bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recurrent landslides events on the submarine flank of Piton de la Fournaise volcano (Reunion Island)
Authors: Labazuy Philippe 
Published: April 2008

Abstract
New studies confirm the existence of large landslide events related to both the Piton des Neiges and the Piton de la Fournaise volcanic systems. Like many other island basaltic shield volcanoes, Réunion Island has had a complex evolution combining construction processes and recurrent destructive events. Landslide deposits probably form an important part of its internal structure. Sliding events and related tsunamis are one of the major hazards of this kind of volcanic activity, in an intraplate oceanic context.

The submarine flank of Piton de la Fournaise has been extensively studied using Seabeam bathymetry and high resolution side-scan sonar images. The eastern submarine flank is entirely covered by 550 km
3
of landslide deposits, which are mainly subaerially erupted basaltic lavas, transported and fractured in large-scale mass wasting. Volumetric considerations imply recurrent partial destruction of the edifice, by landsliding, during its construction. For each sector collapse the fundamental process is the sliding of large blocks, up to several kilometres in length. Fractions of the slide blocks break up and evolve into debris avalanches.

Analogue experiments have been carried out to tentatively explain the geometry of these periodic large landslides of the unbuttressed flank. The morphology and the deformation in the landslides of the model are compared to the natural system of Piton de la Fournaise.
Effects of botanical composition, soil origin and composition on mineral concentrations in dry season pastures in western Kenya
Authors: Jumba I. O. , Suttle N. F. , Hunter E. A. , Wandiga S. O. 
Published: April 2008

Abstract
The influence of botanical (pasture species), geographical (altitude) and pedological (bedrock type, soil pH and extractable mineral concentration) factors on mineral concentrations in dry season pasture was studied in samples of topsoil and herbage from 135 sites on 84 farms in the Mt Elgon region of western Kenya. Of the four major elements measured in herbage, only S was affected by geology, low values being found above Tertiary volcanic (TV) and metamorphic gneiss (MG) bedrocks. By contrast, only P was not affected by species, Setaria being low and Kikuyu grass usually high in macro minerals. Of the seven trace elements analysed in herbage, geology influenced only one: Cu; low values were again found above TV and MG but Cu availability to grazing ruminants would be relatively high because of the associated low S values. By contrast, only Se was unaffected by species, Kikuyu grass being high in all but Mn. Soil bedrock had a greater influence on soil composition but correlations between extractable soil and herbage mineral concentrations were poor for all elements, even within botanical species after correction for soil pH and soil contamination. Concentrations of Ca, P, Mg, S, Cu and Zu were often less than tabulated requirements for grazing livestock. However, risks of deficiency could not be predicted from the pedological factors measured.
The distribution of trace and major elements in Kenyan soil profiles and implications for wildlife nutrition
Authors: Maskall John , Thornton Iain 
Published: April 2008

Abstract

Concentrations of trace and major elements are examined in several soil profiles from national parks and wildlife reserves in Kenya. Broad variations in soil trace element concentrations between locations are largely attributable to differences in parent material and variations in soil pH are related to sodium and calcium concentrations. However, element concentrations and distributions are also influenced by soil forming processes. The process of sodication in alkaline solonetz soils in Lake Nakuru National Park appears to have lowered the concentrations of copper, cobalt and nickel in the surface horizon. At Amboseli National Park, a marked accumulation of molybdenum, sodium, potassium, calcium and magnesium in the surface horizon of an alkaline solonchak is probably due to salinization processes. Apparent mobilization of copper, cobalt and nickel down the profile of a humic nitisol in the Aberdares Salient is associated with eluviation and leaching processes. In two andosols and an ando-humic nitisol, copper, cobalt and nickel tend to accumulate in the surface horizon in association with organic matter. In vertisols from Amboseli National Park and Lewa Downs Wildlife Reserve, the relatively constant trace element concentrations in the A and B horizons are linked to the self-swallowing processes that characterize this soil type. The elevated pH in the solonetz and solonchak soils at Lake Nakuru and Amboseli National Parks results in enhanced uptake of molybdenum in the grass species
Sporobulus spicatus
. At Lake Nakuru National Park, high molybdenum concentrations in this and other plant species are associated with low copper status of impala. The implications of soil geochemistry for the trace element nutrition of wild animals in small conservation areas are discussed.
Biogeochemistry and metal biology
Authors: Selinus O. , Frank A. , Galgan V. 
Published: April 2008

Abstract

Environmental monitoring of metals on two trophic levels is presented: a biogeochemical technique developed at the Geological Survey of Sweden, using aquatic mosses and roots of aquatic plants, and a bioanalytical-chemical technique developed at the National Veterinary Institute based on organ tissues from the moose (
Alces alces
L.), a wild ruminant living in the Swedish forests.

The usefulness of the techniques is exemplified by monitoring of Cd in southern Sweden. The results of both monitoring systems are in close agreement. Together with analysis of crops and drinking water the results indicate a region with elevated Cd burden. Also the changing environment is monitored by the moose. Decreasing concentrations of essential and toxic metals (cations) and increasing molybdenum concentration (anion) were found in a strongly acidified region of Sweden by comparison with a reference material from 1982. pH increase of the environment of the moose is indicated, probably by liming. It resulted in severe copper and chromium deficiency of the moose and was suggested as the cause of a ‘mysterious’ disease in the moose.
Comparison of the techniques confirms the advantage of using metal-monitoring maps in interpreting biological data and also the predictive value of the monitoring maps in biological contexts.
Biogeochemical factors affecting groundwater quality in central Tanzania
Authors: Bowell R. J. , McEldowney S. , Warren A. , Mathew B. , Bwankuzo M. 
Published: April 2008

Abstract

Analysis of groundwaters from the Makutuapora aquifer in the Dodoma region of central Tanzania has revealed a relationship between mineral-water interactions, water chemistry, bedrock geology, and microbiology. Groundwaters were slightly alkaline (pH 6–7.8) and essentially Na-Ca-HCO
3
-Cl, with minor K, Mg, F, and SO
2−
4
. Variations in water chemistry, particularly Ca/Na and Mg/Ca, ratios are related to the progressive alteration of feldspars and ferromagnesium minerals. The constant Na/Ca and Mg/Ca ratios noticed over mature aquifers and wells indicates that a steady-state is attained between aluminosilicates and groundwater. While erratic Fe/Mg and Na/K ratios denote a more open system or rather a greater diversity in minerals hosting these elements participating in mineral-water reactions. In places total concentrations of Fe, Mn, and Al can each exceed 1 mg l
−1
with most of the metal held in particulate form (> 0.45 μm). The increase in metals suggests an imbalance in the steady-state reactions between magmatic minerals and leachate, possibly related to microbial activity. Fifty percent of the groundwaters were contaminated by significant numbers of thermotolerant coliforms indicating considerable risk of contamination by faecal pathogens. Numbers of faecal coliforms were positively correlated with K, Na, NO
3
−
, PO
4
3−
and BOD. Groundwater chemistry also affected the activity of the indigenous microbial community. Microbial biomass appeared to be unaffected by differences in groundwater chemistry. The numbers of selected physiological bacterial types (e.g. organisms contributing to the nitrogen and sulphur cycles) and the range of protist morphotypes, isolated from the tropical groundwater systems, were broadly similar to those found in temperate groundwater. Total concentration of metals such as Al, Fe, Co and Mn certainly exceed levels at which these metals could be considered toxic although if these metals are present in non-labile forms (as suggested by other studies) then the potential toxicity would be negligible. At present the major concerns for health are high seasonal salinities in the groundwaters and high faecal contamination.
Kriging: a method of estimation for environmental and rare disease data
Authors: Oliver M. A. 
Published: April 2008

