bluuebunny/crossref_metadata_2025_split huggingface dataset:
Groundwater exploration in rural Scotland using geophysical techniques
Authors: Macdonald A. M. , Ball D. F. , McCann D. M. 
Published: April 2008

Abstract
Identifying the location, size, and characteristics of small aquifers is becoming increasingly important in Scotland with the growing demand for groundwater to supply isolated rural communities. These small, localized aquifers are found within superficial deposits, such as alluvium, blown sands and raised beach deposits, and in fracture zones in the underlying bedrock. Geophysical techniques offer a rapid and inexpensive method of characterizing these aquifers. Electromagnetic techniques using EM34 and EM31 instruments have proved useful in identifying variations in the thickness of superficial deposits and detecting buried channels, for example, at Palnure, SW Scotland. Ground penetrating radar has been used at several locations, including the island of Coll, to detect the boundary between bedrock and alluvium or blown sand. More detailed techniques, such as resistivity soundings, seismic refraction and resistivity tomography have been used to identify fractures in basement rocks and help calibrate the other methods, for example at Foyers, near Loch Ness. Magnetic profiling has also been used to locate dykes (acting as hydraulic barriers) within Permian aquifers in the west of Scotland.
Role of geographical information systems and groundwater modelling in water resource management for small islands: a case study from St Martin’s and St Agnes, Isles of Scilly, UK
Authors: Watkins David C. 
Published: April 2008

Abstract
Common to other small islands, water resource management is a critical issue on the Isles of Scilly, UK. This study examined the current practice of water management on the islands of St Martin’s and St Agnes in the Isles of Scilly so that a local water management plan could be formulated. The study commenced with a survey of water supplies which included locating wells, rainwater tanks and septic tanks and determining their connections and utility. Wellheads were level surveyed with respect to UK Ordnance Datum, allowing reduced groundwater levels to be monitored. Groundwater is abstracted from shallow dug wells in blown sand or Head deposits and deep wells bored into fractured granite. Hydraulic tests were conducted in seven wells to determine well and aquifer characteristics, although these tests were limited by the low yields of the wells. A geographical information system was used to collate and process information. MODFLOW and MODPATH models were constructed to help interpret the hydrogeology; to determine the impact and sustainability of groundwater abstractions; and to determine the possible extent of source protection zones around wells. The present rate of abstraction is sustainable but, due to large natural variations in the water table level, groundwater resources will always be vulnerable during periods of dry weather. The main threats to existing groundwater supplies are saline intrusion, elevated nutrient levels from agriculture and bacterial contamination from septic tanks.
North Atlantic climate variability in early Palaeogene time: a climate modelling sensitivity study
Authors: Sloan Lisa Cirbus , Huber Matthew 
Published: April 2008

Abstract

Understanding the nature and causes of the variability associated with past warm, high
p
CO
2
climates presents a significant challenge to palaeoclimate research. In this paper we investigate the early Eocene climatic response in the North Atlantic region to forcing from an indirect effect of atmospheric methane (via polar stratospheric clouds (PSCs)), and we investigate the response of the climate system to forcing from a combination of orbital insolation changes and high atmospheric
p
CO
2
concentration. We find that sea surface temperatures (SSTs), sea ice extent, net surface moisture, continental runoff and upwelling in the North Atlantic Ocean are all sensitive to those forcing factors, and that the degree of sensitivity is a function of location and season. Our results suggest that high-latitude SST values can vary by as much as 20 °C during the winter season in response to precessional and polar cloud forcing, whereas in contrast summer temperature varies by 4 °C or less. Model predictions of net surface moisture balance also vary substantially with our prescribed forcing. There is a large difference in variability between the localized net surface moisture results and the mean North Atlantic Ocean results, which suggests that large-scale assumptions about past surface ocean salinities and seawater δ
18
O may need to be reassessed. According to model results, the influx of terrigenous material via continental runoff to the North Atlantic Ocean should be highly seasonal, with greatest runoff occurring in spring. Our model results also indicate that changes in wind-driven upwelling and in continental runoff on a precessional time scale should be seen in regions of the central North Atlantic.
The role of deep basement during continent-continent collision: a review
Authors: Ryan Paul D. 
Published: April 2008

