Although archaeology is often a reassuringly simple process, some features prove to be too complex to be understood without a great deal of analysis and plain hard work. Burnt mounds have perplexed archaeologists for decades, but now with the application of scientific research to archaeological post excavation we are getting, step by step, closer to a more complete understanding of them. This is the first in a two part article detailing a little of the laboratory work being undertaken on our burnt mound samples at Edinburgh University by Tom Gardner. It’s complicated but fascinating stuff.
What have we been doing?
This last season at the Bradford Kaims we embarked upon a series of advanced sampling processes in order to test some of our theories about burnt mounds, what they consist of, and how they are deposited. We had been thinking that these enigmatic mounds must consist of multiple individual deposits, and although these events are invisible to the naked eye, we were wondering whether the events may be visible in the palaeobotanical and micro-component record. We implemented a series of stratified phytolith and concurrent thin section samples in order to appraise the botanical record and microstratigraphy throughout the various deposits in the mound, which Tom Gardner, Project Officer North at the Kaims, has processed and analysed for his MSc by Research at the University of Edinburgh. We are now happily at a point where we can present some of the preliminary interpretations of these samples.
Why have we been doing this?
The burnt mounds we have at the Kaims, especially in trench 6, are enormous. They even come close to challenging some of the biggest in Britain such as Beaquoy and Liddle in the Scottish Northern Isles. This means that these mounds must consist of a numerous depositional events, over an undetermined duration of time, with an unknown intensity of deposition. To the naked eye the burnt mounds seem to be a homogenous mass of fire-cracked stone, ash, and charcoal, indicating a uniformity of deposit components, and thus a uniformity of function.
In some of our experimental work at the Kaims, we have tried brewing and cooking using hot stones, and quickly realised that you can brew 40 litres of beer, or cook for 15 people, using just a few stones. That our mounds comprise hundreds of thousands of stones indicates that there must be thousands of individual events, and that they may be visibly different under a microscope. The combination of phytolith sampling and thin section micromorphology was chosen to unpick these potential variations both horizontally and vertically throughout Mound 1, in trench 6 at the Kaims.
What are Phytoliths?
Phytoliths are small silica micro-bodies formed in the cell structure of plants when they intake water and nutrients from soils. When the plant then dies, these silica moulds can survive for millennia, and can be diagnostic of the genera of their host plant, but are regularly diagnostic to a species level, unlike pollen. More importantly however, they can be diagnostic of the particular part of the plant anatomy they come from, and as such can give information as to plant processing patterns and resource use.
Stay tuned for part two: The Results!