ISSN:0197-9337    

DOI:10.1002/esp.3290100503

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractDetection of anomalies in measurements of low rates of limestone surface lowering with a traversing micro‐erosion meter (MEM) led to temperature‐controlled laboratory and field investigations of some sources of error in the method. Regressions for the correction of temperature change in the instrument and in the stud‐rock interface were obtained. Probe erosion tests permitted a correction to be devised and also provided information whereby a measure of operational irregularity was adopted. Corrections and error terms were applied to field measurements from two southern New South Wales karsts and a collection of Australian limestone slabs exposed at one site.Examination of these results and of published MEM rates from other parts of the world validated the MEM method. Marine platforms are lowered at such gross rates that these error sources may be neglected there. However limestone lowering in terrestrial environments cannot be assumed to proceed at rates which permit this and recommendations are made about procedures to ensure that investigations are prosecuted within the limitations of the m

ISSN:0197-9337    

DOI:10.1002/esp.3290100504

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractQ‐mode factor analysis of soil particle size data is used to identify the three dominant geomorphic processes responsible for the spatial variability of particle size in a catchment on the basaltic Darling Downs landsurface. Three factors are shown to account for 95 per cent of the textural variability of a suite of transported and sedentary materials. The spatial characteristics of groups of samples associated with the three factors suggests that the three factors are associated with suspended sediment transport and deposition, weathering, and bedload transport and deposition respectively. These interpretations are supported by the detailed graphical analysis of the cumulative particle size curves. The spatially variable influence of the three factors and related processes is given by their respective factor loadings which are mappable for the surface layer material

ISSN:0197-9337    

DOI:10.1002/esp.3290100505

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractIn a 350 m wide reach of the braided, gravel‐bed Ashley River, the surface layer of the bed material was sampled in 141 areas of homogeneous graded sediment along seven cross‐sections, and 30 kg bulk samples were collected at 86 randomly selected locations along the cross‐sections. At one location, a single 854 kg sample composed of 28 subsamples was also collected.Analysis of the single large sample indicate that accurate determination of mean grain size D at that site requires, desirably, a sample of ∼ 100 kg, but that samples in which the weight of the largest stone is less than 5 per cent of the total weight have unbiased estimates of D. Spatial variability of bulk material is such that 228 and 50 samples are needed to estimate D to ± 10 and ± 20 per cent respectively of the true value; requirements for estimating inclusive graphic standard duration are only 11 and 3 respectively.The grain‐size distribution of the surface layer is only weakly related to the bulk material beneath. The results of ‘Wolman sampling’ along 12 cross‐sections at two pace intervals (average 120 stones per cross‐section) indicate that estimation of overall surface D to ±10 and ±20 per cent would require sampling along 64 and 14 cross‐sections respectively.It is concluded that accurate characterization of bed sediment in gravel‐bed rivers is very demanding of labour and resources, and that careful planning is needed to ensure efficien

ISSN:0197-9337    

DOI:10.1002/esp.3290100506

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractFour genetic varieties of ice‐marginal cross‐valley moraine ridge have been identified in south‐central Ulster, Northern Ireland. Type I ridges are flat topped, composed of stratified, water‐lain sediments and formed by coalescence of a series of supraaquatic deltas. Type II ridges are sharp crested, composed of stratified, water‐lain sediments and formed by coalescence of a series of subaquatic deltas. Type III ridges show mixed morphological and sedimentological characteristics of type I and II ridges. Type IV ridges are sharp crested or hummocky, composed of poorly‐sorted and poorly‐stratified water‐lain sediments and formed by coalescence of a series of subaquatic sediment gravity flow cones. Field evidence indicates that cross‐valley moraine ridges in south‐central Ulster were deposited in proglacial lacustrine environments. Ridge type depended principally on (1) the nature of the proglacial bedrock slope; (2) the manner in which meltwater entered the proglacial zone; and (3) ice‐sheet behaviour during deglaciation, particularly within the ic

ISSN:0197-9337    

DOI:10.1002/esp.3290100507

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe variation of mechanical and chemical denudation is investigated using discharge and sediment yield data from the Upper Colorado River System. Annual precipitation ranges from approximately 150 mm to 1500 mm. Mean specific yield ranges from 0‐2 1/s km2( = 6 mm p a) to 151/s km2( = 475 mm p a). The hydrological‐geomorphological system adjusts itself to these varying climatic conditions; in some areas, however, the effects of lithology or land use seem to override the climatic controls. It is demonstrated that the increase in the absolute and particularly the relative amount of suspended sediment is closely related to a decrease in annual runoff and to an increase in the importance of high magnitude/low frequency events. This indicates that in areas of low annual runoff and high runoff variability, soluble rocks are more resistant than in more humid areas. During high magnitude/low frequency events, suspended sediment concentrations and loads are very high in semiarid areas due to sparse vegetation cover and dominance of direct runoff. Events of moderate magnitude and frequency, which in more humid areas transport most of the dissolved load, seldom occur. The trend towards increasing mechanical denudation is even observed in areas of very low runoff (0‐221/s km2= 7 mm p a). The peak of sediment yield in dry areas seems to approximate the point of no runoff very closely. Mechanical and chemical denudation are of equal importance at a runoff of about 300 mm per

ISSN:0197-9337    

DOI:10.1002/esp.3290100508

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractHoneycomb weathering has been observed in a Carboniferous sandstone at a coastal location near Ballycastle on the north coast of Northern Ireland. Specimens of this sandstone have been analysed by X‐ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. Results reveal that calcium sulphate (gypsum) is the only salt present and is found only at and immediately below the rock surface. SEM observations suggest that crystallization of salts in pores could easily dislodge quartz grains to promote granular disintegration, whilst etching of quartz grain surfaces attests to chemical weathering activity within the rock However, the reason for the development of the honeycomb pattern is not know

ISSN:0197-9337    

DOI:10.1002/esp.3290100509

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractLichenometry provides a suitable means of dating recent debris‐flow activity on alpine colluvial fans. Existing growth curves can be used, provided that anomalous thalli are excluded and allowances are made for differences in the growth rates ofRhizocarpon alpieolaandRhizocarponsectionRhizocarponthalli. The distribution of flow deposits through time is non‐random and two periods of increased activity (1670‐1720 AD and 1790‐1860 AD) can be identified. There is no evidence for a large increase in debris‐flow activity in the late 19th century, as has been found in Scotland. This can be attributed to the absence of detrimental landuse practices in the Norwegian st

ISSN:0197-9337    

DOI:10.1002/esp.3290100510

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe annual discharge of the Lower Jordan River has decreased from about 1250 × 106m3y−1to about 300 × 106m3y−1due to water exploitation. The decrease in water discharge was not followed by a similar decrease in the suspended sediment. Evidence from air photographs and maps from 1920s to early 1970s show that the river is adjusting itself by shortening its course. The shortening is not distributed uniformly along the valley length. Local effects obscure the effect of decreasing discharge. Since the early 1970s the channel is becoming longer again due to a change in the dominant

ISSN:0197-9337    

DOI:10.1002/esp.3290100511

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290100512

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY