bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrodynamics of salt marsh creek systems: Implications for marsh morphological development and material exchange
Authors: French J. R. , Stoddart D. R. 
Published: February 2007

AbstractIntegrated 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

AbstractThe 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

AbstractBedforms 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

AbstractIn 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

AbstractA 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

AbstractAn 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

AbstractUpper 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

AbstractThe 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

AbstractThe 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

AbstractDespite 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

AbstractIn 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.
Hydrochemistry of carbonate terrains in alpine glacial settings
Authors: Fairchild Ian J. , Bradby Lawrence , Sharp Martin , Tison Jean‐Louis 
Published: February 2007

AbstractNearly 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

AbstractBased 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

AbstractThe 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

AbstractRecent 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

AbstractDuricrusts 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

AbstractThe 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.