Radiocarbon dating

What does a Science Advisor do all day?



Much earlier this year on a visit to the submerged forest at Erith I had found what appeared to be a hurdle; woven from thin pieces of wood. My colleagues in Historic England at Fort Cumberland had identified the wood as Ash (Fraxinus excelsior) and the samples were sent for radiocarbon dating.  Today we got the results of the dating the fragments of ash wood date to the Bronze Age which is excellent news as this is consistent with other dated material from this part of the submerged forest and is exciting as the structure is likely to have been made humans rather than the trees which were overwhelmed by rising river levels.

Next I was asked for advice about a site where Vibro columns were proposed as means of ground improvement. It is very common for buildings to built using piled foundations. This method is often referred to as piling but this is misleading. Vibro columns involve a very different approach mechanically. The particles in the deposits are shaken down into place to provide a more compact and solid base for building upon. How these methods impact archaeological deposits is still poorly understood. We do know that it causes movement and settlement over a wider area and is likely to adversely affect any archaeology present. To find out more about piling and archaeology see

I then joined colleagues from GLAAS (Greater London Archaeological Advice Service) and Development Management team for a visit to the Curtain Theatre excavations in Hackney. Here the knucklebone floor which had been much admired and re-tweeted recently was being reburied. The controlled reburial of archaeological remains to preserve them is referred to as preservation in situ this can be permanent or temporary.  The area to be reburied had been covered with a special membrane Terram and the next stage was for it to be covered with sand. The type of sand used is very important it has to be able to be packed down evenly to provide a buffer layer between the archaeology and what is to go above it and also has to have a low Iron content to avoid leaching into the archaeological deposits and potentially damaging them.

My next task was to work on our next training event. Over the last year or so we have been putting on a series of one day training sessions on Human remains in commercial archaeology, ethical legal and curatorial considerations.  These events have been very well attended and the feedback has also been very positive. The audience has included curators, consultants and contractors. This has involved lots of input from colleagues within Historic England both for technical input and logistic arrangements and also many external speakers from local authorities, universities,  the Church of England and the ministry of justice as well as and archaeology companies and freelance specialists.

So a full and varied day of archaeological science.


Death, dating and dirt

This year despite doing the same job in same location as I have done for the previous 3 Days of Archaeology the name of organisation I work for is different. This is due to the recent split of the old English Heritage into Historic England (who I work for) and the English Heritage Trust. Historic England is the public body that looks after England’s historic environment by championing historic places, helping people understand value and care for them.  English Heritage cares for over 400 historic buildings, monuments and sites.

My day started with reading some new guidelines from APABE – the Advisory Panel on the archaeology of Burials in England which had been written by my Historic England colleagues Jane Sidell and Simon Mays. More and more projects are taking place on land which includes some very large burial ground so this guidance is particularly welcome.

Next I read and responded to a number of WSI (written schemes of investigation) for commercial projects in London. These are basically method statements and have to be approved before work can commence. My colleagues in GLAAS Greater London Archaeological Advisory Service provide advice to the planner in many of the London boroughs (the City of London and Southwark have their own in house archaeological advisers). The archaeology advisers will contact me on projects which include aspects of archaeological science such as Geoarchaeological borehole surveys. Random interesting fact 1 – when writing about the East and North East London wetlands the term Lea is used for the natural river valley and its deposits whilst Lee denotes the manmade channel of the Lee Navigation.

The highlight of my morning was a site visit to see the Crossrail site of Bedlam near Liverpool Street which is being excavated by archaeologists and osteologists from MOLA. All staff on site must to wear full PPE (personal protection equipment). Random interesting fact 2 – because this is a rail project the colour of that clothing is orange rather than the more familiar yellow. So for the purposes of my visit I donned the full orange.

The skeletons were being carefully recorded before being excavated. The site is covered by a large tent in order to shield the public from accidental views of human remains but is also makes the process of excavation a lot easier for the archaeologists especially on rainy days. In addition to evidence relating to the use of the graveyard, a large quantity of bone working waste had been found this week, which comprises mostly sawn through fragments of cattle metapodials (cannon bones) including a fine example of a pinners bone. These were used to hold the metal blanks during the process of filing them down to fine points. Examples of these artefacts are online.

After lunch I joined my colleagues in GLAAS for some training in Radiocarbon dating from Alex Bayliss. Establishing the chronology of a site is key to understanding and interpreting the archaeological features and finds present. Helping to arrange and provide training both inside the organisation and for the wider sector is a big part of the work of the Science Advisors.

Alex’s presentation on radiocarbon dating

Alex’s presentation on radiocarbon dating

On returning to my desk I checked my email and was pleased to discover that the results of a project looking at what we currently know about London’s burial grounds was now available online. This project was carried out by Allen Archaeology and funded by Historic England.

Sylvia Warman, Science Advisor Historic England

Core blimey! Jason Stewart and the Sediment Core Samples

The best thing about working as a geoarchaeologist at MOLA is the variety; one day I could be watching a machine ripping through the odorous remains of a 19th century gas works, the next day could find me wrestling with the implications of a newly returned set of radiocarbon dates.

Today however finds me in the lab examining sediment cores retrieved from an evaluation. The site is in Dartford within the Thames estuary and has early prehistoric peat forming on top of the cold climate landsurface with various phases of being mudflat, marshland or flooded.

The cores are carefully laid out with the top of the borehole at one end of the lab and the base at the other. As there is 16m of sequence and the cores are 1.5m long and filled with heavy sediment this can take longer than you would think.  The cores are then methodically cleaned and the colour texture, inclusions and nature of the boundaries are recorded.  This detailed cleaning and logging allows me to think about the depositional environment of the site and the nature and rate of the changes that occur.

The next task is to select the locations from which to take samples, we take samples for radiocarbon dating, this enables us to places the changes in environment in some kind of chronological framework allowing us to compare the developments onsite with other work we have done in the surrounding area.  We also sample for things which will tell us about the environment in the past (usually pollen, diatoms, ostracods and plant remains).  These are carefully sliced from the core and sealed in labelled bags to be sent off to the various specialists.  The cores are then re-wrapped and returned to their climate controlled environment, the lab surfaces cleaned and the results typed up.

Jason Stewart

Radicarbon dating samples

Was able to escape the thrills of writing about pigs diets and isotopes, as I was just dragged off to advise on, and select samples for radiocarbon dating from the Banjo enclosure at North Down, Dorset. This is a large Bournemouth University dig, which had a team of up to 160 excavators and specialists. The 2011 season finished only a couple of weeks ago and post-ex is now in full swing. As for the samples, there wasn’t a lot to choose from. It’s crucial to pick a bone (or whatever else) that you can be confident has not been kicking about for long periods prior to ending up in the deposit you want to date. You don’t want to waste your money dating something that was dug out of a much earlier pit before finding its way into your deposit. One bone, a cattle radius, was about three quarters complete and although it had evidence of weathering showing it could have been on the surface for some time I’m confident it will provide a good date for the ditch from which it came.