bluuebunny/crossref_metadata_2025_split huggingface dataset:
Till fabric associated with deformable beds
Authors: Hart Jane K. 
Published: February 2007

AbstractThis paper investigates the development of till fabric associated with glaciers overlying deformable beds. First, the till fabrics from both modern and ancient, soft bed and hard bed subglacial environments are investigated, and then soft bedded sites with specific strain histories are examined. The results indicate that lodgement tills had a strong fabric, whilst there is a wide range of much weaker fabric strengths associated with soft bed tills. It is suggested from a theoretical study of soft bed till deposition that longitudinal and vertical processes in the subglacial deforming layer are important in fabric development. Field sites were chosen to isolate these two factors, and fabrics investigated in areas of known relative shear strain, and known relative thickness of the deforming layer. The results indicate that: (1) for a fixed deforming layer, fabric strength does increase with increasing deformation (except at very high strains where the development of a transverse fabric can lead to a reduction in the overall fabric strain); and (2) lodgement tills and soft bed tills associated with a thin deforming layer have a high fabric strength, whilst soft bed tills associated with a thick deforming layer have a low fabric strength. Where the deforming layer is thin, clasts are oriented parallel with the glacier direction either by lodging against a hard bed or ploughing against a soft bed. However, where the deforming layer is thicker and shear strains are high, melt‐out processes encourage a parallel fabric, but the increased shear strain and changes in the deforming layer thickness cause the clasts to develop both a parallel and transverse fabric. These processes combine to reduce the overall fabric strength. Till fabric studies are a further sedimentological technique to separate the depositional processes associated with a homogeneous till.
Reply: Bulk sampling of coarse clastic sediments for particle‐size analysis
Authors: Gale Stephen J. , Hoare Peter G. 
Published: February 2007

AbstractThe work of Gale and Hoare (1992) provides a guide to the minimum mass of bulk sample required to obtain a reproducible measure of the complete particle‐size distribution of coarse clastic sediments such as till, fluvial gravel and beach gravel. Dunkerley (1994) makes a number of criticisms and misrepresentations of this procedure. These are systematically refuted and corrected here, and further data obtained from till and beach gravel are provided to support the criterion adopted by Gale and Hoare (1992) for sample reliability. The procedure of Gale and Hoare (1992) is confirmed as a practical guide to the mass of bulk sample required to obtain a reliable measure of the particle‐size distribution of coarse clastic sediment.
Environmental controls on blowing dust direction at lubbock, Texas, U.S.A.
Authors: Lee Jeffrey A. , Evan Moffett K. , Allen B. L. , Peterson Richard E. , Gregory James M. 
Published: February 2007

AbstractBlowing dust is a common phenomenon at Lubbock, Texas, on the Southern High Plains. The directional variability of blowing dust estimated with the ‘sand rose’ technique, using wind speed and direction data, suggest that dust transport occurs from all directions. An empirical method of determining directional variability using meteorological data on visibility reductions due to blowing dust, however, indicates that most dust comes from the west and south‐west. In addition to wind speed and direction, other environmental factors must be considered in explaining the spatial pattern of dust transport. Soil erodibility is variable in the region, with the most extensive area of highly erodible soils to the west and south‐west of Lubbock. Rangeland dominates land use to the east, while agriculture is extensive to the north, west and south. Local farming techniques leave bare soil during the winter and spring, when most airborne dust is produced and also when strong winds are common from the west and south‐west. Soil moisture is lowest to the southwest of Lubbock, which leads to a decrease in soil structure and an increase in the potential for wind erosion in that direction. Relative humidities affect threshold wind speeds and are lowest during March and April, when winds are common from the west and south‐west. The spatial and seasonal variability and interactions between many factors, both natural and human‐controlled, must therefore considered in explaining the directional variability of aeolian sediment transport at Lubbock.
Breaching in a wave‐dominated barrier spit: The trabucador bar (north‐eastern spanish coast)
Authors: Sánchez‐Arcilla Agustín , Jiménez José A. 
Published: February 2007

AbstractThe Trabucador Bar is a barrier coast linking the main lobe of the Ebro Delta with its southern spit. This coastal stretch, which may be considered as a microtidal transgressive barrier, is the most vulnerable area of the deltaic coast to storm‐induced geomorphologic changes. During the second week of October 1990 a severe storm affected the Ebro Delta causing serious erosion, in which the Trabucador Bar was one of the most damaged zones. A breach 800 m long and with a maximum depth of 0·4 m below the mean water level was created. During the breaching process approximately 70 000 m3 of sand were removed from the subaerial barrier in a few hours. Three factors are normally responsible for the loss of sediment, longshore transport gradient, offshore transport and overwash processes, most of the eroded sediment (60 000 m3) was transported towards the inner bay due to overwash processes. The post‐storm recovery of the zone was slow and far from complete, as the breach remained a conduit for onshore sediment transport under a regime of breaking and reforming waves. An artificial dune was subsequently constructed to close the breach and thus allow beachface recovery.
Application of the qda–md method of environmental discrimination to particle size analyses of fine sediments by pipette and sedigraph methods: A comparative study
Authors: Duck R. W. 
Published: February 2007

