RUI: Evaluating the Limits and Capabilities of Plasma Chemical Oxidation for Accelerator Mass Spectrometry

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Knowing the age of ancient artifacts helps archaeologists better place human activities into absolute time frames. Radiocarbon dating is one of the most important developments in archaeology from the 20th century, making it possible to directly date materials from the past. However, many artifacts are too small or fragile to survive the standard methods for preparing samples for radiocarbon dating. Dr. Ruth Ann Armitage, of Eastern Michigan University, and her team of collaborating archaeologists and students will evaluate the use of plasma chemical oxidation (PCO) for preparing samples of small, fragmentary or fragile artifacts for radiocarbon dating by accelerator mass spectrometry (AMS). The focus of the project is dating endangered rock art, burned bone, and fragments shed from fragile textiles that would otherwise be difficult or impossible to radiocarbon date directly. PCO has been used for decades as a way to extract organic carbon from inorganic carbon matrices to date rock paintings. It is also a way to date fragile organic materials without destroying them, allowing for repeated dating of the same sample. However, much remains to be learned about the capabilities and limitations of the PCO technique. Validation of the PCO method is critical to applying it in a meaningful way to answer questions about the age of artifacts that might otherwise be overlooked. The Armitage group has a long track record of collaborative work between chemists and archaeologists to better understand past human society and behavior through radiocarbon dating and chemical analysis of artifacts. This project will develop a method for handling, processing and radiocarbon dating archaeological samples that could not be dated otherwise, adding to what is known about people and their activities in the past. The award supports a diverse group of scientists and students at a predominantly undergraduate institution (PUI) doing novel, anthropologically-relevant archaeology research in collaboration with archaeologists.Dr. Armitage and her team seek to demonstrate the accuracy, precision and minimum sample size that can be AMS dated with PCO sample preparation through comparative studies of rock painting samples, calcined bones, and textile fragments. Their work will aid in understanding the effects of chemical pretreatments on samples dated in this way, as well as improving the method so that it can become more widely applicable. The proposed project will investigate the fundamental limitations of the PCO method in order to optimize its use for otherwise difficult to date archaeological materials. The project examines minimally-destructive and rapid methods for reliably dating these types of samples with AMS radiocarbon analysis. Successful completion of the proposal's objectives will improve the ability to date archeological materials. The team seeks to validate PCO as a sample preparation method for AMS radiocarbon analysis through comparative measurements and chemical analysis. The project results will be disseminated through a conference symposium, workshop, and book to disseminate the results of the project to a diverse audience of anthropological archaeologists and physical scientists.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.