Geophysical survey at the early Christian complex of Son Peretó (Mallorca, Balearic Islands, Spain)

Abstract

Rural basilicas are the most important evidence of Christianization of the countryside on the island of Mallorca (Balearic Islands, Spain). Recent investigations of rural landscape transformations suggest that some churches were built along communication routes and linked to preexisting settlements. To obtain new data that could support this hypothesis, a geophysical survey has been carried out at the early Christian complex of Son Peretó, one of the most emblematic sites for the understanding of Late Antiquity on the island. The objective was to better define the site investigating the possible presence of other remains related to the Christian complex, that is undergoing excavation, or to a previous settlement that was later Christianized. The geophysical survey was carried out combining magnetometry and ground-penetrating radar.For the magnetic investigation, a multiprobe gradiometer array was used. GPR was used to examine the areas nearby the remains already excavated and to better define areas where the magnetic data revealed interesting anomalies. GPR data were collected using an IDS GPR system. The results revealed both the presence of architectural remains beneath the soil that help define the Early Christian complex, as well as other remains that suggest the church was part of a larger settlement.

Comprehensive geophysical prospection of the Roman and late antique city of Pollentia (Alcúdia, Mallorca, Spain)

“…The heating of the material results in a strong thermoremanent magnetization, expressing dipole anomalies of high intensity. The here applied interpretation scheme corresponds well with the results of magnetic prospection at late antique rural sites of Mallorca, where similar features were found (Mas Florit et al, 2018, 2021). Of course, especially in the context of an ancient city complex, the recognition of individual structures is made difficult by manifold overlays of different settlement phases.…”

“…These differences are relevant in an archaeological context that lays at variable depths and conservation degrees depending on the zones, and especially in clayey soils, altered by centuries of cultivation. As shown in recent experiences, the sites are like the sites of Son Peretó (Mas Florit et al, 2021) or Firella in terms of geological and archaeological contexts, and produce in GPR a high contrast of reflection of the building remains or limestone bedrock rises, but at the same time tend to rapid attenuation of pulses, reducing the effective penetration ranges between 1.1 m and 1.4 m in dry conditions (Davis & Annan, 1989). In the case of Pollentia , the datasets show these characteristics, but also an added problem posed by the different ground surface conditions, from flat grass cover to rugged terrains with higher vegetation, compacted clay, or cultivation fields.…”

“…Secondly, the GPR data processing and time‐slice sequence generation also presented problems with contrast parameters. The clayey soils of the site tend to rapidly attenuate the GPR pulses with depth (Mas Florit et al, 2021; Verdonck, 2012), allowing penetrations that barely exceeded 1.2 m. At the same time, the local limestone ( marès ) produced strong reflections in the clayey media. In this context, one can expect a good definition of the building remains, mainly made of limestone, for a certain depth, but the results do not exactly match this assumption.…”

Contributions of ground‐penetrating radar in research of some predynastic and dynastic archaeological sites at the eastern and western banks of the River Nile, Assiut, Egypt

“…Geophysical methods in archaeological investigations provide large‐scale survey data that can explore and map the buried structures of extensive and complex sites (Florit et al, 2021). Geophysical prospection with it's expanding on archaeological research; specialists continue to make important advances in data collection (Conyers & Leckebusch, 2010).…”