bluuebunny/crossref_metadata_2025 huggingface dataset:
Early-Middle Palaeozoic biogeography of Asian terranes derived from Gondwana
Authors: Burrett Clive , Long John , Stait Bryan
Published: April 2008

Contiguity of the Shan-Thai Terrane and NW Australia is suggested for Cambro-Ordovician times by the close faunal affinities seen in Late Cambrian trilobites, Ordovician molluscs, stromatoporoids, brachiopods and conodonts. Taxa such as
Spanodonta
and
Georgina
are found only on these two blocks whilst others have a Shan-Thai North China, Australian distribution. This, with a re-evaluation of early Palaeozoic palaeomagnetism, places Shan-Thai against NW Australia, N China against N Australia, S China against the western Himalayan-Iran region with Indo-China and Tarim lying between S China and Shan-Thai. A palaeomagnetically required anticlockwise rotation of this greater Gondwana from the Early Cambrian to the Middle Ordovician satisfactorily accounts for the changing biogeographic patterns, in particular the differences between North and South China during the Ordovician. Recent studies on micro vertebrates and conodonts suggest that Shan-Thai was still very close to Australia in the Middle Devonian, as seen by similar turiniform thelodont species from western Yunnan, northern Thailand, and South Australia, as well as the polygnathid
P. labiosus
lineage, species of which have recently been found in Thailand. Continental fish faunas were highly endemic in South China from Silurian through to Early and Middle Devonian, indicating prolonged isolation of this terrane and separation of South China from Gondwana probably in the Silurian. In the Late Devonian, shared biotic assemblages between North China and South China (endemic Zhongning/Wuting plant flora; endemic antiarch placoderm and polybranchiaspid agnathan fishes); and between these Chinese terranes and Australia (sinolepid antiarchs, earlier appearances of certain antiarchs) indicate close continental proximity of these three major regions. New palaeomagnetic data for Ningxia, together with biogeographic data suggests that this region may have constituted a separate 'Hexizoulang Terrane'.
Silurian biogeography
Authors: Boucot A. J.
Published: April 2008

Silurian biogeography is characterized by a globally moderate climatic gradient, on which is superimposed a low latitude, warm region, moderate level of longitudinal provincialism. The cool to cold region Malvinokaffric Realm is bounded to the north by the warm water North Silurian Realm. The North Silurian Realm is divided into North Atlantic and Uralian-Cordilleran Regions. The North Atlantic Region, in turn, is divided into North American and European Provinces, whereas a Mongolo-Okhotsk Subprovince is recognized within the Uralian-Cordilleran Region. There is no biogeographic evidence favouring shallow water regions in the mid to high latitudes of the Northern Hemisphere. The nonmarine biogeography of the Silurian is largely unknown.
Rugose coral distribution as a test of Devonian palaeogeographic models
Authors: Pedder A. E. H. , Oliver W.
Published: April 2008

A data bank, based on stage by stage distributions of 420 rugose coral genera in 25 regions of the world is analysed, mostly by means of Otsuka coefficients, to test an Emsian reconstruction of the world proposed by Scotese. Devonian rugose corals inhabited a narrower range of facies than some other benthic groups, and even without regard to facies, provide a tool for testing geographic reconstructions. Basin dwelling coral genera typically have longer temporal and broader geographic ranges than corals living in shallower environments, and are less suitable for palaeogeographic studies. They are treated separately in this work.

For the most part, conclusions drawn from the analysis are either consistent with, or positively supportive of, the Scotese reconstruction. However, large but poorly known rugose coral faunas from Mongolia and the Amur Basin are at about 60° N in the reconstruction, and other well known coral faunas, from Altai-Sayan, are at 45°-50°N. In the light of known distributions of both modern corals and Devonian southern hemisphere corals, in all recently proposed palaeogeographic reconstructions, it is questionable that the original latitude of any large northern hemisphere Devonian coral fauna would have exceeded 45°.
Late Palaeozoic provinciality in the marine realm
Authors: Bambach R. K.
Published: April 2008

Biogeographic units commonly recognized in large-scale palaeontological studies are usually related to realms, not provinces as recognized in modern zoogeography. In this study the geographic distribution of the Rugosa, Tabulata, Bivalvia, Ammonoidea, Strophomenida, pedunculate Articulata, Bryozoa, and Crinoidea are used to recognize a set of realms and provinces (based on 30% or more generic endemism in the combined fauna within a province) for the Early and Late Carboniferous and Early and Late Permian. Between 12 and 18 provinces in four or five realms are identified in each interval of the Late Palaeozoic. The recently stated view than the Late Palaeozoic was a time of increasing provinciality is related to a decrease in the average range of regionally distributed genera, not an increase in either endemism or in the number of recognizable biogeographic units.
Carboniferous brachiopod migration and latitudinal diversity: a new palaeoclimatic method
Authors: Kelly P. H. , Raymond A. , Lutken C. B.
Published: April 2008

Patterns of migration of organisms, coupled with changes in latitudinal diversity, provide useful information for reconstructing palaeoclimate. We apply these tools to the record of 344 articulate brachiopod genera from the Tournaisian, Visean, and Namurian stages of the Carboniferous. Localities from the Northern Hemisphere were assigned to four palaeolatitudinal zones: the palaeoequatorial zone and the low, middle and high latitudes. Generic migrations were tabulated among latitudinal zones for each pair of successive stratigraphic intervals. Latitudinal diversity gradients were calculated based on the number of genera present within each zone.

Two intervals of climatic change were identified by these methods. Between the middle and late Visean, 42% of the genera moved the northern boundary of their range northward, and nonequatorial diversity rose dramatically. These patterns indicate high-latitude warming, which may have been caused by deflection of the circumequatorial current as the collision of Laurussia and Gondwana progressed. Migration and latitudinal diversity patterns indicate both high-latitude cooling and equatorial warming between the Namurian A and B. The onset of Gondwanan glaciation may have been responsible; similar patterns occurred during glacial onset in the Miocene.
The Palaeobiogeography of the Blastoidea (Echinodermata)
Authors: Waters Johnny A.
Published: April 2008

The 100 blastoid genera are known from some 1500 localities on every continent except Antarctica. Although fissiculates were more geographically widespread than spiraculates, the spiraculates tended to dominate most faunas numerically. The typical blastoid genus is monospecific, relatively short lived (range limited to some part of a single stage), relatively rare in terms of abundance, and geographically restricted to one depositional basin. Throughout their evolutionary history, blastoids were a component (sometimes minor, sometimes important) of echinoderm communities dominated by crinoids.

The palaeobiogeographic history of blastoids can be viewed in three phases. Phase one consisted of the initial radiation from eastern North America in the Late Ordovician, followed by an increase in diversity and geographic range in the Silurian and Devonian and culminating in a Late Devonian extinction. Phase two began with a Tournaisian (Lower Carboniferous) radiation, primarily in North America and Europe and ended in the sudden decline in blastoid diversity and abundance in the Upper Carboniferous. In phase three the biogeographic centre of the blastoids shifted eastward as the re-radiation of Upper Palaeozoic blastoids was concentrated in the Tethyan seaway not in North America and Europe. Upper Carboniferous-Permian blastoids were widespread but the most diversed faunas are found in southeast Asia and Australia.
The Don Field, Blocks 211/13a, 211/14, 211/18a, 211/19a, UK North Sea
Authors: Morrison D. , Bennet G. G. , Bayat M. G.
Published: April 2008

The Don Oilfield is located towards the western margin of the Viking Graben. It lies within four UKCS Blocks, 211/13a, 211/14, 211/18a, and 211/19a, some 15 km (9 miles) north of the Thistle Field. The field is structurally complex and consists of two discrete accumulations (Don NE and Don SW) which are separated by a WNW-ESE fault. The oil is trapped in sandstones of the Middle Jurassic Brent Group at depths of between 11 000 and 11 500 ft SS. Reservoir quality is variable with the Etive and Ness formations which contain the most productive intervals.

The Field is structurally complex and reservoir quality is highly variable. In order to minimize the impact of these uncertainties a phased development strategy has been adopted. This approach ensures the systematic reduction of risk and allows for flexibility to modify development plans as additional reservoir performance data is acquired.
The Tern Field, Block 210/25a, UK North Sea
Authors: Van Panhuys-Sigler Van M. , Baumann A. , Holland T. C.
Published: April 2008

The Tern Oilfield is situated 150 km northeast of the Shetland Islands in Block 210/25a in the UK sector of the northern North Sea. The discovery well 210/25-1 was drilled in 1975 in a water depth of about 541 ft. The trap is defined at around 8000 ft TVSS by a tilted horst-structure. The hydrocarbons are contained in reservoirs belonging to the Middle Jurassic Brent Group sands deposited by a wave-dominated delta system in the East Shetland Basin. Complex faulting of the structure is responsible for the division of the field into two areas with different original oil-water contacts: the Main Area of the field with an oil-water contact at 8260 ft TVSS, and the Northern Area with a possible oil-water contact at 8064 ft TVSS. Reservoir quality is good with average porosities ranging from 20-24% and an average permeability of 350 md. The expected STOIIP and ultimate recovery of oil are 452 and 175 MMBBL, respectively which represents a recovery factor of 39%.

The initial stage of the development plan calls for ten wells, five oil producers and five water injectors, to be drilled from a single platform, Tern Alpha. Development drilling started in February 1989 and first oil was produced on 2 June 1989. The oil is evacuated via the North Cormorant and Cormorant Alpha platforms into the Brent System pipeline for export to the Sullom Voe terminal.

To date, two producers have b een drilled and total cumulative production is 6.4 MMBBL (1 January 1990). Ultimate recovery is estimated to be some 175 MMBBL.
The Glamis Field, Block 16/21a, UK North Sea
Authors: Fraser A. R. , Tonkin P. C.
Published: April 2008

The Glamis oilfield lies within UK block 16/21a, 140 miles off the northeast coast of Scotland. The structure has the general form of an east-west oriented tilted fault block. The reservoir consists of clean sandstones of Late Kimmeridgian to Volgian age, overlain by the Kimmeridge Clay Formation but effectively sealed by Cretaceous marls. The sandstones were deposited directly on the eroded Devonian surface as the result of a late Jurassic marine transgression from the southwest.

The reservoir is subdivided into four facies: a basal conglomerate (unit 2b); an overlying fine- to medium-grained sandstone of shallow marine nearshore origin (unit 2a); a succeeding facies of coarsening upwards sandstones of barrier bar origin (unit lb), and an uppermost localized silty bar-flank transitional facies (unit la). Units 2a and lb constitute most of the reservoir section, having an average porosity of 15% and permeabilities up to 1.5 Darcies.

Glamis contains recoverable reserves of 17.5
MMBBL
of 41.5° API undersaturated oil with an initial gas/oil ratio of 1037 SCF/STB. Oil production is from two wells, 16/21a-6 and 16/21a-8, with reservoir pressure maintained by water injection in well 16/21a-17z. Dedicated flowlines exist from each of the producers to a manifold on the Balmoral floating production vessel
4
miles northeast of Glamis.
The V-Fields, Blocks 49/16, 49/21, 48/20a, 48/25b, UK North Sea
Authors: Pritchard M. J.
Published: April 2008

The Vulcan, Vanguard, North Valiant and South Valiant gas fields (collectively known as the 4 V-Fields) lie on the eastern flank of the Sole Pit Basin in the southern sector of the UK North Sea. They are contained within Blocks 49/16, 49/21, 48/25b and are operated by Conoco (UK) Limited. The first field to be discovered was South Valiant, in 1970 and exploration drilling continued until 1983 with the discovery of North Valiant, Vanguard and Vulcan Fields. Prominent faults and dip closures define the limits of the fields, and gas is contained within reservoir sands of Early Permian age, which are of desert origin. The gross average reservoir thckness is about 890 feet and porosities vary from 3-23% with permeabilities in producing zones varying from 0.1 md to 1950 md. Initial gas in place is estimated at 2.6 TCF with recoverable reserves of about 1.7 TCF. The fields were brought on-stream in October 1988 and produce, on average 325 MMSCFD of gas through the LOGGS complex to the Conoco/Britoil terminal at Theddlethorpe. Lincolnshire.
P–T–t
evolution of orogenic belts and the causes of regional metamorphism
Authors: Brown Michael
Published: April 2008

Barrow (1893) introduced three important ideas that furthered understanding of metamorphic processes: (i) the use of critical index minerals in argillaceous rocks to define metamorphic zones and elucidate spatial features of regional metamorphism; (ii) the concept of progressive metamorphism; and (iii) the concept of magmatic advection of heat as a possible cause of regional metamorphism. This article expands upon these themes by reviewing our understanding of the dynamic evolution of orogenic belts as interpreted from the
P–T–t
paths of metamorphic rocks, and by considering the likely causes of the different kinds of regional metamorphism that we observe within orogenic belts.

Understanding metamorphic rocks allows the distinction of two fundamentally different types of orogenic belt defined by relative timing of maximum
T
and maximum
P
. Orogenic belts characterized by clockwise
P-T
paths achieved maximum
P
before maximum
T
, the metamorphic peak normally post-dated early deformation within the belt and additional heating above the ‘normal’ conductive flux has been related to the amount of overthickening. By contrast, orogenic belts characterized by counterclockwise
P-T
paths achieved maximum
T
before maximum
P
, the metamorphic peak normally pre-dated or was synchronous with early deformation within the belt and additional heating above the ‘normal’ conductive flux has been related to the emplacement of plutons. Techniques used to constrain portions of
P–T–t
paths include: the use of mineral inclusion suites in porphyroblasts and reaction textures; thermobarometry; the use of fluid inclusions; thermodynamic approaches such as the Gibbs method; radiogenic isotope dating; fission track studies; and numerical modelling. We can utilize specific mineral parageneses in suitable rocks to determine individual
P–T–t
paths, and a set of
P–T–t
paths from one orogenic belt allows us to interpret the spatial variation in dynamic evolution of the metamorphism. Recent advances are reviewed with reference to collision metamorphism, high-temperature-low-pressure metamorphism, granulite metamorphism, and subduction zone metamorphism, and some important directions for future work are indicated.
Sedimentary structures: Sorby and the last decade
Authors: Allen J.R.L.
Published: April 2008

Henry Clifton Sorby pioneered in the last century the description and especially the hydrodynamic interpretation of sedimentary structures, together with their use as palaeocurrent indicators. Research completed since the last syntheses were published a decade ago shows that work along these lines continues to be necessary and relevant, particularly as regards the physical explanation of structures, and to present significant challenges and opportunities. Perhaps the most pressing needs are for a better understanding of (1) bedforms in gravels, silts and carbonate sediments, (2) tidal and especially sand-wave bedding, (3) hummocky and swaley cross-stratification, and (4) soft-sediment and dewatering structures in turbidites. Many sedimentary structures present a little-exploited opportunity to quantify process-rates and define short time-periods from the rock record.
Structure and origin of limestones
Authors: Sellwood B. W.
Published: April 2008

Sorby’s Presidential Address of 1879 on the structure and origin of limestones was essentially an interim report of research in progress. His petrographic approach to limestones, stemming from three decades of research, laid the foundations for a wide range of research lines, some of which were not fully exploited for almost a century, such as fluid inclusion studies in diagenesis. The significance of many of his discoveries (e.g. that some Jurassic ooids and Palaeozoic corals were originally calcitic) had geochemical implications that have only recently achieved research prominence (e.g. CO
2
and the ‘greenhouse’ Earth). In addition, Sorby’s legacy was the example of his peerless approach to research, applying ruthless empiricism to the problem at hand. In the case of limestones, this involved an application of meticulous descriptive petrography and innovative experimentation. His approach to understand more fully the complex problems posed by carbonates remains unsurpassed, involving a thorough integration of detailed observation, imaginative thinking and judicious use of analytical techniques.
Sediment drifts and contourite sedimentation in the northeastern Rockall Trough and Faroe-Shetland Channel, North Atlantic Ocean
Authors: Howe John A. , Stoker Martyn S. , Stow Dorrik A. V. , Akhurst Maxine C.
Published: April 2008

Seismic reflection profiles, shallow cores and seabed photography from the continental margin off NW Britain reveal the variety of bottom current influenced sedimentation in the northern Rockall Trough and Faroe-Shetland Channel. Types of sediment drifts identified include: (1) elongate drifts, both single, and multi-crested; (2) sheeted drift forms, varying from gently domed to flat-lying; and (3) isolated patch drifts, including moat-related drifts. Associated fields of localized sediment waves are developed with the elongate and gently domed, broad sheeted drifts. The contrasting style of sediment drift development reflects the complex interaction between bottom current regime, sediment supply and the bathymetry of the continental margin. The majority of the mounded/gently domed drifts occur in the northern Rockall Trough, with sheetform drifts commonly confined to the Faroe-Shetland Channel, a narrow basin which is an area of net sediment export rather than drift accumulation. Small patch drifts are present in both basins. Muddy, silty muddy and sandy contourites have been recognized from sediment cores sampling the uppermost parts of the drift sequences. Based on their glaciomarine character, the mid- to high-latitude contourites are referred to as glacigenic contourites. Both partial and complete con–tourite sequences are preserved; the former consist largely of sandy (mid-only) and top-only contourites. Modern sandy con–tourites have also been identified from seabed photographs on the Hebrides Slope. The contourites are recognized as a rippled mobile sand layer, reworked from a poorly sorted glaciomarine parent deposit.
Sediment drifts of the Corsica Channel, northern Tyrrhenian Sea
Authors: Roveri Marco
Published: April 2008

A sediment drift complex, resulting from the activity of the northward flowing Levantine Intermediate Water, occurs in intermediate water depth (300-600 m) on the eastern flank of the Corsica Basin. Because of the effect of topo–graphic constriction, bottom currents are here accelerated, reaching velocities that are sufficient to erode, transport and redistribute fine-grained sediment. The sediment drift complex shows a variety of depositional and erosional features that appear very similar to oceanic examples. The development of such features appears to be mainly controlled by an interaction between the bottom current regime and slope topography. Seismic geometries and core data show that such features have grown since middle Pliocene time under a long-term stable bottom-current regime. Short-term variability of current effi–ciency, a concept including the combined effects of current speed, sediment availability and local topography, as a result of climate and sea-level changes, is recorded by the cyclical superposition of small-scale depositional units.
The southern Weddell Sea: combined contourite-turbidite sedimentation at the southeastern margin of the Weddell Gyre
Authors: Michels K. H. , Kuhn G. , Hillenbrand C.-D. , Diekmann B. , FÜtterer D. K. , Grobe H. , Uenzelmann-Neben G.
Published: April 2008

Sedimentary processes in the southeastern Weddell Sea are influenced by glacial-interglacial ice-shelf dynamics and the cyclonic circulation of the Weddell Gyre, which affects all water masses down to the sea floor. Significantly increased sedimentation rates occur during glacial stages, when ice sheets advance to the shelf edge and trigger gravitational sediment transport to the deep sea. Downslope transport on the Crary Fan and off Dronning Maud and Coats Land is channelized into three huge channel systems, which originate on the eastern, the central and the western Crary Fan. They gradually turn from a northerly direction eastward until they follow a course parallel to the continental slope. All channels show strongly asymmetric cross sections with well-developed levees on their northwestern sides, forming wedge-shaped sediment bodies. They level off very gently. Levees on the southeastern sides are small, if present at all. This characteristic morphology likely results from the process of combined turbidite-contourite deposition. Strong thermohaline currents of the Weddell Gyre entrain particles from turbidity-current suspensions, which flow down the channels, and carry them westward out of the channel where they settle on a surface gently dipping away from the channel. These sediments are intercalated with overbank deposits of high-energy and high-volume turbidity currents, which preferentially flood the left of the channels (looking downchannel) as a result of Coriolis force. In the distal setting of the easternmost channel-levee complex, where thermohaline currents are directed northeastward as a result of a recirculation of water masses from the Enderby Basin, the setting and the internal structures of a wedge-shaped sediment body indicate a contourite drift rather than a channel levee. Dating of the sediments reveals that the levees in their present form started to develop with a late Miocene cooling event, which caused an expansion of the East Antarctic Ice Sheet and an invigoration of thermohaline current activity.
Sediment drifts and deep-sea channel systems, Antarctic Peninsula Pacific Margin
Authors: Rebesco M. , Pudsey C. J. , Canals M. , Camerlenghi A. , Barker P. F. , Estrada F. , Giorgetti A.
Published: April 2008

Twelve sedimentary mounds are identified on the upper continental rise of the Pacific Margin of the Antarctic Peninsula. All these mounds are produced by a varying degree of interaction of along-slope bottom water flow with down-slope turbidity currents. These mounds provide a complete range of intermediates between two end members: the sediment drift and the channel levee. Surface sediments on drift 7 suggest that the mechanisms for the supply and transport of sediment include entrainment of material from turbidity currents within ambient bottom currents, and pelagic settling from the sea surface, including biogenic and glacially derived material. The long-lasting activity of these mechanisms is documented by the data provided by four DSDP and ODP drill sites. Bathymetric and seismic data, both at a large, comprehensive scale and at a small, detailed scale, show the geometry of the sedimentary mounds and their relationships with the adjacent turbidity current channel systems. These data allow the determination of some diagnostic criteria to identify the sediment drifts.
The Andrew and Cyrus Fields, Blocks 16/27a, 16/28, UK North Sea
Authors: Jolley J. E.
Published: April 2008

The Andrew and Cyrus fields lie in UK Blocks 16/27a and 16/28 at the junction of the Witch Ground Graben and the South Viking Graben. The Andrew Fields was discovered in 1974 with well 16/28-1, and Cyrus in 1979 with well 16/28-4. Both fields share a common reservoir the Paleocene Andrew Formation and both are sealed by the overlying Andrew Shale and Sele Formation. Similarly the traps for both fields formed above swells within Zechstein salt. The Andrew and Cyrus Fields differ in their petroleum content. Andrew contains both gas and oil (40API) while Cyrus contains only oil (30API).

Reserves for the Andrew Field are 140 MMBBL based upon a 46% recovery factor using natural aquifer drive. The same mechanism will deliver 16.5 MMBBL from Cyrus at a 21% recovery factor. Production began from Andrew in July 1996. Cyrus production began in April 1990 using the SWOPS system until April 1992. The small field was subsequently tied back to Andrew.
The Don Field, Blocks 211/13a, 211/14, 211/18a, 211/19a, UK North Sea
Authors: Milne A. D. , Brown A. M.
Published: April 2008

abstract

Cumulative oil production to the end of 2000 from the Don Field was 15.4 MMBBLS, which with an estimated STOIIP of 152 MMBBLS represents a recovery to date of 10%. Don has been producing for over ten years. The field lics 15 km N of the Thistle Field, at the western edge of the Viking Graven in the northern North Sea. The structure of the field is complex, and it comprises several segments, the two larges of which have been developed, Don NE and Don SW. The reservoir sequence is Middle Jurassic Brent Formation. But more deeply buried and of a more distal facies than is typical for other fields in the province.

The Don Field is a sub-sea development tied-back to the Thistle platform, and Britoil (BP) is the operator. The field has been developed with five producers, three in NE andtwo is SW, with a supporting water injection well in each part of the field. All wells have been drill deviated from a seabed manifold located over Don NE.
The Harding Field, Block 9/23b
Authors: Beckly J. , Nash T. , Pollard R. , Bruce C. , Freeman P. , Page G.
Published: April 2008

The Harding Field was discovered in 1988 and lies within Block 9/23b, 320 km NE of Aberdeen, on the western flank of the Crawford Ridge. Appraisal drilling found a series of Tertiary accumulations along the Crawford Ridge, and, though most have an apparent element of stratigraphic trapping, a larger structural closure is possible. The present development comprises two heavy oil accumulations, Central and South, reservoired in massive sands of the Eocene Balder Formation. Deposited by mass flow processes, these clean and well-sorted sands have been further homogenized by post depositional remobilization and injection. There are seven horizontal producers in Central and three in South, with pressure support by water injection. Reservoir quality is exceptional, with permeability in excess of ten darcies and Pi's for the horizontal producers in excess of 1000 STB/psi. Production started in April 1996 achieving a plateau rate in excess of 90 MMSTBPD with 40% of the estimated 200 MMSTB reserves recovered in the first three years.

Four smaller Tertiary satellite pools are presently under appraisal and development by extended reach drilling from the platform.
The North Cormorant Field, Block 211/21a, UK North Sea
Authors: Bater Louise
Published: April 2008

The Cormorant Field was discovered by exploration well 211/26-1 in 1972; the fifth field to be discovered in the Northern North Sea. It straddles blocks 211/21 a and 211/26a and is made up of four discrete accumulations spread along a major N-S trending fault terrace. Oil is produced from the sandstones belonging to the Brent Group. The sedimentary rocks comprising the Brent Group were deposited in a fluvial-wave dominated delta system during the Middle Jurassic. The field is developed from two fixed platforms and an underwater manifold centre and the oil is exported through the Brent system to Sullom Voe in the Shetland Islands. For development purposes the field is split in half; north and south, and it is the northern part, developed by the North Cormorant platform, that is the subject of this review.
The Strathspey Field, Block 3/4a, UK North Sea
Authors: Maxwell G. , Stanley R. E. , White D. C.
Published: April 2008

The Strathspey Field was the first sub-sea development in the North Sea to be tied back to a third party operator, the Ninian Field now operated by Canadian Natural Resources (CNR). The field was discovered in 1975 by well 3/4-4 and lies wholly within Block 3/4a. The field is a tilted fault block, unconformity trap and consists of two separate reservoirs, a volatile oil and a gas condensate reservoir: the Middle Jurassic, Brent Group and the Lower Jurassic/Upper Triassic, Banks Group respectively. Two 3D seismic surveys cover the field, the most recent being a Vertical Cable Seismic survey recorded in 1996.

The Banks Group reservoir is produced under depletion drive by five wells and the Brent Group reservoir by water flooding with 3 water injectors and 6 producing wells. In place volumes are 290 BCF and 90MMSTB for the Banks Group and 120MMSTR in the Brent Group Reservoir. Ultimate recoveries are estimated to be 230BSCF, 22MMBBL and 70MMSTB, 88 BSCF respectively. Oil export is via the Ninian pipeline system to Sullom Voe, while gas export is through the Far North Liquids and Gas System (FLAGS) pipeline system to St Fergus.]
The Thistle Field, Blocks 211/18a, 211/19a, UK North Sea
Authors: Brown A. M. , Milne A. D. , Kay A.
Published: April 2008

Cumulative production of oil from the Thistle Field had reached almost 400 MMBBL by the end of 2000. Thistle is a success story and has been producing for over 20 years. It is now in its late stage of field life and is close to achieving a 50% recovery factor of its estimated 824 MMBBL STOIIP. The millennium challenge is to continue economic production and further increase reserves recovery. It has survived the full range of oil price fluctuations with all the accompanying cost cutting initiatives in late life becoming the benchmark for end of field life performance.
Depositional Architectures of Recent Deepwater Deposits in the Kutei Basin, East Kalimantan
Authors: Fowler J. N. , Guritno E. , Sherwood P. , Smith M. J. , Algar S. , Busono I. , Goffey G. , Strong A.
Published: April 2008

To aid exploration and appraisal of hydrocarbon discoveries in deepwater deposits of the Kutei Basin, a study of analogous sedimentary architectures in Recent deposits of the same basin was undertaken. High quality 3D seismic were used to develop an understanding of the external and internal geometry of slope to basin floor elements in a structured setting. Toe-thrust anticlines and related mud diapirs deflect slope canyons. Over slope-steps, gravity flow deposits are laterally confined with narrow facies belts. In slope mini-basins, flows are less confined resulting in deposition over a broad area. The Recent deposits of a single canyon and associated basin floor system are used to illustrate the deepwater depositional elements. Debrites at the base are followed by a slope channel complex or basin floor fan then a channel-levee complex. Large depocentres occur where gradients are low and the system switches from confined to unconfined. Erosionally confined channels feed basin floor fans at the toe-of-slope, while channels confined by levees feed fans on the 'distal' basin floor. Slope channel complexes and basin floor fans are interpreted to be sand prone. From the slope to basin floor these deposits increase in width:thickness ratio and areal extent and apparent lateral connectivity increases while vertical connectivity decreases.
3D Seismic Analysis Reveals the Origin of Ambiguous Erosional Features at a Major Sequence Boundary in the Eastern North Sea: near Top Oligocene
Authors: Hansen J. P. V. , Clausen O. R. , Huuse M.
Published: April 2008

The near top Oligocene unconformity is a major sequence boundary in the eastern North Sea Basin. It is characterized by erosional scarps below the boundary and a pronounced basinward shift in onlap above. The shift in onlap has previously been interpreted as caused by a major fall in sea level. Detailed 3D seismic analysis of a 20 by 20 km area at and basinward of the uppermost Oligocene clinoform breakpoint reveals that the erosional scarps were caused by undercutting of steep clinoforms by contour-parallel currents and resulting mass wasting whilst the lowermost onlap package consists of a contour-parallel drift deposited as the erosive currents waned. The 3D seismic analysis corroborates a recent analysis based on regional 2D seismic data, which found that the erosional scarps and the geometry of the onlap sequence were indicative of a major shift in sediment input directions and not necessarily associated with any change of sea level. The paper thus demonstrates the utility of local 3D seismic analyses as a form of 'ground truthing' regional basin analyses based on widely spaced 2D seismic grids.
3D Seismic Interpretation of the Messinian Unconformity in the Valencia Basin, Spain
Authors: Martinez Jose Frey , Cartwright Joseph A. , Burgess Peter M. , Bravo Jose Vicente
Published: April 2008

This paper documents the complex three-dimensional geometry of the Messinian Unconformity in the Tarraco concession area on the Ebro Shelf, based on the Tortuga 3D seismic survey. A detailed map of the Messinian Unconformity Surface has been constructed in the survey area, and shows a dendritic drainage pattern with valleys that are around 1 km wide, and 6-7 km in length. The overall morphology of the surface is strongly reminiscent of badlands topography, from semi-arid zone erosion of sandstone-shale sequences. The depth of incision of the valleys into the pre-Messinian clastic sequences is around 400 m. The results obtained confirm previous models of sub-aerial exposure creating erosion of the pre-Messinian shelf and slope sequences that generated the spectacular Messinian Unconformity.
Structural Evolution of a Complex 3D Fault Array in the Cretaceous and Tertiary of the Porcupine Basin, Offshore Ireland
Authors: Jones Greg , Williams L. S. , Knipe R. J.
Published: April 2008

A high-quality 3D seismic survey, located in the northwest Porcupine Basin (Irish Atlantic Margin), has been used to investigate the geometry and origin of pervasively developed and complexly distributed linked extensional fault arrays, present within Late Cretaceous and Early Tertiary sequences. The faults show a downwards transition from relatively simple, planar fault segment geometries (~N-S-trending) within younger Early Eocene sand-dominated clastic sequences, into complex conjugate arrays in the underlying older Early Eocene to Late Cretaceous shale-dominated sequences. Rectilinear to polygonal structural configurations are developed at the deeper levels. Most of the fault array ultimately terminates downwards into the Late Cretaceous, where structural accommodation may have taken place by localized or more regional bedding plane slip and/or by volume changes resulting from compaction of fine-grained sequences. Locally, reactivated Jurassic syn-rift extensional faults are locally seen to link upwards into the shallow fault array and appear to have controlled both the intensity and facing direction of the shallower faults on a km scale. The seismic data also clearly show that early upslope-throwing faults are cross-cut by later, downslope-throwing faults. Such geometries are comparable to those formed in sandbox models where gravitational collapse of a tilted sequence is the dominant process controlling fault development. Overall, the fault array geometries seen in the Cretaceous and lower Tertiary successions in this area are interpreted to have resulted from gravitational collapse processes during basin subsidence and sediment compaction, and where the main deformation mechanism was non-rigid block rotation. Differential compaction of Cretaceous and lower Tertiary sediments over pre-Cretaceous rift topography and selective reactivation of the Jurassic fault array are also considered important influences on the resultant fault distribution in 3D.
Three-dimensional geometry and displacement configuration of a fault array froma raft system, Lower Congo Basin, Offshore Angola: implications for the Neogene turbidite play
Authors: Dutton David M. , Lister Dustin , Trudgill Bruce D. , Pedro Kapela
Published: April 2008

We investigate fault growth and linkage during development of a rafted terrain in the Lower Congo Basin, offshore Angola. Miocene thin-skinned extension has led to the development of isolated raft blocks separated by a graben filled with syn-deformational strata. Angular unconformities together with thinning and onlapping of intra-raft strata onto salt bodies suggest that thick salt was mobile during thin-skinned extension. 3D fault array geometries and displacement patterns record the subsequent deformation history of the graben during further thin-skinned extension. The mode of thin-skinned extension has important consequences for the Neogene turbidite hydrocarbon play associated with the rafted province of the Lower Congo Basin. The presence of thick mobile salt will influence pre-salt source rock maturation and the development of pre-salt/post-salt hydrocarbon migration windows.

Supplementary material:
A movie of a 3D depth-converted fault model of the study area depicting the three-dimensional geometries of faulting associated with deformation of a cover sequence above a raft system is available at
https://doi.org/10.6084/m9.figshare.c.4784598
Riphean and Vendian sedimentary sequences of the Timanides and Uralides, the eastern periphery of the East European Craton
Authors: Maslov Andrey V.
Published: April 2008

The northeastern and eastern margin of the East European Craton exposes numerous Riphean and Vendian (Meso- and Neoproterozoic) sedimentary successions that were deposited in alluvial and shallow-marine environments in intra- and pericratonic basins. A review is presented of the lithostratigraphy, sedimentary environments and architectural style of these sedimentary sequences in the Southern, Middle, Subarctic and Polar Urals, on the Poludov Range, and in the Volga-Urals and Timan-Pechora regions. The Riphean sequences are subdivided into three major sedimentary units: Lower, Middle and Upper, based on type areas in the Bashkirian Anticlinorium. During the Early and Middle Riphean, in the Southern Urals there were several short episodes of ‘diffuse’ and linear rifting and long intervals of more stable development in intracratonic sedimentary basins. During the Late Riphean, in the territory under review, larger shallow marine basin developed. Two laterally connected zones existed along the eastern periphery of the East European Craton: one in the Southern and Middle Urals, with a predominance of shallow marine arkosic deposits, and the other, with moderately deep marine (continental slope and rise) turbidities in the Timan-Pechora region. Subsequent Vendian successions were largely shallow marine and deposited in epicratonic basins; they generally give way upwards in the Late Vendian into non-marine clastic formations, derived from the east.
Neoproterozoic high-grade metamorphism of the Kanin Peninsula, Timanide Orogen, northern Russia
Authors: Lorenz H. , Pystin A. M. , Olovyanishnikov V. G. , Gee D. G.
Published: April 2008

Throughout most of the exposed Timanide Orogen, the grade of regional metamorphism does not exceed greenschist facies. Only on the Kanin Peninsula and in the northernmost Timan and in a few of the drillcores that sample basement beneath the Pechora Basin, are amphibolite facies rocks present. This study presents new
P-T
estimates by garnet-biotite geothermometry and GASP geobarometry from the high-grade rocks of the Kanin Peninsula, together with a new structural interpretation of the SE-Kanin area. Thick metaturbiditic successions show an increase of metamorphic grade downwards from low greenschist to high amphibolite facies. On the SE Kanin Peninsula, peak metamorphic conditions are estimated to have reached
c.
0.72 GPa and
c.
610 °C. These inferred Late Proterozoic successions were thickened by thrust-stacking and emplaced southwestwards onto low-grade metamorphic pericratonic sedimentary rocks of the East European Craton during the Timanian Orogeny. Timing of metamorphism is inferred to be late Neoproterozoic, but radiometric ages are not well constrained and more work is needed. The new field observations and analytical results suggest that high-grade regional metamorphism is not confined to the Timan-Kanin area. This is of importance when considering the geophysical data over the Pechora Basin and Barents Sea, particularly the interpretation of crustal velocity structure. Higher velocities, often inferred to represent pre-Riphean basement, may well be related to Neoproterozoic and Mesoproterozoic complexes.
The Dzela complex, Polar Urals, Russia: a Neoproterozoic island arc
Authors: Remizov D. , Pease V.
Published: April 2008

The Neoproterozoic Dzela complex in the southern part of the Polar Ural Mountains occurs within the Uralian fault zone. It represents residual oceanic lithospheric mantle, partial melt derived from it, and seafloor basalts. In low strain domains, a depleted mantle residue of ultramafic rocks (pyroxenite, lherzolite and dunite) and mafic rocks (gabbro, gabbro-norite and quartz gabbronorite) are preserved. Distinctive negative europium anomalies in the ultramafic rocks (and their metamorphosed equivalents) indicate their residual nature after basaltic melt extraction. Gabbroic rocks (and their metamorphosed equivalents) have elevated rare earth element (REE) concentrations, but similar overall REE patterns as the ultramafic rocks that host them, suggesting that the ultramafic rocks are the source of the gabbroic melts.

Blueschist- and greenschist-facies metabasalts overlie the ultramafic and mafic rocks. Two groups of metabasalts are defined. One has NMORB-like REE patterns, but is uniformly more depleted than NMORB, and the other has slightly enriched (relative to NMORB) LREE/HREE patterns. The latter has high field-strength elements (HFSE) concentrations consistent with formation in an intraoceanic subduction zone setting.

Dzela mafic rocks have been dated for the first time to 578 ± 8 Ma (2σ) (U-Pb zircon from quartz-bearing gabbro-norite), defining a Neoproterozoic crystallization age. The complex was probably accreted to the NE margin of Baltica (
sensu lato
) during the Timanian Orogeny. Locally reset U-Pb zircon ages of about 350 Ma probably record Uralian orogenesis and recrystallization associated with high-pressure/low-temperature metamorphism. The Dzela complex provides further evidence that ocean-continent collision was the driving mechanism for Timanian Orogeny.
The Precambrian rocks of Novaya Zemlya
Authors: Korago Eugene A. , Kovaleva Galina N. , Lopatin Boris G. , Orgo Vladimir V.
Published: April 2008

Neoproterozoic and perhaps older metamorphic and igneous rocks in the Novaya Zemlya Archipelago are exposed in four main localities. On the South Island of Novaya Zemlya (the Southern Domain) largely metasedimentary, low greenschist facies, pelitic and flyschoidal formations, dated by acritarchs as late Riphean-Vendian occur; they are intruded by metagabbro-dolerites and lamprophyres. These rocks are overlain by Ordovician strata with sharp, angular unconformity and are therefore considered to be products of Timanian (Baikalian) tectonogenesis. On the southern part of the North Island (the Central Domain), metamorphic rocks of high greenschist to amphibolite facies are preserved which are partly migmatized and comprise metasedimentary and igneous rocks; their contact with Palaeozoic strata here is tectonic. Isotopic age determinations on metasediments and igneous rocks vary from 1550 to 598 Ma and are not yet conclusive. These relatively highly metamorphosed formations may be older than Neoproterozoic. A Neoproterozoic (late Riphean) age was determined for the Mitushev Kamen‘Granite Massif, which is located within the Main Novozemel’sky thrust zone. On the northern part of North Island, (the Northern Domain) Neoproterozoic strata (mainly turbidites) of low greenschist facies pass conformably up into Cambrian and younger strata.

A major NW-trending fault (the Baidaratsky fault zone) is believed to separate the Southern Domain from Central and Northern Domains. It is concluded that the southern area is a peripheral part of the Neoproterozoic Timanian (Baikalian) fold belt. Further to the NE across the Baidaratsky fault zone, lies a broad area of possibly older basement, including the Central and Northern Domains of Novaya Zemlya and possibly the Franz Josef Land Archipelago.
Early Palaeozoic unconformity across the Timanides, NW Russia
Authors: Bogolepova O. K. , Gee D. G.
Published: April 2008

The Lower Palaeozoic sequences, unconformably overlying the Timanides of Timan, Pechora, Pai-Khoi, Vaigach, Novaya Zemlya and the Polar, Northern, Middle and Southern Urals are described and interpreted with regard to their stratigraphy, sedimentation, structure and biogeography. These mainly shallow marine sedimentary successions, with associated igneous rocks (largely alkaline), are Ordovician in age, reaching back into the Late Cambrian in some areas, particularly in the east, along the front of the Urals. They were deposited during rifting of Baltica’s northeastern margin and subsequent development of a passive continental margin. The underlying, mainly Neoproterozoic basement of turbidites in the west and calc-alkaline volcanites and ophiolites further east are briefly referred to, with particular emphasis on the age of the youngest rocks. Based on these data, a Timanian orogenic belt can be traced along the northeastern and eastern margin of the East European Craton. The timing of orogeny can be constrained to the Vendian, perhaps extending into the Early Cambrian.
Late Cambrian relative age constraints by acritarchs on the post-Timanian deposition on Kolguev Island, Arctic Russia
Authors: Moczydłowska M. , Stockfors M. , Popov L.
Published: April 2008

Platformal sedimentary successions, inferred to overlie folded Neoproterozoic basement complexes and the post-Timanian unconformity, were studied in the Bugrino 1 and North-Western 202 boreholes on Kolguev Island, southern Barents Sea. They yielded diverse, age-diagnostic acritarchs and some shelly fossils. The Upper Cambrian strata, referred to the
Peltura
and
Acerocare
zones, are recognized by means of acritarch taxa known from the East European Platform and other areas in Baltica, Avalonia, and Gondwana. Shelly faunas of brachiopods, phyllocarid crustaceans and problematic molluscs are indicative of the Tremadoc and Arenig stages in the upper part of the succession. The boreholes did not reach the Timanian unconformity and older Cambrian strata may be present. Within the area of the Pechora Basin, Cambrian strata have been identified with certainty only on Kolguev Island. Further east in the Polar Urals, Upper Cambrian strata are present and Lower or Middle Cambrian and Vendian strata have been claimed, though not yet proven. They are reported from several localities, but the fossils are poorly documented. The biostratigraphic evidence and facies development indicate that Upper Cambrian deposits may have been distributed widely along the northeastern margin of Baltica, as they were on the East European Craton and in Baltoscandia.