The Cairns Day 17 – 2019

Hello again to the Cairns followers – it doesn’t seem a year since I was last here on site, and writing once more for the blog! I’m Jo McKenzie, a research geoarchaeologist with the University of Bradford and currently one of the small team working inside the broch as we go into the last couple of days of the excavation.

This is the third year that I’ve been one of the visiting specialists at the Cairns, and as always it’s been amazing to see the development of the excavation and how much changes as – especially for me – we progress through the deposits preserved in the broch interior.

As a geoarchaeologist, my focus is using a range of archaeological science techniques to investigate the soil deposits on site. At Cairns, my analyses will hopefully help us understand the very important floor surfaces which are now exposed in almost all areas inside the broch. I’m using a technique called soil micromorphology to enable us to look at the floors in a way we can’t using traditional excavation methods. Small blocks of deposit are carefully removed, using a metal tin so that they remain undisturbed. Resin is poured into these blocks and hardened, allowing a microscope slide to be made through a ‘slice’ of the floor surface.

Under the microscope, we can examine in detail what often prove to be many, many more deposits that can be seen with the naked eye. This technique is a powerful tool for understanding how the floor surface deposits form and the microscopic information they contain – fuel residues, bone, plant residues and other pointers to human activity, as well as a whole range of indicators for environmental conditions on site and how these have changed through time. 

This year at the Cairns however, it’s been a case of less sampling and more trowelling, as it becomes clear that we’re getting closer to what could be the absolute primary surfaces within the broch – a crucial stage and one that it’s so important to get right. All samples are meaningless without understanding their archaeological context, and so this year I’ve mainly been within the so-far largely unexcavated south east quadrant of the broch, carefully cleaning the complex activity surface we can now see there, doing some head scratching, and making comparisons between the sequence of hearths, floors and features we see in this quadrant and those of the other areas of the interior, so that we can plan the next stage of our sampling strategy. Roll on next year, and once again, so many thanks to Martin and the rest of the Cairns team for a week of the most amazing archaeology!

Thanks to Dr Jo McKenzie, University of Bradford