bluuebunny/crossref_metadata_2025 huggingface dataset:
Tectonic causes of landslides
Authors: Alexander David , Formichi Renzo
Published: February 2007

The relationship between mass movements and tectonic lineaments is investigated in the Pliocene sand and clay terrains of Montepulciano (central Italy). Satellite images and aerial photographs show six families of lineament in southern Tuscany, all of which are present in the Montepulciano area. The orientation, location and density of these are related to corresponding attributes of morphological phenomena such as retrogressive slumps, drainage density and slope angle. Rose diagrams, stereographic plots and statistical analysis all reveal a close correspondence between slumping mass movements and the directions and spatial concentrations of fracture traces. Although slopes and valley trends respond more closely to Apennine (NW‐trending) and anti‐Apennine (NE‐trending) lineaments, the longitudinal axes of landslides are strongly orientated NNW to N, the direction of one of the most significant lineament groups in western central Italy and the local study area.
A note on the role of the lichen collema auriforma in solution basin development on a carboniferous limestone substrate
Authors: Moses C. A. , Smith B. J.
Published: February 2007

A study carried out on Carboniferous limestone in the north and west of Ireland supports the idea that rock substrate is removed by the direct mechanical action of lichens. An experiment in which the lichen Collema auriforma was subjected to a number of wetting‐drying cycles, showed, using scanning electron microscopy, that contraction of the lichen thallus during the drying phase plucked rock fragments from the substrate surface. This process could contribute to the formation of karstic features including solution basins.
Role of porolithon algal‐ridge growth in the development of the windward coast of Tongatapu Island, Tonga, South Pacific
Authors: Nunn Patrick D.
Published: February 2007

A description of the algal ridge fringing the windward coasts of the island of Tongatapu is given. Three coastal types can be distinguished according to the height of the algal ridge. Type A coasts have a low algal ridge and low wave energy. Surge channels are few and uncovered. Blowholes are poorly developed. The reef flat is wide and has numerous living corals. Many beaches occur except around promontories where a cliff‐foot notch is actively forming. Type B coasts have a medium‐height algal ridge and experience moderate wave energy. Surge channels are longer, more frequently covered and blowholes consequently better developed. The reef flat/shore platform has less coral living on its surface. Large beaches along type B coasts are the outcome of sediment becoming trapped on the shoreward side of the algal ridge following storms. Type C coasts have a high algal ridge and are characterized by a high‐energy regime. Surge channels are almost all covered, giving rise to spectacular blowholes, except where collapse has caused the algal ridge to assume a buttressed rather than linear form. The shore‐platform surface is devoid of living coral and lies above high‐tide level. The cliff‐foot notch is shielded by the algal ridge from direct wave attack. A notch is forming on the upper part of the outer slope of the shore platform: such notches were observed only along type C coasts.

A model for Holocene coastline development is outlined. The reef established on the mid‐Holocene shore platform emerged abruptly by ˜ 2 m as the result of coseismic uplift around 4000 years ago. Sea level fell (around 3000 years ago): erosion concentrated on reducing emerged shore‐platform level. Sea level stabilized around 1000 years ago: the emerged shore platform continued to be lowered; around 600 years ago, algal‐ridge growth commenced thereon. Rates of vertical growth ranged from 0·5 to 2·1 mm a−1. The process regime along type C coasts changed around 362 years ago when the algal ridge reached a sufficient height to shield the shoreline from the processes which had fashioned it and a lower‐level notch began to be cut on the reef slope.
Quantitative sediment source ascription using magnetic measurements in a reservoir‐catchment system near Nijar, S.E. Spain
Authors: Yu Lizhong , Oldfield Frank
Published: February 2007

The magnetic properties of sediments from a dried‐out reservoir and its inflowing streams were measured to provide a basis for sediment source determination. Quantitative estimates of source component proportions in the reservoir sediments were made using linear programming procedures. The study confirms that this type of research must be based on a detailed knowledge of the relationship between magnetic properties and particle size in both the sediments and the potential sources. In the case of the site studied, the Isabel II reservoir, near Nijar, S.E. Spain, the sediments generated by contemporary surface processes within the reservoir catchment fail to reflect fully the 19th century material largely responsible for the rapid infill of the reservoir. An additional source type, namely unweathered schist‐derived material not represented in the fine sediments sampled within channels upstream from the reservoir, has to be included in the model before calculations of source component contributions can be made. It is inferred that one or more high magnitude, low frequency event outside the amplitude of the most recently operating processes was largely responsible for the infilling of the reservoir.
Effects on bedload transport of experimental removal of woody debris from a forest gravel‐bed stream
Authors: Smith R. D. , Sidle R. C. , Porter P. E.
Published: February 2007

