Plasma Oxidation Laboratory: Construction of a Multi-Sample Instrument

Shumla School Inc, The, Comstock TX

Investigators

Abstract

With support from the National Science Foundation, Dr. Karen Steelman of Shumla Archaeological Research & Education Center will construct a multi-sample plasma oxidation instrument used to process ancient rock art paint samples for radiocarbon dating. An oxygen glow discharge converts organic material in rock paintings samples to carbon dioxide, which can be radiocarbon dated using accelerator mass spectrometry. Plasma oxidation has been used to radiocarbon date organic binders in mineral-pigmented paintings, as well as many charcoal-pigmented paintings. In recent years, there has been an increased demand by rock art researchers to use the plasma extraction technique for dating studies. The ability to place rock art in a chronological context allows an inventory of images to be studied together with excavated cultural remains from a given archaeological time period. This incorporation of rock art studies alongside other archaeological specialties, such as lithics, ceramics, and weaving techniques, is crucial for developing a synergistic approach to studying past cultures. Before dating methods were developed, only relative ages and approximate age ranges for some distinct genres of rock art were possible. Without a way to place the images in time, archaeologists had mostly ignored these insights into past human cultures. The integration of chemistry and archaeology through this project will directly address a national need for interdisciplinary research. NSF support for the plasma oxidation laboratory fosters collaborations among archaeologists worldwide. In addition, we will train university students interested in archaeological science as interns. More scientists with interests in applying chemical knowledge to archaeological and cultural applications are needed. Public outreach for archaeological science will be accomplished via Shumla's blog, popular magazines/websites, the Shumla Scholars STEM program, and public outreach events. Dr. Steelman has designed a 10 chamber system that has the ability to oxidize 10 paint samples in tandem for batch processing. This will increase sample throughput, decrease analysis time, and reduce costs for rock art dating. By constructing a multi-sample plasma oxidation laboratory, batch processing of paint samples will allow Shumla to expand research for additional archaeological projects. USGS coal (C14-free) and ANU sucrose (modern) radiocarbon standards will be used to test the accuracy and precision of results. At sites where calcium oxalate coatings are present, both oxalate dates from accretions and plasma oxidation dates from paintings agree, suggesting valid results. 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.