The absurdity of the quarrying hypothesis

Over and again on this blog, I have examined the published "evidence" for Neolithic bluestone monolith quarrying in Pembrokeshire, and have found it wanting. With the extraordinary (in the sense that it is difficult to comprehend) backing of geologists Robert Ixer and Richard Bevins (and a few other geologists brought in as specialists in assorted techniques) Mike Parker Pearson and his fellow archaeologists have flogged to death the idea of Neolithic quarrying at Rhosyfelin and Carn Goedog.  They are now apparently about to look for more "quarries".  They have refused to acknowledge that there is any dissent from their quarrying hypothesis either inside or outside of the specialist peer-reviewed literature, and their "bluestone myth" has been developed and enlarged year on year so that it now incorporates a lost "giant stone circle" at Waun Mawn and a wildly convoluted narrative.  I think it is true to say that many independent observers have finally decided that enough is enough, and have come to the same conclusion as me -- that the evidence presented by MPP in that appalling TV programme fronted by Alice Roberts, and in the literature, is so ludicrous as to be embarrassing.

Every now and then I try to assess just what "the Stonehenge bluestone assemblage" consists of -- ie the full assemblage of bluestone or non-sarsen monoliths, stumps, rock fragments, packing stones, hammerstones etc found within the Stonehenge landscape.  This is my assessment from 2017:

There are at least 18 different rock types, and probably more than 20. That means multiple provenances, exactly as you would expect with a collection of glacial erratics.

** There are 31 dolerite orthostats, of which 14 were sampled in 1991 and 2008. Some are standing stones and some are stumps. Some are spotted and some are unspotted. The spots are now thought to be not felspars but aggregations or clusters of low grade, secondary metamorphic minerals. Bevins, Ixer and Pearce (2014) analysed 22 Stonehenge dolerite samples, and suggested that they were clustered into three groups, with one sample petrologically distinct from all three. So there are three groups and one outlier -- four types. Every one of the 22 samples is unique, and the possibility must be entertained that every one has come from a different geographical location in eastern Preseli.

** There are four above-ground volcanic rocks in the orthostat collection (stones 38, 40, 46 and 48). There seem to be four distinct types - two dacites and two rhyolites. They are referred to by the geologists as rhyolitic tuffs, foliated rhyolitic tuffs, crystal-lithic-vitric tuffs, and argillaceous tuffs. They have come from four different north Pembrokeshire locations. Stone 38 has an unusual mineralogy including graphitising carbon.

** There is not much debris to match the 4 volcanic rock orthostats in the Stonehenge debitage, but similar fragments are found in the great cursus field. In the debitage, unique volcanic material has been classified as belonging to two types -- Volcanic Group A and Volcanic group B. None of the potential parent orthostats for Volcanic Group A (32c, 33e, 33f, 40c and 41d) have been petrographically examined, making it impossible to relate this debitage to any (or all) of the buried stones. Ixer and Bevins (2016) say: ".........on present knowledge the origin(s) of the Volcanic Group A lithics is still expected to be found within the Ordovician volcanic sequences in the north Pembrokeshire area on the northern side of the Mynydd Preseli range probably amongst those outcrops examined by Evans (1945)."

** There are two micaceous sandstone stumps -- numbered 40g and 42c. There are also lumps of Lower Palaeozoic sandstone scattered about in the debitage -- the largest lump weighs c 8.5 kg. There appear to be two types, with possible sources in the Lower Palaeozoic rocks of north-west Pembrokeshire.

** The Altar Stone (stone 80) is a greenish calcareous sandstone, probably from the Senni Beds of Carmarthenshire or Powys. (It is not from Milford Haven.) So just one rock type here. There is some debitage related to this stone, but it cannot be established that the fragments came from the Altar Stone itself (Ixer and Bevins, 2013). The most feasible provenance for the stone is the Laugharne - Craig Ddu -- Llansteffan area of Carmerthenshire.

** In the debitage there are many fragments of rhyolites, some with planar fabrics -- and most matching closely (but not perfectly) the rock outcrops of the Craig Rhosyfelin district. There appear to be three distinct groups of "rhyolites with fabric", all assumed to have come from the Pont Saeson area. There may be a match with orthostat 32e or 32d (Ixer and Bevins, 2011), but the debris analyses does not match any of the known volcanic orthostats.

** There are also some basic tuffs in the collection of fragments from the debitage -- two lithologically different types (Ixer and Bevins, 2013). These are probably also from the Fishguard Volcanic Series.

