bluuebunny/crossref_metadata_2025_split huggingface dataset:
Palaeomagnetism and Sm-Nd ages of the Neoproterozoic diabase dykes in Laanila and Kautokeino, northern Fennoscandia
Authors: Mertanen S. , Pesonen L. J. , Huhma H. 
Published: April 2008

Abstract
The results of palaeomagnetic, rock magnetic and isotope data on the NE-SW trending Neoproterozoic Laanila-Ristijärvi (Finland) and Kautokeino (Norway) dyke swarms, northern Fennoscandia, are reported. Positive baked contact tests in both dyke sets indicate that the characteristic remanence is primary thermoremanence. Rock magnetic and petrological properties show similarity between the two dyke swarms. All the dykes except one (where the dominant carrier is Ti-rich titanomagnetite) have mixed multidomain and single-domain or pseudosingle-domain magnetic carriers of Ti-poor magnetite. From its remanence directions, petrography and rock magnetic properties, the easternmost of the three Laanila dykes represents a deeper crustal level than the other two dykes studied. Palaeomagnetic and aeromagnetic data suggest that the Palaeoproterozoic granulite block containing the easternmost Laanila dyke was uplifted after the dykes were emplaced.

The Sm-Nd isotopic age determinations yield an age of 1042 ± 50 Ma for the Laanila dykes, 1013 ± 32 Ma for the Ristijärvi dykes and 1066 ± 34 Ma for the Kautokeino dykes indicating that the dyke swarms are of similar age within error limits. However, palaeomagnetic pole of the Laanila-Ristijärvi dykes (P
lat
= 2.1 °S, P
long
= 212.2 °E, dp = 12.7°, dm = 21.1°,
N
= 3 dykes) differs significantly from the pole of the Kautokeino dykes (Plat = 35.2 °S, P
long
= 236.8 °E,
N
= 2 dykes). The isotope and palaeomagnetic ages of the Laanila-Ristijärvi dykes are considered agreeable, but on the basis of younger precisely dated Sveconorwegian palaeopoles, a magnetization age of
c.
900 Ma for the Kautokeino dykes is inferred. Three explanations for the discrepancy are suggested: (i) local tectonic movements, (ii) delayed magnetization of the Kautokeino dykes with respect to that of the Laanila-Ristijärvi dykes, (iii) the isotope ages and palaeomagnetic ages are compatible but the Fennoscandian APWP should be revised.
Provenance of late Proterozoic Dalradian tillite clasts, Inner Hebrides, Scotland
Authors: Fitches W. R. , Pearce N. J. G. , Evans J. A. , Muir R. J. 
Published: April 2008

Abstract

A geochemical and isotopic study was made of granitoid clasts taken from the
c.
660 Ma Dalradian tillites of Islay and the Garvellach Islands. Objectives were to investigate tillite provenance as a means of helping to characterize the ages, compositions and distributions of basement rocks near and beneath the Dalradian Supergroup. Most clasts have closely similar trace element and REE compositions, implying that they were derived from source rocks produced in similar, but not necessarily coeval, geotectonic settings. Most samples have geochemical traits of Within-Plate Granites. Nd isotopic model ages of
c.
2.0 Ga were obtained from several clasts. One sample gave a Rb-Sr mica whole-rock age of
c.
1.57 Ga, which is probably close to the age of igneous crystallization.

The clasts are petrographically similar to the syenites of the Rhinns Complex, the
c.
1.8 Ga alkalic igneous suite exposed locally in the Hebridean region SE of the Great Glen Fault. Most clasts, however, are geochemically distinct from the Volcanic Arc-type Rhinns Complex. The isotopic model ages of the clasts overlap those of the Rhinns Complex, but the
c.
1.57 Ga age of one clast is substantially younger. Although most clasts were not eroded from the Rhinns Complex of the type presently exposed, it is possible that they were derived from plutonic rocks closely associated in space and time with the Rhinns Complex. The source plutons and the Rhinns Complex were probably components of the early to Proterozoic Sveccofennian-Ketilidian-Labradorian-Makkovikian mobile belt which contains voluminous plutonic rocks with diverse ages and compositions.
The role of geochemistry in environmental and epidemiological studies in developing countries: a review
Authors: Plant J. A. , Baldock J. W. , Smith B. 
Published: April 2008

