I was asked again about "Pigs from Scotland at Stonehenge" - the latest science says; "no". For details see:
www.Sarsen.org
Musings and bookmarks about Stonehenge and related stuff.
Wednesday 6 March 2024
New lead isoscape map for archaeological provenance studies in Great Britain
Links between Distant Monuments
Tuesday 20 February 2024
Antiquity Article: Beyond the bluestones: links between distant monuments in Late Neolithic Britain and Ireland
Monday 29 January 2024
What about the Bluestone pXRF studies?
The recent paper on Stonehenge Sarsen Debitage* ends with this conclusion:
"Our key message is that studies attempting to use surficial (pXRF) analysis to provenance any excavated artefact must demonstrate that weathering processes following burial did not significantly alter the primary chemical signature of the material before any meaningful provenance interpretations can be made."... "Any future attempts to provenance excavated dolerite fragments at the monument (likely derived from the in situ dressing of megaliths and/or the removal of flakes in more recent history) must consider differences in the weathering regime experienced by the buried fragments, exposed potential outcrops and standing stones. Due to its mineralogical composition, dolerite is more susceptible to chemical weathering than sarsen. Thus, one should expect differences in weathering to be much more significant between buried dolerite fragments exposed to subsoil weathering, and dolerite outcrops and megaliths exposed to differing intensities and durations of subaerial weathering."
This obviously could be thought to apply to the existing analysis of the bluestone dolerites, and any other non-sarsen stone.
So is there a problem?
Firstly, apart from the Newall boulder (https://www.sarsen.org/2023/07/the-erratic-that-came-in-from-cold.html), all the pXRF analysis has been on exposed Stonehenge stones comparing to exposed Welsh rocks, so they are like for like comparisons. And the Newall boulder was further analysed to show it was part of a broken monolith from Craig Rhos‐y‐Felin**
Secondly the geochemistry revealed by xPDF is only part of the story. The recent Ixer, Bevins et al papers have also used petrology, understanding the matrix of the rock, to identify sources.
For instance in Bevins, Richard & Ixer, Robert & Webb, Peter & Watson, John. (2012). Provenancing the rhyolitic and dacitic components of the Stonehenge landscape bluestone lithology: New petrographical and geochemical evidence. Journal of Archaeological Science. 39. 1005–1019. 10.1016/j.jas.2011.11.020 the authors showed how Craig Rhos‐y‐Felin rhyolite had been misidentified as microtonalite, the geochemistry was very similar but the petrography different. This holistic approach to identification instills confidence.
But the big difference is in the nature of the stones. Sarsen is over 99% silica, it is the white Wonderloaf of rocks. The various bluestones are complex rocks with other compounds in great abundance in them. So the presence of a small amount of chemical changes from weathering is important on Sarsen but not for bluestone. As Rob Ixer says; "A smear of marmite on plain buttered toast would be tasted but the same smear on jalapeno-anchovy toast would add nothing."
So the valuable lesson of the problems of using pXRF on Sarsen for sourcing studies doesn't cause worries about the reliability of the recent Bluestone papers, and is unlikely to be a problem in the future.
T. Jake R. Ciborowski, David J. Nash, Timothy Darvill, Ben Chan, Mike Parker Pearson, Rebecca Pullen, Colin Richards, Hugo Anderson-Whymark,
Journal of Archaeological Science: Reports, Volume 53, 2024, 104406, ISSN 2352-409X,
https://doi.org/10.1016/j.jasrep.2024.104406.(https://www.sciencedirect.com/science/article/pii/S2352409X24000348)
Richard Bevins Rob Ixer Nick Pearce James Scourse Tim Daw
https://onlinelibrary.wiley.com/share/author/YUUAUVRWBNTZTPSQVBGM?target=10.1002/gea.21971
Sunday 28 January 2024
Possible Stonehenge Debitage Sources
The two "exotic" sources Nash et al identify as possible sources for sarsen at Stonehenge are Stoney Wish near Ditchling Sussex and on the side of the A272 near Bramdean in Hampshire.
To help identify them here they are:
There is a question mark over where the Bramdean stones originated as the circle of stones seems to date from about 1845 - https://pastrambles.wordpress.com/2015/02/22/the-bramdean-circle-of-stones/ erected by "Colonel George Greenwood of Brockwood (formerly Brookwood) House, a large property down the lane on the other side of the crossroads...there are two possible explanations of the Colonel’s motivation for building the it in 1845 or thereabouts: “One…is that he wished to see how long it would be before they were regarded as relics of the ancient past – this is commonly said of them today. The alternative is that they were a demonstration of the power of his tree-lifter”. The tree-lifter was the Colonel’s invention for transplanting trees up to 30 feet in height with their ball of earth intact, a feat the apparatus apparently made possible for a single individual to do at a rate of one tree per day. The somewhat aptly-named Colonel Greenwood was very enthusiastic about the importance of trees to the landscape and wrote a book in 1844 called The Tree-lifter, Or a new method of transplanting forest trees,....Colonel Greenwood is said to have excavated local archaeological sites and was a keen geologist referred to as ‘the father of subaerialism’, ascribing the greater inequalities in the earth’s surface to atmospheric influences. ..It was said in his obituary that “had he fallen amongst geologists in early life, instead of amongst ‘thoroughbreds’, he would doubtless have occupied a leading place among men of science”. ... Incidentally, the colonel is buried nearby at All Saints church, Hinton Ampner, his grave stone a recumbent sarsen which stands out pleasingly amongst all the more traditional ones. "
A few thoughts on the 2024 Sarsen Debitage Paper
Local and exotic sources of sarsen debitage at Stonehenge revealed by geochemical provenancing
Friday 26 January 2024
Local and exotic sources of sarsen debitage at Stonehenge revealed by geochemical provenancing,
Local and exotic sources of sarsen debitage at Stonehenge revealed by geochemical provenancing,
Journal of Archaeological Science: Reports, Volume 53, 2024, 104406, ISSN 2352-409X,
https://doi.org/10.1016/j.jasrep.2024.104406.
