Direct 14C dating of equine products preserved in archaeological pottery vessels from Botai and Bestamak, Kazakhstan

Direct and accurate radiocarbon dating of lipid residues preserved in ceramics is a recently established method that allows direct dating of specific food products and their inception in human subsistence strategies. The method targets individual fatty acids originating from animal fats such as ruminant dairy, ruminant adipose, non-ruminant adipose and aquatic fats. Horse lipid residues found in Central Asian pottery vessels are also directly dateable using this new method. Here we present the identification of equine lipid residues preserved in two pottery assemblages from the Neolithic and Eneolithic in Kazakhstan and their direct ¹⁴C dating. The site of Botai, previously radiocarbon-dated to the 4th millennium BC, was used as a reference to evaluate the dates obtained directly on horse lipids. The direct dating of equine products extracted from Botai potsherds are shown to be compatible with previous ¹⁴C dates at the site. The site of Bestamak, lacking previous¹⁴C measurements, had been relatively dated to the Neolithic based on pottery typologies. The direct dating of equine residues made it possible to anchor the pottery assemblage of Bestamak in the 6th millennium BC confirming their Neolithic attribution. These findings demonstrate the potential for dating horse products through a compound-specific approach, while highlighting challenges in ¹⁴C dating individual fatty acids from lipid extracts in which their abundances differ substantially.

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The online version contains supplementary material available at 10.1007/s12520-022-01630-2.

Off-line pyrolysis and compound-specific stable carbon isotope analysis of lignin moieties: a new method for determining the fate of lignin residues in soil

Off-line pyrolysis was used to liberate lignin moieties from dung and soil and, after trimethylsilylation, the delta(13)C values of these derivatives were determined by gas chromatography-combustion-isotope ratio mass spectrometry. Initial delta(13)C values determined for 4-vinylphenol, syringol, 4-vinylguaiacol, 4-acetylsyringol, 4-vinylsyringol, 4-(2-Z-propenyl)syringol, 4-(2-E-propenyl)syringol and 4-(2-propenone)syringol pyrolysis products of the lignin polyphenol structure from C(4) (delta(13)C(bulk) = -12.6%) and C(3) (delta(13)C(bulk) = -30.1 per thousand) dung confirmed the robust and reproducible nature of the off-line preparation technique. C(4) dung was used as a treatment in a randomised field experiment to assess the short-term sequestration of dung carbon in managed grasslands. Since lignin was on average 3.5 per thousand depleted in (13)C compared with bulk dung delta(13)C values, this may have resulted in an under-estimation of dung C incorporation based on bulk delta(13)C values. Therefore, an investigation of the compound-specific delta(13)C values of dung-derived lignin moieties extracted from soils sampled up to 372 days was undertaken. Delta(13)C values between lignin moieties extracted from treated and untreated soils showed that dung-derived lignin was not especially resistant to degradation and suggested that individual moieties of the lignin macromolecule must: (i) move into soil, (ii) be degraded, or (iii) be transformed diagenetically at different rates. This adds to a gathering body of evidence that lignin is not particularly stable in soils, which has considerable significance for the perceived role of different biochemical components in the cycling of C in soils.