Experimental removal of woody debris from a small, gravel‐bed stream in a forested area resulted in a four‐fold increase in bedload transport at bankfull discharge. This was caused by increased transportability of sediment previously stored upslope of debris buttresses or in low‐energy hydraulic environments related to debris. Bank erosion delivered additional sediment to the channel, and transport energy was increased by an inferred increase in the component of total boundary shear stress affecting grains on the bed. Increased transport following debris removal in May 1987 continued throughout the entire autumn storm season through late November 1987, indicating persistent adjustment of the stream bed and banks despite marked response to earlier flows as large as bankfull. Stream bed adjustments included development of a semi‐regular sequence of alternate bars and pools, many of which were spaced independently of former pool locations.
Soil hydrophobicity effects on rainsplash: Simulated rainfall and photographic evidence
Authors: Terry James P. , Shakesby Richard A.
Published: February 2007

Laboratory rainfall simulation experiments indicate greater splash losses for hydrophobic (water repellent) than for wettable sandy loam soils at different rainfall intensities, durations and soil surface inclinations. Using synchronized video cameras with different shutter speeds and stroboscopically illuminated 35 mm still photography, differences in splash droplets and ejection trajectory characteristics are examined. For hydrophobic soil, raindrop impact gives rise to fewer, larger, slower‐moving daughter ejection droplets which carry more sediment and hence follow shorter range trajectories compared with wettable soil. Implications for erosion of hydrophobic soils are discussed.
Modelling late‐holocene snow‐avalanche activity: Incorporating a new approach to lichenometry
Authors: McCarroll Danny
Published: February 2007

Where snow avalanches descend steeply into large rivers, displacing bedload, avalanche boulder‐ramparts may accumulate, retaining a record of late‐Holocene snow‐avalanche frequency. The age frequency of surface boulders on 12 such features in upper Jostedalen, southern Norway, was investigated using the size‐frequency distribution of lichens. A model was constructed to simulate the influence of variations in avalanche frequency sinceAD1325 on lichen‐size‐frequency distributions.

Using this modelling approach it is not possible to define a unique pattern of avalanche activity to account for the observed lichen‐size‐frequency distributions, but it is possible to place strict limits on the range of scenarios that are acceptable. The results suggest that maximum avalanche activity occurred during the 19th century, after the peak of the Little Ice Age. This conflicts with historical records of avalanche damage to property at lower altitude in nearby valleys, which may reflect avalanche activity only during a short period of extreme climatic conditions. Close agreement between the records of snow avalanches and debris flows suggests that both reflect periods of high winter snowfall and rapid spring melting rather than low temperature. Future ‘greenhouse warming’ may therefore result in increased avalanche activity in southern Norway.
River response to channel regulation: Case study of the Raba river, Carpathians, Poland
Authors: Wyzga Bartłomiej
Published: February 2007

Processes induced by the channelization of the Raba River in the present century are examined to illustrate the response of a gravel‐bed stream following narrowing and straightening of its channel. Up to 3 m of incision has occurred. The change from a slow and relatively steady degradation in the lower reaches to separate degradation events in the higher reaches is attributed to the differential rate of headcut retreat and to the control exerted by mid‐channel bars upon the rate of river‐energy dissipation. Progressive outwashing of finer grains from bed material has followed the diminishing sediment yield of the basin and the increase in stream power. The ensuing growth in mean grain size and changes in sediment fabric have increased boundary resistance to flow and reduced particle susceptibility to entrainment. Downstream magnification of peak discharges has become increasingly pronounced with the advancing incision. The decrease in flood‐plain storage and self‐acceleration of flows passing the relatively deep and straight channel has caused flood waves to become progressively more flashy in nature.

An increase in channel depth and reduction in gradient caused by downward and backward erosion, as well as bed material coarsening has promoted the re‐establishment of an equilibrium. Conversely, flow velocity increases due to flow concentration in the deepened channel. Reduction in grain mobility allows the river to attain a new equilibrium at flow‐velocity and stream‐power levels higher than before the channelization.

Numerous disadvantages of the applied regulation scheme and its failure to reduce flood hazard raise the question of its maintenance. To be successful, any regulation design must take into account changes in sediment supply and flood hydrographs resulting from the simultaneous alterations in basin management.
Geometry, bed topography and drainage system structure of the haut glacier d'Arolla, Switzerland
Authors: Sharp Martin , Richards Keith , Willis Ian , Arnold Neil , Nienow Peter , Lawson Wendy , Tison Jean‐Louis
Published: February 2007

As part of an integrated study of the hydrology, meltwater quality and dynamics of the Haut Glacier d'Arolla, Switzerland, the glacier's drainage network structure was determined from patterns of dye recovery in 342 injection experiments conducted from 47 moulins distributed widely across the glacier. This structure was compared with theoretical predictions based upon reconstructed patterns of water flow governed by (a) the subglacial hydraulic potential surface, and (b) the subglacial bedrock surface. These reconstructions were based on measurements of ice surface and bedrock topography obtained by a combination of ground survey and radio‐echo sounding techniques. The two reconstructions simulate the drainage system structures expected for (a) closed channels, in which water is pressurized by the overlying ice, and (b) gravity‐driven, open‐channel flow. The closed‐channel model provides the best fit to the observed structure, even though theoretical calculations suggest that, under summer discharge conditions, open‐channel flow may be widespread beneath the glacier. Possible reasons for this apparent discrepancy are discussed.
The role of wind direction in eolian transport on a narrow sandy beach
Authors: Nordstrom Karl F. , Jackson Nancy L.
Published: February 2007

Comparison of eolian transport during five high‐velocity wind events over a 29 day period on a narrow estuarine beach in Delaware Bay, New Jersey, USA, reveals the temporal variability of transport, due to changes in direction of wind approach. Mean wind speed measured 6 m above the dune crest for the five events ranged from 8·5 to 15·9 ms−1. Mean wind direction was oblique to the shoreline (63° from shore‐normal) during one event but was within 14° of shore‐normal during the other events.

Eolian transport is greatest during low tide and rising tide, when the beach source area is widest and when drying of surface sediments occurs. The quantity of sediment caught in a vertical trap for the five events varied from a total of 0·07 to 113·73 kgm−1. Differences in temperature, relative humidity and moisture and salt content of surficial sediments were slight. Mean grain sizes ranged from 0·33 to 0·58 mm, causing slight differences in threshold shear velocity, but shear velocities exceeded the threshold required for transport during all events.

Beach width, measured normal to the shoreline, varied from 15·5 to 18·0 m; beach slope differed by 0·5°. The oblique wind during one event created a source width nearly double the width during other days. Beach slope, measured in the direction of the wind, was less than half as steep as the slope measured normal to the shoreline. The amount of sand trapped during the oblique wind was over 20 times greater than any other event, even those with higher shear velocities. The ability of the beach surface to supply grains to the air stream is limited on narrow beaches, but increased source width, due to oblique wind approach, can partially overcome limitations of surface conditions on the beach.
Meanders caused by hyperconcentrated water flow: An example from the loess plateau, China
Authors: Jiongxin Xu
Published: February 2007

This paper describes meandering alluvial rivers with mean annual suspended‐sediment concentrations of more than 100 kgm−3 on the Loess Plateau, China, and explains their formation as caused by the effect of hyperconcentrated water flow. When the river is dominated by hyperconcentrated flow, the rate of energy expenditure required for sediment transport declines significantly. Accordingly, the river channel adjusts itself to a lower channel gradient by increasing the river length, resulting in a meandering channel. Since the stable transportation of sediment by hyperconcentrated flow is dependent on river channel boundary conditions, the latter play an important role in the formation of meanders of this kind. The paper also discusses the conditions for the discrimination of meandering and braided rivers in this area.
The significance of rainstorm variations to shallow translational hillslope failure
Authors: Brooks S. M. , Richards K. S.
Published: February 2007

Landsliding in eastern Scotland results from high‐magnitude rainstorms generated under either cyclonic or anticyclonic conditions, particularly during the summer. Data from Aviemore indicated that cyclonic storms produce higher rainfall totals than anticyclonic storms, as well as being of longer duration and lower intensity. The distribution of rain during individual storms also varies with the synoptic conditions under which the storms are produced. These different rainfall characteristics produce different geomorphic responses, which can be investigated in detail using physical based modelling. In this paper, a physically based coupled hydrology–stability model is used to assess the significance of these rainfall characteristics to soil moisture response and slope instability for mature podsols. The results provide evidence that rainstorms of different synoptic origin produce varying hydrological response, involving both the extent and the timing of moisture content change. This affects the depth and timing of slope failure, with anticyclonic storms promoting a large, rapid response in the factor of safety at shallow depths within the soil. Cyclonic storms produce a more gradual response, with the region of probable failure being deeper. Futhermore, each of these storm types is associated with different rainfall distributions, and this is also shown to have a significant effect on the timing and depth of slope instability.
On being a ‘real’ geomorphologist
Authors: Rhoads Bruce L.
Published: February 2007

In a recent editorial Richards (1990) advocated a realist perspective for geomorphology. Scientific realism, defined broadly, is the doctrine that science attempts to generate true knowledge of the observable and unobservable (i.e. non‐empirical) aspects of an objective world. Various brands of realism exist; the particular version cited by Richards (1990) has not strongly influenced mainstream philosophy of science. Also, critical rationalism, which Richards (1990) contrasts with realism, fully adopts a realist perspective. In its broadest sense, realism encompasses the entire spectrum of geomorpho‐logic research, thus providing a unifying philosophical framework for geomorphology.
Channel and floodplain response to recent abrupt climate change: The tyne basin, Northern England
Authors: Rumsby Barbara T. , Macklin Mark G.
Published: February 2007