Abstract
Most properties that are distributed in geographical space vary, and often in a complex way. The information available is usually fragmentary, but we often want to know the values at intermediate locations. This is the case for both environmental and disease data. However, the nature of the data and the information that we require from them ultimately can be quite different. For rare disease knowing its spatial distribution is often not enough, we also want to know the variation in the underlying risk. At present direct links between disease and factors in the environment are tenuous; however, there is increasing interest in obtaining more precise evidence. Geostatistics provides us with a means of analysing both kinds of data underpinned by the same body of theory, the Theory of Regionalized Variables. Two types of geostatistical estimation are described here. Disjunctive kriging for estimating the probabilities of exceeding particular threshold values in the environment: it is illustrated with an example of soil salinity in Israel. Standard geostatistical technique has been adapted to analyse the spatial distribution of a rare disease, and to estimate the risk of developing it: this is illustrated with an analysis of childhood cancer in the West Midlands Health Authority Region where the risk appears largest in rural areas. The aim in the future is to use the information from both approaches to identify areas for further investigation concerning the aetiology of certain diseases.
Origins and palaeoceangraphic significance of laminated daitom ooze from the Eastern Equatorial Pacific Ocean
Authors: Kemp Alan E. S. , Baldauf Jack G. , Pearce Richard B. 
Published: April 2008

Abstract

Laminated diatom ooze (LDO) has been recovered from several ODP Leg 138 sites and now is also recognized from several DSDP Leg 85 sites. These remarkable sediments are the result of massive and episodic flux of mats of the diatom
Thalassiothrix longissima
. By analogy with the
Rhizosolenia
diatom mat-forming events monitored by JGOFS (Joint Global Ocean Flux Study) in the equatorial Pacific Ocean during cooling conditions in late 1992, these episodes of massive flux of
T. Iongissima
mats may represent the ‘fall out’ from major frontal systems generated during La Niña (anti-El Niño) events. Laminations were preserved in the mat deposits because of the rapid mat deposition and high strength of the diatom mat meshwork, that subjugated benthic activity. This new mechanism of preservation of lamination in marine sediments has wide implications for other laminated sequences. The sustained periods of mat deposition documented in Neogene sediments of the eastern equatorial Pacific Ocean are part of the major cycles in the relative abundance of carbonate and silica in the region and, possibly, in the case of some intervals, also in the Atlantic Ocean.
Magmatic segmentation of mid-ocean ridges: a review
Authors: Batiza Rodey 
Published: April 2008

AbstractTectonic and magmatic segmentation of ridges occurs at several scales that overlap or form a continuum. A good working hypothesis is that segmentation is hierarchical and that magmatic and tectonic segmentation are linked and related by mantle flow and upwelling patterns. The largest scale of magmatic segmentation is isotopic, reflecting differences in mantle history and composition spanning a range of scales as large as individual ocean basins or larger. Superimposed, is the most conspicuous scale of segmentation, defined by large transforms and/or non-transform offsets. Magmatically, this scale of segmentation seems to reflect differences in the melting process together with the effects of smaller scale mantle heterogeneity. There appear to be differences between slow- and fast-spreading magmatic segments, although other factors such as magma supply, plume influence and ridge obliquity may also have important effects. Recurring patterns at individual segments, at least partly independent of spreading rate, include: constancy v. variability in inferred melting parameters, regular v. irregular spatial distribution of enriched basalts, MgO values, and other parameters, and correlation vs. no correlation of chemistry with axial depth.The smallest scales of magmatic segmentation require the most closely spaced and detailed sampling. Since there have been relatively few studies of this type, there are many questions remaining. It is likely that this scale of segmentation is controlled by deep crustal and shallow upper mantle processes. However, the superimposed effects of mantle heterogeneity and time-dependent processes such as volcanic-magmatic cycles complicate the picture.
Restricted melting under the very slow-spreading Southwest Indian ridge
Authors: Robinson C. J. , White R. S. , Bickle M. J. , Minshull T. A. 
Published: April 2008