Abstract
Structural, geophysical and metamorphic studies show that collisional orogeny thickens the crust by a factor of two or more. A large volume of continental material at the base of the orogen is, therefore, subject to eclogite facies conditions. Phase equilibration results in a loss of buoyancy and thermodynamic heating of this crustal root. This dense crustal material may be partially subducted, as in the Alps or the Himalayas, and lost to the system. Alternatively, it may rest isostatically below the Moho until it is partially exhumed during orogenic collapse, as in the Scandinavian Caledonides or the Tonbai-Dabie Mountains. Remnant orogenic roots may exist as seismically reflective mantle and provide a locus for subsequent Wilson Cycle rifting. The rate at which these phase transformations take place may have a profound buffering effect on the amount and duration of orogenic contraction. Isostatically compensated transient 2-dimensional finite element thermal models are presented, which seek to place some limits on these processes. It is interesting to speculate whether more is learnt about the process of orogeny from a single exhumed eclogitic boudin or from mapping nappe complexes.
Thermal-rheological controls on deformation within oceanic transforms
Authors: Furlong Kevin P. , Sheaffer Steven D. , Malservisi Rocco 
Published: April 2008

AbstractTransform faults that offset mid-ocean ridge (MOR) segments accommodate plate motion through deformations that involve complex thermal and mechanical feedbacks involving both brittle and temperature-dependent ductile rheologies. Through the implementation of a 3D coupled thermal-mechanical modelling approach, we have developed a more detailed picture of the geometry of plate boundary deformation and its dependence on plate velocity and the age offset of MOR transforms. The modelling results show that cooling of near-ridge lithosphere (lateral heat transfer) has significant effects in the ductile mantle lithosphere for both the location and style of deformation. The region where strain is accommodated in the subjacent mantle lithosphere is systematically offset from the position of the overlying linear transform fault in the brittle crust. This offset causes the boundary to be oblique to plate motions along much of the transform’s length, producing extension in regions of significant obliquity modifying the location of the surface fault segments. An implication of this complex plate-boundary geometry is that in the near-ridge region, the older (cooler) lithosphere will extend beneath the ridge tip, restricting the upwelling of mantle to the MOR. The melt to generate the oceanic crust adjacent to the transform must migrate laterally from its offset source, resulting in a reduced volume and thinner crust. This near-ridge plate boundary structure also matches the pattern of core-complex extension observed at inside corners of many slow-spreading ridges. The oblique extensional structure may also explain magmatism that is observed along ‘leaky’ transforms, which could ultimately result in the generation of new ridge segments that effectively ‘split’ large transforms.
Clay mineral transformations and weakening mechanisms along the Alpine Fault, New Zealand
Authors: Warr Laurence N. , Cox Simon 
Published: April 2008

