4 results
An updated and revised stratigraphic framework for the Miocene and earliest Pliocene strata of the Roer Valley Graben and adjacent blocks
- Dirk K. Munsterman, Johan H. ten Veen, Armin Menkovic, Jef Deckers, Nora Witmans, Jasper Verhaegen, Susan J. Kerstholt-Boegehold, Tamara van de Ven, Freek S. Busschers
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- Journal:
- Netherlands Journal of Geosciences / Volume 98 / 2019
- Published online by Cambridge University Press:
- 13 January 2020, e8
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In the Netherlands, the bulk of the Miocene to lowest Pliocene sedimentary succession is currently assigned to a single lithostratigraphical unit, the Breda Formation. Although the formation was introduced over 40 years ago, the definition of its lower and upper boundaries is still problematic. Well-log correlations show that the improved lecto-stratotype for the Breda Formation in well Groote Heide partly overlaps with the additional reference section of the older Veldhoven Formation in the nearby well Broekhuizenvorst. The distinction between the Breda and the overlying Oosterhout Formation, which was mainly based on quantitative differences in glauconite and molluscs, gives rise to ongoing discussion, in particular due to the varying concentrations of glauconitic content that occur within both formations. In addition, the Breda Formation lacks a regional-scale stratigraphic framework which relates its various regionally to locally defined shallow marine to continental members.
In order to resolve these issues, we performed renewed analyses of material from several archived cores. The results of archived and new dinocyst analyses were combined with lithological descriptions and wire-line log correlations of multiple wells, including the wells Groote Heide and Broekhuizenvorst. In this process, the updated dinocyst zonation of Munsterman & Brinkhuis (2004), recalibrated to the Geological Time Scale of Ogg et al. (2016), was used. To establish regionally consistent lithostratigraphic boundaries, additional data was used along a transect across the Roer Valley Graben running from its central part (well St-Michielsgestel-1) towards the southern rift shoulders (well Goirle-1). Along this transect, chronostratigraphic and lithostratigraphic analyses were integrated with well-log correlation and the analyses of seismic reflection data to constrain geometrical/structural relationships as well.
The results led to the differentiation of two distinct seismic sequences distinguished by three recognisable unconformities: the Early Miocene Unconformity (EMU), the Mid-Miocene Unconformity (MMU) and the Late Miocene Unconformity (LMU). The major regional hiatus, referred to as the Mid-Miocene Unconformity, occurs intercalated within the present Breda Formation and compels subdivision of this unit into two formations, viz. the here newly established Groote Heide and the younger Diessen formations. Pending further studies, the former Breda Formation will be temporally raised in rank to the newly established Hilvarenbeek subgroup, which comprises both the Groote Heide and Diessen formations. Whereas these two sequences were already locally defined, a third sequence overlying the LMU represents two newly defined lithostratigraphical units, named the Goirle and the Tilburg members, positioned in this study at the base of the Oosterhout Formation. Besides their unique lithological characteristics, in seismic reflection profiles the Goirle and the Tilburg members stand out because of their distinct seismic facies.
Use of an integrated, multidisciplinary and regional approach, an improved southern North Sea framework and more comprehensive lithostratigraphic subdivision of Neogene successions is proposed for the Netherlands, to make (cross-border) correlations more straightforward in the future.
3D modelling of the shallow subsurface of Zeeland, the Netherlands
- J. Stafleu, D. Maljers, J.L. Gunnink, A. Menkovic, F.S. Busschers
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- Journal:
- Netherlands Journal of Geosciences / Volume 90 / Issue 4 / December 2011
- Published online by Cambridge University Press:
- 24 March 2014, pp. 293-310
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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.
Digital Geological Model (DGM): a 3D raster model of the subsurface of the Netherlands
- J.L. Gunnink, D. Maljers, S.F. van Gessel, A. Menkovic, H.J. Hummelman
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- Journal:
- Netherlands Journal of Geosciences / Volume 92 / Issue 1 / April 2013
- Published online by Cambridge University Press:
- 24 March 2014, pp. 33-46
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A 3D geological raster model has been constructed of the onshore of the Netherlands. The model displays geological units for the upper 500 m in 3D in an internally consistent way. The units are based on the lithostratigraphical classification of the Netherlands. This classification is used to interpret a selection of boreholes from the national subsurface database. Additional geological information regarding faults, the areal extent of each unit and conceptual genetic models have been combined in an automated workflow to interpolate the basal surfaces of each unit on 100 × 100 metre (x,y dimensions) raster cells. The combination of all interpolated basal surfaces results in a 3D Digital Geological Model (DGM) of the subsurface. A measure of uncertainty of each of these surfaces is also given. The automated workflow ensures an easily updatable subsurface model. The outputs are available for end users through www.dinoloket.nl.
Silica sand resources in the Netherlands
- M.J. van der Meulen, W.E. Westerhoff, A. Menkovic, S.H.L.L. Gruijters, C.W. Dubelaar, D. Maljers
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- Journal:
- Netherlands Journal of Geosciences / Volume 88 / Issue 3 / November 2009
- Published online by Cambridge University Press:
- 24 March 2014, pp. 147-160
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Silica sand, (almost) pure quartz sand, is a valuable and scarce mineral resource within the shallow Dutch subsurface. High-grade deposits are exploited in the southeasternmost part of the country, as raw material for the glass, ceramic, chemical and other process industries. Dutch land-use policy requires that scarce mineral resources (including silica sand) are taken into consideration in spatial planning and when preparing for largescale engineering or construction works. For this purpose, and in order to review the long-term possibilities for home production of silica sand, we determined resource potential nationally.
Our approach was (1) to establish the relevant conditions and processes associated with the deposition of the currently exploited sands, (2) identify lithostratigraphic units that are genetically similar or are otherwise known to contain quartz-rich sands, and (3) query the Dutch geological survey's borehole database for potential silica sand occurrences within those units. As we have to rely on non-dedicated data, the latter step was undertaken using a largely qualitative set of lithological search parameters. Finally, a limited number of available chemical analyses was used for preliminary verification purposes.
Using this approach, we identified three prospective areas: one in the north of the province of Limburg and east of the province of Noord-Brabant(~750 km2), one in the central south of Noord-Brabant (~45 km2), and one in the east of the Gelderland and Overijssel provinces (~1,200 km2). For each area, first-order characteristics of possible silica sand resources are presented (type of deposit, depth, approximate thickness). In the terms of current reporting conventions, we resolved silica sand occurrence to the level of ‘reconnaissance mineral resource’ or ‘exploration result’, and our results do not constitute a formal resource declaration. Available chemical data suggest that the resources in the first two areas could be or become economic, although the grades are lower than those of the currently exploited resources. The third area is less promising in that respect, but available data is too limited to reject the area in this stage. Even so, we tentatively conclude that home production of silica sand can probably be maintained after the reserves in Limburg are depleted.