bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations and models of volcanic eruption columns
Authors: Woods Andrew W. 
Published: April 2008

Abstract
Direct observations, satellite imagery and field studies of air-fall deposits provide a wealth of information about eruption column dynamics. These data have stimulated a wide range of theoretical, experimental and numerical models of eruption columns to expose the fundamental physical controls. These models show that the motion of hot, turbulent, particle-laden eruption columns is sensitive to the eruption velocity and mass flux, as well as the temperature and grain size distribution of the erupting material. In turn, the eruption velocity and mass flux are sensitive to the magma volatile content, the conduit radius and the chamber pressure. The importance of magma-water interactions, the crater geometry, ambient winds and the atmospheric stratification on the motion of the erupted material are also discussed. Predictions of the models are compared and contrasted and possible avenues for future research are suggested.
Pyroclastic density currents
Authors: Druitt T. H. 
Published: April 2008

Abstract

High-speed, gravity-driven flows of hot particles and gas are a common and highly destructive product of explosive volcanism. They range widely in nature from expanded, turbulent suspension currents formed by lateral blasts or by the fountaining of vertical eruption columns, to highly concentrated granular avalanches formed by lava dome col-lapse or as dense underflows beneath suspension currents. The deposits from these flows, here called pyroclastic density currents, range in volume from much less than 1 km
3
to thousands of cubic kilometres, and may extend over 100 km from their source. This chapter reviews the eruption, transport and deposition of pyroclastic density currents from both geological and physical perspectives, focussing on some recent advances.
The great age of some Australian landforms: examples of, and possible explanations for, landscape longevity
Authors: Twidale C. R. 
Published: April 2008

Abstract
According to the major conventional models of landscape evolution there ought to be no land surfaces older than Oligocene, save some that have been exhumed. In reality, substantial areas of the Australian continent (as well as other parts of Gondwana and of Laurasia) are of Mesozoic or greater ages. Surfaces of Late Jurassic or Early Cretaceous ages are especially widespread. Many are of exhumed origin, but several notable features are of epigene-etch type. Their age ranges have been determined stratigraphically. In some instances (e.g. Gawler Ranges, Hamersley Surface, Eastern Uplands), the stratigraphic evidence is incontrovertible. Elsewhere the position and elevation of massifs, such as Arnhem Land, relative to Cretaceous shorelines demonstrate their essential antiquity. The survival of such very old palaeosurfaces is attributed to several factors, but particularly to unequal erosion, reinforcement mechanisms and the prevalence of vertical (epeirogenic or isostatic), rather than orogenic, earth movements.
Tertiary etchsurfaces in the Sudetes Mountains, SW Poland: a contribution to the pre-Quaternary morphology of Central Europe
Authors: Migoń Piotr 
Published: April 2008

Abstract
This paper presents the evidence of the major part played by deep weathering accompanied, or followed, by stripping of a weathering mantle in the formation of Tertiary surfaces in the Sudetes. It also highlights the complicated nature of the topography of surfaces developed upon differentiated bedrock over protracted time-scales. The evidence is gained from the available data about weathering mantles and Tertiary sediments, and from the analysis of pre-Quaternary landforms such as rolling plains, scarps and inselbergs. A classification of the Tertiary surfaces, recognized here as etchsurfaces, is proposed for the Sudetes. The palaeosurfaces in the Sudetes are regarded as a part of an extensive etch surface which dominated the Tertiary landscape of Central and Northern Europe.
The geochemistry and development of lateritized footslope benches: The Kasewe Hills, Sierra Leone
Authors: Bowden D. J. 
Published: April 2008

Abstract
A series of lateritized footslope benches are observed on the isolated hill masses which rise to 500 m above the interior plain of Sierra Leone. Field observations and chemical analyses of samples indicate that each bench has a characteristic geochemistry controlled by its own topography, hydrological environment and leaching history. The benches are related, each inheriting material from above and providing material for the bench below. The material is transported both mechanically and in solution. As a result, the parent material of each bench is not only the bedrock (metamorphosed volcanic and sedimentary rocks of Proterozoic age in the case of the Kasewe Hills), but also material which has undergone various degrees of lateritization. This cratonic region has been subjected to denudational processes since Mesozoic times at least. Denudational processes, especially etchplanation, are long continued, yet weathering, the development of breakaway slopes and subterranean flushing are patently continuing processes: these palaeosurfaces and palaeosoils may, therefore, be ancient in origin but they cannot be considered as being fossilized.
Rheology of planetary lithospheres: a review from impact cratering mechanics
Authors: Thomas P. G. , Allemand P. , Mangold N. 
Published: April 2008

Abstract
Impact craters are the only universal drills to probe planetary lithospheres. The relationship of the lithospheric thickness/crater diameter ratio and the morphology of the outer parts of the crater are controlled by the rheology of the target. These relationships indicate the following: (1) The lithosphere is thicker on silicated bodies than on icy bodies of the same size. (2) The lithosphere is thicker on small planetary bodies than on larger ones. (3) There is a secular lithospheric thickening and a planetary cooling for silicated and icy bodies. (4) Because of the thickness and the continuity of the lithosphere of one-plate planets, local mechanical disturbances may be transmitted over a long distance and may affect the entire planet. (5) Thermal properties of the lithospheres of satellites are incompatible with the chondritic abundance of radioactive nucleids. This indicates that the origin of satellites is more complex than the accretion-collision of chondritic/icy planetesimal swarms. (6) There is no direct relation between plate tectonics and lithospheric thickness. Some planets have (or have had) the same lithospheric thickness as the Earth, but have not developed plate tectonics. This indicates that plate tectonic development is controlled by parameters other than lithospheric thickness.
Tectonics of the southeastern Australian Lachlan Fold Belt: structural and thermal aspects
Authors: Gray David R. 
Published: April 2008

Abstract
The Lachlan Fold Belt of southeastern Australia is a 700 km wide belt of deformed, Palaeozoic deep and shallow marine sedimentary rocks, cherts, and mafic volcanic rocks. Characterized by large areas of chevron-folded turbidite sequences, linked contractional and strike-slip faults, and superposed thrust-belts of different age and vergence, it has large volumes of granite and low pressure/high temperature metamorphic rocks. Surface structural elements suggest that it formed by massive telescoping and strike-slip translation within a continental margin sediment prism along the former margin of Gondwanaland during the mid-Palaeozoic. Migrating, sporadic compressional and extensional events over the 100 Ma deformational history of the belt produced a crustally thickened, high geothermal gradient orogen, involving non-craton directed thrusting in an inferred convergent margin setting. Compressional periods were marked by eastward-migrating deformation zones involving detachment-related folding and reverse faulting in the largely turbidite dominated sequences. High-grade metamorphic rocks are not part of a metamorphic hinterland, but are largely confined to a shear zone-bounded crustal wedge in the central part of the fold-belt. Extension was marked by localized development of rift basins and half grabens accompanied by extensive granitic magmatism and silicic volcanism. Subsequent basin collapse was by reactivation/inversion of the extensional faults and folding of the basinal sequence. Magmatic activity and high temperature/low pressure metamorphism are linked to a convergent margin setting over much of the Middle Palaeozoic, but with major convergence in the Silurian.
The Scandinavian Caledonides and their relationship to the Variscan belt
Authors: Rey P. , Burg J.-P. , Casey M. 
Published: April 2008

Abstract
The main events that mark the contraction and extension histories of the Scandinavian Caledonides and the European Variscides are summarized. It is shown that continental subduction may have developed similarly large and asymmetric thrust systems in both orogens. However, while continent-continent collision developed in the Variscides, extension began in the Scandinavian Caledonides marking the end of continental subduction. This led extensional tectonics to affect two continental crusts with contrasting rheology and therefore led to contrasting extensional modes. We argue that plate divergence, responsible for extension in the Scandinavian Caledonides, was triggered by the Variscan collision between Laurasia and Gondwana. In contrast, horizontal buoyancy forces acting on a thermally softened thickened crust are more likely to have been responsible for extension in the Variscan belt.
Cenozoic evolution of the Central Andes in Bolivia and northern Chile
Authors: Lamb Simon , Hoke Leonore , Kennan Lorcan , Dewey John 
Published: April 2008

Abstract
The Central Andes in Bolivia and northern Chile form part of a wide and obliquely convergent plate-boundary zone where the oceanic Nazca plate is being subducted beneath the continental South American plate. In the latest Cretaceous and Palaeocene, this part of the Central Andes formed a volcanic arc along what is today the forearc region of northern Chile, with a wide zone of subsidence, as much as 400 km wide, at or close to sea level behind the arc. In the Eocene, the central part of the behind-arc basin was inverted to form a zone of uplift (proto-cordillera), about 100 km wide and along what is today the western margin of the Eastern Cordillera of Bolivia. The Altiplano basin and an early foreland basin were initiated at this time, receiving sediment from the Eocene proto-cordillera. Subsequently, the proto-cordillera widened, as the rate of deformation increased and deformation spread westwards into the early Altiplano basin, and also eastwards towards the Brazilian Shield. In the Late Miocene, deformation essentially ceased in the Altiplano and Eastern Cordillera. An intense zone of shortening was initiated in what is today the Subandean Zone on the eastern margin of the Central Andes, deforming the Oligo-Miocene foreland basin. Shortening in the Subandean Zone accommodated both underthrusting of the Brazilian Shield and also bending of the entire mountain belt about a vertical axis. It is suggested that much of the distinctive Cenozoic tectonic evolution of this part of the Andes is related to pre-Andean strength inhomogeneities in the South American lithosphere.
Recent advances in understanding the southern North Sea Basin: a summary
Authors: Glennie K. W. 
Published: April 2008

Abstract
After a short-lived but very successful phase of exploration in the UK North Sea, the need for extreme confidentiality ceased to exist for those fields that had already been discovered, including the gas fields of the southern North Sea; this led to a widespread dissemination of data from 1974 onwards, to the great benefit of the industry as a whole. Early difficulties in producing gas from reservoirs whose permeability had been reduced by the growth of diagenetic illite led to studies in depth- and facies-related diagenesis, which continues today in different parts of the Southern Permian Basin. A change from analogue to digital recording of seismic data coincided with improvements in computer technology, and transformed seismic from a tool with limited depth penetration, which required the skill of a dedicated specialist to interpret, to one that today is used universally by all exploration and production geologists; these advances led, in turn, to much improved stratigraphic and structural resolution.
Recent studies, especially in the former East Germany, have led to a better definition of the Permian. In Central Germany, Lower Rotliegend volcanics are overlain by sedimentary sequences of the Müritz sub-group (Upper Rotliegend 1), which are coeval coveal part of the combined Altmark and Saalian Unconformity. In northern Germany, this major hiatus is overlain by the Havel and Elbe subgroups (Upper Rotliegend 2) which, together with the succeeding Zechstein sequences, were all deposited within the youngest stages of the Permian, covering a probable time span of no more than 16 Ma. Deposition of up to 4000 m or so of Late Permian strata in such a short time indicates structurally controlled subsidence in addition to any of a thermal nature.
Permian (Upper Rotliegend) synsedimentary tectonics, basin development and palaeogeography of the southern North Sea
Authors: George Gareth T. , Berry Jeremy K. 
Published: April 2008

Abstract
Upper Rotliegend sedimentation in the southern North Sea Basin (SNSB) was a response to complex synsedimentary tectonics and cyclical climatic changes. During the early Upper Rotliegend, faulting (?dextral strike-slip) resulted in the formation of a number of isolated sub-basins e.g. the Sole Pit, Silverpit and the Broad Fourteens, which were gradually united as a consequence of the progressive collapse of the Inde-Cleaver Bank High. Basin-margin tectonics controlled the evolution of the basin and the nature and distribution of the various types of alluvial fan and fan delta systems that evolved during pluvial climatic phases. Many of the earlier Upper Rotliegend fans display a systematic lateral displacement along synsedimentary faults. Along the Dowsing Fault Zone, ‘dry-type’ alluvial fans display a progressive northwestward migration with time. Also, fan deltas, sourced from the Texel-Ijsselmeer High, young progressively to the SE along the trend of the main faults. These systematic lateral displacements have been tentatively explained by invoking dextral oblique transfer of the source area relative to the depositional basin, within the context of a strike-slip tectono-sedimentary model. Alternatively, in an extensional model, the distribution pattern could be explained by sourcing the fans from both the footwall scarps and the transfer zones of dip-slip faults. A rapid decline in synsedimentary faulting, and a gradual change to more pluvial climatic conditions, resulted in the development of larger ‘wet type’ fans during the later part of the Upper Rotliegend time interval.
Application of high-frequency cycle analysis in high-resolution sequence stratigraphy
Authors: Yang C. S. , Baumfalk Y. A. 
Published: April 2008

Abstract
High-resolution sequence stratigraphy analysis is based on the integration of third-order sequence analysis and high-frequency (Milankovitch) cyclicity analysis. Sliding window spectral analysis of wireline logs reveals wavelength changes of the high-frequency cycles along the bore hole. The abrupt wavelength change, shown as the break of the sliding window spectrum bands, indicates a stratigraphic discontinuity. The gradual wavelength change, detected by the gradual shift of the spectrum bands, reflects a gradual change in the rate of net sediment accumulation. These cyclicity patterns reflect the thickness variations of preserved depositional cycles, controlled by basin subsidence, eustatic sea-level/base-level fluctuations, and sediment supply. Observations from the subsurface of the southern North Sea indicate that the breaks of spectrum bands as well as the trend of spectrum band shift can be correlated between wells to help detailed sequence correlation. Cyclicity analysis of the synthetic logs generated from a two-dimensional sequence stratigraphic modelling confirms the lateral correlatability of the cyclicity pattern between wells. Integration of cyclicity analysis with traditional methods will help accurate and reliable sequence stratigraphic correlations in various settings, including biostratigraphically barren strata, thick intervals of fine-grained or coarse-grained sediments, and chalk sections. Such correlations are essential for the establishment of a proper geological model in the hydrocarbon exploration, development and production.
The East Irish Sea Basin — from caterpillar to butterfly, a thirty-year metamorphosis
Authors: Colter V. S. 
Published: April 2008

Abstract
In the thirty years since the award of the first licenses, the East Irish Sea Basin has emerged as a significant hydrocarbon province. This paper first lists some of the occasionally almost arbitrary events that led to the first success in the basin, the discovery of the Morecambe Field in 1974. An attempt is made to review progress over those thirty years in certain topics, namely (1) stratigraphy, (2) structure, (3) sedimentology, (4) diagenesis — ‘the Platy Illite problem’ and others, (5) uplift and inversion, (6) hydrocarbon sources and types, (7) East Irish Sea Basin analogues. The paper concludes by summarizing the current state of knowledge.
Stratigraphical relationships and a revised lithostratigraphical nomenclature for the Carboniferous, Permian and Triassic rocks of the offshore East Irish Sea Basin
Authors: Jackson D. I. , Johnson H. , Smith N. J. P. 
Published: April 2008

Abstract
The Lower Permian and Triassic successions of the offshore East Irish Sea Basin are probably the thickest of the United Kingdom Continental Shelf or UK mainland, but currently, no hierarchical lithostratigraphy exists for this offshore area. A summary is presented of the first comprehensive hierarchical lithostratigraphical nomenclature scheme to be established for the Carboniferous, Permian and Triassic rock successions of the offshore East Irish Sea Basin. This scheme, which has been sponsored by interested exploration companies, identifies 25 formal lithostratigraphical divisions following the methodology already established in BGS-UKOOA (British Geological Survey-United Kingdom Offshore Operators’ Association) revisions of North Sea lithostratigraphy.
Sixteen new lithostratigraphical names are introduced (nine in the Mercia Mudstone Group, one in the Sherwood Sandstone Group, three each within the Permian and Carboniferous successions). The lithology, wireline log characteristics and nature of the lower boundary are discussed briefly for each lithostratigraphical unit, together with correlations to the adjacent onshore successions where appropriate. Formal definitions of lithostratigraphic units, including type and reference sections are fully documented elsewhere. The aims of this study are to rationalize the existing terminology and to provide a practical scheme that will have the widest acceptance within the oil industry.
The presence of sulphate-reducing bacteria in live drilling muds, core materials and reservoir formation brine from new oilfields
Authors: Mcgovern-Traa Caroline , Leu Jyh-Yih , Hamilton W. Allan , Spark Iain S. C. , Patey Ian T. M. 
Published: April 2008

Abstract

The sulphate-reducing bacteria (SRB) produce the toxic gas hydrogen sulphide (H
2
S) and cause numerous problems in the oil and gas industry. It has been suggested that these organisms are either introduced to the formation by drilling or water injection or that they may be indigenous. Little is known of the activity and survival mechanisms of the SRB under reservoir conditions. In this study a number of samples from hydrocarbon reservoirs were inoculated into sulphate-rich growth medium to determine the presence and activity of the SRB. The samples studied included freshly drilled core material and live drilling muds. The majority of samples analysed contained SRB which produced H
2
S to varying degrees following different incubation times. Organisms capable of producing H
2
S at temperatures up to 95°C were detected. Often long incubation periods, in excess of 6 months, were necessary before H
2
S was produced. Many of the blank mud samples analysed (e.g. prior to use in the well) were already contaminated with sulphidogenic bacteria. Some of the cultures obtained to date have been studied in reservoir conditions core flood tests. It is hoped that the use of these laboratory tests will highlight any potentially damaging reactions prior to their occurrence in hydrocarbon formations.
Diagenesis of the Sherwood Sandstone Group in the southern East Irish Sea Basin (Blocks 110/13, 110/14 and 110/15): constraints from preliminary isotopic and fluid inclusion studies
Authors: Greenwood P. J. , Habesch S. M. 
Published: April 2008

Abstract

Diagenesis in reservoir sandstones from the southern East Irish Sea Basin has resulted in the precipitation of multiple generations of quartz and carbonate cements. Other cements are volumetrically minor and do not affect sandstone reservoir quality, which overall retains high porosities and permeabilities. Stable isotope data suggest that precipitation of caliche calcite cement during early diagenesis occurred at low temperature (
c.
30°C) from meteoric porewaters (−3‰ SMOW). By contrast δ
34
S data for evaporitic gypsum/anhydrite from the Ormskirk Sandstone Formation and Mercia Mudstone Group suggest that locally, an early marine sulphate source was available following deposition. Late burial anhydrite and barytes cements were derived through dissolution and reprecipitation of the early sulphates, according to stable isotope data. Fluid inclusion data for burial diagenetic cements record elevated temperatures (>100°C) for authigenic quartz, carbonate and sulphate minerals, which precipitated from concentrated brines. Stable isotopes indicate that porewaters enriched in
18
O evolved during burial and late carbonates incorporated increasing quantities of carbon derived from organic maturation at depth. An episode of hydrocarbon migration during burial, predating the influx of hydrocarbons currently found, is preserved as bitumen in the sandstones. Further cementation postdated this episode, including late calcite cements postdating the migration of the current hydrocarbon charge. Petrographic data indicate that the elevated temperatures recorded in burial cements were not achieved entirely through depth of burial but probably reflect periods of elevated heatflow, as a result of the circulation of hot fluids through the reservoir sandstones.