Well well, you could knock me over with a feather. Just when I thought there was nothing much to say about extraction pits, bluestone monoliths, sockets and archaeological artifices, along comes a southerly gale, down goes a very large oak tree in the wood at the back of the house, and all is revealed.
What has happened is this. In the Cilgwyn Valley there is an undulating surface of rocky outcrops and moraine, with large dolerite boulders and other erratics all over the place. Over the millennia a mature woodland has developed, comprising oak, hazel, ash, holly, rowan, and sycamore for the most part. The trees are safe as long as they do not get too tall, but if one tree has a crown above the rest of the canopy, it becomes vulnerable, and even top-heavy -- and eventually, in a gale, it will come down.
That's exactly what happened the other day. So what's all this got to do with archaeology? Quite a lot, as it happens. I have talked about biological processes before, in the context of the supposed "quarry" at Rhosyfelin. Then, I was talking about the role of rocking trees and bushes, and expanding roots, in forcing slabs of bedrock to part company with the parent rock and to come crashing down, contributing the the accumulating mass of rockfall debris at the base of the slope.
Here, near the Cilgwyn Waterfall, we are talking not about monoliths falling, but being lifted into the air.
When the tree came down, the root mass, which was of course horizontal, embedded into the stony ground, was tilted through 90 degrees, ending up vertical. It carried up with it a large quantity of stones and boulders, the biggest of which is this dolerite "triangular pillar" weighing about 2 tonnes. It has all the features of a highly abraded and weathered glacial erratic. The moss-covered area id the part that was previously exposed at the ground surface. So there it sits, about 2m above the ground surface, supported on a tangled pedestal of roots, soil, leaf mould, cobbles and smaller boulders. There is quite a lot of clay too. At the ground surface there is a large pit that was previously occupied by the root mass. It's about 50 cm deep, and 1m x 3m in extent. It contains a lot of debris, including smaller stones which were in contact with the large boulder that has been lifted into the air. In another context these might be referred to as "packing stones"......... and the sides of the pit are not vertical but damaged and degraded by the occurrence -- in this case -- of a rather catastrophic event.
So what happens next? Assuming no human interference, the "bluestone monolith" could remain on its pedestal for weeks, months, years, decades, centuries or even millennia. It's not all that solidly "gripped" by roots, so my guess is that it will come down sooner rather than later, as rain washes away the finer material in the pedestal.
And what will people find in a thousand or five thousand years' time? Well, they will find the hollow from which the boulder was extracted, with these smaller stones more or less where we see them now, probably filled with a mixture of slope wash debris, leaf litter and the rotted remains of the oak tree root system. The full rotting process could take many centuries, since this is an oak tree. If this woodland should be set on fire at any stage, either as a result of a lightning strike or because it is burnt for clearance purposes, there could be ash, charred fragments and even charcoal incorporated. When the monolith does eventually slide off its pedestal and find its "final resting place" it is most unlikely to end up where it started off -- it could even be a few metres away, with a completely new alignment. Then the soil surface will gradually build up around it, eventually burying both the boulder and the sediments beneath it.
So we end up with an extraction pit containing smaller stones and assorted sediments easily differentiated from those in the sides of the pit, dateable organic sediments, and a measurable gap between the extraction of the boulder and its eventual repositioning following the removal of its supporting pedestal.
This process is a perfectly valid one if we seek to explain what has been uncovered in the excavations at Waun Mawn. But surely the Cilgwyn Valley contains a sheltered and prolific woodland, whereas Waun Mawn is a wild and windy -- and treeless -- moorland? Not so fast, dear reader. It was not always thus.
Not far away is the famous tor called "Carn Goedog", where MPP and his merry gang have been excavating. That means "woodland carn", and the presence of bluebells around the crag is a pretty good indicator of mature woodland not so long ago. The windswept appearance of the moorlands today is largely down to management -- and several centuries of grazing by sheep and other animals. Gorse clearance by burning has played its part too. Not far away from Carn Goedog, at the enclosed "summer settlement" of Hafod Tydfil, there are healthy mature trees growing in abundance, simply because they have been protected from animal grazing. And at Waun Mawn itself, we know that it was once designated as a "deer park" and was used as such in the Middle Ages. Deer parks did not exist on wild moorlands; on the contrary, they were densely wooded, so that deer, wild boar and other animals could be hunted with the help of abundant cover by the lord of the manor and his cronies.
So there we are then. The features at Waun Mawn which have excited certain archaeologists and left the rest of us rather unimpressed can all be explained by natural processes. All we need are some dolerite boulders or monoliths littering the landscape, some mature trees and the occasional gale.