Archaeological and Resources Assessment of Sand and Gravel Deposits Using 3D ERT and Automated Interface Detection

River terrace deposits form one of the major sources for Palaeolithic artefacts and are of economic importance for the groundwater and aggregates industry. Their depositional history and thus structure can be highly complex. We present automated interface detection techniques applied to 3D geoelectrical data in order to guide archaeological prospecting and mining activities. Three different interface detection techniques were applied, which were based on resistivity iso-surfaces defined from clustering techniques and comparison to intrusive investigation, and on the steepest gradient in resistivity depth sections. Their results were compared to intrusive investigations. All three methods successfully imaged an incised channel underlying 3 – 8 m of sand and gravel deposits. The results showed good agreement with bedrock depths obtained from boreholes. The extracted bedrock topography was used to define archaeological trenching locations, within which Palaeolithic artefacts were recovered. The remaining sand and gravel resource of this extraction phase was estimated to be more than 1 350 000 m3.