Directorate Natural Environment
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Marine Geology
OD Nature studies all aspects of the seabed and we are constantly searching for ways to better integrate geology in our models. This is becoming all the more important with the growing demand for major interventions in the marine ecosystem. We need good estimates of the quantity and quality of sand stocks at depth as well as of any changes that may be taking place on the seabed. Major extraction or other works can bring local changes to the geological subsoil. This then has a direct impact on sediment transport and an indirect impact on fauna and flora.
Many seabed measurements and observations, as described in Sediment Transport, are also used in producing digital maps that represent the nature and structure of seabed sediments and deeper in the subsoil. This data can now be retrieved in a flexible manner, in response to investigation into average grain size, type of sediment or any grain size percentile, for example.
To complete and refine this mapping of seabed sediments, geophysical measurements are also carried out, preferably high resolution multibeam data as collected from on board the RV Belgica. This acoustic technique provides depth information from the seabed as well as information on the strength with which the acoustic signal is reflected from the seabed. A strength that corresponds to the hardness of the seabed and therefore indirectly to the sediment nature, but that also tells us something about the action of organisms in the seabed.
For the deeper subsoil, OD Nature collects geological data from core samples of the seabed. This data is converted into European standards to permit a more systematic modelling of the subsoil across borders.
Within a European partnership (EMODnet-Geology), OD Nature produces sediment and geological maps on the scale of the European seas. Together with the Netherlands, Germany, Denmark and the United Kingdom, the southern North Sea is mapped in detail.
The standardised data on seabed sediments and on deeper geological layers is modelled in voxels or 3D blocks of information. The x, y, and z dimensions are determined on the basis of the desired resolution for the area (for example, 250 x 250 x 1 m). In addition to the sediment characteristics per voxel, uncertainties are calculated on the basis of the age of the data or methods of sampling and analysis. Estimating these uncertainties is important in determining “real” changes to the seabed that are greater than the measurement background noise.
Once these three dimensions of the subsoil are modelled the information can be queried in a flexible way. It is easy to calculate desired volumes of raw material quantities and qualities. To determ the environmental impact of major extraction activities, we use the geology in our sediment transport models. Therfore, we can advise to extract only where sufficient resource of a similar quality is available. This is important to prevent major changes in the habitat. In the future, it will be possible to forecast such changes based on the extent that sediment characteristics are altered.
- -Dynamic models of changed sediment composition for major works such as intensive sand extraction and port enlargements.
- -Online, flexible requesting and visualising of geological and geophysical data (in cooperation with BMDC team and BEDIC).
- -Rendering operational requests for sediment characteristics for the purposes of habitat forecasting (in cooperation with MARECO team).
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