bluuebunny/crossref_metadata_2025 huggingface dataset:
Ferromanganese rock varnish in north Norway: A subglacial origin
Authors: Whalley W. Brian , Gellatly Anne F. , Gordon John E. , Hansom James D.
Published: February 2007

A thin, dark brown rock varnish is described from ice‐smoothed bedrock on the forefield of a glacier in North Norway. It occurs only in narrow strips (ca 100 mm or less wide) which run roughly parallel to the ice front and along the top edges of small treads of a series of bedrock steps. The varnish is hard, thin (< 10 μm) and consists of an iron/manganese deposit, greatly enriched in these elements compared with the composition of the underlying gabbroic bedrock. It is suggested that the varnish formation is due to localized changes in Eh/pH conditions in subglacial regelation ice and meltwater at the top of the bedrock steps. These changes may be due to CO2 and/or O2 degassing from water held at higher pressures under the ice than in cavities downstream where the ice is decoupled from the bedrock. Glacier retreat rates indicate that the varnish has remained exposed subaerially at the surface for about twenty years, and its restricted occurrence suggests that it is not of biological origin but rather is essentially authigenic. Possible subglacial origins for associated iron and silica precipitates are also suggested.
Relative instability of colluvium‐filled bedrock depressions
Authors: Crozier Michael J. , Vaughan Elizabeth E. , Tippett J. Mark
Published: February 2007

Regolith landslides commonly occur in colluvium‐filled bedrock depressions rather than on ridges, spurs, or sites with planar bedrock surfaces. Drained direct shear tests of colluvium from bedrock depressions in Wellington, New Zealand, indicate the presence of cohesion in all samples, suggesting that thickness of accumulated deposits may become a limiting factor for stability. Critical depths for a range of slope angles were calculated (assuming conditions of infinite limiting equilibrium) and compared to the depth/angle relationships for depression and interdepression regolith occurring in the field. The results indicate that, under saturated conditions, interdepression regolith is not thick enough to permit the development of landslides. Colluvium‐filled bedrock depressions, on the other hand, generally exceed critical depth and must be considered susceptible to landsliding in the absence of any significant root cohesion.

The age of deposits and the abundance of unfailed colluvium‐filled bedrock depressions suggest that they have been inactive for most of post glacial time. Stability analysis, verified by observing the occurrence of landslides, indicates that recent instability has been brought about by deforestation.
The development of armour in the Tambo River, Victoria, Australia
Authors: Dunkerley D. L.
Published: February 2007

Present understanding of armour formation and the dynamics of grain entrainment and movement, especially in natural environments with coarse and poorly‐sorted bed material, is still incomplete. There are many details which require further field observation for clarification and hypothesis testing, including aspects of grain interaction during bedload transport. Evidence from the Tambo River suggests that there may be mechanisms of armour development which have significance in certain field situations but which have been relatively neglected in the literature. The particular mechanism envisaged for the Tambo River involves the accumulation on the bed surface of large clasts which had been moving as an overpassing traction carpet. These clasts are not genetically related to the underlying subarmour sediments, but nonetheless act as an armour which protects them from scour, and which hence affects grain mobility and bedload transport rates.
Reconnaissance studies of the tufa deposits of the Napier Range, N.W. Australia
Authors: Viles H. A. , Goudie A. S.
Published: February 2007

Tufas are widespread in the Napier Range of north Western Australia, an area of tropical seasonal climate and savanna vegetation. The major tufa deposits have been mapped and the different forms described. These include drapes on cliffs, cones at cave entrances or the mouths of ephemeral streams, rimstone pools, and tufa dams. There are at least two generations of tufa cone, with the older being heavily calcreted and eroded. Simple geochemical and petrographical data allow comparison between the different types of deposit here and with deposits from other parts of the world. Thin section observations and scanning electron microscopy enable an initial assessment of the role of organic processes in tufa formation. Obvious organic remains are sparse, although many of the active tufas are composed of filamentous microsparite fabrics, suggesting that algae have influenced the geometry of the deposits. However, the identification of various endolithic algae indicates that they may also be actively involved in the degradation of the deposits.
Use of the schmidt test hammer to detect enhanced boulder weathering under late‐lying snowpatches
Authors: Ballantyne Colin K. , Black Nicola M. , Finlay Donna P.
Published: February 2007