** Other lithics in the stone collections from the debitage (eg. haematite (from the Reading Beds?), greensand, slate, limestones, Mesozoic sandstones and gabbros) appear genuine, and need further research.

To sum up:

Ixer and Bevins (2014) claim that there are “about ten types of bluestone” represented in the orthostat / debitage samples, but they also show in assorted articles that these have nonetheless come from at least 20 different locations. It is estimated on the basis of the above points that there are at least 30 different rock types represented in the full "bluestone assemblage" -- especially when due respect is given in this count to cobbles as well as orthostats and flakes, for reasons frequently recited on this blog.

It should also be noted that the majority of the 43 bluestone monoliths/stumps at Stonehenge have still not been sampled and analysed. The new work reinforces the idea that the Stonehenge bluestone assemblage is made up entirely of rock types from the west, and that they have come mostly from north Pembrokeshire. 

So has the work published since 2017 changed anything?  

The 2018 article entitled "Megalith quarries for Stonehenge’s bluestones" adds nothing of any interest on spotted dolerite or rhyolite provenancing.  

The 2019 paper entitled "Long-distance landscapes: from quarries to monument at Stonehenge" adds nothing on provenancing but demonstrates the basic ignorance on the part of the authors of the local geology around Waun Mawn.  But the paper has a table listing thirteen different bluestone "rock types" which fails to take into account the substantial differences (demonstrated in the literature) within rock groups that are clearly not uniform in their characteristics. It also assumes sources for rock types that are not demonstrated by research. The 2019 paper entitled "Alternative Altar Stones? Carbonate-cemented micaceous sandstones from the Stonehenge Landscape" flagged up the presence of lumps of sandstone around Stonehenge that might NOT have come from anywhere in Wales.  

The 2020 paper entitled "Constraining the provenance of the Stonehenge Altar Stone" showed that the "Altar Stone" samples examined probably do come from a common source; that the sampled debris at Stonehenge did not come from the Mill Bay Formation; and that the real provenance of the "Altar Stone" fragments probably lies somewhere in the eastern part of the Senni Beds outcrop, far away from Preseli. The 2020 paper called "Provenancing the stones" promises much but delivers almost nothing  -- but demonstrates that the geologists have recognized that the Stonehenge bluestone monoliths and debitage have come from multiple sources, some of which are still unknown.  However, the article demonstrates that for Ixer and Bevins, the quarrying obsession persists. 

The 2021 paper entitled "Revisiting the provenance of the Stonehenge bluestones: Refining the provenance of the Group 2 non-spotted dolerites using rare earth element geochemistry" shows that there are no preferred and known unspotted dolerite sources which can be identified as quarries, but rather multiple scattered sources, not one of which has yet been “nailed down” by hard evidence. The 2021 paper called "The original Stonehenge? A dismantled stone circle in the Preseli Hills of west Wales" mentions quarries but contains no geology whatsoever -- and demonstrates an ignorance of basic geology that would have been obvious to any geologist in the field. The Ixer/Bevins paper called "And the first shall be last", which examines the "bluestone" content of the Aubrey Holes, 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. Further, the new research shows that fragments of many different "bluestone" lithologies are widespread across the Stonehenge landscape, and that there is considerable variation in the group of samples somewhat prematurely ascribed to Rhosyfelin. Strangely, greensand, limestone and other "minor lithologies" represented in the fragments collections are simply dismissed as "non-bluestone lithics"..........

There are other papers too, with a great deal of repetition in them, which can be ignored.  If the hard evidence presented in geological work is assessed carefully, and separated out from the quarrying and provenancing assumptions of geologists Ixer and Bevins, the conclusion is obvious.  In the "bluestone assemblage" at Stonehenge there are around 20 different rock types and around 30 different provenances.  This much has been obvious for a decade or more, and the conclusion is reinforced by every new paper that appears.  No new evidence has been brought forward in the last decade to support the idea of "bluestone monolith quarrying" -- and the very idea is shown to be completely absurd.

Things that are repeated  by the geologists ad infinitum do not automatically turn into the truth, and worthy as much of their research is, it is dragged down by a lack of targetted fieldwork either at Stonehenge or in West Wales.  The collections of rock fragments and thin sections at Stonehenge and in assorted museums have been worked to death, and used quite cynically for the furtherance of an hypothesis that should never have seen the light of day.