This is a new paper involving about 16 authors, purporting to be about the "sarsen stones at Stonehenge" but actually about the detailed analysis (using many different techniques) of two core samples from stone 58. It was strictly embargoed until 4th August, but I can't think why, since its findings, although very worthy, are not exactly earth-shattering. Here is the key info and the Abstract.
Nash DJ, Ciborowski TJR, Darvill T, Parker Pearson M, Ullyott JS, Damaschke M, et al. (2021) Petrological and geochemical characterisation of the sarsen stones at Stonehenge. PLoS ONE 16(8): e0254760.
https:// doi.org/10.1371/journal.pone.0254760
ABSTRACT
Little is known of the properties of the sarsen stones (or silcretes) that comprise the main architecture of Stonehenge. The only studies of rock struck from the monument date from the 19th century, while 20th century investigations have focussed on excavated debris with- out demonstrating a link to specific megaliths. Here, we present the first comprehensive analysis of sarsen samples taken directly from a Stonehenge megalith (Stone 58, in the cen- trally placed trilithon horseshoe). We apply state-of-the-art petrographic, mineralogical and geochemical techniques to two cores drilled from the stone during conservation work in 1958. Petrographic analyses demonstrate that Stone 58 is a highly indurated, grain-supported, structureless and texturally mature groundwater silcrete, comprising fine-to-medium grained quartz sand cemented by optically-continuous syntaxial quartz overgrowths. In addition to detrital quartz, trace quantities of silica-rich rock fragments, Fe-oxides/hydroxides and other minerals are present. Cathodoluminescence analyses show that the quartz cement developed as an initial <10 μm thick zone of non-luminescing quartz followed by ~16 separate quartz cement growth zones. Late-stage Fe-oxides/hydroxides and Ti-oxides line and/or infill some pores. Automated mineralogical analyses indicate that the sarsen pre- serves 7.2 to 9.2 area % porosity as a moderately-connected intergranular network. Geo- chemical data show that the sarsen is chemically pure, comprising 99.7 wt. % SiO2. The major and trace element chemistry is highly consistent within the stone, with the only magni- tude variations being observed in Fe content. Non-quartz accessory minerals within the silcrete host sediments impart a trace element signature distinct from standard sedimentary and other crustal materials. 143Nd/144Nd isotope analyses suggest that these host sediments were likely derived from eroded Mesozoic rocks, and that these Mesozoic rocks incorporated much older Mesoproterozoic material. The chemistry of Stone 58 has been identified recently as representative of 50 of the 52 remaining sarsens at Stonehenge. These results are therefore representative of the main stone type used to build what is arguably the most important Late Neolithic monument in Europe.
Here is the Press Release from David Nash:
Press Release 31 July 2021
UNDER EMBARGO: 4 August 2021 - 11AM Pacific / 2PM Eastern / 7PM UK Time
New research provides the first glimpse inside the great sarsen stones at Stonehenge
New research by an international team of geologists, geomorphologists and archaeologists has provided the first glimpse inside one of the giant sarsen stones at Stonehenge. Published in the journal PLoS ONE, the study – led by Professor David Nash (University of Brighton, UK) – has revealed new insights into the geology and chemistry of the stone, showing how it originally formed before being moved into place at the monument during the Neolithic period.
Typically weighing 20 tonnes and standing up to 7 metres tall, sarsens form all fifteen stones of Stonehenge’s central horseshoe, the uprights and lintels of the outer circle, as well as outlying stones such as the Heel Stone, the Slaughter Stone and the Station Stones. Fifty-two of the original c.80 sarsens remain at the monument.
The breakthrough came following a unique opportunity to analyse a 7 cm (3 inch) long sample from a core drilled from Stone 58 at Stonehenge during conservation work in the 1950s. The location of the core remained a mystery until 2018 when the late Robert Phillips, a representative of the company who did the drilling work, returned it to the UK from his home in Florida. Due to its protected status, taking samples directly from stones at Stonehenge would be almost impossible today.
Analyses of wafer-thin slices of the rock under a microscope show that the sarsen stone is made up of mainly sand-sized quartz grains that are cemented tightly together by an interlocking mosaic of quartz crystals. This explains the stone's resistance to weathering and why it made an ideal material for monument-building.
Studies of chemical isotopes within the sarsen stone indicate that the sand grains were originally eroded from pre-existing Mesozoic sedimentary rocks and that these Mesozoic rocks incorporated much older Mesoproterozoic (1- to 1.6-billion-year-old) sediments. Use of a technique called cathodoluminescence imaging shows that the interlocking quartz cements developed through at least 16 cycles of mineral deposition, most likely as a result of wetting and drying while the sediment was buried underground.
Chemical data from the Phillip’s Core were used last year to show that most of the large sarsen stones came from around 15 miles to the north, in West Woods on the edge of the Marlborough Downs, Wiltshire. This new research provides further data that could be used to trace the sources of the remaining stones.
Professor Nash said: “It is extremely rare as a scientist that you get the chance to work on samples of such national and international importance. Thanks to help from organisations such as the British Geological Survey and the Natural History Museum we have been able apply a suite of state-of-the-art techniques to the Phillip’s Core. We have CT-scanned the rock, zapped it with X-rays, looked at it under various microscopes and analysed its sedimentology and chemistry. This small sample is probably the most analysed piece of stone other than Moon rock! The data are all now publicly available to support future research on sarsens at Stonehenge and other nearby Neolithic monuments.”
The research was an interdisciplinary collaboration between the University of Brighton, Bournemouth University, University College London, University of South Wales, Vrije Universiteit Brussel, British Geological Survey, English Heritage, the Natural History Museum (London), Gatan UK and Vidence Inc. (Canada), and was funded by the British Academy and Leverhulme Trust.
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Note this:
"The chemistry of Stone 58 has been identified recently as representative of 50 of the 52 remaining sarsens at Stonehenge. These results are therefore representative of the main stone type used to build what is arguably the most important Late Neolithic monument in Europe."
and this:
"Chemical data from the Phillip’s Core were used last year to show that most of the large sarsen stones came from around 15 miles to the north, in West Woods on the edge of the Marlborough Downs, Wiltshire."
Whether Stone 58 really is "representative" of the other sarsens remains to be seen, since that word can be interpreted in a host of different ways. And did the data in the original paper by Nash et al really "show" that the bulk of the sarsens came from West Woods? Here we are looking at another piece of interpretive inflation -- the word "possibly" has been quietly omitted. Much more will be revealed on the origins of the sarsens in due course, and the truth will not be quite as simple as some would like.
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PS. 7th Aug 2021. This is rather entertaining -- if we look at the press coverage of this PlosOne article, it is clear that nobody can find anything remotely spectacular to say about it. Every article seems to find a different angle, and one or two of them are really rather silly. We should probably thank the authors for doing some serious science, free of hyperbole.......
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