A02_P05

Freshwater reservoir effects in charred ‘food crusts’ on pottery: frequency, magnitude, risk factors and prospects for correction

Meadows J^1,2, Lucquin A³, Gonzalez Carretero L^3,4, Dolbunova K^4,5, Craig O³, Heron C⁵

¹ZBSA (Centre for Baltic and Scandinavian Archaeology), Kiel, Germany, ²Christian-Albrechts-Universität zu Kiel, Leibniz-Labor für Altersbestimmung und Isotopenforschung , Kiel, Germany, ³BioArCh, University of York, York, United Kingdom, ⁴Department of Scientific Research, The British Museum, London, United Kingdom, ⁵State Hermitage Museum, St Petersburg, Russia

The ERC-funded INDUCE project is concerned with the adoption of pottery by hunter-gatherer-fishers in northeastern Europe. In this region and period, it is often difficult to date pottery find contexts, but potsherds often have carbonised deposits (‘food crusts’, FCs). Thus ¹⁴C dating of FCs is desirable, but these FCs probably contain carbon from aquatic organisms with unknown ¹⁴C reservoir effects. The problem is more salient at inland sites, given the potential scale of freshwater reservoir effects (FREs).

To investigate pottery function, INDUCE has acquired EA-IRMS data (%C, %N, δ¹³C, δ¹⁵N) on FCs on more than 400 sherds, from over 50 sites. In most cases we have also obtained biomarker (GC-MS) and compound-specific δ¹³C (δ¹³C16:0, δ¹³C18:0) data on soluble lipids extracted from the same FC. Some FCs have also been examined by SEM-EDX microscopy. These analyses confirm that FCs are composed primarily of food remains, which are dominated by aquatic species.

We have dated more than 100 FCs, often when their context date, and/or local FRE, is well-constrained. We have tested whether any combination of isotopic, biomolecular and microscopic data predicts apparent ¹⁴C age offsets in FCs. Contrasting results from sites with >10 dated FCs illustrate the scope for using FC ¹⁴C to date hunter-gatherer-fisher pottery. Where FC ingredients are more varied, a multi-proxy approach appears to account for most of the variation in FC offsets, but at other sites, FC composition is too uniform, and FREs are too varied, to justify attempts at FC ¹⁴C-age ‘correction’.