Abstract
Concern over the effects of chemicals in the environment on the health of man and animals is growing as rapid economic and population growth extends such problems as land degradation, pollution and urbanization from industrialized nations to the developing world.
In this paper we review the principal socio-economic and environmental pressures on developing countries before discussing the role of geochemistry in: (1) preparing high resolution baseline data to identify potential hazards; (2) understanding the pathways of chemical elements from rocks and soils to man and animals; and (3) developing amelioration strategies to reduce the impacts of inappropriate land use, power generation and mining. The particular geochemical problems of tropical terrains are discussed and some case histories from the international work of the British Geological Survey (BGS), funded by the Overseas Development Administration, are described.
It is recommended that developing nations prepare modern geochemical maps, ideally to the standards set out in International Geological Correlation Programme Project 360 World Geochemical Baseline, and that aid agencies should fund integrated environmental geochemical surveys as being of primary importance, especially for health studies and land use planning; particular attention should be paid to the environmental impact of urbanization. Further understanding of chemical and mineralogical speciation is required to improve the interpretation of geochemical data for environmental purposes.
Multidisciplinary studies, involving epidemiologists, biochemists and nutritional specialists, are essential if natural and anthropogenic impacts are to be properly assessed and practical amelioration measures implemented.
Formation of cave salts and utilization by elephants in the Mount Elgon region, Kenya
Authors: Bowell R. J. , Warren A. , Redmond I. 
Published: April 2008

Abstract
Herbivores such as the African elephant receive most of their nutrient uptake through digested vegetation or water. When these nutrient sources do not fulfil dietary requirements, eating and digestion of soil and rock can be a common phenomenon. In the Mount Elgon National Park on the Kenya-Uganda border, elephants have taken this activity one step further. Deposits of calcium-sodium-rich alkaline rocks show evidence of quarrying by elephants on the surface, but most of the activity takes place underground in caves. The Na-Ca-Mg-rich rocks are leached by groundwater which reacts with animal excreta in the humid environment of the cave floor to form a series of secondary carbonate, sulphate, halide, nitrate and phosphate minerals by evaporation. Additionally some salts are precipitated on the cave walls by direct evaporation of the cave waters. Inside the caves, elephants tusk and ingest the salt-enriched rock fragments. In an area like Mount Elgon, where supergene processes leach chemical elements essential for dietary requirements from the surface ecosystem, the secondary salts in the caves are potentially an important mineral supplement for wildlife nutrition. Although elephants are the principal exploiters, other wildlife species and humans (for livestock) also utilize the cave salts and surface diggings.
Groundwater geochemistry and health: an overview
Authors: Edmunds W. M. , Smedley P. L. 
Published: April 2008

Abstract
The natural geological and geochemical environment, in addition to providing beneficial mineral content and bioessential elements to groundwaters, may also give rise to undesirable or toxic properties through a deficiency or an excess of various elements. In this paper the controls on the release of toxic elements are considered together with the geochemical conditions that give rise to excess and deficiency. Many studies have pointed towards an inverse correlation between water hardness and cardiovascular disease and the associated mobility of metals in soft waters may also be a contributory factor. Under acidic conditions Al and Be as well as other metals may be released, whilst changes in redox conditions as well as pH will affect the mobility of Fe, Mn and As in particular. Some potentially toxic elements such as Ba and F are usually held at acceptable concentrations in groundwaters by the respective solubility controls of barite and fluorite; quality problems arise from these elements when groundwaters contain respectively low sulphate or low calcium concentrations. Deficiencies of Se and I (as well as F) in groundwater are related to the low geochemical abundance of these elements in certain environments. In the context of groundwater pollution it is important first to define the natural baseline concentrations of key elements of health importance.
Water quality and dental health in the Dry Zone of Sri Lanka
Authors: Dissanayake C. B. 
Published: April 2008

Abstract
The Dry Zone of Sri Lanka has mostly poor rural folk, who live in very close association with the immediate physical environment, depending on it for their living. Many of these people have lived in such a confined environment throughout their lives and it is reasonable to assume that at least some aspects of their health could be correlated with the geochemistry of their immediate environment.

