Session #105: Archaeological Soils and the Detection of Past Practices:
pXRF and the Chemistry of Choma-facts
This session stems from the ongoing dialogue on the guidelines for the analysis of archaeological soils promoted by the Global pXRF Network (GopXRF), and explores the potential of geochemical approaches to extend material culture studies into the soil, the most common material element of any archaeological site. Recent advances in field-based soil chemistry, particularly through portable X-ray fluorescence (pXRF), have demonstrated the presence of culturally constructed landscape-scale artefacts, defined as Choma-facts (from the Greek word χώμα=soil). Like other ecofacts, choma-facts are the enduring residues of past practice that can be detected by soil analyses, and pXRF is one of the most powerful tools available to archaeologists to undertake soil analyses during field research.
Central to the use of pXRF for soil studies is interdisciplinarity: pXRF studies, though rooted in geochemistry, integrate geology, environmental science, bio and landscape archaeology, and material culture studies, as their interpretive power lies not in chemical data alone but in correlations within multi-faceted datasets.The session welcomes contributions presenting case studies and successful methodological applications in the use of pXRF on-site, particularly for understanding the use of space through the identification and interpretation of choma-facts at different scales and contexts (i.e. from the household to landscapes and including construction, production and consumption contexts). These approaches are rooted in an acknowledgement of the potency of space and the challenges around its investigation.
Ultimately, this session invites approaches to how we can understand the spatial dynamics of cultural practice and in turn reflect on materiality and agency. If agency is enacted through the interweaving of time, space, materials, and memory, then pXRF offers a direct, and under-used, method to study the spatial dimension of practice at multiple scales and contexts.
Session organisers:
Doonan, Roger (AtkinsRealis)
Dallai, Luisa (University of Siena)
Schauer, Michaela (University of Vienna)
Rix, Keelie (Universitat Pompeu Fabra Barcelona)
Sharp, Kayeleigh (Northern Arizona University)
Discussant:
Save, Sabrina (Amélie SARL/Terrascope)
Submit your abstract via the conference website: https://www.e-a-a.org/eaa2026 before February 5th 2026