AbstractThe results of particle size analyses by the low‐technology pipette method and by the modern SediGraph, of a suite of fine lacustrine bottom sediment samples, are compared. Good correlations between the two data sets are observed, although the SediGraph consistently indicates finer grain sizes and better sorting of distributions. The QDa‐Md method of environmental discrimination, originally established on the basis of traditional methods of size analysis, is found to be sufficiently versatile to accommodate the SediGraph data into the appropriate trend envelopes, despite the considerable differences in derived grain size parameters.
Fluvial chronology and valley floor evolution of the upper bowmont valley, borders region, Scotland
Authors: Tipping Richard 
Published: February 2007

AbstractTwo major fluvial terrace surfaces, and four less significant surfaces, are identified by aerial photographic interpretation, field mapping and levelling on one c. 2 km long reach of the upper Bowmont Water, an upland stream draining the northern Cheviot Hills, Scotland.The oldest terrace surface remains undated. Cartographic, radiocarbon and palynological dating suggest that later terraces formed very recently, within the last 250 years, with the most prominent terrace fill having aggraded in the 18th century. Incision below this terrace surface is dated to approximately the end of the 18th century, correlated with channel trenching at other sites in the region. Detailed palaeoecological and documentary evidence is used to examine whether climatic or land‐use changes might have instigated aggradation, and a link with increased precipitation and flooding during part of the ‘Little Ice Age’ is suggested.
Quantitative relationships between uplift and relief parameters for the Southern Alps, New Zealand, as determined by fission track analysis
Authors: Tippett J. Mark , Kamp Peter J. J. 
Published: February 2007

AbstractThe Southern Alps mountain chain, New Zealand, has formed as a consequence of late Cenozoic collision of the continental parts of the Pacific and Australia plates. Fission track analysis has yielded estimates of the amount, age of initiation, and rate of late Cenozoic rock uplift for 82 surface samples taken from transects across the Southern Alps. The mean surface, summit and valley elevations in the vicinity of each of the rock sample sites have also been measured. Regression of the geomorphic variables on the uplift variables has been used to establish quantitative relationships between uplift and geomorphology. There are strong and consistent linear associations between uplift and the elevations of the mean surface, summits and valleys. The preferred regression models have uniform slope but varying elevation response between transects. Substitution of space for time has allowed the evolution of landforms to be studied.To the east of the Main Divide, elevation and relief are proportional to, and closely related to, the age of initiation of rock uplift (‘uplift age’) and the amount of rock uplift (r2 > 0·8). Mean surface uplift was delayed for ∼2 Ma after the start of rock uplift, a result of the stripping of a soft cover rock succession that, prior to rock uplift, overlaid the harder greywacke basement. Inter‐transect variations in regression response and x‐intercept are inferred, therefore, to reflect the variable preuplift thickness of cover rocks. However, the regular regression slope for the transects reflects the consistent nature of the interaction between uplift and the erodibility of greywacke basement. Uplift of the mean surface proceeded at 0·4 km/km and 0·4 km/Ma of rock uplift, while the rock uplift rate was 0·8 km/Ma. Summit elevations have increased at a rate of 0·6 km/Ma and valley elevations have increased at 0·2 km/Ma. Regression lines relating mean surface, summit and valley elevations to rock uplift and uplift age diverge from common intercepts; it is concluded, therefore, that the mountains east of the Main Divide have continued to increase in elevation and relief and change in form over time since the start of mean surface uplift. Mountain elevation has little relationship with late Cenozoic mean rock uplift rates of 0·8–1·0 km/Ma or inferred contemporary rock uplift rates (r2 ∼ 0·3).In contrast, to the west of the Main Divide, elevation is shown to be closely related to rock uplift rate (r2 > 0·3).In contrast, to the west of the Main Divide, elevation is shown to be closely related to rock uplift rate (r2 > 0·8). Transects with higher rock uplift rates support higher topography. Landforms are therefore in a stable equilibrium with rock uplift rate, and the landscape contains no residual evidence of the total amount of rock uplift, or the age of uplift. Lithological variation appears to have no relationship with elevation.
The nature and pattern of debris liberation by salt weathering: A laboratory study
Authors: Goudie Andrew S. , Viles Heather A. 
Published: February 2007

