Pretreatment and gaseous radiocarbon dating of 40\u2013100\u2009mg archaeological bone

H Fewlass,E Bard,B Kromer,Y Fagault,T Tuna,S Talamo,J.-J Hublin

doi:10.1038/s41598-019-41557-8

Abstract

Radiocarbon dating archaeological bone typically requires 300–1000 mg material using standard protocols. We report the results of reducing sample size at both the pretreatment and 14C measurement stages for eight archaeological bones spanning the radiocarbon timescale at different levels of preservation. We adapted our standard collagen extraction protocol specifically for <100 mg bone material. Collagen was extracted at least twice (from 37–100 mg material) from each bone. Collagen aliquots containing <100 μg carbon were measured in replicate using the gas ion source of the AixMICADAS. The effect of sample size reduction in the EA-GIS-AMS system was explored by measuring 14C of collagen containing either ca. 30 μg carbon or ca. 90 μg carbon. The gas dates were compared to standard-sized graphite dates extracted from large amounts (500–700 mg) of bone material pretreated with our standard protocol. The results reported here demonstrate that we are able to reproduce accurate radiocarbon dates from <100 mg archaeological bone material back to 40,000 BP.

Highlights

Bone is one of the most frequently radiocarbon-dated materials recovered from archaeological sites
In our preliminary study[29] we demonstrated that the gas ion source of the AixMICADAS30 is suitable for dating bone collagen CO2 samples of
Once we had determined the optimum pretreatment protocol for

Summary

Introduction

Bone is one of the most frequently radiocarbon-dated materials recovered from archaeological sites. 200 μg C from archaeological bones can be successfully produced and measured using the IonPlus Automated Graphitisation Equipment III (AGE 3)[17] and MIni CArbon DAting System (MICADAS)[18,19] developed at ETH Zurich. As sample size is reduced the effect of contamination during pretreatment and measurement increases greatly. The majority of 14C labs follow collagen extraction protocols based on Longin[33]. The addition of an ultrafiltration step, first proposed by Brown, et al.[39] has in particular improved the accuracy of 14C dating of Palaeolithic bones[40]; gelatinised samples are filtered to concentrate large (>30 kDa) molecules to produce a ‘cleaner’ collagen extract.

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