bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of glacigenic sedimentation on slope-apron development on the continental margin off Northwest Britain
Authors: Stoker M. S. 
Published: April 2008

Abstract
The Hebrides and West Shetland shelves were extensively glaciated on several occasions during the mid- to late Pleistocene, with grounded ice locally reaching the shelf edge and depositing vast amounts of sediment directly on to the adjacent slopes. On the Hebrides Slope, the discrete, slope-front depocentre of the Sula Sgeir Fan has accumulated a thick (200 m) succession of interbedded debris-flow diamictons, turbidite sands and muds. This contrasts with a ‘between fan’ area to the south, where a thinner (< 100 m) sediment drape of glaciomarine ice-rafted and suspended sediment, deposited partly under the influence of alongslope currents, is preserved. On the West Shetland Slope, the slope-apron may consist of several coalescing wedges of sediment which form a laterally more extensive, albeit thinner (up to 100 m) succession of mass flow deposits. On both slopes the glacigenic deposits can be separated into discrete mass-flow packages bounded by thin, occasionally slope-wide, prograding clinoforms. Accumulation of these packages was episodic and related to specific rapid phases of downslope sedimentation, concomitant with maximum glaciation and glacio-eustatic lowstand. The thin clinoform units reflect intervals of reduced sediment supply to the slope. The ‘between fan’ area of the Hebrides Slope has been a region of relatively persistent sediment bypass.
Analagous deposits preserved on other mid to high-latitude continental margins, such as the East Greenland, Barents Sea and East Canadian margins, highlight the regional importance of glacigenic processes to late Cenozoic slope-apron development in the North Atlantic region. In particular, they demonstrate the influence that climate can have on the stratigraphical and sedimentological record.
Petrography and biostratigraphy of Palaeogene volcaniclastic sediments dredged from the Faeroes shelf
Authors: Waagstein Regin , Heilmann-Clausen Claus 
Published: April 2008

AbstractA large number of dredge hauls made on the outer shelf and slope east of the Faeroe Islands have yielded Lower Tertiary sedimentary rocks (bothin situand glacially transported). The rocks have been examined petrographically and biostratigraphically (dinoflagellates), and they are all considered to be derived from the Faeroe shelf. They can be classified according to sediment type and chronostratigraphy in the following groups: (1) Lower Eocene basaltic tuffs (dominantly non-marine); (2) Lower and Middle Eocene tuffaceous limestones and phosphatic sediments; and (3) Lower and possibly Upper, Oligocene fine-grained feldspathic volcanic sandstones. Two dredge hauls of local till near the shelf edge west of the Faeroe Islands gave coarse to fine grained volcanic sandstones of Oligocene age.The basaltic tuffs of the eastern shelf bear witness to a major phase of explosive volcanism succeeding the extrusion of the Faeroe lava plateau. Whole-rock chemical analyses suggest that the explosive magmas had a tholeiitic composition rich in iron and titanium. Some of these eruptions are likely to be represented among the tuffs of the Balder Formation in the North Sea. After the deposition of the tuffaceous sediments in a marine setting during the Early and Middle Eocene the central parts of the Faeroe basalt plateau were probably uplifted in the Bartonian or Priabonian. As a result of erosion of the basalt plateau and overlying sediments volcanic sandstones (often rich in reworked dinoflagellates) were deposited in a marine environment during the Early Oligocene.
Tertiary structuration and erosion of the Inner Moray Firth
Authors: Thomson K. , Hillis R. R. 
Published: April 2008

Abstract
Seismic profiles and field data show that the Inner Moray Firth (IMF) experienced significant structural modification during Early Tertiary times with the development of inversion, strike-slip and extensional oblique-slip geometries as well as uplift and erosion at a mid-late Danian unconformity. Seismic reflection profiles across the IMF also show progressively older stratigraphic subcrop towards the west. Analysis of sonic velocities and vitrinite reflectance demonstrate that up to 1.5 km of basin fill has been removed from the IMF. The height of the sequences above maximum burial depth (apparent erosion) is at a maximum in the northwestern part of the basin, where inversion geometries are found, and decreases to zero in the Outer Moray Firth. However, if post-erosional burial is taken into account, the actual amount of erosion during Early Tertiary exhumation (total erosion) is shown to be more evenly distributed, and of greater magnitude throughout the IMF. Incorporation of the effects of Tertiary erosion into analysis of basin development requires much greater post-rift burial than if Tertiary erosion is ignored. It seems most likely that the Early Tertiary deformation of the IMF occurred in response to NE Atlantic (Thulean) and Alpine events.

Late Cretaceous-Early Tertiary times saw the change of the predominant stress field of North West Europe from one of extension to one of NW-SE compression (Ziegler, P. A. 1987,
Tectonophysics
,
137
, 1–5 & 389–420). The present-day stress field of Western Europe is described by a NW-SE direction of maximum principal stress (Müller, B.
et al.
1992,
Journal of Geophysical Research
,
B97
, 11 783–11 803). The present-day-, and by inference palaeo-, intraplate stress field of Western Europe can be attributed to plate-driving forces acting on the boundaries of the Eurasian plate. On average, the orientation of present-day maximum stress in western Europe is subparallel to the direction of relative plate motion between Africa and Europe (Müller, B.
et al.
1992,
Journal of Geophysical Research
,
B97
, 11 783–11 803). A combination of stresses associated with Alpine collision between Europe and Africa, and those associated with opening of the North Atlantic are considered responsible for the Late Cretaceous-Early Tertiary NW-SE compressional stress field of North West Europe.
Structural and tectonic setting of the Permo-Triassic basins of northwest Europe
Authors: Coward M. P. 
Published: April 2008

Abstract
The Permo-Triassic basins of NW Europe formed by (i) late-orogenic spreading of the Variscan mountain belt, eventually leading to ocean floor formation in the Mid-Atlantic, (ii) continental rifting propagating south from the Arctic and (iii) thermal subsidence following Carboniferous volcanic activity in the North Sea. Spreading values in the northernmost North Sea, west of Shetland and west and southwest of Britain, are relatively high but the sediments are dominantly continental; the Permo-Triassic rifting affected lithosphere thickened during Caledonian and Variscan orogenesis. However, subsidence associated with the Arctic rifting, together with global sea level changes, allowed marine incursions into the North Sea, producing the large Zechstein salt basins. Interference of the different basin formation mechanisms led to a complex three dimensional fault pattern and multidirectional extension across Britain and the North Sea. This fault pattern formed the basic framework for subsequent Jurassic and Cretaceous basin formation.
Influence of basement on the geometry of Permo-Triassic basins in the northwest British Isles
Authors: Anderson T. B. , Parnell J. , Ruffell A. H. 
Published: April 2008

Abstract
The orientation and shape of Permo-Triassic basins in the northwest British Isles are strongly influenced by the structure of the underlying basement. In the Hebridean region, NE-SW-elongated basins are controlled by reactivated Caledonian thrusts. Further south, the variable orientation of elongate basins reflects the local fabric of the Dalradian basement. In the Midland Valley of Scotland and Northern Ireland, Permo-Triassic basins have a less regular shape, as they are sited on Carboniferous basins with a weakly pronounced structural fabric: the NNW-SSE-elongation of some outcrops reflects the effects of later (Tertiary) faulting along this trend. In the Southern Uplands lower Palaeozoic basement, bedding and cleavage are tectonically aligned to produce a strong ENE-WSW high angle anisotropy, cross-cut by complicated arrays of steeply inclined faults. Crustal stretching would have occurred normal or parallel to the anisotropy: Permo-Triassic basins, typically elongate NNW-SSE, clearly formed in response to contemporary ENE-WSW stretching, producing half-graben by dip-slip reactivation of existing Caledonian fractures.
New evidence of Permo-Triassic rifting, onshore southern Ireland, and its implications for Variscan structural inheritance
Authors: Keeley M. L. 
Published: April 2008

Abstract

Reconnaissance apatite fission track analysis data from onshore southern Ireland are used to construct a thermal history for Late Palaeozoic rocks. The data show clear evidence of post-Variscan heating. The most significant thermal event took place during the Permo-Triassic, and resulted from not less than 1 km of regional subsidence. Late Palaeozoic rocks were again uplifted and exposed during the Early Jurassic. Significant deposition did not resume until the Late Cretaceous, and was followed by uplift and inversion emanating from the North Celtic Sea Basin. Repeated post-Variscan extension and compression of the Variscan basement must therefore have taken place, making it now difficult to differentiate
bona fide
Variscan deformation. However, the northern extent to both Permo-Triassic and Late Cretaceous sedimentation was probably controlled by extension along a line of major Variscan thrusts in south-central Ireland — the South Ireland Lineament.
The Variscan fold-thrust belt of southeast Ireland and its control on early Mesozoic extension and deposition: a method to predict the Sherwood Sandstone
Authors: Musgrove F. W. , Murdoch L. M. , Lenehan T. 
Published: April 2008

Abstract
The Sherwood Sandstone Group (SSG), of Early Triassic Scythian age, contains attractive fluvial and aeolian sandstone reservoirs in the basins between Ireland and Britain (Morecambe Bay gas field, 6.5TCF) and in southern England (Wytch Farm oil field, 300 MMBBL). While the SSG is very thick in the northern portions of the Mesozoic basin system, it is thinner and generally less well preserved in the southern portions of the Mesozoic basin system which are underlain by the Carboniferous aged Variscan fold-thrust belt. Previously it has been suggested that the SSG was deposited during a time of rifting, and consequently its variable presence was attributed to wells penetrating positions within fault blocks that were high and devoid of syn-rift deposition. Data examined in this study from the East Irish Sea Basin and from the South Celtic Sea Basin, however, suggest that the SSG was deposited in palaeotopographic lows, the positions of which were controlled by erosion around massifs and resistant thrust belt hangingwalls that formed the palaeotopography. Furthermore, the evidence presented suggests that rifting occurred during the deposition of the Upper and Middle Triassic Mercia Mudstone Group (MMG), which is often defined as a post-rift succession.
Successful prediction of the areas of SSG deposition depends on the ability to reconstruct the Early Triassic palaeotopography as it was controlled by the Carboniferous thrust belt morphology. A reconstruction of the Variscan thrust belt is presented, which is based on onshore surface geology, thrusts and transfer faults from published onshore mapping, published offshore thrust plane reflector mapping, gravity data showing lineaments and indications of granite plutons, and a set of observations from well and seismic data. Some thrusts are postulated by observations of reactivation during Mesozoic extension.
A set of predictive tools has been developed for identifying the presence of the SSG. Determination of the presence of the SSG on seismic reflection data is often difficult. Where the data quality is poor, we postulate that there is a better chance of finding the SSG where halites are found in the overlying MMG. This empirical relationship is believed to occur because rifts developed over SSG foreland and intermontane valleys were near sea-level, allowing marine incursions and salt precipitation. By contrast, rifts that developed in high topographic areas were above sea-level and not subject to marine incursion. Additionally, the degree of deformation seen in the pre-Triassic section on seismic data can be used to predict the position of the Variscan Front and thus the topographically low, sand-prone areas overlying the Carboniferous foreland basin. A palaeogeographic map is presented, incorporating the analysis of all of these datasets and utilizing a comparison to the topography of the exposed Ouachita Mountains of the southern USA.
Sedimentology and diagenesis of the Jurassic and Cretaceous of the North Celtic Sea and Fastnet Basins
Authors: Ewins Nuala P. , Shannon Patrick M. 
Published: April 2008

Abstract
The North Celtic Sea and Fastnet Basins both contain a relatively complete Jurassic and Cretaceous section. These sediments were examined in order to gain an insight into the nature and extent of sedimentological and diagenetic processes which affected the basins. Significantly variable depositional environments existed in the basins through time. The Early and Middle Jurassic were dominated by low-energy marine conditions, below storm wave-base, with higher-energy storm events locally depositing coarse-grained sediments. The Upper Jurassic succession contains sediments deposited in marine, marginal marine and continental environments, with significant quantities of coarse-grained material. Lower Cretaceous sediments were initially characteristic of marginal marine to continental conditions but increasing marine influence resulted in deposition of fully marine sediments. Three sequences were examined petrographically, concentrating on those considered to have potential for reservoir development. In general, porosity and permeability appear to be principally related to primary depositional factors, or to the control of these primary factors on the subsequent diagenetic evolution. Quartz cementation appears to have been the most destructive in terms of porosity occlusion, but locally, calcite cements are significant. Significant reservoir potential is considered to remain in the three sequences examined in the area, with good sandstone development postulated in undrilled areas.
Toarcian source rock potential in the North Celtic Sea Basin, offshore Ireland
Authors: Murphy N. J. , Sauer M. J. , Armstrong J. P. 
Published: April 2008

Abstract
Conditions favourable to the development and preservation of rich oil-prone source rocks are demonstrated for the uppermost Lower Jurassic stage, the Toarcian, in the Irish Sector of the North Celtic Sea Basin (and adjacent South Celtic Sea Basin), located offshore to the south of Ireland. An integrated approach, involving geological and geochemical data and techniques, has permitted the quantification of source rock potential. Wireline log responses in conjunction with existing geochemical analyses have defined net thickness, quality and richness for potential source beds. Up to 450 ft of very good to rich source rocks, capable of generating liquid hydrocarbons, are calculated for marine claystones of Early and Middle-Late Toarcian age. The thickest and best quality source rocks are predicted to occur in Toarcian depocentres, mostly situated along the axis of the North Celtic Sea Basin. One-dimensional burial history modelling suggests that substantial quantities of hydrocarbons were expelled from basinal areas towards the end of the Cretaceous.
The Helvick oil accumulation, Block 49/9, North Celtic Sea Basin
Authors: Caston V. N. D. 
Published: April 2008

Abstract

The Helvick oil accumulation in Block 49/9 is situated within the northern margin of the North Celtic Sea Basin. It was discovered by well 49/9-2, drilled in 1983, which tested a cumulative total of 9901 BOPD and 7.44 MMSCFD from four reservoir intervals. These consist of marine limestone of Bathonian age, and an overlying series of Middle to Upper Jurassic age sandstones deposited in a continental/fluviatile environment. The principal ‘Main Sand’ reservoir, which flowed at a rate of 6467 BOPD, lies close to the base of the non-marine sequence and was deposited by a high-energy, braided fluvial system. It is laterally extensive and may be correlated for a minimum east-west distance of 6.5 km. Oil in the Main Sand is 44.06° API with a GOR of 680 SCF/BBL; it is derived from a predominantly herbaceous, terrestrial source which is identified, on regional evidence, as being most likely of Liassic age. The oil-water contact has not been positively established. Calculations based upon RFT and DST pressure measurements give a range of possible oil-water contacts, and hence a corresponding range of oil-in-place values. These range from 8.4 to 12.3 MMBO, with a ‘most likely’ figure of 10.7 MMBO. Reservoir simulation studies indicate potential recoverable reserves in the Main Sand of 2.27–4.42 MMBO. An additional ‘most likely’ figure of
c.
3 MMBO oil-in-place may be present within the underlying Bathonian Limestone, of which
c.
0.6 MMBO may be recoverable. Further, as yet unquantified, reserves are present in the other Upper Jurassic oil-bearing sandstones.
Westline: a deep near-normal incidence reflection profile across the Rockall Trough
Authors: England Richard W. 
Published: April 2008

Abstract
Westline is a 450 km long, near-normal incidence, deep seismic reflection profile crossing the Rockall Trough. The profile was shot perpendicular to the edges of the trough in order to image its conjugate margins. An interpretation of the brute stack of the normal incidence data, partly constrained by existing near-normal incidence and wide angle-data, reveals that the trough is asymmetric, with a broad faulted margin on its western edge and a steep faulted margin where it meets the Irish Shelf. A sill complex extends the whole width of the trough within the 5 km thick sedimentary infill.
Basin development and petroleum prospectivity of the Rockall and Hatton region
Authors: Shannon P. M. , Jacob A. W. B. , Makris J. , O’Reilly B. , Hauser F. , Vogt U. 
Published: April 2008

