bluuebunny/crossref_metadata_2025_split huggingface dataset:
Haltenbanken hydrocarbon province (off-shore Mid-Norway)
Authors: Heum O. R. , Larsen R. M. 
Published: April 2008

Abstract
Exploration drilling at Haltenbanken started in 1980 and to date 11 significant hydrocarbon discoveries have been made. The estimated total recoverable discovered reserves are 310 million SM3 of oil and condens and 305 billion SM3 of gas. Only 14 out of 25 proper wildcat wells turned out dry, giving a pure exploration success ratio of 44%. The major structural elements at Haltenbanken are (from East to West) the Troendelag Platform, the Halten Terrace and the Deep Moere Basin. The major hydrocarbon discoveries are located on the Halten Terrace and on the western margin of the Troendelas Platform.
After a long period of regional passive subsidence during Triassic and most of Jurassic the Halten Terrace was formed as a consequence of Late Jurassic east-west rifting and early/middle Cretaceous north-south Dextral wrenching. During late Cretaceous and Tertiary again regional passive subsidence dominated. In Miocene very deep waters had developed at Haltenbanken as well as over most of the Mid-Norwegian Shelf. In Pliocene uplift of the Fennoscandian Shield resulted in rapid westward shelf progradation and deposition of up to 1000 m of sediments.
This Pliocene burial had a great impact on the formation and entrapment of hydrocarbons at Haltenbanken. As the temperatures increased the rich Upper Jurassic marine and Lower Jurassic terrestrial source rocks passed through the oil window and are currently still producing large amounts of oil, condensates and gas.

The rapid Pliocene sediment loading also led to great overpressure in the Upper Jurassic to palaeocene line-grained sequence. In the Eastern areas this overpressure resulted in a perfect seal over the Middle and Lower Jurassic sandstone reservoirs. In the Western areas also the Jurassic reservoir sequence is severely overpressured leading to less favourable sealing conditions. On the other hand, the overpressure in the reservoirs in the Western areas seems to have reduced the rate of compaction, hence preserving the porosity and permeability better at great depths. Seven of the most important discoveries at Haltenbanken are discussed as case examples. The variations in type of hydrocarbons (oil, vs. gas or gas/condensates) entrapped in the individual fields are caused by subtle, but important variations in source rock maturity, migration conditions (including drainage area and storeage capacity), trapping conditions (fill-spill or fill-leak), timing and
PVT
-conditions.
Lena-Tunguska Upper Proterozoic-Palaeozoic petroleum superprovince
Authors: Kontorovich A. E. , Mandel’Baum M. M. , Surkov V. S. , Trofimuk A. A. , Zolotov A. N. 
Published: April 2008

Abstract
The Lena-Tunguska Superprovince is the only region of the world where extensive economic Upper Proterozoic petroleum production is proved. This province extends the stratigraphical range of hydrocarbon accumulations to the deposits older than one billion years.
The Upper Proterozoic deposits are represented mainly by Riphean carbonate formations and terrigene carbonate sulphate-bearing sediments of Vendian (Eocambrian). These deposits cover an area of some two million square kilometres.
Oil and gas potential in the Vendian and Upper Cambrian sediments in the central and southern regions of the province is proven and more than thirty fields have been discovered. Sheet, roof, lithologically and tectonically screened and non-anticlinal pools dominate these discoveries. The Lower Cambrian salts are the regional seal.

Riphean petroleum potential has been proved in the western part of the province where the extensive Yurubcheno-Takhomsk zone of oil and gas accumulations occur within the Baikit antecline and Katanga Trough. Oils appear to be of one genetical type as low sulphur, naphthenic-rich oils containing
n
-alkanes, isoprenoids and are enriched in 12,13-monomethylalkanes,
12
C carbon isotope.

The main current oil-producing plays are confined to Riphean Formations.
Sequence stratigraphy and the habitat of hydrocarbons, Gippsland Basin, Australia
Authors: Rahmanian V. D. , Moore P. S. , Mudge W. J. , Spring D. E. 
Published: April 2008

Abstract
The Gippsland Basin is Australia’s most prolific oil and gas province, with initial reserves estimated at 3.6 billion barrels crude/condensate, 0.6 billion barrels liquid petroleum gas (LPG) and 8.3 TCF dry gas. It is located in southeastern Australia, mainly offshore. Significant hydrocarbons were first discovered in 1964, in large structures at the top of the Late Cretaceous-Eocene Latrobe Group. All of the large structures have now been drilled, with current exploration concentrating on fault-dependent and combined stratigraphic structural traps within the Latrobe Group. Hydrocarbon, source rock and maturation data suggest that there is a widespread and uniform non-marine source of Late Cretaceous age. The concentration of hydrocarbons at the top of the Latrobe Group is due to the presence of large structures, an excellent cap seal, and the relatively sandy nature of the underlying, intra-Latrobe section. The distribution of oil versus gas at this level is largely explained by maturation variations and migration pathways within the basin. Vertical migration of up to 2 km is required in most cases. The distribution of oil versus gas is also influenced by minor source rock variations, fresh water washing, biodegradation, and the variable quality of fault seal. Recent exploration studies have concentrated on locating stratigraphic and combination traps, especially within the Latrobe Group. Prediction and subsequent discovery of these traps is a challenging task that has been aided by sequence-stratigraphic and seismic-stratigraphic analysis of the rock record. This has allowed the prediction of reservoir, source and seal geometries and distributions. The techniques used to construct this chronostratigraphic framework are presented, together with examples of its application within fields and on a regional basis.
U-Pb geochronology of the Upper Proterozoic Cadomian orogeny in the northern Armorican Massif, France
Authors: Guerrot C. , Peucat J. J. 
Published: April 2008

Abstract
U-Pb zircon dating has clarified the timing of magmatic and metamorphic events during the Cadomian orogeny from 670–660 Ma to 530 Ma. This indicates a time-span of nearly 150 Ma for the Cadomian orogeny in the northern part of the Armorican Massif.

The ages of
c.
667 Ma and 656 Ma obtained for granodiorite boulders from a Brioverian conglomerate are the oldest known dates which may relate to the Cadomian orogeny, and imply an early cycle of uplift, erosion and sedimentation before major plutonism around 590 Ma.

Two main phases of evolution are recognized. The first one, probably related to an active margin, is characterized by the emplacement of granodiorites at 670–660 Ma, 645 Ma and 615 Ma ago followed by basic magmatism at 600 Ma in a back-arc environment. Some of these rocks underwent metamorphism or cooling a short time after emplacement, thus indicating an active tectonic setting with rapid uplift of the crust and some crustal thickening. This phase of evolution ended with diorite emplacement around 590–580 Ma ago. The second phase corresponds to an important crustal melting event recorded by migmatitic gneisses and anatectic magmas formed 540 Ma ago.
The ages obtained lead us to propose a new chronostratigraphy for the Upper Proterozoic Brioverian Supergroup with a Lower Brioverian Group deposited between 660 and 590–580 Ma in the Baie de Saint-Brieuc and before 585 Ma in Normandy. The Upper Brioverian Group in Normandy was formed between 585 and 540 Ma. There is no evidence for the existence of Pentevrian or Icartian basement in the Baie de Saint-Brieuc.
The geology of the Penthièvre crystalline massif: a reappraisal of the type-Pentevrian area, northern Brittany
Authors: Shufflebotham M. M. 
Published: April 2008

Abstract

Field evidence suggests a complex history for the Penthièvre crystalline massif (PCM) prior to the deposition of the local Brioverian supracrustal sequences, the Erquy Volcanic Formation and the Hillion Volcanic Formation. The PCM comprises three assemblages of igneous derivation: (a) the Yffiniac Group, consisting of amphibolites and banded orthogneisses which were deformed and metamorphosed to amphibolite facies during D
1
and D
2
; (b) the Port Morvan Group, comprising Grey and Green Gneisses of trondhjemitic to quartz dioritic composition, the precursors of which intruded the Yffiniac Group and were deformed and metamorphosed during D
3
and D
4
; and (c) the Jospinet Group of granodiorites, the St Maurice quartz diorite and, probably, the Fort de la Latte Complex (the latter two were emplaced during D
5a
). A shearing event (D
5b
) produced cataclastic fabrics in the basement, and the Hillion—Cesson Mylonite Belt, prior to the deposition of the Brioverian in the area.

The Erquy and Hillion Volcanic Formations were deposited in an ensialic basin upon a basement complex represented by the PCM. Island-arc and active continental margin magmatism occurred from before 670 Ma to as late as the Cambrian. This magmatism can be viewed as representing the effects of the Cadomian orogeny, during the early stages of which the local Brioverian sequences were deposited.
Brioverian volcanism and Cadomian tectonics, Baie de St Brieuc, Brittany: stages in the evolution of a late Precambrian ensialic basin
Authors: Roach R. A. , Lees G. J. , Shufflebotham M. M. 
Published: April 2008

Abstract
During late Precambrian times, the Northern Brittany and Lower Normandy region was the site of extensive submarine basaltic volcanism. On the southern side of the Baie de St Brieuc, two volcanic formations have been identified. In the east the Erquy Volcanic Formation (EVF), over 2 km thick, is a sedimentary-volcanic sequence in which the basalts occur mainly as pillowed, massive or composite massive-pillowed flows, interdigitated with intrusive sheets. Whole- and broken-pillow breccias, hyaloclastites, and peperites are locally common. Further west, the Hillion Volcanic Formation (HVF) has a similar thickness and attitude, and exhibits the same range of lithologies as the EVF, though in a more deformed state and metamorphosed to a higher grade. While assigned by some workers to the Ordovician, several lines of evidence are presented which show that the basic volcanics of the EVF form part of the same late Precambrian volcanic suite as the HVF.
The suite was erupted in a marginal basin (the Lanvollon basin) environment founded upon a slightly older crust of calc-alkaline plutonic rocks, now represented in part by the adjacent Penthièvre massif. Basic sheets (the Dahouët dykes), cutting this basement, are considered co-genetic with the volcanics of the EVF and HVF. Chemically, the metabasic lavas, sub-volcanic sills and dyke rocks are subalkaline, tholeiitic basalts and basaltic andesites. The Lanvollon basin was subsequently filled with clastic sediments and then subjected to Cadomian deformation and metamorphism, the grade of which increases westwards, varying from prehnite-pumpellyite to lower amphibolite facies.
The Brioverian (Upper Proterozoic) and the Cadomian orogeny in the Armorican Massif
Authors: Rabu D. , Chantraine J. , Chauvel J. J. , Denis E. , Balé P. , Bardy Ph. 
Published: April 2008

Abstract
The Brioverian in Brittany has generally been divided into the volcanogenic Lower Brioverian and the detrital Upper Brioverian, representing respectively the first and second episodes of the Cadomian orogeny, Cadomian I and Cadomian II. This scheme was subsequently incorporated into an active margin model of evolution and related to subduction during closure of the Celtic Ocean, in a geochronological framework defined by ages of 2000 Ma for the basement, 670 Ma for magmatic rocks of the first episode (Cadomian I) and 600 Ma for those of the second (Cadomian II).
Recent work has led to substantial modification of this model. The two parts of the Brioverian are now considered not to have been superposed one upon the other but to be juxtaposed along a suture, and the superimposition of Cadomian structures not to have been due to successive events but to southward migration of deformation from the ocean towards the continent.
In the northern, orogenic domain the volcanogenic Brioverian represents a volcanic arc-back-arc basin system located on a rifted continental margin. At about 600 Ma the closure of this system resulted in the overthrusting of the orogenic belt onto the continental margin, with the development of anatectic magmatism up to 540 Ma.
In the southern, continental domain the detrital Brioverian includes black chert in the lower part (probably contemporaneous with the volcanogenic deposits of the orogenic zone) and reworked black chert in the upper part. In Normandy, the deformation of these rocks was related to the rise of the Mancellian granites about 540 Ma. In central Brittany, the main deformation is Variscan in age, and the age of the Brioverian there is questionable as the lower part of the Palaeozoic cover is of Ordovician age.
Tectonic evolution of the Cadomian belt in north Brittany
Authors: Strachan R. A. , Roach R. A. 
Published: April 2008

Abstract

A discrete geotectonic unit, here termed the St Brieuc Terrane, has been identified within the late Precambrian Cadomian belt of the Armorican Massif. This terrane contains syn-orogenic Brioverian supracrustal rocks which accumulated in a marginal basin and were intruded by subduction-related calc-alkaline plutonic complexes during the period
c.
615–580 Ma. The Brioverian unconformably overlies orthogneisses and granitoids of the Penthièvre complex which formed during an early phase of Cadomian calc-alkaline activity. Regional transpressive deformation resulted in the internal imbrication of the St Brieuc Terrane into five tectonic blocks, mainly bounded by ductile shear zones which have both strike-slip and dip-slip senses of movement. Amalgamation of the St Brieuc Terrane with the St Malo Terrane to the SE occurred at
c.
540 Ma, during regional sinistral transpression. Major subvertical faulting localised along Cadomian shear zones was probably initiated during post-Cadomian extension and continued through Variscan events.
Post-Cadomian erosion, deposition and basin development in the Channel Islands and northern Brittany
Authors: Went David , Andrews Michael 
Published: April 2008

Abstract
Facies analysis, provenance, and palaeocurrent studies of the Rozel Conglomerate Formation (Jersey), Alderney Sandstone Formation and the Erquy—Fréhel Group (northern Brittany), have established patterns of ‘molasse-like’ sedimentation in a series of basins related to a phase of post-Cadomian tectonism.
Although shallow marine sediments form minor constituents of the Alderney Sandstone Formation and Erquy-Fréhel Group, fluviatile sediments deposited by braided streams axially draining eastwards predominate. Palaeocurrents within alluvial fan deposits in Jersey, and similar tributary systems in Alderney and Brittany, indicate drainage orientated either transverse to the basin axes, or at a high angle to the main trunk streams. Gross sediment dispersal was towards the Cambrian shoreline that lay to the east.
These basins and their equivalents in Normandy are elongate parallel to the east-west structural grain of the Cadomian Orogen. The basins opened, and the sediments were shed, in response to a phase of post-Cadomian extension. The geometries of these basins were possibly controlled by the re-activation of Cadomian thrust and strike-slip faults. The area to the west of Normandy, though probably mountainous in aspect, was one that was, for the most part, open to a marine connection. In Normandy itself, Cambrian sediments were deposited sometimes in continental environments, but more commonly in shallow seas.
Sedimentology, structural evolution and tectonic setting of the late Precambrian Longmyndian Supergroup of the Welsh Borderland, UK
Authors: Pauley J. C. 
Published: April 2008

Abstract
The Longmyndian Supergroup is an approximately 6500 m thick sedimentary sequence of late Precambrian age. Major unconformities within this sequence are lacking. The Longmyndian Supergroup can be divided into four facies associations: (1) turbidite, (2) subaqueous delta, (3) alluvial floodplain, and (4) braided alluvial. These are organized into a single, broadly upwards-coarsening, progradational sequence, with the turbidite association at the base and the braided alluvial association towards the top. The sediments are interpreted to have been deposited in a forearc, or possibly interarc, basin which lay to the north of a contemporaneous magmatic arc, of which the (now adjacent) Uriconian Volcanic Complex is considered to have been a part. The Longmyndian Supergroup has been deformed into a tight NNE-SSW trending syncline. Fault patterns and strain markers within the Longmyndian indicate that it was deformed during sinistral transpression. The adjacent Pontesford-Linley and Church Stretton fault systems are considered to be major strike-slip fault systems which were initiated at about the same time as the deformation of the Longmyndian Supergroup. Strike-slip movements along these fault systems resulted in the juxtaposition of the Uriconian Volcanic Complex with the Longmyndian Supergroup. Late Precambrian/early Cambrian deformation is indicated by some stratigraphic and radiometric age-dating evidence. Since there is evidence that the fault systems have suffered strike-slip displacements during the Palaeozoic it is difficult to be certain of the magnitude and style of the late Precambrian/early Cambrian deformation. However, the recognition of late Precambrian/early Cambrian sinistral transpressional deformation in northwest Wales suggests that the Precambrian of the Welsh Borderland was similarly deformed during the late Precambrian/early Cambrian.
Late Precambrian-Early Palaeozoic evolution of part of the Avalon terrane in southern New Brunswick, Canada
Authors: Nance R. Damian 
Published: April 2008

Abstract

An important Proterozoic to early Ordovician record of the Avalon terrane is exposed between the Wheaton Brook Fault and the Bay of Fundy in southern New Brunswick, Canada. Ductilely mobilized tonalitic ?basement of possibly Helikian age (Brookville gneiss) a platform carbonate-quartzite cover (Green Head Group) containing ?mid-Riphaean stromatolites. ?Unconformably overlying carbonate slump breccias and turbidites (Martinon Formation) are interpreted to record the collapse of this platform and may be broadly contemporary with minor mafic magmatism and a mid-Hadrynian (
c.
800 Ma) tectonothermal event apparently recorded in the Brookville gneiss. However, the association may equally reflect the onset of late Hadrynian (
c.
625–550 Ma) subduction recorded in calc-alkaline granitoid plutonism (Golden Grove suite) and associated arc-related volcanism (Coldbrook Group). The broadly coeval? emplacement of bimodal sheeted dykes (Kingston complex) appears to have occurred under conditions of sinistral transtension suggesting subduction was oblique. Mafic dykes are mainly continental tholeiites and the complex is interpreted to represent the floor of a volcanic arc rift. Major ductile shear zones of dextral sense, which border the dyke complex, may record late Precambrian rift closure but were active in the mid-Palaeozoic. Post-tectonic ‘Eocambrian’ volcanogenic redbeds and continental rift volcanics pass disconformably into Cambro-Ordovician sandstones and shales of the Saint John Group which contain shallow-marine Acado-Baltic fauna of the Iapetus cycle and represent an overstep sequence to Avalon’s Precambrian evolution. Termination of subduction and the tectonic transition to Cambro-Ordovician platformal conditions lacks evidence of a major collisional event. Instead, they coincide with the break-up of a late Precambrian supercontinent that was responsible for the inception of the Iapetus cycle and are likely to reflect the major plate reorganizations that would accompany such an event.
The geochemistry and petrology of the Late Precambrian Georgeville Group: a volcanic arc-rift succession in the Avalon terrane of Nova Scotia
Authors: Murphy J. B. , Keppie J. D. , Dostal J. , Hynes A. J. 
Published: April 2008

Abstract
The Antigonish Highlands of northern mainland Nova Scotia lie within the Avalon terrane of the Canadian Appalachians. They are predominantly underlain by late Precambrian interbedded metasedimentary and metavolcanic rocks of the Georgeville Group. In the southern highlands, subaerial volcanic rocks of the Keppoch Formation consist of bimodal, porphyritic and aphyric mafic and felsic flows. Pophyritic mafic flows display volcanic arc calc-alkalic affinities and are extensively fractionated. The aphyric mafic flows are characterized by strong Fe and Ti enrichment and are probably continental tholeiites derived from a heterogeneous metasomatized upper mantle source. Felsic lavas display volcanic arc affinities and were probably derived by anatexis of the crust.
In the northern highlands, mafic flows of the Chisholm Brook Formation are dominated by calc-alkalic basalts and andesites and minor interlayered continental tholeiites. In the central highlands, submarine volcanic rocks of the Clydesdale Formation consist of continental tholeiites and are broadly comparable with those of the Keppoch Formation. The close spatial and temporal association of calc-alkalic and tholeiitic mafic rocks, the felsic rocks with volcanic arc chemistry and the stratigraphy which documents the infilling of a narrow sedimentary basin suggest a rift setting within an ensialic volcanic arc environment. The style of volcanism exhibited in the Antigonish Highlands compares favourably with other late Precambrian successions in Nova Scotia. In general late Precambrian volcanism in northern Nova Scotia is consistent with an ensialic volcanic arc environment with local development of volcanic arc rifts and provides constraints on the evolution of the Avalon terrane as a whole.