Interest in these features has been awakened by Hugh Thomas through the posting of a drone video featuring this fascinating patch of moorland to the west of Carn Meini (Carn Menyn). Thanks to him for flagging this up.......
The Stone River or stone run is very well known, and has been referred to as an ancient trackway, a moraine, a deliberate stone arrangement or alignment, or a periglacial feature similar to others found in periglacial contexts at high altitude or high latitude in many parts of the planet.
The Wikipedia definition of the feature is as follows:The actual formation of stone runs involved five processes: weathering, solifluction, frost heaving, frost sorting, and washing. The stone runs are essentially different from moraines, rock glaciers, and rock flows or other rock phenomena involving the actual flow of rock blocks under stress that is sufficient to break down the cement or to cause crushing of the angularities and points of the boulders. By contrast, the stone run boulders are fixed quite stably, providing for safer climbing and crossing of the run. Stone runs are accumulations of boulders with no finer material between them. In the Falklands, they occur on slopes of between 1 and 10 degrees, and are the product of mass-movement and stone sorting during past periods of cold climate. They everywhere occur in association with poorly sorted, clay-rich solifluction deposits.
With reference to the "Carn Meini cairn" the excavation of the site (as part of the SPACES project) took place under the direction of Tim Darvill and Geoff Wainwright in 2011, and was written up in 2012 and in the 2016 Prehistory volume of the Pembrokeshire County History (pp 171-173). The authors assumed -- without any solid evidence whatsoever -- that the earliest phase of occupation here was well back into the Mesolithic, since radiocarbon dates suggested occupation around 9,000 years ago and in subsequent millennia. The suggestion that there was a "quarry pit for the exploitation of meta-mudstone" can safely be ignored, since there is no reason why anybody would want to "quarry" metamorphosed shales from here rather than anywhere else, since these rocks cover thousands of acres in the Preseli Hills. Sharp-edged bits of slaty rock may well have been collected, but I have seen no evidence that suggests that this was a "special place." Then, according to TD and GW, there was a second phase involving the "working of dolerite" -- but those words were deliberately chosen to flag up the speculation that this was a special place for quarrying -- and again this is not supported by the evidence. This all supposedly occurred around 4,000 years ago. Then the authors supposed that there was a final phase of meta-mudstone quarrying around 3,500 years ago, in the Bronze age. There are radiocarbon dates, but they are somewhat confusing. On p168 of the County History volume it is all too apparent that TD and GW were all too keen, at the time, fo flag up the "discovery" of Mesolithic quarrying at Carn Meini and to see everything through their Stonehenge rose-tinted spectacles -- as part of their effort to flag this up as a site of "special significance." Pure speculation; no evidence that withstands scrutiny.
What is convincing is the presence here of a standing stone and a cairn that incorporated a burial chamber. A standing stone setting may have been followed by roughly circular ditch and a low outer bank. This may have been re-fashioned slightly off-centre, with the use of some dolerite pillars, around 4,000 years ago, and then this was followed by a final phase of building with the cairn or round barrow with a burial cist and capstone at its core. This was dated to about 3,500 years BP.
In other words, the features here are Bronze Age rather than Neolithic -- and it is extraordinary that TD and GW have tried to interpret this site as if it is an important part of the Stonehenge bluestone story. There is NOTHING here to suggest any link at all with Stonehenge.
The features around Carn Meini fit nicely into the regional context -- with some Neolithic features including remnants of cromlechs, long barrows or passage / gallery graves, and abundant Bronze Age features including embanked circles, burial mounds (as at Foelfeddau and on Foel Drygarn), and standing stones here and there. There's a standing stone circle at Gors Fawr, not far away from Carn Meini. The field patterns around Carn Alw may well be Bronze age too, together with similar features on the flank of Carningli.
So I would characterise this cultural landscape as a Bronze Age landscape, with some older features and some newer ones (including the Iron Age fortified settlements on Foel Drygarn and Carn Alw). The landscape displays an abundance of prehistoric features, as Hugh Thomas and I have been trying to point out for years. The "Stonehenge connection" hypothesis is a complete waste of everybody's time, and it's high time that the archaeological fantasists got real.
PS. I have examined this evidence before, and report on my thoughts here: