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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Terra nova 4 (1992), S. 0 
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Quantitative subsidence analysis for a number of rifted basins in the northern Atlantic/Mediterranean region provides evidence for rapid phases of PlioQuaternary subsidence. The observed acceleration in tectonic subsidence occurs after a phase of general quiescence in subsidence in these basins and deviates from predictions of stretching models. The latter indicate a decay of subsidence with time after Mesozoic-Tertiary basin formatioh and a slow tectonic subsidence in Plio-Quaternary times. A possible explanation for the observed patterns of anomalous subsidence could be an increase in the level of intraplate compression in the northern Atlantic region. Intraplate stress changes in the Plio-Quaternary are related to the dynamics of African/ Eurasian collision processes and a reorganization of spreading directions in the AtlAntic, possibly reflecting a plate reorganization of global nature.It seems that the Plio-Quaternary record reflects a period of increased levels of neotectonic activity, interplaying with periods of (de)glaciation. Stress-induced topography in the onshore parts of continental margins, coupled with the stress-induced subsidence in the offshore deeper parts of the basins, could have contributed to recent phases of uplift in Fennoscandia, augmenting the uplift induced by glacial unloading. Estimates of ice thicknesses are directly inferred from the observed uplift ignoring other driving mechanisms whereas topography plays a crucial role in the dynamics of glaciation. It is, therefore, important to quantdy the interplay of rapid tectonic uplift and subsidence phases with climatic effects during the Plio-Quaternary.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 111 (1992), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: We present a conceptual model for short-term and long-term alternations in subsidence and uplift in foreland basins. Convergence of lithospheric plates produces forces at the plate boundaries, generating stresses in the accretionary wedge, the underthrusted crust, and the lithosphere. When the stresses reach the shear strength of the rocks in these units, deformation, which results in the redistribution of mass, takes place contemporaneously with reduction of the stress level. Modelling of both the effects of this alternating building up and relaxation of stress, and the effects of the resulting mass redistribution on foreland basin geometry, employing an elastic rheology of the lithosphere, demonstrates that these processes exert an important control on the shape of foreland basins. Vertical motions take place on different time-scales dependent on the scale of thrusting and the style of deformation. Short-term (10–104 yr) vertical motions are related to small-scale thrust events, while long-term vertical motions are induced by larger scale deformation in the overriding thrust wedge. Furthermore, the geometry of faults influences the duration of the magnitude of stress fluctuations.Stress-induced alternations of subsidence may lead to the deposition of alternating sequences in foreland basins on scales of centimetres (e.g. cyclothems) to scales of several hundreds of metres (on-lap and off-lap sequences). In this respect, the mechanical coupling between convergent zones and peripheral areas is of particular importance, as it induces simultaneous alternations in regional facies patterns. The model also provides an explanation for vertical motions in the foreland basin previously attributed to visco-elastic relaxation processes.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 124 (1996), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The EET (equivalent elastic thickness) of the lithosphere is a measure of the integrated lithospheric strength. It is directly related to the mechanical thickness and rheology of the crustal and mantle lithosphere. We present a comparison of EET estimates and strength profiles based on the extrapolation of rock mechanics data for different parts of the European and Eurasian continental lithosphere. We discuss the temporal and spatial variations in the mechanical thickness and strength inferred from data for Precambrian segments of Europe's lithosphere, Variscan Europe and the Alpine collision belt. This analysis demonstrates important spatial and temporal variations in lithospheric rigidity for orogenic belts and sedimentary basins in eastern and western Europe and Asian parts of Eurasia. The EET estimates based on synthetic rheological profiles constrained by newly available geophysical data are consistent with the estimates of EET derived from flexural studies of sedimentary basins, forelands and orogenic belts. These rheological profiles suggest weakening of the major parts of the European and Eurasian continental lithosphere by decoupling of the crustal and upper-mantle parts- A comparison with the seismicity-depth distribution for some selected sites suggests that the intra-plate seismicity is essentially restricted to the upper crustal parts of Europe's lithosphere, providing additional support to the notion of the decoupled lithosphere. The presence of intra-plate stress fields can explain a significant part of the observed variations in EET estimates within individual thermotectonic age groups. A comparison of wavelengths of crustal and lithospheric folding with observations shows these wavelengths to be consistent with estimates of EET inferred from the rheological response of basins and orogens at more moderate levels of intra-plate stress.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of earth sciences 78 (1989), S. 183-195 
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract Changes in intraplate stress levels have important consequences for the stratigraphy of rifted basins and provide a tectonic explanation for the generation of sequence boundaries. Late-stage compressional phases during the post-rift evolution of basins produce unconformities, with offlap phases that increase in magnitude with the age of the rifted basin. Late-stage compression has not only a strong bearing on the generation of unconformities, but also induces significant downbending of the centre of a basin. Ignorance of the vertical motions of the lithosphere induced by late-stage compression during post-rift evolution can, therefore, give rise to substantial errors in the estimates of crustal extension derived from analysis of basement subsidence using stretching models. Consequently, late-stage compression can be of great significance in estimates of depth and timing of the hydrocarbon-window inferred from extensional models of basin subsidence. Quantification of the subsidence induced by post-rift compression has important implications for integrated models of basin subsidence and hydrocarbon generation.
    Abstract: Résumé Les changements dans la distribution des contraintes à l'intérieur des plaques ont des répercussions importantes sur la stratigraphie dans les bassins de rift et fournissent une explication tectonique de la limitation latérale des séries. Des épisodes compressifs tardifs, qui marquent l'évolution postrift des bassins, sont à l'origine de lacunes dans lesquelles l'importance des phases régressives augmente avec l'áge du bassin. Les mouvements verticaux de la lithosphère induits par ces épisodes tardifs de compression n'étant pas connus, il peut en résulter des erreurs non négligeables dans l'estimation de l'allongement crustal, telle qu'elle est déduite de la valeur de la subsidence du socle dans des modèles d'extension. Dans ces conditions, l'évaluation quantitative de la subsidence produite par les compressions post-rift doit être prise en considération dans l'élaboration des modèles qui rendent compte de la subsidence des bassins par les processus d'extension.
    Notes: Zusammenfassung Unterschiede in platteninternen Streß-Niveaus haben entscheidende Auswirkungen für die Stratigraphie von Rift-Becken und liefern eine tektonische Erklärung für die Erzeugung von Sequenzgrenzen. Späte kompressive Phasen während der post-Rift-Entwicklung von Becken erzeugen Umkonformitäten mit offlap-Phasen, deren Ausmaß mit dem Alter des Rift-Beckens steigt. Entscheidende Fehlerquellen in der Abschätzung der Krustendehnung können darauf basieren, daß die durch späte Kompression während der post-Rift-Entwicklung ausgelösten Vertikalbewegungen der Lithosphäre ignoriert werden. Das Ausmaß der Krustendehnung wird durch Analysen der Basement-Subsidenz mit Hilfe von Dehnungsmodellen entwickelt. Die Quantifizierung der Subsidenz, die von der post-Rift-Kompression gesteuert wird, hat also wichtige Bedeutungen für Extensionsmodelle von Beckensubsidenz.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 129 (1989), S. 7-25 
    ISSN: 1420-9136
    Keywords: Initiation of subduction ; passive to active margin transition ; preservation of back-arc basins ; emplacement of ophiolites ; mechanics of plate boundary formation ; Wilson cycle ; plate reorganizations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Analysis of the relation between intraplate stress fields and lithospheric rheology leads to greater insight into the role that initiation of subduction plays in the tectonic evolution of the lithosphere. Numerical model studies show that if after a short evolution of a passive margin (time span a few tens of million years) subduction has not yet started, continued aging of the passive margin alone does not result in conditions more favorable for transformation into an active margin. Although much geological evidence is available in supporting the key role small ocean basins play in orogeny and ophiolite emplacement, evolutionary frameworks of the Wilson cycle usually are cast in terms of opening and closing of wide ocean basins. We propose a more limited role for large oceans in the Wilson cycle concept. In general, initiation of subduction at passive margins requires the action of external plate-tectonic forces, which will be most effective for young passive margins prestressed by thick sedimentary loads. It is not clear how major subduction zones (such as those presently ringing the Pacific Basin) form but it is unlikely they form merely by aging of oceanic lithosphere. Conditions likely to exist in very young oceanic regions are quite favorable for the development of subduction zones, which might explain the lack of preservation of back-arc basins and marginal seas. Plate reorganizations probably occur predominantly by the formation of new spreading ridges, because stress relaxation in the lithosphere takes place much more efficiently through this process than through the formation of new subduction zones.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2008-10-08
    Description: Poly-phase deformation of a compressional nature is a common feature in the post-rift evolution of passive margins and rifts. The compressional mode of deformation in these sedimentary basins, originally formed by extension in an intraplate setting, is characterized by a spectrum of spatial wavelengths spanning several tens of kilometres up to several hundreds of kilometres. The actual mode of compressional deformation appears to be strongly affected by the rheological structure of the underlying lithosphere, the level of the regional intraplate stress field, and the geometry of the rifted basin configuration prior to late-stage compressional reactivation. The interplay of plumes and intraplate compressional deformation can lead to temporal transitions from basin inversion to lithospheric folding. These modes of deformation lead to substantial differential vertical motions, late-stage anomalies in subsidence and uplift patterns. The development of innovative combinations of numerical and analogue modelling techniques is the key to differentiating different modes of compressional deformation of passive margins and extensional basins.
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  • 7
    Publication Date: 2007-10-08
    Description: Compared to other Permo-Carboniferous rift basins of NW Europe, the Oslo Graben has two distinct characteristics. First, it initiated inside cold and stable Precambrian lithosphere, whereas most Permo-Carboniferous basins developed in weaker Phanerozoic lithosphere, and second, it is characterized by large volumes of magmatic rocks despite relatively little extension. Seismic reflection surveys show that the crust thickens from southern Norway to southern Sweden, the most significant Moho deepening occurring from the Oslo Region eastwards. Deep seismic studies also suggest that the base of the lithosphere deepens markedly eastwards from the Oslo Region. Such a long-wavelength lithospheric geometry cannot be explained by the Permian or post-Permian evolution of the area, hence the Oslo Graben appears to have evolved at the transition between two lithospheric domains with contrasting thickness. Numerical thermo-mechanical modelling is applied to test if this transitional position can influence the dynamics of rifting. Different models with varying lithosphere thickness contrast are considered. Model results show that a crust and lithosphere thickness contrast comparable to the Oslo Region can explain rifting and focusing of magmatism in a narrow zone with minor thinning of the crust. Models also account for the major characteristics of the Oslo Graben in terms of location and strain distributions in the crust.
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  • 8
    Publication Date: 2007-03-01
    Print ISSN: 0264-8172
    Electronic ISSN: 1873-4073
    Topics: Geosciences
    Published by Elsevier
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  • 9
    Publication Date: 2012-06-01
    Description: Sedimentary basins can be classified according to their structural genesis and evolutionary history and comprise tectonic and sedimentary cycles and stages, to which common elements of petroleum systems and plays may be linked. We describe a new method that allows easier and more efficient comparisons between petroliferous sedimentary basins with similar geologic characteristics. Using this method, we can make predictions of potential petroleum systems and plays occurring in underexplored basins or regions. In this article, the methodology is applied to the well-explored Gabon coastal basin (west African margin) and the conjugate Almada-Camamu Basin (Brazilian margin), which is a frontier basin. The two basins experienced a similar tectonostratigraphic evolution and share many similarities. We propose that petroleum systems and plays identified in the Gabon coastal basin might potentially also be present in the Almada-Camamu Basin. These could include a second lacustrine synrift petroleum system, as well as a fluviomarine transitional petroleum system. Potential, but not yet proven, reservoirs in the Almada-Camamu Basin include coarse sandstones surrounding basement highs within the synrift, synrift lacustrine carbonates, fluviomarine sandstones at the base of the transitional cycle, and early postrift ramp carbonates. The methodology and newly developed figures are particularly useful to obtain a first impression of the tectonostratigraphy, likely petroleum system and play development, and exploration history of potentially analogous basins. Furthermore, the approach allows for the recognition of important differences, raising questions that can be answered by more direct techniques.
    Print ISSN: 0149-1423
    Electronic ISSN: 0149-1423
    Topics: Geosciences
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  • 10
    Publication Date: 2012-05-01
    Description: The Campos Basin is a petroleum-productive, marginal sag basin along the Brazilian margin. It contains a stratigraphic sequence recording lithospheric extension and rift tectonics developing to a fully evolved post-break-up setting. We present a combined approach using subsidence analysis and basin history inversion models to make predictions on source-rock maturation. The classical uniform stretching model does not account for the observed tectonic subsidence, and so we consider the thermal and subsidence implications of incorporating different events of magmatic underplating. The post-rift is characterized by one major phase of post-rift thermal subsidence: changes in sediment supply and load, as well as halokinetic movements, cause deviations from normal thermal subsidence and relaxation. The dimensions of these events have been examined and quantified.Our best-fit forward model is tested against measured borehole temperature (BHT) data. Results show a systematic overestimation of present-day temperatures in the shallow-water wells. Including the effects of hydrothermal convection by raising the conductivity of the top part of the stratigraphic sequence results in an almost perfect fit between predicted and measured BHTs in the shallow-water wells.Based on these forward models, we predict that the lacustrine shales of the syn-rift Lagoa Feia Fm. could be mature to generate oil and/or gas over a larger area than previously expected. Furthermore, our results suggest that the early post-rift Macaé Fm. is locally mature to generate oil, and that the middle/late post-rift Carapebus/Ubatuba Fm. shales are likely to generate oil as well, if organic-rich facies are indeed present. In light of the most recent pre- and post-salt discoveries made near established oil fields in the Campos Basin, our results support the idea that many more such accumulations may be found.
    Print ISSN: 1354-0793
    Topics: Chemistry and Pharmacology , Geosciences
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