Best practices for calibrating and reporting stable isotope measurements in archaeology

Before amalgamating published isotope data, comparability should be demonstrated. This paper compares carbon and oxygen isotopic compositions of 30 enamel samples measured by two laboratories. The aims were to see what, if any, isotopic variation was observed, to determine the causes as needed and to correct if possible. Bioapatite was acidified at 90°C in 2006 and at 26°C in 2017, while δ values were corrected via one‐point normalization in 2006 and by two‐point normalization in 2017. One case (of the 30) produced different δ values between the analysis dates, suggesting contamination. Repeated carbon isotope ratio measurements were not meaningfully different. Repeated oxygen isotope ratio measurements were significantly different, even following correction for acid‐carbonate fractionation at different temperatures and the renormalization of 2017 δ values using one point; however, differences were not meaningful for interpretations. Results were used to calculate real interpretative differences (RIDs) for comparing enamel bioapatite as 0.6‰ for δ13C values and as 1.6‰ for δ18O values.

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“…Some guidelines on reporting isotope data are available for archaeology (Szpak et al . ; Roberts et al . ) and forensics (Dunn et al .…”

Section: Discussionmentioning

confidence: 99%

Addressing data comparability in the creation of combined data sets of bioapatite carbon and oxygen isotopic compositions

et al. 2019

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“…Standard uncertainty was determined to be ±0.15‰ for δ 13 C and ±0.3‰ for δ 15 N as calculated by the method presented by Szpak et al . () (additional details are provided in the Supplementary Methods).…”

Section: Methodsmentioning

confidence: 99%

Stable Isotope Sourcing of Wool from Textiles at Pacatnamú

et al. 2018

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Stable carbon and nitrogen isotopic compositions were determined for wool textiles from the Lambayeque (c. AD 1100-1320) occupation at Pacatnamú in the Jequetepeque Valley, northern Peru. The isotopic data demonstrate that the wool was not obtained via long-distance exchange with the highlands and was most probably derived from locally raised camelids. In light of other lines of evidence (diversity of dyes used to produce the same colours in textiles and the low quality of the weaving), textiles at Pacatnamú appear not to have been as effective a marker of political power and prestige for local elites as they were elsewhere in the Andean region.

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“…Carbon and nitrogen isotopic compositions were calibrated relative to VPDB (Vienna Pee Dee Belemnite) and AIR (atmospheric nitrogen), respectively, using a two‐point calibration anchored by USGS40 and USGS41. Analytical uncertainty was determined to be ± 0.26 for δ 13 C and ± 0.29 for δ 15 N (Szpak et al, ); additional details on analytical accuracy and precision are provided in the supplementary material.…”

Section: Methodsmentioning

confidence: 99%

Effects of Sodium Hydroxide Treatment and Ultrafiltration on the Removal of Humic Contaminants from Archaeological Bone

Szpak

Krippner

Richards

2017

Intl J of Osteoarchaeology

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This study compared bone collagen extraction techniques that included treatment with sodium hydroxide and 30 kDa ultrafilters using a set of well-preserved, humic-contaminated archaeological marine mammal bones. Treatment with sodium hydroxide was effective at removing humic contaminants from archaeological bone, although yields were significantly decreased. Yields were also significantly decreased by ultrafiltration although this study produced no evidence that 30 kDa ultrafilters were effective at selectively removing humic contaminants from archaeological bone. The combination of sodium hydroxide treatment and ultrafiltration did not produce superior results to the treatment involving only sodium hydroxide. Archaeological samples exhibiting darker colouration indicative of humic contamination should be treated with sodium hydroxide to remove these contaminants.

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Best practices for calibrating and reporting stable isotope measurements in archaeology

Cited by 161 publications

References 25 publications

Addressing data comparability in the creation of combined data sets of bioapatite carbon and oxygen isotopic compositions

Addressing data comparability in the creation of combined data sets of bioapatite carbon and oxygen isotopic compositions

Stable Isotope Sourcing of Wool from Textiles at Pacatnamú

Effects of Sodium Hydroxide Treatment and Ultrafiltration on the Removal of Humic Contaminants from Archaeological Bone

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