Abstract

The formation of clay minerals within active fault zones, which results from the infiltration of aqueous fluids, often leads to important changes in mechanical behaviour. These hydrous phyllosilicates can (1) enhance anisotropy and reduce shear strength, (2) modify porosity and permeability, (3) store or release significant volumes of water, and (4) increase fluid pressures during shearing. The varying interplay between faulting, fluid migration, and hydrous clay mineral transformations along the central Alpine Fault of New Zealand is suggested to constitute an important weakening mechanism within the upper section of this crustal discontinuity. Well-developed zones of cataclasite and compacted clay gouge show successive stages of hydrothermal alteration, driven by the cyclic, coseismic influx of meteoric fluids into exhumed amphibolite-facies rocks that are relatively Mg rich. Three modes of deformation and alteration are recognized within the mylonite-derived clay gouge, which occurred during various stages of the fault’s exhumation history. Following initial strain-hardening and frictional melting during anhydrous cataclastic breakdown of the mylonite fabric, reaction weakening began with formation of Mg-chlorite at sub-greenschist conditions (<320 °C) and continued at lower temperatures (<120 °C) by growth of swelling clays in the matrix. The low permeability and low strength of clay-rich shears are suitable for generating high pore-fluid pressures during faulting. Despite the apparent weakening of the
c.
6 km upper segment of the Alpine Fault, the upper crust beneath the Southern Alps is known to be actively releasing elastic strain, with small (<M 5) earthquakes occurring to 12 km depth. We predict that larger events will nucleate at
c.
6–12 km along an anhydrous, strain-hardened portion of the fault.
Petrology and geochemistry of exhumed peridotites and gabbros at non-volcanic margins: ODP Leg 173 West Iberia ocena-continent transition zone
Authors: Hébert Réjean , Gueddari K. , LaFlèche M.R. , Beslier M.-O. , Gardien V. 
Published: April 2008

Abstract

Ultramafic and mafic rocks recovered at Holes 1068A and 1070A were drilled during Leg 173 of the Ocean Drilling Program (ODP) in the ocean-continent transition zone of the Iberia Abyssal Plain. Peridotites show contrasting petrographic characteristics. Hole 1068A peridotites are fine grained and show a well-defined high-temperature foliation marked by elongated pyroxene as well as aligned spinels. Hole 1068A peridotites are strongly serpentinized. Hole 1070A peridotites are coarse grained and show little evidence of high-temperature foliation. The degree of serpentinization is lower and relicts of silicate minerals are preserved. In both sets of recovered material, spinels show a wide range of composition and suggest a complex magmatic evolution. Gabbros dykes, which are found only in Hole 1070A, are very coarse grained and are locally sheared and/or crushed. Magmatic amphiboles are kaersutites and Ti-rich tschermakites that are partially replaced by hornblende and actinolite, and are associated with plagioclase of intermediate composition. Peridotites and pyroxenite have low TiO
2
, Al
2
O
3
and CaO contents in carbonate-free samples. Ni and Cr contents fall into the upper-mantle array. On the other hand, gabbros have relatively high TiO
2
and V contents reflecting modal ilmenite, and suggesting that they are relatively differentiated. This paper presents the very first geochemical data on platinum group elements (PGE) of peridotites and gabbros from passive margins. Peridotites and gabbros show low PGE (25.83 ppb and 1.44 ppb), Pd (2.75 ppb and 0.15 ppb), Pd/Ir ratios (1.45 and 1.3) and mafic index. Pyroxenite has the highest PGE (27.97 ppb), Pd/Ir (19.87) and Pt/Ir (10.25). Interelemental correlation and observation of PGE-bearing sulphide phases suggest that the PGE are hosted by single sulphide phases. From a PGE point of view, extraction of magmas involved very PGE-depleted liquids similar to gabbroic veins cutting the peridotites at Hole 1070A. Partial melting is interpreted as occurring just before oceanic accretion. Geochemical attributes suggest that the peridotites belong to the Ronda and Beni Bousera peridotitic depleted end-member clan. Thus they are believed to be of subcontinental origin. Deformation and retrograde metamorphism of peridotites and gabbros are consistent with exhumation in a rift environment post-dating the 120 Ma magmatic stage.
Palaeomagnetic and rock magnetic results from serpentinized peridotites beneath the Iberia Abyssal Plain
Authors: Zhao Xixi 
Published: April 2008

