Three-dimensional voxel geological model of a riparian lowland and surrounding catchment using a multi-geophysical approach

The distribution and volume of organic sediments as well as the flow pathways in riparian lowlands are important parameters when determining the potential denitrification capacities of a catchment. A headwater catchment in Denmark was investigated with a range of geoelectrical and electromagnetic geophysics as well as shallow boreholes to create a geological model of a riparian lowland. The organic sediments showed a high resistivity variation when measured resistivities were compared with borehole lithology. Chemical analyses of soil and groundwater samples were used to explain the resistivity variation. Resistivity was observed to correlate well with pore water salinity entailing that ionic input into the riparian aquifer was of considerable importance to the resistivity of peat sediments as well as the interpretation of geological boundaries. Based on the analyses of resistivity variations a set of geological surfaces were interpreted on 86 sections. The surfaces were interpolated using ordinary kriging and compiled into a structured three-dimensional grid with uniformly sized voxels measuring 10 x 6 x 0.5 m (x, y, z directions). The resulting model may be used for evaluating the volume and distribution of peat and as a geological basis for hydrobiogeochemical modelling. (C) 2020 Elsevier B.V. All rights reserved.