bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of the GLEAMS model to assess groundwater pollution risk caused by animal waste land disposal
Authors: Garnier M. , Leone A. , Uricchio V. , Marini R.
Published: April 2008

In modern intensive animal farming the disposal of a large amount of waste represents a great concern. It is commonly accepted that the utilization of this waste as a fertilizer on agricultural soil has to be preferred to a treatment process that is extremely expensive and involves problems of final sludge disposal. Both solid and liquid animal wastes are an important resource for agriculture because they can substitute for synthetic fertilizers and contribute to the improvement of the soil structure. Land disposal of animal waste, particularly from swine husbandry, if not properly performed, can pollute surface and groundwater, mainly because of the high nitrate and phosphate content.

This paper presents the results of an application of the GLEAMS (Groundwater Loading Effects of Agricultural Management Systems) model, aimed at assessing the consequences on groundwater of animal waste application on different kinds of soils and agricultural arrangements, which are typical of the Chiana River Valley in central Italy. In this area this matter is of great concern because of the high concentration of swine breeding farms affecting directly a shallow unconfined aquifer.

GLEAMS model simulations were intended to assess the maximum rate of waste that can be applied on different types of soil, without exceeding in the aquifer the nitrate limit determined by law for drinking water. The results confirm that manure, although used according to regulations, in many cases does not allow such a limit to be respected, especially for the most sensitive soils. Some suggestions are given to identify a suitable quantity of animal waste for disposal that is compatible with minimizing the risk to groundwater in the area of concern.
Groundwater vulnerability and the Channel Tunnel Rail Link Bill
Authors: Bishop T. J. , Packman M. J. , Aldous P. J.
Published: April 2008

The Channel Tunnel Rail Link (CTRL) Bill 1994 authorizes the construction, mainten- ance and operation of a high speed rail link between St Pancras in London and Folkstone in Kent. Furthermore, the Bill makes identical provision for widening works associated with the A2 at Cobham and the M2 in Kent between junctions 1 and 4. The publication of the Bill raised a number of very serious issues affecting the responsibilities of both the Statutory Water Undertakers and those of the Environment Agency (the Agency). Furthermore, the Bill failed to define suitable mitigation measures that would reduce the risk of public groundwater supply contamination, introduced by the construction and operation of the CTRL, to within tolerable limits.

This paper explores how both the Promoters of this major transportation link and the water companies sought protective provisions utilizing the Agency's Groundwater Protection Policy and risk assessment methodologies in order to define the potential for groundwater contamination. This process culminated in the Statutory Water Undertakers presenting evidence at the All Party Parliamentary Select Committee in order to demonstrate the necessity for suitable protective measures. Furthermore, this paper assesses the current status of the Agency's Groundwater Protection Policy in the light of this major test of resolve and the apparent paradox of Statutory Duties for both the Agency and Statutory Water Undertakers with regard to groundwater contamination.
Delineating the horizontal and vertical extent of hydrocarbon contamination using laser induced UV fluorescence
Authors: Hughes J. P. , Taer A. D.
Published: April 2008

Before we can hope to successfully conduct a risk assessment, or select the proper technology for remediation at a contaminated site, we must first have a thorough understanding of the nature of the impacts at that site. This paper will present an overview of a field-proven,
in situ
site assessment technique based on laser induced UV fluorescence, that provides continuous, real time information on the distribution of hydrocarbons in the subsurface. The system can detect hydrocarbons regardless of whether they are located above or below the water table, and it gathers the data without generating any cuttings that could require costly disposal. This technology can also provide a qualitative ‘fingerprint’ of the hydrocarbons present at the site. Since the data are available in real time, adjustments to the site assessment programme can be made in the field. Examples of applications of this technology include using it as a screening tool to delineate both the horizontal and vertical extent of hydrocarbon contamination; estimating the volume of contaminated soil that may have to be addressed; or helping to select locations for more expensive confirmatory soil samples or permanent monitoring wells. Actual data from a number of sites will be presented to illustrate some of these applications.
Modelling biodegradation in a groundwater environment: choosing an appropriate method
Authors: Davison Ruth M. , Lerner David N.
Published: April 2008

The transport of contaminants through aquifers is a complex issue affected by advection, dispersion, sorption and biodegradation. Biodegradation is the only process which allows the contaminant mass naturally to be physically reduced. Due to the quantity of contaminated sites and the expense of remediation schemes it is essential to understand the natural attenuation provided by biodegradation. Modelling of the biodegradation processes provides not only the means to a fuller understanding of a plume's development but also the facility to test potential remediation schemes. A two-tier classification system is presented which summarizes the current literature regarding the modelling of biotransformations in saturated porous media. The first relates to the treatment of the physical microbial setting and the second tier relates to the reaction approach. The physical setting tier is discussed in the context of biofilms. The basic theory and various types of biofllm are summarized while discussing the evidence for and against the necessity of representing biofilms in biotransformation models. The techniques implemented to model biofilms are summarized, including the limitations and previous and potential applications. The reaction tier constitutes four sections: first-order decay models, instantaneous reaction models, Monod kinetic models and Michaelis—Menton kinetics. For each of the reaction approaches a physical and mathematical description is provided with an explanation of its relevance for the modelling of biotransformations. An approach for selecting the appropriate modeling techniques is illustrated for a contaminated site.
Contamination of sediments in the Forth Estuary, Scotland
Authors: Lindsay P. , Bell F. G. , Hytiris N.
Published: April 2008

This paper considers the contamination of sediments in the Forth Estuary. When trace metals are released into the water column they can be transferred rapidly to the sediment phase by adsorption onto suspended particulate matter, to be followed by sedimentation. Intertidal flats may be considered as important trace metal sinks since they accumulate large amounts of suspended matter. Hence, in polluted estuaries the deposition of suspended particles on intertidal flats may thus cause severe contamination. The Forth Estuary has unique contamination for British estuaries: it is experiencing significant Hg pollution. In addition, due to the presence of a nuclear submarine base in the Forth Estuary, Co
60
is detectable in the intertidal sediments. Temporal and spatial contamination patterns were analysed in relation to historical and present pollution point sources.
Estimation of solid phase activity coefficients for non-ideal cation exchange behaviour in laboratory samples of UK Triassic sandstones
Authors: El-Ghonemy H.
Published: April 2008

A traditional laboratory method for measuring cation exchange parameters was applied to plugs of Triassic sandstone core. The objective of the study was to measure cation exchange capacities and selectivity coefficients in the Ca—Mg−Na—K system in intact rock samples, and to investigate the extent to which the system departs from ideality. The method involved the use of NH
4
Cl as a high ionic strength exchange salt solution in column experiments. Non-ideal behaviour was observed, being most obvious for the K—Na, K—Mg and K—Ca exchange systems. Activity coefficients for the exchanger phase were estimated and a dependence on the composition of the exchanger was recognized. An equation for exchange equilibria is proposed where this dependence is accounted for in the form of a power function.
An initial evaluation of Synperonic PE surfactants as soil washing agents
Authors: Paterson Iain F. , Chowdhry Babur Z. , Leharne Stephen A.
Published: April 2008

The utility of the Synperonic PE range of block copolymeric nonionic surfactants in the decontamination of soil is systematically investigated. In the case of the solubilization of naphthalene in the absence of soil by the six Synperonic PE surfactants studied, the molar solubilization ratio (MSR), which is a measure of the solubilizing power of surfactants in their aggregated (i.e. micellar) form, broadly increases with an increase in the weight percentage content of the hydrophobic polypropylene oxide portion of the surfactant. Significantly, solubility enhancements are substantial even below the tensiometrically determined critical micelle concentration. The sorption of a number of these surfactants onto a soil of organic carbon content 0.6% is shown to be described by Freundlich isotherms, and is significant, adding considerably to the organic content of the soil. However, the surfactants substantially reduce the soil-water partition coefficient of naphthalene, phenanthrene and pyrene, indicating that they may potentially find applications in soil decontamination.
High-altitude glacial lake hazard assessment and mitigation: a Himalayan perspective
Authors: Reynolds John M.
Published: April 2008

Glaciers throughout the Himalayas have been receding rapidly over the last few years. In the areas vacated by the ice snouts lakes have formed behind large moraine dams. As with their Andean counterparts, these lakes can pose significant threats to downstream towns, roads and power schemes. For a developing country like Nepal, for example, the prospective loss of economically vital infrastructure and food-producing land can be devastating, in addition to the human misery.

The Tsho Rolpa glacier lake has formed by the retreat of Trakarding Glacier at the head of the Rolwaling Valley in northern Nepal. The lake is now over 3 km long and contains an estimated volume of 80 x 10
6
m
3
. The snout of Trakarding Glacier terminates in the lake which, at its western end, is dammed by an ice-cored moraine. It is feared that the lake could be the source of a major glacier lake outburst flood (known locally as a ‘GLOF’) which could destroy the nearby villages of Na and Beding, as well as trekking routes, vital bridges,
etc.
, further downstream. At Khimti, 80 km downstream from Tsho Rolpa, a new hydroelectric power scheme is being built and could potentially be at risk.

It is known that the local glaciers in the Rolwaling Valley have been the source of many GLOFs in historical as well as contemporary times. The last GLOF destroyed several houses and valuable farm land at Beding in July 1991.

Following an initial GLOF-risk assessment in September 1994, a trial siphon was installed at Tsho Rolpa in May 1995. This is the first time that such measures have been used in the Nepalese Himalayas. Since then further remediation measures have been proposed and are awaiting funding. The nature of the glacial hazards at Tsho Rolpa and the engineering mitigation measures being proposed are described. Furthermore, it is concluded that an integrated national policy on glacial hazards should be developed urgently.
Coastal cliff behaviour and management: Blackgang, Isle of Wight
Authors: Moore R. J. , Clark A. R. , Lee E. M.
Published: April 2008

In January 1994 coastal erosion and landslide activity at Blackgang, Isle of Wight, resulted in a dramatic retreat of the coastal cliffs and landward extension of ground movement. The initial impact of the event involved the destruction of two cottages, an access road, several cars and caravans, and around 12 homes had to be evacuated. The event raised considerable local and national media attention.

The initial landslide response was co-ordinated by South Wight Borough Council, with advice from Rendel Geotechnics, and was aimed at ensuring public safety and security in the area. A detailed investigation was subsequently carried out to identify the extent and causes of coastal instability and cliff recession in the context of ‘cliff behaviour units’. An understanding of the characteristic cliff behaviour units has proved the key to assessing future landslide and cliff recession potential as well as identifying options for coastal cliff management at Blackgang.

The coastal cliffs have been significantly oversteepened by the latest events and appear to be very sensitive to rainfall, with only relatively moderate to high winter rainfall totals expected to cause further cliff-top retreat and landslide reactivation. Consequently, in the absence of a financially and environmentally acceptable slope stabilization and coast protection scheme, continued managed retreat of cliff-top development and land use is seen as the only viable option.
Engineering hazards in the Taroko Gorge, eastern Taiwan
Authors: Petley D. N.
Published: April 2008

The population of Taiwan is concentrated on the low-lying coastal strips, separated by the Central Mountains. Whilst communication across the island is economically essential there are only three usable roads. This paper investigates natural hazards on the easternmost section of one of these roads, the Central Cross Island Highway. In the study area the road follows the base of the 600 m deep Taroko Gorge in a series of tunnels and rock ledges. The road is heavily used for transport whilst the gorge is one of the nation’s premier tourist attractions.

Maintenance of the road in Taroko Gorge represents a profound challenge to the engineering geologist. The walls of the gorge are composed of deformed marble, gneiss and schist and are prone to failure under the intense seismic activity. Additionally the area is prone to an average of three to four tropical cyclones per annum, with up to 1200 mm of rainfall in each.

A detailed geomorphological and engineering survey of the gorge has been undertaken. The data are analysed along with information obtained from the highway maintenance board. It is demonstrated that during typhoons the area suffers an unusually severe set of geological hazards. The heavy rainfall initiates rockfalls and landslides along the gorge. Flooding occurs widely both as a result of the increased discharge of the river and as a result of water cascading onto the road from the adjacent cliffs. The destruction of important bridges may also occur. An examination is made of the magnitude of these hazards, and techniques used by the highway authority are described and analysed in relation to the use of the road for both transport and tourism.
Mitigating geohazards affecting mountain roads in northeast Somaliland
Authors: Nathanail Paul , Nathanail Judith
Published: April 2008

Roads linking the Gollis plateau with sea ports on the Gulf of Aden descend a steep escarpment. The roads are continually affected by erosion and degradation. These usually gentle processes constitute significant geohazards to the communities on the plateau which rely on the roads to export their agricultural produce as they attempt to rebuild the local economy following years of civil war. Engineering geological advice was provided to local communities involved in maintaining and repairing three roads, in areas occupied by different Somali clans. The absence of advice at an earlier stage had resulted in much wasted effort in inappropriate realignments and gradients.

By tailoring the advice to the materials, tools and skills available locally, one road could be re-opened and two could be significantly improved, reducing travel times for laden lorries by up to half.
A hazard map of the Magnesian Limestone in County Durham
Authors: Green M. R. , Forth R. A. , Beaumont D.
Published: April 2008

A large part of County Durham is underlain by carbonate rocks of Permian age, principally Magnesian Limestone. In recent years problems have been encountered in constructing on the Permian carbonates, due to dissolution followed by subsidence and/or sink hole formation.

Features believed to be triggers for dissolution of limestone have been mapped and a weighted factor hazard map has been created. The map is based on an extensive review of existing site investigation data including a study of aerial photographs. Records of dissolution features noted by the County Council engineers have been incorporated into the hazard map. The map is intended as a guide for County Council Engineers who are planning site investigations within the area. The preparation of the map and its limitations are discussed.
Landslide susceptibility mapping using the Matrix Assessment Approach: a Derbyshire case study
Authors: Cross Martin
Published: April 2008

Civil engineering schemes such as new highways and railway lines, regional planning and large-scale land-management projects in areas known to have a landslide problem require regional landslide susceptibility evaluation. The Matrix Assessment Approach (MAP) is introduced as a medium-scale landslide hazard mapping technique for establishing an index of slope stability over large areas. The method allows the relative landslide susceptibility to be computed over large areas using a discrete combination of geological/geomorphological parameters. MAP was applied to a region in the Peak District, Derbyshire. The model identified key geological/geomorphological parameters involved in deep-seated failures, provided an effective means of classifying the stability of slopes over a large area and successfully indicated sites of previously unmapped landslides. The resultant regional landslide susceptibility index provides useful preliminary information for use at the desk study and reconnaissance stages of large-scale civil engineering works such as highway construction.
Subsidence hazards caused by the dissolution of Permian gypsum in England: geology, investigation and remediation
Authors: Cooper A. H.
Published: April 2008

About every three years natural catastrophic subsidence, caused by gypsum dissolution, occurs in the vicinity of Ripon, North Yorkshire, England. Holes up to 35 m across and 20 m deep have appeared without warning. In the past 150 years, 30 major collapses have occurred, and in the last ten years the resulting damage to property is estimated at about £1000000. Subsidence, associated with the collapse of caves resulting from gypsum dissolution in the Permian rocks of eastern England, occurs in a belt about 3 km wide and over 100 km long. Gypsum (CaS0
4
.2H
2
0) dissolves rapidly in flowing water and the cave systems responsible for the subsidence are constantly enlarging, causing a continuing subsidence problem.