Abstract

The major element chemistry of basaltic glass from two localities on the Southwest Indian Ridge is consistent with the occurrence of reduced melting under this very slow spreading ridge compared with that under ‘normal’ oceanic spreading centres. This agrees with theoretical models for mantle melting which include the influence of conductive heat loss from the mantle as it wells up beneath very slowly separating plates. There are distinct chemical differences between the two areas of study. Basaltic samples from the segment at 57°E have consistently lower Na
2
O, Al
2
O
3
and SiO
2
and higher FeO, CaO/Al
2
O
3
, K
2
O and TiO
2
than those from 66°E. The 57°E lavas have an MgO range of 5.9–7.5 wt% and define approximately linear oxide trends versus MgO, while the 66°E lavas have too small a range of MgO values (6.8–7.8 wt%) to define any trends. The chemical data can be interpreted in terms of different extents of melting at different mean pressures.
Characterization and interpretation of
P-T
paths with multiple thermal peaks
Authors: Whitney Donna L. , Dilek Yildirim 
Published: April 2008

Abstract

Using pressure-temperature (
P-T
) paths to decipher sequences of tectonic events in the evolution of contractional orogens is difficult because in most metamorphic terrains only a limited part of the path can be inferred from petrologic evidence. Perturbations such as thermal pulses may not be recorded if they occurred over very short geological time scales. Deviations from standard
P-T
path shapes (e.g. pressure and temperature increase followed by decompression and cooling) are seldom recognized although they may reflect major crustal processes that affect the thermal structure of continents during active tectonism. In particular, recognition of complex
P-T
trajectories with multiple thermal peaks is essential for understanding tectonic, metamorphic and magmatic processes that occur during unroofing of metamorphic terrains. Using the example of the Niğde metamorphic core complex (Turkey) and other similar terrains, we propose that
P-T
paths with initial Barrovian trajectories followed by one or more low-pressure-high-temperature thermal spikes (increase in temperature at nearly constant pressure) may be characteristic of metamorphic core complexes. These temperature spikes are commonly associated with granitic magmatism that results when metasedimentary rocks are buried and heated during regional metamorphism. Additional thermal contributions such as enhanced mantle heat flow or mafic magmatism are not required to explain the thermal spikes.
On the occurrence and characterization of ultrahigh-temperature crustal metamorphism
Authors: Harley Simon L. 
Published: April 2008

AbstractUltrahigh-temperature (UHT) crustal metamorphism is a division of medium-pressure granulite facies metamorphism where peak temperatures of 900–1100°C have been attained at pressures in the range 7–13 kbar. The key indicators of UHT conditions are mineral assemblages involving combinations of sapphirine, garnet, aluminous orthopyroxene, cordierite, sillimanite, spinel and quartz in pelites and quartzites. Experimentally constrained and calculated FMAS and KFMASH petrogenetic grids involving these phases and additional osumilite and melt indicate that sapphirine + quartz is stable only at >1040°C in reduced rocks, that osumilite is restricted to >900°C for pressures greater than 6 kbar and has an ultimate stability limit of 9 kbar in FMAS, and that the orthopyroxene + sillimanite + quartz assemblage is restricted to pressures greater than 8 kbar in KFMASH. These criteria, coupled with the grids isoplethed for the Mg/(Mg + Fe) of garnet and Al-content of orthopyroxene allow the peak pressure-temperature (P-T) conditions of several UHT occurrences to be defined and the post-peakP-Tpaths delineated.UHT conditions are seldom determined from slowly cooled granulites using conventional geothermometry principally because of the propensity of Fe-Mg exchange thermometry to only record closure temperatures of 700–850°C. However, pressure-convergence calculations for several granulites with UHT mineral assemblages yield back-calculated mineral compositions that are consistent with temperatures of 950–1000°C prior to post-peak Fe-Mg re-equilibration. The best compositional indicator of UHT conditions remains the preservation of high Al2O3contents (8–12 wt%) in orthopyroxene coexisting with garnet, sillimanite or sapphirine.TheP-Tconditions and records preserved in the currently documented UHT localities and terranes are varied. Both types of post-peakP-Tpath isobaric cooling and isothermal decompression (ITD) are recorded from reaction textures in different UHT terranes, and several preserve very similar ITD histories that may reflect the final stage of collisional orogenesis. Although counter-clockwise and clockwiseP-Tpaths have been proposed on the basis of textural observation for some terranes, the progradeP-Thistories of most UHT areas are not known. Such information, and further experimental constraints on quartz-absent assemblages at UHT conditions, are of prime importance to interpret further this extreme form of crustal metamorphism.
Making movies: phase diagrams changing in pressure, temperature, composition and time
Authors: Worley Brenton , Powell Roger 
Published: April 2008

Abstract

Quantitative phase diagrams, and in particular phase diagram movies, offer a powerful and versatile forward approach to modelling the
P-T-x-t
relationships of natural mineral assemblages. Phase diagram movies are ideal for illustrating the continuous way in which mineral compositions and assemblages evolve with changing
P-T-x
conditions. A feature of the animation process, is that it also enables an extra variable to be represented by the running time of the movie. A methodology for producing quantitative phase diagram movies is illustrated using the example of the AFM compatibility diagram. This approach involves the calculation of phase equilibria at critical values of the animating variable (in this case temperature), with interpolation of the data between these values. Phase equilibria calculations were performed using Thermocalc v2.5, and data interpolation and construction of the individual phase diagrams (or movie frames) was achieved in
Mathematica
® v2.2.2 using purpose-written code. Although the details of the technique, and the code, have been designed for use with this particular application, the approach is quite general.
Tephra dispersal
Authors: Bursik M. 
Published: April 2008

Abstract
Our understanding of the spread of volcanic ejecta from eruption columns has evolved significantly since the first quantitative studies. Given recent advances, it is possible to describe much of the physics of tephra dispersal, and to construct a relatively robust model for the spread of tephra in the proximal region of a volcanic eruption plume. Results from such modelling compare well with data on tephra fall deposits. More distal dispersal, driven as it is by atmospheric motions, has also been treated extensively, by atmospheric scientists as well as by volcanologists. Results from these studies have been compared with satellite data and have been found to be accurate in terms of predicting ash cloud trajectories. Comparisons of the various models with data point out several areas where research could be productively directed in future. The transition from tephra transport by the plume to that by the atmosphere is poorly understood: processes related to transport between plume and ground are poorly known: the layering of the stratosphere needs to be considered more thoroughly to understand transport processes over periods of days to months; and the total grain size distributions of fall deposits and eruption plumes have probably been incompletely characterized in the past.
Geochemical trends in Early Tertiary palaeosols from northeast Ireland: a statistical approach to assess element behaviour during weathering
Authors: McAlister John J. , Smith Bernard J. 
Published: April 2008

Abstract
Geochemical and statistical analyses (principle components and Cluster analysis) are used to study changes in element concentration in a range of chemically complex palaeosols from northeast Ireland produced under humid tropical conditions. Chemical analyses characterize the samples and statistical techniques show trends in elemental concentration due to chemical weathering processes. Simple ratios allow the concentration of each element to be examined in individual samples and a ternary diagram classifies these palaeosols with respect to their degree of lateritization. Results demonstrate the general value of statistical analyses in grouping chemically complex palaeosols in terms of element enrichment and depletion as a result of chemical weathering. This approach is independent of any preferred mechanism in the process of rock weathering. It also points out that the theoretical behaviour of elements does not follow those determined by statistical analysis. This technique could also be applied to the classification of present-day lateritic soils.
Environmental interpretation and evolution of the Tertiary erosion surfaces in the Iberian Range (Spain)
Authors: Gutiérrez-Elorza M. , Gracia F. J. 
Published: April 2008

Abstract
The geomorphological analysis of regional Neogene erosion surfaces is of great geological interest as it helps in the reconstruction of the environmental evolution of continental areas. Moreover, the structural analysis of their deformation is a good approach to the identification of the main neotectonic trends at a regional scale. The Iberian Range is an excellent example of the application of this kind of study. It shows four stepped Neogene erosion surfaces, well preserved in general and whose ages range from the middle Miocene to the Villafranchian. Their formation is related to planation processes in semi-arid conditions. The stepping of surfaces is related to distensive Neogene tectonic pulses of sufficient magnitude for the planation processes to be interrupted.