This paper examines the timing, nature and magnitude of river response in upland, piedmont and lowland reaches of the Tyne basin, northern England, to high‐frequency (20–30 year) changes in climate and flood regime since 1700 AD. Over this period fluvial activity has been characterized by alternating phases of river‐bed incision and stability coinciding with non‐random, decadal‐scale fluctuations in flood frequency and hydroclimate that appear to be linked to changes in large‐scale upper atmospheric circulation patterns. Episodes of widespread channel bed incision (1760–1799, 1875–1894, 1955–1969) result from a higher frequency of large floods (> 20 year return period) and cool, wet climate under meridional circulation regimes. Phases of more moderate floods (5–20 year return period), corresponding to zonal circulation types (1820–1874, 1920–1954), are characterized by enhanced lateral reworking and sediment transfer in upper reaches of the catchment, and channel narrowing and infilling downstream. Rates of fluvial activity are reduced in intermediate periods (1800–1819, 1895–1919) with no dominant circulation regime associated with lower flood frequency and magnitude. The results of this study provide a valuable guide for forecasting probable drainage basin and channel response to future climate change.
Criteria for recognition of constructional silicic lava flow surfaces
Authors: Anderson Steven W. , Krinsley David H. , Fink Jonathan H.
Published: February 2007

Surface‐exposure dating (SED) methods typically rely on the measurement of a geochemical parameter that systematically changes with time. A pivotal task in the calibration of many of these techniques is to demonstrate that lava flow surfaces sampled for dating have not experienced erosion. Although criteria for identification of constructional basaltic lava flow surfaces have been published, no such criteria presently exist for the recognition of constructional silicic flows. Here we present several criteria for identifying constructional silicic lava flow features in the field. First, crease structures are fractures with easily identified, curved, striated walls that are commonly observed on recent and active silicic lava flows. Crease structures form during extrusion, and are resistant to mechanical disintegration because they expose dense material from the flow interior. Second, some crease structures break apart during formation, leaving a deposit of striated blocks on the flow surface. Crease structure blocks are striated on only one side, whereas blocks from internal columnar joints exposed through erosion are striated on two or more sides. Only the striated side of the crease structure block is definitively constructional. Finally, many silicic flow surfaces exhibit expanded or breadcrusted textures. These features consist of a dense, fractured rind, 1 –2cm thick, enclosing highly vesicular material. Breadcrust flow textures appear similar to breadcrust bombs produced during volcanic explosions, so it is imperative to demonstrate that they are part of the lava flow surface. These criteria should enable investigators to positively identify constructional silicic lava flow surfaces when calibrating an SED method.
Subglacial observations from øksfjordjøkelen, North Norway
Authors: Rea Brice R. , Brian Whalley W.
Published: February 2007

Stepped bedrock topography at the snout of a small outlet glacier from Øksfjordjøkelen, North Norway, produces an extensive subglacial cavity system which stretches some 70m across and 100m up‐glacier, giving access beneath ice ≤50 m thick. Inside the cavity, regelation ice, clean glacier ice and deforming basal ice have been observed. Samples were taken and basal debris concentrations at the glacier sole were found to vary between 0.005 and 15.38 per cent by volume. The basal ice velocity has been determined using a linear variable differential transformer attached to an analogue recorder, and also by means of measured displacements of ice crews and clasts embedded in the basal ice. Velocities were found to differ both spatially and temporally from a maximum of 2.55 mm h1 to a minimum of 0.3 mm h−1. The measurements and observations, which have been related to present theory, show how spatially averaged values for a number of variables could lead to inaccuracies in predicted erosion values, certainly at a local scale. On the exposed foreland, jointcontrolled lee‐side faces provide evidence for extensive subglacial plucking (here taken to mean the removal of preloosened bed material and/or material resulting from bed failure). Indeed, in the cavity the early stages of removal of joint‐controlled blocks by ice deformation along joints have been observed. The importance of debris‐rich basal ice is shown in the formation of large striations (up to 500cm × 16cm × 2cm) present on the foreland.
Importance of environment on the order of mineral weathering in olivine basalts, Hawaii
Authors: Wasklewicz Thad A.
Published: February 2007

Examination of weathering rinds from lava flows on Hawaii with backscatter electron microscopy and electron micro‐probe analysis reveals that olivine weathers more slowly than adjacent clinopyroxene and plagioclase in environments with a paucity of organic acids. Yet when weathering rinds are in contact with abundant organic acids secreted by lichens, olivine weathers before clinopyroxene and plagioclase weathers last. The exception to Goldich's widely accepted mineral stability series in organic‐poor environments runs counter to a thermodynamics explanation for the order of mineral weathering and illustrates the importance of the biogeochemical environment.
Effects of atmospheric conditions on wind profiles and aeolian sand transport with an example from white sands national monument
Authors: Frank Andrew , Kocurek Gary
Published: February 2007

