bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluid salinity and dynamics in the North Sea and Haltenbanken basins derived from well log data
Authors: Gran Kjetil , Bjørlykke Knut , Aagaard Per 
Published: April 2008

Abstract
The salinities of porewaters in sandstones and carbonate reservoir rocks from the North Sea and Haltenbanken basins have been calculated using resistivity logs. Applying Archie’s equation, hydrocarbon containing intervals were avoided and a 100% water saturation assumed in the calculations of the formation water resistivity. The salinities obtained vary from 20 000 to 300 000 ppm NaCl equivalents. The highest salinities, which approach saturation with halite, are found in the Southern North Sea, close to the Upper Permian evaporite sediments. There is a marked upwards decrease in the salinity values away from the evaporites. The salinities seem to be a function of the vertical distance to the evaporites and are independent of stratigraphic horizon. In the Northern North Sea, where Permian salt is absent, the salinity values are much lower (20 000–50 000 ppm NaCl eq.). This salinity stratification strongly indicates that large scale vertical mixing of porewater by convection or compaction driven pore water flow has not taken place. We can therefore conclude that saline pore water has not been transported from the deeper parts of the basin to the shallower parts. This also implies that there is no transport of carbonates or silicates in solution over the same distances. Calculation of salinities from well logs is subject to considerable uncertainties. However, the values obtained in this study agree well with reported values from formation water analyses. Mapping the distribution of salinity in the pore waters of sedimentary basins is very important and the information obtained can be used to constrain our models for porewater flow.
Tectonic and bathymetric controls on stratigraphic sequences within evolving half-graben
Authors: Roberts Alan M. , Yielding Graham , Badley Michael E. 
Published: April 2008

Abstract
A modification of the domino fault block model is presented, which can be used to evaluate possible tectonic controls on the development of stratigraphic sequences within an evolving half-graben. The model allows average half-graben load to vary with time and allows the rate of faulting to be varied relative to any background component of basin subsidence.
The basic domino model predicts only transgressive sequences at the crests of tilted fault blocks. It is found with the modified model that a decreasing average half-graben load (increasing bathymetry) or an increasing strain-rate may induce offlap and regression at the fault block crest. The model is used here successfully to model the syn-rift stratigraphy of a tilted fault block in the Viking Graben (North Sea). It is believed to have general implications for evaluating the syn-rift and early post-rift history of extensional basins.
The internal geometry of condensed and unconformable sequences at fault block crests may lie below the limit of seismic resolution. This calls into question the ability of the seismic stratigraphic technique to address successfully the full history of an evolving half-graben.
Comments on the pattern of post-rift subsidence in the Central and Northern North Sea Basin
Authors: Joy Aidan M. 
Published: April 2008

Abstract
Burial history analyses suggest that the post-rift subsidence history of the Central and Northern North Sea Basin is poorly explained by published models of thermal subsidence. The last rifting episode took place during the Late Jurassic. The early post-rift phase (earliest Cretaceous to Danian) was characterized by slow subsidence, with much of the sedimentation accommodated by the infilling of previously developed rift bathymetry. At this time the shoulders of the rift were supported. During the earliest Cretaceous to Danian, the Central and Northern North Sea Basin was situated in a continental interior, and its morphology and subsidence style resembled that of many modern intra-continental rifts. Sub-sequently, rates of subsidence increased markedly; this acceleration in subsidence was particularly pronounced in the region of the rift shoulders. The timing of the accelration was approximately mid-Palaeocene, the time at which the Norwegian-Greenland Sea opened immediately to the north of the North Sea Basin. It is suggested that there are differences between the subsidence rates and styles of extensional basins in intra-continental and continental margin settings which are not predicted by published models.
Permeability variation within aeolian sandstone: a case study using core cut sub-parallel to slipface bedding, the Auk Field, Central North Sea, UK
Authors: Prosser D. J. , Maskall R. 
Published: April 2008

Abstract
A combination of sedimentary dip, structural dip and borehole orientation resulted in a core recovered from the Auk Field being cut sub-parallel to aeolian slipface deposits. Individual 2 inch (5 cm) thick grainflow deposits may be followed for up to 16 ft (4.88 m) along core. A conventional core-plug permeability data-set indicated the importance of a deleterious effect of fine-grained ‘pin-stripe’ laminae which separate individual grainflows. Using a probe-permeameter, over 1000 permeability readings were taken from 27 ft (8.23 m) of the core, mostly on a 1 inch (2.5 cm) spaced grid, in order to study small-scale variations and controls of permeability. The readings were taken from five grainflow laminae and associated wind-ripple deposits in a single slipface deposit, and from wind-ripple laminae from an interdune setting.
Individual grainflow laminae sometimes show coarsening-upward patterns of grain-size variation which can be ascribed to dispersive forces acting during sedimentation. In terms of permeability distribution, individual grainflows may be distinct from their immediate neighbours. Geostatistical analyses indicate permeability correlation lengths across grain-flow laminae equal to lamina spacings, and a within grainflow correlation length of approximately 1.5 ft (46 cm). Similar tests within millimetre-scale laminated wind-ripple deposits indicate appreciably smaller correlation distances. These results can be translated into effective sampling strategies of one reading per grainflow deposit for a traverse perpendicular to sedimentary dip, and one reading every 6–12 inch (15cm–30cm) for a traverse along grainflow lamination. Wind-ripple laminae cannot feasibly be sampled in a truly representative fashion by standard core-plugs.
Petrographic analyses indicate that the principle microscopic controls upon permeability are grain-sorting, the development of authigenic cements and the detrital plus authigenic clay content.
The tectonic implications of contrasting granite magmatism between the Kohistan island arc and the Nanga Parbat-Haramosh Massif, Pakistan Himalaya
Authors: George Mark T. , Harris Nigel B. W. , Butler Robert W. H. 
Published: April 2008

Abstract

In northern Pakistan, an integrated structural and geochemical study across the contact between the Cretaceous-Tertiary Kohistan island arc and Indian crust of the Nanga Parbat-Haramosh massif (NPHM) has identified strongly contrasting source regions contributing to post-50 Ma magmatism, which constrains the tectonic evolution of the region. Nd-model ages of Tertiary intrusives increase dramatically across the contact from
c.
700 Ma in the Kohistan terrane to
c.
2500 Ma in the NPHM.

Following collision between the Indian continent and the Kohistan island arc terrane at
c.
50 Ma, biotite granite sheets (Confluence granites) were emplaced into the Kohistan batholith at 50–30 Ma, followed by muscovite granite sheets (Parri granites) at
c.
26 Ma. These are geochemically distinct, with the Confluence granites comprising a range of granitic compositions with high Sr and Ba abundances and the Parri granites forming granite sheets enriched in Rb. Undeformed granites in both suites have (
87
Sr/
86
Sr)
i
in the range 0.7045–0.7054 and ε
Nd
(
T
) of + 0.1 to +2.7, suggesting that both groups may be derived from juvenile arc sources. Detailed structural studies verify that the Kohistan granite sheets postdate the initial collision of the Kohistan terrane with the Indian continent, but are preor syntectonic with respect to continued underthrusting of the Indian continent below the Kohistan arc. These results, together with isotopic evidence from the undeformed granite sheets, suggest that significant underthrusting of northern Kohistan by the Indian continental crust could not have occurred until after 26 Ma.

Along the western margin of the NPHM, deformed granite sheets show a marked increase in (
87
Sr/
86
Sr)
i
(0.7075–0.7784), with decreased ε
Nd
(
T
) (−13 to −26). These trends are thought to be due to a combination of sub-solidus fluid infiltration and assimilation of crustal material, with fluids or material derived from the adjacent, isotopically evolved NPHM crust.

