Introduction

1 The medieval mound of Nids (Tournoisis, Loiret, France) has been the subject of planned archaeological surveys since 2022. This project aims to characterize and date the moated site and its surroundings. It compiles documentary studies on the cadastral morphology with geoarchaeological prospecting (especially field walking, geophysical and geotechnical prospecting).

2 The medieval mound of Nids (Figure 1) is one of the most important at a regional scale (with a platform of 5280m²and 3 to 4 meters in height above the surroundings grounds). In addition, an important part of the associated ditch system is still remaining in the landscape. This mound raises questions regarding the volume of raw material needed for its construction.

3 From an archaeological point of view, the project aims to:

4 Analyse the spatial organization of the mound (lateral and vertical homogeneity, thickness of the stratification)

5 Assess its relationship with the underlying geology

6 Furthermore, this archaeological study is the perfect context to examine the relevance of geophysical typology based on data analysis, data clustering and its interpretation.

7 We will present the results from the 2022 to 2024 campaigns and combine them with the archaeological findings to propose a comprehensive geoarchaeological analysis of the mound.

Figure 1

Medieval mound of Nids and its surroundings looking towards North.

Medieval mound of Nids and its surroundings looking towards North.

Material and methods

Preliminary results

11 The magnetic survey revealed a ditch system and internal features (Figure 2). Several artefacts gathered in the northern area during the field walking survey suggest that the site was already settled during the roman period. They also suggest area with different uses. This spatial distribution of activities could be further refined through geophysical clustering of EMI data. The ERT inversions were done using the PyGIMLI python package (Rücker et al., 2017)

Figure 2

Synthetic map presenting the results of all the geophysical investigations

Synthetic map presenting the results of all the geophysical investigations

Magnetic anomalies, apparent resistivity map and inverted resistivity from the inverted tomographies reported on the horizontal plane.

12 In addition, both DPT and ERT results confirm that the bedrock is located between 2.25 and 6.3 m in depth (Figure 3). This thickness could be associated with archaeological levels. However, mechanical parameters and electrical properties do not associate unequivocally (for example the more resistive anomaly seems to always be related to high Qd values levels which is not the case for less resistive ones).

Work in progress

13 The EMI maps will be processed into three apparent properties maps (Benech et al., 2016). These maps will be analysed with automatic clustering and then compared with the interpretative map proposed by the archaeologist based on the morphology of the anomaly mapped using electrical and magnetic survey together with the walking survey. Seismic velocities tomography (first break and MASW) will be acquired in 2025 to complement the tomography setup.

Figure 3

DPT total length reported over the inverted resistivity model obtained over the top of the mound.

DPT total length reported over the inverted resistivity model obtained over the top of the mound.

14 Excavation are planned for 2025 too which will allow cross analysing with geoarchaeological results. Finally, this cross-referencing of data will enable us to take a closer look at the methodological issues involved in data acquisition and interpretation.