AbstractA palaeomagnetic and rock magnetic study has been performed on serpentinized peridotite rocks recovered at Ocean Drilling Program (ODP) Leg 149 and 173 sites, off the west coast of Portugal (Sites 897, 899 and 1070). Stable components of magnetization are revealed after detailed thermal and alternating field demagnetization. Results from a series of rock magnetic measurements with advanced instrumentation all corroborate the demagnetization behaviour and show that (titano)magnetites and maghemite are present in the peridotites. At Leg 149 and 173 sites, the inclinations of characteristic magnetization in the ‘fresher’ lower part of the serpentinized peridotite section show a predominantly reversed polarity in a depth zone ofc.25 m, which is compatible with a reversed event (probably correlated with marine Anomaly M0 atc.121 Ma) before the Cretaceous Long Normal Superchron (83–120 Ma) and is incompatible with a Holocene field direction. In contrast, the inclinations of samples from the more ‘altered’ upper part are predominantly normal. In view of the polarity of magnetization identified from the overlying Cretaceous and Tertiary sediments and the newest interpretation of the drilling results for the Iberia margin, our results suggest that the Iberian peridotites were emplaced during Aptian-Barremian time and recorded the middle Cretaceous geomagnetic field during Anomaly M0 time (c.121 Ma). Our data are consistent with new radiometric dates for the Iberian peridotites at Leg 173 drill sites.
Palaeowaters in European coastal aquifers — the goals and main conclusions of the PALAEAUX project
Authors: Edmunds W. M. 
Published: April 2008

Abstract
The PALAEAUX project has brought together up-to-date geochemical, isotopic and hydrogeological information on coastal groundwaters across Europe in a transect from the Baltic to the Canary Islands. These data have been interpreted in relation to past climatic and environmental conditions, as well as extending and challenging concepts about the evolution of groundwater near the present day coastlines. Groundwater movement beyond the present coastline as well as emplacement on shore to greater depths (up to 500 m) than allowed by the present-day flow regime has occurred, hence offshore freshwater reserves are inferred in some coastal areas. The main attributes of palaeowaters, in terms of water quality, are their high bacterial purity, total mineralization that is often less than that of modern waters and being demonstrably free of anthropogenic chemicals. However, in the Mediterranean coastal areas, lower recharge leads to higher salinity conditions in both palaeo- and modern waters.
Freshwater of high quality originating from different climatic conditions to the present day, when the sea level was much lower, is found at depth beneath the present-day coastline in several countries. Recharge is shown to have been more or less continuous during the past 100 ka, even beneath the ice, as demonstrated by groundwaters from Estonia, having δO values of c. −22%o. However, elsewhere (UK and Belgium) an age gap can be recognized indicating that no recharge took place at the time of the last glacial maximum. Devensian recharge temperatures (soil air temperatures) were some 6°C colder across Europe than at the present day.

The development of aquifers in Europe during the past 50–100 a, by abstraction from boreholes, has generally disturbed flow systems that have evolved over varying geological timescales, especially those derived from the Late Pleistocene and Holocene. Hydrogeophysical logging has demonstrated time and quality stratified aquifers resulting in mixed waters being produced on pumping. A range of specific indicators, including
3
H,
3
H/
3
He,
85
Kr, chlorofluoro-carbons and pollutants, have been used to recognize the extent to which waters from the modern (industrial) era have penetrated into the aquifers, often replacing the natural palaeogroundwaters.

In the coastal regions, many problems for management are identified, including issues relating to quantity and quality of water, seasonal demand, pollution risks and ecosystem damage, requiring a new look at legislation.
Evidence for palaeowaters in the coastal aquifers of France
Authors: Dever L. , Travi Y. , Barbecot F. , Marlin C. , Gibert E. 
Published: April 2008

Abstract
Over time, coastal aquifers, which constitute a great part of available freshwater resources from sedimentary basins in France, have been subjected to changes in hydraulic gradients and hydrodynamic properties, mainly due to discharge-recharge phases in response to sea-level variations and/or human influences. This work aims to understand the salinization process originating from the recharge-discharge conditions as recognized at three sites: the calcareous Dogger aquifers along the English Channel (Caen area); along the Atlantic coast (Marais Poitevin), and the Astian sandy aquifer (Cap d’Agde). In addition to conventional hydrogeological and hydrochemical techniques, the main tools used for investigation are those of isotope geochemistry.