Quantifying aeolian sand transport rates relies upon the computation of the near‐surface shear velocity (u*) determined from velocity profiles of the wind. While it has been recognized that various conditions, such as saltation, surface roughness, surface slope and atmospheric conditions, have an effect on the velocity profile, it is commonly assumed that measurements made above the surface will be representative of the near‐surface shear velocity. Airflow and temperature data collected over a flat substrate at White Sands National Monument in New Mexico, however, show the significant effects that atmospheric conditions have on velocity profiles. During the day, when solar insolation is heating the surface, atmospheric conditions in the lowest several metres become unstable, resulting in enhanced convection and vertical mixing so that the velocity gradient changes little with height. As a result, the shear stress in this region of vertical mixing lessens, while the near‐surface shear stress is increased because the higher wind speeds are now nearer the surface. At night, the near‐surface atmospheric conditions are stable, thereby reducing convection and vertical mixing, resulting in stratified airflow and increased shear velocity away from the surface. Unless this atmospheric effect is accounted for, estimates of sediment transport rates may be in error by as much as a factor of 15 times when wind speeds are near threshold velocity. At wind speeds approaching 10 ms1, at 5m above the surface, this error in computing sediment transport is reduced to a factor of only two to three times, and may be within the range of measurement error.
Response of tide‐dominated mangrove shorelines in Northern Australia to anticipated sea‐level rise
Authors: Woodroffe C. D.
Published: February 2007

The exact response of mangrove shorelines to anticipated sea‐level rise will depend upon the balance between sedimentation and sea‐level change. Within the Top End of the Northern Territory of Australia there are extensive, relatively unmodified, tide‐dominated mangrove forests, where tidal processes redistribute sediment. Harbours, such as Darwin Harbour, and tidal rivers, such as the South Alligator River with its associated coastal and estuarine plains, represent opposite extremes in terms of Holocene sedimentary infill, and will respond differently to sea‐level rise. In Darwin Harbour, mangrove assemblages can be recognized in geomorphologically defined habitats. Similar topography within and between creeks implies morphodynamic equilibrium with tidal processes. Tidal reworking of sediment may maintain an equilibrial profile under gradually rising sea level, with resuspension of lower intertidal and subtidal muds and their redeposition within upper intertidal mangrove habitats. In contrast, the plains along the coast and tidal rivers draining into van Diemen Gulf developed during the post‐glacial marine transgression, and since sea level stabilized, around 6000 years ago, coastal plains have prograded. These broad plains are presently not extensively influenced by salt water, but are often at elevations close to, or even below, modern high‐tide levels. They may, therefore, revert to saline conditions particularly rapidly if the sea rises. The pattern of change may not be directly analogous to marine incursion experienced in the early Holocene, because broad plains have been able to prograde during the last 6000 years of relatively stable sea level.
Rapid entrenchment of stream profiles in the salt caves of Mount Sedom, Israel
Authors: Frumkin Amos , Ford Derek C.
Published: February 2007

Rock salt is approximately 1000 times more soluble than limestone and thus displays high rates of geomorphic evolution. Cave stream channel profiles and downcutting rates were studied in the Mount Sedom salt diapir, Dead Sea rift valley, Israel. Although the area is very arid (mean annual rainfall ≈ 50 mm), the diapir contains extensive karst systems of Holocene age.

In the standard cave profile a vertical shaft at the upstream end diverts water from a surface channel in anhydrite or clastic cap rocks into the subsurface route in the salt. Mass balance calculations in a sample cave passage yielded downcutting rates of 0–2 mm s−1 during peak flood conditions, or about eight orders of magnitude higher than reported rates in any limestone cave streams. However, in the arid climate of Mount Sedom floods have a low recurrence interval with the consequence that long‐term mean downcutting rates are lower: an average rate of 8·8 mm a−1 was measured for the period 1986–1991 in the same sample passage. Quite independently, long‐term mean rates of 6·2mm a−1 are deduced from 14C ages of driftwood found in upper levels of 12 cave passages. These are at least three orders of magnitude higher than rates established for limestone caves.

Salt cave passages develop in two main stages: (1) an early stage characterized by high downcutting rates into the rock salt bed, and steep passage gradients; (2) a mature stage characterized by lower downcutting rates, with establishment of a subhorizontal stream bed armoured with alluvial detritus. In this mature stage downcutting rates are controlled by the uplift rate of the Mount Sedom diapir and changes of the level of the Dead Sea. Passages may also aggrade. These fast‐developing salt stream channels may serve as full‐scale models for slower developing systems such as limestone canyons.
Geomorphic evolution of the Southern Alps, New Zealand
Authors: Tippett J. Mark , Kamp Peter J. J.
Published: February 2007

The Southern Alps are the topographic expression of late Cenozoic (<8 Ma ago) uplift of the crust of the leading edge of the Pacific plate in South Island, New Zealand. New fission track data on the basement exposed in the Southern Alps quantify the age, amount, and rate of rock uplift, and in combination with geomorphic parameters permit the construction of a new model of the geomorphic evolution of the Southern Alps. The model emphasizes the development over time and space of rock uplift, mean surface elevation, exhumation of crustal section, and relief. The earliest indications of mean surface uplift are between 4 and 5 Ma ago at the Alpine Fault. Mean surface uplift, which lagged the start of rock uplift, propagated southeastward from the Alpine Fault at a rate of 30 km/Ma. By about 4 Ma ago, exhumation had exposed greywacke basement adjacent to and east of the entire 300 km long central section of the Alpine Fault. At 3 Ma ago, greenschist was exposed in the southern parts of the Southern Alps near Lake Wanaka, and since then has become exhumed along a narrow strip east of the Alpine Fault. The model infers that amphibolite grade schist has been exhumed adjacent to the Alpine Fault only in the last 0·3 Ma. The age of the start of rock uplift and the amount and rate of rock uplift, all of which vary spatially, are considered to be the dominant influences on the development of the landscape in the Southern Alps.

