1080/04353676.1978.11879958

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

ABSTRACTPits, with a diameter up to 50 cm and a depth of max. 25 cm, often with overhanging walls, are found in the Lake Mjörn area northeast of Göteborg. The pits are concentrated to a near lake level zone between 3 m above lake level and 1.5 m below it. The pits are most frequent in tonalitic and amphibolitic rocks. Thin sections show that these rocks contain a larger amount of chlorite than the other rocks. The scattered chlorite makes the rocks less resistant against weathering. Thin sections show that the rock at the bottom of pits is not more weathered than the rock near the pits. Pits developed in glacial striae show that the weathering is Post-Glacial.It is supposed that the formation of pits is initiated by the accumulation of water in small depressions like coarse glacial striae and joints or along foliation planes. The exclusive shore position of the pits indicates the importance of the intermittent wet occasions, their duration and frequency. Once the initial depression is formed and sufficient frequency of wetting and drying is at hand, the depression will have a generally higher weathering rate than the surrounding bedrock and a pit will be formed.

ISSN:0435-3676    

DOI:10.1080/04353676.1978.11879959

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

ABSTRACTHypotheses developed to explain meandering in river channels often demand excess energy to initiate bank erosion, which is usually assumed to occur in the location of a pool. Field observations of variations of channel geometry in riffle-pool sequences on the River Fowey, Cornwall, England indicate that equilibrium channels can, however, be wider at riffles because of bank erosion at these locations. Furthermore, the varying flow geometry suggests that the minimum variance theory of meandering may require reassessment.

ISSN:0435-3676    

DOI:10.1080/04353676.1978.11879960

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

ABSTRACTA wind tunnel of recirculating type was constructed and used for the study of eolian ripples. The height and wave-length of the ripples were found to be a function of wind velocity. There is a ripple formation period, the length of which depends on wind velocity. During this time fully developed ripples form. After that threshold time ripples are almost stable in size and form except at the high wind velocities which produce“secondary”ripples on the surface of the“primary”ripples and thus cause a decrease in mean wave-length. Material sorting on the rippled surface was studied as well as the migration rate of the ripples. At the beginning of ripple formation a process of sorting of the sand material was found.

ISSN:0435-3676    

DOI:10.1080/04353676.1978.11879961

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

ABSTRACTAltitudinal gradients of temperature vary in many different ways, notably according to the time periods considered, but also to such things as differences in topography, synoptic conditions, climatic regions, soils and vegetation cover. This study attempts to separate out the effects due to varying synoptic conditions and different climatic regions, primarily within Great Britain but referring also to southern Norway. Altitudinal gradients of maximun, mean and minimum temperatures react differently to these various influences.

ISSN:0435-3676    

DOI:10.1080/04353676.1978.11879962

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

ABSTRACTMany accounts of nivation activity stress the role of snowpatches in supplying water to the area immediately downslope, thereby facilitating rillwash and solifluction. It is often assumed that melt of the snowpatch itself provides the main source of water. Runoff meansurements and dye-tracing observations carried out on perennial snowpatches in the Canadian Arctic indicate that the main source of runoff from snow-covered nivation features is active layer interflow, brought to the absence of a thawed zone beneath snowpatches, and that melt of the snowpatch itself is relatively unimportant in generating runoff.

ISSN:0435-3676    

DOI:10.1080/04353676.1978.11879963

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

ABSTRACTConventional radiography, xeroradiography, tomography and contrast enhancement were applied to the study of thinly laminated sediments from Lake Valkiajärvi, Finland. Conventional radiography provides satisfactory contrast when the sediment sample is thin, and tomography gives better results in the study of thick unextruded sediment cores, while xeroradiography and contrast enchancement did not essentially improve poor radiographic contrast in the present experiments. Examples are given of radiographs of thin laminae and of microdensitometer curves obtained from these.

ISSN:0435-3676    

DOI:10.1080/04353676.1978.11879964

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

ABSTRACTA chronology for the main Holocene events in Nordfjord. Mellemfjord and Disko Fjord on the west coast of Disko could be established with the help of radiocarbon dates of marine shells and a comparison with earlier results, particularly from the area south of Disko Bugt. The glaciers had retreated from the fjords before 8000 B.P. but the retreat from the outer coast began at about 10000 B.P., possibly somewhat earlier. The relative emergence of the coast during and after the deglaciation ended at about 3000 B.P. The highest marine limit recorded was 85 m in Disko Fjord. At lower altitudes, below 45 m. marine terraces and beach ridges were formed. After 3000 B.P., when there were no land/sea level changes or possibly only a small subsidence. Neoglacial rock glaciers advanced from the cirques, often down to the present shore, most of them reaching their maximum position in A.D. 1600–1920. Periglacial features are common in the whole area: pingos occur in some of the main valleys.

ISSN:0435-3676    

DOI:10.1080/04353676.1978.11879965

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

ABSTRACTExcavations in the outermost end moraine ridges in front of three Jotunheimen glaciers exposed buried palaeosols and moss layers which were14C dated. Pre-‘Little Ice Age’Neoglacial maxima were indicated by14C dates on various soil organic fractions at Styggedalsbreen and Leirbreen; the most probable dates for these maxima are ca.2700 calendar years B.P. and ca.1300 calendar years B.P. A‘Little Ice Age’maximum was confirmed by dates onSphagnummoss layers at Storbreen. Use of replicate dates, dates on different kinds of organic material and on different fractions of soil organic matter were found useful in assessing the relative accuracy of the datings. It is concluded that the‘Little Ice Age’glacier expansion episode was the most extensive in southern Norway, but that in at least two other periods of Neoglacial time, glaciers expanded to similar dimensions. No evidence was found for Neoglacial expansion episodes earlier than ca.300014C years B.P. Attention is drawn to the temporal and spatial complexities of Neoglacial glacier fluctuations in the European Alps; although similar complexities are suspected for southern Norway and elsewhere in Scandinavia, doubt is expressed in the ability of current glacial stratigraphic approaches to reconstruct the finer details of a Neoglacial chronology. It is inferred that climatic deteriorations since the Preboreal chronozone have been of no greater magnitude than that of the‘Little Ice Age’.

ISSN:0435-3676    

DOI:10.1080/04353676.1978.11879966

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor