bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract

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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
An investigation of the thermal history of the Ahnet and Reggane Basins, Central Algeria, and the consequences for hydrocarbon generation and accumulation
Authors: Logan Paul , Duddy Ian 
Published: April 2008

Abstract

In an attempt to better understand the thermal history of the Ahnet and Reggane Basins, the techniques of apatite fission track analysis and zircon fission track analysis were employed on samples from a number of exploration wells previously drilled in the study area. The results indicated clear evidence for a major heating event at
c.
200 Ma, overprinted on the effects of heating caused by simple burial before the Hercynian uplift. It is proposed that at least two major phases of hydrocarbon generation took place within the study area; an early, pre-Hercynian phase, in which chiefly liquid hydrocarbons were expelled and a later phase, associated with a ‘heat spike’ at
c.
200 Ma, in which significant quantities of dry gas were generated and expelled.
Mesozoic rifting and basin inversion along the northern African Tethyan margin: an overview
Authors: Guiraud R. 
Published: April 2008

Abstract
The northern African Tethyan margin registered three major rifting episodes from the latest Palaeozoic-earliest Mesozoic to the earliest Cenozoic. Break-up of Gondwana was initiated in the late Carboniferous. Along the northern African-Arabian plate margin rifting propagated westward from the northeastern Arabian margin to Morocco during the Permian and Triassic, and was accompanied by Mid-Late Triassic-earliest Liassic extensive alkaline flow basalts. Rifting continued during the Liassic, e.g. in the Moghrebian Atlas troughs. A second stage of rifting occurred in the Late Jurassic and continued into, or was rejuvenated during, the Early Cretaceous. Along the east Mediterranean margin, some large E-W trending rifts formed, often with associated volcanism, e.g. southern Sirt and Abu Gharadig. Most researchers believe the oceanization of the eastern Mediterranean basin occurred at this time. Flexural subsidence affected the Moghrebian Atlas, including the Riffian-Tellian domain, where a thick flysch series was deposited. Two short-lived, but widespread and tectonically important, compressional or wrench-dominated events occurred during the Santonian and the latest Maastrichtian. From Morocco to Oman, most sedimentary basins were folded and inverted at these times. The Santonian event resulted from onset of the collision between the African-Arabian and Eurasian plates. New stress-fields favoured NE-SW extension along the African plate margin, generating or rejuvenating some rifts, e.g. in the Euphrates trough and in the Libya-Tunisia region (northwestern Sirt, Pelagian Sea). Rifting and magmatism continued in these regions into the Paleocene. During the Mesozoic, therefore, the northern margin of the African-Arabian plate registered both rifting resulting in the oceanization of the Tethys and rifting resulting from the initiation of the closure of the Tethys. The intraplate domain exhibited echoes of the tectonic events affecting the margin.
An overview of the petroleum systems of Morocco
Authors: Morabet Al Moundir , Bouchta Rabah , Jabour Haddou 
Published: April 2008

Abstract
Magoon & Dow’s petroleum system concept is utilized in this paper to evaluate the origin of the proven hydrocarbon resources of Morocco, which lie chiefly in the Essaouria, Prerif and Rharb Basins. Several systems are interpreted, in which the confidence in the source-petroleum tie varies from ‘known’ to ‘speculative’, involving charge from Silurian (eastern Essaouira), Lias (Prerif), Oxfordian (western Essaouira), Cretaceous (Ain Hamra) and an intra-Miocene biogenic system in the Rharb Basin. The origin of the Cap Juby heavy oil accumulation in the offshore Tarfaya basin is uncertain, with a Jurassic carbonate source currently the favoured interpretation. The petroleum system concept is extended in this paper to predict further, currently undrilled and unproven systems. These include areas where the proven source systems referred to above are likely to extend, plus additional systems predicted on the basis of analogues to surrounding regions. An example of the latter is a series of postulated Triassic systems developed in lacustrine deposits in offshore half-grabens. Palaeozoic source rocks may be regionally developed and may still be in the oil and gas windows over wide, generally unexplored, regions. Lower to Middle Jurassic source rocks are predicted in lagoonal settings in platform sags and in outer shelf environments, whereas Cretaceous source beds occur in continental rift complexes and passive margins, with maturity likely to be reached in depocentres and below thrusts. Biogenic gas potential is probably confined to Neogene deposits in foreland and divergent margin basins. Further application of the petroleum system concept should help to significantly reduce geological risk, particularly in frontier exploration areas.
Application of fault seal analysis techniques in the Western Desert, Egypt
Authors: Richardson S. M. , Vivian N. , Cook R. J. , Wilkes M. , Hussein H. 
Published: April 2008

Abstract
The Western Desert is one of Egypt’s major hydrocarbon provinces. Most discoveries to date have been in the Cretaceous, with the Jurassic being the most underexplored interval, with the highest potential for new discoveries. Although trap styles vary, the majority are structural fault blocks, requiring fault seal on one or more bounding faults. Despite the number of excellent reservoirs present in the Western Desert, large field sizes are rare, with less than 50 MMBOE STOIIP (million barrels oil equivalent, oil initially in place) being predominant. This apparent failure to regularly prove larger field sizes can be considered a direct function of trap failure resulting from absence of fault seal. A number of fault seal analysis techniques including fault-plane profiles, smear-gouge ratios, incremental strain analysis and structural sections are available to directly address trap integrity. Case histories from the Western Desert are used to demonstrate the use of these techniques, and to highlight potential pitfalls. These case histories show that fault seal techniques allow a more accurate assessment of trap integrity in the Western Desert, provided they are applied iteratively, and integrated with other geological and geophysical data.
The thin-skinned style of the South Atlas Front in Central Algeria
Authors: Bracène R. , Bellahcène A. , Bekkouche D. , Mercier E. , de Lamotte D. Frizon 
Published: April 2008

Abstract
Seismic lines cutting through the southern front of the Sahara Atlas show that the front is not superimposed on a major basement fault. Folded Cretaceous rocks can be observed on these lines to overlie a décollement surface climbing from Triassic to Early Cretaceous, below which flat-lying sediments can be recognized. The structural style is thus interpreted to be thin skinned and the folds underlining the front as ramp- related features. The development of duplexes in the core of some anticlines explains the apparent thickening of Cretaceous and/or Jurassic strata revealed by boreholes. This thickening was previously interpreted to be related to now-inverted extensional half-grabens, a model which cannot now be supported. This new interpretation allows a reassessment of other parts of the Sahara Atlas system, the large-scale structural model for which is that of large half-graben system that has undergone inversion because of shortening between the High Plateau massif and Sahara Platform.