NEW GEOLOGICAL INSIGHTS FROM STOCHASTIC 3D VOXEL MODELS

TNO - Geological Survey of the Netherlands produces nation wide 3D voxel models up to a depth of 50m below the land surface. The models are integrations of several hundred thousands of database stored borehole descriptions with existing geological mapping and geological expertise. They contain estimates of stratigraphy, lithology (clay, sand, peat) and, where applicable, sand-grain size class data at voxel-resolutions up-to 100*100*0.5m.

Besides serving as a source of subsurface information for the applied geosciences, the models also give new insights in the geological development of the Netherlands throughout the Quaternary. The combination of large amounts of borehole data and the use of powerful new visualisation software (INSIGHT GmbH Subsurface Viewer) reveals new geological patterns that were not known from (classic) geological studies. An example of this is the distribution of peats below the Saalian (Illinoian) glacial till in the northern Netherlands. Borehole data and transects from earlier geological studies already indicated the presence of peat below the till. The 3D distribution of peat in our NL3D voxel model however revealed that the peat occurs in a narrow SE-NW oriented zone. This remarkable spatial distribution suggests that the peats represent the infill of a large incised palaeovalley of the Rhine River that flowed in the area just before progradation of the Saalian ice-sheet into the Netherlands.

It is important to note that these findings ‘emerged’ from the models without direct geological steering. This shows that 3D voxel models like those produced at TNO - Geological Survey of the Netherlands, are valuable sources for obtaining new geological insights in the future.