The results from our carbon 14 samples have arrived, always an exciting time. Was there enough good charcoal for a date, has it been contaminated by the earlier dig on the site, will it turn out to be a date we hoped for. The e-mail flashed up in the right hand corner of my screen and I let out an excited cry, much to the surprise of my colleagues who all stopped working to ask if I was ok. I opened the results but could not look, ….. deep breath and eyes open ….
Phew! we have some answers, and as suspected not a simple result! Many thanks to Gordon Cook from the radiocarbon lab East Kilbride, for the results and the extra explanations and information, I will try to explain it with my non science mind 🙂 C14 dating has developed over the years and new information can be added to the mix to help pin point a date. Radioactive decay of the C14 isotope is not constant, as shown in the wiggly blue line on the chart above. For some periods it flat lines and one area is AD 400-550 making more precise dating more difficult. The sample of charcoal from above the early rectangular bath footing in the north range at Chedworth has two date range spikes of AD 131-262 77.6% and AD279-328 17.8%. This is probably due to the charcoal coming from different types of wood, older dates will come from old timber and later dates from twigs and branches. Also we had re excavated the site and may have some contamination from the earlier disturbance.
The grain from the south range we are 95% certain that it was burnt AD388-564 or for the alternative sample AD329-537. When these were jointly calibrated we got AD385-539. So the mid-point over that 154 year period would be AD462, and we can reasonably say we have a sub-Roman date.
The last date from the charcoal around the crucible found in the soils running under the stone steps to the upper baths are 68.2% AD128-231 and 92.9% AD72-256 which again unfortunately falls in another flat line in the calibration curve. We knew we may not get a very good result from the bath house, but we are very happy with the grain result! What this all means now is many more discussions and new theories to add to the story of Chedworth Villa, one more piece for the jigsaw 🙂
Interesting. As I sit in bed I’m trying to work through the dates. Am I right in thinking the charcoal indicates late Roman occupation, whilst the grain shows continued usage after the end of the Roman occupation of Britain?
Hi Julia, yes the grain suggests use after the end of the villas heyday, it could be continued use or a re use of the south range buildings. The charcoal was a bit difficult to read as it suggests too main areas of dating but is most likly to be the later 2nd/3rd century dates. With not a lot of layers left by previous excavation we had very small areas from which to collect the charcoal. The rebuilding of a bath house on top of the earlier one may link into the date we got back. More work as ever is needed to add to the picture 🙂 the usual case of solve some questions but find more to ask! cheer Nance