So how do you actually date an ancient stone circle?

A Scottish farmer has admitted that the ‘ancient’ stone circle located on his farm was actually built in 1990s, which leaves us asking: how can you actually date a stone circle?

This week, archaeologists got very excited about the identification of a previously unrecorded Recumbent Stone Circle in Aberdeenshire, a type of monument unique to the north east of Scotland and generally thought to have been built during the Bronze Age between 3,500-4,500 years ago.

The stone circle was initially reported by the land’s current owner and, when officials came to inspect it, they noted some unusual features, including its small diameter and proportionately small stones. But given the huge amount of variation between Recumbent Stone Circle, it didn’t set any alarm bells ringing and, for a few days at least, the discovery was celebrated by Historic Environment Scotland and Aberdeenshire Council’s Archaeology Service as a genuine new discovery.

But the jubilation was not to last. A few days after the news went viral, another farmer who had worked the land before its current owner took over stepped forward and admitted that far from being an ancient stone circle, it was one he himself had built in the 1990s.

Cue the mocking headlines like ‘fake stone circle!’, ‘redfaced archaeologists’ and ‘ancient stone circle not so ancient after all’. But don’t be too hard on the archaeologists involved: stone circles are notoriously difficult to date and, even when you have a genuine one, the very nature of these sites presents archaeologists with a real conundrum…

So how do you actually date a stone circle?

Ok, so let’s imagine we’ve found a stone circle. Let’s also imagine that our stone circle has passed any initial assessments of not being modern – it’s the right kind of size and shape compared to other known monuments in the area, it’s made of the right material, and there’s no aerial photographs from the last century that indicate it wasn’t there a few years ago. So, how could you actually figure out how old it was?

Unfortunately, techniques like radiocarbon dating can’t be applied to stone, and even if you do use a scientific dating technique that can tell you how old stone is, all you’d learn is when the stone was formed geologically, and not when the stones were cut and put into place.

One approach archaeologists can take is to excavate around the site and find some evidence that can tell you when it was in use. Unfortunately, unlike other typical archaeological sites such as settlements or burial grounds, stone circles can often be pretty barren. Things like burials, pottery, bones, and tools are rarely found and, even if they are, they’re often from later phases of use. What’s more, stone circles have often been built and rebuilt over huge periods of time, meaning that it can be quite unclear when building started.

Likewise the ‘radiocarbon date whatever you can get your hands on’ approach would require a seriously big budget to get enough samples analysed to come up with any sort of answer!

Another approach is simply to compare its form to another stone circle that archaeologists have been lucky enough to recover dateable evidence from. But, if you’re up against someone determined to build a very realistic replica, you can be easily misled! As Neil Ackerman, Historic Environment Record Assistant at Aberdeenshire Council pointed out, the stone circle recently discovered in Scotland was an unusually well informed replica, that showed some pretty intimate knowledge of what genuine stone circles in the local area looked like.

Your best bet is probably to excavate the stone-hole into which one of the stones has been placed and cross your fingers that you find some dateable material at the bottom. This is basically the equivalent of removing part of a wall to get at a building’s foundations to see if there are any clues down there that can tell you when those foundations were dug. The problem is that unlike a wall, removing a standing stone is rather frowned upon…

However, these days, things are looking up for archaeologists who do get permission to excavate a stone-hole. In quartz or silica rich deposits, a new technique called ‘Optically Stimulated Luminescence’ dating can reveal when a deposit last saw sunlight. Assuming they’ve not fallen over and only recently been put back up, that could give you a pretty good clue at least to when the stones were originally put in place.

For further reading, try Historic England’s publication on prehistoric henges and circles, or Guerilla Archaeology’s insightful assessment of another ‘fake’ stone circle at Glastonbury.

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Written by Maiya Pina-Dacier

Head of Community at DigVentures, Maiya digs with a trowel in one hand, and a Twitter feed in the other. She reports on all our discoveries live from the trenches, and keeps our Site Hut full of the latest archaeology news. Got a story? Just drop her a line...

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