bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical textures on quartz grains: An experimental approach using salts
Authors: Magee A. W. , Bull P. A. , Goudie A. S.
Published: February 2007

Two groups of fresh crushed Brazilian quartz grains (0.4–0.6 mm) were placed in 10 ml of various saturated salt solutions (sodium sulphate, sodium chloride, magnesium sulphate, sodium carbonate, and sodium carbonate and soil). One group was placed in an environmental cabinet programmed to simulate summer diurnal temperature and relative humidity values recorded in Wheeler Valley, a dry valley in southern Victoria Land, Antarctica. The other group was allowed to remain at normal laboratory conditions. Quartz grains from both groups were removed at pre‐selected intervals for examination using the scanning electron microscope. After 50 hours chemical surface textures were formed on the quartz grains in all but the sodium sulphate solution. At the 140 hour interval all the salt solutions used were producing chemical surface textures on the quartz grains. This paper demonstrates that chemical surface textures can be produced on quartz grain surfaces by saturated salt solutions in a short period of time and may prove to be representative of chemical surface textures produced in a saturated saline environment.
The significance of scarp retreat for cenozoic landform evolution on the Colorado Plateau, U.S.A.
Authors: Schmidt Karl‐Heinz
Published: February 2007

Since the beginning of the Cenozoic period several hundreds of metres of the sedimentary cover have been removed from the Colorado Plateau. Palaeoclimatic considerations show that the Colorado Plateau has been dominated by dry climates throughout the Cenozoic with the possible exception of the early Palaeocene. Today in the still prevailing arid climate, which strongly accentuates differences in rock resistance, the relief shows a structurally controlled cuesta scarp topography in the slightly deformed strata of alternating resistance.

In examining whether the denudational efficiency of scarp retreat was sufficient to account for the wide erosional gaps in the sedimentary cover, rates of scarp retreat were determined by using the information of dated volcanic material and by applying a new method, which calculates the amount of retreat from the width of beheaded valleys of known age. Rates of retreat range from 0·5 to 6·7 km my−1. The results show that the rates of retreat are controlled by the thickness and resistance of the caprocks.

A model of Cenozoic scarp retreat demonstrates that the rates of recession calculated for the scarps in Upper Cretaceous rocks were sufficient to bring them into their present positions from the centre of the Monument Uplift on the central Colorado Plateau. The late Eocene positions of the cliffs in the Early Tertiary formations give an indication of their maximal extent. After the Upper Cretaceous sediments had been removed from the uplifts, erosion cut through successively older rocks, and activated scarps in stratigraphically lower positions. Scarp retreat can operate simultaneously and independently at different levels, which enabled this erosional mechanism to remove great proportions of the sedimentary cover of the Colorado Plateau during the Cenozoic.
A rational explanation of cross‐profile morphology for glacial valleys and of glacial valley development: A further note
Authors: Hirano Masahige , Aniya Masamu
Published: February 2007

The authors discovered a misinterpretation in their original paper which is corrected here.
An assessment of surface‐mine reclamation based upon sheetwash erosion rates at the Glenrock coal company, Glenrock, Wyoming
Authors: Toy Terrence J.
Published: February 2007

Comparative erosion rates provide a rational basis for evaluating reclamation success because the work performed by erosion processes is a function of both forces and resistances operating on a surface. Sheetwash erosion data collected by the LEMI technique over several years at the Dave Johnston Mine in east‐central Wyoming show that, based upon average values, there is generally little difference between the erosion rates of natural and reclaimed hillslopes at this locale. Therefore, it is permissible to infer that the reclamation programme has been successful from a geomorphic perspective. However, there is considerable variation in erosion rates about the average for individual hillslopes in both the natural and reclaimed groups.

Examination of these data by hillslope element and segment show that, based upon average values, the concave elements of natural and reclaimed hillslopes experience the highest rate of sheetwash erosion. Again, however, there is considerable variation about the average and considerable erosion can occur in any element or segment of particular hillslopes.

Lastly, there are seasonal oscillations of hillslope surface elevation with frost‐heaving prevalent during the late autumn to early spring months and erosion prevalent during the late spring to early autumn months.
Longitudinal dunes can move sideways
Authors: Hesp Patrick , Hyde Robert , Hesp Virginia , Zhengyu Qian
Published: February 2007

Longitudinal dunes occur in all major sand areas in the world. Their dominant mode of migration or extension is considered to be either prevailing‐ or resultant wind‐parallel, the dunes extending downwind via accretion of the terminal nose. In the Qaidam Pendi in Northwest China a series of active longitudinal dunes extend downwind at 5–10 m yr−1. Internal sedimentary structures examined in the dunes, however, display beds dipping in one direction rather than two opposed directions as is expected. Analysis of aerial photographs confirms that these dunes migrate laterally up to three metres per year, whilst maintaining a symmetrical longitudinal dune morphology.
A distinction between ice‐pushed and ice‐lifted landforms on lacustrine and marine coasts
Authors: Gilbert Robert
Published: February 2007

Study of a small lake, Second Roach Pond, in Maine, U.S.A. clarifies the distinction between shoreline features created by ice push which occurs on both lacustrine and marine coasts, and those created by ice lift related to tidal action in the marine environment. Ice lifting occurred as littoral sediments were frozen into the lake ice, followed by a rise in water level due to damming of the lake before the nival melt each spring. In the period 1905 to 1969 prominent barricades were constructed by this means. A classification based on this distinction is proposed. Ice‐pushed landforms include ramparts, ridges in coarse and fine sediments, stone pavements, ice keel grooves, pushed boulder grooves, and tails off promontories. Ice‐lift features include boulder barricades, perched stones, stone garlands, and ice keel depressions.
The rate of bedrock weathering by frost action: Field measurements and a predictive model
Authors: Matsuoka Norikazu
Published: February 2007

Shattering rate, surface temperature, moisture content, and the physical and strength properties of bedrock were measured in four rockwall sites of the Japanese Alps. Five‐year observations revealed that the bedrock shattering rate was usually much higher in the freeze‐thaw period from October to next May than in the frost‐free period from June to September. This indicates that frost action is the most important shattering process, although unusual heavy rainstorms in summer are also responsible for the shattering. A combination of some empirical relationships derived from recent laboratory experiments leads to a predictive model of the frost shattering rate. This model shows that the annual shattering rate is dependent on the annual freeze‐thaw frequency on the rock surface, and the degree of saturation and tensile strength of the rock masses. The coefficients involved in the model were determined using the field data.
Coarse woody debris and channel morphology interactions for undisturbed streams in southeast Alaska, U.S.A.
Authors: George Robison E. , Beschta Robert L.
Published: February 2007

Coarse woody debris and channel morphology were evaluated for five low‐gradient streams that ranged from first to fourth order (0.7 to 55 km2 watershed area). Debris volumes were directly related to variations in bankfull width. Woody debris was associated with 65 to 75 per cent of all pools and the relative proportion of types of pools (i.e. plunge, lateral scour, etc.) varied with stream size. High variability in channel depths and widths was common. The results provide benchmark values of woody debris loadings and channel morphology for undisturbed coastal Alaskan stream systems.
A long flume study of the dynamic factors affecting the resistance of a loamy soil to concentrated flow erosion
Authors: Govers G. , Everaert W. , Poesen J. , Rauws G. , De Ploey J. , Lautridou J. P.
Published: February 2007

Experiments were carried out in a 20 m long flume to assess the variation of the runoff erosion resistance of a loamy soil as a function of initial moisture content and compaction. The results of seven experimental runs show that the runoff erosion resistance of a loamy material is extremely sensitive to variations in initial moisture content and, to a somewhat lesser extent, in bulk density. The very low resistance to runoff erosion of initially dry material is explained by structural changes which take place at the time of wetting: slaking and microfissuration cause a considerable decrease of the soil's shear strength and therefore of its resistance to runoff erosion. A first analysis shows that, during a given rainfall event, initially dry soils may well show significantly more erosion than initially wet soils, despite the increase of infiltration with decreasing initial moisture content.
An estimator for the density of a sediment‐induced stratified fluid
Authors: Shiati K.
Published: February 2007

The contribution of dissolved salts and/or sediment particles in altering the fluid density cannot be neglected in studying density stratified flows. In this paper equations are presented to evaluate the density of water as a function of temperature, salt content, and sediment load. A nomograph based on these equations is constructed. The nomograph is applied to estimating the density variations of the Shapur River, a sediment‐laden stratified river in Southern Iran. It is illustrated that sediment gives rise to large peaks in density of the river. Such variations are known to be an important factor in geomorphology.
Differential bedload transport rates in a gravel‐bed stream: A grain‐size distribution approach
Authors: Shih Shyuer‐Ming , Komar Paul D.
Published: February 2007

The grain‐size distributions of bedload gravels in Oak Creek, Oregon, follow the ideal Rosin distribution at flow stages which exceed that necessary to initiate breakup of the pavement in the bed material. The distributions systematically vary with flow discharge and bed stress, such that at higher flow stages the grain sizes are coarser while the spread of the distribution decreases. A differential bedload transport function for individual grain‐size fractions is formulated utilizing the dependence of the two parameters in the Rosin distribution on the flow stress. The total transport rate, which is also a function of the flow stress, is apportioned within the Rosin grain‐size distribution to yield the fractional transport rates. The derived bedload function has the advantage of yielding smooth, continuous frequency distributions of transport rates for the grain‐size fractions, in contrast to the discrete transport functions which predict rates for specified sieve fractions. Successful reproduction of the measured fractional transport rates and bedload grain‐size distributions in Oak Creek by this approach demonstrates its potential for evaluations of transport rates of size fractions in gravel‐bed streams. The approach will be useful in investigations of downstream changes in bed material grain‐size distributions.
The hydrological response of soil surfaces to rainfall as affected by cover and position of rock fragments in the top layer
Authors: Poesen J. , Ingelmo‐Sanchez F. , Mucher H.
Published: February 2007

Rainfall experiments have been conducted in the laboratory in order to assess the hydrological response of top soils very susceptible to surface sealing and containing rock fragments in different positions with respect to the soil surface. For a given cover level, rock fragment position in the top soil has an ambivalent effect on water intake and runoff generation. Compared to a bare soil surface rock fragments increase water intake rates as well as time of runoff concentration and decrease runoff volume if they rest on the soil surface. For the same cover level, rock fragments reduce infiltration rate and enhance runoff generation if they are well embedded in the top layer. The effects of rock fragment position on infiltration rate and runoff generation are proportional to cover percentage. Micromorphological analysis and measurements of the saturated hydraulic conductivity of bare top soils and of the top layer underneath rock fragments resting on the soil surface reveal significant differences supporting the mechanism proposed by Poesen (1986): i.e. runoff generated as rock flow or as Horton overland flow can (partly) infiltrate into the unsealed soil surface under the rock fragments, provided that they are not completely embedded in the top layer. Hence, rock fragment position, beside other rock fragment properties, should be taken into account when assessing the hydrological response of soils susceptible to surface sealing and containing rock fragments in their surface layers. A simple model, based on the proportions of bare soil surface, soil surface occupied by embedded rock fragments, and soil surface covered with rock fragments resting on the soil surface, describes the runoff coefficient data relatively well.
Distributions of horizon‐limited direct beam potential radiation in steep pastures
Authors: Boyer Douglas G. , Feldhake Charles M.
Published: February 2007

Agricultural production from steep terrain is frequently limited to pasture systems, where forage harvesting is done by grazing animals. Intercepted solar radiation determines the energy available for forage production. A model was developed for estimating potential direct beam radiation in areas with a wide range of aspects, landscape positions, and various shadow sources. The model was applied to a small, steep pasture watershed in central Appalachia to determine the spatial distribution of potential direct beam radiation. Effective horizon was an important parameter affecting the energy budget of the study watershed. A simple means for estimating global radiation from the modelled potential direct beam radiation, given atmospheric transmissivity and cloudiness, was presented. When the proportion of global radiation that was diffuse radiation was increased the effective horizon was less important and the spatial variability of modelled radiation decreased.
Trapping of airborne dust by mosses in the Negev Desert, Israel
Authors: Danin Avinoam , Ganor Eliezer
Published: February 2007

Airborne silt and clay containing calcium carbonate, quartz, clays, marine nannoplankton, and aquatic diatoms are trapped among stems of mosses in the Negev Highlands Desert. The mosses were studied in an area with 70 mm mean annual rainfall. They grow over the particles covering them and trap additional dust as it comes, resulting in the accumulation of loess sediments. The mosses protect the accumulated soil from erosion by wind or water. Remnants of the moss leaves and stems were found at a depth of 15 mm and more. No particles or minerals typical to basalt were found in the moss‐trapped soil. The function of cushiony mosses may be used to explain the processes of loess trapping and protection in larger areas in moister areas such as the Northern Negev. Microscopic fossils in the dust may be used as guides to the origin of the (aeolian) sediments.
Hydrological mapping from SPOT imagery
Authors: Ali Abdalla Elsadig
Published: February 2007

Four SPOT images, one panchromatic and three multispectral, were studied to evaluate their usefulness for hydrological mapping in an arid environment. Simple visual methods of interpretation were used to plot the drainage network independently from each test image. The results were compared with the drainage network shown on the topographic map of the area. Results show that with the panchromatic image, over 90 per cent of the map content could be discerned, identified, and plotted. The accuracy of plotting the drainage system from the multispectral images seems to depend on the season in which data had been acquired. However, in all cases, the success rate is not less than 70 per cent. Comparison with Landsat Thematic Mapper (TM) imagery showed that SPOT system is superior in hydrological mapping.
Geochemical equilibria of iron in sediments of the roaring river alluvial fan, Rocky Mountain National Park, Colorado
Authors: Litaor M. Iggy , Keigley R. B.
Published: February 2007

Iron geochemistry of the sediments and interstitial waters of the Roaring River alluvial fan in the Rocky Mountain National Park, Colorado was studied using a chemical equilibria approach. Large concentrations of colloidal Fe in the filterable Fe of the interstitial waters results in considerable overestimation of Fe2 + activity. The overestimation of Fe(II) seriously hampered the usefulness of chemical equilibria approach in the study of Fe geochemistry. Buried soil organic matter and a high water table within the alluvial fan has produced a highly reduced environment which results in elevated colloidal and filterable iron concentrations in the interstitial waters. The source of the iron is probably iron oxides within the buried soil and primary iron‐bearing minerals in the sediments. When the iron‐rich solutions reach the surface, the water rapidly oxidizes and amorphous ferric hydroxides precipitate. Between 190 to 370 mmol of iron per kg of surficial material were precipitated at the surface within two months. Noticeable decreases in the total amount of C and extractable iron (20 per cent and 30 per cent respectively) in the buried soil were observed during the study period (1985‐1987) which implies a significant reduction in iron dissolution and subsequent deposition across the alluvial fan.
Climatic effects on the runoff conditions in Hungary
Authors: Nováaky Béla
Published: February 2007

Using runoff and climatic observations from 37 small watersheds in Hungary a regional climate‐runoff relationship has been established. This non‐linear relationship is a modification of Budiko's similar equation and can be used to estimate the effect of climate changes on long‐term average runoff. The degree of change in runoff depends not only on changes in precipitation and temperature, but also on the present climate characteristics. The regional relationship is verified only within a relatively narrow range of precipitation and temperature and this fact limits its use in climate impact assessment. Model calculations show that a relatively slight shift in climate, an increase in annual temperature by 0.5°C, and a decrease of annual rainfall by 0.08 mm d−1 may lead to a decrease of runoff by 25‐30 per cent in small watersheds of Hungary.
Landscape ecological and spatial impacts of climatic change in two areas in the Netherlands
Authors: Jongman Rob H. G. , Souer Martin A.
Published: February 2007

The possible impact of climatic change on the water balance is analysed for the River Dommel and the Veluwe, an area drained by many very small brooks. A water balance is calculated for the winter and the summer period. With the help of four scenarios, based on GCMs, climate data from the dry year 1976 and land use scenarios the impact of climatic change and a possible superposed effect of acid precipitation is analysed. The results show that although the yearly changes in the water balance are small in some cases, in all cases the fluctuations in the water balance between winter and summer period increase. Changes in precipitation and evapotranspiration are multiplied in water storage and runoff. This will have consequences for water use planning and management.
Superposition of aeolian dust ripple patterns as a result of changing wind directions
Authors: Goossens Dirk
Published: February 2007

The effect of a change of wind direction on the orientation (and some other morphometric characteristics) of aeolian dust ripples is investigated. Ripple formation is simulated in a wind tunnel on surfaces that are already characterized by a previously established rippling. The effect of a wind rotation of 45 degrees, 90 degrees, and 180 degrees is examined. It is found that wind rotations of 45 and 180 degrees will lead towards a ripple alignment perpendicular to the last air flow. A wind rotation of 90 degrees, however, leads towards a ripple alignment perpendicular to the resultant wind direction. The faster the wind blows, the more this effect is expressed. No distinct relationship exists between the asymmetry of a dust ripple (and a dust ripple field) and the direction of the wind blowing as the ripples formed. As the orientation and asymmetry of aeolian dust ripples do not necessarily reflect the air flow direction during which the ripples formed, great care should be taken when reconstructing wind directions from such aeolian ripples.
Coarse cliff‐top aeolian sedimentation in northern Gaspésie, Québec (Canada)
Authors: Hétu Bernard
Published: February 2007

This paper deals with the effects of wind on rockwall dynamics. On 5 and 6 January, 1988 very strong northwest winds (blizzard) were blowing onto the rockwall of Mount Saint‐Pierre (alt.: 424 m), Gaspésie, Québec (Canada). The most violent recorded squall reached 99·4 km h−1. During this event, the summit plateau received a large amount of aeolian sediments originating from the shale rockwall that forms the mountain's northwest side. In the 15 to 20 m wide by 75 m long belt located along the top of the rockwall, over a 1200 m2 area, a continuous layer of debris completely covered the snow. This layer of debris had a mean thickness of 11·4 mm, which represents an accumulated volume in the order of 13 m3. Largely dominated by sand and granules (2–4 mm), the 28 samples collected for grain‐size analysis also contained numerous thin shale flakes, many of which were longer than 10 mm. The largest flake measured had a width of 134 mm and a weight of 164·3 g. Six available 14C dates provide information concerning mean cliff‐top aeolian sedimentation rate for the last thousand years (c. 1·8 mmyr−1).
Hydrodynamics of salt marsh creek systems: Implications for marsh morphological development and material exchange
Authors: French J. R. , Stoddart D. R.
Published: February 2007

Integrated ebb‐aligned drainage systems are a feature of tide‐dominated marshes, and are generally regarded as major conduits for material exchange. In north Norfolk, highly unsteady creek flows exhibit well‐developed velocity and stress transients which result from the discontinuous nature of the tidal prism and the interaction of shallow water tidal inputs with hydraulically rough vegetated surfaces. Marsh morphological development is governed by a form‐process feedback, in the sense that the marsh surface acts as a topographic threshold separating the depositional regime of below‐marsh tides from the erosional (ebb‐dominated) regime of over‐marsh tides. Vertical marsh growth results in increasing intermittency of creek sediment transport. Furthermore, velocity transients are associated with large discharges which must be allowed for in material flux computations. Creek flux measurements are not in themselves sufficient to estimate total material budgets, since a large proportion of tidal exchange may take place via the marsh edge. Such studies should focus instead on direct measurement of marsh surface processes. These findings have relevance beyond this back‐barrier setting to marshes of different geometry, occupying a broad range of the tidal energy spectrum.
Photogeological study of cenozoic landform evolution in the Cooktown area, North Queensland, Australia
Authors: Nash C. R.
Published: February 2007

The Great Escarpment of the eastern Cape York Peninsula of far northeast Australia consists of two parallel, offset segments. In the hinterland of Cooktown, these segments are separated by the Mesozoic Laura Basin. To the west of the Basin, the Great Escarpment appears to have evolved on a tiltblock associated with Cenozoic normal faulting along the Palmerville Structure, a major north‐south tectonic feature forming the western margin of the Basin. To the east of the Basin, the Great Escarpment appears to have developed along a north‐northwest axis of upwarping. The existence of this axis is supported by evidence of drainage capture, by the association between the axis and Quaternary volcanism and by fracture patterns in the Mesozoic sandstones along the line of the axis. The eastern segment of the Escarpment appears to be younger than the western. This model supports an earlier hypothesis of escarpment formation in the region as a result of en echelon double lines of uplift.
Lateral sediment transport by bedforms in a meander bend
Authors: Kisling‐Møller Jørgen
Published: February 2007

Bedforms and their migration are among the most important features determining bed load transport on point bars in sand‐bedded rivers. A case study has been carried out in the Danish river Gels Å in a bend with equilibrium point bar topography. Bedforms (dunes) were repeatedly surveyed to determine the bedform migration on the point bar surface. Bedforms occur in two categories in the bend: primary dunes and secondary dunes migrating transversely in the troughs between primary dunes. The study shows that the migration of these bedforms can account for the entire lateral transport known to concentrate the transport in the convex half of the cross section at the bend exit. The bedform transport is induced by both dune categories, partly by turning of the primary dunes towards the convex bank and partly by the migration of secondary dunes. In certain areas, the two categories operate together and thus make the lateral transport particularly large; it is shown that almost 60 per cent of the entire lateral transport in the bend takes place within less than 30 per cent of the streamwise extent of the point bar.
Correlation between rainfall and dust occurrence at mildura, Australia: The difference between local and source area rainfalls
Authors: Yu B. , Neil D. T. , Hesse P. P.
Published: February 2007

In studies of temporal variation in dust activity, rainfall recorded at the same location as the dust events (local rainfall) has commonly been used as a climatic control variable. The main objectives of this note are to test the validity of using local rainfall and to determine the improvement in the relationship between rainfall and dust activity that could be achieved by using regional rainfall in the dust source area. For the period 1960‐1989 at Mildura, Australia, the likely dust source area was identified by analysing wind direction during dust events. It was found that a marked improvement in the correlation between dust activity and antecedent rainfall can be achieved by using the regional source area rainfall rather than local rainfall. The improved correlation suggests that widespread drought is more important than local below‐average rainfall in intensifying dust activity.
Bulk sampling of coarse clastic sediments for particle‐size analysis
Authors: Gale Stephen J. , Hoare Peter G.
Published: February 2007

A guide is provided to the minimum sample masses required to obtain reproducible measures of the particle‐size distributions of coarse sediments. This is based on studies of the actual particle‐size distributions of a range of clastic deposits. Procedures are given to enable representative bulk samples of tills, fluvial gravels and beach gravels to be taken.
Geomorphic application of the hausdorff‐besicovich dimension
Authors: Outcalt Samuel I. , Melton Mark A.
Published: February 2007

An algorithm was developed and tested to produce a useful description of natural terrain texture. First, orthogonal calculation of the variance spectrum of an elevation matrix of a square terrain sample was made using a variation of standard methods to eliminate directional effects. Second, the slope of the log‐log spectrum‐wavelength diagram was used to calculate the Hausdorff‐Besicovitch (H‐B) dimension of the terrain sample according to Voss' formula.

The algorithm was tested on samples from a 60 km × 60 km digital terrain model from Death Valley, California, and Las Vegas, Nevada, U.S.A. Three 12 km × 12 km samples showed systematic variations in both the spectral signature and H‐B dimension. One of the terrain samples was manipulated by smoothing and simulated erosion to test the sensitivity of the dimension. A sloping artificial surface was subjected to several cycles of synthetic fluvial erosion with dimension increasing with erosion duration (age). A smoothed 60 km × 60 km terrain model was subjected to extended cycles of synthetic erosion which produced a Pali‐type landscape typical of the Island of Kauai.
Geomorphology and hydrology of upper sinking cove, cumberland plateau, Tennessee
Authors: Davis Jerry D. , Brook George A.
Published: February 2007

