Here is the short paper on which I have been working for some time. It was high time for an unbiased description of the geology and geomorphology of the site, together with a scrutiny of the claims made by Ixer and Bevins on the geology front and Parker Pearson et al on the matter of the imaginary quarry.
It's a preprint which has not been peer-reviewed -- so I hope I get some creative feedback both here and on the Researchgate platform. I may submit it later for journal publication,
Geological analyses show that the dolerite sills of the Fishguard Volcanic series on the north flank of Mynydd Preseli are geochemically heterogenous, with substantial lateral and vertical variations. Many sills are still inadequately mapped and sampled. The Carn Goedog sill is exposed at the surface at Carngoedog, Carn Breseb and Carn Ddafad-las and at multiple other locations, with a surface outcrop extending over at least 450,000 sq m. While geological differences have been demonstrated between the three main tors, claims of “precise provenancing” of certain Stonehenge fragments to the Carngoedog tor are of questionable validity. Even more dubious is the claim that nine of the Stonehenge bluestone monoliths have been quarried at Carn Goedog, since eight out of the nine are heavily abraded boulders and slabs which look like ancient glacial erratics rather than sharp-edged and fresh pillars extracted from the parent rock. Geomorphological studies on the extensive Carn Goedog tor reveal that it is dominated by terraces, crags and hollows with very little scree. Pillars suitable for use as monoliths are restricted to a few small areas on the tor, in locations difficult to access. Jumbled frost-shattered blocks of all sizes dominate the tor landscape, with dolerite outcrops in various stages of disaggregation and collapse under gravity. There are many boulders and slabs with sub-rounded edges, indicative of either many millennia of weathering or of abrasion and redistribution by glacier ice. Frequent moulded and smoothed surfaces on the tor also indicate that the influence of over-riding ice (probably during both the Anglian and Devensian glacial episodes) has been considerable. Examinations of the supposed “Neolithic quarry” site on the south flank of the tor have revealed no traces of quarrying, apart from a few signs of modern activity. All of the features referred to as “engineering features” are found to be entirely natural. Stone tools, if they are correctly labelled as such, owe nothing to quarrying activities, and are present simply because there is a long history of intermittent occupation at this site adjacent to a major routeway across Mynydd Preseli. Soft shale “wedges” supposedly used in the process of extracting fracture-bounded pillars from the rock face are entirely natural; indeed the idea that soft pieces of shale would be hammered into dolerite fractures defies the principles of rock mechanics. Radiocarbon dates ranging from Mesolithic to medieval times do nothing to underpin the quarrying hypothesis. It is concluded that there is no Neolithic quarry at Carngoedog, and that if blocks of spotted dolerite have indeed been extracted and transported away from the vicinity of the tor, the agency was glacier ice.
(PDF) Carn Goedog and the question of the "bluestone megalith quarry". Available from: https://www.researchgate.net/publication/332739336_Carn_Goedog_and_the_question_of_the_bluestone_megalith_quarry [accessed Apr 29 2019].