Sam Harris, Doctoral Research Student – University of Bradford
Firstly, it is purely coincidental that I study in Bradford (West Yorkshire) and am coming to take samples at the Bradford Kaims. As an archaeomagnetist, and we are pretty few and far between, it is always amazing the variety of sites that you get to see and work on. Having parachuted into the Bradford Kaims trenches for the second time, this site is no exception in its wonder. Placed at the edge of a fen, the variety of soil and sediment types on site is impressive! This offers the perfect opportunity for archaeomagnetic studies.
For those that aren’t quite sure what this odd science (magic) is, you are welcome to peruse my website, which is listed at the end of this blog post, for some answers. Simply put, the Earth has a magnetic field which varies over space and time. A record of the past geomagnetic field can be found in the in situ remains of hearths, furnaces, or other anthropogenically fired features that we as archaeologist excavate on a regular basis. Archaeomagnetic studies seek to improve our knowledge of past geomagnetic field changes through the analysis of this material. Why though, I hear you ask…
This is because we can use the knowledge of geomagnetic fluctuations over time to conduct archaeomagnetic dating and gain an idea of the last time that some fired archaeological features were heated. Having a dating method which directly relates to an anthropogenic activity, rather than to the end of an organism’s carbon absorption for example, is a powerful tool for the archaeologist.
Archaeomagnetic dating was first attempted at the Bradford Kaims in 2011. While the study was successful and the date recovered for a fired hearth feature in Trench 6 (c.4350 cal.BC) was considered accurate given other artefactual dating evidence for the site, newly acquired radiocarbon dating evidence suggests that the calibration methods used for the archaeomagnetic dates produced erroneous results. This was due to the use of an experimental and alternative calibration model from outside the UK, as the current UK calibration model does not stretch back into the Bronze Age or before. This previous study, and others since, have identified the need for further work to be undertaken. This is where me and my PhD come in! My main aim is to improve our understanding of geomagnetic field change during prehistoric periods, but particularly the Neolithic.
At the Bradford Kaims this season, I sampled two features associated with the Bronze Age burnt mounds, both of them interpreted as fire pits containing fired stones, burnt sediments, ash, and charcoal. These features will provide good radiocarbon dating records, alongside the archaeomagnetic signatures for the fired subsoils within and below them.
Thanks to the Bamburgh Research Project’s excellent radiocarbon dating programme at the Bradford Kaims, the fired archaeological features that I can archaeomagnetically study will have independent dates associated with them. By building up a number of well-dated features in this way, a new calibration curve for the UK can be created, with the Bradford Kaims being a central case study in this process. Through the combined use of radiocarbon dating and archaeomagnetic dating on prehistoric sites like the Bradford Kaims, we can gain a more nuanced understanding of their chronologies.
Sam’s website can be viewed at; www.neolithicarchaeomagnetism.weebly.com
Sam’s Twitter can be viewed at; @Archaeomagnetic