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  • 1
    Electronic Resource
    Electronic Resource
    Pseudo-unconformities in seismic models of large outcrops (1995)
    Springer
    Geologische Rundschau 84 (1995), S. 761-769 
    Details
    ISSN: 0016-7835
    Keywords: Key words: Seismic modeling ; Seismic interpretation ; Sequence-stratigraphy ; Unconformities ; Carbonates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Traditionally, seismic modeling has concentrated on one-dimensional borehole modeling and two-dimensional forward modeling of basic structural–stratigraphic schemes, which are directly compared with real seismic data. Two-dimensional seismic models based on outcrop observations may aid in bridging the gap between the detail of the outcrop and the low resolution of seismic lines. Examples include the Dolomites (North Italy), the Vercors (SE France), and the High Atlas (Morocco). The seismic models are generally constructed using the following procedure: (a) construction of a detailed lithologic model based on direct outcrop observations; (b) division of the lithologic model into lithostratigraphic units; (c) assignment of petrophysical properties to these lithostratigraphic units; (d) ray tracing to compute time- or depth sections of reflectivity; (e) convolution of the reflectivity sections with source wavelets of different frequencies. The lithologic detail modeled in the case studies led to some striking results, particularly the discovery of pseudo-unconformities. Pseudo-unconformities are unconformities in seismics, but correspond to rapid changes of dip and facies in outcrop. None of the outcrop geometries studied were correctly portrayed seismically at 25-Hz peak frequency. However, in some instances the true relationship would gradually emerge at peak frequencies of 50–100 Hz. The examples given in this study demonstrate that detailed, outcrop-derived, seismic models can reveal what stratigraphic relationships and features are likely to be resolved under ideal or less-ideal conditions, and what pitfalls may befall the interpreter of real seismic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240566
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  • 2
    Electronic Resource
    Electronic Resource
    Pseudo-unconformities in seismic models of large outcrops (1995)
    Springer
    International journal of earth sciences 84 (1995), S. 761-769 
    Details
    ISSN: 1437-3262
    Keywords: Seismic modeling ; Seismic interpretation ; Sequence-stratigraphy ; Unconformities ; Carbonates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Traditionally, seismic modeling has concentrated on one-dimensional borehole modeling and two-dimensional forward modeling of basic structural-stratigraphic schemes, which are directly compared with real seismic data. Two-dimensional seismic models based on outcrop observations may aid in bridging the gap between the detail of the outcrop and the low resolution of seismic lines. Examples include the Dolomites (North Italy), the Vercors (SE France), and the High Atlas (Morocco). The seismic models are generally constructed using the following procedure: (a) construction of a detailed lithologic model based on direct outcrop observations; (b) division of the lithologic model into lithostratigraphic units; (c) assignment of petrophysical properties to these lithostratigraphic units; (d) ray tracing to compute time- or depth sections of reflectivity; (e) convolution of the reflectivity sections with source wavelets of different frequencies. The lithologic detail modeled in the case studies led to some striking results, particularly the discovery of pseudo-unconformities. Pseudo-unconformities are unconformities in seismics, but correspond to rapid changes of dip and facies in outcrop. None of the outcrop geometries studied were correctly portrayed seismically at 25-Hz peak frequency. However, in some instances the true relationship would gradually emerge at peak frequencies of 50–100 Hz. The examples given in this study demonstrate that detailed, outcrop-derived, seismic models can reveal what stratigraphic relationships and features are likely to be resolved under ideal or less-ideal conditions, and what pitfalls may befall the interpreter of real seismic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240566
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    Paper (German National Licenses)
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  • 3
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    3D geology in a 2D country: perspectives for geological surveying in the Netherlands (2013)
    Cambridge University Press
    Details
    Publication Date: 2013-12-01
    Description: Over the last ten to twenty years, geological surveys all over the world have been entangled in a process of digitisation. Their paper archives, built over many decades, have largely been replaced by electronic databases. The systematic production of geological map sheets is being replaced by 3D subsurface modelling, the results of which are distributed electronically. In the Netherlands, this transition is both being accelerated and concluded by a new law that will govern management and utilisation of subsurface information. Under this law, the Geological Survey of the Netherlands has been commissioned to build a key register for the subsurface: a single national database for subsurface data and information, which Dutch government bodies are obliged to use when making policies or decisions that pertain to, or can be affected by the subsurface. This requires the Survey to rethink and redesign a substantial part of its operation: from data acquisition and interpretation to delivery. It has also helped shape our view on geological surveying in the future.The key register, which is expected to start becoming operational in 2015, will contain vast quantities of subsurface data, as well as their interpretation into 3D models. The obligatory consultation of the register will raise user expectations of the reliability of all information it contains, and requires a strong focus on confidence issues. Building the necessary systems and meeting quality requirements is our biggest challenge in the upcoming years. The next step change will be towards building 4D models, which represent not only geological conditions in space, but also processes in time such as subsidence, anthropogenic effects, and those associated with global change.
    Print ISSN: 0016-7746
    Electronic ISSN: 1573-9708
    Topics: Geosciences
    Published by Cambridge University Press
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  • 4
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    Advances in constructing regional geological voxel models, illustrated by their application in aggregate resource assessments (2015)
    Cambridge University Press
    Details
    Publication Date: 2015-02-16
    Description: Aggregate resource assessments, derived from three subsequent generations of voxel models, were compared in a qualitative way to illustrate and discuss modelling progress. We compared the models in terms of both methodology and usability. All three models were produced by the Geological Survey of the Netherlands. Aggregate is granular mineral material used in building and construction, and in this case consists of sand and gravel. On each occasion ever-increasing computer power allowed us to model at a higher resolution and use more geological information to constrain interpolations. The two oldest models, built in 2005 and 2007, were created specifically for aggregate resource assessments, the first as proof of concept, the second for an online resource information system. The third model was derived from the ongoing multipurpose systematic 3D modelling programme GeoTOP. We used a study area of 40 × 40 km located in the central Netherlands, which encompasses a section of the Rhine-Meuse delta and adjacent glacial terrains to the north. Aggregate resource assessments rely on the extent to which the occurrence and grain size of sand and gravel are resolved, and on proper representation of clay and peat layers (overburden and intercalations) that affect exploitability. Average model properties (e.g. total aggregate content) are about the same in all three models, except for a difference resulting from converting older lithological classifications to the current one. This difference illustrates that data selection and preparation are paramount, especially when dealing with quality issues. Generally speaking the results of the aggregate resource assessments are consistent and satisfactory for all three models, provided that they are judged at the appropriate scale. However, the assessments based on GeoTOP best approach the desired scale of use for the aggregates industry; in that sense progress was significant and each model was a better fit for the purpose.
    Print ISSN: 0016-7746
    Electronic ISSN: 1573-9708
    Topics: Geosciences
    Published by Cambridge University Press
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  • 5
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    3D modelling of the shallow subsurface of Zeeland, the Netherlands (2011)
    Cambridge University Press
    Details
    Publication Date: 2011-12-01
    Description: The Geological Survey of the Netherlands aims at building a 3D geological voxel model of the upper 30 m of the subsurface of the Netherlands in order to provide a sound basis for subsurface related questions on, amongst others, groundwater extraction and management, land subsidence studies, aggregate resources and infrastructural issues. The Province of Zeeland (SW Netherlands, covering an area of approximately 70 by 75 km) was chosen as the starting point for this model due to an excellent dataset of 23,000 stratigraphically interpreted borehole descriptions.The modelling procedure involved a number of steps. The first step is a geological schematisation of the borehole descriptions into units that have uniform sediment characteristics, using lithostratigraphical, lithofacies and lithological criteria. During the second modelling step, 2D bounding surfaces are constructed. These surfaces represent the top and base of the lithostratigraphical units and are used to place each voxel (100 by 100 by 0.5 metres) in the model within the correct lithostratigraphical unit. The lithological units in the borehole descriptions are used to perform a final 3D stochastic interpolation of lithofacies, lithology (clay, sand, peat) and if applicable, sand grain-size class within each lithostratigraphical unit. After this step, a three-dimensional geological model is obtained. The use of stochastic techniques such as Sequential Gaussian Simulation and Sequential Indicator Simulation, allowed us to compute probabilities for lithostratigraphy, lithofacies and lithology for each voxel, providing a measure of model uncertainty.The procedures described above resulted in the first fully 3D regional-scale lithofacies model of the shallow subsurface in the Netherlands. The model provides important new insights on spatial connectivity of sediment units of, for example, sandy Holocene tidal channel systems. Our results represent a major step forward towards a fully 3D voxel model of the Netherlands.
    Print ISSN: 0016-7746
    Electronic ISSN: 1573-9708
    Topics: Geosciences
    Published by Cambridge University Press
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  • 6
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    Pseudo-unconformities in seismic models of large outcrops (1995)
    Springer
    Details
    Publication Date: 1995-01-01
    Print ISSN: 0016-7835
    Electronic ISSN: 1432-1149
    Topics: Geosciences
    Published by Springer
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  • 7
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    Pseudo-unconformities in seismic models of large outcrops (1995)
    Springer
    Details
    Publication Date: 1995-12-01
    Print ISSN: 0016-7835
    Electronic ISSN: 1432-1149
    Topics: Geosciences
    Published by Springer
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  • 8
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    Three-dimensional distribution of organic matter in coastal-deltaic peat: Implications for subsidence and carbon dioxide emissions by human-induced peat oxidation (2018)
    Elsevier
    Details
    Publication Date: 2018-06-01
    Print ISSN: 2213-3054
    Topics: Geography
    Published by Elsevier
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