Causes of uncertainties in geomodelling inputs: data review of Paleozoic geology of the Euregion Meuse-Rhine

Geological models are needed for subsurface engineering purposes, and it is crucial to identify their uncertainties. However, uncertainties in their input are easily overlooked. Through a data review of Paleozoic geology in the Eurogion Meuse-Rhine, sources of uncertainty were identified in geomodelling input. Causes of uncertainty were classified into four groups: (a) stratigraphic interpretation, (b) fault interpretation, (c) transferring data, and (d) uncertainty in legacy materials. The causes of uncertainty are interlinked, causing the uncertainty chain in geomodelling to be more complex than generally considered. 

The Paleozoic geology in the study region is structurally complex and geomodelling is hampered by limited outcrops and scattered input data. This study compiles geomodelling input and examines data inconsistencies. We collected legacy literature and maps, conducted fieldwork, and compiled a dataset of 738 boreholes. New borehole data are included, and two legacy boreholes (Kastanjelaan-2 and RWTH-1) were re-evaluated. Differences are observed between various stratigraphic profiles for these two boreholes among different sources. Here, we propose updated stratigraphic interpretations for them. Comparing a newly drilled borehole with an existing geological cross-section reveals a >1 km depth mismatch between stratigraphic units. Comparing the stratigraphy of the borehole dataset with different geologic maps shows various degrees of agreement. The identified inconsistencies demonstrate the necessity of validating input data before embarking on any geomodelling exercise.