bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterizing petroleum charge systems in the tertiary of SE Asia
Authors: Todd S. P. , Dunn M. E. , Barwise A. J. G.
Published: April 2008

Most SE Asian Tertiary-aged petroleum has been derived from paralic (lower delta plain to prodelta, higher land plant dominated) source rocks, although the larger proportion of
oil
is from lacustrine (freshwater/brackish algal) sources. Because many SE Asian petroleum provinces have been largely explored without penetrating source rock, the source is inferred from the oil’s geochemistry. Prolific lacustrine sources develop mainly in
rift
lakes in the Palaeogene syn-rift megasequence common to many SE Asian basins, but
floodplain
lake sources are also important. Paralic source rocks include both coals and particularly coaly mudrocks developed within the Miocene post-rift megasequence with an oil-prone zone. Oil-prone source rocks are preferentially developed in the paralic realm between the lower coastal plain and lower estuary/delta front facies, perhaps involving a mangrove system. The stratigraphic position and kinetic expulsion behaviour of different source types, migration, seal timing and pressure-temperature-depth relationships converge to make younger plays, including carbonate buildups, more gas prone. The volumetric significance of biogenic gas is still poorly understood. Vertical migration is common in overpressured SE Asian basins; lateral migration is thus commonly restricted to distances of 20 km or less from the kitchen.
Exploring the lake basins of east and southeast Asia
Authors: Sladen Chris
Published: April 2008

SE Asia contains a large number of late Mesozoic and early Tertiary lake basins, that together contain a significant proportion of the world oil and gas reserves, oil shale reserves, and coal reserves. Exploration and production of oil and gas from these basins is likely to continue throughout the twenty-first century. As exploration for oil and gas continues, and fewer large fields remain to be found, it will become increasingly vital to focus expenditure on low risk, small volume opportunities in a manner that generates a return on investments. To achieve this, there needs to be a much more detailed understanding of lake basins and the sequences that fill them. This has to be combined with innovative technology to reduce well costs and increase flow rates per well, reductions in operating expenditures and greater flexibility in fiscal terms.
The tectonic evolution and associated sedimentation history of Sarawak Basin, eastern Malaysia: a guide for future hydrocarbon exploration
Authors: Mat-Zin I. C. , Swarbrick R. E.
Published: April 2008

A seismic-stratigraphic study of the reprocessed regional lines for the offshore Sarawak area was undertaken with the aim of reviewing the present understanding of the tectonics and the palaeo-depositional environments of the Sarawak Basin. The study was integrated with biostratigraphy and wireline-log data from the wells drilled throughout the basin.

Seven unconformities were identified within the Tertiary sediments and these were used as the markers for the seismic correlations. Where the unconformities become conformable, well data were used to guide the correlation of the conformities. Palaeo-environment maps were generated which document the interaction of tectonics and sediments throughout the basin history. The development of the Sarawak Basin commenced in late Oligocene times with deposition along a coastline running in a NW-SE direction, which is almost perpendicular to the present-day coastline. The coastline was oriented to the present-day NE-SW during late Miocene times.

Geochemistry of Sarawak Basin oils shows generation of hydrocarbons from land plant dominated source rocks. The distribution of these types of source rocks are favoured in the Coastal Fluvial, Coastal and Lower Coastal Plain environments. The quantity and quality of the source rocks deteriorates with the distance from the coastline. The palaeo-environment maps illustrate the likely distribution of Sarawak Basin source rocks which will help in effectively planning for future exploration in Sarawak.

The study also revealed that the Sarawak Basin was formed as a result of NW-SE-trending right-lateral fault movement during late Oligo-Miocene times. This dextral movement was responsible for creating the NW-SE coastline and divided the offshore Sarawak area into two sub-basins. Deposition and preservation of coastal plain and shallow marine sediments continued in the eastern area while the western area remained as a ‘high’ until late Miocene times. The dextral strike-slip movement which controlled the evolution of the Sarawak Basin is sub-parallel to a number of lineaments elsewhere in Sarawak. The timing of movement of these suggests progressive younging in an eastward direction. It is also believed the late structuration of the sediments and the formation of structural traps is linked to these tectonic movements.
A review of the petroleum potential of Papua New Guinea with a focus on the eastern Papuan Basin and the Pale Sandstone as a potential reservoir fairway
Authors: Boult P. J.
Published: April 2008

Substantial oil seeps were first reported from the eastern Papuan Basin in 1911, and oil has since been produced from the sub-surface, but not in commercial quantities. A significant discovery of gas in 1986 sparked an upsurge of activity within the adjacent western Papuan Basin. From 1986 to 1992, 13 new hydrocarbon discoveries were made, which included four major oil fields, and an oil pipeline for export purposes was then opened in 1992. This activity did not spread to the eastern Papuan Basin due to a perceived lack of good reservoir and the last well drilled there was over 30 years ago. In 1986, a potentially excellent reservoir, the Pale (Pah leh) Sandstone was discovered in outcrop in the eastern Papuan Basin. Thus the Papuan Basin as a whole remains an extremely prospective basin. However, due to high infrastructure costs most activity has recently been focussed on the already proven reservoir potential of the Late Jurassic Imburu and Toro Formations in the western section.

The extent of the Imburu-Toro Formation reservoir in the western section of the Papuan Basin is well documented. It was deposited as several regressive episodes within an overall transgressive, passive-margin, clastic sequence. In the eastern section, the Late Cretaceous Pale Sandstone was deposited in a barrier island or strand-plain environment. Lateral equivalents of the Pale Sandstone and the potential for a new reservoir fairway have been documented for a strike length of approximately 400 km. This fairway is coincident with the northeast edge of the western Papuan Basin and on the northern edge of the Aure and Port Moresby Troughs of the eastern Papuan Basin.

All the commercial oil accumulations and seeps found in the Papuan Basin before 1992 have been attributed to the Jurassic, with peak generation occurring in the Late Cretaceous prior to the formation of existing structures. In 1992 an oil seep was discovered which is geochemically very different to all the other oils found in the Papuan Basin. This was found to the north and east of the present discoveries that occur within the western Papuan Basin. The oil seep is indicative of undiscovered Tertiary source rock, which is currently at or near peak generation. However, most of this source rock in the north may be covered by overthrusted allochthonous terrain.

The Aure Trough was a Late Cretaceous to Tertiary rift basin that later developed into an Oligocene to Mid-Miocene foreland basin depocentre occurring on the northern and eastern margin of the Papuan Basin. It is proposed in this paper that mature Tertiary source rocks which occur within this foreland basin and the Pale Sandstone reservoir may form a significant petroleum system on the northeastern rim of the western Papuan Basin and within the eastern Papuan Basin.
Cenozoic deformation in Sumatra: oblique subduction and the development of the Sumatran Fault System
Authors: McCarthy A. J. , Elders C. F.
Published: April 2008

Sumatra is situated at a long-lived active continental margin. At the present day, subduction beneath the margin is strongly oblique, leading to subduction of Indian Oceanic crust at the Sunda Trench and right-lateral strike-slip along the onshore Sumatran Fault System (SFS). A pre-Tertiary history of accretion against the margin was followed by Palaeogene basin formation throughout Sumatra. A strong mid-Miocene inversion event is recorded in the onshore part of the forearc basin in southern Sumatra. The mid-Miocene also marked the inception of seafloor spreading in the Andaman Sea and the probable inception of major strike-slip movement along the SFS, possibly following clockwise rotation of Sumatra towards it present NW-SE trend. The SFS exhibits a wide variety of geometries and deformational styles and is characterised by an extremely complex deformation history including polyphase reactivation of fault surfaces and contemporaneous strike-slip and orthogonal compression or extension. A new estimate of approximately 150 km offset of Mesozoic units across the SFS in central Sumatra is proposed. Several basins have formed along the SFS during the Quaternary. Some of these are not readily explained in terms of classic models of strike-slip basin formation and it is proposed that thermally induced uplift along the axis of the volcanic arc of the Barisan mountains was of primary importance in their formation.
New observations on the sedimentary and tectonic evolution of the Tertiary Kutai Basin, East Kalimantan
Authors: Moss Steve J. , Chambers John , Cloke Ian , Satria Dharma , Ali Jason R. , Baker Simon , Milsom John , Carter Andy
Published: April 2008

The Kutai Basin, Kalimantan, is one of several large Tertiary basins which opened during the mid- to late Eocene in Borneo. Extensional tectonics are responsible for basin formation, and not crustal flexure as has been suggested previously. Extensional faulting did, however, occur within a general foreland setting located to the south of the late Cretaceous/Palaeogene Central Kalimantan fold belt. The basin post-dates late Cretaceous/early Tertiary orogenic activity which affected the Central Kalimantan foldbelt and formed several upper Cretaceous granites. The Palaeogene stratigraphy of the basin includes basal conglomerates, shallow marine clastics and minor clastics and thick sequences of bathyal marine shales. Neogene stratigraphy is dominated by deltaic clastics and carbonate platforms. Several phases of Tertiary igneous activity are seen intruded into and interbedded with Tertiary sediments of the Kutai Basin. Three suites are recognized and have been variously interpreted as the products of melting of an orogenic root, extensional driven melting and/or subduction related melting. We review Tertiary sedimentation in the basin and propose a new model which relates the formation of the Kutai Basin to the opening of Celebes Sea and collapse of an uplifted Late Cretaceous/Palaeogene orogenic belt.
The role of structural geology in reservoir characterization
Authors: Cosgrove J. W.
Published: April 2008

In this brief review of the role of structural geology in reservoir characterization a comparison is made between the original role of structural geology, which focused on the three-dimensional geometry and spatial organization of structures and which involved a statistical treatment of the spatial arrangement of structures such as faults and folds and on static analyses, and the more recent trend in structural geology which is concerned with the dynamics of structure formation and the associated interplay of stress and fluid migration.
Experimental fault sealing: shear band permeability dependency on cataclastic fault gouge characteristics
Authors: Crawford B. R.
Published: April 2008

An experimental rock mechanics facility was used to assess the finite permeability of shear bands artificially induced in cylindrical core plugs of high porosity sandstone under triaxially compressive stress states of varying magnitude. A method of estimating shear band permeability from axial transient pulse-decay measurements is presented, based on certain assumptions including a linear thickness decrease with resolved normal stress across the fault. Computed permeability reductions range from 2.5 to 3.5 orders of magnitude, with cataclastic sealing exhibiting an order of magnitude increase with increasing normal stress and angular shear strain imposed on the gouge zone. A laser particle sizing technique was applied to the experimentally generated fault gouge samples to appraise any differences in their distributions down to 0.1 μm particle size. By defining the peak (relative fineness) and width of distribution (closeness of grading) of each, the Rosin-Rammler exponential function was able to quantify ‘cataclastic intensity’ via a ‘coefficient of variation’ statistical parameter. An empirical relation demonstrated between fault seal and degree of cataclasis is rationalized through consideration of the Kozeny-Carman relation, which analyses permeability in terms of its constituent parameters of tortuosity, porosity and surface area.
Physical character and fluid-flow properties of sandstone-derived fault zones
Authors: Gibson Richard G.
Published: April 2008

Evaluation of hydrocarbon entrapment and production patterns in faulted sandstone reservoirs requires understanding of the nature and fluid-flow properties of sandstone-derived fault zones. This study documents the interrelationships between sandstone composition, deformation mechanisms, fault-zone character, and fluid-flow properties (permeability and capillary properties) using a global sandstone dataset.

Quartz-rich sandstones deform by cataclasis (most commonly), diffusive mass transfer, or a combination of these processes to form deformation bands. The fluid-flow properties of these zones depend on deformation mechanism(s). Faulting of mineralogically immature sandstones results in the formation of clay-matrix gouge zones by a combination of processes, including cataclasis, intergranular sliding in clay-rich materials, and diffusive mass transfer. Clay-matrix gouge zones generally have lower permeabilities and higher capillary displacement pressures than deformation bands.

Most deformation bands have capillary properties sufficient to maintain hydrocarbon column-height differences of less than 75m across them, whereas clay-matrix gouge zones can potentially seal hydrocarbon columns with heights of several hundred metres. Both low-permeability deformation bands and clay-matrix gouge zones are likely to influence production patterns, although the magnitude of these effects will depend on the spatial distribution and abundance of faults and the permeabilities of the fault zones and undeformed sandstone.
Fracture distribution in faulted basement blocks: Gulf of Suez, Egypt
Authors: Younes Amgad I. , Engelder Terry , Bosworth William
Published: April 2008

Fractures in basement rocks of Gebel El Zeit and Esh El Mallaha fault blocks, Egypt, occur in three nearly orthogonal sets: a SE-dipping, cross-rift set that parallels ENE faults and dykes; a SW-dipping set sub-parallel to bedding in overlying clastic rocks; and a NE-dipping, rift-parallel set that parallels the rift-border faults. Restoration to prerift orientations puts these sets into vertical, horizontal and vertical attitudes respectively. All fracture sets are present throughout the fault blocks, except for the horizontal set which is absent on the NE side of Gebel El Zeit and in the Nubia Sandstone. Fracture density increases near the top of basement where sheet fracturing is common, near faults, and in and around dykes. The distribution of similar fracture sets is recorded from sub-surface Formation Micro Scanner and Formation Micro Imager logs in the basement of the Ashrafi Oil-field, southern Gulf of Suez. The similarity of the fracture pattern between Gebel El Zeit and the Ashrafi Field suggests that surface fault blocks can be adequate analogues to the sub-surface blocks.

The intersection of sheet and fault-parallel fractures localizes the maximum fracture density at the edges and near the top of the fault blocks. Block faulting and subsequent depth of erosion govern the distribution of fractures within the blocks. Block rotation during rifting relocated the maximum fracture density at an upper corner or structural crest, whereas block faulting without rotation maintained the maximum fracture density at block edges. In both styles, erosion of an exhumed block removed rocks of high fracture density by eroding the crest in the first case, and by stripping off the sheet fractures in the second. The first style is an analogue for half-graben reservoirs, e.g. the southern Gulf of Suez, while the second style is an analogue for full-graben reservoirs, e.g. the Mekong Basin, southern Vietnam.
Fault and fracture characteristics of a major fault zone in the northern North Sea: analysis of 3D seismic and oriented cores in the Brage Field (Block 31/4)
Authors: Aarland R. K. , Skjerven J.
Published: April 2008

Based on three-dimensional (3D) seismic and core data, an analysis of fault geometry and fracture distribution related to a normal fault in the Brage Field, northern North Sea, has been achieved. The fault has a vertical throw of 200–300 m, and exhibits a steep ramp-flat-ramp geometry. Most of the deformation related to this fault is concentrated within a narrow zone in the hangingwall. Both extensional and compressional antithetic structures have been identified. The most intensive fracturing is associated with areas of change in the fault plane orientation. Correspondingly, these areas represent locations where questions regarding sealing capacity arise. The complexity of the fault zone caused difficulties in an exact pick of the fault plane. Oriented cores from one of the production wells in the area include a continuous 120 m long interval across the fault zone itself. Detailed measurements of fracture and bedding orientations were carried out using an automated goniometer as well as manual measuring techniques. Biostratigraphic data show that two faults can be identified within the narrow fault zone, with the main displacement recorded across the upper one. Fracture orientations and fracture distribution pattern versus core depth indicate, however, that the deformation is associated with the lower fault. Based on the core material which exhibits an asymmetrical distribution of deformation in relation to the fault zone, an exact determination of the depth of the fault plane has been possible. It is concluded that the lower interval is the initial main fault. The largest slip has, however, been taken up across the upper interval, representing a hangingwall splay fault.
Protection of groundwater quality in the UK: present controls and future issues
Authors: Harris R. C.
Published: April 2008

Groundwater pollution and its prevention are discussed in the context of the currently perceived issues in the UK and Europe and the future challenges, particularly in addressing historical pollution within the existing regulatory framework. Contamination from industrial processes and facilities is considered to be the most serious point source but its significance has not been appreciated because of the preoccupation with landfills. The influences of legislation, education and policy are reviewed and the growing impact of liability issues discussed. Progress in the development and implementation of the Environment Agency’s Groundwater Protection Policy is described. Developments in the use of groundwater modelling and risk assessment techniques are considered in the light of the growing need to examine the cost-effectiveness of remedial treatment of historical pollution.
Foreseeability of environmental hazards: the implications of the Cambridge Water Company case
Authors: Paul Ashley R.
Published: April 2008

The House of Lords decision, in the case of
Cambridge Water Company
v.
Eastern Counties Leather and Others
, introduced the concept of foreseeability as one test of civil liability for environmental pollution. In this paper the main criteria for foreseeability of pollution hazards are considered, including:

•

recognition of the acute and chronic toxicity of a potential pollutant;

•

availability of suitable detection and analysis methods;

•

understanding of migration and transport mechanisms in the environment.

Examples of the application of foreseeability criteria are discussed, such as chlorinated hydrocarbon solvents (as in the Cambridge Water Company case), methyl tertiary butyl ether and mine drainage waters.
Sewage sludge disposal to agriculture and other options in the UK
Authors: Andrews R. J. , Lloyd J. W. , Lerner D. N.
Published: April 2008

Due to the forthcoming European Union ban on sewage sludge disposal at sea and associated environmental legislation which has increased the amount of sewage sludge produced annually in the UK, there is a need for consolidation and expansion of existing sludge disposal outlets and assessment of the suitability of alternative and innovative disposal options. This paper reviews the main elements of sludge disposal in the UK in relation to their environmental sensitivity, sustainability and general security. Much of the additional sludge produced by changes in waste water treatment is likely to be accommodated by an increase in disposal by incineration and application to agricultural land. The effect of sludge application to land has, therefore, come under increasing examination, primarily due to potentially detrimental long-term effects on soil fertility and on nitrate leaching to groundwater. The implications and causes of nitrate leaching are discussed in relationship to sludge types and recommendations made for minimizing potentially adverse impacts to sensitive groundwater.
Investigation of contamination at a public supply borehole in Hertfordshire, UK
Authors: Davey I. , Moxon I. , Hybert D.
Published: April 2008

For several years a public supply borehole in Hertfordshire has suffered intermittent low level contamination by ammoniacal nitrogen. The situation worsened in about 1990 when the concentration began to rise steadily. Concentrations of other ions, including chloride, had also risen over a number of years. The site has limited treatment capacity and, because of the ammoniacal nitrogen contamination, it became necessary to take the source out of supply. Investigation of the problem began in 1994, concentrating on the potential contaminant sources nearby which were a pig slurry lagoon, a landfill and a river, which carries a loading of sewage effluent. Monitoring indicated the slurry lagoon to be the most likely cause of contamination to the public supply. The lagoon was emptied in 1995 which revealed that no liner existed and that there was apparent continuity with groundwater. Subsequent monitoring reinforced the evidence for a connection between the slurry lagoon and the public supply. However, contaminants were also found in association with the landfill and the river and contributions from these cannot be ruled out.
Pollution resulting from the abandonment and subsequent flooding of Wheal Jane Mine in Cornwall, UK
Authors: Bowen G. G. , Dussek C. , Hamilton R. M.
Published: April 2008

The closure of Wheal Jane Mine in Cornwall and the withdrawal of dewatering pumps resulted in the flooding of mine workings extending over a large area. The mine drainage was historically very acidic and high in metals. In order to predict the impact of the mine discharge, the National Rivers Authority commissioned a programme of investigations and monitoring. This paper describes the monitoring and assessment work undertaken at Wheal Jane during mine flooding in order to predict the discharge, location, time, quantity and quality, and the potential impact on groundwater sources used for potable supply. It also describes the subsequent mine water discharge and actual monitored levels of flow and water quality.

Investigations and monitoring of the flooding mine system included a detailed mining survey, the recording of water levels at suitable shafts, the collection and analysis of mine water samples and water quality depth profile surveys in a number of shafts. Surveys and monitoring of groundwater sources were also undertaken. Measurement of water levels and the mining survey allowed accurate prediction of the location and time of discharge. An estimate of the mine water discharge of between 5000 m
3
day
−1
and 20 000 m
3
day
−1
was prepared from catchment water balance calculations. This compares with the seasonally fluctuating, actual discharge of between 5000 m
3
day
−1
and 40 000 m
3
day
−1
. Mine water quality samples and water quality depth profiles taken from different shafts across the mine system identified large variations; in general, becoming more acidic with higher concentrations of metals with depth. Following flooding, the initial discharge quality was within the range predicted, with a pH of 2.8 and total metals of approximately 5000 mg l
−1
, notably consisting of iron, zinc and cadmium. Surveys identified a number of groundwater wells and boreholes close to the mine system which required regular monitoring. None were identified to have been affected during the mine flooding or following discharge.
Migration of dissolved petroleum hydrocarbons, MTBE and chlorinated solvents in a karstified limestone aquifer, Stamford, UK
Authors: Banks David
Published: April 2008

Two incidents of hydrocarbon contamination to the Lincolnshire Limestone in east Stamford, UK, have been investigated. No evidence of LNAPL contamination of groundwater was observed, suggesting that the spills may largely have been retained in the unsaturated zone. Some groundwater contamination by dissolved hydrocarbons occurred, apparently especially at times of high recharge. Rapid flow paths were proven to nearby springs in the River Welland (with groundwater flow velocities of up to 240 m day
−1
), and dissolved hydrocarbon and MTBE contamination appears to have been flushed rapidly from these systems. MTBE contamination at Tallington Pumping Station (5 km east of the site) is not clearly linked to these incidents. Of potentially more concern was the discovery of dissolved chlorinated solvent contamination in the groundwater at the spill sites, possibly related to a landfilled quarry and/or a nearby engineering works. No direct evidence of DNAPL was observed. A conceptual model of solvent distribution suggests independent sources of TCE, PCE and TCA.
Remediation of hydrocarbon leakage from a service station at Wansford, Cambridgeshire, UK
Authors: Clark R. G.
Published: April 2008

Two service stations have been built at the location of the present Nene Service Station on the A47 Trunk Road at Wansford, Cambridgeshire, UK; one replacing the other. Both have been affected by ground movements resulting from the reactivation of a periglacial landslip. During the investigation of these ground movements, hydrocarbon contamination was found in the flood plain gravels adjacent to the River Nene, which is downslope of the present service station. The paper describes the investigation work undertaken, with emphasis on soil vapour monitoring to map the contaminant plume. Remedial measures carried out included pump-and-treat of contaminated groundwater from a recovery pit, together with removal of LNAPL phase petroleum by means of absorbent pads.
Groundwater remediation of chlorinated hydrocarbons at an electronics manufacturing facility in northeastern USA
Authors: Muldoon D. G. , Connolly P. J. , Makovitch A. W. , Holden J. M. W. , Tunstall-Pedoe N.
Published: April 2008

An extensive investigation was undertaken to determine the degree and extent of contamination of three groundwater production wells by chlorinated solvents, and to design a full-scale remediation programme. Four major potential contaminant sources were identified. Hydrogeological investigations included drilling and multi-level groundwater sampling of 21 wells at 11 locations, monitoring of road-salt chloride as a groundwater flow tracer, and a seven-day pumping test to confirm the conceptual hydrogeological model. Immediate remedial measures were recommended to minimize further groundwater contamination. Camp Dresser & McKee’s three-dimensional models DYNFLOW and DYNTRACK were used to develop a contaminant transport model which was used extensively in a feasibility study for long-term remediation. The implemented remedial programme included installation of a pump-and-treat system involving two extraction wells and surface treatment of the water in an air stripper. Operational and performance data for the remedial system are given for the first three years of operation. In this time progress towards treatment standards has been slow. However, treated water has been used in the manufacturing plant and the system has acted as a hydraulic control, preventing the dissolved contaminant plume reaching one of the original abstraction wells which supplies water to the plant.
Groundwater pollution by chlorinated solvents: the landmark Cambridge Water Company case
Authors: Misstear B. D. R. , Ashley R. P. , Lawrence A. R.
Published: April 2008

The case of
Cambridge Water Company
v
Eastern Counties Leather plc and
v
Hutchings and Harding Ltd
is believed to be the first case this century in which common law principles have been applied to groundwater pollution in England. The case concerned the pollution of a public water supply borehole at Sawston, Cambridgeshire, by the chlorinated solvent tetrachloroethene, and the attempts by the water company to recover damages from the alleged polluters. Following discovery of the pollution in 1983 and subsequent investigations, the case was heard in the High Court in 1991, the Court of Appeal in 1992, and was finally decided by the House of Lords in 1993. This paper sets out the background and chronology of the case, reviews the investigations into the nature and extent of groundwater pollution, and then considers the legal arguments and findings of the courts and the House of Lords. The paper concludes with a discussion of some of the technical implications of this case, especially in relation to the collection of hydrogeological evidence.
Groundwater monitoring to assess the influence of injection of liquid radioactive waste on the Tomsk public groundwater supply, Western Siberia, Russia
Authors: Lgotin V. , Makushin Y.
Published: April 2008

This paper considers the potential impact of the deep injection of liquid radioactive waste (LRW) on the continued operation of the Tomsk public groundwater supply. The close proximity of the LRW injection polygons to the wellfield creates a geoenvironmental conflict, due to the possibility of migration of radionuclides and other toxic components of LRW from the Cretaceous aquifer system used for LRW injection to the Palaeogene aquifer complex used for water supply. Although a significant argillaceous aquitard and a non-utilized buffer aquifer horizon lie between the aquifer systems, there are indications that such inter-aquifer migration may take place, either due to sandy windows in the aquitard or to inadequately sealed well annuli. A major groundwater monitoring network, based on the co-operative use of automated information systems and GIS technologies, has been established. In order to simulate contaminant migration scenarios, the use of variably scaled numerical hydrogeomigrational models is recommended. These would allow prognostic estimations and form a basis for administrative decision-making to minimize damage to the geological environment.
Pesticides in groundwater: some preliminary results from recent research in temperate and tropical environments
Authors: Chilton P. J. , Lawrence A. R. , Stuart M. E.
Published: April 2008

The paper summarizes the preliminary results of field investigations of pesticide behaviour in the UK, Barbados and Sri Lanka. Field observations of groundwater pesticide concentrations in these studies range up to 100 µgl
−1
, but are more commonly less than 5 µgl
−1
. The risk of pesticide concentrations in pumped water reaching 10 or 100 times guideline values from normal agricultural use at recommended application rates is probably small. Simple laboratory determinations of degradation rates support earlier studies and general considerations of subsurface environmental conditions in suggesting that pesticides are likely to be more persistent in groundwater than in soils. Simple modelling of the saturated zone movement of pesticides towards wells indicates that concentrations in pump discharge are highly sensitive to aquifer porosity, pesticide half-life and extent of cultivated area. The greatest risk to groundwater from normal usage of pesticides in agriculture will occur where persistent compounds are applied over aquifers which are shallow, permeable and thin, and overlain by permeable soils.
Shallow geotechnical profiles, acoustic character and depositional history in glacially influenced sediments from the Hebrides and West Shetland Slopes
Authors: Paul Michael A. , Talbot Lisa A. , Stoker Martyn S.
Published: April 2008

Surficial sediments from the Hebrides and West Shetland Slopes are mostly matrix-supported diamictons or laminated muds with subordinate sand. Those from the outer shelf and upper slope have water content and undrained shear strength profiles that suggest variable light to moderate overconsolidation, whereas those from the lower slope and basin floor have water content and undrained shear strength profiles that suggest normal consolidation. We believe that these geotechnical differences are genetic and reflect the processes operative in former glacial and glaciomarine palaeoenvironments along the continental margin: variably overconsolidated sediments are the products of marginal or proximal glaciomarine environments in which ice loading has occurred, whereas normally consolidated sediments are found in distal glaciomarine to basin plain settings. The depositional setting also controls the void index of the sediment via its sedimentary fabric and we find a sensible relationship between the compression curve of a sediment and its mode of deposition. It is usual to find that individual values lie scattered about this curve as a result of small variations in the packing. These variations correspond to minor sediment layers from which acoustic reflections may interfere constructively to give a multilayered acoustic texture, whose appearance is thus ultimately related to the magnitude of the scatter.
Cenozoic changes in the sedimentary regime on the northeastern Faeroes margin
Authors: Nielsen T. , Van Weering TJ. C. E. , Andersen M. S.
Published: April 2008

An area on the northeastern Faeroes margin has been studied in detail using multichannel, high-resolution, seismic-reflection data which have revealed an early Tertiary basaltic basement overlain by an up to 2 km thick, wedge-shaped succession of sediments. Seismic facies analysis of the sedimentary succession has given rise to a sequence-stratigraphic interpretation of the slope. In addition, the study has provided information about changes in the sedimentary regime and variations in slope stability during deposition of the slope-apron caused by changes in sea level and the bottom-current regime.
Seismic characterization of Palaeogene depositional sequences: northeastern Rockall Trough
Authors: Egerton Paul D.
Published: April 2008

Palaeogene depositional geometries and sedimentation patterns along the Hebridean margin in the northeastern Rockall Trough have been strongly influenced by the interaction of complex structure and bathymetric morphology. An evaluation of the seismo-stratigraphy of this margin has been undertaken using multichannel seismic-reflection data. Analysis of these profiles reveals that the late Palaeocene volcanic unit displays well-developed oblique to sigmoidal clinoforms and internal seismic facies variations indicative of westward progradation into a marine basin. This volcanogenic unit is overlain by a lower to middle Eocene seismic unit characterized by moderate- to high-amplitude downlapping reflection configurations and is interpreted to represent a shelf-margin deltaic system. A prominent upper Eocene to lower Oligocene unconformity surface that truncates the shelf-margin wedge can be identified and correlated regionally along the Hebridean margin. This significant unconformity surface is onlapped by upslope accreting high-amplitude continuous reflectors with complex mounded geometries which are interpreted as deep-water contourite drifts of middle to upper Oligocene age. Distinct upper Eocene to lower Oligocene point-sourced fans are preferentially developed along the southern margin of the Wyville-Thomson Ridge. These seismic packages are inferred to have been deposited during a lowstand in relative sea level induced by compressional uplift of the Wyville-Thomson Ridge, and have wide-ranging implications for understanding the distribution of sand-prone fans in general around the western and eastern margins of the Rockall Trough.
Sediment-drift development on the continental margin off NW Britain
Authors: Stoker M. S.
Published: April 2008

The long-term record of sediment-drift development on the continental margin off NW Britain was investigated using seismic-reflection data calibrated with boreholes and short cores. These data indicate that the onset of bottom currents on the NW British margin occurred in the early late Eocene following a major phase of subsidence in the Rockall Trough and Hatton-Rockall Basin. Seismic reflection profiles reveal the downwarped and eroded surface of lower upper Eocene and older strata onlapped by middle to upper Cenozoic sediments. The latter consist predominantly of deep-marine contourites preserved both as mounded, elongate, and broad, sheeted, sediment drifts with associated sediment waves. Seismic-stratigraphical analysis of the drift succession has revealed a broad two-stage depositional history. A vigorous bottom-current regime in the late Eocene to mid-Miocene interval was accompanied by significant lateral migration of sediment by upslope accretion onto the flanks of the basins, including the construction of the bulk of the Feni Ridge. Mid-Miocene tectonism modified the palaeoceanographic and sedimentary regime. In the ensuing mid-Miocene to Holocene interval, drift accumulation persisted in the axial and eastern part of the Rockall Trough whereas a largely erosional regime prevailed on its western margin. The overall locus of drift sedimentation shifted westeards onto the Rockall Plateau.
Cyclic sedimentation on the Faeroe Drift 53-10 ka BP related to climatic variations
Authors: Rasmussen Tine L. , Thomsen Erik , Van Weering Tjeerd C. E.
Published: April 2008

More than 15 sedimentary cycles dated to the last glacial period (53-10 ka BP) have been recognized in a contourite deposit on the Faeroe Drift in the southern part of the Norwegian Sea. Each cycle consists of a silty, basaltic lower part and a clayey, acidic (siliceous) upper part. The sedimentary cycles can be accurately correlated with the Dansgaard-Oeschger temperature cycles in the Greenland ice cores, and it appears that the cyclic sedimentation was controlled by climatic and palaeoceanographic changes. The basaltic layers were deposited during warm interstadial periods in a current regime that resembles the modern circulation system in the North Atlantic region. Deep bottom-water created by thermohaline convection in the Norwegian-Greenland Seas flowed along the Iceland-Faeroe Ridge into the Atlantic Ocean, with the Faeroe-Shetland Channel as the main gateway. The source of the basaltic sediments was the volcanic rocks and detritus on the Iceland-Faeroe Ridge and on the shelf of eastern Iceland. The fine-grained acidic (siliceous) layers were deposited during intervening cold periods, in which convection took place in the subpolar North Atlantic Ocean and the circulation was reversed in the Faeroe-Shetland Channel. The acidic deposits were carried into the Norwegian Sea from the Hebrides and West Shetland shelves and the northeastern Atlantic Ocean.
Late Quaternary stratigraphy and palaeoceanographic change in the northern Rockall Trough, North Atlantic Ocean
Authors: Howe J. A. , Harland R. , Hine N. M. , Austin W. E. N.
Published: April 2008

A series of six shallow gravity cores, taken from a variety of sedimentary settings in the northern Rockall Trough, have been analysed using microfossil and sedimentological techniques. Cores from sediment waves on the Barra Fan are interpreted as being sequences of hemipelagites, turbidites and hemiturbidites. Northeastern Rockall Trough cores, from slope apron, escarpment and sediment drift areas are interpreted as hemipelagites, with glaciomarine deposits interbedded with and overlain by muddy-silty and sandy contourites. The dinoflagellate cyst, planktonic foraminifera and nannofossil biostratigraphy reveals a four-fold deglaciation record, with a single long core from the Barra Fan seemingly containing all four divisions of the Late Glacial, Allerød-Bölling, Younger Dryas and Holocene intervals. The sedimentary record suggests that deglaciation in the North Atlantic Ocean was not a simple linear process but an irregular, non-linear series of rapid events characterized by sudden sea-surface temperature changes, and fluctuating bottom-current activity.
About this title
Authors: Stoker M. S. , Evans D. , Cramp A.
Published: April 2008

There has lately been a growth in the level of study of continental margins. Apart from increased scientific interest, studies of continental margins have now taken on a much higher commercial profile, largely because of the oil industry’s move off the shelf into increasingly deeper waters world-wide. The variation and disturbance of sediments on slopes make them ideal areas for the generation, migration and entrapment of hydrocarbons.

The three topics considered in this volume are of particular significance to continental margin development. The 19 papers provide a sample of recent and current work with an emphasis on processes active beyond the shelf break. Individual researchers have unsurprisingly tended to concentrate on specific types of process, having chosen study areas well suited to the investigation of specific phenomena. The key distinction of processes is that between downslope, alongslope and hemipelagic processes. There is, however, increasing recognition that all these need to be integrated to produce a model of continental margin development. The processes will differ in importance in space and time, but their interrelationship needs to be understood, and background processes must be appreciated. A notable contribution of this volume is an increased awareness of the importance of alongslope processes within this model.

It is thought that in ten years’ time as much as 25% of oil will be extracted from deep-water fields. An understanding of continental margin processes is therefore becoming crucial to the safe development of deep-water oilfields. The papers in this volume thus have considerable actual or potential commercial value.
Mapping groundwater vulnerability: the Irish perspective
Authors: Daly Donal , Warren William P.
Published: April 2008

The groundwater protection scheme used in the Republic of Ireland since the 1980s had not encompassed the vulnerability mapping concept. Yet internationally, vulnerability maps were becoming an essential part of groundwater protection schemes and a valuable tool in environmental management. Consequently, following a review of protection schemes world-wide, the scheme used in Ireland was updated and amended to include vulnerability maps as a crucial component of the scheme.

The approach taken to vulnerability assessments and mapping in the Republic of Ireland has been dictated by the following fundamental questions: Vulnerability of what? Vulnerability to what? Which factors determine the degree of vulnerability? What is the appropriate scale for map production? How can limitations and uncertainties be taken into account? How can vulnerability assessments be integrated into environmental and resource management?

The following decisions were made: (i) we should map the vulnerability of groundwater, not aquifers or wells/springs; (ii) the position in the groundwater system specified to be of interest is the water-table (i.e. first groundwater encountered) in either sand/gravel aquifers or in bedrock; (iii) we should map the vulnerability of groundwater to contaminants generated by human activities (natural impacts are a separate issue); (iv) as the main threat to groundwater in Ireland is posed by point sources, we should map the vulnerability of groundwater to contaminants released at 1–2 m below the ground surface; (v) the characteristics of individual contaminants should not be taken into account; (vi) the natural geological and hydrogeological factors that determine vulnerability are the sub-soils above the watertable, the recharge type (whether point or diffuse) and, in sand/gravels, the thickness of the unsaturated zone; (vii) based on these factors, four vulnerability categories are used (extreme, high, moderate and low); (viii) map scales of 1:50 000 and 1:10 000 are preferred; (ix) limitations and uncertainties are indicated by appropriate wording on the maps and a disclaimer; (x) vulnerability maps should be incorporated into groundwater protection schemes, which should be used in decision-making on the location and control of potentially polluting developments.

Vulnerability maps have now been produced for a number of local authority areas. They are an important part of county groundwater protection schemes as they provide a measure of the likelihood of contamination, assist in ensuring that protection schemes are not unnecessarily restrictive of human economic activity, help in the choice of engineering preventative measures, and enable major developments, which have a significant potential to contaminate, to be located in areas of relatively low vulnerability and therefore of relatively low risk, from a groundwater perspective.
Exploration history of the Palaeozoic petroleum systems of North Africa
Authors: Traut Marc W. , Boote David R. D. , Clark-Lowes Daniel D.
Published: April 2008

Subsurface exploration of the Palaeozoic petroleum systems of Libya, Algeria, Tunisia and Morocco began in the early 1950s after the discovery of a large prospective Palaeozoic basin in the Sahara Desert province of North Africa. The first exploration well to test this concept was drilled in Algeria in 1952. A non-commercial find in 1953 was followed by major discoveries in 1956. Since that time approximately 1100 new field wildcats have been drilled to test Palaeozoic and basal Triassic reservoir targets in a variety of discrete petroleum systems. This resulted in the discovery of approximately 330 Palaeozoic-sourced accumulations in the Algerian, Libyan and Tunisian portions of the Sahara Desert. By the end of 1996 ultimate recoverable reserves in oil equivalent for these discoveries were estimated to be just over 46 billion barrels. Using measures of activity and reserves discovered, it is seen that the history of exploration of this province has followed a normal cycle, familiar to the petroleum industry, which can be divided into five major periods. They are: Pre-Discovery, Discovery, post-Discovery Boom, post-Boom and Revival. It is anticipated that future advances in technology will result in new ideas and more effective exploration, and ultimately in the future discovery of significant oil and gas reserves.