For the three study sites, the evolution of isotopic signatures along a flow path, depending on the mineralogy of the aquifer matrix, is linked to water-rock interactions such as cation exchange and equilibrium with aluminosilicates. Residence times of these fresh groundwaters are from Modern (Atlantic site) up to the
14
C detection limit (English Channel site). Groundwater of the Astian aquifer (Mediterranean) belongs to the Holocene, as determined by
14
C analyses.

The saline waters identified in the three study sites have a marine origin and were modified either by interaction with organic-rich layers, by cation exchange, or by deep carbon input. The salinization process has been associated with marine overflow onto a plain and to an upward leakage of water rich in CO
2
. The marine intrusion registered in the English Channel and Atlantic aquifers is associated with the Flandrian transgression; for the Astian aquifer, the salinization is related to mixing with older water.
Hydrochemical modelling as a tool for understanding palaeowaters
Authors: Van Der Kemp W. J. M. , Appelo C. A. J. , Condesso De Melo M. T. , Gaus I. , Milne C. J. , Walraevens K. 
Published: April 2008

Abstract

Hydrogeochemical modelling was used to interpret water-sample analyses of three European aquifers: the East Midlands Triassic Sandstone (UK), the Tertiary Ledo-Paniselian (Belgium) and the Aveiro Cretaceous aquifer (Portugal). Soil CO
2
pressures at recharge,derived from inverse chemical modelling, correlate well with δ
18
O of the water. Higher soil CO
2
pressures correspond to less negative δ
18
O of the recharge water, indicating higher recharge temperatures. This trend is confirmed by noble gas temperatures from the East Midlands aquifer. Cation exchange and carbonate reactions were the most important chemical processes that contributed to the groundwater composition of all three aquifers. Transport modelling of the water quality of the Ledo-Paniselian aquifer confirmed the importance of cation exchange and elucidated that recharge of this aquifer occurs through preferential pathways.
‘Had Lord Kelvin a right?’: John Perry, natural selection and the age of the Earth, 1894–1895
Authors: Shipley Brian C. 
Published: April 2008

Abstract

The Marquis of Salisbury’s 1894 address to the British Association for the Advancement of Science sparked an important development in the debate on the age of the Earth. It led John Perry, a physicist, to produce the first mathematical rebuttal of Lord Kelvin’s calculations, which had since 1862 functioned as an argument against the theory of evolution by natural selection. Perry wished to affirm the independence of geology from physics, keeping each branch of science to its proper domain. With the support of his mathematical friends, Perry tried privately to induce Kelvin to modify his views. This effort failed, however, and the discussion became public in
Nature
. Perry supported his calculations with Heaviside’s new mathematical methods, and also with empirical data, though these were later undermined by Kelvin’s experiments. Perry was uncomfortable with his position as Kelvin’s critic, however, because he held his old teacher in great esteem. Although Kelvin never stopped believing that the Earth was too young for natural selection to have taken place, geologists and biologists responded very positively to Perry’s results, and no longer felt they had to justify their conclusions to physicists. The answer to ‘Had Lord Kelvin a right?’, ultimately depended on one’s scientific politics.
Arthur Holmes’ vision of a geological timescale
Authors: Lewis Cherry L. E. 
Published: April 2008

Abstract
Arthur Holmes (1890–1965) was a British geoscientist who devoted much of his academic life to trying to further the understanding of geology by developing a radiometric timescale. From an early age he held in his mind a clear vision of how such a timescale would correlate and unify all geological events and processes. He pioneered the uranium-lead dating technique before the discovery of isotopes; he developed the principle of ‘initial ratios’ thirty years before it became recognized as the key to petrogenesis, and he wrote the most widely read and influential geology book of the twentieth century. But despite all this, much of his contribution to geology has gone unrecognized in the historical literature. This paper attempts to redress this omission, to dispel some of the myths about Holmes’ life, and to trace his contribution to the development of the geological timescale.