Difficult ground conditions are associated with caves, subsidence breccia pipes (collapsed areas of brecciated and foundered material), crown holes and post-subsidence fill deposits. Site investigation methods that have been used to define and examine the subsidence features include microgravity and resistivity geophysical techniques, plus more conventional investigation by drilling and probing. Remedial measures are difficult, and both grouting and deep piling are not generally practical. In more recent times careful attention has been paid to the location for development and the construction of low-weight structures with spread foundations designed to span any subsidence features that may potentially develop.
Digital image texture analysis for landslide hazard mapping
Authors: Mason P. J. , Rosenbaum M. S. , Moore J. McM.
Published: April 2008

Textural enhancements using co-registered, multi-temporal, digital remotely sensed imagery have been used to study slope instability at three landslide localities. The remotely sensed imagery consists of Landsat TM, SPOT Pan and Daedalus 1268 Airborne Thematic Mapper (ATM); stereo, black and white aerial photographs have also been used. Image processing provides spatial and textural information concerning landform change, landslide location and morphology. The enhanced imagery can be integrated with digital elevation models (DEMs), as can other map and geotechnical data, into a GIS to analyse quantitatively the effect of slope geometries on the observed landsliding. The suitability of available imagery depends upon the type and scale of the study and the landslide dimensions. The case histories have shown that spatial resolution is the most important parameter for successful landslide identification. The optimum imagery is provided by a combination of textural and spectral enhancements using different types of imagery.
Acid mine drainage and pollution: two case histories from South Africa
Authors: Bell F. G. , Bullock S. E. T. , Geldenhuis S.
Published: April 2008

Different types of waste waters and effluents may be produced as a result of mining. They arise due to the extraction or preparation of the mineral deposit or from the disposal of associated spoil. Generally the major pollutants are suspended solids, dissolved salts or acidity. In the latter case acid mine drainage refers to the oxidation of sulphide minerals, notably pyrite, which are exposed in the mine or are present in the spoil. The primary oxidation products of pyrite are ferric and ferrous sulphates, and sulphuric acid. Two case histories are provided which deal with the problem of acid mine drainage associated with mines in South Africa. The first refers to a tin mine in the Transvaal where acidic waters were produced by heaps of pyrite discard. As the mine was due to close, the problem of possible groundwater pollution due to acid mine drainage had to be investigated as part of the environmental management programme. The second case history involves a coal mine in the Eastern Transvaal which was seeping an appreciable load of acidic effluent and salts into the headwaters of the Vaal River, which is a major source of water to the main industrial conurbation of the country. Investigations which included a study of the history of the site, geology, geophysics, hydrology, hydrogeology and geochemistry succeeded in clarifying the sources of the acidic seepage and the remedial measures that would have the greatest chance of success.
Improved methods for developing and visualizing remediation strategies
Authors: Hatton W. , Hunter G. , Hall D. , Haigh D.
Published: April 2008

Remediation of contaminated sites can be both costly and time-consuming. In order to ensure that a cost-effective remediation method is selected, several options are usually considered. VULCAN, a 3D modelling package, has been used to demonstrate the development and visualization of remediation strategies using site assessment data.

At a former chemical manufacturing facility, 71 samples were collected from 31 boreholes. Concentrations of the contaminant were measured in all samples and visualized using the 3D package.

Remedial options were considered and a benefit analysis performed. This considered positive benefits, such as attainment of clean-up levels, and negative benefits, such as excavation and associated costs. Optimization of the most cost-effective method was then performed using the Lerchs-Grossman algorithm.
Development of ‘rockhead’ computer-generated geological models to assist geohazard prediction in London
Authors: Strange P. J. , Booth S. J. , Ellison R. A.
Published: April 2008

Much of London is founded on Quaternary river terrace deposits, consisting mainly of sand and gravel associated with the course of the River Thames. The base of these Quaternary river terrace deposits, the ‘rockhead’ surface, is generally planar and rests on London Clay. Locally, however, the terraces may include steep-sided, gravel-filled hollows, some of which penetrate other solid formations below the London Clay, such as the Lambeth Group (formerly known as the Woolwich and Reading Beds).

Unforeseen engineering problems involving deep foundation construction or tunnelling beneath London have resulted from failure to predict irregularities in the base of Quaternary deposits. Detailed knowledge of the three-dimensional shape of the Quaternary deposits can assist in predicting ground conditions. In order to provide such a model more than 22 000 borehole records from London have been encoded into a digital, relational database. Contour plots of specific geological surfaces, including the top of the Chalk, the base of the London Clay and the base of the Quaternary deposits have been generated from the database using computer-modelling software.

Quality assurance is an important part of the databasing procedure and suspect borehole information is discarded at an early stage. As computer modelling proceeds, further data may be eliminated if considered anomalous. The computing infrastructure provides graphical presentations of borehole logs, contour plots, isopachyte (thickness) plots of the major geological units together with cross-sections, fence diagrams, block diagrams and perspective views, giving an enhanced, three-dimensional understanding of the geology of London.
Subsidence hazard assessment as a basis for planning guidance in Ripon
Authors: Thompson Alan , Hine Peter , Peach Denis , Frost Lindsay , Brook David
Published: April 2008

The Ripon area of North Yorkshire provides a well-documented example of subsidence problems caused by the natural dissolution of gypsum deposits. This paper summarizes the findings of a programme of research, commissioned by the former Department of the Environment, which has aimed to assess the degree of hazard associated with this particular form of subsidence and to develop appropriate planning and engineering responses which might be applicable both to Ripon and to other affected areas. The paper draws attention to the sensitive nature of the problem and to the conflict which exists between the benefits of using hazard assessment to minimize the risk to future development within an area, and the possible disbenefits of widely publicizing the existence of a land instability problem.

In Ripon, the potential consequences of gypsum-related subsidence, in terms of building damage and road closures, can be significant. In addition, there may be a small risk of personal injury. It is therefore important that the planning of future development in the area should be guided by the results of the hazard assessment carried out in this study and that such development should be subject to controls and mitigation measures, where appropriate. However, the probability of this form of subsidence occurring at any given site is very low and the risk to individual properties is therefore generally very small, especially from the statistical viewpoint normally adopted by insurers. Taking account of these facts, forward planning and development control procedures have been recommended for use by the local planning authority.
Grade and time of metamorphism in the Caledonide Orogen of Britain and Ireland
Authors: Fettes D. J. , Long C. B. , Bevins R. E. , Max M. D. , Oliver G. J. H. , Primmer T. J. , Thomas L. J. , Yardley B. W. D.
Published: April 2008

Plate 3 depicts three major belts distinguished by their style and age of metamorphism: the orthotectonic and paratec-tonic zones of the Caledonides and the Hercynides. Age of metamorphism, shown on the inset map (Plate 3), in part reflects the areal distribution of these zones and refers to the timing of the main phase or peak of metamorphism. The orthotectonic zone is, therefore, shown to be metamorphosed during the earliest Ordovician although recrystaHization was almost certainly taking place from the late or even mid-Cambrian to the Silurian. In the paratec-tonic belt the main metamorphism is shown as occurring in the period Lower Ordovician-to-Silurian although recrystahization may well have continued into the Lower Devonian. The Lower Devonian rocks within the central and southern Caledonides have suffered folding and weak metamorphism normally before Middle Devonian times and have been differentiated on the map.

The southern limit of significant Caledonian deformation is normally taken as the northern edge of the Midland Block (F. W. Dunning, pers. comm.). However, it is believed that weak Caledonian metamorphism affected rocks south of this line. Similarly, recrystaHization associated with the Hercynian extended well to the north of the so-called Hercynian front, the northern limit of strong deformation (F. W. Dunning, pers. comm.). There is, therefore, some doubt as to whether the main recrystaHization in pre-Carboniferous rocks of South Wales and the English Midlands relates to the late-Caledonian or to the Hercynian.
Palaeomagnetic constraints on the position of Gondwana during Ordovician to Devonian times
Authors: Bachtadse V. , Briden J. C.
Published: April 2008

The currently available palaeomagnetic data base for Gondwana is reviewed and using revised rotation parameters for the fit of the southern continents an attempt has been made to construct an apparent polar wander path for Gondwana during Ordovician to Permo-Carboniferous times using a cubic spline fitting technique. Although the density of the data set is still rather sparse and the quality of the data is variable, our approach seems to be justified when tying the apparent polar wander path to selected palaeopoles of high quality. The palaeogeographic scenario based on our results is rather complex. Rapid northward shift of Gondwana during the Ordovician to the Early Silurian and subsequent collision with Laurentia is followed by divergence and the formation of a wide intervening ocean during the Devonian. The final closure of this ocean did not begin before the Late Devonian and was completed by the Late Carboniferous. If the apparent polar wander path presented in this paper is correct, then extremely high drift rates of about 23 cm a
-1
have to be postulated for Gondwana during the Late Ordovician-Silurian.
Palaeozoic palaeogeography from palaeomagnetism of the Atlantic-bordering continents
Authors: Kent Dennis V. , Van Der Voo Robert
Published: April 2008

Revised palaeogeographic reconstructions of the Atlantic-bordering continents and intervening terranes are presented for the Siluro-Devonian boundary, Early Devonian, and Late Devonian, based on incorporation of new palaeomagnetic results that have become available from Laurentia and Gondwana. The key features of the palaeogeographic model are the transpressive collision between the eastern margin of Laurentia and the northwest South American margin of Gondwana in the Siluro-Devonian, and the subsequent Devonian retreat of the north African margin and the development of a wide ocean between Africa and Europe by the Late Devonian. Although rather complex and involving rapid motions especially of Gondwana, the revised Devonian plate tectonic evolution as indicated by palaeomagnetism is not inconsistent with biogeographic and palaeoclimatological evidence.
Palaeoclimatic constraints for palaeozoic Palaeolatitudes of Laurentia and Euramerica
Authors: Witzke Brian J.
Published: April 2008

Palaeozoic lithic palaeoclimatic data were plotted at the series or stage level for Laurentia (North America) and Euramerica. Their distribution was used to infer the extent of humid and arid climatic belts across the continent for specified time intervals. Climatic data are potentially useful for constraining palaeolatitudes for times when zonal atmospheric circulation remains the dominant pattern. Arid lithic indicators (evaporites, carbonate oolite) and humid indicators (coal, bauxite) were constrained to provide the best fit of these data into a simple zonal climatic pattern delineating subtropical arid belts and equatorial and/or temperate humid belts, respectively. An attempt was made to minimize occurrences of arid indicators in interpreted equatorial regions to maximize a zonal fit. Climatic belts can be arranged in a temporally consistent zonal climatic scheme for much of the Palaeozoic, but monsoonal and orographic effects apparently disrupted the general zonal pattern during portions of the Late Palaeozoic. The interpreted climatic patterns suggest progressive southward movement of Laurentia during the Cambrian through Early Devonian followed by general northward drift of Euramerica during the Middle Devonian through Permian. Lithic palaeoclimatic data provide an independent means to test palaeolatitudes interpreted from palaeomagnetic data. There is general agreement between palaeoclimatic and palaeomagnetic interpretations, but some discrepancies, particularly for the Devonian and Early Carboniferous, warrant further attention.
Biogeography of Ordovician and Silurian faunas
Authors: Cocks L. R. M. , Fortey R. A.
Published: April 2008

The new reconstructions generated for this volume fit well with the majority of Ordovician and Silurian faunal data and are a great improvement on previous attempts. The distribution of selected trilobites, brachiopods and graptolites are plotted on the new maps and confirm the importance of palaeolatitude in controlling the faunal distributions, particularly of the old cratons, which are shown for the Early Ordovician and Late Silurian. Two contrasting patterns of cratonic faunas are (a) disjunct or (b) gradational across a large palaeocontinent, e.g. Gondwana. Marginal and deeper-water biofacies show different patterns, which help to define the edges of palaeocontinents, but which are not so constrained in their palaeolatitudinal distributions. In contrast pelagic trilobites do not help to define palaeocontinents, but were sensitive to palaeo temperature and palaeolatitude. Specific case histories are considered, in particular the closing of Iapetus and the contemporary widening of the Rheic Ocean and the positioning of Avalonia, and the ancestry of the various associated trilobite and brachiopod genera during the later Ordovician. The Ashgill deeper-water
Foliomena
fauna is also plotted.
Biogeography of the Devonian stromatoporoids
Authors: Stock C. W.
Published: April 2008

Stromatoporoids were a common component of shallow carbonate environments of North America, Eurasia, and Australia during the Devonian. They were least abundant during the Early Devonian. After that time abundance increased, and remained high steadily through the Frasnian. At the Frasnian-Famennian boundary the number of stromatoporoids was greatly diminished, but they did not become extinct until the end of the Devonian (at the end of the Strunian). The geographic extent of stromatoporoids expanded and contracted concurrently with increases and decreases in total population size. Provincialism at the genus level prevailed during the Early Devonian, with stromatoporoids inhabiting the Old World and Eastern Americas Realms; none are known from the Eastern Americas during the Siegenian. For the remainder of the Devonian stromatoporoids were cosmopolitan at the genus level. The abundance of stromatoporoids varied directly with eustatic sea level during the Devonian. Variations in depositional conditions apparently controlled the local distribution of genera.
Early and Middle Devonian gastropod biogeography
Authors: Blodgett R. B. , Rohr D. M. , Boucot A. J.
Published: April 2008

Early and Middle Devonian gastropods show biogeographic patterns remarkably similar to those of better studied faunal groups of this same interval, notably articulate brachiopods, rugose corals, and trilobites. Three biogeographic realms are recognized: Old World, Eastern Americas, and Malvinokaffric Realms. Gastropod diversity is highest in the Old World Realm and lowest in the Malvinokaffric Realm. The diversity patterns and the high degree of shell ornamentation suggest that the Old World Realm was generally warmer than the Eastern Americas Realm, and that both were considerably warmer than the cool temperate to cold polar waters of the Malvinokaffric Realm. The utility of gastropods for fine-scale delineation of biogeographic units is illustrated for the Eifelian of western North America. At least two subprovincial units (the Alaska-Yukon and Nevada subprovinces) can be recognized. Eifelian gastropods from interior and southeastern Alaska belong to a single unit (the Alaska-Yukon Subprovince), and are most closely related to coeval faunas of northwestern Canada, suggesting little displacement of most of Alaska's so-called 'suspect' terranes. Plotting the data on the Devonian palaeogeographic maps of Scotese results in several suggested emendations: (1) North America should be moved south by 10-20°; (2) Australia is too far south on the Emsian and Givetian reconstructions, it should be in a more palaeotropical position; and (3) Siberia is too far north, it too should also be placed in a palaeotropical position.
Givetian-Frasnian phytogeography of Euramerica and western Gondwana based on miospore distribution
Authors: Streel Maurice , Fairon-Demaret Muriel , Loboziak Stanislas
Published: April 2008

