Non-invasive chemical characterisation of archaeological ochres from the early 4th millennium BCE forager graves and settlements in Finland

• The use of non-invasive ED-XRF to chemically group archaeological ochres from eight 4th millennium BCE sites in Finland. • Three primary chemical ochre groups were discovered at the sites, which potentially represent regional ochre sources. • The group division suggests that ochres were part of a long-distance exchange or gift-giving network. • The deliberate use of different ochre types indicates their role in ritualized practices. In the early 4th millennium BCE, the region of modern-day Finland was inhabited by pottery-using foragers, the Typical Comb Ware culture (TCW) people, who lived in village-like clusters of semi-subterranean houses and buried their dead in ochre-coloured graves. Here, we report the results of the analyses of archaeological ochre samples from burial and domestic contexts at eight TCW sites across Finland using non-invasive energy-dispersive X-ray fluorescence (ED-XRF) and scanning electron microscopy with energy dispersive spectrometry (SEM-EDS). Our comparative characterisation of the archaeological ochres aimed to distinguish whether 1) a signature ochre composition per site/community could be chemically discriminated; 2) similar ochre chemical fingerprints are detected in both burial and domestic settings in specific regional contexts; 3) the chemical data indicates shared ochre procurement strategies or ochre exchange among the studied communities or regions; and 4) how ochre was used as part of TCW mortuary practices. Based on our study, non-invasive ED-XRF of archaeological ochre samples enables the characterisation of a limited set of elemental concentrations; however, statistical analysis of log 10 Fe-normalised concentration values allowed us to identify compositional groups in our dataset that correlate with the site location clusters or specific archaeological or geological phenomena. Hence, we propose that this result indicates regionalised ochre procurement and, in some cases, inter-regional, two-way transport of ochre, which may have specific, cross-regionally desired characteristics. Simultaneously, our results also highlight the deliberate use of different types of ochre within ritualized practices.