bluuebunny/crossref_metadata_2025 huggingface dataset:
An example of the use of crosshole tomography in dam wall foundation studies
Authors: Cartmell S. J. , Conn P. J. , Pugh T. D.
Published: April 2008

Understanding the material properties upon which a man-made structure is to stand is essential to ensure its post-construction stability. The method of imaging of the rock mass between boreholes by crosshole seismology is a well established
in situ
test utilized in many civil engineering site investigations. A case history is presented from a site investigation for a hydro-electric dam project in the Lesotho Highlands of Southern Africa.

Ten boreholes were drilled along the line of a proposed dam wall, to determine rock properties within the wall foundation. Uphole seismic and wireline logging techniques were used to determine seismic velocity and the dynamic elastic properties within the vicinity of the boreholes. Crosshole shooting and first arrival picking of both Compressional (P) and Shear (5) waves was used to determine the average dynamic elastic rock properties within the inter-borehole mass. Tomographic processing derived velocity information within cells with horizontal and vertical dimensions of 5 and 2.5 m respectively.

Dynamic elastic properties were calculated for individual cells using smoothed density values and velocity data from tomographic processing. Contouring of these values indicated trends in dynamic moduli between boreholes, a technique that allowed identification and location of anomalous zones.
High-definition seismic for Channel Tunnel marine route
Authors: Arthur J. C. R. , Phillips G. , McCormick C. R.
Published: April 2008

The sub-seabed investigations for the Channel Tunnel in 1986–1988 included major marine geophysical surveys as well as 11 deep boreholes in which geophysical techniques were also employed. This was the first time that the significant advances in geophysical techniques which had occurred during the 1970s were applied to a major civil engineering project.

High-resolution multi-trace seismic data was obtained to a greater accuracy and resolution than had been possible during previous studies by means of multi-trace digital techniques. These provided a channel-wide assessment of the tunnelling environment, specifically within the proposed tunnelling medium of the Chalk Marl of the Lower Chalk to a depth of 150 metres below sea bed. Deeper seismic acquisition techniques were used to investigate the sub-tunnel structure to about 800 metres below sea bed to assist with seismic risk evaluation.

The field investigations were complemented by a number of in-depth reviews carried out by a joint Anglo-French team of specialists drawn from the Bureau de Recherches Geologique et Minieres (BRGM) and Mott, Hay and Anderson (MHA). J Arthur & Associates were appointed as specialist sub- consultants to MHA to specify and supervise the engineering geophysical studies and assist with the data interpretation.
The use of ultrasonics to monitor long-term creep tests of salt rock samples
Authors: Guillaume S. , du Mouza J. , Brulhet J.
Published: April 2008

Over recent years, much attention has been focused on the geomechanical properties of salt rocks (halites) from the Bressan Basin, France. This paper presents the results of studies of the textural evolution of salt rocks during creep tests. Four samples were tested under various thermal and mechanical stresses, ranging from 25° to 70°C and under varying isotropic (2 to 5 MPa) and deviator stresses (5 to 20 MPa), in order to reproduce
in situ
conditions. A special experimental biaxial cell was set up in order to stress the samples in such conditions, and ultrasonics was used to monitor changes in rock texture and other properties and to control the experiments. Four tests were carried out on the two main facies of the halite of the Bressian Basin (France), each covering a threemonth period. All the ultrasonic parameters (velocity, attenuation, amplitude) proved to be sensitive to thermo-mechanical conditions. Their variations are functions of the rock type and the imposed stresses. The main result is that damage of the samples could be precisely determined. The limit between dilatant and non-dilatant creep is determined in terms of deviatoric stress. This limit depends on temperature and facies.
Seismic refraction in relation to geotechnical information for (road) construction contracts
Authors: Stewart I. E. , Williams J. R. , Walker C. S.
Published: April 2008

The Roads and Traffic Authority of NSW (RTA) (Australia) has developed a high standard of practice in collecting, interpreting and documenting geotechnical information for road construction contracts. In particular high standards have been developed for seismic refraction information and its integration into overall geotechnical information in relation to detailed design, documentation for contract tendering, road construction and its possible use in evaluating contract claims. It is important to treat the seismic information as an independent source of data for an overall geological model that is developed for the site. This model is derived from sources such as geological mapping and surface observations, drilling, pitting and geophysics. Use of this approach has been critical in achieving substantial reductions is cost overruns attributable to geotechnical conditions. The simplistic approach of comparing bulk property information from geophysics with the specific point information from drilling or test pits, and ascribing differences to erroneous geophysical interpretation, or adjusting the geophysics to agree with the drilling can lead to errors in the geological model. This in turn can lead to costly errors in tendering and in construction planning and often to protracted contractual claims.
A new standard in the practice of engineering seismic refraction
Authors: Walker C. S. , Win M. A.
Published: April 2008

Seismic refraction is applied routinely to all stages of highway engineering projects in Australia and is particularly useful for investigation, design and contract documentation of road cuttings. The Roads and Traffic Authority of NSW (Australia) has developed a new standard of practice in seismic refraction since the late 1980s. The most significant advance has been to reduce shot spacing. This means that high levels of reversed coverage of all refractors and high levels of data redundancy are achieved, ensuring a well controlled interpretation with much reduced ambiguity. Other important advances are more efficient and rigorous equipment and field procedures, greater attention to data quality, PC based interpretation and improvements in reporting and documentation. The seismic information is now an important component, together with geological information, in the development of a geological model of a site. Previously, particularly in complex weathered and fractured terrains, the seismic information was not regarded as reliable enough for this purpose. The result of these advances is that seismic refraction surveys cost the same or less per km as ten years ago but produce more detailed and reliable information. The benefits are better information for design, more reliable information for construction tendering and reduced incidence and cost of contractual claims. This paper discusses in detail the new standard in seismic refraction practice and presents a field example.
Modern geophysics in engineering geology: an overview
Authors: Eddleston M. , McCann D. M. , Cripps J. C. , Johnson P.
Published: April 2008

The 30th Annual Conference of the Engineering Group (September 1994) of the Geological Society was structured to reflect the application of modern geophysical methods in current engineering geology practice.

This paper aims to highlight some of the important points raised during the discussions at the conference. It is based on transcripts of the discussion sessions, but it is not intended to be a verbatim reproduction of all the points raised, rather it concentrates on key themes that were discussed at length. The direct points raised on particular papers have been addressed and amended by the proceedings editors and authors and are not repeated in detail here. The authors apologise to those delegates whose points may have been poorly represented, misrepresented or omitted. The aim is to take an overview of the major conference discussion themes and bring together material addressed by different speakers during different sessions.

The main topics which generated protracted discussions form the subheadings of the paper as follows:

professional status of engineering geologists and geophysicists

geophysical imaging and tomography

investigation of rock masses

accuracy/resolution of various techniques

evaluation of soil/rock stiffness/strength using geophysical methods and sample disturbance effects

presentation of geophysical data in contract documentation

Professional status of engineering geologists and geophysicists

The topic of the professional status of engineering geologists was raised by Professor Atkinson (City University, London, UK) Chair of the Engineering Group of the Geological Society. He noted that while in the UK Chartered Geologists currently work closely
The outlook for rock armour and beach recharge
Authors: Thomas Richard Stephenson
Published: April 2008

Rock armour and beach recharge have been used increasingly over recent years as central elements of coastal defence and other forms of coastal construction. In attempting to define the outlook for rock armour and beach recharge, the context at the coastline, the background to coastal defence, the present need for coastal works and the environmental value of the coast are considered. The advantages of natural materials such as rock, sand and gravel compared with some of the more traditional forms of coastal construction are reviewed. The ‘market’ for rock armour and beach recharge materials, including the legal background and relevant economic factors, is considered and the actual demand for the materials estimated. Important environmental considerations are discussed.
An approach to the abrasion testing of individual pieces of construction materials
Authors: Eden M. A.
Published: April 2008

This paper briefly introduces the basis of abrasion testing and suggests a rapid and simple test that allows the abrasion resistance of specific materials to be evaluated. Small, individual pieces of rock, mortar, or concrete can be tested and the method has been used to evaluate the potential for surface abrasion of concrete surfaces. Many of the commonly used test methods for measuring abrasion resistance of construction materials are aggregate tests such as the QMW mill abrasion test and the ASTM Los Angeles abrasion test which measure the combined resistance of a material to impact and abrasion. Other tests such as the aggregate abrasion and polished stone value tests require a smaller numberof resin mounted aggregate pieces to be studied. The ASTM surface abrasion test for concrete uses physically large flat test pieces. Like the ASTM test, the test method described in this paper measures only the abrasion resistance. However, it provides a means of comparing the abrasion resistance of small pieces of construction material and introduces quartz as a reference material.

The test uses a mixture of oil and carborundum as a grinding medium with 10 mm square test pieces held by a standard load against a rotating steel lapping wheel in a rotating jig. The results are expressed as a ratio of the abrasion rate of the test material to that of quartz tested in the same way. This comparative approach enables the test to be carried out using equipment of various designs.
The economics of contaminated site remediation: decision making and technology selection
Authors: Hardisty Paul E. , Bracken Robert A. , Knight Mark
Published: April 2008

Most activities associated with production of goods and services in modern society are linked directly or indirectly to the production of wastes and pollution. In general, environmental impacts increase with the level of production (as measured by the Gross National Product, or GNP). The decision to remediate a contaminated site can be seen from the macroeconomic and microeconomic viewpoints. Macroeconomics can be used to plan and account for the overall cost of pollution as part of a firm's production, and thus make overall decisions on the real cost of pollution and the level of clean-up that may be called for. Valuation of damaged resources, option values and intrinsic worth is an important part of this process. Once the decision to remediate has been taken, the question becomes how best to remediate. It is safe to say that cost is one of the single most important factors in site clean-up decision making. A basic rule of remediation is often taken to be the maximization of contaminant mass removed for the money spent. However, remediation may also be governed by other objectives and constraints. In some situations, minimization of time, rather than cost, could be the constraint. Evaluation of the economics of a clean-up project is directly linked to the objectives of the site owner, and the constraints within which the remediation is to be performed. Once objectives and constraints have been clearly identified, a range of possible remedial approaches and technologies can be developed, and each option evaluated on a comparative basis. One of the most powerful tools for comparative options analysis is technical-economic analysis. This approach combines evaluation of technical feasibility and effect, with consideration of capital, operation and maintenance costs over a selected time horizon. By constraining remedial alternatives within cost and time boundaries, possible solutions can be evaluated with respect to specific criteria. Two examples illustrate these concepts. Economic analysis of remedial options for containment of a 350 000 1 hydrocarbon spill migrating through fractured rock into a river in Alberta, Canada, provided clear direction to the site owner. Economic analysis of remedial alternatives for contaminated sites in the UK sheds interesting light on the common practice of landfilling, when compared to other alternatives.
Evaluation of inter-organisational sampling trials on contaminated land: comparison of two contrasting sites
Authors: Argyraki A. , Ramsey M. H.
Published: April 2008

The measurement process in environmental studies on contaminated land comprises sampling and analysis with the objective of estimating the values of the analyte concentrations. The estimated mean concentration has a real variation but also a variation due to errors originating from sampling and analysis. Inter-organizational trials, in the form of collaborative trials and proficiency testing, is a well established methodology for the estimation of the analytical uncertainty. However, such trials applied to sampling are in a very early stage of development. The objectives of inter-organisational sampling trials are to reveal discrepancies due to sampling at a particular site, to estimate measurement uncertainty on the estimates of mean metal concentrations at the site and ultimately to improve reproducibility of the participants' results. The very first pilot sampling trial was conducted on a smelter-contaminated site in Derbyshire. The results showed the feasibility of conducting sampling trials and also that errors originating from sampling tend to be much greater than the analytical errors. A second inter-organizational sampling trial was conducted on Hounslow Heath, West London, which is an old landfill site with different contamination characteristics. The results from both trials have shown large discrepancies in estimates of mean metal concentrations in soils by factors up to 2.5 times. The role of heterogeneity of the distribution of the contaminants is a limiting factor when conducting such trials and their usefulness in measuring uncertainty of metal concentration at a particular site has been demonstrated.
The importance of understanding groundwater flow history in assessing present-day groundwater contamination patterns: a case study
Authors: Jones Ian , Davison Ruth M. , Lerner David N.
Published: April 2008

Locating and delineating suspected or known groundwater contamination is often a difficult and costly task. Prior to drilling the first borehole or taking the first sample it is standard practice to undertake a desk study. This is likely to involve investigating the history, geology and hydrogeology of the site. Often, only present-day groundwater flow patterns are used to assess the current situation and plan a site investigation. This paper uses a recent experience to illustrate the importance of understanding the history of groundwater flow in planning a successful and cost-effective groundwater investigation.

The site of an old coal carbonization (coking) plant in the UK East Midlands was selected as a field site to undertake research into coal tar related contamination in sandstone aquifers. From the evidence of previous studies, contamination was known to exist in the aquifer, although its exact location and extent was unknown. A comprehensive desk study, extensive surface geophysics and a solute transport modelling exercise were undertaken prior to doing any drilling. Based on the results of this work a number of monitoring wells were installed and samples taken. Results from these initial wells confirmed the original hypothesis. As more wells were completed it became evident that our understanding was not entirely correct and that the evolution and distribution of the contamination was more complex than the initial investigations indicated.

Ongoing investigations have revealed a complex groundwater flow and contaminant history. This paper intends to illustrate how limited information can be made to fit and ‘prove’ expectations, whereas in reality an entirely different situation may exist.
Characterization of extensive hydrocarbon contamination of an alluvial aquifer, Ploiesti, Romania
Authors: Wallace Stephen , Burgess William , Dottridge Jane , Kim Alexander , Zamfirescu Daniela , Zamfirescu Florian
Published: April 2008

The alluvial aquifer in Ploiesti, Romania, is severely contaminated with hydrocarbons. Petroleum products from four major refineries and 30 km of pipeline affect an area of 37 km
2
, occurring as free product floating on the shallow water table, dissolved hydrocarbon in the groundwater, and residual hydrocarbon in the unsaturated zone. Surveys performed between 1975 and 1995 defined the extent, nature and rapid movement of the contamination at rates up to 100 m a
-1
. Analysis of free product and soil samples showed a complex mixture of crude and refined hydrocarbons, with advanced biodegradation in both phases. Concentrations of non-volatile hydrocarbons in groundwater from the zone surrounding the free product plume were high, averaging 25 mg l
-1
, with dissolved contaminants as far as 6 km down-gradient of the industrial area. Organic and inorganic analyses indicate that biodegradation is occurring. Remediation requires the prevention of further spillages and application of economical and innovative technology. The highly permeable aquifer favours the use of
in situ
remediation, but remedial action is currently limited to a few skimming wells to remove free product.
Sorption of three heterocyclic compounds and their hydrocarbon analogue from coal-tar contaminated water in a natural clayey till
Authors: Broholm Mette M. , Broholm Kim , Arvin Erik
Published: April 2008

The natural attenuation of contaminants in fractured media is controlled by biodegradation and by diffusion into the matrix. The effective rate of diffusion and the mass of contaminants thereby removed from the aqueous phase in the fracture depends on the sorption of the contaminants. The sorption of three heterocyclic compounds and their hydrocarbon analogue from an aqueous solution of a complex mixture of 25 organic coal-tar compounds including all major groups of organic coal-tar compounds in clayey till was studied in batch experiments for a large range of concentrations including concentrations approaching the effective solubility of the mixture and for two different solid:liquid (s:l) ratios. For the high s:l ratio sorption experiment the isotherms were close to linear and best fitted by Freundlich isotherms. Sorption of the four compounds was correlated with
K
ow
, but an order of magnitude greater than predicted from a
K
ow
-
K
ow
relationship for aquifer materials. Sorption was primarily dominated by hydrophobic sorption. However, at high surface density carbazole sorption appeared to be influenced by dipole-dipole attraction. For the low s: 1 ratio experiment at higher concentrations a dramatic increase in sorption was observed for all four compounds. The dramatic increase is likely a result of multi-layer formation/condensation of organic compounds on mineral surfaces at high surface density of organic compounds possibly induced by the complexity of solutes. The steepness of the increase and sensitivity to total compound surface density appears to be related to compound hydrophobicity. The impact of these four compounds on groundwater quality from sources of coal-tar in fractured clayey till overburden may be significantly lower than predicted from general sorption relationships.
On the controls of fluvial hazards in the north Bihar plains, eastern India
Authors: Sinha Rajiv
Published: April 2008

The rivers of the north Bihar plains, eastern India, pose three major fluvial hazards: rapid lateral migration, frequent flooding and extensive bank erosion. Lateral shifting of the Kosi, Gandak and several other rivers in the area has been attributed mainly to neotectonic tilting and subsidence of the area, and to some extent, local topography and sedimentological readjustments in the basin. Overbank flooding is a perennial problem, with most of the rivers of the north Bihar plains causing enormous damage to life and property. The construction of embankments along major portions of the rivers is only a short-term solution to mitigate floods not only because of frequent breaches in the embankment due to extremely high discharges during high flows but also because of the fact that these rivers carry a high sediment load causing rapid siltation and thereby raising the water level in a few years’ time. Severe bank erosion takes place during the lateral shifting of rivers as well as during high flows. Efforts to prevent these fluvial hazards in the area have largely failed as the geological and geomorphological considerations have not been taken into account.
The construction of a drainage tunnel as part of glacial lake hazard mitigation at Hualcán, Cordillera Blanca, Peru
Authors: Reynolds J. M. , Dolecki A. , Portocarrero C.
Published: April 2008

At Hualcán in the Cordillera Blanca is a high-altitude glacier lake dammed by a moraine. Local glaciers regularly produce ice avalanches. In 1988 it was confirmed that the moraine was ice-cored. The rate of melting of the ice was sufficiently fast that, unless mitigation measures had been undertaken rapidly, the moraine would have collapsed. This would have resulted in the inundation downstream of Carhuaz, a town with a population of 25000 people. Following the successful installation of siphons in 1988–89 to reduce the water level by 8 m, it was decided to undertake more permanent engineering works to ensure that the lake could never again pose a threat. It was proposed to construct a 2-m diameter tunnel, 155 m long beneath a rock bar below the moraine dam, to lower the lake level by a further 20 m. This would create sufficient freeboard to contain possible displacement waves.

Work on the tunnel was started in May 1993 using compressed air drilling and blasting with hand excavation. The initial tunnel design consisted of a single tunnel drive 135 m long plus a 20-m inclined drive under the lake. A second, near-vertical shaft was constructed for ventilation and access. Had the proposed method of breakthrough from the tunnel to the lake been carried out, it would have resulted in a rockburst leading to the catastrophic discharge of the lake. The tunnel design was changed on site to include three additional inclined drives from the main shaft, reaching the lake at vertical intervals of 5 m. Using this method, the lake level was lowered 20 m safely.

The objective of this paper is to describe in detail the geotechnical engineering aspects of the tunnel construction, the reasons for the change in its design, and the results of the mitigation work.
Assessing erosion of sandy beaches due to sea-level rise
Authors: Nicholls Robert J.
Published: April 2008

The prospect of accelerated sea-level rise in the coming century makes beach erosion more likely. Given the concentration of human habitation and infrastructure adjacent to sandy beaches, it is prudent to consider the implications of such changes. To select the most appropriate approach to evaluate this problem, three levels of increasingly complex assessment can be distinguished: (1) screening assessment (SA); (2) vulnerability assessment (VA); and (3) planning assessment (PA). SA and VA are amenable to analysis with a Bruun rule-based approach. SA can be quickly and effectively accomplished using a simple proportionality approach that shoreline recession is in the range of 100 to 200 times the sea-level rise scenario. For VA, a range of shoreline response scenarios can be estimated by selecting appropriate low and high offshore boundary conditions. PA ideally requires a comprehensive sediment budget approach. SA may trigger VA, which may in turn, trigger PA, depending on the results. The limitations of this structured approach are discussed.
The distal impact of Icelandic volcanic gases and aerosols in Europe: a review of the 1783 Laki Fissure eruption and environmental vulnerability in the late 20th century
Authors: Grattan John
Published: April 2008

This paper presents detailed documentary evidence for volcanic pollution of the atmosphere over many parts of Europe during the eruption of the Laki Fissure in Iceland during
ad
1783. The environmental impact of this event appears to have been severe, with reports of an acid dry fog in many parts of Europe, and often of associated damage to vegetation. It is argued that the meteorological conditions that led to this event are precisely the same as those which are associated with modern-day air pollution episodes in European conurbations, and the potential addition of millions of tonnes of volcanic gaseous material to the air over already polluted cities poses a rare, but in health terms potentially major, risk.
Lessons from the Kobe earthquake
Authors: Esper Philip , Tachibana Eizaburo
Published: April 2008

The Kobe earthquake is considered to be one of the most devastating and costly natural disasters in recent history considering the number of buildings destroyed, the number of people killed and injured, the size of the affected area, and the extent and severity of damage to a wide range of structural types. As a result, important questions have been raised about earthquake preparedness, disaster response, seismic design and codes of practice, and upgrading of earthquake-resistant structures. This paper presents an overview of this earthquake, investigates the extent and types of damage caused, studies the factors behind each type of damage, and highlights important lessons learnt from this earthquake. Protective measures and future research that should be undertaken in Japan, and all countries that are at seismic risk, are recommended in order to reduce damage and casualties in future seismic events.
Use of landslide inventory data to define the spatial location of landslide sites, South Wales, UK
Authors: Jennings P. J. , Siddle H. J.
Published: April 2008

This paper presents and analyses the findings of a landslide inventory survey undertaken in deeply dissected upland valleys in layered Carboniferous lithology, Rhondda Valleys, South Wales. This area has one of the highest recorded concentrations of landslides in the UK.

The paper analyses the terrain factors identified at landslide sites (lithology, slope angle, geographical setting) with factors denning the landslide (such as type/depth of movement, age, activity, material, areal extent, geometry). Using these data, a composite profile of probable landslide sites is developed. This provides a valuable tool in further quantifying likely landslide hazard at sites, giving an indication of the potential of, for example, first-time failures or whether degraded relict landslides may be present.

Discussion is provided on the findings, particularly landslide locations within the valley and their age and current state of activity.
The role of engineering geology in the hazard zonation of a Malaysian highway
Authors: Cook J. R. , McGown A. , Hurley G. , Choy Lee Eng
Published: April 2008

The University of Strathclyde and the Institut Kerja Raya Malaysia (Public Works Institute) have undertaken a joint research project into the investigation, description, classification and geotechnical analysis of tropically weathered in situ materials (TWIMs) in Malaysia in general and on a major highway in particular. The research project has developed a general approach to TWIM profile characterization and classification which allows specific systems to be developed to deal with particular project requirements.

A key part of the research is to provide practical engineering geological and geotechnical advice to a hazard identification and risk assessment project on the 113 km long East-West Highway in Kelantan, northern Peninsular Malaysia. This highway has an ongoing history of persistant slope failure and contains a large number of significant earthworks in generlly mountainous terrain underlain by a ange of tropically weathered bedrocks including sedimentary, meta-sedimentary and igneous materials. The 3-year long-term project produced hazard maps for the earthworks along the highway. These maps provided a more scientific basis for cost-effective planning and design of maintenance and preventative remedial works along the highway.

This paper outlines the main elements of the project and indicates the key influence that the engineering geological character of the tropically weahered soil-rock profiles has had on the assessment of slope hazard.
Development advice maps: mining subsidence
Authors: Scott M. J. , Statham I.
Published: April 2008

In 1985 the Department of the Environment/Welsh Office commissioned the ’South Wales Desk Study - Mining Subsidence’. This project was to develop a method for preparing Development Advice Maps giving advice to planners and developers on abandoned shallow mining. The pilot area for this study was centred in Ebbw Vale and supplemented by a detailed review of mining subsidence throughout the whole of South Wales. Subsequent to this study a follow on project was undertaken in 1991 in the Borough of Islwyn. The purpose of the study was to confirm the methodology developed during the first study and produce Development Advice Maps which could be introduced into the planning process at Islwyn Borough Council. Maps were introduced into the planning system with planning guidelines and were monitored for 15 months. The monitoring period has indicated that the Development Advice Maps, drafted in accordance with the procedure developed from the South Wales Mining Desk Study, are generally reliable.

This paper discusses the method of preparation of Development Advice Maps in South Wales and proposes a strategy of risk management with which to appraise potential mining subsidence.
Gondwana's movement over the South Pole during the Palaeozoic: evidence from lithological indicators of climate
Authors: Scotese R. Christopher , Barrett Stephen F.
Published: April 2008

A statistical technique is described that uses the geographical distribution of lithological indicators of climate (carbonates, evaporites, coals and tillites) to estimate the past position of the geographic pole. This technique was used to estimate the movement of the South Pole across the supercontinent of Gondwana during the Palaeozoic. Our results indicate that during the Cambrian and Early Ordovician the South Pole was located adjacent to northwestern Africa. The pole moved into the Amazon Basin during the Late Ordovician and into south-central Argentina during the Silurian. Throughout the Devonian and Early Carboniferous the pole moved slowly from a location in southern Argentina to a position near the south coast of Africa. From the Late Carboniferous and into the Permian the South Pole swung eastward across central Antarctica. The Early Palaeozoic and Late Palaeozoic portions of the palaeoclimatically determined APW path are in good agreement with available palaeomagnetic data. The Middle Palaeozoic portion of the palaeoclimatically determined APW path agrees better with the palaeomagnetic data that places the South Pole in southern Argentina, than with the palaeomagnetic results that place the Devonian pole in central Africa.
Graptolite biogeography: implications for palaeogeography and palaeoceanography
Authors: Berry W. B. N. , Wilde P.
Published: April 2008

Two faunal regions, a cool-water, Atlantic and a tropical-water, Pacific, may be distinguished among Tremadoc into Ashgill planktic graptolite faunas. The zenith of graptolite provincialism was during the Arenig-Llanvirn when Laurentia, Australia-New Zealand, North China, South China, Siberia, Argentine Precordillera, and parts of Kazachkstan were provinces within the Pacific Region. Coeval, Southern Hemisphere, Atlantic Region provinces were: England-Wales, Baltoscania, Bolivia-Peru-Northern Argentina, western Europe, North Africa, and possibly part of modern Tien Shan. South China Arenig-Llanvirn faunas include many incursions of Atlantic Region taxa, probably reflective of current circulation changes linked to development of seasonal monsoons. Mid-Ordovician plate motion included northward movement of Baltoscania into the tropics. That motion resulted in Baltoscania becoming a province in the Pacific Region in the Late Ordovician. Late Ordovician glaciation led to restriction of graptolites to the tropics (Pacific Region) during the latest Ordovician. Deglaciation was followed by re-establishment of a tropical, Pacific Region fauna and a cool-water, Atlantic Region fauna during the Llandovery and Wenlock. Graptolite faunas appear to have been only tropical from the Ludlow to their extinction in the Pragian (Early Devonian). The graptolite regions and provinces are essentially consistent with plate positions suggested by palaeomagnetic and lithofacies data.
Graptolite biogeography: recent, future hopes
Authors: Rickards Barrie B. , Rigby Susan , Harris Jonathan H.
Published: April 2008

Recent progress in the plotting of biogeographical distributions is shown to be partly due to improved base maps, some of the notable anomalies detected by earlier workers being explained and easily accommodated in the latest maps. Progress is also in part due to increasingly precise systematics, which results in more accurate biostratigraphical correlation: examples include the
'Didymograptus' bifidus
controversy and its role in the definition of the Pacific and Atlantic provinces of the Arenig-Llanvirn. Analogy with modern planktonic regimes enables recognition of marker species in specific water masses; and in the distinction of neritic from open ocean plankton. Analysis at species level and lower of Wenlock graptolite assemblages has resulted in the recognition of the Rheic and Mediterranean subprovinces within a Pacific province or realm. Hydrodynamic modelling suggests directions for future research which may provide independent support for biogeographical studies.
Brachiopod zoogeography across the Ordovician-Silurian extinction event
Authors: Sheeman P. M. , Coorough P. J.
Published: April 2008

The Extinction event at the close of the Ordovician, one of the largest of the Phanerozoic, had a profound effect on the zoogeographic distribution of brachiopods. Strong endemism in the Ashgill was particularly apparent in the epicontinental seas covering the primary lithospheric plates. Areas in the open ocean and around the margins of the continents had more widely distributed faunas. Glacio-eustatic decline in sea level and climatic deterioration caused by the developing North African glaciation have been widely invoked as the cause of the extinction event. The Hirnantian Stage roughly corresponds to the glacial maximum, and Hirnantian faunas were somewhat more cosmopolitan than were early-middle Ashgill faunas. At the end of the Hirnatian, sea level rise and climatic amelioration accompanying the end of the glacial maximum apparently caused another wave of extinctions. Early Silurian brachiopods were far more cosmopolitan, especially in the epicontinental seas, than they had been in the Late Ordovician. There is a strong correlation between wide geographic distribution of genera and survival of the extinction event. Provincial patterns are consistent with the symposium maps.
Distributions and extinctions of Silurian Bryozoa
Authors: Tuckey M. E.
Published: April 2008

Gradient and cluster analyses of bryozoan genera, from a worldwide bryozoan data base has revealed biogeographic patterns for the Silurian. In the Llandovery, three provinces can be distinguished: (1) a north American-Siberian Province; (2) a Baltic Province; and (3) a Mongolian Province, which includes localities on the Siberian and South China plates.

During the Wenlock, the North American-Siberian and Baltic Provinces merged into a single province as the Iapetus Ocean continued to close, with the Mongolian Province still present. A single cosmopolitan province developed during the Ludlow, and little biogeographic differentiation can be observed among Ludlow and Pridoli faunas. Formation of the Mongolian Province may be related to latitudinal climatic zonation, as the northern portion of the Siberian plate had moved into temperate latitudes in the Early Silurian. Loss of the north temperate Mongolian Province in the Ludlow, suggests that the Siberian plate may have moved southward in the Late Silurian.

Increases in extinctions of bryozoan species and genera coincided with loss of provinciality in the Silurian. Merging of the Baltic and North American-Siberian Provinces in the Wenlock coincided with large increases in extinctions in North America and Baltica. Wenlock extinctions may be related to climatic change caused by continental convergence, or competition between faunas. Loss of the Mongolian Province in the Ludlow also coincided with increases in extinctions, which may be related to southward movement of the Siberian plate into a warmer climatic zone.
Biogeography of Silurian stromatoporoids
Authors: Nestor Heldur
Published: April 2008

Stromatoporoids were widespread in the Ordovician, Silurian and Devonian shallow seas with carbonate types of sedimentation. Their occurrences in reefs and association with bahamitic type carbonate sediments, sometimes replaced by evaporites, allow them to be considered as stenothermal warm-water organisms which lived in the tropical to subtropical climatic belt between 40° N and S. The rapid eustatic deepening after the latest Ordovician glaciation gave rise to ecological stress in the shallow-water stromatoporoids and suppressed their adaptive radiation. Therefore a taxonomically monotonous cosmopolitan fauna of stromatoporoids formed at the beginning of the Llandovery. Few endemic genera existed during the late Llandovery and Wenlock. In Ludlow time a low degree of provincialism appeared when differences developed between the European and Asiatic faunas; these vanished again in the Pridoli. The data on stromatoporoid distribution are in good agreement with the current palaeogeographical reconstructions.
Biogeography of Devonian Algae
Authors: Poncet J.
Published: April 2008

Most of the Devonian calcareous algae are distributed in the Palaeotethyan Realm on carbonate platforms located around the Palaeotethys Ocean. Possible connections by hypothetical palaeocurrents between the different palaeobiogeographical areas have been reported. Palaeogeographic Devonian reconstructions are tested using the latitudinal constraints due to the ecology of calcareous algae.
Biogeography of Lower Carboniferous crinoids
Authors: Lane N. Gary , Sevastopulo G. D.
Published: April 2008

The stratigraphic are ranges of all known crinoid genera of Mississippian and Lower Carboniferous age in western Europe and North America compared. Camerate crinoid distribution was published in 1987 (Lane and Sevastopulo). Inadunate and flexible crinoid ranges are presented here. A total of 197 genera are involved, 157 in North America and 93 in Europe, with 53 joint occurrences. Conspicuous endemism occurs at both the familial and generic levels in both Europe and North America. In early Mississippian time camerate crinoid genera are especially endemic in North America and many become extinct. In later Mississippian time many poteriocrinoid and flexible crinoid genera and some families are confined to either North America or Europe. Both environmental and physical barriers contributed to isolation and endemism. Genera tend to originate first, and become extinct first, at about equal rates in North America and in Europe. European genera tend to be somewhat longer ranging than North American genera, perhaps due to differences in breadth of definition on the two continents. Primitive groups like disparid and cyathocrinoid inadunates range up from the Late Devonian. Advanced poteriocrinoid inadunates commonly range up into younger Pennsylvanian-Upper Carboniferous rocks. New families originated in both North America and western Europe with about equal frequency. New Japanese occurrences of Pennsylvanian inadunates and the age relations of Permian Timor crinoids are discussed briefly.
The North Brae Field, Block 16/7a, UK North Sea
Authors: Stephenson Mark A.
Published: April 2008

North Brae is the first gas condensate field in the UK to be produced by gas recycling. The field lies at the western margin of the South Viking Graben in UK Block 16/7a. Estimated recoverable reserves are 178 MMBBL of condensate and 798 BCF of dry gas. First hydrocarbon production was in April 1988 from the Brae 'B' platform.

The reservoir is composed of coarse clastic sediments of the Upper Jurassic Brae Formation which were deposited by debris flows and turbidity currents in a submarine fan setting adjacent to an active fault scarp. The Brae Formation now abuts impermeable Devonian rocks of the Fladen Ground Spur to the west. The reservoir is capped by the Kimmeridge Clay Formation, which also provided the source of the hydrocarbons.
The Central Brae Field, Block 16/7a, UK North Sea
Authors: Turner Colin C. , Allen Philip J.
Published: April 2008

Central Brae Oilfield is the smallest of three Upper Jurassic fields being developed in UK Block 16/7a. The field was discovered in 1976 and commenced production in September 1989 through a subsea template tied back to the Brae 'A' platform in the South Brae Oilfield. Recoverable reserves are estimated as 65 MMBBL of oil and 6 MMBBL of NGL. The Central Brae reservoir is a proximal submarine fan sequence, comprising dominantly sand-matrix conglomerate and sandstone with minor mudstone units. The sediments were shed eastwards off the Fladen Ground Spur and were deposited as a relatively small and steep sedimentary cone at the margin of the South Viking Graben. Mudstone facies border the submarine fan deposits to the north and south, forming stratigraphic seals. The structure is a faulted anticline developed during the latest Jurassic and early Cretaceous possibly in response to large-scale rotational slump movement within the easterly-dipping graben margin sequence. The western boundary of the field is formed by a sealing fault, whilst to the east, there is an oil-water contact at 13 426 ft TVSS. The overlying seal is the Kimmeridge Clay Formation, which also interdigitates with the coarser facies basinwards, and provides the source of the hydrocarbons.
The Deveron Field, Block 211/18a, UK North Sea
Authors: Williams R. R.
Published: April 2008

The Deveron Field lies to the west of the Thistle structure and is a satellite development to the main Thistle Field. It holds separate field status but utilizes Thistle platform facilities. Although Deveron has a similar structural framework and stratigraphic sequence to the Thistle Field, subtle differences in reservoir character and behaviour are evident. The field was discovered by the first well on Block 211/18 but its small size prevented development until installation of the Thistle production facilities. The Deveron appraisal and development wells have all been drilled from the Thistle platform and so far no injection has been required. The current STOIIP is estimated at 41 MMBBL of which 20 MMBBL will ultimately be recovered. Cumulative production to the end of 1988 was 9.96 MMBBL from 3 production wells.
The Dunlin Field, Blocks 211/23a and 211/24a, UK North Sea
Authors: Baumann A. , O'Cathain B.
Published: April 2008

The Dunlin Oilfield is located in the East Shetland Basin, 160 km northeast of the Shetland Islands. It lies in UK Blocks 211/23a and 211/24a in about 500 ft of water. The field was discovered in June 1973 by well 211/23-1. The oil accumulation is trapped, in a north-south oriented, tilted fault block at the western margin of the Viking Graben, at a depth of about 8500 ft TVSS. The reservoir is contained in the formations of the Middle Jurassic Brent Group. In the Dunlin area they form a 450 ft thick sequence of sands and intercalated minor shales, which has been deposited by a shore face and delta system prograding northwards across the Viking Graben. The seal is formed by the shales of the Middle/Upper Jurassic Heather Formation. Reservoir properties of the Brent sands are fair to good with porosities of up to 30% and average permeabilities in the range from 10 to 4000 md. Development of the field is carried out from a single platform, from which production started in 1978. To date 40 development wells have been drilled and the total cumulative production amounts to 282 MMBBL of an ultimate recovery of 363 MMBBL.
The Frigg Field, Block 10/1 UK North Sea and 25/1, Norwegian North Sea
Authors: BREWSTER J.
Published: April 2008

The Frigg Field was the first giant gas field to be discovered in the northern North Sea. Its position on the boundary line between the UK and Norway called for international cooperation at an early stage in development. The Lower Eocene reservoir sands have extremely good poroperm characteristics but the heterogeneities within the sands control the water influx from the immense Eocene and Palaeocene aquifers below.