Ballantyne et al. (1989) presented data that show a significant reduction in Schmidt hammer rebound values for boulders buried by late‐lying snow. McCarroll (1990) questions these findings on the grounds of sampling design, methodology and unexpectedly rapid weathering of boulders at one recently‐deglaciated site. However, analysis of the data using the procedure recommended by McCarroll yields identical results, and his methodological objections appear groundless. The absence of evidence for reduction of rebound values at snowpatch sites investigated by McCarroll may reflect lack of meltwater runoff beneath snowbeds in permafrost areas. The implied rapidity of weathering on recently‐deglaciated ground requires further investigation.
Seasonal changes in iron transport and nature of dissolved organic matter in a humic river in northern Finland
Authors: Heikkinen Kaisa
Published: February 2007

Changes in the concentration of iron and dissolved organic matter (DOM), and in the colour and fluorescence properties in the River Kiiminkijoki were investigated as functions of the seasonal flow regime over a two‐year period. The iron concentration in filtrates and the ratio of Fe to DOC in the river increased under low flow conditions and decreased during the flood periods. The colour of the dissolved organic matter increased with increasing iron content, the effect being more pronounced during the warm period of the year than in winter. The ratio of fluorescence to DOC increased during the warm period of the year but not in winter, and decreased rapidly with discharge at the beginning of the flood period in autumn. The results give indications of the origin, formation, nature, and fate of the DOM in the river water. Temperature‐dependent microbiological processes in the formation and sedimentation of iron‐organic colloids seem to be important. Estimates are given for the amounts and transport rates of iron discharged into the Gulf of Bothnia by the river.
Rates of tafoni weathering on uplifted shore platforms in Nojima‐Zaki, Boso Peninsula, Japan
Authors: Matsukura Yukinori , Matsuoka Norikazu
Published: February 2007

Many tafoni occur on the faces of marine cliffs on three uplifted shore platforms with different altitudes and with known ages of emergence. The mean value of the ten largest depths of tafoni, D (cm), was obtained and the period of their formation, t (years), was estimated. The relationship between the two variables was found to be D = 20·3 × (1−e−0.005t).
Measurement and calibration of weathering using the schmidt hammer, on wave washed moraines on the upper norrland coast, Sweden
Authors: Sjöberg R. , Broadbent N.
Published: February 2007

The Schmidt hammer has for some years been used to measure the hardness of different rock surfaces and to date relatively boulders in moraine deposits. In this paper applications on isostatically raised boulder‐beaches and rocky shores are described. The research area is the northern Swedish Bothnian coast where present isostatic uplift is between 0.8‐1.0 cm year−1. Elevations above sea‐level can be converted to a timescale. Rebound values (R) of the Schmidt hammer are correlated with the altitude and the degree of rock weathering can be estimated for each site.

Eight sites with boulder‐beaches and nine sites with rocky shores have been analysed. For boulder‐beaches correlation‐coefficients of 0.82‐0.97 for weathering values (R) and the elevations above sea‐level were obtained. For the rocky shores these values were calculated to 0.75‐0.97.

This method has applications in both geomorphology and archaeology. For example, a deep layer of weathered dolerite in the Nordingrå region, which previously has been regarded as a post‐Weichselian formation, can be shown to be of pre‐Weichselian origin. Several archaeological applications are also mentioned in the paper.
Size characteristics of sediment in interrill overland flow on a semiarid hillslope, Southern Arizona
Authors: Parsons Anthony J. , Abrahams Athol D. , Luk Shiu‐Hung
Published: February 2007

This study examines the size characteristics of sediment removed from a semiarid hillslope by interrill overland flow. Rainfall simulation experiments were conducted on a runoff plot 18 m wide and 35 m long established on a piedmont hillslope in southern Arizona. The top of the plot coincided with the hillslope divide, and its outlet was located within a shallow rill. Samples of runoff were obtained from two cross‐sections located in the interrill portion of the plot upslope of the rill and from a calibrated flume through which was directed interrill overland flow reaching the bottom of the plot. Analyses of sediment contained in these samples showed that sediment in interrill flow is finer than the matrix soil. The fineness of the interrill sediment compared to the matrix soil appears to be due to the inability of interrill overland flow to transport the coarser fraction of the sediment supplied to it by raindrop detachment. This finding implies that the rate of soil erosion in interrill areas is not. as is commonly supposed, limited by the rate at which raindrops can detach sediment but by the rate at which they detach sediment of a size that the overland flow is competent to transport. The relative fineness of sediment eroded from this hillslope is consistent with other evidence for the recent evolution of shrub‐covered hillslopes in southern Arizona.
The application of cellular automata to the erosion of landforms
Authors: Smith Roger
Published: February 2007

