KEY WORDS: 3D geological model, London

This paper will describe firstly the combined cognitive and geostatistical modelling methodology that was developed in order to produce a structural model of the Chalk under London and secondly how the resultant model has improved our understanding of how the London Basin evolved during the Cretaceous period. A major difficultly in elucidating the structure of the Chalk in the London Basin is that the Chalk is largely unexposed. By using a combined cognitive and geostatistical approach, the resultant 3D model for the London Basin was more consistent with current geological observations and understanding. In essence, the methodology proposed here decreased the disparity between the digital geological model and the geological reality. Previously, the geological structure of the London Basin was thought to be ‘relatively ’ simple, being dominated by a broad north-east trending syncline. However, 3D modelling suggests that, in detail, the London Basin is a far more complex structure, being a collection of at least 5 fault-bounded basins. The model also indicates that the structural style of the basin changes moving north to south. This corresponds to the boundary between two structural provinces observed within the basement strata in the region (London Platform, part of the Midlands Microcraton in the north and the Variscan fold-thrust belt in the south)