Optically Stimulated Luminescence (OSL)

The Tudor Farming Interpretation Group (TFIG) have recently been successful in securing funds to undertake a programme of dating the field system at Under Whitle using a method called Optically Stimulated Luminescence or OSL. The main reason we are doing this is because although we have a number of radiocarbon dates that have shown us when an artificial terrace was being used and of course dates from our peat bog which tells us when plants were growing around Under Whitle, they do not tell us about the development of the field system itself. Field systems often develop over time, and we believe that to be the case here at Under Whitle and this particular method of dating is well suited to the task.

What is Optically Stimulated Luminescence?

OSL is a method of dating which is quite different to radiocarbon dating. Radiocarbon dating is used on organic materials such as bone or charcoal. OSL is used to date minerals such as quartz found in soils. The method is based on the level of radiation found in these minerals, which degrades at a constant rate over time. In this case the source of the radiation is sunlight. As soils are dug, ploughed or otherwise disturbed, the surface which has been exposed to sunlight becomes buried and from that point the radiation trapped in the mineral begins to decay. In our case we are interested in when the soil buried in the formation of earthworks such as banks, field boundaries and lynchets/terraces. We hope to find the dates when these were created to complement the radiocarbon dates we have.

How will it be done?

The work involves taking samples from buried surfaces, which of course means there will be some digging involved. Once the surface has been identified, then care must be taken to avoid exposing the area to sunlight as this will ‘reset the clock’. To take a sample, a corer is inserted into the soil and once secure it is taken to the laboratory for analysis.

Who will be doing the work?

We will be working with Professor Sam Turner of the University of Newcastle and Dr Tim Kinnaird of the University of St Andrew’s. They are specialists in this type of dating and have worked on projects around the world. We have selected 11 potential sites for sampling which we hope will provide a range of dates to help tell the story of when the fields were established.

Community Engagement

As ever we are keen to involve local communities in our work here at Under Whitle and we have invited a number of schools along to see science and archaeology in action!

Dr Ian Parker Heath - Achaeology Consultant