AbstractA laboratory simulation of salt weathering was used to ascertain the effects of sodium sulphate and sodium carbonate under ‘Negev’ conditions using a single immersion technique. Three main points were addressed: what are the grain size and textural characteristics of the debris liberated from limestones and a sandstone, what do scanning electron microscope observations of the weathered samples tell us about the decay processes involved, and how does the rate of debris liberation change during the course of 100 cycles? The grain size characteristics of the liberated debris tended to be multimodal and were related to the original petrological characteristics of the rock. Large amounts of fines were produced which are believed to be analogous to the ‘rock flour’ of arid areas. Blistering was also observed. Scanning electron microscope analysis revealed differences in the style of attack for different rock types and salt treatments, and revealed the pattern of salt crystallization in pores and the nature of cracking. The rate of debris liberation tended to decline or remain constant through time. The reasons for this remain obscure, but it is evident that diurnal cycles of temperature and humidity change can cause continuing rock weathering long after the initial input of salt to the rock has taken place.
A partial explanation of the dependency of hydraulic conductivity on positive pore water pressure in peat soils
Authors: Baird Andrew J. , Gaffney Simon W. 
Published: February 2007

AbstractPart of the relationship between positive pore water pressures and hydraulic conductivity in peat soils may be explained by accumulations of methane bubbles. We show how compression and expansion of gas bubbles with changes in pore water pressure could cause changes in hydraulic conductivity and thus help to explain some observations of dependency of hydraulic conductivity in peats on pore water pressure. Consideration is also given to the effect on hydraulic conductivities of methane gas going into solution with increase in pore water pressure.
Global positioning system: An effective way to map a small area or catchment
Authors: Fix Ronald E. , Burt T. P. 
Published: February 2007

AbstractThe Global Positioning System (GPS) is an established method for establishing high accuracy horizontal and vertical control points over large areas. Recent improvements in receiver technology, differential surveying and software have made the use of GPS technology more practical for smaller projects. This paper compares different GPS methods with occupation times of 2 s, 2 min and 12 min using an existing control network, and the gathering of topographic data from a difficult field site. Two examples are given, one in East Texas, demonstrating the speed and accuracy of different techniques, and the other in the Quantock Hills in Somerset.
Modelling the time‐varying extent of groundwater seepage on tidal beaches
Authors: Turner Ian L. 
Published: February 2007

AbstractThe outcrop of groundwater on tidal beaches distinguishes an upper unsaturated region from a lower saturated region of the intertidal profile. Since the 1940s, it has been recognized that the extent of groundwater seepage at the beach face is one factor determining the tendency for erosive or accretionary conditions to prevail. As a primary step towards incorporating bed saturation characteristics within cross‐shore sediment transport models, this paper (and accompanying program disk) details a simple model to simulate the time‐varying extent of seepage face development across tidal beaches. From a comparison with field results obtained on the macrotidal Central Queensland (Australia) coast, the model appears to provide an encouraging degree of predictive capability. The model also assists in highlighting the sensitivity of seepage face development to varying beach face, tide and wave characteristics.
Semi‐Lagrangian advection on a spherical geodesic grid
Authors: Carfora Maria Francesca 
Published: February 2007

AbstractA simple and efficient numerical method for solving the advection equation on the spherical surface is presented. To overcome the well‐known ‘pole problem’ related to the polar singularity of spherical coordinates, the space discretization is performed on a geodesic grid derived by a uniform triangulation of the sphere; the time discretization uses a semi‐Lagrangian approach. These two choices, efficiently combined in a substepping procedure, allow us to easily determine the departure points of the characteristic lines, avoiding any computationally expensive tree‐search. Moreover, suitable interpolation procedures on such geodesic grid are presented and compared. The performance of the method in terms of accuracy and efficiency is assessed on two standard test cases: solid‐body rotation and a deformation flow. Copyright © 2007 John Wiley & Sons, Ltd.
Upward bias in odds ratio estimates from genome‐wide association studies
Authors: Garner Chad 
Published: February 2007

