Effective combination of microgravimetry and geoelectrical methods in the detection of subsurface cavities in archaeological prospection – selected case-studies from Slovakia

Abstract

This contribution is focused on a common utilization of microgravimetry (very precise and detailed gravimetry) and geoeletrical methods (ground penetrating radar and electric resistivity tomography) in the detection of subsurface cavities in non-destructive archaeological prospection. Both methods can separately detect such kind of subsurface objects, but their complementary and at the same time an eliminating aspect can be very helpful in the interpretation of archaeogeophysical datasets. These properties were shown in various published case-studies. Here we present some more typical examples. Beside this, we present here for a first time an application of the electric resistivity tomography in the interior of a building (a church) in Slovakia. We also demonstrate an example with an extremely small acquisition step in microgravity as a trial for the detection of cavities with very small dimensions -in this case small separated spaces for coffins as a part of the detected crypt (so called columbarium). Unfortunately, these cavities were too small to be reliably detected by the microgravity method. We have tried the well-known 3D Euler deconvolution method to obtain usable depth estimates from the acquired anomalous gravity field. Results from this method were in the majority of cases plausible (sometimes little bit too shallow), when compared with the results from the ground penetrating radar.In one selected example, the 3D Euler solutions were too deep and in the present stage of study we cannot well explain this situation. In general, all presented results support an important role of common combination of several geophysical methods, when searching for subsurface cavities in non-destructive archaeological prospection.

Experiences from microgravity and GPR surveys for subsurface cavities detection – case studies from SW- and central Slovakia

“…In the St. Joseph's church the GPR method has found a central crypt in the presbytery (in a form of so-called columbarium -Fig. 3a), which was the first case in Slovakia that the small spaces for coffins could be recognized in horizontal GPR sections (Pašteka et al 2019). Microgravimetry method could confirmed only the total effect of this crypt (Fig.…”

“…Very effective is a joint use of these two methods, as it has been shown in many studies (e.g. Pánisová et al 2013;Pašteka et al 2019). Here we present results from several surveys, performed in medieval churches in SW-and central Slovakia.…”

Zaniknuté stavby v areáli farského kostola vo Svätom Jure : (výsledky geofyzikálneho a archívneho výskumu)

“…Kombinácia týchto dvoch metód sa používa najmä na detekciu podzemných prázdnych priestorov, ako sú väčšie hrobky a krypty (napr. Pašteka et al 2019). Obidve použité geofyzikálne metódy boli realizované v lokálnom súradnicovom systéme, ktorý bol následne zameraný pomocou GNSS prístroja Trimble R8S v globálnom súradnicovom systéme JTSK-03.…”

Microgravity method in archaeological prospection: methodical comments on selected case studies from crypt and tomb detection

“…In comparison with the GPR method, microgravimetry is much more time-consuming, but less dependent on the influence of various artificial sources (such as electric cable networks, iron meshes in concrete layers, metallic covers of shafts, etc.). There exist many successful applications of the combination of the GPR and microgravity methods in crypt discovery (Panisova et al, 2012(Panisova et al, , 2013(Panisova et al, , 2016Pašteka et al, 2007Pašteka et al, , 2019and others).…”