摘要:

AbstractThe occurrence of red desert soil profiles developed on Nubian Sandstone in the Libyan Sahara is discussed. From an examination of profile morphology in the field and the position of the soils at 970 m on an old land surface, it would be possible to regard them as desert paleosols formed under a previous humid climatic phase during the Quaternary. However, an investigation of the mineralogy of the soils and the underlying parent rocks strongly suggests that the properties of the soils are largely dependent on the parent material. Both have identical patterns of kaolinite content, haematite as the main ferric oxide, and similar proportions of quartz silt and coarse quartz sand. Therefore, the use of kaolinite and ferric oxides in interpreting past soil‐forming climates in arid regions needs to be carried out with caution, for in the present case such an interpretation would be unreliabl

ISSN:0360-1269    

DOI:10.1002/esp.3290040202

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractWestern Port, Victoria, Australia is a tide‐dominated embayment with an unusual and complex shape. Bottom currents and circulation and their effects on sediment processes were examined using instrumented tripods to measure currents, tides and wave activity, and to estimate sediment transport at nine locations in the bay. Overall bottom water movement patterns were determined by use of seabed drifters.The characteristics of the bay reflect a small catchment and low freshwater and sediment input. A complex system of channels is flanked by extensive intertidal areas.Tidal range varies up to more than 3 m, generating bottom currents up to 70cm s−1. Flow directions generally conform to channel alignments but major deviations are important. Net circulation in the bay is clockwise around the large central island. The ratio of tidal range to half‐tidal period (ΔH/ΔT) when compared with measured currents gave a method of prediction of the annual frequency distribution of maximum bottom current velocities.Determination of threshold current velocities enabled prediction of annual frequency of bedload movement (generally 50–100 per cent of tide cycles). Bedload mass transport for all observed tide cycles was calculated, and estimates of annual mass transport capacity (between 102and 106g cm−1a−1( were obtained from a relationship between predicted tidal conditions and mass transport.Seabed drifters delineated the major bottom water movements in the bay and adjacent Bass Strait, and also detailed circulation patterns. This linked the data from the tripod stations, in particular patterns of ebb‐ and flood‐dominance.A coherent picture of the processes operating in Western Port is presented by integrating these studies with corroborative studies of sediment distribution and morphology, hydrochemistry, and mathematical modelling. Some morphological characteristics related to tide‐domi

ISSN:0360-1269    

DOI:10.1002/esp.3290040203

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe modification of scree sediments entering a stream is examined by QDa‐Md methods. Loss of fine or coarse subpopulations or both in combination from an initially symmetrical grain size distribution is shown to result in the dispersion of the QDa‐Md plots throughout an envelope typical of fluvial sediments. Natural plots from the Rivers Earn and Tay provide live examples of the transenvironmental trend patterns demonstra

ISSN:0360-1269    

DOI:10.1002/esp.3290040204

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe slope of an alluvial fan increases with increasing debris size and sediment concentration in the flow, and decreases with increasing discharge. Laboratory studies suggest that the discharge which controls this slope, or dominant discharge, is that which is equalled or exceeded one quarter to one third of the time that flow occurs on the fan. In contrast, the dominant discharge in perennial alluvial rivers is equalled or exceeded only about 5 per cent of the time that flow occurs in the river. The dominant discharge on fans increases with increasing debris size, reflecting the importance of threshold stress.The slope of some natural and most laboratory alluvial fans is steepest on the flanks and gentlest along the axis. Consideration of the momentum of water debouching onto a fan at its apex suggests that the difference in slope between axis and flank should be greatest on steep fans composed of relatively non‐cohesive materials because on such fans higher discharges tend to flow down the axis, whereas lower discharges can be turned to course down the flanks. On fans with gentle slopes or composed of more cohesive material the higher discharges can also be turned toward the flanks, so on such fans the difference in slope between the axis and flank is less pronounced. Field and laboratory observations support this interpretation.Because deposition at any one time on an alluvial fan is localized, some areas aggrade while others remain at a fixed elevation. This process is treated as a Markov process with the probability of diversion from an area of active deposition into an adjacent lower area increasing as the height of the active area above the mean or ‘ideal’ surface increases. Analysis of data from laboratory and natural fans suggests that the amplitude of such surface irregularities is greater on fans composed of coarser material. The data on natural fans also suggest an increase in amplitude of the irregularities with increasing fan

ISSN:0360-1269    

DOI:10.1002/esp.3290040205

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractA hydrochemical budget is used to quantify the rate of chemical weathering and solutional denudation on Old Red Sandstone in East Twin drainage basin (0.2 km2) on the Mendip Hills for the 1972–73 Water Year. Net nutrient uptake by the biomass and precipitation inputs are subtracted from stream solute outputs to give an estimate of the solutes released to the system by weathering. The mineralogies of the sandstone and the soil are compared to predict possible weathering reactions for the primary and secondary minerals. Tentative estimates of primary mineral alteration and secondary mineral formation are then made by substituting the hydrochemical balances into the formulated weathering reactions. Finally the rate of solutional denudation (0.8 tonnes/a or 1.6 mm/100 a) is compared with other estimates of solutional and mechanical denudation at East Twin and with similarly derived results for other lithologie

ISSN:0360-1269    

DOI:10.1002/esp.3290040206

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe concept of causality has been a fundamental principle of scientific investigation for many centuries. Recently, however, there has been a significant reappraisal of the philosophical basis of the concept of causality and this has important implications for future geomorphological research.It is now recognized that there are two approaches to the study of relations between variables. Conventionally knowledge was divided into classes and, on the basis of time precedence, causal relations were defined. While this approach enables static systems to be analysed it does not apply to dynamic systems which exhibit mutual causality. This traditional view of knowledge became obsolete with the introduction of the concept of the continuum. Algebraic techniques now enable the solution of systems of simultaneous equations, provided that there are as many equations as unknowns. Significantly this approach applies to dynamic as well as static systems.Further advances in fluvial geomorphological research are dependent on the adoption of mathematical reasoning. This will concentrate research on the mode and rate of operation of channel processes and feedback mechanisms. Given this information it will be possible to develop a static process‐response model to explain and predict channel response to a set of input conditions, and a dynamic model to simulate channel development through time and spac

ISSN:0360-1269    

DOI:10.1002/esp.3290040207

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractGround retreat was monitored on two vegetated and two unvegetated profiles over a five‐year period. The average annual retreat of the two unvegetated profiles was 5.84 mm and 3.62 mm; that of the two vegetated profiles 2.34 mm and 2.07 mm. Slope evolution was controlled by the mid‐slope‐ward migration of two zones of accelerated erosion and the resulting replacement of a central rectilinear slope segment by the upper and lower slope ele

ISSN:0360-1269    

DOI:10.1002/esp.3290040208

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe modification of limestone scree slopes in North Yorkshire takes the form of downslope trains of finer stones. These features, termed stone chutes, usually coincide with a narrow defile in the limestone scar above. Investigations of four stone chutes below Raven Scar in Twisleton Dale revealed intermittent downslope movement of stones. On these coarse limestone screes, where there is insufficient fine material for debris flow formation, stone chutes are the visible evidence of slope evolution.

ISSN:0360-1269    

DOI:10.1002/esp.3290040209

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

ISSN:0360-1269    

DOI:10.1002/esp.3290040210

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

ISSN:0360-1269    

DOI:10.1002/esp.3290040211

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY