bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antarctic belemnite biogeography and the break-up of Gondwana
Authors: Doyle Peter , Howlett Philip 
Published: April 2008

Abstract

In the late Jurassic, the belemnite genera
Hibolithes
and
Belemnopsis
were abundant and widespread in Tethys, characterizing a Tethyan Realm that extended south from southern Europe and Asia to Antarctica and the rest of Gondwana. Although a distinct Southern Hemisphere ‘Austral’ belemnite realm counterbalancing the northern Boreal Realm was absent, it is clear that a significant degree of endemicity existed at the species level, with distinct species groups in Indonesia, Madagascar, Australasia, South America and so on.

Trans-Gondwanan faunal links first developed in the late Jurassic shelf seaway between Antarctica, Madagascar and India.
Belemnopsis
became extinct in southern Europe, and was left as a relict, endemic to this trans-Gondwanan seaway. In the Aptian the Belemnopseidae were eventually replaced around Gondwana by the endemic family Dimitobelidae, which developed as the Antarctic—Australasian core of Gondwana began to drift south. In Tethys few genera remained, the Tethyan Realm finally breaking down in the late Cretaceous. Initially the Dimitobelidae were widespread in Gondwanan seas, the trans-Gondwanan links developed in the Jurassic being maintained. However, as Gondwana fragmented further in the late Cretaceous, these links broke down and the Dimitobelidae survived only in the Antarctic-Australasian region which was retreating southwards.
Evolutionary patterns in macrurous decapod crustaceans from Cretaceous to early Cenozoic rocks of the James Ross Island region, Antarctica
Authors: Feldmann Rodney M. , Tshudy Dale M. 
Published: April 2008

Abstract

The fossil record of macrurous decapod crustaceans is unusually rich in the Late Cretaceous to Paleocene rocks of the James Ross Island region, Antarctica. Four species of lobsters, contained in four genera, are known from the region.
Hoploparia stokesi
(Weller) is most abundant and has been collected on James Ross, Vega, Humps, Cockburn, Seymour, and Snow Hill islands from early Campanian through Paleocene rocks. Whereas morphometric analysis of the species shows no evolutionary trends in shape, carapace ornamentation and claw ornamentation become more variable higher in the section.
Metanephrops jenkinsi
Feldmann, has also been identified.
Metanephrops
has previously been known from only one fossil occurrence, in the Pliocene of New Zealand. Its occurrence on Seymour Island may lie within the region of origin of this taxon which currently inhabits deep water, lower latitude habitats in the Atlantic and Indo-Pacific oceans.
Metanephrops jenkinsi
is known in the early Campanian Santa Marta Formation, in the Maastrichtian portion of the Lopez de Bertodano Formation, and in the Paleocene Sobral Formation. Other taxa are less abundant. In early to middle Campanian rocks on James Ross Island,
Meyeria crofti
Ball represents a relatively late occurrence of a conservative group.
Linuparus macellarii
Tshudy & Feldmann represents the highest latitude occurrence of a species within this genus, which is known from numerous Cretaceous and Paleogene sites in the Northern Hemisphere but from only two other fossil occurrences in the Southern Hemisphere. This species ranges from the early to middle Campanian into the Paleocene. There is no apparent effect of the K/T boundary ‘event’ on the decapod fauna. New taxa appear below the K/T boundary and none of the Antarctic species disappear from the record at that time.
Antarctica: the effect of high latitude heterochroneity on the origin of the Australian marsupials
Authors: Case Judd A. 
Published: April 2008

Abstract
The record of the Antarctic marine fauna during the Paleogene indicates the occurrence of taxa in high latitude regions (>60°) before these same taxa are known in midto low latitudes. It has been hypothesized that high latitude regions serve both as ‘holding tanks’ for taxa and as regions in which novel adaptations leading to new lineages within a taxon can arise. These features of high latitude regions appear to have had a major impact on the origin of the Australian marsupial fauna. The australidelphian marsupial clade (all Australian marsupials plus South American microbiotheriids) and the ameridelphian marsupial clade (all South American marsupials except microbiotheriids) diverged in the Late Cretaceous. The South American marsupial radiation occurred in mid- to low latitude regions during the Late Cretaceous to early Paleocene. The Australian marsupial radiation probably did not occur until the medial or late Eocene. If accurate, this represents a time differential of 20 to 25 Ma between the two marsupial radiations. The heterochroneity of the marsupial radiations results from the fact that during the Late Cretaceous to Eocene, Australia resided in a high latitude region, the cool temperate Weddellian Biogeographical Province. The radiation of Australian marsupials only reaches a level of taxonomic diversity comparable to that in South America after the continent drifted northward into lower latitudes and habitat diversity increased. This is deduced from changes in floral diversity and the projected timing of the diprotodontian divergences based on DNA hybridization data.
Antarctica as an evolutionary incubator: evidence from the cladistic biogeography of the amphipod Family Iphimediidae
Authors: Watling Les , Thurston Michael H. 
Published: April 2008

Abstract

The modern Antarctic marine fauna is quite distinct, with levels of endemism reaching 90% at the species level and 70% at the generic level. Since the modern Antarctic waters are very cold and isolated from all of the worlds oceans except the deep-sea, the origin of the modern Antarctic fauna has remained in doubt. The amphipod Family Iphimediidae is represented in Antarctic and Sub-Antarctic waters by 16 of its 21 genera and 490f its species. A phylogenetic analysis of the family indicates that the most primitive genera are distributed primarily outside Antarctic waters. It is suggested that these are relicts of a former global distribution, and that once the Antarctic began to cool (38 Ma ago), a radiation of the iphimediids occurred in the Southern Ocean. This radiation was furthered by the reorientation of the mandible from one where the incisor cut in the horizontal transverse plane to cutting in the vertical frontal plane. With this advance, the family spread outward from the Antarctic, principally through the genus
Iphimedia
, which is today represented by 35 known species worldwide. The tracking of features in
Iphimedia
suggests that its initial spread beyond Antarctic waters occurred before the continent was finally thermally isolated 23 Ma ago. It is proposed that the cooling Antarctic waters acted as an incubator for this family, producing an evolutionary advance that allowed it to be a successful colonizer of the thermally changing global ocean.
Gamma-ray log shape used as a facies indicator: critical analysis of an oversimplified methodology
Authors: Rider M. H. 
Published: April 2008

Abstract
Gamma-ray log shapes are often used by geologists to determine sandstone grain size trends and hence depositional facies. However, for the simple methodology of relating shapes to facies to be valid, there must be consistent relationships between gamma-ray log values and clay content and between clay content and grain size. Log to core comparisons and sandstone textural analyses show that these relationships are naturally variable. Consequently, correlation of log shape with grain size trend is tenable only under very limited (and defineable) conditions. A universal application of gamma-ray log shape to grain size trend and depositional facies is wrong.
Stochastic reservoir description: a methodology
Authors: Moss B. P. 
Published: April 2008

Abstract
Stochastic log interpretation methods are shown to provide more detailed information regarding the geology encountered in a complex formation than can be obtained by conventional interpretation methods. The next stage is to combine these data with qualitative data from other sources than wireline logs to provide information about the ‘rock types’ present. Such rock type definition provides the link between descriptive geological data and the likely hydrodynamic model of interest to reservoir engineers. The final stage in the reservoir description process is to relate the vertical sequence, observed and described in the well bore, to the distribution of the rock types in three dimensions within the reservoir body. This paper presents the methodologies behind each of these three stages in building a more complete reservoir description, and demonstrates their application on actual data from a producing field.
Natural gamma-ray spectrometry in hydrocarbon-bearing sandstones from the Norwegian Continental Shelf
Authors: Hurst Andrew 
Published: April 2008

Abstract
Concentrations of thorium (Th), uranium (U) and potassium (K) are measured using natural gamma-ray spectrometry (NGS) logs. The precision of NGS measurements in sandstones varies: K measurement is in general moderately good; Th measurement varies with the service company involved; U measurement is unreliable. Concentrations of Th, U and K in standard tables of minerals used commonly in log evaluation are not representative of the actual elemental concentrations found in sandstone minerals. Th/K cross-plots are shown to be unsuitable for the identification of clay minerals in sandstones. Illite cement cannot under normal geological circumstances be identified from the K content of the rock. Authigenic kaolinite has no particular affinity for concentration of Th. Th in sandstones is concentrated predominantly in detrital heavy minerals with up to 200f the total Th present in silt-sized and finer authigenic REE-phosphates and Th salts. Variation in the K content of micas from some Jurassic sandstones demonstrates the need for using formation-specific chemical data for the minerals of interest (micas, feldspars, clay minerals) as input parameters in normative calculations. Appropriate statistical control of the validity of Th, U and K contents for specific minerals is required.
Structural interpretation of dipmeter results in the Gullfaks Field
Authors: Rønningsland T. M. 
Published: April 2008

Abstract
Dipmeter interpretation has been carried out on seven wells from the Gullfaks Field. Orientation and style of major and associated minor faults have been investigated using dipmeter results. Major faults, as inferred from dipmeter data, are in fairly good agreement with faults defined from seismic interpretation. Several less significant dipmeter-defined faults were below the resolution of seismic data. The orientation of these faults probably corresponds with that expected of antithetic and synthetic faults associated with the main fault system. Analyses of dipmeter results indicate little or no influence of synsedimentary tectonism. Thickness variations of the different formations can be explained by post-depositional faulting (fault cut-out) and erosion. The differences in structural dip between the seven wells support the interpretation that they are located on separate fault blocks. The density of detected faults, one per 140 m (from dipmeter results), proves the presence of an intensely faulted area. This study therefore emphasises the importance of using dipmeter results as a supplement to seismic for the purpose of structural interpretation.
Example of fault identification using dipmeter data
Authors: Devilliers M. C. , Werner Ph. 
Published: April 2008

Abstract
Dip results obtained by conventional processing techniques are not always suitable for the identification of faults. Dipmeter identification of faults is usually based on the recognition of increasing angles of dip associated with drag zones adjacent to fault zones. Several case studies confirm this relationship. Interpreting faults in this way is, however, risky, and can lead to erroneous data being integrated into structural interpretation. By reviewing original log quality and processing methods, much erroneous information can be eliminated. The influence of faulting on raw dipmeter curves is studied, and actual fault geometries from outcrops are compared with dipmeter patterns. Outcrop data are taken from several tectonic contexts in order to provide a significant amount of information, in spite of the restricted vertical perspective of the outcropping faults. Reliable detailed fault interpretation from dipmeter data is enhanced by reconstruction of dip profiles from field examples, in particular where similar data are available from other wells and local structural geological knowledge is available.
Main aspects of petroleum exploration in the Apure area of Southwestern Venezuela, 1985–1987
Authors: Chigne Nestor , Hernandez Leroy 
Published: April 2008

Abstract
This paper gives an update of exploration advances made in Apure during the years 1985–1987. It begins with a brief history of exploratory activities in the area, and then reviews present concepts as to its tectonic-sedimentary evolution. New seismic surveys have notably extended structural knowledge and recent geochemical studies have given new insights into the origin and migration of hydrocarbons; these, together with results of all exploratory drilling, allow new ideas as to additional prospects in the area.
Petroleum geology of the Campos Basin, offshore Brazil
Authors: Mohriak W. U. , Mello M. R. , Dewey J. F. , Maxwell J. R. 
Published: April 2008

Abstract
The Campos Basin, offshore Brazil, is the most prolific basin in the western South Atlantic, with more than thirty hydrocarbon accumulations currently accounting for about 60% of Brazilian oil production.
Intensive drilling and seismic, gravity and magnetic data have contributed to the recognition of four tectono-stratigraphic units related to the rifting and break-up of Pangea. The lowest sequence consists of Neocomian clastics deposited on basalt dated at 120–130 Ma, and reflects the fault-controlled subsidence associated with the stretching that preceded the emplacement of oceanic crust. The Aptian proto-oceanic stage is characterized by a sequence of evaporitic rocks that have undergone intense diapiric activity in deep water. An open-marine environment begins with a thick sequence of Albian/Cenomanian limestones, locally with clastic input, which grades upwards and basinwards into deep water marls and shales. This section is structurally associated with detached listric normal faults that sole out on the Aptian evaporites. Finally, the marine Upper Cretaceous to Recent clastic section is characterized by a more quiescent phase of thermal subsidence, with some residual halokinetic activity that increases in intensity towards deeper waters.
The hydrocarbon accumulations are distributed throughout the stratigraphic column of the basin from Neocomian to Miocene. The reservoirs range from fractured basalts and porous bioclastic limestone (coquinas) in the Lagoa Feia Formation, to limestones and sandstones in the Macaé Formation, and sandstones in the Campos Formation.

Detailed geochemical analyses undertaken on cutting, core and oil samples show that almost all the hydrocarbon accumulations discovered to date are sourced mainly from lacustrine calcareous black shales deposited in a closed Upper Neocomian lake system, having saline to hypersaline waters of alkaline affinities. The extreme anoxic conditions in this lacustrine environment resulted in the deposition of fine, well laminated organic-rich (TOC up to 9%) calcareous black shales, with high-quality organic matter composed almost entirely of low-sulphur type-I kerogen, originating from lipid-rich algal and bacterially-derived material. The excellent hydrocarbon source potential of these sediments, combined with the appropriate thermal history, produced the necessary conditions to yield low-density oil (around 30° API) characterized by a low sulphur content (around 0.30%), and significant quantities of alkanes (up to 70%). Diagnostic features in the biological markers from this depositional environment include: low concentration of steranes, presence of β-carotane, gammacerane and 28,30-bisnorhopane, very high concentrations of hopanes and high relative abundances of tricyclic terpanes up to C
34
.
Geochemistry of crude oils in Oman
Authors: Grantham P. J. , Lijmbach G. W. M. , Posthuma J. 
Published: April 2008

Abstract
The petroleum geochemistry of Oman provides a picture of considerable variety since crude oils and their source rocks are found both throughout the country and throughout the stratigraphic column from the Infra-Cambrian to the Tertiary. The oils can be geochemically classified into five groups. Three of them can be related to good oil source rocks found in the Precambrian Huqf Group, the Silurian Safiq and the Cretaceous Natih Formations. Another group of oils probably originates from the Upper Jurassic Diyab Formation whilst the fifth group of crudes (name ‘Q’) cannot be correlated to a known source rock but is inferred to have originated from an unpenetrated Huqf level.

