摘要:

AbstractOn the backwall of Twynam East Cirque selected stones moving through snow creep were marked and their movements from 1963 to 1975 measured. Their annual movements varied markedly between 1963 and 1970 but thereafter little. The percentage of stones failing to move varied reciprocally with snow thickness over a snow course in a comparable site near Spencers Creek. The annual mean movement, ranging from 7·6 to 36·3 cm, correlated strongly with Spencers Creek snow thickness. Frequent occurrence of annual movements of intermediate value characterise the process.Snow surface maps with 2m contours for 1964, 1974 and 1975 permitted determination of snow slope at the stone positions and of snow thickness by subtraction of ground heights. A 2 m contour ground surface map was also the basis for hillslope angles at stone positions. Basal area and area transverse to snow movement were calculated from measurements of the three principal axes of the stones. The vertical angles and directions of their abrasion tracks were measured.Rank correlation of stone movements with hillslope and snow slope was usually not significant but with track angle was so in most years. Track angle and direction are controlled partly by hillslope and partly by local rock geometry. Movements correlated inversely with stone basal area on which frictional drag depends. Correlation with stone transverse area was weak and inverse; this may be due to snow tending to move round larger stones. In most years there was significant correlation with snow thickness and basal stress (calculated from snow thickness and snow slope). However, the amount of ‘explanation’ associated with all the independent variables was small and the experiments revealed an importance of surface roughness at various scales in controlling stone movement which was much greater than expected from direct observ

ISSN:0360-1269    

DOI:10.1002/esp.3290030102

出版商:John Wiley&Sons, Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractObservations on an Early Quaternary slope deposit in the Massif Central indicated that the texture and mineralogy of this deposit have been seriously altered by post‐depositional subsurface weathering. Analyses of clay fractions and water samples show that the montmorillonite present is a stable mineral in this environment and is, and has been, newly formed. As shown by water analyses from nearby sites, the chemical environment is strongly dependent on local factors. Consequently it can be seen that great care should be taken firstly in correlating different slope deposits on the basis of texture and clay mineralogy and secondly in using these parameters as (paleo) climatic indicator

ISSN:0360-1269    

DOI:10.1002/esp.3290030103

出版商:John Wiley&Sons, Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractGrumusols (Vertisols), though having a uniformly high clay content with depth, commonly exhibit a coarsening upward in the sand fraction, either of skeletal grains or of nodules. The non‐uniform way in which the wetting front advances in swelling clay soils, with preferred advance and swelling around the coarse grains, produces upward directional forces and uplifting of the grains, thus producing the observed textural differentiation in the coarse fraction.From observations of slickenside distribution in the profile, and using published data on the ratio of lateral to vertical stresses and swelling pressure distribution with depth, a concept of optimum depth for slickensides is developed. Generally at 150–200cm, below the depth of cracking, this depth depends in part on climatic conditions. Below the optimal depth increased overburden pressure and smaller moisture variations restrain the extent of swelling and deformation, above it drying produces cracks and obliterates large slickensides, though a strong bimasepic microfabric remains.The extent of intrapedonic turbation was estimated from measurements of the volume of cracks and of surface material falling into the cracks. It indicates a turnover time of several hundred to a few thousand of years. This agrees with the known increase of radiocarbon ages of organic matter (MRT) with depth which in Vertisols (Grumusols) is only slightly slower than in non‐turbating Udolls (Chernozems) and Udalfs (Lessivés). The moderate rate of homogenization due to intrapedonic turbation does not prevent the development of a normal organic carbon profile and it is slower than the upswelling of coarse grains by upward directional forces. The development of shear planes and slickenside structures is a rapid process and not dependent on tur

ISSN:0360-1269    

DOI:10.1002/esp.3290030104

出版商:John Wiley&Sons, Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe four models postulated for the formation of calcrete layers all involve the three‐stage process: provision of a carbonate‐rich solution, the movement of that solution and the precipitation of solid carbonate. The last step originates from either or both of two main alternatives: loss of CO2out of the solution increasing the pH and consequently the CO 32−concentration, or evaporation of the water effecting an increase in the ionic concentration. This paper presents theoretical calculations for the isotopic composition of the carbonate resulting from these two alternative processes. The isotopic composition of calcrete deposits from France, Spain, Italy, Libya, Cyprus, Kenya, Morocco, South Africa and India are compared with the theoretical models. The calcrete samples from Spain, Cyprus and India are probably the result of evaporation pr

ISSN:0360-1269    

DOI:10.1002/esp.3290030105

出版商:John Wiley&Sons, Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractA study of water chemistry changes and stream network changes during and immediately after the 1976 drought is made in an area to the north and east of Bristol. In particular, contrasts are made between the Cotswold Limestone dip slope and the Severn Clay Vale. Immediately following the end of the drought a solute flushing effect was observed on the clay streams, whilst network extension on limestone streams incorporated new source areas and maintained higher solute concentrations throughout the post‐drought period investigate

ISSN:0360-1269    

DOI:10.1002/esp.3290030106

出版商:John Wiley&Sons, Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractDuring 1974 and 1975, measurements of splash and wash were carried out in the cultivated area, in a station installed on 6·5 per cent slope covered with a loess in which a grey‐brown podzolic soil has developed. Splash has been measured using an apparatus prepared for this purpose and wash has been measured on plots of standard length (22·13m).The splash is some tens t/ha.year but the splash loss calculated using the results of the measurements of splash is only a few tens kg/ha.year. Splash is positively correlated with the erosion index of the rains and with the structural stability but negatively with the crop cover.As splash, wash is positively correlated with the erosion index of the rains and negatively with the crop cover, but unlike splash it is negatively correlated with structural stability. The mean value of the wash loss is a few t/ha.year but very important differences are observed from one plot to another with regard to the structural stability. However, on a given plot wash loss and splash are positively correlated because the particles of soil detached by splash are easily carried off by runoff, but the relation between wash loss and splash is very different from one plot to another because splash is positively and wash loss negatively correlated with the structural stability of so

ISSN:0360-1269    

DOI:10.1002/esp.3290030107

出版商:John Wiley&Sons, Ltd    

年代:1978

数据来源: WILEY

ISSN:0360-1269    

DOI:10.1002/esp.3290030108

出版商:John Wiley&Sons, Ltd    

年代:1978

数据来源: WILEY

ISSN:0360-1269    

DOI:10.1002/esp.3290030110

出版商:John Wiley&Sons, Ltd    

年代:1978

数据来源: WILEY

ISSN:0360-1269    

DOI:10.1002/esp.3290030111

出版商:John Wiley&Sons, Ltd    

年代:1978

数据来源: WILEY

ISSN:0360-1269    

DOI:10.1002/esp.3290030112

出版商:John Wiley&Sons, Ltd    

年代:1978

数据来源: WILEY