The NPHM (Indian continent) has been intruded by a series of tourmaline leucogranite dykes and plutons at 2–12 Ma. These intrusives have trace-element signatures consistent with generation by vapour-absent melting of a pelitic source. Sr-Nd isotope systematics indicate derivation from metasediments such as are currently exposed in the basement rocks of the massif, although melting at the present exposure level is generally precluded by subsolidus metamorphic grades in the country rock. Extreme heterogeneities in radiogenic Sr((
87
Sr/
86
Sr)
i
> 0.9) are observed in leucogranite dykes from the Liachar thrust zone, probably indicating subsolidus fluid infiltration. In general the NPHM leucogranites result from rapid exhumation of metasediments characterised by unusually high heat productivity.
Geochemistry of the continental basalts within the Tethyan Himalaya of Lahul-Spiti and SE Zanskar, northwest India
Authors: Vannay J. C. , Spring L. 
Published: April 2008

Abstract
The intrusive continental basalts of the Tethyan Himalaya are not necessarily comagmatic feeder dykes or the hypabyssal equivalents of the middle Permian Panjal Traps flows associated with the Permo-Mesozoic rifting of the Tethys, as is generally considered. A comparative study of basic rocks from SE Zanskar, NW Spiti and Upper Lahul shows the coexistence of geochemically different basalts in this region. The Panjal Traps of SE Zanskar and NW Spiti are tholeiitic continental flood basalts (CFB). They originated from an ‘enriched’ P-MORB-type magma which underwent a limited evolution by fractional crystallization and probable crustal contamination. In the adjacent Upper Lahul area, the Baralacha La Dyke Swarm shows a close spatial association with Lower Carboniferous transtensional synsedimentary faults. These dykes consist of tholeiitic to alkalic basalts, belonging to a comagmatic suite that evolved mainly by fractional crystallization. Geochemical data indicate that the Panjal Traps and the dykes are not comagmatically related. These characteristics imply either the coexistence, in the studied area, of contemporaneous but chemically different magmas or temporally unrelated magmatic events. The Baralacha La Dyke Swarm could be associated with a Lower Carboniferous transtensional tectonic event, related to an early phase of Permian rifting of Neo-Tethys.
Braided rivers: perspectives and problems
Authors: Bristow C. S. , Best J. L. 
Published: April 2008

Abstract
Progress towards a fuller understanding of the dynamics and deposits of braided rivers demands an interdisciplinary approach to a host of unresolved problems. Although many advances have been made within recent years in interpreting the mechanics of flow, transport of sediment and sedimentary architecture of braided rivers many key issues remain to be addressed. In particular, several areas demand attention: the mechanisms of braid bar initiation; confluence-diffluence dynamics, the nature of sedimentary facies over a range of grain sizes and the influence of flow stage and aggradational regime upon the depositional architecture over a range of channel scales. This paper focuses upon these issues and highlights several areas of fruitful future interdisciplinary collaboration.
Sedimentology of the Rough Rock: a Carboniferous braided river sheet sandstone in northern England
Authors: Bristow C. S. 
Published: April 2008

Abstract
The Rough Rock is a coarse-grained fluvial sheet sandstone which outcrops across northern and central England. It is interpreted as a braided river sandstone on the basis of sedimentary structures, internal erosion and growth surfaces. This study reveals that the Rough Rock represents more than a single phase of deposition and that internal erosion surfaces may indicate anabranch avulsions or more significant river avulsions. Detailed outcrop profiles are presented to try and distinguish the styles of deposition and the nature of internal bounding surfaces and channel geometry. The Rough Rock Formation contains a very large number of first and third order bedding contacts, which represent the migration of dunes and channels respectively, there are relatively few macroforms and bars preserved. The lack of second order surfaces within many outcrops could indicate that bars in the Rough Rock rivers were very large and therefore cannot be resolved at the outcrop scale. Similarly, the rivers which deposited the Rough Rock may have had such high width: depth ratios that the dip of second order bounding surfaces are too low to be identified. The large number of third order bounding surfaces indicates channel stacking which may have occurred in two ways: (1) relocation of rivers in the same area over time, or, (2) anabranch avulsion within a braided river within a hierarchy of channels. The problems associated with differentiating between these two mechanisms are discussed.
Basaltic-volcano systems
Authors: Walker George P. L. 
Published: April 2008

Abstract
This review and personal account of basaltic volcanism concentrates on the geological aspects and physical controls, unlike most others which concentrate on geochemistry. It serves as an update to reviews by Wentworth & Macdonald 20 to 40 years ago. The concept of volcanic systems is developed, a system including the plumbing, intrusions, and other accoutrements of volcanism, as well as the volcanic edifice. Five types of systems are described, namely lava-shield volcanoes, stratovolcanoes, flood-basalt fields, monogenetic-volcano fields, and central volcanoes (having silicic volcanics as well as basaltic). It is postulated that the system-type depends on (a) the magma-input rate and (b) the frequency with which magma-batches enter the system (or modulation frequency). These controls determine whether a hot pathway is maintained from the source to the high-level magma chamber, and hence if eruptions are concentrated in the central-vent system. Reviews are given on many aspects: the different kinds of rift zones that volcanoes exhibit, and their controls; the mostly small intrusions, including coherent-intrusion complexes, that occur in and under the volcanic edifices; the great sill swarms that are an alternative to flood basalts; the origin of the craters and calderas of basaltic volcanoes; high-level magma chambers, their locations, and cumulate prisms; the positive Bouguer gravity anomalies that are attributed to cumulates and intrusion complexes; the structures of basaltic lava flows; the characteristics of basaltic explosive volcanism and the consequences of participation by non-volcanic water; the products of underwater volcanism; the origin and significance of joints, formed either by contraction or expansion, in volcanic rocks; and the distribution of vesicles in basaltic rocks. A fairly extensive bibliography is included.
The development of a late Cretaceous microplate suture zone in SW Cyprus
Authors: Malpas J. , Calon T. , Squires G. 
Published: April 2008

Abstract
Recent detailed mapping and volcanic geochemistry of rocks exposed in erosional windows through post-Cretaceous cover rocks in SW Cyprus have provided evidence for the development of a model for late Cretaceous microplate collision in the eastern Mediterranean. Two major juxtaposed terranes are recognized: the older Mamonia Complex consisting of Triassic ocean floor, accompanying seamounts and a series of continental rise prism sediments, and the younger Troodos Complex consisting of ophiolitic rocks formed in a supra-subduction zone environment, and modified in part by transform fault tectonics and magmatism. The two complexes were juxtaposed along an intricate suture zone, the evolution of which displays two main phases of contractional deformation of late Cretaceous age. These are a primary north- and northwest-directed thrusting, and a secondary backthrusting episode towards the west and southwest, that in places reorganized the initial structural stacking sequence. Extensional faulting of Troodos Complex rocks, that took place on the ocean floor prior to juxtaposition, clearly influenced the orientation of the later thin-skinned delamination. Although there is some evidence for strike-slip faulting, this process does not appear as extensive as proposed by previous workers.
Re-evaluation of inclined intrusive sheets and dykes in the Cuillins volcano, Isle of Skye
Authors: Walker George P. L. 
Published: April 2008

Abstract

This paper presents new quantitative data on the mafic dykes and classic centrally inclined sheets (cone-sheets) of the Cuillin Hills. Most dykes were intruded into the NW and SE rift zones of the Cuillins volcano. The dyke-widths, and the downrift rate of increase of widths, are almost identical with those of Koolau dykes in Oahu (Hawaii). The dilation vector (direction of opening) is roughly normal to the plane of the inclined sheets, showing that the sheets are simple extensional intrusions like the dykes. Sheet thicknesses are nearly identical with dyke-widths, reinforcing this conclusion. Sheets cut dykes, and dykes cut sheets, showing that dyke or sheet injections alternated. Sheets are concentrated in the NW and SE sectors of the Cuillins where they comprise a coherent complex having intrusion-intensities of 40–807fb3e69creferentially injected into the rift zones. A mechanism is proposed in which magma batches were injected as bladed dykes or bladed sheets as the σ
3
stress direction oscillated between vertical and horizontal; this was in a tectonic setting where, because of slow extension, magma excursions could not all be accommodated as dykes. Injection of sheets resulted in a vertical thickening of the volcanic edifice by
c.
1.5 km about the same as the amount of widening by dykes.
Geochemistry of aliphatic-rich coals in the Cooper Basin, Australia and Taranaki Basin, New Zealand: implications for the occurrence of potentially oil-generative coals
Authors: Curry David J. , Emmett John K. , Hunt John W. 
Published: April 2008

Abstract
Although the concentration of long-chain aliphatic constituents is a primary determinant of the oil generation potential of coals, the factors which govern their occurrence in different coals are poorly understood. In this study, Permian coals from the Cooper Basin, Australia, and the Eocene coals from the Taranaki Basin, New Zealand, were compared to determine these factors.

