image/svg+xml131 V/2/2014 INTERDISCIPLINARIA ARCHAEOLOGICA NATURAL SCIENCES IN ARCHAEOLOGY homepage: http://www.iansa.eu Electric Resistivity Tomography and Magnetic Susceptibility Measurements at the Baden Culture Site Stavenice-Úsov (Czech Republic) Martin Moník a* , Jan Sedláček a a Department of Geology, Faculty of Science, Palacký University in Olomouc, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic 1. Introduction Along with tree logging on the northern slope of an unnamed hill between the villages of Úsov and Stavenice (Olomouc region, Czech Republic) at an altitude of 312 m and coordinates N 49°47ʹ08.89ʺ, E 16°59ʹ31.21ʺ, a rescue excavation took place in 2012 and 2013 (Daňhel 2014; Daňhel in press). This site is located in the southern part of the Hanušovice Highlands at the foot of the Mohelnice Furrow. The bedrock at the site is formed by Culmian greywackes, siltstones and shales (Paleozoic), covered by Quaternary deposits, primarily loessic loam and colluvial sediments (Koverdynský 1996). A number of archaeological features ( i.e. pits, structures, hearths, etc. ; Binford 1964) dating from the Boleráz phase of the Baden Culture of the Middle Eneolithic (Podborský 1993) were unearthed at the site earlier (Daňhel 2014; Daňhel in press). This would date the settlement between 3325 and 3027 cal BC (Horváth et al. 2008). Two earthen, and possibly the wooden ramparts on the northern (N) slope of the hill, fnished with a stone pavement rank among these features. The fortifcation work was also identifed by magnetometry and aerial prospection on the mild south- eastern (SE) slope of the hill (Daňhel 2014), where it had been levelled by Modern Age feld tilling and made partially visible by crop marks. Part of the same fortifcation is in all probability distinguishable as a terracing modifcation on the south-western (SW) slope of the same hill (Figure 1).As the excavations of 2012 and 2013 could not cover the entire area affected by forest clearance, a non-destructive geophysical measurement was carried out in the unexcavated area in June of 2013 and November of 2014 in order to discover additional potential settlement features and verify the spatial continuation of the rampart. Selected settlement strata have been sampled for magnetic susceptibility measurement to confrm or reject their anthropogenic origin and identify potential burned sediments. 2. Methods Out of the range of geophysical methods used in archaeological prospection, geoelectrical methods constitute an important tool for distinguishing archaeological features from original, undisturbed ground. Electric resistivity Volume V ● Issue 2/2014 ● Pages 131–138 *Corresponding author. E-mail: martin.monik@gmail.com ARTICLE INFO Article history: Received: 22. May 2014Accepted: 15. December 2014 Keywords: electric resistivity tomographymagnetic susceptibilityBaden CultureMoraviahillfortEneolithic ABSTRACT Electric resistivity tomography (ERT) is a well-known geophysical method for the identifcation of archaeological features. It was applied at the Middle Eneolithic fortifed site Stavenice-Úsov in Central Moravia (Czech Republic) to reconstruct the shape and structure of a local rampart and, if possible, identify additional settlement features in addition to those revealed by archaeological excavation. Simultaneously, mass magnetic susceptibility (χ mass ) was measured in selected settlement layers and flls in order to distinguish settlement and post-settlement strata and contexts destroyed or otherwise infuenced by fre. The results of ERT measurement indicate that artifcial terrain modifcations took place on the northern, south-eastern and possibly south-western slopes of the hill. Magnetic susceptibility values indicate that the fortifcation, and in all probability also other settlement features, had been destroyed by fre.
image/svg+xmlIANSA 2014 ● V/2 ● 131–138Martin Moník, Jan Sedláček: Electric Resistivity Tomography and Magnetic Susceptibility Measurements at the Baden Culture Site Stavenice-Úsov (Czech Republic) 132 tomography (ERT) is based on the detection of variations in resistivity of rocks and subsurface materials (Kampke 1999). The method is frequently used both in sedimentology for differentiating high-resistivity sands and gravels from low-resistivity loams and clays ( cf. Matys Grygar et al. 2013) and in archaeology ( i.e. Negri, Leucci 2006; Cardarelli, Di Filippo 2009; Tsokas et al. 2009). It is assumed that certain archaeological features, above all stone walls and rubble, behave as resistivity anomalies. If their resistivity values differ from their surroundings, they can be easily detected. It should be mentioned, moreover, that the resistivity values of subsurface soil and colluvial sediments are affected by water saturation (Besson et al. 2004). During dry seasons, soil particles contain a small amount of water and the subsurface layers appear as highly resistive. Measurement by ERT is relatively precise, fast and a wide range of electrode arrangements can be selected from. Reliable results can be expected in particular in shallow subsurface structures. ERT measurement was realized in Stavenice-Úsov using ARES geoelectrical system (GF Instruments, Czech Republic) to discover the shallow subsurface situation on the northern, south-western and south-eastern slopes of the hill. Three ERT sections were carried out, all localized by a GPS device Ashtech Promark 500. Preceding the measurements, a series of electrodes connected with a multi-core cable were introduced into the ground using the Schlumberger array, with the electrodes spaced at 0.5 m. This minimum spacing is necessary to acquire the high resolution of the underlying ground. The northern and south-western sections were made in one day in June of 2013 to minimize the infuence of weather conditions (precipitation) on the differences between single measurements. Although the third, south-eastern section was made in the autumn of 2014, the resistivity values seem to be similar to those from the other two sections. The length of the acquired sections was 35.5 metres in all cases. The maximum depth reached by the measurement, which depends on the length of the section, was approximately 7 metres in the central part of each section. Raw measurement results were processed by the RES2INV software (Geotomo, Malaysia), using the least squares inversion method. One of the aims of this study was to confrm the suitability of ERT method for distinguishing cultural sediments and anthropogenic impact into the bedrock from the underlying, original subsoil. Furthermore,