The Givetian and Frasnian miospore distributions in western Gondwana and southern Euramerica show a rather uniform vegetation prevailing from palaeo-polar to palaeo-tropical regions. Similar climatic conditions are certainly required to explain this but it is concluded from a discussion on the dispersal of homosporous vegetation that no wide oceans separated these regions at the time. Frasnian northern Euramerica vegetation seems different and might correspond to an equatorial belt. Heckel & Witzke's palaeogeographical reconstruction fits much better with the miospore distribution than other maps.
The Balkhash-Mongolia-Okhotsk region of the Old World Realm (Devonian)
Authors: Hou Hong-Fei , Boucot A. J.
Published: April 2008

Reconsideration of the Emsian brachiopods from parts of central Asia extending from the Lake Balkhash Region easterly through Heilungjiang leads us to conclude that they should be separated as a distinct region, termed the Balkhash--Mongolia--Okhotsk Region, of the Old World Realm. This conclusion was arrived at after considering the high level of endemic genera, plus the significant admixture of genera common with the Eastern Americas and Tasman Realms.
Reconstruction of the Laurasian and Gondwanan segments of Permian Pangaea
Authors: Lottes Ann L. , Rowley David B.
Published: April 2008

A reappraisal of the geological and geometrical constraints on the fits of the continents around the Atlantic, Indian and circum-Antarctic oceans is used as a base upon which to re-examine Early and Late Permian palaeomagnetic data. The palaeomagnetic poles from each of the three main Late Palaeozoic palaeo-continents: Eurasia, North America, and Gondwana define statistically well determined means for the Early and Late Permian. When these poles are reconstructed, the means, and their associated A
95
cones of confidence do not superimpose. The lack of superposition of Late Palaeozoic palaeomagnetic poles on Wegener-style Pangaea reconstructions based on Mesozoic and younger seafloor spreading geometries has been noted for some time. Most solutions to this problem have involved alternative 'tight fits' of the Pangaean continents for the Late Palaeozoic. Solutions invoking the non-dipole behaviour of the magnetic field have also been proposed. We examine the geometric consequences of the 'tight fit' Mesozoic-based Pangaean reconstructions that allow better fit of the palaeomagnetic data and conclude that the magnitudes of overlap (650-950 km) required by these modifications are not compatible with the geological and tectonic evidence from these regions. We prefer to use a 'looser' Pangaea fit that does not necessarily result in the superposition of palaeomagnetic poles. However, when the individual poles from Europe, North America, and Gondwana are combined into a global mean pole, it is observed that both the 'tight' and the 'loose' fit yield virtually indistinguishable mean pole positions. Considering the strong geological and geometrical arguments against the palaeomagnetically derived fits and the lack of a clear statistical difference between the two we use our revised Pangaean reconstruction to determine palaeo-latitudinal framework of the Eurasian, North American, and Gondwanan segments of Pangaea for the Early and Late Permian. The validity of these palaeo-latitudinal reconstructions is tested with climatically sensitive floristic and lithological data by Ziegler, and found to be satisfactory.
Devonian palaeogeography and palaeobiogeography of the Central Andes
Authors: Isaacson P. E. , Sablock P. E.
Published: April 2008

During Devonian time, western Gondwana (northern Chile, Bolivia, and Peru) witnessed a period of thick clastic rock deposition. The sialic Arequipa Massif, apparently a stable terrane since Precambrian time, supplied the bulk of the Bolivian intracratonic basinal sediments. Late Ordovician orogeny in northern Chile-northwestern Argentina included the emplacement of the Puna magmatic arc, with attendant plutonism. The resulting highland supplied coarsegrained sediments to northern Chile. Late Devonian(?) orogenesis deformed Early to Middle Devonian rocks in northern to central Peru. It is suggested that mid-Palaeozoic convergence was 'buffered' by the Arequipa Massif, giving little evidence of orogeny in the Bolivian Devonian-Carboniferous sequence. A highly endemic (Malvinokaffric) shelly fauna, indicative of high palaeolatitudes, occupied the region in Early Devonian (Emsian) time, while allochthonous (Eastern Americas Realm) faunas entered southern Peru. During Middle Devonian time a much lower diversity 'post-Malvinokaffric' fauna (consisting of the brachiopods
Tropidoleptus, Globithyris
, and other taxa) arrived, although a Malvinokaffric stock remained. These taxa arrived via the Amazonas and other eastern basins during a rotation of the region to lower latitudes and presumably warmer waters in Middle Devonian time.
25 years of UK North Sea exploration
Authors: Bowen J. M.
Published: April 2008

Any attempt to summarize 25 years of exploration for petroleum in the UK sector of the North Sea must be a daunting task. The outcome, in terms of the oil and gas fields discovered, is the subject of this volume. This introduction will attempt to outline, very briefly, some of the ups and downs of the exploration history which has led the industry to where it stands today, 25 years on (Fig. 1).