Two approaches to modelling surface erosion are described which can be used to explain the development of geomorphological features. The first approach uses non‐linear wave theory and shows how surface gradient discontinuities can arise as the erosion of an initially smooth surface proceeds. For isotropic erosion, surface shapes may be predicted by a simple application of the Huyghens wavefront construction and Snell's law at media boundaries. A second approach uses a computational cellular method. The general shapes predicted by the computer simulations are shown to agree with those determined from the wave approach. The application of the cellular method to problems of geomorphological interest are discussed.
The schmidt hammer, weathering and rock surface roughness
Authors: McCarroll Danny
Published: February 2007

Measures of the differential relief of adjacent feldspar and pyroxene grains provide the first clear negative correlation of Schmidt hammer rebound (R‐) values and degree of weathering. However, weathering and roughness are intimately related, so the latter cannot be seen simply as a source of error limiting the utility of the Schmidt hammer. Only where surfaces had similar textures prior to weathering can R‐values be compared directly. Even where surface texture is well controlled, differences in R‐values should be viewed critically rather than assigned indiscriminately to differences in degree of weathering.
Aeolian dust transport and deposition over crete and adjacent parts of the mediterranean sea
Authors: Pye K.
Published: February 2007

Monitoring of dust deposition at several stations on Crete over a three year period has shown that the present‐day depositional flux is of the order of 10‐100 gm−2 yr−1. Most of the dust deposition takes place during a few annual dust [events] which typically last for 1‐3 days. Dust haze episodes are usually associated with southerly or southwesterly winds which transport fine sediment from North Africa. Dust is raised by a wide variety of meteorological conditions which generate strong near‐surface winds in the source areas, but major long‐range transport events are often associated with cold fronts linked to the passage of deep mid‐latitude depressions during winter and spring. Dust haze frequency and deposition rates are highest in western Crete and decrease towards the east, suggesting that transport from Tunisia and neighbouring parts of North Africa is particularly important. The measured rate of dust deposition is well below the minimum level required for loess formation. Deposits which have previously been identified as loess are shown to be uncemented marine marls of Tertiary age. Laboratory analysis of red soils, surface sediments, and bedrock samples has confirmed that many of the soils contain an important aeolian dust component, but it is concluded that a more important source of soil parent material is provided by weathering of local rocks. Many of the soils contain significant amounts of quartz sand which cannot have been transported across the sea from North Africa. Reworking of weathered material and deposited dust is extensive, and is accomplished by both aeolian and fluvial processes. Tectonically‐controlled depressions in the mountains and parts of the coastal lowlands have acted as long‐term sinks in which a thickness of several metres of sediment and soil has accumulated during the Quaternary.
The influence of microform bed roughness elements on flow and sediment transport in gravel bed rivers: Comment on a paper by marwan A. Hassan and ian reid
Authors: Clifford Nicholas J. , Richards Keith S. , Robert Andre
Published: February 2007

Data from Turkey Brook are used to demonstrate that the interaction between gravel bedforms, flow resistance and bedload transport is a dynamic one, both between and within hydrographs. and that creation of a significant component of form drag through construction of microforms (pebble clusters) may precede the eventual break‐up of the bed in a transport event. This process of drag augmentation', which can be seen as a feedback mechanism delaying transport and can be likened to dilation of a soil tested in a direct shear apparatus, itself appears to be dependent on the characteristics of turbulence, and therefore involves feedback at a finer resolution than envisaged by Hassan and Reid (1990).
Segmentation of alluvial fans in death valley, california: New insights from surface exposure dating and laboratory modelling
Authors: Leb. Hooke Roger , Dorn Ronald I.
Published: February 2007

Laboratory experiments, recent paleoenvironmental analyses of rock varnish, and surface exposure dating of geomorphic units have led to new insights into the process of entrenchment and segmentation of alluvial fans, and into the history of Quaternary sedimentation in Death Valley. Entrenchment begins at the fanhead. As the trench deepens, its down‐slope end migrates down‐fan, taking several tens of thousands of years to reach lower parts of the fan. Laboratory experiments suggest, however, that a new segment begins to grow at the toe long before the trench reaches this part of the fan. Furthermore, the initial slope of the segment is not the equilibrium slope. Field evidence supports this model. The tectonic tilting that caused entrenchment and segmentation in Death Valley may have been triggered by loading of the valley with water.

Sedimentation on the salt pan in southern Death Valley is not, at present, in equilibrium with that on the fans. Rather, it seems to be adjusting to an increase in the amount of fine material reaching the playa, due in part to breaching of the outlet of Lake Tecopa somewhat after 600 ka BP, and in part to subsidence of different parts of the valley at different rates. Failure to recognize this disequilibrium resulted in errors in earlier estimates of the age of the segmentation events.
Modelling floodplain flows using a two‐dimensional finite element model
Authors: Bates Paul D. , Anderson Malcolm G. , Baird Laura , Walling Des E. , Simm David
Published: February 2007

A prototype two‐dimensional finite element flow model for depth‐averaged free surface flows was developed for floodplain environments. Limited refinement of the model's physical representation was undertaken and the enhanced scheme applied to an 11 km river channel/floodplain reach in the U.K. Preliminary model results indicate that this modelling approach can be used to identify dynamic variations in the flow field parameters over length scales of the order of 10‐100 m. Potentially, such data have the ability to permit detailed analysis of short‐term floodplain sedimentary dynamics.
Distribution and formation of rock varnish in southern Tunisia
Authors: Drake N. A. , Heydeman M. T. , White K. H.
Published: February 2007

Field observations, chemical analysis, electron and light microscopy and radiolabelling experiments provide information on the characteristics, formation and distribution of Fe and Mn rock varnishes in southern Tunisia. Unstable rocks are not surface‐coated, but when broken they commonly reveal internal microbial solution fronts. Stable rocks are coated in Fe, and more rarely Mn, rock varnishes. Radiolabelling indicates the presence of many respiring microbes on both Fe and Mn varnishes. Microscopy shows fungi and bacteria, both on the Fe varnishes and within the rock. Only rare, microcolonial fungi occur on Mn varnishes, suggesting that the microbes are within or beneath the varnish. The abundance of microorganisms supports a biogenic origin for rock varnishes. Different microbial communities appear to be involved in Fe and Mn varnish formation. Microbes appear to live beneath the surface of unstable rocks but coat stable rocks which cannot be penetrated, apparently to avoid u.v. light and desiccation. This explains the concentration of elements that form u.v. opaque minerals and clays. The origin of these elements is external to the substrate. These results suggest that rock varnish dating and paleoenvironmental techniques can be applied in southern Tunisia.
Numerical simulation of vertical marsh growth and adjustment to accelerated sea‐level rise, North Norfolk, U.K.
Authors: French Jonathan R.
Published: February 2007

In parts of North America and Europe, present and future sedimentary deficits translate into major areal losses of coastal salt marsh. Physically based simulations of medium‐ to long‐term adjustment to accelerated sea‐level rise are few, partly due to the difficulty in extrapolating imperfectly understood sedimentation parameters. This paper outlines the implementation and application of a simple one‐dimensional mass balance model designed to simulate the vertical adjustment of predominantly minerogenic marsh surfaces to various combinations of sediment supply, tidal levels and regional subsidence. Two aspects of marsh growth are examined, with reference to sites on the macro‐tidal north Norfolk coast, U.K.: (i) historical marsh growth under a scenario of effective (long‐term) eustatic stability but slow regional subsidence; and (ii) marsh response to various non‐linear eustatic rise scenarios for the next century. In contrast to more organogenic North American marshes, sedimentation rates in Norfolk are strongly time‐dependent. Where the overall sediment budget is so closely linked to marsh age and relative elevation, some form of numerical simulation offers a preferred means of predicting the impact of accelerated sea‐level rise. Simulations performed here show that only the most dramatic eustatic scenarios result in ecological ‘drowning’ and reversion to tidal flat within the conventional 2100 prediction interval. Currently favoured scenarios give rise to accretionary deficits which are clearly sustainable in the short‐term, albeit at the expense of increased inundation frequency and consequent changes in the distribution of marsh flora and fauna.
Interactions between perched and saprolite aquifers on a small, salt‐affected and deeply weathered hillslope
Authors: George Richard J. , Conacher Arthur J.
Published: February 2007

A small hillslope was chosen to investigate the role of throughflow as a mechanism responsible for the movement of soil water and solutes towards a saline seep and as a source of recharge to a permanent, regional aquifer at depth. The hydraulic properties, chemical characteristics and physical responses of both systems were studied on a deeply weathered, salt‐affected hillslope. Additional data were also obtained from other sites in south‐western Australia.

Regional groundwater flow occurred in a variably textured, deeply weathered material in which the hydraulic conductivity varied from < 0·001 to 0·14m day−1. Perched groundwater flow (throughflow) occurred in the higher permeability (˜ 1·5 m day−1), near‐surface soil materials. Throughflow occurred throughout winter, contributing approximately 530 m3 of fresh (˜ 160 mg l−1 Cl) water to a saline seep. By contrast, the deep aquifer discharged approximately 1100 m3 of waters with salt concentrations of 2000–6000 mg l−1 Cl. Recharge and discharge rates to and from the deep aquifer, were estimated to be of the order of 5–20 mm a−1 and 50–300 mm a−1 respectively.

Saturated conditions existed throughout winter within the seep and the immediately adjacent non‐saline area, with up to 60 per cent of the hillslope soils becoming saturated after major rainfall events ( > 20 mm day−1). In the mid‐slopes, in particular along a central depression, saturation of the shallow soils caused macropore channel recharge to take place through the clay‐textured subsoils. Water‐level responses suggest that approximately 25–30 per cent of annual recharge occurred from one storm studied in September 1984. Recharge through macropore channels is a significant mechanism in the concave slope areas on the hillslope. Throughflow was found to be a major source of water, but not salt, contributing to the saline seep. In general, the contribution of throughflow was found to decrease further inland at other sites studied. However, at inland sites where perennial, perched aquifers have developed in deep sands, saline areas have been caused by throughflow and not by deep aquifer discharge.
Reply. Denudational isostatic rebound of intraplate highlands: The Lachlan river valley, Australia
Authors: Bishop Paul , Brown Roderick
Published: February 2007

Two main points are raised in replying to Fabel et al. (1993) in their discussion of the paper by Bishop and Brown (1992). It is argued that local variations in denudation are insufficient to invalidate the key conclusions, especially as the amount of sediment deposited in the Murray Basin is a key (and known) measure of the amount of denudation. The total evidence for rebound is now known to be regional in extent, supporting the relevance of a regional isostatic model. We note that isostatic rebound need not to be continuous, so that evidence of episodic rebound does not conflict with it, and that a lack of isostatic rebound would require a strongly opposing active tectonic regime. That is, a key general conclusion is that denudational rebound should always be assessed as an explanation for uplift before active tectonism is invoked.
Till fabric associated with deformable beds
Authors: Hart Jane K.
Published: February 2007

This 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

The 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

Blowing 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

The 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

The 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

Two 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

The 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

A 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

Part 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

The 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

The 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

A 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

Genome‐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

Asthma 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

The 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

The 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.
Additions to the non‐marine fauna of the lower coal measures of the North‐Midlands Coalfields
Authors: Eagar R. M. C.
Published: February 2007

The main elements of the non‐marine fauna are reviewed in stratigraphical order in the light of recent revisional work on the Anthracosiidae. Attention is directed towards non‐marine facies and to the lesser known faunas from the upper half of the Lower Coal Measures, from which Carbonicola extenuata and C. proxima spp. nov. are described. Evidence is adduced to suggest that the boundary between the lenisulcata and communis Zones, defined by Wray and Trueman (1934) at the top of the Elland Flags in Yorkshire, should be lowered to the horizon of the Upper Band Coal—Pasture Mine.

Detailed work on the Bassy Mine succession (Eagar 1952a) has been extended southward to Huyton, near St. Helens, Pott Shrigley in Cheshire, and to Goyt's Moss in Derbyshire. A summary of results of a special study of shells from about the horizon of the Lower Foot Mine at Goyt's Moss reveals evidence bearing on shell shape and ecological station which is generally in conformity with results from other horizons elsewhere (Eagar 1953b).

One new marine or estuarine phase (15 feet above the Six Inch Mine near Bacup) and 11 non‐marine horizons, or records of them, have been found or re‐discovered in Lancashire. New localities and two new non‐marine horizons have been found in Yorkshire. Descriptions of faunas include those of Carbonicola sp. nov. cf. bipennis (Brown), from the horizon of the Lower Foot Mine, assemblages of C. artifex Eagar and variants, and Carbonicola torus Eagar. The species Anthraconaia (?) prisca (Trueman) is now referred to the genus Carbonicola. Anthraconaia sp. nov. has been discovered on a horizon probably below the Upper Band Coal in a boring at Laisterdyke near Bradford. Another new Anthraconaia has been found with Carbonicola torus, C. aff. bipennis and shells resembling Anthracosia from the Modiolaris Zone, near the top of the Elland Flags at Kirkheaton, Huddersfield. Anthraconaia cf. modiolaris (J. de C. Sowerby) has been found in a similar fauna in the basal communis Zone, 60 feet below the Arley Mine at Bolton, Lancashire.
Abnormalities of growth in specimens of gastrioceras from the lower coal measures
Authors: Magraw D.
Published: February 2007

Certain abnormalities of growth have recently been seen in specimens of the genus Gastrioceras. These take the form of a distinct groove occurring on the venter, and photographs of three specimens showing the salient features of these grooves are reproduced. Details of the abnormalities are given and their significance discussed.