The Taranaki Basin coals were deposited in temperate, fluvial-deltaic environments. HI values range from 236–365. Extracts have high pristane/phytane ratios and variable abundances of oleanane and other non-hopanoid terpanes. The extracts and pyrolysates contain high relative concentrations of aliphatic groups >
n
-C
20
. These data imply that much of this aliphatic carbon is derived directly from higher plant material.

The Cooper Basin coals were deposited in high latitude bogs and contain 40–70 0nertinite. The coals have been severely degraded. Pristane/phytane ratios are low (2.15–6), but HIs are moderate (up to 243 mg g
−1
OC). The extracts and pyrolysates both contain high relative concentrations of aliphatic groups; however, the distributions are different from higher plant-derived material. These data imply the bulk of the aliphatic carbon in these coals is derived from microbial biomass (both bacterial and fungal degradation products and algal input).

These results show that long-chain aliphatic groups in coals can be derived directly from the higher plant material, from microbial activity in the depositional environment, or from a combination of the two.
Crustal stress, faulting and fluid flow
Authors: Sibson Richard H. 
Published: April 2008

Abstract

Differential stress exerts both static and dynamic effects on rock-mass permeability, modulating fluid flow in the Earth’s crust. Static stress fields impose a permeability anisotropy from stress-controlled features such as faults, extension fractures, and stylolites which, depending on the tectonic regime, may enhance, or counteract existing anisotropic permeability in layered rock sequences. Textural evidence from hydrothermal veins suggests, however, that fluid flow in fault-related fracture systems generally occurs episodically and that dynamic stress cycling effects are widespread. In the vicinity of active faults that undergo intermittent rupturing, permeability and fluid flux may be tied to the earthquake cycle through a range of mechanisms, leading to complex interactions between stress cycling, the creation and destruction of permeability, and fluid flow. Mechanisms for fluid redistribution include: (1) various forms of
dilatancy
(localized to the fault zone or extending through the surrounding rock mass) related to changes in shear stress and/or mean stress that occur during the
fault loading
cycle; (2) localized
post-seismic redistribution around rupture irregularities
, especially dilational jogs and bends which act as
suction pumps
; and (3) post-seismic discharge of fluids from overpressured portions of the crust through
fault-valve
action when ruptures breach impermeable barriers. All of these processes may be involved in fluid redistribution around active faults, but they operate to varying extents at different crustal levels, and in different tectonic regimes.
Controls on two-phase fluid flow in heterogeneous sandstones
Authors: Ringrose P.S. , Corbett P.W.M. 
Published: April 2008

Abstract
The effective flow behaviour of two immiscible fluids in a permeable medium is a function of fluid/fluid as well as fluid/matrix interactions. These are described by relative permeability functions, which are strongly influenced by the spatial distribution of permeability in sedimentary media, given specified fluid and pore surface properties. For typical subsurface flow rates and patterns of rock heterogeneity in hydrocarbon reservoirs, capillary forces can result in significant amounts of trapping and bypassing of the non-wetting phase. Different types of sedimentary media (e.g. laminated, crossbedded and pervasively faulted strata) result in different, quantifiable, degrees of trapping. Examples of typical water-wet oil/water systems illustrate how the amount of trapped oil can vary between around 40% and 65% depending on the type of heterogeneity. Furthermore, the layered nature of most sedimentary strata means that the relative permeability of two immiscible phases is highly anisotropic. These findings have important implications for reservoir engineering and studies of oil migration.