Upper Sinking Cove, dissecting the eastern escarpment of the Cumberland Plateau, is characterized by a multiple aquifer, predominantly vadose hydrologic system with minor surface components. There is a central trunk channel along the axis of the cove and a network of independent tributaries. Aquitards within the limestones, particularly Hartselle Formation shales, have influenced both cave and surface landform development by perching ground waters and slowing the vertical growth of closed depressions. Long‐term solutional denudation in the portion of the cove underlain by limestones (40 per cent) is an estimated 56 mm per 1000 years, suggesting that karst development began 15–16 million years ago. Despite lower soil CO2 and spring water hardness, 61 per cent of annual denudation occurs in the six winter months when 76 per cent of yearly runoff occurs. Landform development in Upper Sinking Cove appears to have begun as stream erosion carved a valley first in the sandstone caprock of the escarpment and later in the underlying Pennington Formation limestones containing numerous shale layers which promoted surface stream flow. Eventually stream erosion exposed the massive Bangor limestones which allowed deep ground water flow. Surface streams were pirated underground with the eventual formation of the chain of three closed depressions which constitute Upper Sinking Cove.
The influence of soil interstitial waters on the physicochemistry of major, minor and trace metals in stream waters of the green lakes valley, Front Range, Colorado
Authors: Litaor M. Iggy
Published: February 2007

The influence of soil interstitial waters on the physicochemical characteristics of major, minor and trace metals in stream waters of an alpine watershed, Front Range, Colorado was assessed. Dissolution of Ca‐aluminosilicate minerals, ion exchange reactions and the magnitude of solute flux within the alpine soil environment account for most of the observed concentrations of major, minor and trace metals in the alpine stream waters. The rate of mineral dissolution and magnitude of solute flux during the summer of 1989 was greatly affected by anthropogenic disturbance which resulted in large amounts of colloidal material and freshly exposed mineral surfaces. The alpine ecosystem responded very quickly to this disturbance. The magnitude of solute flux in the soil environment was also highly dependent on the duration and intensity of rain events, as well as the location of the site along the slope. Transport of most trace metals in the stream waters was achieved by adsorption onto colloidal surfaces of Al–Si hydroxides smaller than 0·45 μm.
Deformation‐induced microstructures in soils affected by mass movements
Authors: Bertran Pascal
Published: February 2007

The soil deformation produced by mass movements gives rise to specific microscopic features. The study of some markers of deformation, such as the orientation of rigid clasts and the morphology of fine‐grained intercalations, indicates that, in most cases, mass movements can be related to simple shear. The development of these features varies according mainly to the type of mass movement (solifluction, debris flow or earth slide). Different factors play a significant role in their formation: intrinsic soil characteristics such as the grain size of the matrix, water content and matrix/element viscosity ratios, and external factors such as the intensity and homogeneity of deformation. A careful study of the microscopic features leads to a better understanding of the dynamics of mass deposits.
The description and representation of particle shape
Authors: Benn Douglas I. , Ballantyne Colin K.
Published: February 2007

Despite widespread agreement on the value of shape analysis in the study of sediments, methods of representing and summarizing data have proved difficult to standardize. This paper shows that Sneed and Folk ternary diagrams provide an appropriate standard method of representing data and a rational basis for the choice of descriptive indices and analytical methods. Such diagrams have the unique quality of representing the variation of particle shapes without bias or distortion, unlike alternative diagrams (e.g. biaxial Zingg plots). Simple descriptive shape indices plot on Sneed and Folk diagrams as straight lines, and behavioural indices (e.g. sphericity) as curves. No index or pair of indices can be regarded as ‘optimum’ in all situations: indices should be chosen with reference to particular data distributions and specific research aims. The use of ternary diagrams in studies of clast shape is illustrated using data from Slettmarkbreen, Norway.
Fluvial processes in a forested anastomosing river: Flood partitioning and changing flow patterns
Authors: Harwood K. , Brown A. G.
Published: February 2007

In an effort to further our understanding of multiple channel systems, this paper presents data on the flood response of channels in one of the last wooded, semi‐natural anastomosing systems in Europe. The Gearagh, Ireland, is characterized by hundreds of small islands separated by interconnected channels of low slope. These include channels that cross islands at right angles to the main flow and blind anabranching channels. Islands are relatively stable and wooded, with evidence of division by channel erosion and growth by in‐channel sedimentation. Four active zone cross‐profiles were surveyed, each containing between seven and 13 channels. Velocities were measured in several channels before and during two separate floods. From these observations channels have been categorised into three types: fast (shallow and trapezoidal); slow (deep and more irregular); and flood channels. During the floods, interchannel flows were caused by variations in water surface elevations due to backing‐up behind debris dams, and it is suggested that this is the origin of the anomalous cross‐island channels and one cause of island division. Another potential cause of island division, blind anabranching channels, is the result of concentrated bank scour between root masses. Biotic components such as debris dams, tree root masses and tree‐throw pits play a key role in the partitioning of flow, and cause variations in channel velocities and the overbank velocity distribution. The implications of these observations for channel pattern maintenance are briefly discussed.
The analysis of turbulence time series: Statistical and correlation approaches using the minitab package
Authors: Clifford N. J.
Published: February 2007

The theoretical basis and use of statistical and correlation approaches for the analysis of turbulence time series are described. In particular, the analysis of data from high frequency current meter measurements using MINITAB is presented and the data files and analytical routines are included on the software disk.
Time series analysis using spectral techniques: Oscillatory currents
Authors: Hardisty Jack
Published: February 2007

The use of time domain and frequency domain techniques in the analysis of geomorphological time series is discussed and the techniques of spectral analysis are introduced. An Excel worksheet is used to analyse wave‐current data from Slapton Sands in Devon and the advantages and limitations of the technique are listed.
Hydrochemistry of carbonate terrains in alpine glacial settings
Authors: Fairchild Ian J. , Bradby Lawrence , Sharp Martin , Tison Jean‐Louis
Published: February 2007

Nearly 200 analyses of meltwaters, ice and snow from three alpine glacial sites in carbonate terrain are summarized and discussed in terms of sources of solutes and kinetic controls on the progress of weathering reactions. Most data derive from the Swiss Glacier de Tsanfleuron which is based on Cretaceous and Tertiary pure and impure limestones. Two other sites (Marmolada, Italian Dolomites and the Saskatchewan Glacier, Alberta) are based on a mixed calcitic‐dolomitic substrate.

Most solutes originate from carbonate dissolution; moreover, where pyrite is present its oxidation supplies significant sulphate and forces more dissolution of carbonate. The ratios Sr2+/Ca2+ and Mg2+/Ca2+ are much higher in Tsanfleuron melt‐waters than local bedrock, a phenomenon that can be reproduced in the laboratory at small percentages of dissolution. These anomalous ratios are attributed to incongruent dissolution of traces of the metastable carbonates Mg‐calcite and aragonite. These phases also provide Na+ to solution. K+ is argued to originate mainly by ion‐exchange on clays with solute Ca2+. Quartz and very minor feldspar dissolution are also inferred. Locally enhanced input from atmospheric sources is recognized by high Cl− and associated Na+.

The progress of weathering reactions has been evaluated by the trends in the data, computer modelling and some simple laboratory experiments. The most dilute samples show a trend towards removal of CO2 to low partial pressures (c. 10−5.5 atmospheres), reflecting initially rapid carbonate dissolution and relatively slow dissolution of gaseous CO2. Later addition of atmospheric CO2 or acid from pyrite oxidation allows further carbonate dissolution, but solutions show a wide range of saturations, and CO2 pressures as high as 10−2.2 where pyrite oxidation is important.

In a carbonate terrain, measurement of electroconductivity (corrected to 25°C) and alkalinity in the field allows the following preliminary deductions (where meq stands for milliequivalents): magnified image where S is the minimum meq(Ca2+ + Mg2+) produced by simple dissolution of carbonate unconnected with pyrite oxidation. As with any proxy method, these deductions do not remove the need for chemical analysis of waters in a given study area.
Loess accumulation and soil formation in central kansas, United States, during the past 400 000 years
Authors: Feng Zhao‐Dong , Johnson W. C. , Sprowl D. R. , Lu Yanchou
Published: February 2007

Based on interpolation of thermoluminescence dates and the mean accumulation rate of 0.034 mm yr−1, four cycles of pedogenic CaCO3accumulation are found within the Loveland Loess: 415–325 ka, 325–250 ka, 250–195 ka and 195–95 ka. The four CaCO3peaks correspond chronologically to marine oxygen isotope stages 11, 9, 7 and 5, respectively. The early Wisconsin (95–70 ka) was characterized by sand dune activity. The reddish pedocomplex was formed from 70 to 35 ka under relatively warm and moist climatic conditions with a very slow rate of silt accumulation (0·016 mm yr−1). The Gilman Canyon pedocomplex, enriched in organic matter and dated at 35–20 ka, was formed under a strong physical weathering regime and a relatively high rate of silt accumulation (0·15 mm yr−1), indicating a windy, relatively moist, probably cool environment. It developed when the Laurentide ice sheet was advancing and dust content in Greenland ice core was low. The Peoria Loess was accumulated at a rate of 0·3 mm yr−1in central Kansas under cold dry conditions when the ice sheet fluctuated around its maximum position and the dust content in the Greenland ice core was the highest. Even the warm substage around 13 ka has some corresponding evidence in the central Great Plains. The well‐developed Brady Soil, dated at 10·5–8·5 ka, indicates that the early Holocene was the optimal time for soil development since 20 ka. The poorly weathered Bignell Loess might have been deposited during the Altithermal Period from 8·5 to 6 ka.
Effects of rock fragment size and cover on overland flow hydraulics, local turbulence and sediment yield on an erodible soil surface
Authors: Bunte Kristin , Poesen Jean
Published: February 2007