Abstract
The Rockall region, offshore west of Ireland, contains a number of large, virtually unexplored, frontier sedimentary basins: Rockall Trough, Hatton Basin and Hatton Continental Margin. It is suggested that the sedimentary section, up to 6 km thick, is of Late Palaeozoic to Tertiary age. Normal incidence reflection seismic data from the region are typically of poor quality owing to the effects of shallow Tertiary sills. Recent wide-angle reflection seismic profiles have helped to resolve the basin geometry and structural setting. Backstripping (reverse modelling) and forward modelling of the wide-angle model are consistent with development in a complex multi-phase rift setting. Rift events are suggested in the Jurassic and Cretaceous, and possibly locally during the Permo-Triassic. The variation in structural style across the region is interpreted as resulting from the interplay of intraplate stresses, magmatic underplating, thermal doming and thermal subsidence adjacent to the continent/ocean margin, and seafloor spreading dynamics in the region to the west. The basins are predicted to contain a range of petroleum plays. Structural, stratigraphic and combination traps are indicated from a range of data. Reservoirs are predicted at several levels, with source rocks in the Jurassic and lowermost Cretaceous.
Characterization of deep marine clastic systems
Authors: Hartley Adrian , Prosser Jeremy 
Published: April 2008

Abstract
Sandstones deposited in deep marine environments form important hydrocarbon reservoirs in many basins throughout the world. However, despite the plethora of outcrop studies and the development of numerous submarine fan models and classification schemes, very few applied studies at a reservoir scale have been published.
This publication has arisen from the perceived needs of the academic and industrial communities to understand the controls on the architecture and geometry of deep marine clastic reservoirs. A number of areas of concern have been addressed: (1) Are conceptual models applicable to understanding sandstone body development and distribution at a reservoir scale? (2) Do we understand the processes that are active in the formation of deep marine clastic systems and the likely influence of these processes on reservoir quality? (3) How do we correlate and at what scale do correlation mechanisms work within and between deep marine clastic reservoirs? (4) How can we quantify heterogeneity and reservoir quality within these reservoirs?
Experimental study of subaqueous fan development
Authors: Ouchi Shunji , Ethridge Frank G. , James Edward W. , Schumm S. A. 
Published: April 2008

Abstract
Subaqueous fan-shaped depositional forms were developed during flume experiments, that were conducted to investigate processes of underwater deposition. The flume was filled with fresh water, and clay plus salt water was introduced as a density flow at the head of the underwater slope. A lobe-shaped sandbody (sand lobe) migrated downslope, as a liquified flow, when sand was mixed into the clay plus salt water flow. In a steep-slope experiment (37°) sand lobes were deposited at the toe of the slope and overlapped each other to form a fan-shaped body. Without sand, clay plus salt water flows of small discharge, which showed characteristics of laminar flow, tended to incise a channel on the sandy fan surface. The larger discharge flows, in which some turbulence developed, however, spread into the overlying water body and did not cut a channel. Clay moved further and was deposited on the basin-floor. Sand lobes occasionally migrated on to the basin-floor clays, especially when an incised channel developed on the fan surface. When sand lobes reached the basin-floor clay deposits, movement of the sand accelerated basinward, the sand lobe slid on the clay like the floating plug of a debris flow, and formed crescent-shaped mounds and hummocky topography. The accelerated movement of the distal portion of the sand lobes appeared to cause them to become detached from the main sandbody. With gentler slopes (18°), clay deposition occurred on the slope. Sand moved in the form of an elongate lobe, and the fan itself became more elongate than the one developed on the steeper slope. The elongate nature of the fan deposit on the low slope was apparently related to the higher efficiency of sand movement on the clay that settled on this slope.
Subaqueous fans, on both slopes, collapsed and generated relatively large subaqueous debris flows when the water in the flume was being drained. The failure started on the surface with a fluidized flow, and the entire fan slumped basinward. A reduction of hydrostatic pressure caused by the lowering of the water levels apparently generated a pore-pressure gradient in the deposits. The fan slopes became unstable and pore water probably flowed upward as the pressure gradient developed. This pore-water flow induced the fluidized flow on the surface and then the slump of the entire fan.
The experimental subaqueous fans cannot be compared quantitatively with natural fans because they are not scale models. The general similarity of process, however, might provide insights into depositional and erosional processes in natural systems.