bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Devonian period
Authors: Friend Peter Furneaux , House Michael Robert 
Published: September 2007

Summary
A review of the radiometric evidence suggests that the top of the Devonian should be dated at about 345 m.y. and the base of the system at about 395 m.y. Using cumulative thickness methods the age of the base of the Upper Devonian is estimated at 358 m.y. and that of the base of the Middle Devonian at 370 m.y. Famennian ammonoid species zones must each represent about a million years. Suggestions are made as to where future radiometric work of importance to the time-scale might be undertaken.
The role of the Department of Energy in petroleum exploration of the United Kingdom
Authors: Walmsley P. J. 
Published: September 2007

Summary
Three Divisions of the U.K. Department of Energy have responsibility for petroleum. Oil Division handles policy including Licence administration. Gas Division handles gas policy. All technical matters relating to exploration, development and safety are handled by Petroleum Engineering Division (PED). Their role is to advise Ministers on exploration and development policy and to carry out the policy so decided.
Exploration Branch of PED has three sections: Geological, Geophysical and the Well Record Centre. To advise Ministers, Exploration Branch requires a comprehensive knowledge of U.K. geology and prospects. All data received from operators is passed on a confidential basis to the hydrocarbons Unit of the Institute of Geological Sciences where the review work is carried out on the Department’s behalf. Exploration Branch recommends areas for licensing, interviews applicants to determine their suitability as licensees and negotiates work programmes with selected applicants. Additional responsibilities include technical appraisal of fields, the determination of field boundaries for tax purposes and the estimation of reserves.
Exploration Branch works closely with the Development, Projects and Administration Branches of PED in the approval of development plans and field monitoring. The Safety, Pipelines, Diving and Research Branches of PED play an active role in the control of exploration and development operations.
Exploration of the Norwegian Shelf
Authors: Rønnevik Hans , Eggen Svein , Vollset Jan 
Published: September 2007

Summary
The drilling activity on the Norwegian Shelf has reached a level of more than 40 wells per year. Exploration licensing has taken place in seven rounds. The success rate on the Norwegian Shelf are very high both in the North Sea and area to the north.
In the North Sea three exploration models are established, the Chalk play, the Lower Tertiary deep sand play and Jurassic and older pre unconformity sand. Common for all the plays are Jurassic source rocks. In the north the established play types are related to pre unconformity Jurassic-Upper Jurassic sand.
Stratigraphy and Sedimentation of the Palaeocene Sands in the Northern North Sea
Authors: Mudge D. C. , Bliss G. M. 
Published: September 2007

Summary
The Palaeocene of the North Sea basin between 58°N and 62°N contains a number of reservoir sands. The regional tectonic setting, which was dominated by subsidence in the Viking Graben and Witch Ground Graben areas had an important influence on the thickness and distribution of the Palaeocene sands. Following deposition of the Danian, middle Palaeocene sedimentation was controlled by uplift and faulting along the flanks of these areas with large quantities of sand being shed off the East Shetland Platform. These sands were deposited in a nearshore shallow marine environment. With a decrease in tectonism, late Palaeocene deposition was dominated by the outbuilding of a delta system in the Moray Firth area with the northward spread of sands along the edge of the East Shetland Platform. At this time, the basin became increasingly cut off from open marine circulation. The top of the Palaeocene is marked by a regional unconformity representing a late Palaeocene-early Eocene transgression which affected much of northwestern Europe.
Aspects of Burial Diagenesis, Organic Maturation and Palaeothermal History of an Area in the South Viking Graben, North Sea
Authors: Pearson M. J. , Watkins D. , Pittion J-L , Caston D. , Small J. S. 
Published: September 2007

Summary
A detailed study has been made of changes in interlayered clay minerals, sediment mineralogy, vitrinite reflectance, kerogen composition, and chemistry of the soluble organic extract through Well 16/22-2 in the South Viking Graben. The well sampled sediments range in age from Oligocene to, at total depth, Middle Jurassic (Dogger).

Lithologies are typical of the South Viking Graben/Central Graben area with Upper Jurassic black pyritic shales, a thick Cretaceous chalk succession and prominent top Palaeocene tuff. Sandstones are common only in the Upper Jurassic Palaeocene and Eocene. Tuffs are sporadically present in the Middle Jurassic. Randomly interlayered illitesmectite is the dominant clay mineral through the Tertiary and Cretaceous and the change to an ordered structure which occurs just above the Jurassic/Cretaceous unconformity is interpreted as a diagenetic reaction. Estimates of illite-smectite composition indicate a reversal to smectite rich clays in the Lower Eocene-Top Palaeocene which is attributed to an insufficient supply of K
+
from detrital feldspar and mica due to the dominance of basic volcanic weathering products.

The vitrinite reflectance profile for this well indicates progressive maturation of kerogen to marginal maturity in the Upper Jurassic. A large jump of 0.2% R
o
occurs at the Upper/Middle Jurassic boundary below which kerogen maturity is at the peak oil-generating stage. This maturation break is supported by an increase in spore colour index. Chemical parameters are strongly influenced by a change in kerogen type from mixed algal and humic to predominantly humic at this stratigraphic level. Very high heat flow due to localized intrusive igneous activity during the late Middle Jurassic is thought to have caused the increased maturity of the Middle Jurassic sediments.
Kerogen Types, Organic Maturation and Hydrocarbon Occurrences in the Moray Firth and South Viking Graben, North Sea Basin
Authors: Fisher M. J. , Miles Jennifer A. 
Published: September 2007

Summary
Kerogen typing and maturation studies have been conducted in order to rationalise the variations in hydrocarbon types observed in the Moray Firth and South Viking Graben in the U.K. North Sea. The distribution of terrestrially-derived kerogen follows accepted models for water-borne transport. The occurrence of amorphous debris of algal origin in significant amounts is related to variations in the environment of deposition. Although the relationship between the major kerogen groups and their range of hydrocarbon product is established, the type and quantity of generated hydrocarbons could only be predicted from organic facies if the maturity of the source rocks were known. Maturity maps were therefore constructed from thermal gradients, burial histories and measured maturity (spore colour). The resulting predictive model of the distribution of oils, condensate and gas correlates favourably with observed hydrocarbon occurrences and is now an integral part of Britoil’s ongoing exploration programme.
Geochemistry of North and South Brae Areas, North Sea
Authors: Reitsema R. H. 
Published: September 2007

Summary
The Brae area of the North Sea has at least two types of crude oils present. Kimmeridgian shales are the source for both oils. The geologic setting, based on a fan delta model, is similar for both and, as expected, the oils are similar in many ways. No significant differences appear in maturity, carbon isotopic ratios or gas chromatographic analyses. The oils can be distinguished, however, by use of multiple geochemical parameters. Quantities and various ratios of pristane, phytane, normal paraffins and gasoline range components are characteristic for each area of Brae. Relative amounts of saturates and aromatics and GC/MS patterns are also useful characterization methods.
The Search for Petroleum in Northern Ireland
Authors: Griffith A. E. 
Published: September 2007

Summary
Although a considerable amount of exploration is currently taking place in Northern Ireland and in the Republic of Ireland, no commercially exploitable petroleum has yet been found on land.
Interest in searching for petroleum in Northern Ireland is relatively recent. In 1957 a number of small American oil companies became interested in the prospects in the South of Ireland and after encountering small flows of gas in two wells drilled in the Carboniferous, exploration was extended to include parts of N. Ireland.
This paper outlines the geological mapping and drilling programme which has been undertaken by the Geological Survey of N. Ireland and which has recently accompanied by experimental vibroseis surveys, some over the Tertiary basalt outcrop. It is hoped that these studies will establish the geological framework to facilitate further petroleum exploration. In particular, the prospect that petroleum sourced by Carboniferous strata, underlying extensive Mesozoic and Cainozoic outcrops in the NE of Ireland will be considered.
Origins of Natural Gas in the Po Valley, N. Italy
Authors: Mattavelli L. , Ricchiuto T. , Grighani D. , Schoell M. 
Published: September 2007

Summary
A study on natural gases sampled from 48 gas fields in the Po Basin is reported. A total of 155 wells are involved in the present work, representing 90% of the total original gas in place. The chemical and isotopic analyses have been considered based on the regional geological setting.

A correlation between chemical and isotopic composition is shown by the presence of pure and isotopically light methane (13C from −76 to −60 parts/10
18
) in the Plio-Pleistocene fields and by gas less depleted in 13C (13C from −60 to −30 parts/10
18
) and associated with heavier hydrocarbons in Miocene and Mesozoic gas fields.

No relationship exists within the Tertiary sequences between depth and isotopic composition.
The organic matter of the Tertiary sequences is mainly of terrestrial origin and is immature down to 5000 m.

On the basis of these data it is possible to distinguish three types of methane in the Po Basin:

(1)

Biogenetic and/or diagenetic gas (80% of the original gas in place) from Tertiary reservoirs, originated
in situ
from terrestrial immature organic matter of the Tertiary sequence themselves.

(2)
Thermogenetic gas (10% of the original gas in place) which migrated from more than 5000 m depth, associated with heavier hydrocarbons.

(3)
Gas of mixed origin (10% of the original gas in place).

The areal distribution and the amount of the three types of methane are strictly controlled by geological factors. As a matter of fact the synsedimentary tectonics and the turbiditic sedimentation have determined the best conditions for the trapping of the biogenetic gas in the southeastern part of the area, where 70% of the original Tertiary gas in place is present. In the pedealpine homocline sediments have not been affected by strong Plio-Pleistocene folding, and therefore only a small amount of biogenetic gas was accumulated in the stratigraphic and in the rare structural traps. On the other hand the thermogenic methane is found in the vicinity of the Apennines where strong tectonic movements have favoured its migration from deeper zones and into Mezozoic deposits of the pedealpine homocline.
Furthermore for the first time the presence of pure isotopically light methane is here reported at 4500 m depth, that is from depths greater than so far reported in literature (3350 m). This fact is due to peculiar geological settings of the southeastern area comprising the low geothermal gradient, the synsedimentary tectonics and the strong Plio-Pleistocene subsidence (8000 m).
Selection Criteria for the Use of Vitrinite Reflectance as a Maturity Tool
Authors: Buiskool Toxopeus J. M. A. 
Published: September 2007

Summary
The increase in temperature during burial of a source rock results in a series of progressive diagenetic changes in the organic matter, one of them being the generation of oil and/or gas in the maturity zone. These diagenetic changes (maturity level) can be measured by vitrinite reflectance. Microscopical investigation together with extensive vitrinite reflectance measurements on coals and coaly shales indicate that various types of vitrinite can occur. Two main groups of vitrinite can be distinguished:

Vitrinite-1
is a relatively hydrogen-poor vitrinite formed in the peat swamp environment. In the vitrinite-1 group common submacerals such as telinite, telocollinite and corpocollinite are found.

Vitrinite-2
is relatively hydrogen-rich. Vitrinite-2 can be distinguished from vitrinite-1 by its (weak) fluorescence during ultraviolet irradiation and by a lower reflectance. Detrital vitrinite particles are often vitrinite-2.

In conventional coal petrology, vitrinite reflectance is measured exclusively on telocollinite. As the maturity is measured by the same vitrinite reflectance scale, it is of great importance to select the higher reflecting vitrinite-1 for measurements instead of the lower reflecting vitrinite-2. In this paper selection criteria are described for the use of vitrinite reflectance. In a number of examples the variation of reflectance between these two types of vitrinite and its implication for exploration are reported.
Commercially Available Geological Databanks—U.K.C.S.
Authors: Wigley P. 
Published: September 2007

Summary
There are two major commercially available databanks which contain geological data from the U.K.C.S. They are operated by Petroconsultants Ltd. and ERICO Research Labs Ltd. This paper deals primarily with the ERICO system, but a brief review of the Petroconsultants’ system is also given.
EXPHST—A Program to Analyse the History of Exploration Success within a Basin or Country
Authors: Chew K. J. , Stephenson H. 
Published: September 2007

Summary
EXPHST is a program written to search for, extract and manipulate information contained in two of Petroconsultants’ petroleum exploration data banks. The objective of the program is to provide statistical data regarding trends in the exploration history of a basin, country or other areas. The data thus derived describe drilling and discovery rates and various aspects of oil and gas production and reserves.
This paper describes the nature of the data banks from which the data are obtained, the operation of the EXPHST program, and some limitations and possible extensions of the method.
Finally, as an illustration of the program output, the exploration history of the U.K. continental shelf is described.
Oscillating modes of orogeny in the Southwest Pacific and the tectonic evolution of New Caledonia
Authors: Rawling T. J. , Lister G. S. 
Published: September 2007

Abstract

This paper presents a new interpretation of the tectonic evolution of New Caledonia, based on the extrapolation of detailed structural analysis at several different scales. The coherent high-pressure schist belt of northern New Caledonia contains clear evidence for cyclicity in the orogenic process. Two switches from large-scale crustal shortening to extensional tectonism can be recognized. We propose that orogenesis initially resulted in significant crustal thickening, obduction, and high-pressure (15–20 kbar) metamorphism. There is a close temporal link between ophiolite emplacement and high-pressure metamorphism. The high-pressure rocks were exhumed during the first period of extensional tectonism (
c.
40–36 Ma) as a large coherent terrane (>1500 km
2
). During the second period of crustal shortening the New Caledonia orogen was folded into upright megafolds. Basin and Range style normal faulting then took place, bringing the folded extensional terrane and the high-pressure rocks to their present crustal level. Metamorphic grade changes in the high-pressure belt are structurally controlled by these late-stage normal faults. However, movement on these faults is responsible for only the very last stages of exhumation.
Exhumation history of orogenic highlands determined by detrital fission-track thermochronology
Authors: Garver John I. , Brandon Mark T. , Roden-Tice Mary , Kamp Peter J. J. 
Published: September 2007

Abstract

A relatively new field in provenance analysis is detrital fission-track thermochronology which utilizes grain ages from sediment shed off an orogen to elucidate its exhumational history. Four examples highlight the approach and usefulness of the technique. (1) Fission-track grain age (FTGA) distribution of apatite from modern sediment of the Bergell region of the Italian Alps corresponds to ages obtained from bedrock studies. Two distinct peak-age populations at 14.8 Ma and 19.8 Ma give calculated erosion rates identical to
in situ
bedrock. (2) Zircon FTGA distribution from the modern Indus River in Pakistan is used to estimate the mean erosion rate for the Indus River drainage basin to be about 560 m Ma
−1
, but locally it is in excess of 1000 m Ma
−1
. (3) FTGA distribution of detrital apatite and zircon from the Tofino basin records exhumation of the Coast Mountains in the Canadian Cordillera. Comparison of detrital zircon and apatite FT ages gives exhumation rates of
c.
200 m Ma
−1
during the interval between
c.
34 and 54 Ma, but higher rates (
c.
1500 m Ma
−1
) at
c.
56 Ma. (4) FTGA analysis of apatite grain ages from a young basin flanking Fiordland in New Zealand indicates that removal of cover strata was followed by profound exhumation at
c.
30 Ma, which corresponds to plate reorganization at this time. Exhumation rates at the onset of exhumation were
c.
2000–5000 m Ma
−1
. These studies outline the technique of detrital FTGA applied to exhumation studies and highlight practical considerations: (1) well-dated, stratigraphically coordinated suites of samples that span the exhumation event provide the best long-term record; (2) strata from the basin perimeter are the most likely to retain unreset detrital ages; (3) the removal of ‘cover rocks’ precedes exhumation of deeply buried rocks, which retain a thermal signal of the exhumation event; (4) steady-state exhumation produces peak ages that progressively young with time and have a constant lag time; (5) same-sample comparison of zircon and apatite peak ages is best in sequences with high-uranium apatite grains (>50 ppm), and peak-ages statistics can be improved by counting numerous apatite grains (>100).
Detachment faults in the Aegean core complex of Ios, Cyclades, Greece
Authors: Forster M. A. , Lister G. S. 
Published: September 2007

Abstract
Several generations of detachment fault systems have been recognized in the Aegean metamorphic core complex of Ios, Cyclades, Greece. Multiple strands occur in each fault system, with fault-bounded slices often characterized by distinctive lithologies. These faults accomplished significant exhumation, and telescoped the crustal section. Different slices have been deformed at different crustal levels, and then juxtaposed, so that adjacent fault slices display different deformation styles. The Aegean detachment systems differ from equivalent faults observed in the US core complexes in that they separate relatively cohesive tectonic slices. However, the Aegean detachments are dissected by the multiple systems of later high-angle normal faults that define the current geomorphology, and this raises significant difficulties in correlating detachment systems between the different islands of the Cycladic archipelago. A number of distinct extensional events can be defined on Ios. The Cycladic blueschist belt was exhumed relatively early during the history of Alpine orogeny, after it had been thrust over a Hercynian ‘basement’ terrane, with the oldest recognized detachment faults associated with Miocene N-S extension. This led to the exhumation of the ‘basement’ terrane from beneath the blueschist ‘series’ rocks. The Ios Detachment Fault system now separates the metasediments of the Cycladic blueschist belt from the mylonitized ‘basement’ complex. It was associated with the operation of the south-directed, crustal-scale, middle to upper greenschist facies, South Cyclades Shear Zone. The youngest detachment faults formed during late-stage W-directed extension, and formed a prominent sequence of low-angle normal faults termed the Coastal Fault system. These were associated with spectacular breccias, and relatively narrow ductile shear zones which formed during and subsequent to the formation of the Ios dome, under significantly lower grade conditions (lower-greenschist facies assemblages). Final exhumation of the Cycladic blueschist belt appears to have been associated with the detachment faults that led to its exposure beneath non-metamorphic sediments, and remnants of the Cyclades ‘ophiolite nappe’ as observed on adjacent islands.
Controls on pseudotachylyte formation during tectonic exhumation in the South Mountains metamorphic core complex, Arizona
Authors: Goodwin Laurel B. 
Published: September 2007

Abstract
Pseudotachylyte formed during the later stages of extension in the South Mountains metamorphic core complex. Microstructural and microchemical evidence of pseudotachylyte formation processes is well preserved in granitoid mylonite host rocks because of rapid cooling during tectonic exhumation. Petrographic studies indicate a cataclasite precursor to pseudotachylyte. Transmission electron microscope analysis shows glass in pseudotachylyte, providing evidence of melting. Electron microprobe analyses demonstrate variations in glass, microlite, and crystallite composition with proximity to quartz clasts, indicating reaction between clasts and melt. Amphibole crystallites exhibit sieve textures, interpreted as recording rapid crystallization and subsequent decompression. Decompression is postulated to result from drops in fluid pressure along jogs in the slip surface or following formation of injection veins. Both pseudotachylyte and cataclasite are typically subparallel to C-surfaces in the host mylonite. Cataclasite not associated with pseudotachylyte is composed of quartz + feldspars ± biotite. Pseudotachylyte everywhere contains biotite. The model proposed for formation of pseudotachylyte and cataclasite in foliated granitoid protoliths includes seismic failure along C-surfaces. Where biotite is absent, slip produces cataclasite. Where biotite is present, initial cataclasis may be followed by frictional melting, facilitated by biotite’s low melting temperature and lowering of the melting temperatures of other phases by release of water during biotite breakdown.