The Southern Alps have been studied in terms of domains of different rock uplift rate. At present the rate of rock uplift varies from up to 8–10 mm/a adjacent to the Alpine Fault to 0·8–1·0 mm/a along the southeastern margin of the Southern Alps. This spectrum can be divided into two domains, one northwest of the Main Divide where the present rock uplift rates are very high (up to 8–10 mm/a) and exceed the long‐term value of 0·8–1·0 mm/a, and another to the southeast of the Main Divide where the long‐term rate is 0·8–1·0 mm/a. A domain of no uplift lies immediately to the east of the Southern Alps, and is separated from them by a 1·0–1·5 km step in the basement topography. We argue that this spatial sequence of uplift rate domains represents a temporal one.

The existing models of the geomorphic development of the Southern Alps—the dynamic cuesta model of J. Adams and the numerical model of P. Koons—are compared with the new data and evolutionary model. Particular constraints unrealized by these two earlier models include the following: the earlier timing of the start of rock uplift of the Southern Alps (8 Ma ago); the spatial variation in the timing of the start of rock uplift (8 Ma ago to 3 Ma ago); the lower long‐term rock uplift rate (0·8–1·0 mm/a) of the Southern Alps for most of the late Cenozoic; the lag between the start of rock uplift and the start of mean surface uplift; and the patterns of the amounts of late Cenozoic rock uplift and erosion across the Southern Alps.
Use of magnetic and radiometric measurements to investigate erosion and sedimentation in a British upland catchment
Authors: Hutchinson Simon M.
Published: February 2007

In response to the potential shortcomings of single‐technique strategies in the investigation of erosion and sedimentation, a combined magnetic and radiometric (13Cs and 210Pb) approach has been undertaken in the upland, watershed‐lake system of Howden Reservoir, Derbyshire. By combining these techniques, some assessment of sediment sources and the erosion status of the catchment has been achieved. Alone, each approach would have been unable to determine unequivocally sediment provenance. Furthermore, the parallel use of these measurements has highlighted limitations and/or uncertainties in both the magnetic and 137Cs techniques. These problems reflect the particular soil characteristics and drainage conditions of this upland catchment. Despite the documented severity of peat erosion in the region, Howden Reservoir has a mixture of sediment sources and a relatively moderate rate of sedimentation. Sediment yields (total 127·7 t km−2 yr−1 including organic fraction 31·3 t km−2 yr−1) are, however, higher than in other British upland areas.
Air flow over foredunes and implications for sand transport
Authors: Arens S. M. , Van Kaam‐Peters H. M. E. , Van Boxel J. H.
Published: February 2007

More than 4000 hourly wind profiles measured on three topographically different foredunes are analysed and discussed. Wind flow over the foredunes is studied by means of the relative wind speed: the ratio between wind speed at a certain location and the reference wind speed at the same height. Relative wind speeds appear to be independent of general wind speed but dependent on wind direction. For perpendicular onshore winds the flow over the foredune is accelerated due to topographic changes and decelerated due to changes in surface roughness. Accelerations dominate over decelerations on the seaward slope. The pattern of acceleration and deceleration in relation to wind direction is more or less comparable for different foredunes, but the magnitudes differ. An increase in foredune height from 6 to 10m leads to an increase in speed‐up near the top of the seaward slope from 110 to 150 per cent during onshore wind, but further increase of foredune height from 10 to 23m appears to have little effect, due to increased roughness and deflection of flow.

Topography also influences the direction of the flow. Between beach and top, the flow deflects in the direction of the normal during onshore winds. During offshore winds the flow is deflected to the parallel. Near the dunefoot, deflection is always in the direction of the parallel, and increases with steeper topography. The maximum deflection near the dunefoot was 90°, over a 23 m high dune, observed during offshore winds.