The interactions between overland flow hydraulics and sediment yield were studied in flume experiments on erodible soil surfaces covered by rock fragments. The high erodibility of a non‐cohesive fine sediment (D50 + 0·09mm) permitted the effects of local turbulence and scour on sediment yield to be examined. Overland flow hydraulics and sediment yield were compared for experiments with pebble (D50 + 1·5cm) and cobble (D50 + 8·6cm) rock fragment covers. Cover percentages range from 0 to 99 per cent. Rock fragment size strongly affects the relations between flow hydraulics and rock fragment cover. For pebbles spatially‐averaged hydraulic parameters (flow velocity, flow depth, effective flow width, unit discharge, total shear stress, Darcy‐Weisbach friction factor, percentage grain friction and grain shear stress) vary most rapidly within cover percentages at low covers (power functions). In contrast, for cobbles these parameters vary most rapidly within cover percentages at high covers (exponential functions). As the type of the function that describes the relation between flow hydraulics and cover percentage can be deduced from the ratio of rock fragment height to flow depth, the continuity equation can be employed to determine the actual coefficients of the functions, provided the regression of one hydraulic parameter (e.g. flow velocity) with cover percentage is known and a good estimate exists for two values of another hydraulic variable for a low and a high cover percentage.

The variation of sediment yield with cover percentage is also strongly dependent on rock fragment size, but neither the convex‐upward relation for pebbles, nor the positive relation for cobbles can be solely attributed to the spatially averaged hydraulics of sheet‐flow. Rock fragments induce local turbulence that leads to scour hole development on the stoss side of the rock fragments while deposition commonly occurs in the wake. This local scour and deposition substantially affects sediment yield. However, scour dimensions cannot be predicted by spatially averaged flow hydraulics. An adjustment of existing scour formulas that predict scour around bridge piers is suggested. Sediment yield from non‐cohesive soils might then be estimated by a combination of sediment transport and scour formulas.
Dissolved oxygen variations in alpine glacial meltwaters
Authors: Brown G. H. , Tranter M. , Sharp M. J. , Davies T. D. , Tsiouris S.
Published: February 2007

Recent models of chemical weathering in alpine glacial meltwaters suggest that sulphide oxidation is a major source of solute in the distributed component of the subglacial hydrological system. This reaction requires O2, and may lower dissolved oxygen levels to below saturation with respect to the atmosphere. This should result in an inverse association between SO72‐ and dissolved oxygen saturation. However, measurements of O2 saturation in bulk meltwaters draining the Haut Glacier d'Arolla, Switzerland, show that there is a positive association between SO42‐ and O2 saturation. The O2 content of glacial meltwaters depends on the initial content of snow and icemelt, which may be controlled by the rate of melting, and the kinetic balance between O2 losses (e.g. sulphide oxidation, microbial respiration) and gains (e.g. diffusion of O2 into solution).
Duricrust development and valley evolution: Process–landform links in the kalahari
Authors: Nash David J. , Shaw Paul A. , Thomas David S. G.
Published: February 2007

Duricrusts are an important landscape component of the Kalahari region of central southern Africa. Their exposures within the dry valleys (mekgacha) of the Kalahari provide some of the most widespread surface outcrops of the terrestrial Jurassic to Holocene Kalahari Group sediments. Exposures have been extensively used in the construction of lithostrati‐graphic sequences, on the assumption that valley systems have incised their courses through a pre‐existing duricrust sequence. Recent work, however, has identified the role of groundwater erosion processes in valley development, which may have influenced duricrust formation.

Studies of duricrusts from boreholes drilled within two mekgacha show that duricrust type is intrinsically related to the presence of a valley. Analyses of calcretes and silcretes in a series of profiles and thin sections from the Letlhakeng area of Botswana also indicate extensive alteration and diagenesis in association with former higher water tables. Sedimentary sequences within duricrust host materials can be identified but there is no evidence for correlation of duricrust cements between exposures. Profile studies from the Auob Valley in Namibia, however, suggest that this valley has incised through a sequence of duricrusts. Caution is advised in future attempts to correlate duricrust types on the basis of valley exposures, with the recommendation that where such exposures are used in a lithostratigraphic context, only duricrust host material characteristics and not cementing materials should be considered.
The age of alluvial fan deposition at a site in the southern uplands of scotland
Authors: Tipping Richard , Halliday Stratford P.
Published: February 2007

The age of a large alluvial fan debouching onto the valley floor of the River Tweed, in southern Scotland, and the sequence of events relating to this, are investigated using geomorphological, sedimentological, palynological, archaeological and radiocarbon dating evidence. Prior to fan deposition, the Tweed valley floor seems to have been covered by a wooded peat at a time of low fluvial activity. The fan commenced deposition in the 11th century AD, and appears to have been a local event, the Tweed showing no response to this accelerated sedimentation. Later, perhaps 200 years later, the Tweed commenced overbank deposition of the only Flandrian terrace preserved. Local proxy data are examined in order to define the causes of these events, but difficulties in temporal correlation, despite the good resolution of the radiocarbon chronology, mean that the causes of these events remain unknown.