The ‘Huqf oils’ are those that have been correlated to known Infra-Cambrian Iuqf source rocks and are characterized by a strong C
29
sterane predominance and very light carbon isotope values (δ C
13
) of around −36.0‰. In contrast, the ‘Q’ crudes, derived from the unknown source are characterized by a C
27
sterane predominance and carbon isotope ratios of around −30.5‰. Both the Huqf and ‘Q’ crudes also contain a series of characteristic compounds referred to as the ‘X’ compounds (all isomers of methyl and dimethyl alkanes). Oils thought to originate from Silurian Safiq source rocks have a weak C
29
sterane predominance, a significant content of rearranged steranes and carbon isotope ratios of approx. −30.5‰. The oils correlatable to the Jurassic Diyab Formation have a similar sterane distribution but heavier carbon isotope values of around −26.5‰. Finally, the crude oils from the mid-Cretaceous Natih Formation source rocks are characterized by steranes with an equivalent distribution of C
27
, C
28
and C
29
isomers and carbon istope values of around −26.9‰.
Zechstein reservoirs in The Netherlands
Authors: Baan Dietert Van Der 
Published: April 2008

Abstract
Thick, shallow-water gypsum banks, formed during Zechstein times at the site of regional palaeohighs along the margins of the Southern Permian Basin, acted as foundations for shallow-water carbonate platforms. The carbonate platform margins, in particular their northern to northeastern windward margins, were characterized by deposition of grainstones dominated by aragonitic ooids, pisoids, intraclasts and bioclasts, while muddy, stromatolitic carbonates and nodular anhydrites accumulated on tidal flats and in lagoons behind the platform margins.
Usually the platforms are surrounded by thick slope deposits consisting of carbonate mudstone and redeposited intervals, but locally the platforms deepened gradually and changed, without intervening slope deposits, into a shallow-marine facies devoid of ooids. The slope aprons grade basinwards into thin successions of finely laminated carbonate.
Porosity creation in Zechstein carbonates was due to meteoric-water leaching and to subsurface leaching by carbon dioxyde-enriched formation waters during burial. Porosity destruction was mainly caused by anhydrite pore plugging and subsurface calcitization. The best reservoir properties are found in the unrestricted platform facies and in parts of the slope facies. Fractures are important in Zechstein carbonates; their presence is a prerequisite for high production rates in gasfield wells.
Hydrocarbon plays in the northern North Sea
Authors: Pegrum R. M. , Spencer A. M. 
Published: April 2008

Abstract
The hydrocarbon finds of the Norwegian and British sectors of the North Sea, north of 56°, can be grouped into six discrete plays. The key to all the plays is the presence of organic-rich Upper Jurassic shales (source rocks) and a rift system of the same age. The rifting provided the structures (the traps) and post-rift cooling caused the subsidence necessary for hydrocarbon generation. The pre-Jurassic Play is of least importance. The Lower-Middle Jurassic Play, with about 40% of the resources, results from pre-rift uplift in the south providing clastic input for a delta system in the north, the thick sandstone reservoirs of which were preserved during the subsequent rifting. In late Jurassic times graben formation by rift collapse was accompanied by erosion of marginal uplifts, resulting in thick sand sequences, which interfinger with graben shales containing the source rocks. This ideal relationship provides the Upper Jurassic Play which contains 30% of the resources. The Lower Cretaceous Play occurs in submarine fan sandstones and is of minor importance. Chalk deposition in a tectonically unstable environment, with subsequent rapid burial beneath Tertiary muds and clays, is responsible for the Chalk Play. Although geographically limited, it is prolific and accounts for nearly 10% of the hydrocarbon resources. Geologically youngest is the Paleogene Play. Uplift of the Orkney-Shetland Platform in early Tertiary times was a consequence of sea-floor spreading in the North Atlantic. Great quantities of sand derived from this uplift spilled eastwards into the northern North Sea, blanketing the western flank of the Tertiary basin and extending axially far south along the Central Graben. These sands have captured vertically migrating hydrocarbons and have allowed extensive lateral migration. Although important volumes of oil and gas, about 20% of the total resource, are trapped within these sands, large volumes have probably been lost to the basin via their outcrop in the west.