AbstractGenome‐wide association studies are carried out to identify unknown genes for a complex trait. Polymorphisms showing the most statistically significant associations are reported and followed up in subsequent confirmatory studies. In addition to the test of association, the statistical analysis provides point estimates of the relationship between the genotype and phenotype at each polymorphism, typically an odds ratio in case‐control association studies. The statistical significance of the test and the estimator of the odds ratio are completely correlated. Selecting the most extreme statistics is equivalent to selecting the most extreme odds ratios. The value of the estimator, given the value of the statistical significance depends on the standard error of the estimator and the power of the study. This report shows that when power is low, estimates of the odds ratio from a genome‐wide association study, or any large‐scale association study, will be upwardly biased. Genome‐wide association studies are often underpowered given the low α levels required to declare statistical significance and the small individual genetic effects known to characterize complex traits. Factors such as low allele frequency, inadequate sample size and weak genetic effects contribute to large standard errors in the odds ratio estimates, low power and upwardly biased odds ratios. Studies that have high power to detect an association with the true odds ratio will have little or no bias, regardless of the statistical significance threshold. The results have implications for the interpretation of genome‐wide association analysis and the planning of subsequent confirmatory stages. Genet Epidemiol. 2007. © 2007 Wiley‐Liss, Inc.
A variant of the myosin light chain kinase gene is associated with severe asthma in African Americans
Authors: Flores Carlos , Ma Shwu‐Fan , Maresso Karen , Ober Carole , Garcia Joe G. N. 
Published: February 2007

AbstractAsthma is a complex phenotype influenced by environmental and genetic factors for which severe irreversible structural airway alterations are more frequently observed in African Americans. In addition to a multitude of factors contributing to its pathobiology, increased amounts of myosin light chain kinase (MLCK), the central regulator of cellular contraction, have been found in airway smooth muscle from asthmatics. The gene encoding MLCK (MYLK) is located in 3q21.1, a region noted by a number of genome‐wide studies to show linkage with asthma and asthma‐related phenotypes. We studied 17 MYLK genetic variants in European and African Americans with asthma and severe asthma and identified a single non‐synonymous polymorphism (Pro147Ser) that was almost entirely restricted to African populations and which was associated with severe asthma in African Americans. These results remained highly significant after adjusting for proportions of ancestry estimated using 30 unlinked microsatellites (adjusted odds ratio: 1.76 [95% confidence interval, CI: 1.17–2.65], p = 0.005). Since all common HapMap polymorphisms in ∼500 kb contiguous regions have low‐to‐moderate linkage disequilibrium with Pro147Ser, we speculate that this polymorphism is causally related to the severe asthma phenotype in African Americans. The association of this polymorphism, located in the N‐terminal region of the non‐muscle MLCK isoform, emphasizes the potential importance of the vascular endothelium, a tissue in which MLCK is centrally involved in multiple aspects of the inflammatory response, in the pathogenesis of severe asthma. This finding also offers a possible genetic explanation for some of the more severe asthma phenotype observed in African American asthmatics. Genet Epidemiol 2007. © 2007 Wiley‐Liss, Inc.
The succession above the soft bed and bassy mine in the pennine region
Authors: Eagar R. M. C. 
Published: February 2007

AbstractThe measures between the Soft Bed and the Middle Band Coal of Yorkshire and the equivalents of these seams in Lancashire, the Bassy and Lower Foot Mines, are remarkably uniform. The horizons of two thin Lingula bands, first described by the author from Huddersfield, may be traced, usually as marine shale, northward to Bradford and Burnley, southward to near Sheffield, westward to St. Helens and south‐westward to Goyt's Moss, Derbyshire, where the lower band has yielded Gastrioceras sp. The bands of Lingula divide the measures into three small‐scale cyclic units of sedimentation which contain non‐marine lamellibranchs throughout much of their vertical extent.Studies of faunas from localities which yielded the types of Carbonicola fallax, C. protea and C. haberghamensis Wright are described in some detail. At Feniscowles, near Darwen (type locality for the first two species) it is shown that with passage upward into slightly more coarse grained beds in the lower cyclic unit the small shells of the C. fallax group show an upward increase in H/L ratio with some evidence of a split into two species.The non‐marine succession, of Honley, near Huddersfield, is regionally summarized. Attention is drawn to a maximum of Carbonicola rectilinearis Trueman and Weir in the lower part of the lower cyclic unit and to the marker horizons of Carbonicola discus Eagar and C. haberghamensis Wright in the upper part of the middle unit.Carbonicola pilleolum, the new species described, covers variants previously referred to, or compared with, C. sulcata (Brown).
The structural evolution of north wales
Authors: Shackleton R. M. 
Published: February 2007

AbstractThe Caledonian structures of North Wales were foreshadowed by Pre‐Cambrian structures. A feature of the Caledonian pattern is a deflection of cleavage and fold trends from north‐south, as in Merionethshire, to east‐west, as in Denbighshire. The axis of this deflection trends northwest—southeast from Shropshire to Anglesey; it appears to be wrenched sinistrally along the Bala fault. The vergence of cleavage and folds is generally towards the east and south. Intensity of deformation increases from the foreland (Shropshire) to Anglesey. Late‐Caledonian granite and dolerites are discussed in relation to deformation. Post‐Caledonian events are briefly reviewed.