When the author was at university in the early 1950s the very idea the the United Kingdom would be likely to become a significant, let alone major world producer of petroleum would have been viewed as utterly ridiculous

It is true that oil and gas indications had been encountered in wells and mines in such disparate areas as sussex, the west Midlands and the Midland Valley of Scotland and as seepages in Dorset, Lancashire and West Lothian, but these had been thoroughly investigated without the discovery of any economically significant oil or gas fields. Indeed, the only economic production at that time came from BP's small east Midlands fields based on Eakring where the first discovery had been made in 1939

The first Serious attempt to explore for oil in the United Kingdom was initiated in 1918 for strategic reasons, when 11 relatively shallow wells were drilled on anticlinal features in various parts of the country. of these only one, Hardstoft-1 in Derbyshire, discovered producible oil, but attempts to follow up the discovery were unsuccessful.

Exploration then
The Alwyn North Field, Blocks 3/9a, 3/4a, UK North Sea
Authors: Inglis I. , Gerard J.
Published: April 2008

Abstract: Situated in the southeastern part of the East Shetland Basin, the Alwyn North Field produces oil and gas from Brent Group reservoirs and gas and condensate from the Statfjord Formation. The structural style is of tilted and eroded fault blocks dipping to the west and aligned north-south conforming to the principal normal fault trend. NE-SW cross elements further separate the hydrocarbon accumulations. The hydrocarbon columns are restricted to the Tarbert and upper part of the Ness Formation of the Brent Group, in sediments associated with the retreat of the Brent delta. The Statfjord Formation was deposited in an alluvial, fan-delta setting with increasing marine influence towards the top of the formation.
The Cormorant Field, Blocks 211/21a, 211/26a, UK North Sea
Authors: Taylor D. J. , Dietvorst J. P. A.
Published: April 2008

The Cormorant Oilfield is located approximately 150 km northeast of the Shetland Islands in Blocks 211/2la and 211/ 26a of the UK sector of the North Sea, in water depths of 500-550 ft. The field was discovered in 1972 by exploration well 211/ 26-1 and consists of four discrete accumulations spread along a major, north-south trending fault terrace. Hydrocarbons are produced from Middle Jurassic (Bajocian) sands of the Brent Group, which was deposited in a wave-dominated delta system. The reservoir has a typical gross thickness of 250-300 ft, locally increasing to 550 ft over faults active during sedimentation. Reservoir porosity varies from 16-28%, with average permeabilities ranging from tens of md to 1300md. The accumulation contains under-saturated 34-36° API oil which was initially overpressured by some 1000-1270 psi. The stock tank oil initially in place and ultimate recovery are estimated at 1568 MMBBL and 623 MMBBL, respectively, reflecting a recovery factor of 39%. The reserves are produced through crestally-located wells supported by down-dip water injectors, and exported via two fixed platforms and an underwater manifold centre. To date, 59 wells have been drilled and 324 MMBBL (52%) of the estimated reserves have been produced.
The Arbroath and Montrose Fields, Blocks 22/17, 18, UK North Sea
Authors: Crawford R. , Littlefair R. W. , Affleck L. G.
Published: April 2008

The Arbroath Field was discovered by the Amoco operated group comprising Amoco (UK) Exploration Company, Gas Council (Exploration), Amerada Hess Ltd and Texas Eastern (UK) Ltd with the 22/18-1 well in May 1969 and was the first commercial oil field to be discovered in any sector of the northern North Sea. Two years later in 1971, the adjacent Montrose Field was discovered. Both Arbroath and Montrose are located 130 miles east of Aberdeen towards the northern end of the Central Graben area. The two fields have simple non-faulted, anticlinal structures separated by a structural saddle with only 15 ft of relief. The structures are a product of Alpine tectonism combined with differential compaction of the reservoir section. The hydrocarbons have a Kimmeridge Clay source and occur wholly within the Forties Sandstone interval. The oil is trapped by mudstones of the Sele Formation. The reservoir sandstones were deposited in a prograding submarine fan complex and have maintained an average porosity of 23% and a permeability of 80 md.

To date only the Montrose Field has been produced. The main recovery mechanism is natural bottom water drive supplemented by water injection. First oil was produced in 1976 via a tanker mooring system, replaced by a dedicated pipeline in 1984. The Arbroath Field is under development and first oil was produced in April 1990.
The Argyll, Duncan and Innes Fields, Block 30/24 and 30/25a, UK North Sea
Authors: Robson D.
Published: April 2008

abstract

The Argyll, Duncan and Innes Fields are situated in the UK Central Graben in Blocks 30/24 and 30/25a. They produce oil from Devonian, Rotliegendes, Zechstein and Jurassic reservoirs through a common floating production facility, the Deepsea Pioneer.

Argyll was the first UK North Sea oil field to come on stream, with first oil produced in June 1975. Duncan and Innes were added later and the estimated STOIIP for the three fields is approximately 270 MMBBL. To date over 90 MMBBL have been recovered, and the fields are now on decline.