Yates, AB 2015, 'Radiocarbon dating residues from stone tools', PhD thesis, Southern Cross University, Lismore, NSW.
Copyright AB Yates 2015
This dissertation focuses on the development of radiocarbon dating residues from stone artefacts. In the study, the method’s application is examined on artefact samples from archaeological assemblages. While radiocarbon dating of blood residues had been previously reported, dating accuracy required further substantiation. Compromising effects had been described, however the real impact of contamination during sampling steps and analysis protocols remained unclear. Certainly minimizing the quantity of extraneous carbon introduced into samples becomes increasingly significant with small-mass samples.
This study has four consecutive aims: (i) to test the practicability of radiocarbon dating plant residues by investigating the impact of contaminant introduction during sample preparation, (ii) to examine contaminants inherent on stone tools and their removal strategies, (iii) to test the feasibility of the method by dating residues from archaeological stone tools with a reference age and (iv) to develop adequate strategies for contaminant prevention to meet future residue dating requirements.
Methods used for this study comprised of microscopic residue and use wear analyses, including Scanning Electron Microscope Energy Dispersive X-ray (SEM-EDX) observations. Experimental studies evaluated contaminant cleaning from stone tools and residue extraction methods. Samples were radiocarbon dated using Accelerator Mass Spectrometry (AMS). Replicated stone tools were used initially to test techniques. Subsequently, selected artefacts from three archaeological sites were analyzed.
Results of this research show significant steps forward in direct residue radiocarbon dating.
The feasibility of radiocarbon dating ultra-small samples is suggested if contaminants are confined. For instance, the smallest sample of 10.5 μgC – extracted wooden residues from iv replicate chert flakes – was dated in agreement with the reference age of ~ 6000 cal BP. Residues dated from an archaeological context showed promising results while emphasizing the crucial impact of contamination for age offsets. Two adhesive residues from one stone tool, which yielded 33.30 μgC and 44.38 μgC, were dated within the expected Late Holocene time frame. Wooden residues from a Mesolithic stone tool, containing 18.97 μgC, were dated successfully, and although deviating ~ 1000 years from the stratigraphical age measurement, the date may still represent the authentic age if taphonomic processes caused tool movement. For the first time it has been shown that the measurement of residues with such small carbon masses yielded dates in or near agreement to the reference age. This is particularly remarkable when considering the archaeological artefacts initially contained multiple contaminants.
Several limitations were overcome by the development of specific sampling and analytical protocols. This will limit common contamination and facilitate accurate artefact residue radiocarbon dating.