3D DIGITAL GEOLOGICAL MODELLING OF PALEO-SURFACES. A CASE STUDY FROM THE NATIONAL NUCLEAR WASTE DEPOSITORY SITE IN HUNGARY

The site of the final disposal facility for radioactive waste of the Paks Nuclear Power Plant at Bataapati in Hungary is under intensive geological survey, including paleo-environmental and paleo-surface investigations. The objective of this paper is to present the results of a borehole database analysis and modelling for the pre-Quaternary paleo-surface reconstruction in this important area. Data are heights above sea level of this paleo-surface measured in drill cores. The analysis is based on the assumption that a geological process such as hill slope erosion produces a statistically homogeneous distribution of the measured variable, paleo-surface depth in this case. During spatial trend analysis the obtained six statistically significant paleo-surface depth populations are divided into 13 trend surfaces significant at the 95% confidence level. The model gained by merging the 13 local trend surfaces describe the overall slope conditions. The other surface model is obtained by the accurate linear Triangular Irregular Network (TIN) interpolation capturing all the local details of morphological information. The original 10m grid TIN model is generalised by average smoothing filter with window size increasing from 25m to 1,000m in order to reveal morphological 'trends' at various spatial scales. Analysis of morphological lineaments confirm that major valleys run along regional fault lines, while secondary erosion processes forming the smaller side valleys act at scales below 1km. In this way the pre-Quaternary and younger paleo-valleys can be distingushed from the higher spatial scale tectonic forms. The stationary residuals remaining after trend removal enables detailed surface reconstruction by kriging interpolation.