Background: Radiocarbon dating of materials is a radiometric dating technique that uses the decay of carbon-14 (14C) to estimate the age of organic materials, such as paper and parchment. The method has been used to date the substrate of a range of significant items, however it should be noted that carbon dating can only date the material itself, the paper or parchment, not media used to add content to the parchment or paper substrate. The Earth's atmosphere contains various isotopes of carbon, roughly in constant proportions. These include the main stable isotope (12C) and an unstable isotope (14C). When an organism dies, it contains the standard ratio of 14C to 12C, but as the 14C isotope decays, the proportion of carbon 14 decreases at a known constant rate. The time taken for it to reduce by half is known as the half-life and the measurement of the remaining levels of 14C in organic matter can be used to give an estimate of its age.
Contributing Studies:
Szmidt, CC, Normand C, Burr GS, Hodgins GWL, LaMotta S (2010) AMS 14C dating the Protoaurignacian/Early Aurignacian of Isturitz, France., “Implications for Neanderthal-modern human interactions and the timing of technical and cultural innovations in Europe”, Journal of Archaeological Science 37:758-768.
Project Description:Five parchment Portolan (early nautical) Charts from the Mediterranean were selected by the curators of the Geography and Maps Division, Library of Congress for radiocarbon dating. The five charts spanned the time period 1320 through 1633 to aid investigations into whether the charts were from the specified time periods, or were created by a cottage industry known to occur many centuries later. An important aspect of the study was a series of controlled tests comparing the radiocarbon content of un-cleaned, possibly contaminated samples, with chemically cleaned equivalents.
Outcomes/Findings:
- The five parchment Portolan Charts selected by the curators of the Geography and Maps Division, Library of Congress for radiocarbon dating were sampled in 2009 by Dr. Greg Hodgins, NSF-Arizona Accelerator Mass Spectrometry Facility, University of Arizona.
- The samples were taken to the University of Arizona where they were cleaned and then radiocarbon dated.
- All five of the Portolan Charts had parchment radiocarbon ages consistent with their historically assigned ages. For four of the five charts, different chemical cleaning treatments applied to subsamples of each chart generated the same radiocarbon age at 2 standard deviations (SD) precision.
- Radiocarbon measurements on un-cleaned samples of each parchment were either the same or very close to the ages of chemically cleaned samples at 2 SD precision.
- Limited controlled testing suggested that modern glue contamination did not significantly influence the results.
