More on the Stonehenge bluestone debitage

Two illustrations from the reviewed paper, made from slides of "Group C" foliated rhyolites which may or may not have come from the Pont Season area near Brynberian.  As far as I can see, all of the published slides from this rhyolite group show subtle -- and sometimes quite marked -- differences.

Every journal paper published should attract scrutiny.  And the authors should welcome it.  So here we go.  Here is yet another paper on the bluestone debitage at Stonehenge, from those ever-enthusiastic geologists Ixer and Bevins.  This one is in the WANH magazine -- one of their favourite routes to publication:

Rob Ixer and Richard Bevins

And the first shall be last: the Aubrey Holes and their stones

Wiltshire Archaeological & Natural History Magazine, vol. 114 (2021), pp. 1–17

ABSTRACT
The petrography of approximately fifty ‘foreign’ stones and sarsens excavated from fourteen Aubrey Holes by Hawley/ Newall in the 1920s together with lithics collected from Aubrey Hole 7 by Parker Pearson et al.in 2008 is described and discussed. All the major and minor bluestone lithological groups are present, save for any Altar Stone sandstone. Although relative amounts between the groups differ from elsewhere in the Stonehenge Landscape, this is the result of changing collecting/recording strategies rather than reflecting a true diversity in the debitage distribution. The presence of ‘Rhyolite Group D’, a dacitic tuff, within the stones, corrects the suggestion that this lithology is not a genuine bluestone. However, its relationship to other groups, especially Volcanic Group B (SH38), remains undetermined. This, the last major collection of bluestones to be re-described and incorporated into the modern scheme, completes the reassessment of the 20th- and 21st-century material that has been described in the literature. The way is now clear for a return to a detailed look at the stones.

There is a good deal of repetition in this article, and as the authors themselves state, there is nothing new here -- it's essentially a piece of housekeeping, designed to complete the published records of what the "foreign" materials in the Stonehenge debitage actually are.

All the work recorded here was on existing collections of fragments, except for a small number of fragments collected in recent research at Stonehenge.  The priority seems to have been on the "re-classification" of fragments previously given vague labels into "the modern scheme" -- which is of course the scheme created by the authors.  Many of the samples were "re-classified" and put into the selected categories on the basis of "macroscopic" or hand examination of samples.  Since the evidence in most cases is not presented, we just have to accept that the authors have put the right fragments into the right categories.  I would like more showing and less telling.  

There are some things here that have me worried.  One, because the authors insist that the word "bluestone" is only used for fragments deemed to have come from orthostats, they ignore or marginalise  fragments that fall outside their definition, referring to them as "other lithics" including micaceous sandstone, quartzite, sarsen, flint, greensand and oolite.  That is unscientific, since these "other lithics" might actually be of huge importance in our understanding of which stones got to Stonehenge,  how they travelled, and when they got there.  This introduces bias, and it is unscientific.  I, for one, will not accept a definition of a "genuine bluestone" on the basis of what Ixer and Bevins may have to say about it.  (On the other hand, to their credit, the authors do describe a number of non-igneous samples in this analysed collection -- while dismissing the idea that they had anything to do with the bluestone assemblage......)

Then we come to twenty-five rhyolite fragments assumed to come from Craig Rhos-y-felin (referred to as Rhyolite Group C samples).  In my view Ixer and Bevins have never satisfactorily demonstrated that the rhyolites with fabric assumed to have come from the "bluestone quarry" at Craig Rhosyfelin have not come from other related outcrops across a stretch of countryside.  In fact in their earlier work the two geologists referred to the Post Season area as the source of the analysed samples -- it was only after the "discovery" of a hotly-disputed "quarry" that the provenancing was turned into something claimed to be "accurate to within a few square metres."

Quote: "All Group C lithics have an origin from Craig Rhos-y-felin including the quarry site described by Parker Pearson et al. (2015). Group C rhyolites are an important and widespread group of loose material found throughout the Stonehenge Landscape (‘debitage’) but are not represented amongst the four standing, silicic, bluestone orthostats (Stones 38, 40, 46, 48) but perhaps are from buried orthostat 32d or e (Ixer and Bevins 2011a; 2011b; 2013b). These rhyolites are defined and recognised by having all or many of the following key characteristics: strong to very strong planar fabric combined with lensoidal segregations ; microtonalite clasts; presence of stilpnomelane; discrete zircon; and radiating fine-grained titanite/TiO2 minerals in feldspar-rich layers/lenses). An extreme fabric with lensoidal titanite segregations has been named ‘Jovian’ (Ixer 2012)."

Then there is reference to "the full range of Craig Rhos-y-felin lithologies" including one with a classical ‘Jovian’ texture plus microtonalite clasts and one referred to as "a classical Craig Rhos-y-felin" with all of the characteristic features.    In the Discussion towards the end of the paper the authors again refer to "Craig Rhosyfelin rhyolite" and in their Conclusion there is a gratuitous mention of "the detailed provenancing of Rhyolite Group C to the quarry site at Craig Rhos-y-felin."

To repeat what I said when the original 2011 paper was published by the same authors, the idea that the foliated rhyolites assigned to Group C come exclusively from Craig Rhosyfelin has never been established, and there is so much variation within the group (as demonstrated again in this latest paper) that the fragments at Stonehenge -- in the Aubrey Holes and across the wider Stonehenge landscape -- must have come from a wider area around Pont Season and maybe even further afield.  The attempts here to label  all of these rhyolites as "Craig Rhosyfelin Rhyolites" is extremely misleading, and smacks of an attempt to make an assertion true just through a process of endlessly repeating it.  We already know that none of the Group C fragments found in the Aubrey Holes or elsewhere in the wider landscape has been matched to an existing bluestone at Stonehenge, so the balance of probabilities is that the fragments have simply come from a debris litter. 

Finally, there is no attempt in this paper to demonstrate that all of the analysed fragments have actually come from orthostats.  I maintain the view that many of them probably had nothing to do with the 43 (or maybe more) bluestone orthostats or boulders at Stonehenge, and that they are just as likely to have come from a litter of cobbles and stones left behind as part of an expanse of degraded glacial deposits.  

In summary, this paper does nothing to enhance the view that the Group C rhyolites actually came from a rock face at Craig Rhosyfelin, nothing to enhance the hypothesis of a bluestone quarry at this site, and nothing to enhance the view that the builders of Stonehenge did anything other than making use of what they found in the neighbourhood.

What I would dearly love to see is a map of the extent of "bluestone fragments" across the Stonehenge landscape and an analysis of fragment shapes and sizes which might give us some guidance as to what their origins might have been.

Extra Reference:
IXER, R.A. and BEVINS, R.E., 2011b.
Craig Rhos-y-felin, Pont Saeson is the dominant source of the Stonehenge rhyolitic ‘debitage’.
Archaeology in Wales
50, 21–31