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Integrating multi-receiver electromagnetic induction measurements into the interpretation of the soil landscape around the school of gladiators at Carnuntum



Recently, the unique foundations of a school of gladiators were discovered in the Roman town of Carnuntum (40 km southeast of Vienna, Austria) by applying a combination of non-invasive archaeological prospection techniques such as magnetometry, ground penetrating radar, aerial photography, airborne laser scanning and airborne imaging spectroscopy. Although the well-preserved remains of the building complex were revealed down to a depth of 1.8 m by high-resolution near-surface geophysics, some questions about the surrounding soil landscape remained unanswered. Therefore, a proximal soil sensing procedure based on a survey with a multi-receiver electromagnetic induction (EMI) instrument was conducted to interpret the surroundings of the school, covering an area of 5.6 ha. We investigated the usefulness of integrating the complementary apparent electrical conductivity (ECa) and apparent magnetic susceptibility (MSa) measurements for the mapping and investigation of this soil landscape. The multiple ECa measurements allowed the identification of zones with low-conductive gravel outcrops, and zones where silty-clayey soils were deposited on top of the underlying gravel. An EC-depth slicing procedure enhanced the contrast between small soil features, such as frost-wedge pseudomorphs and drainage gullies, and their background, and provided indications about the depth extent of these features. The MS-depth slices showed the foundations of the school of gladiators, an aqueduct and grave monuments. After combining these results with the topography, an integrated visualization of the school in its soil landscape was obtained. This study demonstrated the potential of multi-receiver EMI soil surveys to map and interpret the soil landscape and to discern small natural as well as archaeological features.