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Sunday, 5 January 2014

Geology of the Trefael Stones

 The main Trefael Stone --  photo by Paul M.  Note the cupmarks and the bluish colour on the 
broken face

The second stone near Trefael  -- once a standing stone and later dumped into the hedge?  
Or maybe once a gatepost, and later rejected?
(Photo: George Nash)

 There is an interesting letter from Rob Ixer about the recumbent Trefael Stone (and other things) in the latest edition of Current Archaeology.   I assume that the letter relates to the second stone found near the edge of the field.  I agree that this doesn't look like spotted dolerite, and that it might be an unspotted dolerite.  I'll take issue with Rob's use of this phrase:  "probably a joint block taken from a Preseli dolerite outcrop....."  Dodgy assumption.  "Derived from" would have been a better phrase for a geologist!

The presence of elongated lumps of dolerite in the tract of country to the north of the Nevern Valley is rather intriguing.  There are quite a few of them, and this led OT Jones to speculate that maybe there was at one time a glacier flowing northwards from Preseli -- he assumed that they were erratics.  There are two further possibilities:

1.  The dolerite orthostats are not from Preseli at all, but are glacial erratics carried from Pen Caer.  That would indicate ice movement west to east -- possible but not probable.

2.  The orthostats (including the one in the photo) were collected as gateposts within historical time by farmers who lived in the area.  Hundreds of gateposts throughout North Pembs are made of elongated "pillars" of dolerite -- and we know from historical records that farmers used to go up into the mountains to collect them.  Much more long-lasting than gateposts made of oak.......

More to be revealed, I'm sure.



In your recent article about the Trafael stone (CA 276), it was suggested that the (now recumbent) standing stone found close to the monument was 'probably Preseli spotted dolerite like those found at Stonehenge'. However, while careful re-examination of the photograph confirms that the rock is probably a joint block taken from a Preseli dolerite outcrop, unlike the majority of the Stonehenge dolerite orthostats, it is unspotted. Further macroscopical and new microscopical examination is required before any serious Stonehenge connection could be verified, as - despite the recent confirmation of four small spotted dolerite fragments from Silbury Hill - the dearth of authenticated spotted dolerite orthostats, or even 'debitage', within secure archaeological contexts away from Stonehenge is remarkable.
       This also appears to be true for its use in pottery, as no Stonehenge dolerite (or any other bluestone) has been recognised as temper from any [Neolithic] Grooved Ware pottery. This includes pottery found at Trafael and, more significantly, at Durrington Walls and elsewhere in Wessex. What a contrast with the Inka, who used 'off-cuts' from their highest-status buildings to use as temper in Capitol Inka/ Inka Fine Ware, their finest pottery.

Dr Rob Ixer.

Current Archeology (no. 286, January 2014)


geocur said...

I don't think the stone in the pic had been a gate post . There are quite a number of "stone"s marked on the large scale OS map 1889 map of the area all singular and not associated with boundaries .It looks like that particular one was removed from it's original setting and dumped at the edge of the field .

BRIAN JOHN said...

That's what George Nash says -- speculation or evidence?

geocur said...

What little evidence we have suggests gate post is the most speculative. It doesn't look like a gate post ,the stones on the map are singular and none are on boundaries. Further , standing stones have been used as gate post ,so even in the less likely event it could be shown to be a gate post it doesn't exclude the possibility that it was a standing stone prior to re-use .
If the stones in the area were gate posts it seems a strange circumstance to find that in all the examples one has been removed and one left and no indication of boundaries ,cattle scratching post is much more likely .You tend to get them singly and not at boundaries .

chris johnson said...

Given the imaginative fervour gripping North Preseli we should include a third possibility - human transport of orthostats from Pen Caer to the Nevern Valley for the building of a grand unification complex around Castell Mawr.

BRIAN JOHN said...

Well, why not? A few mini-unification projects all building up to a mego-unification project. There is no limit to this political fantasising....

TonyH said...

Yep, folks, why not? Especially as Pen Caer/ The Strumble isn't that far from the well - known Carreg Samson closed chamber tomb, which is a very important tomb in MPP et al's entire notion [page 326, STONEHENGE, MPP, 2012] that the earliest immigrant farmers, speculatively from northern France and Brittany, made Pembrokeshire one of their points of origin in
Wales/ Britain. Pottery expert Alison Sheridan "is certain that a pot from the burial chamber of Carreg of a style identical to that made in Brittany before 4000 BC. She reckons that,
in large measure, the Neolithic way of life was brought by migrating Continental farmers as a 'package' rather than just its separate components being imported by the indigenous hunter-
gatherers. Once farming had arrived in Britain, it was adopted by the locals.'
Someone once said, famously, "it pays to speculate, in order to accumulate". I'll leave it there!

Dr George Nash said...

Hi Brian, concerning the monolith, it once stood in the next field to the Trefael Stone and was grubbed-up by the late Mr Richards (landowner) during the mid to late 20th century. He was the man who showed me where it was. The only problem is to work out its geology. As far as I am aware, the stone has never been looked at by a geologist (apart from yourself). I do have thin sections though of the Trefael Stone.

BRIAN JOHN said...

Thanks George -- interesting info. No, I haven't looked at the recumbent stone. If you can tell me where it is, I'll try to pop over and have a look at it......... easily visible, or now covered in jungle?!

TonyH said...

I was led to believe that Dr Rob Ixer, Geologist often mentioned on these Posts, has been involved in the work and excavations relating to the Trafael Stone site. Perhaps one of his acquaintances may be able to shed some light on this, and any conclusions he has made e.g. in relation to analysis of pottery sherds from thereabouts.

TonyH said...

New Post on the BBC Website, dated yesterday, 13th January. George Nash is maintaining a case for Continuity of Ritual Use, or at any rate, use commencing in the Mesolothic period. No mention of the Stone's Geology but speculates the cupmark patterns bear resemblances to constallation patterns which encourages his thinking that the Stone was originally horizontal in position.

TonyH said...

In 2011, "after examining the [missing standing] stone the team geologists, Isabelle Therriault and Rob Ixer, identified it as an igneous rock, probably Preseli Spotted Dolerite..........While it has yet to be confirmed, we believe the Trafael Stone may be of a similar local geology....