Patterns of erosion and sedimentation resulting from winds from different directions can be explained by the observed accelerations and decelerations. Owing to speed‐up on the seaward front of the foredune, sand transport capacity of the wind increases, which results in erosion if vegetation is absent. During strong onshore wind, sand is lifted near the dunefoot and moves over the foredune in suspension. During weaker winds, vertical wind velocities do not exceed fall velocities of the sand grains, and most of the sand is deposited near the dunefoot.
Floodplain sedimentation: Quantities, patterns and processes
Authors: Asselman Nathalie E. M. , Middelkoop Hans
Published: February 2007

This paper presents the result of measurements of floodplain sedimentation using sediment traps. The study was carried out on two embanked floodplains along the Rivers Rhine and Meuse in The Netherlands during a 3 day flood in January 1993. Raster maps of sediment accumulation were made by interpolating the measurements from the traps using block kriging. The sediment maps show clear patterns in sediment accumulation, together with the estimated interpolation errors. Average sediment accumulation ranges between 0·57 and 1·0 kg m−2. High sediment accumulation is found on the levees (4 kg m−2 or more) and on low lying areas (1·6 kg m−2); sediment accumulation decreases with distance from the main channel. The sedimentation patterns are related to floodplain topography and sediment transporting mechanisms. Sediment transport by turbulent diffusion as well as by convection can be recognized. Also, flood duration and the process of sediment settling out in ponding water in closed depressions are important. The applied method allows comparison of the results with raster‐based sedimentation models.
Adjustment and recovery of unstable alluvial channels: Identification and approaches for engineering management
Authors: Simon Andrew
Published: February 2007

The management of riverine environments is shown to require a knowledge and awareness of the complex interactions between fluvial and mass‐wasting processes, riparian vegetation, and channel form. Identification of the cause of instability rather than the local symptoms, and knowledge of the temporal and spatial aspects of channel adjustment are central to the application of (1) appropriate analyses to estimate future channel changes, (2) appropriate mitigation measures, and (3) the protection of river‐crossing structures and adjacent land. Conceptual models of channel evolution and bank‐slope development are particularly valuable for interpreting past and present processes, applying appropriate computational techniques to estimate future channel changes, and implementing strategies to mitigate the impacts of processes likely to dominate the channel in the future.

Techniques for identification and analysis of channel instability are interdisciplinary and provide a mechanism for estimating changes in channel‐bed elevation and channel width with time. Features of channel form and associated riparian vegetation can be used as diagnostic criteria to identify channel processes, the stage of channel evolution and the magnitude and extent of instability. Changes in bed elevation with time can be represented using an exponential function; changes in channel width with time can be calculated using slope stability equations and (or) projection of a temporary angle of stability from a low‐angle surface termed the ‘slough line’ that supports re‐establishment of woody vegetation. These techniques, in combination with knowledge of the state of channel evolution, can then be used to assess the appropriateness of various mitigation measures to control on‐going channel adjustments and to protect river‐crossing structures.
Concentrated flow erosion in cultivated catchments: Influence of soil surface state
Authors: Auzet A. Véronique , Boiffin Jean , Ludwig Bruno
Published: February 2007

Concentrated flow erosion is the dominant form of winter erosion in northern France. This study correlates the ephemeral rill and gully volumes measured in 20 cultivated catchments (4–95 ha) for three consecutive winters with the size of the potential runoff‐contributing areas. These areas were identified by characterizing soil surface state through crust development stage, importance of surface wheel tracks and roughness grade. A single and significant relationship was found between the size of runoff‐contributing areas, estimated by this criterion, and the rill and gully volumes. This identified the proportion of the catchment area occupied by fields with a degraded surface structure as the main factor controlling the variability of erosion in a context of concentrated flow erosion on cultivated land. The extension of degraded areas was shown to be controlled by dynamic interactions between weather, land occupation and soil physical properties. This criterion accounts for the uneven distribution of rainfall in space and time. Morphological factors, such as talweg length and slope, are believed to determine part of the residual variability.
Variation with respect to petrological differences in a thin band of upper carboniferous non‐marine lamellibranchs
Authors: Eagar R. M. C.
Published: February 2007

The development of an impersistent band of non‐marine shells immediately underlying the Gastrioceras subcrenatum marine band and referred to Carbonicola ? lenisulcata (Trueman) and C. ? aff. bellula (Bolton) is traced over much of the area of outcrop of the Lower Coal Measures in Yorkshire and Lancashire. The fauna of an underlying local leaf in the Sheffield area is referred to Carbonicola aff. protea Wright. The shells of both faunas show allometric growth with respect to their height and length.

Differences in the petrology of the main non‐marine shell band in five localities have been investigated optically by Professor K. C. Dunham and Mr. T. Deans, and by chemical analysis. What appear to be regional changes in the nature and range of variation of the shells reveal a correlation with petrological change closely comparable with that found in passage upward through the lower parts of cyclic units of sedimentation in the Soft Bed — Bassy Mine succession (Eagar 1947). Changes in the variation of the faunas, when they are traced horizontally on this single horizon, are however, of considerable smaller magnitude than those of the latter. Thus a fauna of dominantly anthraconaioid elongate shells, occurring in fine‐grained richly carbonaceous shale, shows greater variation and an increasing proportion of relatively short Carbonicolae? as it is followed into shaly mudstone with larger detrital constituents and less carbonaceous matter. The relative proportions of carbonaceous matter, varying inversely with thickness of the band and amount of shells per unit thickness, suggest that sedimentation caused reduction in size in two localities. The significance of the clay‐mineral content and of pyrite, which is unusually abundant and present with framboidal texture in the band, is brieflly discussed. It is suggested that the water was brackish during the formation of the band and that possibly unusually saline or near‐marine conditions may have obtained.
Hebridean notes: Rhum and Skye
Authors: Bailey E. B.
Published: February 2007

I. Black's dating of the Tertiary lavas of Rhum as later than the Tertiary granophyre is accepted, as also his tracing of a fault along the contact of granophyre and Torridonian. This fault is interpreted as part of the Rhum ring‐fault, and a local transition between granophyre and Torridonian arkose is discussed.

II. King's discovery of dissimilar contacts on the two sides of a Tertiary basalt dyke cutting Tertiary granophyre in Skye is explained on a mobilisation hypothesis.
Diagenetic fabrics in some British Dinantian limestones
Authors: Bathurst R. G. C.
Published: February 2007

Diagenetic fabrics (textures and structures) have been examined in thin sections of Dinantian limestones mainly from the Avon Gorge, North Wales and Yorkshire. Six processes are shown to have been responsible for the change from unconsolidated sediment to limestone. These are: (1) granular cementation and drusy growth, (2) rim cementation (secondary enlargement), (3) pressure solution, (4) grain growth sensu stricto, (5) mechanical deposition in cavities of post‐depositional age, and (6) post‐depositional formation of cavities by erosion and solution in a carbonate mud.

Grain growth, a process well known to metallurgists, acts in monomineralic fabrics of low porosity in the solid state. The intergranular boundaries wander so that some grains enlarge while others shrink and disappear, so bringing about a general increase in coarseness.

In all the limestones the mosaic between the mechanically deposited particles (skeletal debris, pellets, ooliths) is one of three types. These are granular cement, rim‐cemented detrital crystals, and a mosaic caused by grain growth.
The stratification of the Great Scar Limestone in the Settle district of Yorkshire
Authors: Schwarzacher W.
Published: February 2007

The Great Scar Limestone in the Settle district and near the Stainmore syncline has been studied in eight representative sections. The sequence of D1 age in this area is divided by pronounced master bedding planes into nine lithological cycles, which can be traced from section to section.

Fossils are concentrated near the master bedding planes and indications of increased current activity are recorded. The regularity with which the master bedding planes occur suggests a climatic rather than tectonic control of the cycles.
The lower Ludlow Grits in Wales
Authors: Cummins W. A.
Published: February 2007

Developments of arenaceous beds in different parts of North and Central Wales are shown to be contemporaneous and are grouped together as the Lower Ludlow Grits. Directions of transport based mainly on flute cast measurements are recorded. It is shown that the Welsh Basin was divided into two distinct troughs. In the northern, Denbigh Trough, greywackes were deposited by currents flowing from west to east. In the southern, Montgomery Trough, no greywackes are found, but calcareous siltstones were deposited by currents flowing from south to north. Turbidity current flow was along the lengths of the troughs. Contemporaneous slumping was down the sides of the troughs.
Some aspects of radiogeology
Authors: Davidson C. F.
Published: February 2007

Within recent years studies of the natural distribution pattern of the radioactive elements have been developed as a prerequisite to explorations for the raw materials of atomic energy. One important result of this activity is an improvement of our geochronological knowledge of the stratigraphical succession. Memorable bench‐marks are Lower Cambrian at 600 million years, Upper Carboniferous at 300 m.y., Middle Cretaceous at 100 m.y. So‐called Proterozoic rocks may locally be more than 2,000 m.y. old (Witwatersrand System) and may pre‐date several orogenies in so‐called Archaean rocks elsewhere. Some ore deposits provide factual evidence for theories of reworking: for example, ores apparently of late Mesozoic age can derive from Hercynian granites. Radiogeological studies now play an important part in prospecting for ore deposits and for coal and oil fields, and they can be of much significance in evaluating the health hazards arising from artificial radioactivity.
Geophysical investigations of the sea floor
Authors: Mason R. G.
Published: February 2007

Seismic refraction measurements show that the earth's crust thins from about 35 km. under the continents to 6 km. under the oceans, also that the oceanic crust has a layered structure. The sediments that cover it are much thinner than expected, which suggests that the oceans are perhaps younger than was thought, or perhaps the sediments have become engulfed in lavas. Great fracture zones cross the floor of the north‐east Pacific and there is evidence for strike‐slip movements of more than 200 km. along them. The discovery that heat flow rates for continents and oceans are approximately equal upsets previous ideas about radioactive heat sources. A pattern has been observed in the heat flow associated with an oceanic rise. It has been suggested that both are related to convection in the mantle. Subcrustal drag by convection currents may explain the fracture zones.
The history of Chirotherium
Authors: Swinton W. E.
Published: February 2007

Cheirotherium was the name given to a hand‐like imprint believed in 1835 to be a mammal. Similar footprints have long been found in Cheshire and much work was done by J. Lomas and H. C. Beasley upon them. The genus is now known to occur in America as well as in Europe and 34 species have been described. The history of discovery, the validity of species, and the classification are discussed here. The animal that made the prints is identified as a pseudosuchian reptile.