At the end of this piece I have posted the new report on the NERC web site of the latest research by Bevins, Ixer and Pearce on the Carn Goedog rock identifications:
"Carn Goedog is the likely major source of Stonehenge doleritic bluestones: evidence based on compatible element geochemistry and Principal Component Analysis"
Richard E. Bevins, Rob A. Ixer, Nick J.G. Pearce
http://www.sciencedirect.com/science/article/pii/S0305440313003956
ABSTRACT: The
Stonehenge bluestones were first sourced to outcrops in the high parts
of the eastern Mynydd Preseli in SW Wales by H.H. Thomas in the early
1920s. He recognised the distinctive ‘spotted dolerite’ from his
fieldwork in that area and suggested that the tors of Carn Meini (also
known as Carn Menyn) and Cerrigmarchogion were the most likely sources.
In the early 1990s, in a major contribution to our understanding of the
Stonehenge bluestones, the geochemistry of a set of samples from
Stonehenge monoliths and debitage was determined and compared against
the geochemistry of dolerites from the eastern Mynydd Preseli by a team
from the Open University led by R.S. Thorpe. They argued that the
majority of the Stonehenge dolerites could be sourced from outcrops in
the Carn Meini-Carn Gyfrwy area, based on the concentrations of the
so-called ‘immobile’ elements (elements which are not affected by rock
alteration processes), in particular TiO2, Y, and Zr.
However, these elements are incompatible during crystallization of
mineral phases in basaltic systems (that is they do not enter into the
mineral phases which are crystallizing but are concentrated in the
residual liquid) which severely hampers their use in discriminating
between different pulses of an evolving magma (as is the case of the
doleritic sills emplaced high in the crust and now exposed in the Mynydd
Preseli). An alternative strategy in this study re-examines the data
set of Thorpe's team but investigates the concentration of elements
which are compatible in such basaltic systems (that is elements which do
enter into the crystallizing mineral phases), namely MgO, Ni, Cr and Fe2O3.
On the basis of the abundances of these elements on bivariate plots and
also by using Principal Component Analysis on the dataset available and
various sub-sets we identify three compositional groupings for the
Stonehenge doleritic monolith and debitage samples and conclude that the
majority of them (Group 1 of this paper) can be sourced to the
prominent outcrop in the eastern Mynydd Preseli known as Carn Goedog. We
also offer potential sources (with one exception) for those Stonehenge
dolerites which appear not to relate to Carn Goedog.
We have looked at this paper before, so there is no need to analyse it again. What's interesting is the article, published in a journal (web based) devoted to the Earth Sciences. Look at the heading -- totally absurd, since presumably the author is an earth scientist herself. Could she not bring herself to say " New evidence brings bluestone human transport theory into question" or something similar? That shows us just how far the human transport myth has penetrated deep into the souls of people who should know better....... even within the Earth Sciences research community. How sad.
As for the article, it's pretty straightforward, and it's good to see that HH Thomas's science and his motivation are at last being questioned by professional geologists -- as I have done often before on this blog. Just put "HH Thomas" into the search box to uncover some of my past comments.....
Assuming that Richard Bevins is being quoted correctly, he does seem to be getting much more critical and questioning of the archaeological orthodoxy. At last!!
This is the key para:
"If Carn Goedog is the true origin of
the dolerites, and Craig Rhos-y-felin is a source of the rhyolitic
bluestones then it does bring into question the stones being transported
by rafts down to the Bristol Channel, because both of these outcrops
lie on the northern side of the Preseli Hills. The rocks would have had
to be dragged up the hills, across the summits and back down again
before they even reached the waterways. It's just not likely," Bevins
concludes.
Welcome to the club. But if Richard was prepared to go this far, why could he not just have added: "The locations of these possible source areas on the north -- or up-glacier - flank of Preseli is entirely in tune with glacial theory, and increases the likelihood that the stones are glacial erratics picked up by over-riding ice and transported at least part of the way towards Stonehenge."
Now if he had said that, and if it had been reported in this short article, we might have an indication of earth scientists actually taking seriously the comments of their own colleagues, instead of going with the archaeological orthodoxy. And if you think that indicates a degree of frustration on my part, you would be quite right.......
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Did humans transport Stonehenge rocks further than previously thought?
17 February 2014, by Harriet Jarlett
http://planetearth.nerc.ac.uk/news/story.aspx?id=1611&cookieConsent=A
Scientists have pinpointed the exact source of many of the rocks used to build Stonehenge.
A new study, published in the
Journal of Archaeological Science,
suggests that the site researchers had previously thought was the
starting place of many of Stonehenge's rocks may not have been the
source after all. Instead, it looks like the rocks actually come from a
different site three kilometres away.
The findings, bring into
question the long-standing theory that people transported the rocks from
Wales to Wiltshire in order to build the monument.
The research
focused on the smaller stones at Stonehenge, called bluestones. The
chemistry of these rocks varies, but they all originate from the Preseli
Hills in Wales and are thought to have been transported to the
Stonehenge site over 4000 years ago.
By confirming the source of
the rocks, the researchers hope to help answer the long standing
question of how around 80 of these bluestones, weighing up to three
tonnes each, were transported 250 kilometres from southwest Wales to
Wiltshire.
'The Holy Grail question is how were the stones moved
and why,' explains Dr Richard Bevins of National Museum of Wales who led
the research. 'Many people think humans transported the stones south,
down from the Preseli Hills and then up the Bristol Channel on rafts.
But a second school of thought says these rocks are glacial erratics
that were transported by ice to Salisbury Plain and so were available in
the local environment.
'We're trying to discover the source of
the stones so archaeologists can excavate sites in order to see if they
can find evidence for people working the source stones,' he continues.
Scientists
have known the bluestones originated from the Preseli Hills since 1923,
when H. H. Thomas from NERC's British Geological Survey recognised the
distinctive dark grey spotty rocks, known as spotted dolerites, during
fieldwork. Further work in the early 1990s then tried to tie down the
specific locations of the rocks' origin by matching the chemistry of the
Stonehenge bluestones with those at the proposed origin site.
'The
earlier research looked at the source of one of the spotted dolerites
and tied it down to a specific outcrop, Carn Meini. It seems Thomas
wanted all of the bluestones to also come from that same small area so
he argued the rhyolites came from a nearby outcrop, Carn Alw. When we
looked at it again we realised the descriptions of the rhyolites from
Carn Alw and those at Stonehenge didn't look the same at all,' says
Bevins.
The team took images showing the rocks at Stonehenge and
the rocks at Carn Alw. They then asked members of the public with no
geological background whether they looked the same.
'We asked
people "does A look like B?" and everyone said no,' Bevins continues.
'This is astonishing because this has not been questioned since the
original publication by Thomas in 1923.'
The team used a new
method of identifying the chemical makeup of the rocks, to match the
rocks with their origin. They believe that they have now identified Carn
Goedog as the source of at least 55 per cent of the spotted dolerite
bluestones at Stonehenge.
'If Carn Goedog is the true origin of
the dolerites, and Craig Rhos-y-felin is a source of the rhyolitic
bluestones then it does bring into question the stones being transported
by rafts down to the Bristol Channel, because both of these outcrops
lie on the northern side of the Preseli Hills. The rocks would have had
to be dragged up the hills, across the summits and back down again
before they even reached the waterways. It's just not likely,' Bevins
concludes.
