AEM Combined with TDEM - A Good Tool for Mapping the Quaternary in Rugged Areas

Overdeepend alpine valleys are main players in alpine geology, and therefore the main operational theatre for applied geophysicst in Austria. One of the main geological questions to be tackled is the presence and/or size of hydrogeological regimes, mostly harboured in quaternary units. The combination of Air-borne electromagnetics (AEM) and transient-electromagnetics (TDEM) proofed successful as assistance for geological mapping activities in rugged, alpine areas. Hereby the TDEM method is applied to collect deeper information than provides by air-borne systems. The starting models for TDEM inversions are constraint by multi-electrode geoelectric profiles. However, strong anthropogenic noise in alpine valleys reduces the success rate of TDEM surveys to 70%. One case study is presented, showing the thinning out of a clay rich bottom set underneath a glacial terrace.