Hydrogeochemical investigations of surface well water and deep well water in parts of the Dry Zone notably in the North Central Province, have shown that the fluoride concentrations often reach anomalously high levels, of the order of 10 mg
−1
in some instances. As a result of this, dental fluorosis is increasing in its prevalence among school children. With over 13 000 tube wells with hand pumps, mostly in the Dry Zone, the problem of dental fluorosis will assume serious proportions in the future unless methods of defluoridating household water supplies are developed.

An attempt has been made to implement a programme of defluoridating water supplies with a defluoridator using charcoal and charred bone meal. However, a major awareness programme is needed to educate the villagers of the dangers of excessive fluoride in drinking water and the need for community participation in maintaining household defluoridators.
Geochemistry of iodine in relation to iodine deficiency diseases
Authors: Fuge Ron 
Published: April 2008

Abstract

Seawater is the most important reservoir for terrestrial iodine (mean concentration 58 µgl
−1
I); this is a major influence on iodine distribution in the secondary environment. Volatilization of iodine from the oceans, possibly as elemental iodine or as an organically-bound species, is the main source of the element in the environment. The distribution of iodine in the secondary environment is, therefore, largely controlled by proximity to the oceans, with rainwater and surface run-off relatively enriched in iodine in near-coastal regions. Soil iodine content is also strongly influenced with coastal soils being much enriched and central continental soils being depleted. Topography has a marked influence with soils in rain shadow areas being relatively depleted in iodine. While iodine input is a major controlling influence on its geographical distribution in soils, the soil’s ability to retain iodine is also an important factor. Organic matter together with iron and aluminium oxides and clays are the important sinks of soil iodine.

An additional factor in the distribution of iodine in the secondary environment, and its subsequent availability to the biosphere, relates to its speciation in soils. In acid oxidizing conditions iodine is likely to be present as the I
−
ion and as such liable to be volatilized as I
2
. In near-neutral or alkaline conditions iodine is likely to be present as the IO
3
−
ion which is not volatilized. Soils in limestone areas, with pH values of 7 and above, have thus been found to be much enriched in iodine compared to acidic soils in neighbouring areas.

It is suggested that iodine from oceanic sources migrates in a series of ‘steps’ across landmasses by deposition followed by revolatilization. High pH soils and organic-rich soils then act as a migration barrier for iodine. In addition, it is suggested that volatilized iodine is bioavailable and any geochemical barrier to such volatilization deprives the biosphere of a major source. In this context it is interesting to note that several goitre endemias occurred in areas with limestone bedrock.
Preliminary studies of acid and gas contamination at Poas volcano, Costa Rica
Authors: Nicholson R. A. , Roberts P. D. , Baxter P. J. 
Published: April 2008

Abstract
Primary volcanic phenomena are potentially catastrophic, whilst those of a secondary nature may be merely considered as background activity but may be of sufficient intensity to cause long-term suffering to indigenous populations. The latter is the case at Poas volcano in Costa Rica, where a change in the quiescent state of the volcano has been shown by increasing activity during the last decade. Acid gases are apparently now being emitted more intensely than before, particularly during the dry season, to the detriment of the health of people and domestic livestock living in the surrounding countryside. Damage to crops and farm buildings is also evident.
A pilot geochemical study has been undertaken at Poas volcano to determine the principal constituents of the gas emissions, the form in which they are most likely to be transported and the extent of the area within which they can be easily measured.
The results obtained indicate that emissions of mixed volatile acids contribute to the problems encountered, and that, as might be expected, seasonal changes and distance from the source also exert control. Rainfall effectively scrubs the acid gases during the wet season, thereby considerably ameliorating the immediate effects of the emissions.
A re-evaluation of Middle and Upper Jurassic stratigraphy and the flooding history of the Moray Firth Rift System, North Sea
Authors: Davies Richard J. , Stephen Kevin J. , Underhill John R. , Davies Richard J. , Stephen Kevin J. 
Published: April 2008

