bluuebunny/crossref_metadata_2025 huggingface dataset:
The use of text databases in the management of exploration data
Authors: Mallender S. C. R.
Published: April 2008

The management of exploration data concerns all the things that happen to a piece of exploration data during its life, and the management of the physical data is controlled by the information used to describe it. A description of the data forms part of a contract between a company and a recording contractor before the physical data even come into existence. Descriptive information about each data item and each dataset is recorded and re-recorded on many transmittals as the physical data move from recording contractor, to processing contractor, to storage contractor. The ‘computerized catalogue’ listing, which a storage contractor provides to an exploration company is often the only record of what is available, and the legal ownership records of these data are often stored elsewhere. The amount of this reference information used to describe exploration data (for example, the name and extent of a map or a line, the title of a report, the reference number of a tape) varies significantly from one data type to another, and the amount actually recorded often varies from one record to the next. Historically, there has been a lack of consistency throughout the industry in the terms used, and the number of those terms employed when describing and referring to exploration data. This poses problems in the management of exploration data.

The main problem concerns the storage, retrieval and transmission of this descriptive information; the information is rarely ‘processed’ as such. From a database point of view, the problem is to store large quantities of quite disparate and unstructured information, to find rapidly what has been stored, and to retrieve the information easily in a (re-)usable form.

Text databases are ideal in these circumstances: they can hold completely unstructured information, and allow users to find records using any data that appear anywhere in the content of the record. Accompanying software is used to provide a user interface to the text database, and this enables sophisticated systems which are very user-friendly to be developed easily.
The geological data manager: an expanding role to fill a rapidly growing need
Authors: Lowe D. J.
Published: April 2008

The management of geological data—raw, inferred and derived—has been neglected for many years. Where such management was attempted, the staff responsible were commonly non-specialists, and most were under-supported and under-valued. Expanding use of digital systems in the geological sciences and growing acceptance of a need for quality management of data in an increasingly business-orientated and competitive world have necessitated reappraisal of data management needs and the role of the geological data manager. The importance of supporting work to develop data verification and validation procedures and the means to assess and ensure data quality is gaining recognition. Some 20 years after the first major incursion of digital technology into the field of geology, the value of the data already gathered, and thus the importance of geological data management, is only now beginning to be appreciated and accepted. In the near future the geological data manager’s role is expected to expand rapidly to address the needs of geological activity.
The quality assurance of geological data
Authors: Duller Paul R.
Published: April 2008

The key to success in any geological investigation is access to accurate and reliable information. Clear strategies are required to ensure that geological information, often acquired at great expense, is not mislaid and is kept in a form that can benefit its owners. To meet this need requires the provision of a reliable data management strategy, a well-defined and efficient policy of administration and a clear understanding of the nature, origin and quality of data involved. Geological data by their very nature pose particular problems in terms of compilation, quantification and validation. However, the application of standard quality control, quality assurance and audit procedures can be used to ensure the
correctness
(or accuracy) of the data, thereby safeguarding the integrity of any associated investigation.
Project databases: standards and security
Authors: Henley Stephen
Published: April 2008

For technical applications in the mining industry, large institutional data models are the exception rather than the norm. Much more common, given the distributed nature of the business, and the scattered locations of the specialists involved, is the personal or project database. Such a database is set up for a project (or part of a project), and is developed using a data model defined specifically for that project. At the end of the project, the database may be archived or it may be supplied to a central group for integration with a corporate database. If uncontrolled, such methods of database management can lead either to direct drastic loss of data or to incompatibilities in data recording standards. The use of common software standards and data dictionaries throughout an organization can reduce radically these dangers and can produce positive benefits not only in data recovery but in reusability of techniques.
Database applications supporting Community Research Projects in NERC marine sciences
Authors: Lowry Roy K. , Cramer Raymond N.
Published: April 2008

Traditionally, oceanographic data management has been strongly cruise oriented. However, the organization of research into Community Research Projects, such as the North Sea Project and Biogeochemical Ocean Flux Study (BOFS), has produced a requirement for handling multidisciplinary data from a large number of research cruises as an integrated dataset. The code of practice for the project dictated that data were to be exchanged freely between project participants throughout the duration of the project, after which the data were to be brought into the public academic domain. The data management strategy therefore had to provide both a vehicle for data exchange within the project and a mechanism for subsequently making the data available to a wider community.

These problems were solved by BODC through the adoption of two technologies. Relational database technology was used to integrate the data and, through access over the UK academic wide area network (JANET), provide the data exchange mechanism. Electronic publication of the datasets on CD-ROM provided the mechanism for expanding the dataset user base.
Geoscience data value, cost and management in the oil industry
Authors: Miller Richard G. , Gardner John S.
Published: April 2008

BP Exploration, through its Frontier and International division (XFI), is the first oil major to openly release some of its international exploration data, information and internal reports to competitors for cash. The data and information relate to geographical areas in which the company foresees no strategic interest.

There are various ways in which such a programme could be run. In our case, all exploration information and data have an identified owner, usually the asset manager responsible for exploration in the relevant part of the world. A dedicated XFI data broking team identifies and prices material for possible exchange or licence sale. The asset manager who owns the material certifies whether it may be released without damage to the company’s competitive position. Legal staff check the ownership of the material, and ensure that there are no confidentiality constraints. Commercial brokers then either offer released material to the open market or create new products from it for licencing. The material is licenced for use rather than sold, so that the recipient cannot re-sell it. All income accrues centrally to XFI rather than to the asset manager; altruism by the owners of the data is central to our data brokerage philosophy.

Such marketing follows naturally from treating data and information as a true asset, whose value can be established in the market-place. When such marketing becomes the industry standard, then XFI can also enter the market-place as a buyer. Those who can buy existing exploration data and information will save the great cost of generating their own. This is part of a sea-change in the industry, in which the players are moving towards a lower cost base through shared activity as opposed to duplicated activity.
Groundwater level archive for England and Wales
Authors: Doorgakant P.
Published: April 2008

The monitoring of groundwater levels is important for the management of groundwater resources. Within the United Kingdom a selection of observation boreholes are monitored for periodic assessment of the groundwater resources. The measurement of groundwater levels is undertaken principally by the water companies, the National Rivers Authority (NRA) for England and Wales, the River Purification Boards (RPB) for Scotland and the Department of the Environment (DoE) for Northern Ireland. Weekly and monthly data are supplied to the British Geological Survey (BGS) and these data are entered into an ORACLE database where they are assimulated with historical records. Additionally, paper copies are archived. Data usage is facilitated by a number of computer retrievals including well hydrographs in graphic form. Access to the groundwater level information is made available to the public at a small operational cost. A number of publications are produced giving a review on groundwater, including an assessment of recharge to major aquifers and also a number of hydrographs are illustrated from the key boreholes. The database has proved to be an invaluable tool in predicting environmental change, such as droughts and rising groundwater levels.
A hydrogeological database for Honduras
Authors: McKenzie Andrew A.
Published: April 2008

An information system for the management of groundwater data was developed for the government of Honduras. The database design concentrated on close attention to the requirements and skills of the users. The database was implemented using commercially available database languages and programming tools. This allowed a bilingual system closely matched to local requirements to be developed at low cost.
CD-ROM and its application to the petroleum industry
Authors: Allen Stephen G.
Published: April 2008

Over the last few years CD-ROM has emerged in many industries and professions as an essential means of distributing and accessing information. The petroleum industry, however, has been slow to realize the potential of this medium with, until recently, only a few isolated applications available. A detailed description of the CD-ROM medium and its manufacture is provided and its relevance to the oil industry discussed. Some examples of early and current applications are presented and discussed.
Magnetostratigraphic correlations of the Jurassic carbonates from the Paris Basin: implications for petroleum exploration
Authors: Belkaaloul Kifaya N. , Aissaoui Djafar M. , Rebelle Michel , Sambet Gerard
Published: April 2008

Shallow water carbonates from the Middle Jurassic of the Paris Basin include oil reservoirs, mainly oolitic and bioclastic limestones. Biostratigraphic markers within these deposits are generally used for regional correlations. Unfortunately, these markers are not available in all cored sections. A pilot study has shown that palaeomagnetism could be used to better constrain the chronostratigraphic framework of the Jurassic shallow water carbonates. Because the magnetization of sediments is independent of facies and location, palaeomagnetic dating may allow higher resolution.

Further magnetostratigraphic results are reported for three additional well dated core sections (53, 18.50 and 36.35 m in length) correlated throughout the Paris Basin. Specimens were subjected to alternating field and stepwise thermal demagnetization. The demagnetization paths show either one, two or three components. Based on the primary magnetization component, normal and reverse polarity intervals occur in the three sections. Rock magnetic experiments performed on representative specimens from both sections indicate that the bulk of the natural remanent magnetization is carried mainly by low coercivity minerals such as magnetite/maghemite and high coercivity minerals exclusively in altered layers of the cores. Single domain maghemite, probably biogenic in origin, has been observed by transmission electron microscopy. Larger detrital irregular titanomagnetite and secondary, framboidal magnetite spheres have been characterized with a scanning electron microprobe. The occurrence of the secondary magnetic spheres is probably related to the transformation of framboidal pyrite into magnetite during hydrocarbon migration. This has presumably resulted in the overprint of a secondary magnetization.

The polarity sequences have been correlated with the magnetostratigraphic record defined for the Bathonian and Callovian. The correlation is fairly good for the Bathonian, but ambiguous for the Callovian. However, we used a characteristic reverse polarity interval occurring in all our cores, including that studied previously, to correlate strata throughout the Paris Basin. The positive correlation within these strata provides a strong potential for the analysis of reservoir geometry and quantitative modelling of the Middle Jurassic shallow water carbonates.
Palaeomagnetic study of Cenozoic sediments in North Sea boreholes: an example of a magnetostratigraphic conundrum in a hydrocarbonproducing area
Authors: Thompson R. , Cameron T. D. J.
Published: April 2008

Palaeomagnetic measurements from a southern North Sea borehole that penetrated 13 m of Holocene, 189 m of Plio-Pleistocene and 4 m of Oligocene sediments have yielded six polarity changes. One polarity boundary coincides with a regional mid-Tertiary unconformity and a second occurs at the base of the Holocene section. The other four boundaries are interpreted as the Kaena-Gauss and the Gauss-Matuyama polarity transitions, and the base and top of the Olduvai subchron. The borehole results provide a chronological framework for interpreting nearby seismic sections and for assessing the sedimentation rates as a major Plio-Pleistocene delta complex approached and then overwhelmed the borehold site. Rock magnetic and X-ray diffraction work show that the iron sulphide greigite is an important magnetic mineral in the prodelta and delta front marine clays and lagoonal delta top clays, whereas magnetite is the dominant magnetic mineral in the fluvio-deltaic sands and in the Holocene and Oligocene marine deposits. Thermal demagnetization studies demonstrate that the greigite carries a stable natural remanent magnetization. It may have formed through sulphide diagenesis induced by hydrocarbon seepage or in a reducing sedimentary environment. Greigite is surprisingly difficult to detect through the standard palaeomagnetic method of alternating field demagnetization and may be of much greater palaeomagnetic importance in hydrocarbon-producing areas than previously supposed.
Viscous remanent magnetization: a tool for orientation of drill cores
Authors: Rolph T. C. , Shaw J. , Harper T. R. , Hagan J. T.
Published: April 2008

To interpret the directional physical properties of reservoirs it is necessary to obtain orientated specimens of well material. The standard technique in the petroleum industry has been the use of ‘down the hole’ tools, which leave a physical scribe on the core material during the drilling procedure. This method is expensive and is subject to a number of problems which can limit the accuracy of the results. A new orientation technique is presented in which a present day component of magnetization is isolated during the progressive thermal demagnetization of core material. This component is essentially a magnetic compass bearing for the core which can be used to rotate the core reference frame into the geographical system. Unlike the standard palaeomagnetic method it can be used both on undated core and core taken from complex tectonic areas.
Palaeomagnetic analysis of fold closure growth and volumetrics
Authors: Stewart S. A. , Jackson K. C.
Published: April 2008

Fold closures (four-way dip closures) occur in several tectonic environments. These closures must attain lengths and widths of several kilometres before they can contain economically significant amounts of hydrocarbons. The growth kinematics of such large structures differ in some respects from those of geometrically similar, but smaller structures. Key aspects of the kinematics of large-scale fold structures are described, illustrated by new palaeomagnetic data from an example in the Salt Range of Pakistan. A numerical model describing the geometry of four-way dip closure is developed, relating the bulk volume to tangible geological parameters (limb dip, fold amplitude). An understanding of growth kinematics enables the application of a ‘fold test’, which provides a restoration of the palaeomagnetic data and host beds back to their attitudes at the time of magnetization. Comparison of the restored data with magnetic directions of known ages reveals the time of magnetization, so the geometry of the structure, including bulk volume at a known time, can be estimated. These data enable a curve describing the evolution of bulk volume through time to be calculated, which can be compared with the burial history of local source rocks — hence the trap volume available at the time of hydrocarbon generation can be estimated.
Searching for extinction/recovery gradients: the Frasnian-Famennian interval, Mokrá Section, Moravia, central Europe
Authors: Čejchan Petr , Hladil Jindřich
Published: April 2008

A series of ancient seafloors colonized by diverse organisms has been documented from the Upper Devonian rocks of the Western Mokrá Quarry. Situated in the southern tectonic closure of the Moravian Karst, the Frasnian-Famennian shallow carbonate ramps exhibit both Rhenish and Ukrainian affinities. Reconstruction of palaeo-sea floor horizons results in a series of 28 quadrats sufficient for further evaluation. Eighty-five taxa involved were scrutinized for abundance, occupied area, skeletal mass production and biomass production. The aim of the study was to determine whether the observed sequence of quadrats can be distinguished from a random one, and to discover any possible unidimensional gradient as a latent control. Monte Carlo simulations and a graph theoretical approach were utilized. Although the raw data seemed chaotic, the simulations demonstrated the observed sequence is not random. A significant influence of a hidden control is thus suggested. Fifteen characteristics of quadrats (e.g. diversity, number of taxa, vertical stratification of community, number of patches) were utilized for final interpretation. The gradient reconstructed by TSP algorithm reveals a significant crisis within the uppermost part of the
Amphipora
-bearing limestone.
Recovery of the marine fauna in Europe after the end-Triassic and Early Toarcian mass Extinctions
Authors: Hallam A.
Published: April 2008

A detailed analysis of species diversity increase, zone by zone up the Liassic section in northwest Europe, has been undertaken for the six fossil groups for which adequate data are available: bivalves, ammonites, rhynchonellid brachiopods, crinoids, foraminifera and ostracods. The general pattern is of a rapid increase through the Hettangian from a very low level after the end-Triassic mass extinction, followed by a slower rate of increase until the late Pliensbachian. Thereafter there was a drastic fall in the early Toarcian as a consequence of the mass extinction of that time, followed by a further rise continuing into the Middle Jurassic. A more general study takes into account data from southern Europe and extra-European localities, the best of which for the Liassic being in Argentina and Chile. The best data come from brachiopods and bivalves. The brachiopod pattern is similar to that described above for a more limited geographical region, with genera already occurring in the Hettangian and Sinemurian of southern Europe spreading into northwest Europe in the Pliensbachian. The bivalve data show that genera present in the Sinemurian and Pliensbachian of South America did not reach Europe until after the late Toarcian and early Middle Jurassic. Reef ecosystems, which were drastically affected by the end-Triassic mass extinction, did not re-establish themselves until the Pliensbachian; the early Toarcian event had a similarly deleterious effect.

There is a good correlation between the Hettangian to Pliensbachian diversity rise and rise of sea level, with the very low diversity values of the early Hettangian being associated with widespread dysoxic and anoxic conditions. The low diversities of the early Toarcian are also associated with anoxia correlated with a rapid sea-level rise, with the immigration into Europe of South American taxa taking place subsequently when environmental conditions ameliorated and the higher sea level permitted freer communication, most probably through the Hispanic Corridor across the present Central Atlantic region.
Foraminiferal recovery after the mid-Cretaceous oceanic anoxic events (OAEs) in the Cauvery Basin, southeast India
Authors: Tewari A. , Hart M. B. , Watkinson M. P.
Published: April 2008

The Cauvery Basin, SE India, is one of the best exposed late Mesozoic to Tertiary basins in India. The study of foraminiferal assemblages from the core samples obtained from two 120m deep wells in the basin records the occurrence of two mid-Cretaceous anoxic events in the basin. Abrupt increases in planktonic: benthonic ratios and reductions in benthonic diversity are recorded in the late Albian and in the late Cenomanian-early Turonian. These events coincide with worldwide oceanic anoxic events (OAEs).

The OAEs had an impact on the microfauna of the basin, with approximately 35–45% of the benthonic species not surviving and major morphological changes occurring in the planktonic community. The late Cenomanian-early Turonian event was more significant than the late Albian event, with considerable readjustments occurring in the planktonic foraminifera. The genusRotaliporadisappeared and the genusHedbergellawas largely replaced byWhiteinella. Marginotruncanaappeared for the first time and theDicarinellapopulation expanded considerably.Praeglobotruncanawas the most tolerant genus, undergoing least change. The planktonic foraminifera evolved from small, weakly ornamented forms with poorly developed keels, into robust, well ornamented forms with well developed keels. The pattern of evolution of planktonic foraminifera suggests a recolonization of deeper water environments after the late Cenomanian-early Turonian anoxic event.
Recovery of the food chain after the Late Cenomanian extinction event
Authors: Hart M. B.
Published: April 2008

The Late Cenomanian bio-event is accepted as a globally synchronous extinction event that is characterized by significant biological changes which are coincident with isotopic and geochemical anomalies. The extinction event is characterized by changes on the macro-, meio-, micro- and nanno-scale and, in many examples, it has been suggested that these are ‘step-wise’. In the United Kingdom successions the steps are emphasized by depositional non-sequences, but in all cases the biological changes are in the same order. In microfaunal terms this involves a marked reduction in the benthonic foraminifera followed closely by a restriction of the planktonic foraminifera to surface-dwelling morphotypes. The event is also characterized by short-lived floods of
Heterohelix
sp. (small, biserial planktonic foraminiferids),
Bulimina
sp. (small, benthonic foraminiferids often characteristic of low-oxygen environments, calcispheres (?calcified dinoflagellates) and radiolaria. Following the extinction events, in the very latest Cenomanian, the recovery phase begins. Almost immediately the calcareous nannoplankton flora is restored but the dinoflagellates do not recover until much later in the Turonian. The benthonic foraminifera recover slowly with the fauna of the Early Turonian being of low diversity, with long-ranging taxa — including a large (?deep water), internally complex, agglutinated genus (
Labyrinthidoma
). The planktonic foraminifera recovered quickly with the
Praeglobotruncana, Dicarinella
, and
Marginotruncana
faunas appearing in succession within 100 000–200 000 years of the end of the extinction event. Using a model of the normal food chain it is possible to identify the order in which the basic building blocks needed for ecosystem recovery are put in place following the extinction event.
Recovery of Turonian dinoflagellate cyst assemblages from the effects of the oceanic anoxic event at the end of the Cenomanian in southern England
Authors: Fitzpatrick M. E. J.
Published: April 2008

The oceanic anoxic event during the latest Cenomanian caused the decline and temporary extinction of many species of marine micro-flora and -fauna. Many of these species reappeared during the Turonian. The recovery of the marine phytoplankton population after the oceanic anoxic event is examined. Detailed sampling of Turonian sediments from Kent, Sussex and the Isle of Wight (southern England) was undertaken to analyse the changes in the dinoflagellate cyst assemblages through time. Chalk, marl and flint samples were collected with no bias. Abundance and diversity of the assemblages varies greatly between sections and samples. Assemblages at the base of the Turonian (the Melbourn Rock Beds) are poor to barren. This is attributed to the lasting effect of the latest Cenomanian oceanic anoxic event. There is a general increase in diversity and abundance upwards through the succession, although assemblages never reach the richness that is seen in other Cenomanian sections.
Post-crisis recovery of Campanian desmoceratacean ammonites from Sakhalin, far east Russia
Authors: Yazykova Elena A.
Published: April 2008

The Santonian-Campanian boundary in Sakhalin marks a major Cretaceous mass extinction event. In the late Santonian there was a decrease in the taxonomic diversity of ammonoids as well as significant changes in shell morphology which were probably related to a global regression event. However, the fauna of the Pacific region is endemic and precise correlation between the Pacific and European regions is impossible. In this paper the stratigraphic position of the boundary between the Santonian and Campanian in Sakhalin is revised and the post-crisis recovery of the ammonoid diversity is discussed. Detailed sampling of the Santonian-Campanian sequence of Sakhalin (Naiba section, Orlovka section and others) allows identification of the phyllogenetic links between the different ammonite morphotypes in the pre-crisis communities. Comparison with adjacent regions in northeast Russia and Japan is also attempted. The ammonite extinctions at the Santonian-Campanian boundary are a good marker for stratigraphic correlation. During the crisis event ammonites of the superfamilies Acanthocerataceae and Desmocerataceae were affected most strongly whereas phylloceratids and lytoceratids were not significantly changed at that time. Heteromorphic ammonites are not discussed here. The pre-crisis community is characterized by a predominance of Acanthocerataceae, while the Desmocerataceae had a subordinate role. Representatives of these two groups form a community with large-size shells and strong ornamentation and this is not seen in the ammonites of the post-crisis community. The maximum occurrence of the Superfamily Desmocerataceae is recorded in the Middle Campanian, when the first diversification occurred (Family Pachydiscidae). Zonal correlation of the Santonian to Campanian succession of northeast Russia and Japan is discussed.
Extinction and survivorship of southern Tethyan Benthic foraminifera across the Cretaceous/Palaeogene boundary
Authors: Speijer R. P. , Van Der Zwaan G. J.
Published: April 2008

The benthic foraminiferal record from the Cretaceous/Palaeogene boundary stratotype of El Kef, Tunisia, shows a succession of three distinct assemblages. The late Maastrichtian upper bathyal assemblage is highly diversified and shows no prominent signs of gradual change towards the boundary. The earliest Palaeocene is marked by the disappearance of more than 50% of the taxa, resulting in a strongly impoverished fauna, tolerant to low oxygen conditions and with a shallower water affinity. Sequential (re-) appearance of many taxa in the early Palaeocene signifies the restoration towards normal Palaeocene upper bathyal faunas. The faunal changes reflect major perturbations in redox and trophic conditions at the sea-floor.

At least locally, and perhaps even on a regional Tethyan scale, the extinctions can be related to a sharp decrease in oxygen supply, in combination with strongly reduced nutrient resources. It is suggested that a prolonged reduction in surface fertility and food flux to the sea-floor invoked worldwide (but diachronous) benthic extinctions. In particular endo-benthic deposit feeders and other taxa adapted to high and perhaps heterogeneous nutrient resources suffered extinction.
Recovery of the naticid gastropod predator-prey system from the Cretaceous-Tertiary and Eocene-Oligocene extinctions
Authors: Kelley Patricia H. , Hansen Thor A.
Published: April 2008

Naticid gastropods have been important shell-drilling predators of molluscs since the Cretaceous. Preliminary compilations of drilling frequencies by Vermeij (1987) were used to support his hypothesis of escalation, involving temporal increase in the hazard of predation and in adaptation to this hazard.

A comprehensive survey of naticid predation on molluscs in the Cretaceous and Palaeogene of the North American Coastal Plain revealed a complex pattern of escalation influenced by mass extinctions and recoveries. Data from more than 46 000 specimens from 17 formations show that dynamics of the naticid predator-prey system were affected significantly by the Cretaceous-Tertiary and Eocene-Oligocene mass extinctions. In the Cretaceous, drilling was low for gastropod prey (4–6%) and moderate for bivalves (13–19%). Drilling frequencies significantly increased above the K/T boundary in an initial recovery phase that lasted no more than 1–3 Ma. Recovery from the Eocene-Oligocene extinction also involved a significant increase in drilling, especially on bivalves (from 8% to 24%).

Based on these data (and similar patterns reported for fossil ostracode prey), we propose a model of cyclic escalation of the naticid predator-prey system, in which mass extinctions perturb the system and initiate cycles. Drilling frequencies in recovery faunas are greatly increased, possibly owing to preferential extinction of highly escalated prey. As the recovery proceeds, escalation of prey defences causes drilling frequencies to stabilize or decline. Reorganization of the predator-prey system also involves reduction in predator behavioural stereotypy after mass extinctions, followed by gradual recovery.
Balancing sections through inverted basins
Authors: Coward Mike P.
Published: April 2008

Basin inversion and the reactivation of earlier normal faults is now recognized as being widespread in many mountain belts. By ignoring the effects of basin inversion, serious errors in section construction and structural and tectonic interpretations can be made.

Folds produced during thick-skinned basement-involved faulting are generally very different from those produced during thin-skinned thrust tectonics and hence different models must be used for section construction and restoration. In particular, block rotations are important. Rotation about a horizontal axis may lead to shortening of the graben or half-graben, expulsion of material from out of the graben and/or reactivation of the original normal fault. The resultant hanging wall folds are characterized by long gently dipping backlimbs and short hooked forelimbs. Various models for fold development are derived and compared for different inversion geometries and kinematics. Examples are taken from the North Sea.

Many inverted faults involve components of strike-slip or oblique-slip movement, and hence simple 2D methods of section balancing cannot be applied. Basin inversion may have involved rotation of the fault blocks about vertical axes and/or lateral expulsion of material from the basin. Examples are described from South Wales, Syria and the French Alps. Vertical axis rotation appears a common mechanism for intraplate deformation, where the regional shear couple is applied at an angle to earlier fault blocks or crustal lineaments. The analysis of paleomagnetic data together with kinematic data enable the rotation to be determined and amounts of shortening strain estimated.
A strategy for palinspastic restoration of inverted basins: thermal and structural analyses in SE Australia
Authors: Hill Kevin C. , Cooper Gareth T.
Published: April 2008

Constructing balanced sections across inverted basins is difficult because of the different directions of tectonic transport during extension and compression and the imprecise estimates of the magnitude and timing of inversion events. Sections oriented within 25° of all transport directions can be restored and result in ≤10% error in the amount of extension-compression. Extensional faults are commonly oblique to the transport direction, so the inferred extension direction may be verified by dip analysis of the pre-rift section. Where oblique extensional faults are reactivated during compression, the compressional vector is best determined from the orientation and magnitude of large, curved inversion anticlines. For strongly inverted and eroded anticlines, where
T
max
is not at the present day, palaeotemperature gradients determined regionally from borehole vitrinite reflectance and fission track profiles constrain the amount of denudation allowing reconstruction of the original anticline morphology. The timing of inversion and erosion determined by apatite fission track analysis allow the eroded strata to be replaced on the section and the inversion restored to reveal the amounts of extension and compression and the syn-rift basin morphology, which may constrain hydrocarbon migration paths. For the Otway Ranges in SE Australia 45% Early Cretaceous extension followed by 10% mid-Cretaceous compression are inferred.
Benefits and limitations of section restoration in areas of extensional salt tectonics: an example from offshore Louisiana
Authors: Rowan Mark G.
Published: April 2008

A composite, multi-level salt system from offshore Louisiana is used to illustrate some benefits and limitations of cross section restoration. The system has a complex three-dimensional geometry in which both salt and overburden have apparently moved in multiple directions during Miocene-Pleistocene deformation. Sequential restorations are beneficial in that they provide a framework for: (1) analysis of the structural evolution of salt and overburden; (2) determination of rates of various processes; (3) prediction of changes in the sea-floor paleotopography; (4) evaluation of evolving sediment transport and deposition systems; and (5) analysis of the timing and pathways of hydrocarbon migration. The limitations of section restoration include possible inadequacies of restoration algorithms to model correctly actual rock deformation. More importantly, the assumption of plane-strain deformation is shown to be invalid in this example. Local pin lines are used to demonstrate that there is significant out-of-plane movement. Thus, cross-sectional area for both salt and overburden may need to be added or removed from the section during restoration if the goals are to illustrate the geometric evolution. If, on the other hand, the goal of restoration is to validate and, if necessary, modify the interpretation, then 2D restoration is not appropriate in this case. Ultimately, 3D restoration is needed to restore accurately complex structural geometries.
The growth of normal faults by segment linkage
Authors: Cartwright Joseph A. , Mansfield Chris , Trudgill Bruce
Published: April 2008

Fault growth is widely described using a scaling law between maximum displacement (
D
) and length (
L
), of the form
D
=

cL
n

. This expression defines a model of fault growth by radial propagation from a single seed fracture or fault. This paper presents geometrical and kinematic evidence from a set of exceptionally well exposed normal faults in Utah for an alternative model of fault growth. This model is referred to as growth by segment linkage, and involves the propagation and linkage of independent fault segments on ascending length scales. The evidence presented focuses on the geometry and displacement variation in the region of relay structures, and on local scaling relationships between
D
and
L
. The
D - L
data from 97 faults in the study area range over three orders of magnitude, and show a general trend to increasing
D
for increasing
L
. There is a large scatter in the data, similar to that recognized in previous
D - L
compilations. It is argued that the scatter cannot be attributed either to measurement errors or to variation in mechanical properties. Instead, we argue that the model of growth by segment linkage provides a simple explanation of this scatter, and propose that the process of segment linkage may explain scatter in other datasets.
Recent advances in analogue modelling: uses in section interpretation and validation
Authors: McClay K. R.
Published: April 2008

Scaled analogue modelling is a powerful tool for the understanding of the geometric and kinematic development of extensional, strike-slip and inverted fault systems, as well as for some thrust systems. In this paper the results of 2D and 3D scaled analogue model experiments designed to simulate listric fault systems, rift fault systems, and inverted listric faults are reviewed. Simple 2D rift models are characterized by asymmetric rift graben structures with planar rift border faults and domino-style intra-rift fault systems. 2D listric fault models produce roll-over anticlines with associated crestal collapse grabens whereas the ramp-flat listric fault models produce roll-over anticlines associated with each concave-up segment of the main fault system and also a syncline above the convex-up ramp section of the main detachment. The 2D analogue models are directly comparable to natural examples of extensional fault systems. The results of simple 3D analogue models of an orthogonal and a 60° oblique rift are presented. Orthogonal rift models are characterized by both rift-border and intra-rift faults that are nearly orthogonal to the extension direction. Like-dipping intra-rift faults overlap to form relay ramps that transfer displacement between the faults. In contrast oblique rift models are characterized by en-echelon arrays of segmented extensional faults. Rift border fault systems are parallel to the underlying zone of basement stretching whereas the intra-rift faults are segmented and at a high angle to the extension direction. Oblique accommodation zones formed by interlocking conjugate fault arrays separate individual depocentres within the models. No strike-slip or oblique-slip transfer faults are found in these models. The 3D rift models produce fault patterns that are comparable with natural examples of rift systems. Analogue modelling of inverted listric faults is described and the results compared with natural examples of inverted fault systems. The results of the scaled analogue models described in this paper provide important constraints on section interpretation and restoration in that they permit an understanding of the geometric and kinematic evolution of fault (and fold) structures as well as indicating the sequences of faulting and activity on faults. They provide templates for the interpretation of seismic sections in regions of poor data quality and for projecting surface data into the sub-surface.
Numerical modelling of extension in faulted crust: effects of localized and regional deformation on basin stratigraphy
Authors: Ter Voorde M. , Cloetingh S.
Published: April 2008

A numerical model for localized and regional deformation during crustal extension is presented. In this model, the behaviour of the faulted upper crust is coupled with ductile deformation in the lower crust and upper mantle. The incorporation of finite extension rates makes the model an appropriate tool for analysing the effects of synrift processes on the basin structure and stratigraphy.

Modelling results indicate that the shape of a basin depends not only on the fault geometry and the deformation mechanism, but also on the behaviour of the lower lithosphere. The authors demonstrate that onlap and offlap patterns can be caused by successive activation of a series of faults.

As shown by the modelling, the amount of footwall uplift of the fault blocks is determined by the integrated effects of deep-lithospheric and near-surface processes. Of particular importance are the spacing of the faults, the amount of extension, the depth of necking, the depth of the Moho, and the lithospheric rigidity. The rate of extension turns out to be a very important but undervalued factor for the postrift to synrift sediment thickness ratio. It is shown that this ratio increases with the extension velocity.
The role of pre-existing faults in basin evolution: constraints from 2D finite element and 3D flexure models
Authors: Van Wees J. D. , Cloetingh S. , de Vicente G.
Published: April 2008

