bluuebunny/crossref_metadata_2025_split huggingface dataset:
Principal aspects of compaction and fluid flow in mudstones
Authors: Bjørlykke K. 
Published: April 2008

Abstract
Compaction and fluid flow in sedimentary basins are usually modelled as mechanical compaction assuming that the main driving force is the effective stress. However, in the deeper part of sedimentary basins (> 2–3 km, 70–100°C), compaction also involves dissolution and precipitation of minerals, and these processes are strongly controlled by temperature and to a lesser extent by variations in effective stress. The total pore-water flux is relatively independent of the permeability and pressure gradients because it is controlled by the rate of compaction. The main effect of permeability variations is the focusing of the compaction-driven flow. Fluids are also released by petroleum generation and dehydration of clay minerals; both these processes are also essentially temperature dependent. If the minimum permeability in one sedimentary layer (seal) falls below a critical value and there is little lateral drainage, the pressure will build up to fracture pressure. Pore pressures and fluid flow cannot be calculated from the matrix permeability of the rock when fracture pressures are reached, because much of the flow occurs along the generated fractures. The permeability produced by fracturing is a dynamic variable adjusting itself to the flux; it is not a rock property like the intergranular permeability. The intergranular permeability of shale samples before fracturing is also difficult to measure reliably in the laboratory as a result of unloading. This makes pressure prediction using one-dimensional pressure modelling uncertain. The prediction of permeability distributions in three dimensions is much more difficult.
In sight of the suture: the early Palaeozoic geological history of the Isle of Man
Authors: Woodcock N. H. , Quirk D. G. , Fitches W. R. , Barnes R. P. 
Published: April 2008

Abstract
The pre- and syn-Caledonian rocks of the Isle of Man are now known to comprise three distinct units: the early Ordovician Manx Group, the mid-Silurian Dalby Group and the ?late Silurian-early Devonian Peel Sandstones.
The Manx Group is dominated by Arenig deep-marine turbidites and debrites deposited in oxygenated basins on the northwest-facing margin of Avalonia. Its organization into a sand-rich lower part and a mud-rich upper part invites comparison with the Skiddaw Group (Lake District) and Ribband Group (Leinster) and points to control by margin-wide events, in part eustatic sea-level changes. Episodes of mass-wasting and Fe-Mn fluid exhalation also correlate along the margin. A mid-late Ordovician volcanic arc is missing above the Manx Group, although parts of its intrusive substructure may be preserved.
The Dalby Group comprises northwest-derived turbidites, sedimented into an anoxic basin during Wenlock (mid-Silurian) time. These turbidites were deposited in a successor basin above the Iapetus suture zone. The Dalby Group sits with a tectonic contact on the Manx Group.
No evidence has been found of a pre-Silurian cleavage. The main Caledonian D1 and D2 shortening phases are post-Wenlock, comparable in age with those further along the margin in the Lake District and Leinster. The Peel Sandstones preserve a Lower ‘Old Red Sandstone’ sequence, mostly removed by post-Caledonian erosion elsewhere along this outboard part of the Avalonian margin. The unit does not host a definite Caledonian cleavage, and it must have been deposited late in the deformation history. The granitic intrusions into the Manx Group range from early in D1 to late in D2. The intrusions generate only local aureoles, and the high metamorphic grade in parts of the Manx Group may be enhanced by favourable protolith compositions.
The Skiddaw Group (English Lake District) reviewed: early Palaeozoic sedimentation and tectonism at the northern margin of Avalonia
Authors: Stone P. , Cooper A. H. , Evans J. A. 
Published: April 2008

Abstract

The Skiddaw Group is a 5 km thick sequence of Tremadoc-Llanvirn turbiditic mudstone and sandstone, including a major olistostrome, which occupies the northern part of the Lake District Lower Palaeozoic Inlier. Sporadic outcrop and borehole records indicate that similar strata extend beneath other parts of northern England. To the west, the Manx Group of the Isle of Man is a regional correlative. The Skiddaw Group was deposited on the Avalonian margin of the Iapetus Ocean, with constituent sediment derived largely from an earlier, possibly Precambrian, continental margin volcanic arc. Nd isotope data confirm the absence of juvenile detritus. Olistostrome emplacement in the late Arenig preceded subduction-related uplift of the deep-marine Skiddaw Group to form the subaerial basement to the mainly Caradoc, Borrowdale and Eycott volcanic groups. The scale of the unconformity beneath the volcanic rocks requires considerable pre-volcanic disruption and erosion of the Skiddaw Group prior to structural disturbance by volcanotectonic faulting. Volcanism ended in the late Caradoc when thermal reequilibration, coupled with possible further extension, allowed marine transgression through the early Silurian. Ultimately, convergence of Avalonia with Laurentia initiated thrust imbrication of the Skiddaw Group as the Southern Uplands thrust belt extended across the sutured Iapetus Ocean. Thrust-related hydration caused widespread resetting of Rb-Sr isotope systems during the 430–420 Ma interval. A penetrative slaty cleavage with a broadly Caledonian trend was imposed during the Early Devonian, Acadian Orogeny and cuts an earlier, bedding-parallel (compaction) fabric. Later phases of Acadian compression probably involved reactivation of thrusts within the Skiddaw Group with associated strain partitioning resulting in domainal crenulation cleavage. Granite intrusion at
c.
400 Ma coincided with the final cleavage episode.
A comparison of the Ribband Group (southeastern Ireland) to the Manx Group (Isle of Man) and Skiddaw Group (northwestern England)
Authors: McConnell B. J. , Morris J. H. , Kennan P. S. 
Published: April 2008

Abstract
The lithostratigraphy of the Ribband Group of southeastern Ireland is revised through comparison to the equivalent Avalonian margin sequences of the Manx(Isle of Man) and Skiddaw (northern England) Groups. Four tracts are recognized in the Ribband Group, within which fossil age control and the ‘coticule package’ marker horizon are used to constrain lithofacies comparisons. Volcanic arc rocks in the Ribband and Manx Groups contrast with the passive margin provenance of the Skiddaw Group.
On the uplift and denudation of the Weald
Authors: Jones David K. C. 
Published: April 2008

Abstract

The evolution of the Weald has been the subject of continuing controversy over nearly two centuries of investigation. This paper reviews current knowledge of the area’s development during the Tertiary against this background and produces an evolutionary geomorphology focused on a cross-section reconstruction of the Weald stretching from the south coast to the Thames. Estimations of the original thickness of Chalk (400–460 m) and other Mesozoic strata indicate a complex fold structure which, if ever fully developed, would have had a crestal elevation of 1400 m. The additional accumulation of an estimated 60–220 m of Palaeogene sediments reveals gross denudation of up to 1350 m in 66 Ma or 20.4 m Ma
−1
, a low rate on relatively erodible strata indicating periods of relative morphostasis in the Tertiary. Four models of evolution are identified — ‘Neogene flexuring and erosion’, ‘pulsed tectonism focusing on Palaeogene denudation’, the classic Wooldridge and Linton interpretation, and the model detailed in this paper — and applied to the cross-sectional reconstruction to produce spatial and temporal patterns of gross denudation and denudation rates. The analysis reveals that all models are possible theoretically and that denudation rates lie in the lower half of the range attributed to ‘normal denudation’. The model detailed in this paper has a proposed pattern of evolution for the Central Weald that involves early Palaeogene uplift, warping and denudation, followed by slower denudation in the later Palaeogene, stimulated erosion in the Neogene due to tectonic activity, culminating with severe denudation and relief generation in the Quaternary due to uplift of up to 260 m. The Chalk downlands, by contrast, are considered to have developed from the Pleistocene exhumation and dissection of areas that evolved more slowly in the Tertiary and were dominated by low relief landsurfaces at no great elevation above contemporary summits that experienced lengthy periods of morphostasis.
What do experiments tell us about the relative contributions of crust and mantle to the origin of granitic magmas?
Authors: Patiño Douce Alberto E. 
Published: April 2008

Abstract
The origin of different kinds of granitic rocks is examined within the framework of experimental studies of melting of metamorphic rocks, and of reaction between basaltic magmas and metamorphic rocks. Among the types of granitic rocks considered in this chapter, only peraluminous leucogranites represent pure crustal melts. They form by dehydration-melting of muscovite-rich metasediments, most likely during the fast adiabatic decompression that results from tectonic collapse of thickened intracontinental orogenic belts. All other granitic rocks discussed here represent hybrid magmas, formed by reaction of basaltic melts with metamorphic rocks of supracrustal origin. These hybrid rocks include Cordilleran granites, formed at or near convergent continental margins, strongly peraluminous ‘S-type’ granites, alumina-deficient ‘A-type’ granites, and rhyolites associated with continental flood basalts. The differences among these types of granites reflect differences both in their source materials and in the pressures at which mantle-crust interactions take place. In turn, these variables are correlated with the tectonic settings in which the magmas form. Hybrid mafic cumulates are also produced by mantle-crust interactions, simultaneously with the granitic melts. These cumulates range from orthopyroxene + plagioclase-rich assemblages at low pressure to clinopyroxene + garnet-rich assemblages at high pressure, and are known to be important constituents of the lower continental crust. With the exception of peraluminous leucogranites, generation of granitic magmas is almost always associated in space and time with growth, rather than just recycling, of the continental crust.
Permo-Triassic and Jurassic extension in the northern North Sea: results from tectonostratigraphic forward modelling
Authors: Odinsen Tore , Reemst Paul , Beek Peter Van Der , Faleide Jan Inge , Gabrielsen Roy H. 
Published: April 2008

Abstract

We have undertaken 2D forward modelling across the northern North Sea, based on reprocessed, interpreted and depth-converted deep reflection seismic lines NSDP84-1 and −2 (15 s twt) and refraction data. Two separate stretching phases, Permo-Triassic and Jurassic, are recognized. The cumulative stretching is consistent with the observed crustal structure and the overall basin configuration, as reproduced by forward modelling. Good agreement between observed and modelled top basement level, and crustal thickness below the platform areas are particularly emphasized. Crustal-scale modelling indicates that crustal thickness varied across the northern North Sea at the onset of the Permo-Triassic rifting, from
c
. 35 km in the platform areas to less than 30 km in the interior of the basin. This may be ascribed to Devonian(-Carboniferous?) crustal stretching. Thinning of the crust has progressively been narrowed, from post-Caledonian extensional collapse, to less regional Permo-Triassic basins, and finally development of the Viking Graben area in the Jurassic-early Cretaceous time. Most of the Permo-Triassic stretching occurred between the Øygarden Fault Zone to the east and the Shetland Platform (southern transect) and the Hutton Fault alignment to the west. The width of the Permo-Triassic basin was
c
. 120–125 km, with calculated
β
mean
between 1.38 and 1.40. Permo-Triassic
β
mean
estimates across the present Horda Platform vary between 1.33 and 1.39. The Jurassic
β
mean
estimates for the same area vary between 1.08 and 1.13. Across the Viking Graben, Permo-Triassic
β
mean
varies between 1.28 (southern transect) and 1.41 (northern transect). This is lower than estimates for the Jurassic
β
mean
, which amounts to 1.53 and 1.42. Permo-Triassic and Jurassic
β
mean
estimates across the East Shetland Basin are 1.29 and 1.11, respectively. Lithospheric thermal evolution reflects the general differences between Permo-Triassic and Jurassic stretching, with a much wider thermal perturbation during the former and a focusing and lateral migration towards the east of the peak thermal elevation during the latter. There are still uncertainties related to the degree of (de)coupling between the upper crust and upper mantle during the Permo-Triassic and the Jurassic rift phases. These uncertainties are related to the interplay between age, strain rate, crustal rheology, crustal thickness and long-lived zones of weaknesses.
Detachments and low-angle faults in the northern North Sea rift system
Authors: Fossen Haakon , Odinsen Tore , Færseth Roald B. , Gabrielsen Roy H. 
Published: April 2008

Abstract
Several master faults in the North Sea basin tend to flatten to give low dips at depth, and in this sense form detachments in the rift system. Such low angle faults are identified in the western flank of the Viking Graben (Tampen Spur area), where they occur as both intra- and supra-basement detachments. Interference between detachments and steeper faults results in ramp-flat-ramp geometries. In the eastern part of the Gullfaks fault block, a supra-basement detachment is probably associated with anomalously high late Jurassic extension in the Gullfaks Field area. The low-angle Gullfaks detachment also helps explain the presence of sets of parallel east-dipping faults (domino systems), a common feature in the collapsed hanging wall to low-angle detachments. Similar detachments probably exist beneath the Gullfaks Sør block and SE of the Visund fault block. All of these are interpreted as late Jurassic collapse structures directly related to active late Jurassic extensional tectonics. Strong indications of intra-basement detachments are also found in the Tampen Spur area. These detachments are formed by major normal faults that flatten in the basement, as seen beneath the Visund fault block. This geometry may to some extent be related to fault rotation during repeated phases of extension in the Palaeozoic-Early Mesozoic period. However, abrupt flattening of some of the faults in the basement indicates that the master faults follow some of the many pre-existing mechanically weak zones in the basement, primarily low-angle Devonian extensional shear zones or Caledonian thrusts.
Syn-rift evolution and resulting play models in the Snorre-H area, northern North Sea
Authors: Nøttvedt Arvid , Berge Anker M. , Dawers Nancye H. , Færseth Roald B. , Häger Kjell O. , Mangerud Gunn , Puigdefabregas Cai 
Published: April 2008

Abstract
An upper Jurassic, wedge-shaped syn-rift succession, comprising the Heather and Draupne Formations, is present in the hangingwall trough of the Snorre Fault Block. The succession is bounded to the west by the Statfjord East Fault, whereas it onlaps the snorre Fault Block to the east. It consists of a two-fold coarsening-upward sequence from shale to sandstone of shallow marine/shoreline origin.
Active fault block rotation and subsidence in the Snorre-H area commenced in the Mid-Bathonian and lasted through the Ryazanian. The Heather Formation was deposited during the early rift stage (Mid-Bathonian-Early Oxfordian; 3° cumulative tilt), whereas the Draupne Formation (Late Oxfordian-Ryazanian; 9° cumulative tilt) accumulated during the main and late rift stages. The lower part of the Heather Formation was likely deposited across a submerged tilted fault block terrain, with a predominant extra-basinal sediment supply. Deposition of the upper Heather Formation, however, was governed by gradually emerging footwall islands, albeit yet without significant local erosion. As a result of increased fault/block rotation during deposition of the Draupne Formation Shale, Sequences I–II (late Early Oxfordian-early Mid-Volgian) footwall islands became firmly established, providing a predominant local sediment source to the Snorre-H sub-basin. Clay and silt were supplied from erosion of the Heather Formation on the Snorre-H hangingwall, with subordinate input of sand from the Statfjord East footwall. Subsequent deposition of the Draupne Formation, Sequences III–V (Late Mid-Volgian-Ryazanian), was governed by significant relief on the footwall islands, causing deep erosion into the Brent Group on the Snorre-H hangingwall dip-slope and leading to progradation of the Upper Draupne Sandstone shoreline complex across the Snorre-H area. Deposition of the Draupne Formation and temporal shoreline position were likely partly controlled by northwards fault-tip propagation of the Statfjord East Fault.
Various syn-rift play models and depositional reservoir facies are present within the Snorre-H hangingwall basin. They include dip-slope shallow marine/shoreline sands, basin floor gravity transported sands and likely footwall talus sands enveloped in organic rich shales of the Draupne Formation. The distribution of reservoir facies is intimately linked to exposure and erosion of the middle Jurassic Brent Group below the syn-rift unconformity.
Crustal stress and tectonics in Norwegian regions determined from earthquake focal mechanisms
Authors: Lindholm Conrad D. , Bungum Hilmar , Hicks Erik , Villagran Mario 
Published: April 2008

Abstract

A database of 109 earthquake focal mechanisms for Scandinavia and Svalbard has been compiled, comprising 29 new solutions. Stress directions extracted from these earthquake focal mechanisms have been calculated for southeastern and southwestern Norway, the Norwegian Sea and the Barents-Finnmark region. The principal horizontal stress is
c.
N45°W, and indicates a clockwise rotation as one moves from south to north, in accordance with stress trajectories that can be expected from ridge push. The data indicate that in southern Norway normal faulting regimes are more dominant in onshore regions, whereas thrust faulting dominates the offshore seismic activity. Offshore mid-Norway a preference for normal faulting is also found, whereas the shallow earthquakes in Finnmark, northern Norway, are all reverse. Focal depth distributions were studied in the northern North Sea region, revealing substantial differences with depths in the range 5–30 km.
The interplay of faulting and folding during the evolution of the Zagros deformation belt
Authors: Sattarzadeh Y. , Cosgrove J. W. , Vita-Finzi C. 
Published: April 2008

Abstract
In this short paper satellite images, aerial photographs and seismic sections are used to show that pure buckle folds, pure forced folds and folds intermediate between the two have all formed, and are still forming, in association with the compression tectonics currently occurring in the Zagros deformation belt which is situated along the northeastern margin of the Arabian plate. The type of folding and its distribution can be linked directly to the distribution of ancient basement faults and to the rheological profile of the cover sequence.
Tectonically enhanced forced regressions: examples from growth folds in extensional and compressional settings, the Miocene of the Suez rift and the Eocene of the Pyrenees
Authors: Gawthorpe Robert L. , Hall Matt , Sharp Ian , Dreyer Tom 
Published: April 2008

Abstract
This paper examines the stratal geometries and facies stacking patterns associated with forced regressions around fault-propagation folds in extensional and compressional settings. Case studies are documented from: (i) the Miocene of the Suez rift and (ii) the Eocene of the Ainsa piggyback basin, Pyrenees. Despite the different tectonic settings, the stratal geometries and facies stacking patterns are remarkably similar. Distinctive sharp-based shoreface sandstones, formed as a result of forced regression, were deposited around growth anticlines. The forced regressive shoreface sandstones ‘shale-out’ rapidly basinward away from the growth anticlines and sit abruptly within offshore mudstones of highstand (HST) and transgressive (TST) systems tracts along the flanks of the growth anticlines.
As fold amplification proceeded, older sandbodies were rotated to dip more steeply, and there is commonly a 2–5° angular difference between successive forced regressive sandbodies. This progressive tilting, coupled with marine erosion during relative sea-level fall has completely removed HST and TST deposits near anticline crets, and led to vertical amalgamation of individual forced regressive sandbodies. The resulting stratal geometries clearly result from the tectonic enhancement of forced regression.
Suprasubduction Zone Origin of the Pozanti-Karsanti Ophiolite (Southern Turkey) Deduced from Whole-rock and Mineral Chemistry of the Gabbroic Cumulates
Authors: Parlak Osman , HÖck Volker , Delaloye Michel 
Published: April 2008

Abstract

The Pozanti-Karsanti Ophiolite Complex is situated in the eastern Tauride Belt and represents a remnant of the Mesozoic Neotethyan Ocean. It consists of three distinct nappes: (1) an ophiolitic mélange; (2) a metamorphic sole; and (3) ophiolitic rocks. The oceanic lithosphere section of the Pozanti-Karsanti Ophiolite comprises mantle tectonites, ultramafic-mafic cumulates, isotropic gabbros, sheeted dykes and basaltic volcanic rocks. These units are cut by isolated microgabbro-diabase dykes at all structural levels. New results are presented on the whole-rock and mineral chemistry of the gabbroic cumulates. Well-layered, low-Ti gabbroic cumulates, showing adcumulate to mesocumulate textures, are represented exclusively by gabbronorites. The mineral chemistry of gabbronorites from the Pozanti-Karsanti Ophiolite indicates that these cumulate rocks have been produced by the low-pressure crystal fractionation of basaltic liquid. Magnesium numbers (Mg-numbers) of clinopyroxene, orthopyroxene and amphibole range from 89 to 73, 80–66 and 80–72, respectively. Plagioclase compositions range from An
94
to An
84
. The coexistence of calcic plagioclase, magnesian clinopyroxene and orthopyroxene indicates that the cumulate gabbronorites from the Pozanti-Karsanti Ophiolite were formed in an arc environment. The covariation of Al
2
O
3
and Mg-numbers of both clinopyroxene and orthopyroxene show features typical of low-pressure igneous intrusions such as the Skaergaard and Tonsina Complexes, but differ from the high-pressure ultramafic cumulates found in the same arc. The cumulate gabbronorites probably represent shallower levels in the arc which were subsequently juxtaposed against deeper level ultramafic cumulates either during accretion or later faulting.