Abstract
The application of a sequence stratigraphic approach to the study of the Middle and Upper Jurassic of the Moray Firth has enabled the stratigraphy of disparate onshore and offshore successions to be linked and clarified. The results allow for the construction of regional correlation panels, chronostratigraphic diagrams and palaeogeographic maps which illustrate the tectono-stratigraphic evolution of the basin and importantly show a new flooding history for this arm of the North Sea rift system. It is now demonstrable that the Inner Moray Firth (IMF) and Outer Moray Firth (OMF) were separated by a topographic high centred around the Ross Granite area (UKCS blocks 13/28 and 13/29) from the Bajocian until the latest mid-Oxfordian. New biostratigraphic results demonstrate that the first marine influx into the Buchan Trough area of the OMF was Callovian in age (significantly earlier than previous models) and probably marked connection with the South Viking and/or North Central Grabens. Similar marine depositional systems are envisaged to have developed in the geographically isolated IMF basin and Buchan Trough area of the OMF basin during the Callovian, early and mid-Oxfordian. The unification of these marine basins occurred during the latest mid-Oxfordian via the South Halibut Trough, with a subsequent early Kimmeridgian connection via the Halibut Platform. The new flooding model suggests that the drowning of the rift arm was more rapid than previously believed and that within the rift itself any relief associated with a Mid-Jurassic doming episode, which created ‘the Mid-Cimmerian Unconformity’ had effectively diminished by this time. Although the deflation of a triple junction-centred dome remained an important process in the basin’s Mid-Jurassic evolution it was not the sole causal control on rift-arm stratigraphy. Instead the complexities of the Mid- and Late Jurassic flooding of the Moray Firth are interpreted to be the result of both short- and long-term regional sea-level changes superimposed upon a complex evolving rift topography.
The role of trace fossil (ichnofabric) analysis in the development of depositional models for the Upper Jurassic Fulmar Formation of the Kittiwake Field (Quadrant 21 UKCS)
Authors: Martin M. A. , Pollard J. E. , Martin M. A. 
Published: April 2008

Abstract
The sedimentology and sequence stratigraphy of the Upper Jurassic (Upper Oxfordian — Middle Kimmeridgian) Fulmar Formation of the Kittiwake Field, Western Platform of the north Central Graben are investigated through an integrated study of core material and wireline logs. The Fulmar Formation, in this area, comprises largely finegrained sandstones which are intensely bioturbated such that the use of primary sedimentary structures for the identification of depositional environments is impractical. By using the approach of ichnofabric analysis presented here, the information provided by trace fossils can be fully utilized in the formulation of a depositional model for the Fulmar Formation.

A depth and substrate-related succession of ichnofabrics was determined for the Fulmar Formation from more complete and progradational successions. This attached shoreface succession extends from a
Chondrites
ichnofabric (offshore), through
Anconichnus
(upper offshore),
Anconichnus
and spreiten burrows and ‘
Teichichnus zigzag
’ (upper offshore-offshore transition zone), bivalve tube ichnofabric (offshore transition zone to lower shoreface),
Ophiomorpha irregulaire
(lower shoreface),
Ophiomorpha nodosa
(middle shoreface) to a burrow mottling ichnofabric and associated high-energy laminated sandstones (upper shoreface). Anomalies in this succession form the basis for the identification of bounding surfaces, particularly omission surfaces (
Thalassinoides
and
Diplocraterion habichi
ichnofabrics) and sequence boundaries.

The distribution and evolution of the essentially retrogradational succession of the Fulmar sandstones is illustrated by analysis of a detailed core log of well 21/18-3, a general cross section through the Kittiwake Field and an Early-Mid-Kimmeridgian time slice facies distribution map.
Facies controls on reservoir quality in the Late Jurassic Fulmar Formation, Quadrant 21, UKCS
Authors: Cannon S. J. C. , Gowland S. 
Published: April 2008

