摘要:

AbstractThe reactions of pebbles, granules and sand grains to different flow—sediment—bed conditions under varying flow energy input are discussed and investigated theoretically and experimentally with special regard to the relaxation of sedimentary structures and their corresponding fabrics. Some aspects are given of dynamic conditions affecting the stability, erosion, transport and deposition of particles of different sizes and shapes in non-uniform frictional sediments under varying flow conditions.Different types of imbrication are related to particle geometry, flow velocities, flow separation, bed resistance to deformation, contacts of the particles, sediment transport, and time. Stability—erodibility of the particles at varying orientation is shown to depend on the support, angle of flow attack, particle exposure, and fluctuations of flow directions and tractive force.The response of gravelly sand beds to the flow energy input by development of gravelly transport—erosion surfaces, gradually stabilizing as imbricated pebble pavements, is demonstrated at different bed slopes under 2- and 3-dimensional geometry.Bed structures and forms of coarse-grained 2- and 3- dimensional delta bodies are related to the flow traction, flow separation, gravity pull, friction, and sediment segregation in backset, topset, foreset and bottomset beds.The results are shown in diagrams and tables. Conclusions and summaries are found at the end of each chapter. A key to interpret the sedimentary environment from textural and structural data is devised in Ch. 10.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879939

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractA gamma distribution function was used to simulate annual and seasonal precipitation in Alberta using long term records from 18 stations. Good agreement was obtained between historic and synthetic values. The parameters of the gamma function were used to divide the region into precipitation zones. An attempt was made to explain the sequences of wet and dry years in terms of the behaviour of the westerlies.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879940

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractThe erosion of mounds raised by burrowing animals on experimental plots on a slope in the Luxembourg Ardennes was studied in a number of ways. Splash selectively removed fine material from mound surfaces increasing their stoniness and resistance to erosion. The relatively few mounds not protected by litter during the winter were attacked by frost action. The importance of animal mounds as sediment sources was indicated by measurements with a rainfall simulator. The erosion rates of individual mounds varied considerably. The monthly collections from splash-boards suggested an average rate of erosion of about 2 mm/year but higher rates of surface lowering were indicated by erosion pins. Some of the implications of the results for slope process studies are considered.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879941

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractMeasurement of water temperatures and salinities in proglacial lake Jökulsáilón made during the spring, summer and winter months allows the structure of the lake water, together with its seasonal variations, to be described. A distinct thermal stratification is present during the summer season when a weakly developed thermocline separates warmer surface water from deep-lying cold, isothermal water. Multiple temperature inversions occur within the water column, implying that the thermal structure of the lake in summer is a dynamic one. In the winter months water at all depths and in all parts of the lake is isothermal at 0°C.Intermittent reversals of flow in the channel connecting the lake with the sea occur at all seasons and this allows saline water to enter the lake. The vertical and spatial distribution of salinity in Jökulsárlón varies greatly at different times of the year. For up to nine months of the autumn, winter and spring seasons the salinity pattern in the lake—a rapid increase at the surface followed by a smaller steady increase to a maximum of 10.5‰to 12.5‰at the base of the water column—appears to remain unchanged. During the summer months glacial melt-waters flush this salt water from the lake but leave a bottom-lying saline body of water (of maximum salinity 5‰) in one of the deepest areas of the lake basin. The implications that these temperature and salinity variations have for sedimentation in the lake are mentioned. It is considered that the presence of salt water in Jökulsárlón inhibits the formation of diatactic varved sediments, samples of which are known from neighbouring freshwater lakes of the Breidamerkurjökull.

ISSN:0435-3676    

DOI:10.1080/04353676.1976.11879942

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor