Hammer found in Cretaceous layer

AMS RADIOCARBON DATING OF MODERN STEELS AND ANCIENT IRON ARTIFACTS: A NEW CARBON EXTRACTION METHOD IN USE AT LLNL
UCRL: JC-138722
Authors: Andrea Cook, Earth and Environmental Division
Presenting: Thursday, 2:00pm - 2:45pm
Abstract:
A new sealed double tube combustion method was developed at LLNL to extract carbon from modern steels and ancient iron artifacts. Iron samples were chemically pretreated with 10% nitric acid, vacuum sealed in 6mm quartz tubes with CuO, double tubed in vacuum sealed 9mm quartz tubes, and combusted at 1100C for a minimum of 10 hours. The resulting CO2 was then graphitized routinely using hydrogen reduction with a cobalt catalyst (Vogel et al., 1989). Since only 1mg of carbon is required for AMS, small iron samples can be analyzed (50mg of a 2.0%C iron or 1g of a 0.1%C iron). After the initial developmental phase, carbon yields of 100% were consistently obtained. The radiocarbon age of modern high carbon steel manufactured using only coal as the carbon source was determined to be approximately 39,000 450 BP, indicating that very little contamination is introduced during the sample preparation process. Since the Iron Age began less than 5,000 years ago, the background uncertainties should introduce errors of no more than 40 years in the radiocarbon ages for actual artifacts. Several ancient iron artifacts of known date were analyzed to demonstrate that the new methodology is robust and can be successfully used to obtain the date of manufacture for any iron object, provided that it was made exclusively using charcoal that is contemporaneous with the manufacture of the object. We anticipate that this methodology will be particularly useful to archeologists who currently rely on context to date iron artifacts.

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