Abstract
Fulmar Formation sandstones have been assessed for reservoir quality in terms of their primary textural and sedimentological characteristics with respect to conventional core analysis data. Some 6000 ft of core were characterized in total using a comprehensive lithofacies scheme and the results integrated with porosity and permeability data to create a statistically valid data set. From this dataset the primary influences affecting reservoir quality have been evaluated for a discrete area of the Central North Sea. Simple cross-plotting techniques indicate general trends in reservoir quality related to lithofacies type and hence depositional energy levels in shoreline/shallow marine shelf environments. Dominant grain size trends are identified that also influence reservoir quality. Broad prograding, aggrading and retrograding sequences are recognized which can be used to sub-divide the reservoir and locally predict reservoir quality.
Upper Jurassic sandstone reservoir quality and distribution on the Fladen Ground Spur
Authors: Freer Geoff , Hurst Andrew , Middleton Paul 
Published: April 2008

Abstract

During the Oxfordian to Early Kimmeridgian much of the Fladen Ground Spur was a positive feature and sourced clastic deposition in the Piper Basin, Witch Ground and South Viking grabens. The
eudoxus
flooding event introduced shallow marine conditions onto the Fladen Ground Spur, and during the continuing transgression, a veneer of clastic sediments was deposited. Three facies units are defined: facies 1 — thin, low-high-energy glauconitic sandstone; facies 2 — medium-high-energy clean, well-sorted medium-grained sandstone; facies 3 — low-energy, fine-grained argillaceous sandstone. Reservoir quality is evaluated using porosity data from neutron porosity and bulk density logs. Porosity-permeability cross-plots provide a workable relationship for permeability prediction in uncored wells. Initial results show that, predictably, facies 2 sandstone has the best poroperm characteristics. Facies 1 sandstone contains locally derived clasts, the diverse nature of which affects reservoir quality. Subcrop is interpreted to be an important, if not causal, factor that controls reservoir quality in facies 1 sandstone.
Reservoir architecture and diagenesis in downthrown fault block plays: the Lowlander Prospect of Block 14/20b, Witch Ground Graben, Outer Moray Firth, UK North Sea
Authors: McCants C. Y. , Burley S. D. 
Published: April 2008

Abstract
The Lowlander Prospect is an Upper Jurassic, downthrown hydrocarbon accumulation, with three-way dip closure and fault seal developed within the Sgiath and Piper formations. The prospect was discovered in 1987 and has since been appraised by more than 900 ft of core from five wells. Detailed core description, conventional core analysis, thin section petrography, fluid inclusion microthermometry, stable isotope analysis and over 2000 ft of wireline petrophysical log interpretation were utilized in constructing an integrated reservoir and diagenetic model for the reservoir units in the prospect.
Piper Formation sandstones form the main reservoir in the Lowlander Prospect. Deposition of Piper Formation sandstones was controlled by three major structural elements which served as separate hinterlands; the Fladen Ground Spur and Piper Ridge to the northeast, Halibut Horst and Platform to the southwest, and regional Toarcian-Aalenian domal uplift to the southeast. Two major coarsening up sequences are present in the Lowlander Piper Formation that represent progradational strandline deposits. Transgressive abandonment sandstones, locally preserved beneath a top Piper Formation unconformity, represent a Volgian transgression and associated reworking of Piper Formation sediments.
Mechanical compaction and diagenetic cementation, the latter including early non-ferroan calcite, kaolin, quartz overgrowths, ankerite, late calcite and barite-sulphide mineralization, have resulted in generally low intergranular porosities in Piper Formation sandstones. However, total porosities are enhanced by the development of late, post-quartz overgrowth feldspar grain dissolution. Microthermometric study of fluid inclusions in quartz overgrowths indicates that precipitation of authigenic quartz took place at temperatures of between 88 and 122°C, concomitant with hydrocarbon migration. Best reservoir quality is developed adjacent to basin centre faults where early carbonate cements and detrital feldspars have been extensively dissolved. Higher depositional energy facies adjacent to the faults were the initial focal point for aggressive fluid ingress into the reservoir. Fluid migration away from the faults resulted in reprecipitation of carbonate cements up-structure towards the graben edges where reservoir quality is now the lowest. Structural highs thus need not be the prime exploration target in downthrown, hanging-wall basin centre plays.