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

Abstract

Geological models are important for subsurface engineering and it is crucial to identify their uncertainties. However, uncertainties in their geological input can be elusive and easily overlooked. Through a data review of Paleozoic geology of the Euregion-Meuse-Rhine, uncertainties in geomodelling inputs are identified and their causes are categorised into four groups: (1) stratigraphic interpretation, (2) fault interpretation, (3) transferring data, and (4) uncertainty in legacy materials. Examining these uncertainties reveals numerous sources for them that are intertwined. The number of connected sources of uncertainty demonstrate that the uncertainty chain in geomodelling is complex, calling for further investigation into the magnitude of the identified uncertainties.

The Paleozoic geology in the study region has structural complexity in which geomodelling is hampered by limited outcrops and scattered input data. We compile input and examine data inconsistencies by collecting legacy literature and maps, conducting fieldwork, and compiling a dataset of 738 boreholes. Stratigraphic profiles of new boreholes (Cottessen-01, Banholt-01, and Terziet-02) are also included and two boreholes (Kastanjelaan-02 and RWTH-01) are re-evaluated with additional palynological constraints. Differences are found between various stratigraphic profiles for the latter two boreholes among different sources and updated stratigraphic profiles are presented for them. Comparing a newly drilled borehole with an existing geological cross-section reveals a >1 km depth mismatch between stratigraphic stages. Comparing stratigraphy of the borehole dataset with different geological maps reveals various degrees of agreement. The identified inconsistencies demonstrate the necessity of validating input data before embarking on any geomodelling exercise.