(https://www.sciencedirect.com/science/article/pii/S2352409X24000348)
Abstract: The application of novel geochemical provenancing techniques has changed our understanding of the construction of Stonehenge, by identifying West Woods on the Marlborough Downs as the likely source area for the majority of the extant sarsen megaliths at the monument. In this study, we apply the same techniques to saccharoid sarsen fragments from three excavations within and outwith the main Sarsen Circle to expand our understanding of the provenance of sarsen debitage present at the monument. Through pXRF analysis, we demonstrate that the surface geochemistry of 1,028 excavated sarsen fragments is significantly affected by subsurface weathering following burial in a way that cannot be overcome by simple cleaning. However, we show that this effect is surficial and does not have a volumetrically significant impact, thus permitting the subsequent use of whole-rock analytical methods. Comparison of ICP-AES and ICP-MS trace element data from 54 representative sarsen fragments with equivalent data from Stone 58 at Stonehenge demonstrates that none are debitage produced during the dressing of this megalith or its 49 chemical equivalents at the monument. Further inspection of the ICP-MS data reveals that 22 of these fragments fall into three distinct geochemical ‘families’. None of these families overlap with the geochemical signature of Stone 58 and its chemical equivalents, implying that sarsen imported from at least a further three locations (in addition to West Woods) is present at Stonehenge. Comparison of immobile trace element signatures from the 54 excavated sarsen fragments against equivalent data for 20 sarsen outcrop areas across southern Britain shows that 15 of the fragments can be linked to specific localities. Eleven of these were likely sourced from Monkton Down, Totterdown Wood and West Woods on the Marlborough Downs (25–33 km north of Stonehenge). Three fragments likely came from Bramdean, Hampshire (51 km southeast of Stonehenge), and one from Stoney Wish, East Sussex (123 km to the southeast). Technological analysis and refitting shows that one of the fragments sourced from Monkton Down was part of a 25.7 cm × 17.9 cm flake removed from the outer surface of a large sarsen boulder, most probably during on-site dressing. This adds a second likely source area for the sarsen megaliths at Stonehenge in addition to West Woods. At this stage, we can only speculate on why sarsen from such diverse sources is present at Stonehenge. We do not know whether the fragments analysed by ICP-MS were removed from (i) the outer surface of Stones 26 or 160 (which are chemically distinct to the other extant sarsen megaliths), (ii) one of the c.28 sarsen megaliths and lintels from the c.60 erected during Stage 2 of the construction of Stonehenge that may now be missing from the monument, or (iii) one of the dismantled and destroyed sarsen megaliths associated with Stage 1 of the monument. With the exception of the fragment sourced from Monkton Down, it is also possible that the analysed fragments were (iv) pieces of saccharoid sarsen hammerstones or their pre-forms, or (v) small blocks brought on-site for ceremonial or non-ceremonial purposes.
Keywords: Stonehenge; Sarsen; Silcrete; Geochemical provenancing; pXRF; ICP-AES; ICP-MS
Second, we analysed 54 sarsen fragments from the 3 trenches using ICP-MS. This is where it gets interesting. Comparison of the geochemistry of fragments against data for 20 sarsen outcrop areas across southern Britain shows that 15 fragments can be linked to specific areas.
Eleven sarsen fragments were likely sourced from Monkton Down, Totterdown Wood and West Woods on the Marlborough Downs (25–33 km N of Stonehenge). Three fragments likely came from Bramdean, Hampshire (51 km SE of Stonehenge), and one from Stoney Wish, East Sussex (123 km SE).
You might be thinking "Wow, Neolithic people dragged sarsen boulders all the way from Hampshire, East Sussex and other sites on the Marlborough Downs to build Stonehenge, not just from West Woods!" Not quite. Calm down, calm down.
We cannot tell if the fragments are from extant megaliths, or from stones from earlier phases of Stonehenge, or stones that have been removed. It is also possible the fragments were from saccharoidal sarsen hammerstones, or stone brought to Stonehenge for some other reason.
There is one exception - a sarsen fragment sourced from Monkton Down that we know (thanks to expert refitting by Ben Chan) was part of a 25.7 × 17.9 cm flake removed from the outer surface of a large sarsen boulder, most probably during on-site dressing.
We're pretty sure this boulder isn't on site today, unless it is stone 26 or 160, which have a different chemistry to the other extant sarsens. However, it adds a second likely source for the Stonehenge megaliths in addition to West Woods. I'll leave it there. Happy reading!