The lithospheric driving forces which cause intraplate basin deformation are relatively constant over large areas. Consequently, lateral variations in deformation and stress and strain concentrations seem to be primarily caused by (pre-existing) heterogenities in the rheological signature of the continental lithosphere underlying the sedimentary basins. In this paper, we explore the weak character of upper crustal faults and their control on basin shape for a number of case studies on intraplate Phanerozoic basin settings, using a 2D finite element and a 3D flexure model. Of key importance is the integration of seismic data and field observations with the tectonic modelling, allowing the investigation of deformation processes and their expressions on different scales, operating on different levels of the lithosphere. Finite element models for sub-basin scales, incorporating weak upper crustal faults, predict strong control of these weak zones on local stress distributions and subsequent deformation, in agreement with observed deformation patterns. Slip along upper crustal faults control stress distribution and subsequent faulting in overlying sedimentary rocks. The effect of weak upper crustal fault movements on basin-wide (regional) upper crustal flexure is looked at in two case studies on: (1) extensional tectonics in the Lake Tanganyika Rift Zone (East Africa); and (2) compressional tectonics in the Central System and Tajo Basin (Central Spain). Both settings indicate that basement warpings are controlled by large amounts of slip along so-called weak crustal-scale border faults, which are mostly planar. Adopting border fault displacements in the 3D flexure model, the results indicate low effective elastic thickness (EET) values in a range of 3–7 km for induced basement deflection patterns in accordance with observations. The low EET values most likely reflect a (partly) decoupling of upper crustal and subcrustal deformation, facilitated by the weak lower crust, and in agreement with standard rheological assumptions for Phanerozoic lithosphere. In contrast, the inferred weakness of upper crustal faults relative to surrounding rock is not evident from uniform rheological assumptions. However, observations of reactivations of faults which are not preferably aligned with the stress field, and reactivations of basin deformation on long time-scales are in support of this feature.
The use of satellite imagery in the validation and verification of structural interpretations for hydrocarbon exploration in Pakistan and Yemen
Authors: Insley M. W. , Murphy F. X. , Naylor D. , Critchley M.
Published: April 2008

Landsat TM and stereo-SPOT satellite imagery has an important application in the validation and verification of structural models for on-shore hydrocarbon exploration. The lithological discrimination of Landsat TM can be merged with the higher resolution panchromatic stereo-SPOT imagery to produce detailed geological maps at scales of 1:25 000 and 1:50 000 from which to ‘hang’ structural cross-sections. In addition, the calculation of surface dip data and fault off-sets, as well as the construction of structure contour and topographic maps is now possible using SPOT-derived digital elevation models (DEMs), thus providing the necessary information for the construction of structural cross-sections.

Examples of the use of satellite imagery are presented from the Sulaiman Ranges of Pakistan and southeast Yemen. For the Sulaiman Ranges of Pakistan, satellite imagery has been used to constrain the construction of a balanced deformed and restored cross-section from relatively poor quality seismic data. The satellite imagery provides information on structural style and along-strike structural continuity. The construction of a balanced cross-section is used to highlight the contrast between the position of structural closure at surface and subsurface.

In southeast Yemen, satellite imagery is combined with both field and seismic data to develop a viable structural interpretation. The model is complicated by the superposition of Late Tertiary extensional structures on an earlier Mesozoic rift system. Earlier structural trends have been inferred from the interpretation and analysis of the Late Tertiary fault patterns observed on the Landsat MSS and TM and stereo-SPOT imagery. Stereo-SPOT imagery is used at 1:50 000 scale to map out extensional faults, to examine their displacement gradients and identify potential closures at surface. Quantitative analysis of displacement patterns around faults is possible using structure contour maps derived from stereo-SPOT imagery and DEMs. Satellite imagery also enables the validation of structural continuity between seismic lines.
Gravity-driven nappes and their relation to palaeobathymetry: examples from West Africa and Cardigan Bay, UK
Authors: Turner Jonathan P.
Published: April 2008

Gravity-tectonics serves to reduce gravitational potential compared to the undeformed state. Consequently, a common setting of gravity-driven faulting is at actively prograding passive margin basins where abrupt shelf-edge relief promotes potentials sufficiently large to induce and sustain large-scale deformation. In the West African Rio Muni basin, Albian gravity-tectonics predates the Senonian drift unconformity and owes its existence to a significant bathymetric deep that characterized the late syn-rift stage of the basin. Thin-skin nappes, detaching on a syn-rift salt and/or shaly horizon, emplace shallow water shelf carbonates in a deep, basinal setting. Seismic mapping indicates that ‘upslope’ extension occurred contemporaneously with ‘downslope’ contraction and that the nappes behaved as small coulomb wedges. It is suggested that structural restoration of these large-scale nappes, retro-deforming them to their pre-deformational position at the palaeo-shelf edge, yields a minimum estimate of palaeobathymetry. In the Rio Muni basin, variations in the inferred palaeobathymetry accord with intra-basinal differences in Bouguer gravity anomaly, here interpreted as an expression of varying crustal thickness and uplift/subsidence rate. Comparable structures in the Jurassic of the UK Cardigan Bay basin occur at the margin of a basin characterized, similarly, by a major negative Bouguer gravity anomaly and which, from evidence on seismic profiles, clearly experienced deep bathymetry during Jurassic deposition.